Eye Conditions

This page provides basic information about numerous eye conditions including a description, associated vision loss, accommodations and implications for learning.

Description: Achromatopsia is a rare, hereditary, congenital inability to distinguish colours (Cassin & Rubin, 2012, p. 23) due the absence of cone photoreceptors within the retina (Schwartz, 2010). Nystagmus is usually present. Achromatopsia is usually stable, although rarely deterioration of vision may occur (Schwartz, 2010).

Effects on Vision: Individuals with achromatopsia have a complete inability to see colour as well as extreme photophobia (light sensitivity) and reduced visual acuity (Schwartz, 2010).

Educational Implications: Students with achromatopsia will be unable to use resources that rely on colour alone to convey concepts. Teachers will need to work with a teacher of students with visual impairments to adapt materials in ways that do not rely on colour and are of sufficient print size and contrast. Students may need to be positioned in areas without exposure to bright light or glare (such as windows or whiteboards) and other measures to control classroom lighting may be helpful.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed. pp. 137-191). New York, NY: AFB Press.

Description: Aicardi syndrome is an inherited disorder that affects the central nervous system and brain and can include retinal malformation (Cassin & Rubin, 2012, p. 26). Aicardi syndrome may be accompanied by other eye conditions including microphthalmia and optic nerve coloboma (Genetics Home Reference, “Aicardi Syndrome”).

Effects on Vision: The severity of Aicardi syndrome varies (Genetics Home Reference, “Aicardi Syndrome”). Vision may range from low vision to blindness.

Educational Implications: The educational needs of students with Aicardi syndrome will vary widely. Students may need low vision devices or audio and tactile materials.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetics Home Reference. (July 10, 2018). Aicardi syndrome. Retrieved from https:/ghr.nlm.nih.gov/condition/aicardi-syndrome#statistics.

Description: Albinism is an inherited disorder where melanin (pigment) is decreased or absent. Albinism can affect the skin, hair, and eyes (Schwartz, 2010). Albinism may affect only the eyes (ocular) or may affect the eyes, skin, and hair (oculocutaneous). There are several subtypes of oculocutaneous albinism that vary in severity. Melanin is needed for development of the fovea within the eye, so a lack of melanin causes underdevelopment of the fovea and optic nerve (Schwartz, 2010).

Effects on Vision: Albinism varies widely in its severity, but individuals with albinism have reduced visual acuity, reduced or no depth perception, and sensitivity to light and glare (Schwartz, 2010) as well as nystagmus (Cassin & Rubin, 2012, p. 27).

Educational Implications: Students with albinism may benefit from the use of low vision aids and control of environmental light and glare. Specific seating away from sources of light and glare (such as windows or whiteboards) and other measures to control classroom lighting may be helpful. Depending on a student’s visual acuity, a learning media assessment and/or orientation and mobility assessment may be recommended.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Alstrom Syndrome is a rare genetic disorder that can result in infant cardiomyopathy and later deafness, obesity, and diabetes (Pediatric Ophthalmology Education Center, August 26, 2016). Individuals with Alstrom syndrome may have photophobia, nystagmus, and a form of cone-rod dystrophy  that is progressive (Pediatric Ophthalmology Education Center, August 26, 2016).

Effects on Vision: Degeneration of the retinal cones result in loss of visual acuity and colour vision (Cassin & Rubin, 2012, p. 71) and degeneration of the retinal rods leads to loss of night vision, tunnel vision, and blindness (Casin & Rubin, 2012, p. 245). Individuals with Alstrom syndrome also experience light sensitivity (photophobia) and hyperopia is common (Pediatric Ophthalmology Education Center, August 26, 2016).

Educational Implications: A student’s vision can vary from low vision to total blindness. Students may benefit from low vision aids or nonvisual methods such as use of braille or tactile educational resources. Students would also benefit from being seated away from bright light and glare (such as windows or whiteboards).

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Pediatric Ophthalmology Education Center. (August 26, 2016). Alström syndrome. Retrieved from https://www.aao.org/disease-review/alstr%C3%B6m-syndrome.

Description: Amblyopia is a condition where there is poor visual acuity in one or both eyes due to poor visual input to the brain, resulting in the visual part of the brain failing to develop properly (Schwartz, 2010). Causes of amblyopia include large differences in refractive errors in each eye, secondary to conditions that block vision such as corneal cloudiness or cataracts, uncorrected refractive errors, strabismus, or consumption of toxic substances. Treatment may include correcting refractive errors (Cassin & Rubin, 2012, p. 29) and blurring of vision in the better eye with patching or eye drops (Schwartz, 2010).

Effects on Vision: Amblyopia results in poor visual acuity in one or both eyes (Cassin & Rubin, 2012, p. 29). Amblyopia can also cause monocular vision (vision in only one eye) and poor depth perception (Schwartz, 2010).

Educational Implications: Students with amblyopia may need to use patching or eye drops that blur vision in their better eye during the school day. This may cause them to be functionally visually impaired while undergoing the patching program.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Aniridia is a congenital condition in which the iris is underdeveloped or absence and the retina and optic nerve are underdeveloped. Individuals with aniridia commonly also develop nystagmus, cataracts, and glaucoma (Schwartz, 2010).

Effects on Vision: Aniridia results in decreased visual acuity and photophobia (sensitivity to light and glare).

Educational Implications: Students with aniridia may benefit from low vision aids, assistive technology, and classroom seating away from sources of bright light and glare, as well as possibly other measures to control classroom lighting. Students should be assessed regularly as their vision could change over time.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Anophthalmia is the absence of one or both eyes (National Eye Institute, August, 2009). Anophthalmia may occur because of genetic mutations and chromosomal abnormalities.

Effects on Vision: Individuals with anophthalmia have no usable vision.

Educational Implications: Students with anophthalmia will be nonvisual learners and will need to work closely with a teacher of students with visual impairments and orientation and mobility specialist to learn skills such as braille, assistive technology, and travel skills.

References:

National Eye Institute. (August, 2009). Facts about anophthalmia and microphthalmia. Retrieved from https://nei.nih.gov/health/anoph/anophthalmia.

Description: Apert’s syndrome is a congenital syndrome that may result in heart and kidney abnormalities, developmental delays, and abnormalities of the face, fingers, and toes (Cassin & Rubin, 2012, p. 36). Ocular conditions that can occur with this syndrome include eye socket abnormalities, exposed corneas, exotropia, and optic nerve damage (Cassin & Rubin, 2012, p. 36).

Effects on Vision: Individuals with Apert’s syndrome may have visual field defects (Cassin & Rubin, 2012, p. 36).

Educational Implications: Students with Apert’s syndrome will have complex educational needs requiring an interdisciplinary team that includes a teacher of students with visual impairments. Visual needs may include positioning the student so that they can use their best area of visual field and ensuring that materials are high-contrast and glare-free.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: Aphakia is the absence of the lens of the eye, most often associated with the surgical removal of a cataract (Cassin & Rubin, 2012, p. 36). Aphakia may also occur from a complete dislocation of the lens (Schwartz, 2010). The optical power of the lens can be replaced with plus-powered glasses (Cassin & Rubin, 2012, p. 36).

Effects on Vision: Students with aphakia have very poor vision without glasses, but can be corrected with plus-powered glasses (Cassin & Rubin, 2012, p. 36).

Educational Implications: Individuals with aphakia should be encouraged to wear their glasses and contact lenses at all times. They may benefit from enlarged materials and low vision devices.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Bardet-Biel Syndrome is a genetically inherited disorder that can affect vision as well as many other body systems (Genetics Home Reference, July 10, 2018). The genes affected lead to problems with the structure and function of cilia, which are microscopic projections on the surface of many cells and affect cell movement and chemical signaling pathways. In this condition, the retina photoreceptors degenerate and often lead to legal blindness by adolescence (Genetics Home Reference, July 10, 2018).

Effects on Vision: Children with Bardet-Biedl Syndrome first have problems with night vision, followed by blind spots in and gradual narrowing of peripheral vision. Most children with Bardet-Biedl Syndrome also have decreased central visual acuity (Genetics Home Reference, July 10, 2018).

Educational Implications: Students with Bardet-Biedl syndrome may benefit from controlled lighting (not too dim), enlarged materials and low vision devices, and alternate formats such as braille, depending on their functional vision. They may also benefit from assessment and instruction from a teacher of students with visual impairments and/or orientation and mobility specialist.

References:

Genetics Home Reference. (July 10, 2018). Bardet-biedl syndrome. Retrieved from https://ghr.nlm.nih.gov/condition/bardet-biedl-syndrome.

Description: Batten disease is a group of rare, genetic nervous system disorder involving a defect in body cells’ ability to recycle certain molecules (National Institute of Neurological Diseases and Stroke, July 6, 2018). Age of onset and specific symptoms vary depending on the specific gene affected. Common symptoms include vision loss, seizures, regression of previously acquired skills, and movement difficulties. Batten disease is progressive with symptoms worsening over time and a shortened life expectancy (National Institute of Neurological Diseases and Stroke, July 6, 2018). Batten disease causes retinal lesions in the macula and optic nerve degeneration (Cassin & Rubin, 2012, p. 45).

Effects on Vision: Macula damage causes decreased visual acuity and optic nerve degeneration causes visual field defects.

Educational Implications: Batten disease has a wide range of effects on vision, motor skills, learning, as well as medical considerations including seizures. As such, a transdisciplinary approach to education will be needed. Students with Batten disease may benefit from low vision aids as well as functional vision, learning media, and orientation and mobility assessments from a teacher of students with visual impairments and orientation and mobility specialist.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

National Institute of Neurological Disorders and Stroke. (July 6, 2018). Batten disease fact sheet. Retrieved from https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Batten-Disease-Fact-Sheet.

Description: Cat Eye syndrome is a non-inherited chromosomal abnormality that affects many areas of the body (Genetic and Rare Diseases Information Center, April 13, 2015). Individuals with this syndrome have duplicate genetic material from chromosome 22 attached to each cell in their body, which leads to the varying signs and symptoms of the syndrome. Cat Eye syndrome can affect the eyes in several ways, including iris coloboma and strabismus (Genetic and Rare Diseases Information Center, April 13, 2015). This syndrome may also lead to macular underdevelopment and optic nerve degeneration (Cassin & Rubin, 2012, p. 60).

Effects on Vision: Students may have reduced visual acuity, visual field defects, or a combination of both. The extent of these effects will vary widely from student to student.

Educational Implications: Students with reduced visual acuity may have difficulty seeing small objects and seeing objects at a distance. Students with a reduced visual field may have difficulty seeing objects that are to the sides or in one particular location (e.g., upper visual field). A teacher of students with visual impairments will be able to provide assessment and communicate the student’s functional vision and needed accommodations to the educational team. Educational teams will also need to take other medical or developmental aspects of Cat Eye syndrome into considering when designing an educational program.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetic and Rare Diseases Information Center. (2015, April 13). Cat eye syndrome. Retrieved from https://rarediseases.info.nih.gov/diseases/26/cat-eye-syndrome.

Description: Cataracts refer to an opacity or cloudiness of the lens, which may prevent a clear image from forming on the retina (Cassin & Rubin, Cataract, 2012). Congenital cataracts (from birth) or infantile cataracts (developed during the first two years of life) are caused by genetics, inherited metabolic disorders, intrauterine infections (such as rubella), trauma, or associated with other eye conditions such as aniridia and microphthalmos (Schwarts, 2010). Types of cataracts include nuclear, cortical, and posterior subcapsular cataracts (Cassin & Rubin, 2012, p. 58-59). If cataracts are removed surgically, the individual will be aphakic. Other eye conditions that may be present with cataracts include strabismus, amblyopia, nystagmus, and glaucoma (Schwarts, 2010).

Effects on Vision: Cataracts primarily cause a reduction in visual acuity, which varies by type and location of the cataracts. Contrast sensitivity, and problems with glare may also be present (Schwarts, 2010).

Educational Implications: Students with decreased visual acuity may have difficulty seeing small objects and objects at a distance. If a student has difficulty with contrast sensitivity, materials must have very good contrast. Students may need specific seating to accommodate difficulties with glare (e.g., off whiteboards, projectors, and other surfaces or through windows).

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Cortical visual impairment is a condition where the optical cortices within the brain are damage but the retina appears normal (Cassin & Rubin, 2012, p. 78-79). The most common causes of CVI include inadequate blood or oxygen supply to an infant’s brain near the time of birth. A majority of children with CVI have additional neurological problems such as seizures or cerebral palsy (Schwartz, 2010).

Effects on Vision: Children with CVI have difficulty interpreting the visual information in their environment (Schwartz, 2010). Visual function varies widely between individuals and may seem to vary daily within the same individual. There are certain characteristics that are common among children with cortical visual impairment, such as preferring certain colours, attraction or aversion to lights, aversion to new objects, and a tendency to look at and reach for objects as separate actions. Although visual acuity cannot be used to predict vision, visual field defects are common. In many cases vision may improve somewhat over time, though most children with CVI remain visually impaired (Schwartz, 2010).

Educational Implications: As the visual functioning of students with CVI can vary so widely, it is important for these students to work with a teacher of students with visual impairments so that appropriate assessments, environmental adaptations, and appropriate learning resources are provided.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: CHARGE syndrome is a congenital, genetic condition that results in a number of effects on the body, including abnormalities in the eyes, heart, nasal passages, growth and development, genitals, and ears. CHARGE syndrome may be inherited or due to a spontaneous genetic mutation (Genetic and Rare Diseases Information Center, February 16, 2017). A major characteristic of CHARGE syndrome is coloboma of one or both eyes, and affected individuals may also have microphthalmos (Genetics Home Reference, July 10, 2018, “CHARGE syndrome”).

Effects on Vision: The visual effects of coloboma vary depending on which structure of the eye is affected (Schwartz, 2010).

Educational Implications: Students with a coloboma may have a visual field loss and low visual acuity. Depending on visual needs, they may benefit from enlarged materials, high-contrast materials, preferential seating, control of light and glare, and functional vision, learning media, and orientation and mobility assessments. It is likely that the student will have a dual sensory loss and require services for students with deafblindness.

References:

Genetics Home Reference. (July 10, 2018). CHARGE syndrome. Retrieved from https://ghr.nlm.nih.gov/condition/charge-syndrome.

Genetic and Rare Diseases Information Center. (2017, February 17). CHARGE syndrome. Retrieved from https://rarediseases.info.nih.gov/diseases/29/charge-syndrome.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Coats' disease is a chronic, progressive disorder involving white exudates into the retina and torturous blood vessel development (Cassin & Rubin, 2012, p. 69). It is more common in males and typically only affects one eye. Coats’ disease may eventually lead to retinal detachment, glaucoma (Cassin & Rubin, 2012, p. 69), strabismus, and cataracts (Genetic and Rare Diseases Information Center, 2017, August 17).

Effects on Vision: The effects Coats' disease has on vision varies. In its early stages, there may only be minor loss of vision, but vision loss can be substantial in its later stages (Genetic and Rare Diseases Information Center, 2017, August 17).

Educational Implications: The associated retinal detachment can result in visual field loss, where parts of the visual field are missing. Preferential seating in the classroom should be considered. Since it is unilateral there can be loss of depth perception. Physical and spatial activities should be assessed for potential dangers. Deterioration usually begins in the upper part of the vision field so reading environments (near and far) should be assessed for access and efficiency.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetic and Rare Diseases Information Center. (2017, August 17). Coats’ disease. Retrieved from https://rarediseases.info.nih.gov/diseases/6121/coats-disease.

Description: A coloboma is a congenital abnormality caused by the interruption of the eye’s normal development during gestation, leaving a cleft. Colobomas can affect the optic nerve, retina, iris, lens, or eyelid (Cassin & Rubin, 2012, p. 70). Colobomas are usually stable, but may be associated with nystagmus, retinal detachment, and cataracts (Schwarts, 2010) as well as microphthalmia (Cassin & Rubin, 2012, p. 70).

Effects on Vision: The effects of a coloboma depend on the part of the eye affected and the extent of the coloboma (Schwarts, 2010). An iris coloboma will not affect visual acuity but may cause photophobia and astigmatism. A coloboma affecting the back of the eye visual acuity and visual field will be reduced (Schwarts, 2010).

Educational Implications: The degree and severity of a student’s visual impairment will vary. Students who have photophobia will benefit from seating and presentations that avoid excess light and glare. Aids such as magnification and a Learning Media Assessment may assist students with reduced visual acuity.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Cone dystrophies are hereditary, progressive degeneration of the retinal photoreceptors involving primarily the cones. There is no known treatment (Cassin & Rubin, 2012, p. 71).

Effects on Vision: Individuals with cone dystrophy may have decreased colour vision and visual acuity (Cassin & Rubin, 2012, p. 71) and may also be sensitive to light (Ward, 2010).

Educational Implications: Since cone dystrophy is a degenerative condition, it is important that students are monitored regularly to ensure that any changes in vision can be accommodated. Students may benefit from seating away from light and glare, large print or digital texts, and low vision devices.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Ward, M. E. (2010). Chapter 5: Anatomy and Physiology of the Eye. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed. ed., pp. 111-136). New York, NY: AFB Press.

Description: Corneal dystrophy refers to several inherited diseases that result in corneal clouding due to swelling, scarring, or deposits of foreign material in the cornea (Schwartz, 2010). Corneal dystrophy may be present from birth or develop later, such as during young adulthood. Treatment may include laser or surgery, but the condition tends to recur. If corneal dystrophy occurs in infancy, related eye conditions may include nystagmus and amblyopia (Schwartz, 2010)

Effects on Vision: Corneal dystrophy may result in reduced visual acuity, impaired contrast sensitivity, and sensitivity to light and glare (Schwartz, 2010).

Educational Implications: Students with corneal dystrophy would benefit from high-contrast, low-glare material, material that is enlarged, and low vision devices. Students may also benefit from control of light and glare in the classroom (e.g., from overheads, whiteboards, and windows).

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Ehlers-Danlos syndrome is a congenital connective tissue disorder that affects many areas of the body (Cassin & Rubin, 2012, p. 98-99). The syndrome can affect the eyelids and sclera and cause problems including lens dislocation, glaucoma, and retinal hemorrhages (Cassin & Rubin, 2012, p. 98-99). Lens dislocation may result in a large astigmatism or aphakia (Schwartz, 2010).

Effects on Vision: Effects on vision will vary depending on how Ehlers-Danlos syndrome affects a student’s eyes. Students with lens problems may have a large refractive error (Schwartz, 2010) and may have blurred. If glaucoma develops, they may experience blind spots, peripheral field loss, loss of contrast sensitivity, or visual acuity loss (Schwarts, 2010).

Educational Implications: Students may have to wear glasses to correct a refractive error or complete lack of refractive power if they have a dislocated lens (Schwartz, 2010). Students who develop glaucoma secondary to the syndrome may have difficulties with light and glare as well as areas of field loss. Control of lighting is important, such as use of sun filters, avoiding fluorescent lighting, and reducing environmental glare can be helpful. Discriminating between colours and reading low-contrast text may be difficult. Additionally, students may experience problems with mobility and night vision.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Familial exudative vitreoretinopathy (FEVR) is a genetic, inherited disorder that causes new blood vessels to grow on the retina, resulting in folding, scarring, and detachment (Schwartz, 2010). This condition may degenerate during childhood, but further degeneration in adulthood is rare. Associated eye conditions include nystagmus, retinal detachment, cataracts, and glaucoma (Schwartz, 2010).

Effects on Vision: The severity of FEVR varies greatly. Vision can range from normal to total blindness. Students with FEVR may have reduced visual acuity, blind spots, and reduced visual fields (Schwartz, 2010).

Educational Implications: It is important for students with FEVR to get regular assessment from a teacher of students with visual impairments and orientation and mobility specialist. Students may benefit from high-contrast and enlarged materials, low vision devices, or use of braille and other non-visual tools, depending on their level of vision.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Glaucoma refers to a group of conditions resulting in damage to the optic nerve almost always associated with elevated pressure within the eye, called intraocular pressure. Glaucoma may be acute or chronic and may occur as a congenital condition in infants (Schwartz, 2010). Children who have glaucoma are often treated with surgery and pressure-lowering drops throughout life (Schwartz, 2010).

Effects on Vision: Glaucoma in children can cause clouding of the cornea, extreme light sensitivity, larger-than-normal eyes, myopia, and severe vision loss or blindness (Schwartz, 2010).

Educational Implications: Students with glaucoma may have low vision or be totally blind, therefore their education programming will differ. Students with low vision may benefit from seating close to the teacher and demonstrations, large print materials, low vision devices, and reduced glare. Students who have low vision or are totally blind may benefit from alternate format materials such as braille and tactile exposure to learning resources. As vision may change over time, regular assessment and instruction by a teacher of students with visual impairments and/or orientation and mobility specialist are important.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: This is a rare disorder affecting the scalp, brain, face, sinuses, and eyes (Genetic and Rare Diseases Information Center, 2017, April 21). Individuals with this condition may have corneal opacities, as well as brain abnormalities, numbness of the face, and loss of hair from the scalp. Children may have developmental delays, intellectual disability, seizures, and other symptoms (Genetic and Rare Diseases Information Center, 2017, April 21).

Effects on Vision: Corneal opacities lead to reduced visual acuity, sensitivity to light and glare, and reduced contrast sensitivity (Schwartz, 2010).

Educational Implications: Children with Gomez Lopez Hernandez syndrome may benefit from a transdisciplinary team approach to address their varied educational needs. Students may benefit from use of large, high-contrast materials, control of light and glare, and use of low vision aids.

References:

Genetic and Rare Diseases Information Center. (2017, April 21). Gomez Lopez Hernandez syndrome. Retrieved from https://rarediseases.info.nih.gov/diseases/229/gomez-lopez-hernandez-syndrome.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Hemianopia is a visual field defect that affects the visual field within each eye due to damage to the visual pathway (Schwarts, 2010). Causes of hemianopia may include optic nerve or vascular lesions, strokes, tumors, or trauma (Cassin & Rubin, 2012, p. 132).

Effects on Vision: The degree of vision loss depends on the type, size, and amount of optic pathway damage (Schwartz, 2010). Hemianopia may affect the upper, lower, left, right, inner, or outer visual fields of both eyes (Cassin & Rubin, 2012, p. 132). Vision loss in the affected area may be complete or partial, where vision is reduced but not completely missing. The vision loss may affect the same side of each visual field, opposite sides of each visual field, half fields or quadrants, and may or may not involve the macula (Schwartz, 2010).

Educational Implications: Individuals with hemianopia may benefit from optical devices such as prisms to shift visual information into an area of usable field (Schwartz, 2010). It is recommended that the student work with a teacher of the visually impaired to provide adaptations in the classroom and in Physical Education. It is important to consider preferential seating to allow the student maximum viewing of the classroom. An Orientation and Mobility specialist may help the student navigate unfamiliar environments safely.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Leber congenital amaurosis is an inherited form of retinitis pigmentosa that affects a child from birth (Schwartz, 2010). Children with Leber congenital amaurosis have reduced visual acuity within the first six months of life. Nystagmus is also usually present (Schwartz, 2010).

Effects on Vision: Vision: Children with Leber congenital amaurosis have vision ranging from legal blindness to total blindness (Schwartz, 2010).

Educational Implications: Students with Leber’s congenital amaurosis may benefit either from low vision devices and enlarged material or alternate formats such as braille, depending on their functional vision. They may also benefit from assessment and instruction from a teacher of students with visual impairments and/or orientation and mobility specialist.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Norrie’s syndrome is a hereditary condition that results in bilateral retinal detachment as well as deafness and developmental delays (Cassin & Rubin, 2012, p. 194).

Effects on Vision: Norrie’s syndrome results in blindness (Cassin & Rubin, 2012, p. 194).

Educational Implications: Students who are blind need assessment and instruction from a teacher of students with visual impairments and orientation and mobility specialist. They benefit from tactile exposure and experiences and braille as a reading medium.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: Nystagmus is an involuntary, side-to-side motion of the eyes. Nystagmus may be congenital, secondary to other eye conditions (e.g., albinism), or acquired (Cassin & Rubin, 2012, p. 195-196). Acquired nystagmus may be secondary to trauma, brain tumours, or degenerative conditions (Schwartz, 2010).

Effects on Vision: Nystagmus itself can cause blurred vision, and it is also frequently associated with poor vision caused by other eye conditions (Schwartz, 2010). Individuals with acquired nystagmus may also experience the world as moving (Schwartz, 2010).

Educational Implications: Students with nystagmus may benefit from enlarged materials and low vision devices. As many children have nystagmus secondary another primary conditions that causes severe vision loss, accommodations for students with nystagmus will vary greatly depending on their level of functional vision.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Optic atrophy refers to any degeneration of the optic nerve. Causes may include trauma, infection, premature birth, hydrocephalus, tumors, and other conditions (Schwartz, 2010).

Effects on Vision: Effects on vision may vary and include reduced visual acuity, loss of colour vision, reduced contrast sensitivity, blind spots, reduced visual field (Schwartz, 2010).

Educational Implications: Students with optic atrophy may benefit from use of large print, high-contrast materials, reduced reliance on colours to convey information (e.g., in charts and graphs), control of lighting and glare, and preferential seating in the classroom.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Optic nerve hypoplasia is a congenital condition in which the optic nerves are too small. The cause is unknown. Associated conditions include nystagmus and septo-optic dysplasia (Schwartz, 2010).

Effects on Vision: Optic nerve hypoplasia results in reduced visual acuity and visual field abnormalities. Visual acuity varies widely (Schwartz, 2010).

Educational Implications: Students with optic nerve hypoplasia may have varying visual needs in the classroom. They may benefit from large print materials, alternate formats, and use of assistive technology. They should work with a teacher of students with visual impairments and orientation and mobility specialist to assess needs and provide ongoing assessment and instruction.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Peter’s Anomaly occurs when there is a malformation of the cornea resulting in abnormal adherence to other eye structures (Cassin & Rubin, 2012, p. 216). In addition the cornea is cloudy, and associated eye conditions include cataracts, glaucoma, and amblyopia (Genetics Home Reference, “peters anomaly”).

Effects on Vision: Many individuals with Peter’s anomaly have low vision (Genetics Home Reference, “peters anomaly”).

Educational Implications: Students with Peter’s anomaly may benefit from enlarged materials, low vision devices, seating close to the teacher and demonstrations, and assessment and instruction from a teacher of students with visual impairments.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetics Home Reference (August 28, 2018). Peters anomaly. Retrieved from https://ghr.nlm.nih.gov/condition/peters-anomaly.

Description: A refractive error is a condition in which light rays are not brought into focus properly on the retina (Cassin & Rubin, p. 237, 2012). Three types of refractive errors are astigmatism, hyperopia, and myopia. Astigmatism occurs when the cornea or lens has a “spoon” or cylindrical shape rather than its usual spherical shape (Cassin & Rubin, 2012, p. 39-40). This irregular shape of the cornea or lens causes light to focus at different points in front of and behind the retina. Some types of astigmatism may be caused by corneal scarring, trauma, inflammation, or developmental anomalies (Cassin & Rubin, 2012, p. 39-40). Hyperopia, or far-sightedness, occurs when the eye is too short for its focusing power, resulting in distant images not being focused by the time they reach the retina (Cassin & Rubin, 2012, p. 140). Myopia, or nearsightedness, occurs when light rays are brought into focus before they reach the retina (Cassin & Rubin, 2012, p. 188). Refractive errors may occur in conjunction with other eye conditions.

Effects on Vision: Individuals with astigmatism may be left with residual astigmatism (Cassin & Rubin, 2012, p. 39-40) and those with myopia may occasionally have a progressive type of myopia that may result in thinning and tearing of the retina (Cassin & Rubin, 2012, p. 188).

Educational Implications: Refractive errors are common and usually vision can be corrected to normal or near-normal levels. Students who have progressive myopia that has resulted in retinal complications may benefit from accommodations and working with a teacher of students with visual impairments.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: A retinal detachment occurs when the retina separates from the underlying tissue. Retinal detachments often require immediate treatment (Cassin & Rubin, 2012, p. 239-240) and are often complications of other eye conditions.

Effects on Vision: A retinal detachment can cause reduced visual acuity or visual field defects, depending on its location.

Educational Implications: Students may benefit from use of low vision devices or enlarged material. If students have large visual field defects, they may benefit from seating or positioning objects in the portion of the field they can best use. If a student is blind, they would benefit from assessment and instruction by a teacher of students with visual impairments and orientation and mobility instructor.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: Retinitis pigmentosa is a hereditary condition resulting in progressive vision loss in both eyes (Cassin & Rubin, 2012, p. 241).

Effects on Vision: Symptoms of retinitis pigmentosa often begin in childhood, and the condition results in decreased peripheral vision, night blindness, and eventual total blindness (Cassin & Rubin, 2012, p. 241).

Educational Implications: Students with retinitis pigmentosa will have differing visual needs depending on the degree of their vision loss. Students may benefit from avoidance of dim or dark lighting, large print or tactile materials, and ongoing assessment and instruction from a teacher of students with visual impairments and orientation and mobility specialist.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: Retinoblastoma is an inherited, malignant tumour within the eye. If untreated, retinoblastoma is fatal (Cassin & Rubin, 2012, p. 241); however, retinoblastoma is treatable with chemotherapy, radiation, laser treatment, and surgery (Schwarts, 2010).

Effects on Vision: Vision depends on the size and location of tumours as well as the treatment. Tumours near the macula and optic nerve may result in decreased visual acuity (Schwartz, 2010). If an eye needs to be enucleated (surgically removed), a student may have no vision.

Educational Implications: Students with reduced visual acuity may benefit from seating close to the front of the classroom and teacher demonstrations, large print materials, low vision devices, and high-contrast materials. If a student has no vision, they may benefit from non-visual strategies.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Retinopathy of prematurity is abnormal blood vessel growth that occurs in premature infants and that can lead to scarring and retinal detachment (Schwartz, 2010). Factors that may influence the development of ROP include low birth weight, use of too much or too little oxygen exposure, blood transfusions, and genetic predisposition. Retinopathy of prematurity may regress spontaneously (Cassin & Rubin, 2012, p. 242) or may be treated with cryotherapy or laser treatment (Schwartz, 2010). Conditions that may occur alongside ROP include strabismus, nystagmus, glaucoma, myopia, optic atrophy, and cortical visual impairment (Schwartz, 2010) as well as cataracts (Cassin & Rubin, 2012, p 242).

Effects on Vision: Retinopathy of prematurity can result in loss of both visual acuity and visual field (Schwartz, 2010). Effects on vision may vary widely based on the severity of the ROP as well as presence of associated eye conditions.

Educational Implications: Students with visual impairment from ROP usually benefit from instruction by a teacher of students with visual impairments and orientation and mobility specialist. They may benefit from low vision aids or nonvisual techniques such as braille, depending on the extent of vision loss.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Retinoschisis is a splitting of the sensory layers of the retina (Cassin & Rubin, 2012, p. 243). In children, this may be due to a hereditary, congenital condition where the macular area of the retina is split into inner and outer layers (Cassin & Rubin, 2012, p. 243).

Effects on Vision: Children with retinoschisis may have reduced visual acuity, especially of the central vision (Genetics Home Reference, 2018, August 28).

Educational Implications: Students with decreased visual acuity may benefit from enlarged materials, low vision aids, and seating close to the teacher and presentations.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetics Home Reference. (August 28, 2018). X-linked juvenile retinoschisis. Retrieved from https://ghr.nlm.nih.gov/condition/x-linked-juvenile-retinoschisis.

Description: Rubella syndrome results from German measles contracted during the first trimester of pregnancy. It results in developmental delays and heart, hearing, and eye defects, which include cataracts, glaucoma, retinal changes, and eye deviations (Cassin & Rubin, 2012, p. 246).

Impact on Vision: Cataracts may result in a reduction in visual acuity while glaucoma may affect visual acuity and field. Retinal changes may also affect both visual acuity and field.

Educational Implications: Students with Rubella syndrome may require vision, hearing, deafblindness, and other educational services. Students may benefit from low vision aids, enlarged material, preferential seating, and instruction from a teacher of students with visual impairments, orientation and mobility instructor, and other professionals depending on their unique educational needs.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Description: Septo-optic dysplasia is a congenital disorder where an individual has optic nerve hypoplasia, nystagmus, and absence of the septum pellucidum within the brain (Cassin & Rubin, 2012, p. 254). Individuals with septo-optic dysplasia also have growth hormone deficiency and other hormonal deficiencies (Genetics Home Reference, 2018, August 28).

Effects on Vision: Optic nerve hypoplasia results in reduced visual acuity and visual field abnormalities. Visual acuity varies widely (Schwartz, 2010).

Educational Implications: Students with optic nerve hypoplasia may have varying visual needs in the classroom. They may benefit from large print materials, alternate formats, and use of assistive technology.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Genetics Home Reference. (August 28, 2018). Septo-optic dysplasia. Retrieved from https://ghr.nlm.nih.gov/condition/septo-optic-dysplasia.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Stargardt disease a genetic condition and is the most common form of macular dystrophy of late childhood. Stargardt disease may be difficult to diagnose in its early stages but becomes progressively worse over time (Schwartz, 2010).

Effects on Vision: Visual effects include decreased visual acuity, blind spots (scatomas) in the central visual field, difficulties with colour vision, and mild difficulties adapting to changes in lighting (Schwartz, 2010).

Educational Implications: Central vision is the vision that allows for reading and perception of other fine visual details. Therefore, students with macular damage may benefit from the use of low vision aids. As the condition is progressive, students should work closely with a teacher of students with visual impairments and orientation and mobility specialist so that changing visual needs can be addressed.

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Strabismus is a condition in which the eyes are not properly aligned with each other and, as a result, do not move together normally. Strabismus is caused by an imbalance in the muscles that control eye movement (Cassin & Rubin, 2012, p. 261). Strabismus may be congenital (occur within the first six months or life) or may be acquired (Schwartz, 2010). Strabismus may be hereditary or secondary to trauma, systemic diseases, paralysis, or other eye conditions. Eye misalignment may be intermittent or permanent, and individuals may sometimes be able to control their eye alignment, or it may be involuntary. The misaligned eye may be deviated inwards (esotropia), outwards (exotropia), upwards (hypertropia), or downwards (hypotropia). When strabismus occurs in children, the image from the misaligned eye may be suppressed, resulting in amblyopia. Treatment of strabismus may include glasses, surgery, medication, or occluding the better eye if amblyopia has developed (Schwartz, 2010).

Effects on Vision: Strabismus can result in double vision or decreased visual acuity in one eye (amblyopia). Decreased visual acuity results more frequently in children, while double vision is more frequent in older children and adults (Schwartz, 2010).

Educational Implications: If student is patched, preferential seating is recommended to maximize visual access to the classroom. Depth perception will also be reduced which may affect physical activity. Strabismus should be reported for treatment as soon as it is noticed.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Toxoplasmosis is caused by an infection from the toxoplasma gondii protozoa (Cassin & Rubin, 2012, p. 278-279). Toxoplasmosis can affect many areas of the body, including the lungs, liver, and brain. Toxoplasmosis is also one of the most common causes of retinal scarring in developed countries. Toxoplasmosis may have periods of inactivity with no symptoms and periods of parasite activity that result in visual and other symptoms (Schwartz, 2010).

Effects on Vision: Toxoplasmosis effects on vision include floaters, blurred vision, light sensitivity, and distortions. Scarring resulting from parasite activity can cause loss of visual acuity and localized scotomas, especially if scarring occurs near the optic nerve and macula (Schwartz, 2010).

Educational Implications: A student infected by toxoplasmosis may need a variety of vision supports and services, but it is dependent upon the area and severity of the affected vision.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: User’s syndrome consists of a degeneration of the retina and congenital deafness (Cassin & Rubin, 2012, p. 285). The retinal degeneration found in Usher’s syndrome is a form of retinitis pigmentosa. Usher’s syndrome is usually inherited (Schwartz, 2010).

Effects on Vision: Retinitis pigmentosa, the form of vision loss found in Usher’s syndrome, in decreased peripheral vision, night blindness, and eventual total blindness (Cassin & Rubin, 2012, p. 241).

Educational Implications: Students with Usher’s syndrome will benefit from services from a teacher of students with visual impairments, orientation and mobility specialist, and services for students with deafblindness. Students may benefit from low vision aids, control of lighting and glare, alternate formats such as braille, and will need ongoing monitoring and changing support as their vision changes.

References:

Cassin, B., & Rubin, M. L. (2012). Dictionary of Eye Terminology, 6th Ed. Gainesville, Florida: Triad Publishing Company.

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

Description: Uveitis is inflammation of the iris, retina, or other structures within the eye (Schwartz, 2010). Its cause is not always known, but potential causes may include infection, trauma, surgery, and autoimmune disease. Complications of uveitis may include cataracts, glaucoma, retinal detachment, and bleeding and swelling of the retina (Schwartz, 2010).

Effects on Vision: Most causes of uveitis cause decreased visual acuity. Vision is often unstable (Schwartz, 2010)). Complications such as glaucoma and retinal detachment may affect visual fields, if present.

Educational Implications: Students with uveitis may benefit form magnification, control of lighting and glare, and braille instruction in cases of severe vision loss (Schwartz, 2010).

References:

Schwarts, T. L. (2010). Chapter 6: Causes of Visual Impairment: Pathology and Its Implications. In A. L. Corn, & J. N. Erin (Eds.), Foundations of Low Vision: Clinical and Functional Perspectives (2nd Ed., pp. 137-191). New York, NY: AFB Press.

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