(color deficiency, colorblindness, achromacy or rod achromacy) Cone Malformation, macular deficiency, and partial or total absence of cones.
Effects on vision:
Limited or no color vision
Colors may be seen as shades of gray
Loss of detail
Decreased acuity
Central field scotomas
Normal Peripheral fields
Associated with nystagmus and photophobia
Educational considerations:
Adapted color-dependent activities
Alternate methods for matching clothing
Support of eccentric viewing
High contrast materials
May need to use sunglasses, visors or hats outdoors and indoors
Reduced or diffused lighting
Supplement vision with auditory and tactile information
Total or partial absence of pigment, causing abnormal optic nerve development. Lenses and tinted lenses may be prescribed.
Effects on vision:
Decreased acuity
Photophobia
Increased sensitivity to glare
High refractive error
Astigmatism
Central scotomas
Nystagmus
Muscle imbalance
Eye fatigue with close or detailed work
Reduced depth perception
Educational considerations:
Magnification
Close viewing
High contrast materials
May need to use sunglasses, visors, or hats outdoors and indoors
Lighting from behind
Reduced glare
Line markers and templates - placeholders
Frequent breaks
(was Anopsia, also called "lazy eye") see strabismus -
Reduced visual functioning in one eye, which causes the person to use one eye instead of both. With young children, eye exercised, occlusion or patching of one eye or surgery may help.
Effects on vision:
Monocular vision
Reduced visual field
Reduced depth perception
May develop blindness in one eye
Reduced visual-motor abilities
Eye fatigue with close or detailed work
Educational considerations:
Frequent breaks
Seating should favor functional eye
Familiarization with new environments
Time to adjust in new situations
May need adaptations for activities requiring visual-motor coordination
A rare genetic disorder that causes absence of all or part of the iris, usually affecting both eyes.
It also causes the cornia to lose clarity over time by inhibiting the stem cells that "refresh" it with new, clear epithelial cells. Aniridia is often associated with amblyopia, cataracts, the developement of closed angle glaucoma, and sometimes, displaced lens, under-developed retina, and nystagmus. Contact lenses with an artificial iris, tinted spectacles, or bioptic glasses may bbe prescrived. Iris and stem cell implant surgeries are now possible.
Hereditary aniridia is associated with Gillespie syndrome. Sporadic Aniridia may cause nephroblastoma (Wilm's tumor), and it is associated with WAGR syndrome.
Effects on vision:
Decreased acuity
Photophobia
Large pupil that may be misshapen
Generally, respond very well to use of low vision devices
Corneal involvement: scattered light, increased glasre, blurred vision, and further reduction of acuity
If cataracts develop: further reduction of visual acuity, blurred vision, and decreased color vision
Foveal involvement: loss of detailed vision
If glaucoma develops: fluctuating visual function, field loss, poor night vision, and decreased sensitivity to contrast
Educational considerations:
Vision stimulation for infants to maximally develop the visual cortex
May need to use sunglasses, visors or hats outdoors and indoors
Allow time for adjustment to lighting changes
Provide seating in the front of the classroom with back to windows
Reduced glare
Provide lighting from behind
Reduced or diffused lighting
Lamps with rheostats and adjustable arms
Magnification
Use of a black chalkboard and bold chalk
If white board is used, bold black markers are recommended over other colors
Felt-tipped pens and tinted paper with bold lines
Place paper/worksheets on a dark/black background
Provide copies of materials presented on the board
Use black backgrounds and white san serif fonts in slide presentations
Absence of one or both eyeballs.
Causes can be heredity, injury, or secondary to disease. Prosthetic eyes are prescribed to preserve the health of the eyelids and surrounding tissues.
Effects on vision:
Monocular vision
Reduced depth perception
Blindness
Educational considerations:
May need visual efficiency training to develop scanning skills
Seating and presentation of materials should favor functional eye
May need tactile and auditory learning media
Absence of the lens.
Although it can b caused by injury, aphakia is usually a result of cataract surgery. Treatments include lens implants, contact lenses, and/or glasses.
Effects on vision:
Inability to accommodate to varying focal distance
Inability to accommodate to lighting changes
Reduced depth perception
May have peripheral field distortions
Educational considerations:
Support wearing of any prescribed lenses
High contrast materials
Magnification
Enlarged printed materials
Close viewing
Adequate lighting
May need sunglasses, visors, or hats outdoors and indoors
Allow time for adjustment to lighting changes
Irregularity in the curvature of the cornea and/ or lens, which prevents light rays from being properly focused on a single point on the retina
Astigmatism commonly occurs with myopia and hyperopia. It also can be associated with albinism and keratoconus.
Corrective lenses may be prescribed.
Effects on vision:
Blurred vision at any distance (uncorrected)
Distorted vision
Tendency to squint to create a pinhole effect
Visual fatigue associated with close work
Educational considerations:
High contrast materials
Adequate lighting (e.g., lamps with rheostats and adjustable arms)
Frequent breaks from close/ detailed work
(Infantile glaucoma) Enlarged eyeballs
Caused by congenital glaucoma; hereditary; onset from birth to three years; can cause enlargement and increased depth of the anterior chamber, damage to the optic disc, and/or increased diameter and thinning of the cornea; requires surgery, and blindness occurs if left untreated.
Effects on vision:
Photophobia
Reduced central acuity
Corneal opacity
Refractive error
Eye pain
Educational considerations:
May need to use sunglasses, visors or hats outdoors and indoors
Reduced or diffused lighting from behind
Allow time for adjustment to lighting changes High contrast materials
Magnification
Enlarged printed materials
Close viewing
Opacity or cloudiness of the lens, which restricts passage of light to the retina; usually bilateral.
Opacity increases over time until "mature" cataracts can obscure the fundus and the pupil may appear white. Mature cataracts are usually removed surgically, requiring lens implants or contact lenses.
Effects on vision:
Reduced visual acuity
Blurred vision
Reduced color discrimination
Photophobia
Associated with nystagmus
Visual ability fluctuates according to light
If cataracts are centrally located, near vision will be reduced
Increased sensitivity to glare
Educational considerations:
Support of the wearing of any prescribed lenses
Magnification (e.g., handheld magnifier, electronic magnifier, screen enlargement software, telescope, etc.)
Enlarged printed materials
Close viewing
Support of eccentric viewing
May need to use sunglasses, visors, or hats outdoors and indoors as well
May need reduced or diffused lighting
Lighting from behind
May need lamps with rheostats and adjustable arms
Reduced glare
Posterior uveitis, or an inflammation of the choroid that spreads to the retina.
This can be caused by tuberculosis, histoplasmosis, or toxoplasmosis.
Effects on vision:
Blurred vision
Photophobia
Distorted images
Central scotomas
Educational considerations:
Support of the wearing of any prescribed lenses
Magnification (e.g., handheld magnifier, electronic magnifier, screen enlargement software, telescope, etc.)
Enlarged printed materials
Close viewing
Support of eccentric viewing
May need to use sunglasses, visors, or hats outdoors and indoors as well
May need reduced or diffused lighting
Lighting from behind
May need lamps with rheostats and adjustable arms
Reduced glare
A congenital, nonhereditary, and progressive disorder that is characterized by abnormal development of the blood vessels behind the retina.
Coats' occurs mostly in males. Symptoms typically appear in children around six to eight years old but they can appear in infancy. Coats' usually affects only one eye. Severity depends on the size and number of affected blood vessels. Leakage of blood and fluids cause retinal swelling and detachment.
Cryotherapy and laser photo-coagulation sometimes are used to stop the progression of blood vessel growth and leakage.
Effects on vision:
Decreased central acuity
Loss of detail
Progressive central field loss
Reduced night vision
Loss of color vision
May develop strabysmus
May have iritis
May have glaucoma
May develop cataracts
May be blind in one eye
Peripheral fields can be affected
Educational considerations:
Avoid contact sports and other high risk activities to prevent retinal detachment
Seating and presentation of work should favor more functional eye
Visual efficiency training to develop scanning skills
Hereditary birth defect that casues a notch or cleft in the pupil, iris, ciliary body, lens, retina, choroid or optic nerve. A "Keyhole" pupil often occurs. It can be associated with refractive error, cataracts, nystagmus, strabismus and glaucoma (later in life).
Effects on vision:
Decreased acuity
Photophobia
Muscle imbalance
Restricted fields (if retina is affected)
Reduced depth perception
Educational considerations:
High contrast materials
Magnification (handheld magnifier, electronic magnifier, screen enlargement software, telescope, etc)
Average to bright light
Reduced glare
May need to use sunglasses, visors or hats outdoors and indoors as well (if iris is affected)
High contrast line markers and templates may be helpful for reading, finding math problems or locating other information
An open sore of scarring on any part of the cornea.
It can be caused by bacteria, viruses (herpes), fungi, vitamin deficiency, injury, a hypersensitive reaction, diabetes or severe dry eye. Superficial ulcers (called abrasions) usually heal quickly and completely, but deep ulcers cause growth of scar tissue or new blood vessels that impair vision. Corneal ulcers are usually quite painful and other symptoms may include vision loss, squinting and tearing (watering). Early diagnosis and treatment are curcial. With extensive scarring, a corneal transplant may be necessary. There are promising results with use of artificial conreas, which seem to be less likely to be rejected.
Effects on vision:
Photophobia
Fracturing of light (like looking through broken glass)
Increased glare
Blurred vision
Reduced acuity
Blindness
Educational considerations:
May need to use sunglasses, visors or hats outdoors and indoors as well
Reduced or diffused lighting
Seating in front of room with back toward windows
Reduced glare
High contrast materials
Diffused lighting from behind
Lights with rheostats and adjustable arms are helpful for close work
Magnification
Enlarged printed materials
Frequent breaks from visual tasks
Support of eccentric viewing
May need auditory materials for longer reading assignments
A neurological visual disorder resulting from damage to the optic nerve and/or parts of the brain that process and interpret visual information (i.e., visual cortex)
CVI is characterized by:
Specific color preference, especially for red and/or yellow
Attraction to movement
Visual field preference, especially for peripheral fields
Visual latency: delayed visual processing - in directing gaze, identification, recognition and/or discrimination
Difficulties with discrimination and interpretation of complex visual information
Poor visual attention
Atypical visual responses (i.e., looking at something while appearing not to look)
May not look at an object and reach for it simultaneously (look first, then look away while reaching)
Better visual performance with familiar objects/settings
Unique visual features (i.e., light gazing and nonpurposeful gaze)
Effects on vision:
Fluctuation in visual functioning
Reduced visual fields
Photophobia
Fatigue has a negative impact on visual performance
Educational considerations:
Use of movement to increase visual attention
Use of preferred color to increase visual attention
Present visual information in preferred visual field
Present visual information on a solid background (e.g., black or white cloth)
Use of bright, high contrast materials
Increase line spacing and white space on a page of text and/or images to reduce visual clutter and complexity
Use high contrast templates to reduce the amount of information seen at one time
Close viewing
Vision efficiency training
Frequent breaks from visual tasks
High illumination from behind
Sunglasses, visors or hats, indoors or outdoors
Support use of one sense at a time
Reduce visual, auditory and tactile distractions
Extra time to respond
Extra time to adjust to new environments
Use of consistent language
Use of color coding as visual cues for recognition
Use of consistent visual cues across settings
Changes in the blood vessels of the retina, causing hemorrhaging in the retina and vtreous.
It is caused by juvenile or type 2 diabetes. It may lead to retinal detachment and blindness.
Effects on vision:
Increased sensitivity to glare
Lack of accommodation
Floating obstructions in the vitreous
Fluctuating acuity
Diminished color vision
Reduced visual fields
Double vision
Blindness
Educational considerations:
Adequate high quality lighting (e.g., lamps with rheostats and adjustable arms)
High contrast materials
Magnification
Large button/key technology may be helpful
Training in use of auditory materials may be needed due to loss of vision and tactile sensitivity
Training in use of speech recognition input software may be helpful
Precautions related to decreased sensitivity in hands and feet (e.g., burns, cuts, falls)
Muscular defect that restricts the ability of the eyes to work together.
It causes double vision, as the image from one eye is imposed on the image from the other eye. Left untreated, this condition can develop into amblyopia. Corrective lenses may be prescribed.
Effects on vision:
Visual confusion
Double vision
Dizziness
Suppression of the image from one eye, causing monocular vision
Eye fatigue
Blurring of print
Headache
Loss of place in visual tasks
Educational considerations:
High contrast materials
Reduced glare
Extended time to adjust to new situations
Frequent breaks from visual tasks
High contrast line markers or templates for reading, finding math problems, or locating other information
Familiarization with new environments
The lens is not in its natural position.
It isi sometimes associated with coloboma, Marfan's syndrome or Marchesani's syndrom. Also, it may be associated with diplopia or cataracts.
Effects on vision:
Blurred vision
Double vision
Visual fatigue during close or detailed visual tasks
Educational considerations:
Frequent breaks from visual tasks
High contrast materials
Adequate lighting (e.g., lamps with rheostats and adjustable arms)
Reduced or diffused lighting
High contrast line markers or templates for reading, finding math problems or locating other information
The anterior chamber or the entire eyeball is surgically removed from the orbit (eye socket).
Prosthetic eyes or scleral shells are usually recommended.
Effects on vision:
If one eye is removed, there is no depth perception
Monocular vision
Reduced visual field
Blindness
Effects visual-motor skills, especially reach and negotiation of steps and drop-offs
Educational considerations:
Training in care of prostheses
Vision efficiency training (i.e., scanning)
Considerations related to the visual impairment of the remaining eye
Considerations related to possible changes in learning media
An eye disease which causes increased pressure in the eye because of blockage in the normal flow of the fulid in the aqueous humor.
Causes include changes in the lens or vueal tract, trauma, reaction to a medication, surgical procedures, and heredity. Eye pain and headaches are associated with glaucoma.
Prescription eye drops to deduce pressure must be sued regularly, and surgery may be necessary. Untreated, glaucoma can lead to degeneration of the optic disk and blindness.
Effects on vision:
Fluctuating visual functioning
Field loss
poor night vision
photophobia
Difficulty reading
Difficulty seeing large objects presented at close range
Decreased sensitivity to contrast
Eye redness
hazy cornea
Wide open pupil
stress and fatigue have a negative affect on visual performance
Educational considerations:
May need to use sunglasses, visors or hats outdoors and indoors as well
Allow time for adjustment to lighting changes
Reduced glare
Lamps with rheostats and adjustable arms
High contrast materials
May benefit from magnification
May need visual efficiency training to develop scanning skills
Frequent breaks from visual tasks
May need instruction in tactile learning and braille
Teachers must be alert to signs of pain and increased ocular pressure.
Blindness or impaired vision in one half of the visual field in one or both eyes.
If both eyes are affected, vision loss may occur on the same side, in both nasal fields, or in both temporal fields. Visual acuity in the unaffected field(s) remains unchanged.
Hemianopia can be caused by stroke, other brain trauma, tumors, infection, or surgery.
Effects on vision:
Field loss
May be unaware of missing visual information
Educational considerations:
Visual efficiency training to develop scanning skills
Use markers at the beginning and/or ending of each line of text to facilitate reading the entire line
This is a syndrome affecting the choroid and retina, which is characterized by peripheral atrophic chorioretinal scars, maculopathy, and atrophy or scarring adjacent to the optic disc. Vision loss is secondary to macular and choroidal neovascularization (CNV).
POHS is most likely caused by a fungal infection acquired through exposure to spores in bird droppings and bat guano. Treatments include steroids to treat the initial infection, laser, anti-vascular endothelial growth factors, and photodynamic therapy. Prism lenses may be prescribed.
Effects on vision:
Distorted vision
Blind spots
macular damage or central scotomas cause "patchy" fields, central vision loss, and reduced color vision
Peripheral damage causes loss of night vision
Educational considerations:
Lamps with rheostats and adjustable arms
High contrast line markers or templates for reading, finding math problems, or locating other information.
Central damage:
Eccentric viewing
Magnification to enlarge an image beyond the scotoma
Enlarged printed materials
Close viewing
Adapted color-dependent activities
Alternate methods for match clothing
Diffused, less intense light to enlarge the pupil so that more area can be viewed
Magnifier with reversable foreground and background
Peripheral damage:
High Illumination
NOIR lenses or overlay filters may be helpful
Video magnifier for maximum contrast
Night vision devices
Visual efficiency training in organized search patterns
may need to be seated farther away from the front to see more of the viewing area
A refractive error in which the focal point for light rays is behind the retina.
It is caused by the eyeball being too short from front to back. Corrective lenses are usually prescribed.
Effects on vision:
Distance acuity is better than near acuity
Uncorrected, close visual tasks may cause headache, nausea, dizziness, and eye rubbing
Educational considerations:
Support use of prescription lenses for close visual tasks
Magnification for near tasks
Frequent breaks from close visual tasks
Alternate near and distance visual tasks
Degenerative disorder in which the cornea thins and takes on a conical shape. Keratoconus is often bilateral but not symmetrical, so vision may be significantly better in one eye than the other. Vision deteriorates at varying rates (sometimes quite rapidly), and plateaus of stable vision can occur. Although it seems to be hereditary, keratoconus is typically diagnosed in adolescence. It is sometimes associated with retinitis pigmentosa, Down's syndrome, Marfan's syndrome, and aniridia. Treatments include prescription lenses and various surgeries: intrastromal corneal ring segments, cross-linking, mini asymmetrical radial keratotomay, and corneal transplants. There are promising results in transplants with use of artificial corneas, which seem to be less likely to be rejected.
Effects on vision:
Slightly blurred vision in early stages, increasing as KC progresses
Distortion of entire visual field, which worsens in low light
Decreased visual acuity especially distance vision
Irregular astigmatism (parts of the field are in focus, and parts are out of focus)
Increased sensitivity to glare
Decreased night vision
Multiple images
Flaring of images
Streaking
Stationary objects/lights may appear to move
May develop photophobia
Cornea can rupture
Can lead to blindness
Educational considerations:
Avoid activities that could cause corneal damage, such as contact sports and swimming in heavily chlorinated water
Reduced glare
Diffused lighting
Lamps with rheostats and adjustable arms
High contrast materials
High contrast line markers or templates for reading, finding math problems, or locating other information
Magnification (e.g., hand-held magnifier, screen enlargement software, telescope, etc.)
A rare hereditary disorder that leads to degeneration of the macula. LCA becomes evident within the first few months of life. Progressive central field loss can occur, although vision is grenerally stable. LCA is a subset of retinitis pigmentosa with at least thirteen described types that are distinguished by genetic cause, patterns of vision loss, and associated eye conditions. Nystagmus, keratoconus, photophobia, and sluggish (or absent) pupilary response to light are often present with LCA. Excessive rubbing of eyes (also poking or pressing) is a characteristic behavior.
Effects on vision:
Decreased acuity
Reduced night vision
Progressive central field loss
Loss of color vision
Loss of detail
Peripheral fields can be affected
Educational considerations:
May need visual efficiency training to develop scanning skills
Support of eccentric viewing
Magnification (e.g., hand-held magnifier, screen enlargement software, telescope, etc.)
High contrast materials
High contrast line markers or templates for reading, finding math problems, or locating other information
Enlarged printed materials
Close viewing
Adapted color-dependent activities
Alternate methods for matching clothing
Lamps with rheostats and adjustable arms
Support use of sunglasses, visors, or hats in bright sunlight
Seat in the front of the room with windows behind back
May need frequent breaks from visual tasks
May need instruction in use of auditory materials
May need instruction in tactile learning and braille
ONH and Septo-Optic Dysplasia (SOD) are related disorders of early brain development. ONH is a congenital, nonprogressive condition in which the optic nerve is under-developed and small.
It may affect one or both eyes, and when both are affected, side-to-side nystagmus is frequently present. During the first few years of life, vision may improve as the brain continues to develop. The incidence of strabismus is increased with ONH. It is one of the three defining characteristics of Septo-Optic Dysplasia, which is also called DeMorsier's Syndrome. Learning disability, autism, cerebral palsy, and intellectual developmental delays can occur with ONH and SOD. Possible causes include young maternal age, genetic mutation, fetal alcohol syndrome, trauma, and viral infection.
Effects on vision:
May decreased acuity
May have better acuity in one eye than in the other
May have nystagmus
May have strabismus
May have variable field restrictions
Visual perception may be impaired
Educational considerations:
High illumination
High contrast
Enlarged printed materials
May need magnification (e.g., hand-held magnifier, screen enlargement software, telescope, etc.)
Avoid visual clutter: Present visual information in isolation, Avoid busy backgrounds, Avoid wearing patterned clothing when presenting visual information
Provide opportunities to confirm or clarify visual information through tactile exploration
May benefit from verbal descriptions to help make sense of visual information
May need adapted color dependent activities
May need alternate methods for matching clothing
May need instruction in tactile learning and braille
A degenerative disorder in which the retina splits into two separate layers, resulting in progressive loss of vision, beginning in the fields that correspond to the areas where the retina splits.
The hereditary form (juvenile X-linked retinoschisis) affects mostly boys and yound men. The more common form can affect both men and women, and it usually is acquired in middle age or older (senile retinoschisis). Both forms may be associated with cysts (sack-like blisters) that form a spoke-like pattern in the retina. Retinal detachments can occur, and if detected early, they sometimes can be repaired with surgery. Prismatic glasses may be prescribed to increase field of vision.
Effects on vision:
Strabismus
Nystagmus
Central field loss
Peripheral field loss
Reduced visual acuity
Reduced color discrimination
Blind spots (scotomas)
Blindess
Educational considerations:
Avoid contact sports and other high risk physical activity to prevent retinal detachment
May need visual efficiency training to develop scanning skills
May need visual efficiency training in organized search (grid) patterns
Adequate lighting (e.g., lamps with rheostats and adjustable arms)
Reduced glare
High contrast line markers or templates for reading, finding math problems, or locating other information
Frequent breaks from visual tasks
May benefit from access to auditory materials
May need instruction in tactile learning and braille
For central vision loss:
Nighttime orientation and mobility evaluation
Magnification (e.g., hand-held magnifier, screen enlargement software, telescope, etc.)
High illumination
Night vision devices (e.g., Streamlight flashlights, Third Generation Night Vision Devices, etc.)
Adapted color-dependent activities
Alternate methods for matching clothing
For peripheral field loss:
Increase viewing distance to see more area
Support of eccentric viewing
Balance need for larger viewing area with the need for magnification
(muscle imbalance)
Abnormal alignment of the eyes; an inability to look at the same point in space with both eyes at the same time.
It can be caused by a defect in the extra-ocular muscles or in the part of the brain that controls eye movement. It can be hereditary, and it may be associated with brain tumors, cerebral palsy, Down syndrome, extreme farsightedness, cataracts, or having much better vision in one eye than in the other.
Strabismus includes:
"phorias" muscles imbalances that are controlled by the brain's efforts toward binocular vision. Not always present, they tend to manifest when the person is tired.
"tropias" observable deviations that the brain cannot resolve. They are always present.
Eso - turned inward/nasal (esophoria and esotropis)
Exo - turned outward/temporal (exophoria and exotropia)
Hyper - turned upward (hyperphoria and hypertoropia)
Hypo - turned downward (hypophoria and hypotropia)
Treatments can be effective for young children: eye exercises, occlusion of the better eye, medications, and surgery. Prismatic glasses may be prescribed to increase field of vision.