Causes And Functional Consequences Of Visual Impairment Flashcards
Types of functional deficits in low visions
Cloudy media-no VF defect
Central field defect
Peripheral field defect
Cloudy media-no field deficit
Diseases of the cornea, lens, or vitreous
Central field deficit
Diseases of the macula or ONH, can also rarely be a neuro problem
Peripheral field deficit
Glaucoma
Neuro
Peripheral retinal problems
ONH problems
Cloudy media pateitns
- general blur across their vision
- these patients suffer from glare problems-think of patients post refractive surgery or patients with cataract
- they also have difficulty in situations with poor contrast
- with severe corneal problems, patients may see diplopia (kones)
Causes of cloud media-cornea
Dry eye-can be treated by primary care provider but may want to consider re refractive after condition is treated
Kones-often will be referred to specialty CL for eval rather than low vision
Corneal scaring
Causes of cloudy media-lens
Cataracts-of the patient is willing to undergo surgery, generally does not become an issue
- nuclear: generally just needs magnification
- cortical: needs glare control
- posterior subcortical: needs glare control, difficult to provide magnification
Nuclear cataracts need
Magnification
Cortical cataracts
Needs glare control
Posterior subcapsular cataract needs
Glare control, difficult to provide magnification
Causes of cloudy media-vitreous
- vitreous hemorrhages and inflamamtion provide nearly the same symptoms-depending on severity, they can completely block light from reaching the retina
- vitreous floaters can also be bothersome, and many pateitns have to learn to look around their floaters until they can ignore them
Management of patients with cloudy media
- as always, try to provide these patients with the best refraction possible
- test filters to help with contrast and glare sensitivity- a yellow/orange filter may help with contrast when reading, where a brown gray filter may help to reduce glare from the sun
- similarly, make sure that pateitns are reading with good lighting condition; they need a task lamp that can be positioned optimally to reduce glare as opposed to an overhead light or a light shining directly at them
- try magnification, but results may not be good due to reduced contrast
Central visual field deficit
- varying degrees of severity canc abuse a large range of visual acuities
- they patients will have a relative or an absolute scotoma in or near their central vision. Common complaints are difficulty seeing street signs, reading books, and identifying faces (especially at a distance)
- if the patient has one unaffected eye and one bad eye, they may not have symptoms other than reduced depth perception
- often reduced contrast sensitivity
Causes of central visual field deficits-AMD
AMD is currently the most common cause of low vision that ODs/MDs see in office
Dry AMD-this causes slow, progressive degeneration
- defects being as relative scotoma but may progress to absolute scotoma with time
- some patients may develop ring scotoma-the fovea is temporarily preserved while the surrounding area develop atrophy. These patients typically do well on acuity charts but struggle greatly with reading quickly
- patients with GA almost always have an absolute scotoma over those retinal areas
Wet AMD
This can cause sudden, severe degeneration
- less devastating now that it was 30 years ago due to success of anti-vegf treatments
- typically have more difficulty reading than may be expected from their VA
For both dry and wet AMD, what can be done for them
Illuminated magnifiers and improving contrast are important
-eyes may have differing levels of involvement, so consider demonstrating occlusion of one eye
Beginning treatment for AMD patients in low vision
It is important to begin treatment early if patients are motivated and have complaints-even as soon as 20/40, patients may have functional deficits with reading
AMD and eccentric viewing in low vision
Occasionally they may need to be trained to look above or below the defect to improve reading
Toxo and myopic degeneration as causes of central visual field deficit
- both causes field deficits similar to AMD but patients with myopic degeneration may be able to rake off their glasses instead of using magnifiers
- be very careful when refracting patients with myopic degeneration to avoid overminsuing them
- patients with scars from toxo usually have healthy retina surrounding their scars, so they may have acuities as good as 20/20
Optic nerve disorders as causes of central visual field deficits
- can cause central or cecocentral defects
- important to perform a visual field to know the baseline field loss
DR as a cause of central VF deficit
DR can fall under all fo the categories with differing complications
- vitreous hemorrhages can cause cloudy media
- AMD can cause central loss
- PRP to treat peripheral neo or retinal detachments from PDR can cause peripheral loss
What do DR pateitns need before low vision
Stable blood sugar for your glasses/magnification recommendations
If their blood sugar is never stable, it is okey to provide a Rx to the patient if they have the understanding that the glasses will not work unless that level is maintained
Management of patients with central VF deficits
- do a careful refraction0you may need to let your patient view eccentricall (be sure they are not cheating!)
- if available, perform perimetry of central VF to map defect. If not, use amsler grid
- patients may appreciate filters, especially yellow, for reading as they can improve contrast. Other techniques designed to improve contrast also work well
- magnification usually works well, both at N and D. If the patient has great results in your office but does not at home, the difference is usually lighting (occasionally it is contrast)
Peripheral VF deficits common complains
Bumping into objects, misplacing items or not being able to find items and difficulty navigating new environments
Diseases causing peripheral VF deficit can affect function in what ways
Many ways
-bitemproal hemiansopsia causes difference problems than an altitudinal defect, for example
Two overarching types of visual field defects
Generalized constriction, and sector or hemianopic defects
RP as a cause of peripheral VF deficit
- these patients will have gradual loss of peripheral vision, occasionally progressing to total blindness
- first complaint is usually night blindness, second is bumping into things
- miniature flashlights may be helpful for spot reading in dimly lit environments
- filters (often red) can be very helpful to reduce glare
- if the patient has very little VF or his condition is progressing rapidly (especially if the patient is young), consider recommending that the patient be evaluated for a reading assessment as well as O&M, as it is easier to learn Braille and white can training before it is absolutely necessary
Glaucoma as a cause of peripheral VF deficits
- these patients will have gradual loss of peripheral vision, occasionally progressing to total blindness (but this will hopefully be prevented through good screening and treatment)
- patients with moderate to advanced glacuaom often have poor contrast. Filter may help this
- with significant field loss, patients often need O&M
Neuro disorders a peripheral VF deficits
- Patients with hemianopsias will often have trouble reading, even though good acuity, especially if they have a right heminaopsia. Parting with left hemianopsias may have trouble finding the next line
- non-optical aids such as typoscopes can be very helpful for helping the patients to maintain reading on the same line
- these patients often require a multidisciplinary approach and have more problems than solely vision loss
- with significant field loss, patients often need O&M and scanning training
- it is always a good idea to have a caretaker or family member prestn to remind the patient of how to use devices, etc
Managment of patients with peripheral VF deficits
-refract
-glare control is important, especially for conditions affecting light and dark adaptation
-least magnification necessary (need to keep image in patients FOV)
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Field expansion for peripheral VisiCalc field deficits
Only with patients with good VAs. Generally teaching scanning techniques will work better, occasionally prims may be useful in helping patients learn to scan more efficiently
Orientation and mobility for peripheral VF deficits
Every patient with problems of bumping into things and have a decreased visual field (and are wiling) should be referred to an O&M instructor
