A walk through of a low vision exam ...
Imagine being able to see well one day, and the the next day, you wake up and cannot see anything from the tips of your fingers to the door in the room you are in. You aren't able to read letters, watch TV, scroll through your phone, read a book or message your friends. It's hard for you to turn on the stove to cook and see the color of raw or cooked meat. You can't read the text on a microwave. Because you can't see you also lose the ability to drive- driving yourself to work, school, or picking up your children. When someone has a condition that causes this progressive loss of vision and the person is struggling to function in daily life, a low vision exam can be beneficial to see if he/she can benefit from using any functional low vision devices, counseling, or in-patient services, or occupational therapy.
A low vision exam is different from a comprehensive eye exam that the general public is used to-- the usual "1 or 2?" to figure out glasses or contacts, including a brief examination of the eye health to screen for any conditions. In low vision, these patients are beyond the need for a simple pair of glasses or contacts to see 20/20.
Usually, the patients coming in for a low vision exam are referred by a
primary eye care provider because a patient can't see well. These underlying conditions can be chronic,
acute, or congenital causes that usually causes irreversible and declining vision changes. Examples of conditions that can cause irreversible vision loss include
diabetic retinopathy, macular degeneration, glaucoma, retinitis
pigmentosa, etc. Usually the loss of permanent vision becomes debilitating to the patient.
The primary focus of these exams is structured for the patient. The sequencing can vary on a case by case basis. It includes everything from visual skills to sensory and motor skills. The person's age, occupation, personal lifestyle and family support are also taken into account. The majority of time is spent on case history-- figuring out why the patient is here, what the needs of the patients for their visual function. With impaired vision, does the patient live alone? Is he able to get around to get groceries? cook? get to work? Is he able to do his work properly and can we help him with any visual aids or consultation? Does he go to school? Does he need Braille or auditory books, large print brooks to be able to study his material and take tests? It's also important to note motor skills and sensory skills. Is he/she able to recognize touch i.e. to use a device that requires a patient to touch certain digits to help the patient out. Is the patient also mobile enough to learn how to use a blind cane, or is the patient immobilized and wheelchair bound? All these are things to consider to help the patient live the best life the patient has given the conditions he/she is in.
Often times, referrals with ancillary providers are also consulted. Occupational therapists can help a patient relearn everyday tasks. Psychologists may help with a patient who may be grieving over loss of vision or functionality on life, family issues due to impaired vision problems. Social workers and local government workers are useful to help a patient find a job placement or seek job training for work, finding housing etc. These everyday tasks are things a seeing eye person may take for granted than an impaired vision person needs to relearn and adapt. But it can be done with a low vision consult.
Other than an extensive case history, the low vision optometrist will continue on with the exam:
- assessing visual acuities at distance and near to determine what his/her potential acuity could be with aids
- ability to use mobile and immobile devices for distance and near (can a patient walk? Do they have tremors that prevent them from using hand-eye coordination to operate a small magnifying glass? Are their cognitive abilities intact to learn a new skill or complicated device to operate?
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Low vision case of the day:
During my clinical rotation at a low vision clinic, I was presented with a patient who had Stargardt's disease.
Typical description in a case: young onset in life, early macula degeneration, usually early loss of central vision, up to 20/200
aka "fundus flavimaculatus"- the appearance yellow flecks in the macula
Tests to diagnose:
DFE: fish fleck lesions, macula lesion
fundus photos
color testing
visual field testing: standard Humphrey VF, Octopus (for low vision)
ERG
OCT of the macula
Treatment: Low vision aids to help with visual demands, helps with contrast, color, central vision loss
24 y.o. M with previous Stargardt's history
- about 20/80 to 20/70 vision
- accounting student who adapted pretty well for studying: needs to hold things up close and use large print for reading, can't really see well in the distance to read words on the board in school and to read street signs for driving. Usually this patient just asks classmates for notes in class, listens to instructors in class.
- Patient was interested in driving in IL (in IL, an optometrist can prescribe a bioptic device to use while driving if the patient receives the proper number hours of training to learn how to look and use a bioptic). A bioptic device is an instrument with 2 oculars. One of the ocular has a small telescope attached that helps magnifies objects and words at a distance. The telescope is only to be glanced at to find street signs and not to be viewed at while driving-- similar to looking through the rearview to look behind you. It looks like a pair of glasses with a small tube sticking out of one side of the glasses.
After doing a low vision exam on the patient, we educated the patient on different devices that may help the patient. We demonstrated how to use and showed it to the patient to see if it could be useful for the patient.
Examples of devices:
Distance:
1. full field microscope (large + spectacles with BI added to decrease convergence) - looks like really thick glasses with high plus that helps magnifies objects at a distance. This patient felt the mag was too strong.
2. hand held microscope: looks like a small telescope that the patient brings up to his face and uses one eye to look through. best vision, good for spotting things at a distance like a person's face, reading subtitles on TV, reading the screen in the classroom, but not hands free. Can't use with driving.
3. Max TV: hands free, but patient had decreased vision (spectacles with adjustable zoom/mag)
4. bioptic microscope: needs to be fitted, most expensive, upwards $1000+, can be eligible to pass driving test in IL after trained. Similar to HHM, but magnifier is placed on one of the lens so patient can be hands free and just glance at the magnifier once in a while to read a street sign or look at the board.
At Near:
1. menas zoon stand magnifier (Dome shape)- easy to use; place on reading material and move around to read
2. bar stand magnifer: place on reading material (straight line); clear lines but not as easy to use. There is less surface area because is a rectangular and can only read one line at at time where the Dome shaped magnifier has a larger surface area to glance at a few lines above and below.