Many ODs are intimidated to work with patients when their visual needs can no longer be met with a simple refraction. They have flashbacks to low vision class with formulas for calculating magnification and fear they won’t remember them correctly. But with a few quick tips, you can feel more comfortable working with visually impaired patients and help your patients get back to doing what they love.
This guide will serve to help the primary care OD incorporate some low vision techniques into your complete eye exam. These tips can also be extrapolated for further low vision work-ups if you want to set your clinic up for this kind of care!
But first, download the cheat sheet!
Don’t forget, as soon as you are unable to meet your patients’ visual needs with the tools you have in your office, refer them to an optometrist who specializes in low vision. A patient with vision impairment can avoid years of frustration if they are referred to a low vision specialist early in their disease course. Low vision specialists can provide tools that can change with patients' visual needs, as well as give the patient hope for resources they can use if and when their vision worsens in the future.
A low vision exam is all about a thorough case history
History should at least include the following:
- Ocular/medical hx; ocular surgeries/treatments
- Hx of vision loss: assess what patient knows about their vision problem and when they started/worsened
- ADL: occupation/avocation/living situation/driving
- Chief complaint & Goals: Ask specific tasks pt needs help seeing: ie) reading mail vs reading email vs loading insulin syringe—pt’s goals will help guide what tools you recommend
Low vision is about helping someone use the vision they have to do the things they need and want to do every day.
How to succeed in a low vision exam: notes from the (visual) field
For visual acuity, have a chart with more large letter size options—i.e., digital acuity charts or ETDRS.
Contrast is available on many digital acuity charts:
- If reduced, the patient will need more magnification than based on VA alone
- Based on your patient's ocular disease, you will know whether they are likely to have reduced contrast (i.e., corneal scarring, cataracts, AMD all reduce contrast)
Make sure to perform visual field testing (including central field ie HVF 10-2 and/or Amsler) to determine scotomas!
Trial frame refractions:
Perform a trial frame refraction automatically if you know a patient has an ocular disease limiting their vision. This has several benefits:
- Allows the patient to move their head around to use their eccentric viewing position
- Gives a more accurate representation of your patient’s vision in the real world
- JND = Just noticeable difference = amount of lens power needed to elicit an appreciable change = lens size difference made during refraction
- To calculate JND, use VA denominator and divide by 100
- i.e., if VA is 20/200, JND is 200/100 = 2.00 D, so show the patient +1.00/-1.00 in sequence during TF refraction; depending on which the patient prefers, remember the change you made was 2.00D in this example, so if the patient likes plus, you would add +2.00 over sph already in TF
- Use larger change JCC
Immediately following your distance trial frame refraction, perform trial framing at near. Remember, higher add powers for SV near glasses. Use the Kestenbaum Formula:
- To determine minimum add (or amount of accommodation required) to read 1M print (average newspaper size print)
- Invert BCVA, ie BCVA 20/200 would then be 200/20 = 10 D
- Add = +10.00 (over distance correction)
- This can be manipulated depending on goal print size
- If the goal is 2M print, which is twice as large as 1M print, you only need half add power (or +5.00 for prior example)
- Working distance = 1/D = 1/10=0.1m (10 cm) working distance for above example
- Dioptric power can also be used to select magnification needed in hand or stand magnifiers (each magnifier is labeled with its dioptric value in addition to its magnification)
Keep in mind that patients can only read binocularly with about a maximum of +10.00 or +12.00D. If add needed is much greater than this, add should be applied to better functioning eye and occlude fellow eye so the patient can read monocularly.
Consider type of glasses
If a patient has a large scotoma, (ie advanced glaucoma, hemianopia, etc) do not recommend a traditional progressive for them which will further limit their peripheral vision. This may not be as much of an issue with newer digital progressives which have significantly improved peripheral vision.
Beyond glasses: trial magnifiers and tints!
Consider fall risk
If a patient already has vision loss (especially if they are older), they may be at risk of falling. Unless the patient is already comfortable with a bifocal or progressive for walking around, be careful about putting someone in this type of lens. Be especially careful about putting someone in a bifocal or progressive if you are giving a higher than typical add power.
Take the time to explain the disease to the patient and any family members present as well as its functional effects. Even though a patient may have been suffering from an eye condition for many years, they may not truly understand what is going on. Other family members may not fully comprehend the condition either. Explaining where the person has blind spots or which tasks will be difficult for the patient to see can help the family be more understanding of both the patient and their eye condition. The family member also knows what goes on at home and other specific needs the patient may have. Opening this dialogue can better help you help the patient.
Refer to a low vision specialist
Low vision referrals are best made to large centers, whether state run or private non-profits. In addition to providing low vision evaluations, they will also connect patients with various other resources. These resources include:
- technology training classes
- orientation and mobility training
- counseling (losing vision causes grieving just like any other loss)
- other life skills classes
They will be best equipped to meet all your patient’s needs. If this is not available in your area, refer to an optometrist who practices low vision and they should know other social organizations to connect the patient and meet their multifaceted needs.
You may decide to have large print business cards and a large print option on your website to make your patients with low vision feel more comfortable.