Lens-based strategies to address reading issues due to mild, disease-related vision loss
We all see patients with mild vision loss (best corrected vision 20/25 to 20/40, for example) who report their vision does not allow them to read the way they did in the past. Let’s discuss some strategies I use when refraction doesn’t yield a vision improvement and further disease treatment isn’t warranted.
| Written by Janis Winters, O.D., chair of the AOA’s Vision Rehabilitation Committee.
I try to clarify what the patient means by “issues with reading.” As you know, this complaint can be related to reading duration, reading speed, a different font/color of text, difference in working distance, etc. A better understanding of the complaint can help define a solution.
Add/reading glasses prescription
Sometimes increasing the add or reading prescription can solve the issue. I often use Kestenbaum’s rule as a guide. Kestenbaum’s rule states the inverse of the distance best corrected visual acuity is the power needed to read 20/50. So, if I double the result the patient should see 20/25. For example, if the patient’s BVA is 20/40, Kestenbaum’s rule would approximate that with a +2.00 reading prescription the patient would read 20/50 and with +4.00 the patient would read 20/25. Of course, an increase in add/reading glasses power influences working distance. That is something to consider based on your patient’s goals. Another consideration is reading reserve, which is needed for efficient, long-term reading. I will often correct to several lines lower than the patient’s goal acuity to allow for reading reserve.
Consider binocular status
With increased add or reading glasses prescription, there is an increased convergence demand. While proximal convergence is thought to increase in those who have presbyopia, this increase in convergence demand still may be significant. I think about the binocular status of my patient considering phoria and vergence testing. Base in prism can be incorporated to lessen convergence demand; however, this may necessitate reading-only glasses instead of bifocals. A rule of thumb that is often used in vision rehabilitation: prism in reading glasses equates to two prism diopters more than the dioptric value of the reading power in each eye. So, for a +4 reading prescription, 6 BI prism diopters in each eye would be incorporated.
Other issues may be the root cause for the vision complaint, such as dry eye or functional vision loss or even cognitive impairment. Dry eye must be evaluated and treated appropriately. Central/peripheral visual field loss, contrast sensitivity loss or glare issues may be the root cause of the reading complaint.
If this is the case, other strategies may be needed to solve the patient’s complaint. Sadly, I see patients whose vision complaints don’t have to do with vision but are related to dementia or other issues. Education along with interdisciplinary communication is needed to manage these patients.
If you are unable to solve the patient’s complaints, consider referral. You can find AOA colleagues who practice a variety of specialties, including low vision or vision rehabilitation.
Written by Janis Winters, O.D., chair of the AOA’s Vision Rehabilitation Committee.
Disclaimer: The information contained in this article represents the opinion of the author and not the AOA. These are not clinical practice guidelines, nor has the evidence been peer reviewed. There are additional aspects to this topic that may not be presented, or considered, based on the specifics of the case.
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