What's "good enough" visual acuity?

Some of you may recall the late 'hard' science fiction author Jerry Pournelle. From about 1982 to 2008, he wrote a regular computer column (Chaos Manner) for Byte magazine in which he championed "good enough" computer performance, based on the idea, as I recall, that most people should seek equipment and performance good enough for their needs rather than the best and most expensive.

.

In this spirit, as I have contemplated my choice of IOL and vision strategy, the question has occurred to me, what's good enough vision? For me, being too risk averse to choose a multi-focal IOL, this question has at least two aspects. One is entirely subjective: what range of vision do I want to prioritize? Some choose distance vision; a few choose near or intermediate. This is not the subject of this inquiry. (Nor is contrast sensitivity, which goes to vision quality.)

.

The other aspect I think has more of an objective component, namely: what counts as good enough vision so that, at any distance within its, one can see comfortably without glasses? For these purposes, I assume that wearing glasses can correct any deficiency.

.

Having no clear idea about the answer, when I looked at defocus curves for the Eyhance IOL—my surgeon’s recommendation and my current choice—I arbitrarily differentiated different ranges, e.g., 20/20–25; 20/26–32 (logMAR 0.2); 20/33–40 (driving cut-off); etc. Yesterday, however, I ran across a blog post at For Eyes, that, citing the American Optometric Association, lumped together 20/30–60 saying: “This means you may have a small vision issue, but your vision is almost normal. It’s unlikely you’ll need to wear glasses all the time.” See Starting At What Level of Prescription Should I Wear Glasses All the Time? (Note that the linked AOA webpage doesn’t quite say this.)

.

Accordingly, I’d appreciate your thoughts regarding what counts as “good enough” vision. To explain how I want to use the concept, averaging three binocular Eyhance defocus curves that I’ve found on-line suggests that, if my surgeon’s preferred target of -0.50 D is achieved, the mean uncorrected distance visual acuity for subjects in the three studies was 20/22 (logMAR 0.0467), which I’m inclined to think would be more than good enough vision. They also suggest that, at 40 cm (15.75”), the mean visual acuity was 20/38 (0.273 logMAR), about which I’m doubtful. In contrast, and momentarily assuming no degradation in visual acuities from 0.75 D mini-monovision, mean visual acuity with -0.50 and -1.25 D eyes indicatively would be 20/28 (0.153 logMAR) at 36.36 cm (14.31”) and 20/32 (0.2 logMAR) at 33.33 cm (13.12”), about which I’ve no clear idea.

.

For anyone interested, the three binocular Eyhance defocus curves mentioned above can be found on-line at the following sources:

.

Gerd U. Auffarth, et al., Clinical evaluation of a new monofocal IOL with enhanced intermediate function in patients with cataract, J Cataract Refract Surg 2021; 47:184–191.

.

Mayank A. Nanavaty, et al., Visual Acuity, Wavefront Aberrations, and Defocus Curves With an Enhanced Monofocal and a Monofocal Intraocular Lens: A Prospective, Randomized Study, J Refract Surg. 2022;38(1):10-20.

.

Ella SeoYeon Park, et al., Visual outcomes, spectacle independence, and patient satisfaction of pseudophakic mini‑monovision using a new monofocal intraocular lens, Nature Scientific Reports (2022) 12:21716.

1 like, 18 replies