Optometry & Visual Performance 160 Volume 14 | Issue 2 | June 2026 Robert Hooke’s scientific work with astronomy and microscopy was groundbreaking, and we owe a lot to him, including our modern-day definition of good visual acuity. Remember, however, 20/20 is arbitrary and the result of an old employment test; it is not an absolute standard of ‘good sight,’ so do not, as good doctors with psychometric integrity, use it as a cutoff for refraction, an ideal goal acuity, or best-possible vision.” Noticing “You can observe a lot just by watching.” –Yogi Berra “Have you ever noticed,” Professor McIver began to the class, “that so much of what is done in the health care professions is that which was done in the past and handed down from generation to generation of practitioners without question? Don’t get me wrong, there is a lot of good, evidence-based practice being done, but so much of our daily care has not changed significantly in decades, as there is just not good evidence for everything we do.” “Why are you telling us this?” Hugh from the back asked. “If it’s been done for decades, shouldn’t it be just fine to continue?” “There it is!” Professor McIver exclaimed. “While it might be “fine”, we need to keep our eyes open for changes in our process of care if we are to consistently improve. There is a word for continuous improvement in Japanese: it is ‘kaizen.’ It is a mindset, a philosophy, and a methodology of making ongoing step-by-step progress and requires an open mind to keep watching for opportunities. Most steps of improvement are small and incremental, but sometimes those steps of improvement are large and might even be big enough to provide a chance for a punctuation of the equilibrium. For instance, back in the 1970s, a revolution in measuring visual acuity was largely sidelined by the inertia of years and years of recording acuity in the established, classic manner. Even though the old way no longer met the high standards of psychometric integrity, it had always been considered ‘fine’ and so endured (Bailey I, Lovie-Kitchin J, 2013). That should no longer be considered satisfactory for modern optometrists who adhere to psychometric integrity.” “Listen, why don’t we open up ‘The Source’ and see where the revolution came from and how we can still access its power in caring for our partially sighted patients?” “That sounds intriguing,” Hugh said, speaking for many in the class, “but until it can be demonstrated as superior, I still think ‘fine’ is ‘fine’.” “We’ll see if you still think so when I am done. So, here we go,” Professor McIver replied. “Math was advancing in the late 16th century when John Napier discovered logarithms and used them as an aid in calculating the large numbers needed for astronomy. By the early 17th century, he invented the calculating tool known as Napier’s Bones as a forerunner to the slide rule. The slide rule was invented by William Oughtred8 and eventually allowed three decimals of accuracy once Isaac Newton, Robert Hooke’s nemesis, added a slide a few decades later. The slide rule made modern industrial society possible and was de rigueur for all professions until the early 1970s, when affordable electronic calculators came on the scene as inexpensive and widespread for performing complex calculations. ‘So what’, you think, right?” Professor McIver asked rhetorically. “Exactly,” Hugh sighed, waiting for the end of the session. “It’s been a nice history lesson, but what does it have to do with patient care?” “Glad you asked,” Professor McIver continued, “as it has everything to do with rational decision-making in the clinic. Recall that, as you have been taught so far, we have vision charts and refraction techniques which were developed for fully sighted patients. The large, irregular-letter-size jumps on the chart and the 0.25 D lens steps were fortuitously workable for them in refracting the fully sighted. When we begin dealing with partially sighted patients, however, those systems break down quickly, causing frustration for both patients and doctors, and is one of the main reasons, in my opinion, that many practitioners shun low vision care.” “So, let’s continue to explore how math can be our friend in low vision rehabilitation. In the 19th century, Hans Weber observed that human sensory ability to detect change was proportional to the original stimulus. The original stimulus for measuring sight is the 1’ of arc that Robert Hooke posited as good vision. Proportional change can be thought of as changes in letter size as well as dioptric power. Do you see the logarithmic function? Logarithms allow math to be simplified by making proportional change into additive change. Now, since it is easier for human brains to add and subtract rather than to multiply and divide, we can glimpse an avenue to lever the principles of ‘good sight’ that Robert Hooke defined with the rational chart letter sizes and power progression that Weber discovered. It has since been
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