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Are you patients being over minused

By 22.05.2017 No Comments

Habituation to the crispness of 21st century electronic (pixelated) images creates a tendency for patients to fixate on static refraction targets. The subconscious goal is to maximize the contrast between the black and white areas.

That inadvertent examination lane preference for a static refraction overminus is inherent in both myopia and presbyopia. The patient walks out of the doctor’s office with their new glasses, is delighted to read the license plates of cars across the street, but goes home to their computer and starts having visual stress due to the overminus.

The problem with static Snellen target refractions is that we read words rather than letters. Reading letter-based words requires eye movement for both word comprehension and word collaboration in that the meaning of words not only requires cognition but also their association with adjacent words and phrases. The saccade process tries to compensate for the fixation, but the electronic image habituation defeats that saccade process. That fixation habituation is why a Dyop test gives a more precise and consistent acuity and refraction measure.

The refraction overminus can easily be detected by having the patient move their lenses a half inch forward from their eyes while reading text. In about a third of refractions, the words get smaller as the lens spherical power is reduced, but the words also get clearer and more legible. That improved legibility, for both myopes and hyperopes, is evidence that the refraction is overminused.

The Dyop gap/segment strobic stimulus of the photoreceptor minimum stimulus area overcomes that overminus preference. As the the refraction is overplussed or underminused, the diameter of the Dyop needs to be increased.to detect rotation, or the smallest rotation detected Dyop becomes blurrier. The strobic Dyop gap/segment stimulus is the electronic equivalent of the saccade process.

Chart2020

Author Chart2020

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