The Nonlinearity of Optometric Data

What are the visual metrics in Opto-metry?  What were the “formulas” they taught you in school as related to visual analysis?  Chances are they revolved around linear equations such as calculating dioptric demands, Snellen equivalents, AC/A ratios, etc.  Graphical analysis is an almost defunct system of linearity, pre-deceased by checking, chaining, and case-typing as a way of labeling data.  Fixation disparity profiles through curve types got a bit closer to the nonlinearity of data.


Although purists might argue that FD still has linear properties – simply curvilinear instead of rectilinear – it was a way of representing emergent visual profiles that began to get closer to the heart of the nonlinear profiles that most of our patients exhibit.

Engineering plant diagrams were attractive and helpful, but rooted again in linearity.

Plant Diagram

Begin to think more deeply about the numbers you collect on patients, and how that does or does not relate satisfactorily to their visual performance.  More importantly, think about the boxes into which we pack this data, and how suitably that serves your clinical purposes.

4 thoughts on “The Nonlinearity of Optometric Data

  1. Excellent Len. I often tell students and vision therapists that variations or instability in the visual system have more diagnostic value than hard numbers.

  2. This underlies the difficulties with communicating people within the eye care sphere, particularly with who do not routinely assess binocular vision and accommodation beyond some fairly rudimentary tests. Nice post.

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