Welcome to 2019! It’s safe to predict that the ophthalmic market will begin planning catchy slogans for 2020 sometime during the course of this year. That also presents the opportunity to redouble our efforts regarding the significance of vision beyond 20/20.
It’s a tradition on New Year’s Eve to sing Auld Lang Syne, a Scottish phrase which literally means “Old Long Since” or for old time’s sake.
So it seems appropriate at this time to reach back for something old to inform something new, regarding vision beyond 20/20. Having recently begun a consulting practice in an area that places a high premium on vision and learning in general, and in reading visually challenging text in particular, the topic of prescribing prism has resurfaced with a vengeance. I use that term here for it’s definition as something that occurs with great force or effect. It is in this spirt that we’ll discuss something old and something new regarding the detection of subtle yet very significant binocular misalignments or instabilities.
For old time’s sake, a slide that remains very useful is part of the Bernell 553 light box series as pictured below.
This polarized slide is highly useful for its dedicated horizontal and vertical fixation disparity targets, as well as the opportunity to balance accommodative responses at near for the right and left eyes under binocular conditions.
For something new, I’ve found great utility in the numerous binocular vision features that are part of the smart screen from DMD Med Tech. It is distributed by Burton Ophthalmic as the ClearVue II Acuity Panel, which is a bit of a misnomer. Originally introduced as electronic visual acuity charts, smart screen computerized devices have become increasingly sophisticated in incorporating fusion, fixation disparity, and stereoscopic targets. The charts are available in polarized or anaglyphic mode.
A couple of brief examples:
- The familiar Mallet Test from England for fixation disparity
2. The Differentiated Stereo Test the progresses from 5 minutes of arc down to 10 seconds of arc with reversible convergent or divergent disparity.
3. Random Dot Stereopsis targets ranging in disparity from 206 seconds of arc to 55 seconds of arc when viewed from 30 to 50 centimeters, some with multiple levels of disparity within the same field.
The bottom line is that many of the visual stimuli now available through either low tech or hi tech systems can be adapted to probe how well lenses and prisms are enhancing binocular balance, improving binocular stability, and translating to improved stereoscopic localization.