HAND-HELD DEVICE REVEALS MACULAR ACUITY
AND PREDICTS POST-OPERATIVE VISION
WHEN THE MACULA CAN NOT BE SEEN
By John Karickhoff, M.D.
Doctors can easily examine the cornea, the lens, and the vitreous to learn if there is the clarity to allow good vision. However, learning the potential visual acuity of the macula when the cornea, lens, or vitreous is cloudy is presently impossible because the doctor (a) can’t see the macula adequately pre-operatively and (b) the cloudy cornea, lens, or vitreous blocks the macula from viewing the visual testing chart on the wall. To solve this impossibility, we are proposing using the blue-field entoptic test.
The blue-field entoptic phenomenon was first described in 1924 by Richard Scheerer. It consisted of using an electric light in a box as a projector to shine through a very pure blue light pass-filter into the eye of the patient. There the blue light was absorbed by the red blood cells in the micro-vessels of perifoveal area of the macula, but the light was not absorbed by the white blood cells. This created what appeared to the patient as about 50 tiny white lights each moving for about one second in its curved pattern and all lights pulsating when the patient’s heart beat.
We have studied this blue field entoptic phenomenon for 30 years and have learned or done six things with the test.
(1) We learned clinically that if the patient sees their retinal white blood cells in their perifoveal area, their macular acuity is 20/40 or better, which, by happy coincidence, is level of vision commonly used as the standard of surgical success.
(2) We learned that this test is independent of the presence of a cataract, vitreous or corneal haze as long as one gets some pure blue light to the retina.
(3) We learned that the test worked when the cornea, lens, or vitreous opacities were dense enough to prevent reading any conventional wall chart. This is possible because in this test, both the visual receptors and the visual target are adjacent in the retina, not one on the wall.
(4) We adapted the blue-field entoptic test from using the light in the box as the projector to using the slit lamp as the light projector. This was accomplished by simply placing the filter on a handle. This adaptation made the test less expensive, no table space was used, the patient did not have to be moved from the slit lamp to the box, and the test could be done in 10 seconds.
(5) We performed a 10-month clinical study to learn the accuracy of the test in predicting post-operative vision.
(6) We worked with a manufacturer and made this test commercially available.
The diagram shows how the test works: the bright, white light of the slit lamp shines through the proprietary filter which has the proper optical frequency bandpass, the proper band-width, diameter, and optical density so as to get adequate light to the retina but not to dazzle the patient. The blue light coming out of the filter into the patient’s eye, lights up their perifoveal white blood cells. This display is dramatic and unique for any viewer.