Neil Young on the old. What else is new? What’s new is old, and now even neuroplasticity is seemingly being recycled. Presbyopia literally means old vision. But is the opia in the eyes or in the brain? We’ve asked this question of other opias, most notably amblyopia.
I’ve blogged before about Gabor patches and the evolution of Neurovision into Revitalvision and the potential benefits of what is essentially contrast sensitivity and crowding training as nouveau perceptual learning paradigms. Revitalvision has the approach of trying to improve near focus in presbyopia to lessen the dependency on reading glasses. (Parenthetically it’s interesting to see Ophthalmology struggle with how to fit such “therapy” into its clinical model of presbyopia, particularly with regard to accommodation function after IOL implantation.)
Enter Uri Polat and Dennis Levi, the researchers responsible for the science behind Neurovision and perceptual learning. Like good musicians jamming they have found each other again and have formed a new super group to go after presbyopia. This began in earnest with Polat’s paper in Vision Research in 2009, proceeding to a super group presentation at ARVO last year: Polat U, Sterkin A, Yehezkel O, Lev M, Zomet A, Schor C, Levi D. Perceptual Training Overcomes the Optical Limits of Presbyopia. Sterkin, Yehezkel, Lev, and Zomat are members of the Polat Lab, and as you can see, they’ve been joined by Clif Schor who, like Levi, is a prolific researcher at UC Berkeley.
Their ARVO paper has now been published in Nature, Scientific Reports (2012) under the title: Training the brain to overcome the effect of aging on the human eye. Here are some key results:
(a) Near visual acuity before (abscissa) and after (ordinate) perceptual learning (PL). Solid symbols are presbyopic subjects (median age 51). Open symbols are the no PL control group. The dotted gray line is the quality line. The solid gray diagonal is a power function fit to the presbyopes data. The horizontal and vertical lines show typical newsprint size (expressed in minutes of arc). (b) Near visual acuity vs. age before (blue) and after (red) PL. The large blue and red circles show the geometric mean acuities before and after PL, plotted at the corresponding pre-training abscissa values (shown by the arrows). (c) Reading speed before (abscissa) and after (ordinate) PL for the smallest letter size that each subject could read.
So here’s the deal: The Nature article shows promise that perceptual learning through improved contrast discrimination may improve visual acuity and reading speed in presbyopia. Though the authors note that their results would have to be replicated in a larger scale study with better controls, it is the first report of its kind to document that these changes occurred without any measurable change in accommodation, pupil size or depth of focus. This clearly turns the optics of classical optometry and ophthalmology on its head, for if there are changes in presbyopic focus and function occurring beyond the pupil and crystalline lens, where do these changes occur? Ah yes, – the brain thing. Looks like optometrists like John Streff and Harry Wachs knew what they were talking about after all. 😉