A world of experience in retinal image quality
Good visual acuity does not always reflect a good visual image
Leigh Spielberg
Published: Saturday, February 11, 2017
Raymond Applegate[/caption]
Retinal image quality was the topic presented by Raymond Applegate OD, PhD, Houston, USA, to delegates attending the Basic Optics Course at the 21st ESCRS Winter Meeting in Maastricht, The Netherlands.
“Retinal image quality is not equivalent to visual image quality, as there are several processes involved between the retina and the actual perception of the image,” said Dr Applegate. These include sampling by the photoreceptors, neural processing and visual perception, the so-called mind’s eye.
“You have a world of experience in your head, and this largely determines what you perceive. Visual performance is dependent not only on retinal image quality, but also on the neural systems which process the retinal image,” he said.
The problem is further complicated by the fact that ‘good’ visual acuity does not always reflect a good visual image.
“After all, there are six noticeable differences in retinal image quality in just one line of visual acuity. These make the difference between 20/20 happy patients and 20/20 unhappy patients,” said Dr Applegate.
There are six noticeable differences in retinal image quality in just one line of visual acuityHe stressed that visual acuity is in fact a poor performance metric. “It is therefore not surprising that cross-sectional studies correlating measures of retinal image quality and visual performance have been only moderately impressive,” he pointed out. So what connects the two? “The visual Strehl and neural strength tests are excellent metrics of visual image quality that are highly correlated with visual performance as measured by acuity,” explained Dr Applegate, suggesting that clinical investigators focus on these metrics.