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Mehmet N. Ağaoğlu; Susana T. L. Chung

Exploration of the functional consequences of fixational eye movements in the absence of a fovea

publication date
February 2020
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A recent theory posits that ocular drifts of fixational eye movements serve to reformat the visual input of natural images, so that the power of the input image is equalized across a range of spatial frequencies. This “spectral whitening” effect is postulated to improve the processing of high-spatial-frequency information and requires normal fixational eye movements. Given that people with macular disease exhibit abnormal fixational eye movements, do they also exhibit spectral whitening? To answer this question, we computed the power spectral density of movies of natural images translated in space and time according to the fixational eye movements (thus simulating the retinal input) of a group of observers with long-standing bilateral macular disease. Just as for people with normal vision, the power of the retinal input at low spatial frequencies was lower than that based on the 1/f2 relationship, demonstrating spectral whitening. However, the amount of whitening was much less for observers with macular disease when compared with age-matched controls with normal vision. A mediation analysis showed that the eccentricity of the preferred retinal locus adopted by these observers and the characteristics of ocular drifts are important factors limiting the amount of whitening. Finally, we did not find a normal aging effect on spectral whitening. Although these findings alone cannot form a causal link between macular disease and spectral properties of eye movements, they suggest novel potential means of modifying the characteristics of fixational eye movements, which may in turn improve functional vision for people with macular disease.


Despite their abnormal characteristics, fixational eye movements exhibited by people with macular disease also demonstrate spectral whitening, although the magnitude of whitening is less (and is limited to lower spatial frequencies) than that observed in people with normal vision. The less-than-normal whitening should not be interpreted as indicating that the benefits of fixational eye movements, especially those due to ocular drifts, are smaller for people with macular disease. Rather, it just means that spectral whitening occurs for a range of spatial frequencies lower than that for normal vision, which is reasonable given that people with macular disease must rely on their peripheral retina for vision. Using a mediation analysis, we found that the eccentricity of the PRL adopted by these observers and the diffusion constant of ocular drifts are the important factors limiting the amount of whitening. These findings offer novel potential means of improving the characteristics of fixational eye movements, which may, in turn, improve functional vision for people with macular disease. Finally, we did not find a normal aging effect on spectral whitening.


Vision therapy is well worth the response, time and effort. Our Son had a hard time focusing and writing neatly. After vision therapy Seth could complete a task in half the time if previously took. His abilities to focus improved greatly and so did his handwriting.

Also, he was better at listening. As a parent, we wanted learning to be fun for our Son, and vision therapy made this possible.

Amanda T.

Vision Therapy is well worth the expense, time and effort. Our son had a hard time focusing handwriting neatly. After vision therapy Seth could complete a task in half the time it previously took his abilities to focus and improved greatly and so did his handwriting.

Also, he was better at listening. As a parent you wanted learning to be fun for our son and vision therapy made this possible.

Alexa H.

Vision Therapy has given or son the tools he needs to be able to scan and read the written word more effectively and efficiently.

He love working with John and these working sessions give him the motivation to gladly work on his homework assignments.

It amazed us to see the difference in the tracking of his eyes and along a line of it's from the beginning to the end of the treatment.

Dr. McBryar , Kristen and John  are all marvelous and we would recommend them to anyone I only wish that we would have found them sooner!

Charlotte M.

Prior to coming to the institute for vision development my son complained of daily headaches. Therapy has eliminated his headaches completely. I love knowing my son is able to learn pain-free for the rest of his life because of the work that has been done over just a few weeks in this office. He he absolutely loved coming that didn't even feel like going to a doctor or therapy. We are grateful for the relief he was able to find by coming here.

Thank you!

Olivia C.

Seems much less frustrated with life

Reads non-stop and fast

Spelling abilities have been hugely improved

Seems much more confident

Thank You!!!

Kelly O.

When we first came to the practice, my son did not have huge issues, but lots of small ones- trouble with reading, sports (hitting the baseball consistently), coordination, etc- that were not easily detectable,but when put together presented issues. The staff here were all very professional and loving towards him. While I was concerned in the reading, my son was concerned with the athletic side. Seeing improvement night off the bat gave him confidence that i have nor seen in him and made him want to not only Come to therapy, but also made him want to work hard. He has surpassed his grade level and above in reading and hit his first home run this year! Thank you!!!

Alice M.
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