Human Eye Movements for Vision Are Remarkably Adaptable

Our eyes are constantly on the move, darting this way and that four to five times per second. Our eyes have the ability to change direction and focus at an incredible speed. 

A new study published in the Cell Press journal Current Biology on August 15, states that researchers have found that the precise manner of those eye movements can change within a matter of hours. This discovery might lead to a way to help those with macular degeneration better cope with vision loss.

“The system that controls how the eyes move is far more malleable than the literature has suggested,” says Bosco Tjan of the University of Southern California. “We showed that people with normal vision can quickly adjust to a temporary occlusion of their foveal vision by adapting a consistent point in their peripheral vision as their new point of gaze.”

The fovea is the small, center-most portion of the retina, which is responsible for our Eye Charthigh-resolution vision. In other words, it is the “pointer” we use to direct our eyes to different parts of a scene, building an image of our world. For those with age-related macular degeneration, increasing loss of foveal vision leads to visual impairment and blindness.

The researchers simulated a loss of foveal vision in six normally sighted young adults by blocking part of a visual scene with a gray disc that followed the individuals’ eye gaze. Once the disc was in place, the individuals were asked to complete demanding object-following and visual-search tasks.  The researchers found that within three hours of working on those tasks, all six participants showed a remarkably fast and spontaneous adjustment of eye movements. Once the visual adjustment had been made by the participants, the change in their “point of gaze” was retained for a period of weeks and was reengaged whenever their foveal vision was blocked.

Tjan and the other two researchers stated they were surprised by the rate of this adjustment. They note that patients with macular degeneration frequently do adapt their point of gaze, but in a process that takes months, not days or hours. They suggest that practice with a visible gray disc like the one used in the study might help speed that process of visual rehabilitation along. The discovery also reveals that the oculomotor (eye movement) system prefers control simplicity over optimality.  Tjan states “Gaze control by the oculomotor system, although highly automatic, is malleable in the same sense that motor control of the limbs is malleable.”

The result of this study is potentially very good news for people who experience loss of their foveal vision due to macular diseases. This study shows that it may be possible to create the right conditions for the oculomotor system to quickly adjust.

To read the original article, visit: https://www.sciencedaily.com/releases/2013/08/130815133447.htm

Does Low Birth Weight = Age-related Vision Loss?

A recent study suggests doctors may need to pay close attention to vision concerns in patients born with a low birth weight.

Medical researchers at the University of Alberta recently published findings of their study on rats with restricted growth in the womb, causing them to be born with low birth weights.  The study showed those rats were most susceptible to developing age-related vision loss, compared with rats born within the normal range of birth weight.

Additional work needs to be done to see whether this same link exists in people. If it does, doctors will need to incorporate better vision monitoring in adults who were born with a low birth weight.

Although most age-related eye diseases or vision loss can result from many different factors, this study may indicate that low birth weight could be an additional factor to consider.

The low birth weight rats in the study had overall poorer vision as they aged, they also had poorer night vision.  While it is normal for night vision to be slightly affected with age, the night vision loss was worse than normal in the test subjects as they aged.

Now all of this begs the question: How do they know what a rat can or cannot see and the degree of the difference??

Read more: https://www.healthcanal.com/eyes-vision/39986-low-birth-weight-may-be-risk-factor-for-age-related-vision-loss.html