A new study, published in the November 27, 2012 issue of the online journal Eye and Brain, concludes that saccadic eye movements are significantly delayed in individuals with early, moderate, or advanced glaucoma. Eye and Brain is an international, peer-reviewed, open access journal focusing on clinical and experimental research in the field of neuro-ophthalmology.
About Saccades and Eye Movements
Saccades (pronounced suh-KAHDZ) are a series of rapid, very small movements of both eyes in unison that help us “pick out” the relevant components of an object or a scene to quickly build a three-dimensional visual “map” of our immediate worlds. Saccadic eye movements help us perform a wide range of everyday activities, including reading, scanning grocery store shelves, or evaluating oncoming traffic, for example.
If saccadic eye movements are impaired or delayed, however, it becomes more difficult to create this rapid and necessary three-dimensional view of the environment. Thus, the findings of this study may shed new light on why individuals with glaucoma may be at increased risk for falls or traffic accidents.
The Study Authors
The study, entitled Delayed Saccadic Eye Movements in Glaucoma, was authored by Raageen Kanjee; Yeni H Yücel; Martin J. Steinbach; Esther G González; and Neeru Gupta, who represent the following institutions: St. Michael’s Hospital, University of Toronto; Toronto Western Hospital, University Health Network; and York University.
About the Research
The objective of this prospective study was to determine whether saccadic eye movements were altered in patients with glaucoma. The study participants were 16 patients with glaucoma and 21 control subjects (i.e., individuals who did not have glaucoma).
(Note: A prospective study measures a group of individuals over time and follows up with them in the future. A retrospective study, on the other hand, collects data only from past records and does not follow up with individuals in the present.)
Dr. Gupta and co-authors studied groups of people with and without glaucoma who wore a head-mounted device that measured the length of time it took their eyes to move from one point to another and how long it took their eyes to begin the movement. They also measured whether the subjects focused their eyes on an object right away or overshot the target.
“Most of us take that processing of information for granted,” she said.
[The researchers] found that people with glaucoma demonstrated eye movement reaction times that were 15% slower, even if they were in the early stages of the disease.
Dr. Gupta said the findings are significant because they suggest that approaches to measuring vision loss beyond eye charts or visual field tests that related to real world settings may provide important clues to how the disease affects the lives of glaucoma patients.
“Now that we know that eye movement reaction times are delayed in people with glaucoma, there is an opportunity to understand the effects of glaucoma on daily activities of living that most of us take for granted, such as walking up and down stairs, driving, navigating, and reading,” Dr. Gupta said.
“Just as alcohol causes a delay in hitting the brakes, glaucoma slows the time it takes to move the eyes quickly in response to a visual cue.”
Glaucoma is a group of eye diseases that damage the optic nerve and is one of the leading causes of vision loss and blindness.
Glaucoma results in peripheral (or side) vision loss initially, and the effect can be like looking through a tube or into a narrow tunnel. This “tunnel vision” effect makes it difficult to walk without bumping into objects that are off to the side, near the head, or at foot level. It is an especially dangerous eye condition because most people do not experience any symptoms or early warning signs at the onset of glaucoma.
Glaucoma can be treated, but it is not curable. The damage to the optic nerve from glaucoma cannot be reversed. However, lowering the pressure in the eye can prevent further damage to the optic nerve and further peripheral vision loss. Early detection, therefore, along with appropriate and ongoing treatment, is critical.
The Study Conclusions
The study authors concluded that:
Saccadic eye movements are significantly delayed in patients with early, moderate, or advanced glaucoma.
Determination of … saccade reaction time may offer a novel functional test to [measure] visual function in glaucoma patients. Further studies are needed to determine [the disease processes that cause] delayed … saccades, and to assess whether the alteration of saccades affects daily activities in glaucoma patients.
VisionAware will provide updates of this important research as they become available.