Stargardt Macular Dystrophy: Changes in Fixation When Asked to Look Straight Ahead
When central vision is lost due to Stargardt Macular Dystrophy, a person commonly uses a new location in their healthy peripheral retinas for fixation of objects. We explored whether this new peripheral location or the original, diseased location of the fovea (the area in the center of the retina that we use for best acuity) is used as the perceptual center of the visual world. Using microperimetery, fixation was measured under two different instructions: “look at the cross” and “look straight ahead, even if you do not see the cross”. If a person fixates using the diseased, non-seeing fovea with the instruction to “look straight ahead,” spatial representation of the visual world has not been re-mapped to the peripheral retina.
We found that peripheral locations were predominantly used to fixate under the viewing condition “look at the cross”. However, when asked to “look straight ahead,” 89% of the eyes had fixations at, or close to the fovea. That is, despite using peripheral retina to see the fixation target, most people did not think of these location as the center of their visual world. This finding emphasized that reliable assessment of visual function during evaluations of disease progression or in therapeutic intervention trials requires consistent instructions and monitoring of fixation.
“Stargardt Macular Dystrophy: Changes in Fixation When Asked to Look Straight Ahead”. Published in Ophthalmology Retina. Mary Lou Jackson, MD, William Seiple*, PhD (2017). Vol. 1 Issue 6, Nov. – Dec. 2017, pp 524-530.
*William Seiple, PhD, is Vice President of Research at Lighthouse Guild.