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Walter Wittich, Olga Overbury, Michael A. Kapusta, Jocelyn Faubert; Procedure- and stimulus-dependent differences in perceptual filling-in after macular hole surgery. Journal of Vision 2005;5(8):297. doi: 10.1167/5.8.297.
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© ARVO (1962-2015); The Authors (2016-present)
Traditionally, perceptual filling-in has been investigated at the optic nerve head as well as with artificial scotomas in the periphery. Research into this phenomenon related to central scotomas remains extremely limited, especially if they occur in the process of ocular disease. Recently, central retinal defects due to Age-Related Macular Degeneration, where scotomas are due to photoreceptor degeneration, have been examined from the perspective of filling-in. The present study took advantage of another ocular pathology, Macular Hole (MH), which results in central field defects due to circular and localized dislocation of photoreceptors in the macula. A surgical procedure (vitrectomy) facilitates closure of the MH, restoring visual function, yet, not always completely. Frequently, patients complain about distortions postoperatively.
Anatomical closure of the MH is clinically assessed with the Watzke-Allen (WA) Test, the projection of a bright white line across the surgical site. The present study investigated the parameters of this test (in 32 eyes) and established guidelines for a standardized version (in 17 eyes). Levels of distortion and perceptual filling-in were examined and compared with a new Line Resolution Test (LRT) in all 49 eyes. The clinically controllable parameters of the WA were line width and luminance. Stimulus display time could only be controlled in the LRT (500 ms) while assessing levels of perceptual filling-in and distortion (solid, bent or broken perception of the line). Overall, line perception on the LRT contradicted the WA in 15 eyes (31%). This disagreement was independent of the type of WA used. The large amount of contradiction in line perception between the two tests can, in part, be attributed to display time in the WA as patients have the opportunity to scan the stimulus. Furthermore, even the standardized WA was displayed at an extremely high level of luminance, facilitating the possibility of perceptual filling-in.
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