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Nilpa Shah, Steven C. Dakin, Roger Anderson; The Effect of Blur on Detection and Recognition Thresholds Using Vanishing Optotypes in Peripheral Vision. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5515.
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© ARVO (1962-2015); The Authors (2016-present)
Vanishing Optotype letters have a pseudo high-pass design so that the mean luminance of the target is the same as the background and the letters thus ‘vanish’ soon after the resolution threshold is reached in the fovea. Previous studies have demonstrated that this is not the case for peripheral vision. We wished to separately determine the effect of increasing blur on detection and recognition acuity measurements in the periphery using these optotypes.
High contrast letters of both conventional and high-pass ‘Vanishing’ optotype design were presented on a standard CRT monitor. Separate detection and recognition thresholds were determined for all 26 letters at 10 degrees in the horizontal temporal retina of two normal subjectts under increasing amounts of dioptric blur. Five measurements were made in a randomly interleaved order for each letter of the alphabet for each condition.
The mean difference between detection and recognition thresholds for high-pass ‘Vanishing’ optotypes with 0D blur was 0.30 logMAR, but the exact magnitude of this difference varied with the letter in question. Detection and recognition thresholds for these optotypes deteriorated by approximately 0.10 logMAR and 0.07 logMAR respectively for each dioptre of blur, with thresholds converging around +7D blur.
Unlike in the fovea, high-pass ‘Vanishing’ optotypes display significant differences in their detection and resolution thresholds in peripheral vision. In addition, this difference remains with up to +7D blur. This is further evidence for the sampling limited nature of peripheral recognition acuity for these optotypes and thus their potential to detect localized loss of ganglion cells in glaucoma.
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