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(Investigative Ophthalmology and Visual Science. 2006;47:3695-3702.)
© 2006 by The Association for Research in Vision and Ophthalmology, Inc.
DOI:  10.1167/iovs.05-1569
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Altered Visual Sensitivity in Axial High Myopia: A Local Postreceptoral Phenomenon?

Alexandra Jaworski, Alex Gentle, Andrew J. Zele, Algis J. Vingrys, and Neville A. McBrien

From the Department of Optometry and Vision Sciences, The University of Melbourne, Victoria, Australia.

PURPOSE. The present study investigated retinal integrity in high myopia using spatial psychophysical tasks.

METHODS. Ten axial high myopes (–8.5 to –11.5 D) and 10 age-matched control subjects (±1.0 D) were recruited. All participants underwent clinical examination and ocular biometry and demonstrated no visible macular disease with visual acuities better than 6/12. Foveal summation thresholds were determined for white and S-cone-isolating spots of various diameters up to 5.4° and spatial contrast sensitivity to luminance sine wave gratings (0.5–9.7 cyc/deg). Data were analyzed after correction for the magnification induced by eye size and correcting lens power.

RESULTS. Spatial summation for both white and S-cone-isolating spots showed a generalized loss of sensitivity at all spot sizes in myopes relative to control subjects (P = 0.01). Critical areas at maximum summation were significantly larger in myopes, for S-cone isolating spots only, after image size correction (P = 0.048). Sensitivity at maximum summation correlated negatively with vitreous chamber depth for both targets (P = 0.005). Sensitivities for S-cone and luminance spots also correlated (P < 0.001), indicating widespread dysfunction. Myopes displayed contrast sensitivity losses at high spatial frequencies (P ≤ 0.006) with a normal peak contrast sensitivity.

CONCLUSIONS. These data can be interpreted to indicate that highly myopic eyes have either (1) a reduction in the number of receptors and/or a reduction in their sensitivity or, (2) a reduction in the sensitivity of postreceptoral processes. The presence of normal contrast sensitivity at low spatial frequencies indicates dysfunction at a postreceptoral level in high myopes.






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Copyright © 2006 by the Association for Research in Vision and Ophthalmology