Blur adaptation in myopes.

It has been suggested that when subjects with myopia remove their refractive correction, blur adaptation develops to produce an improvement in their visual resolution. The present study measured visual acuity (VA) using high contrast letters and gratings with contrast levels between 2.5% and 40% at 30-minute intervals over the course of a 3-h period during which the subjects remained uncorrected. Twenty-two young subjects with moderate degrees of myopia (mean refractive error, -185 D) participated in the study. Immediately after a 1-h period of full correction, subjects spent 3 h without any refractive correction, during which time they watched television and videos at a viewing distance of 5 m. A significant change in letter and grating VA was observed during the course of the 3-h period of sustained blur, with the mean uncorrected letter VA improving from 0.76 (SD, +/-0.26) to 0.53 (SD, +/-0.23) logarithm of the minimum angle of resolution (logMAR). The Snellen equivalent to this change is from 6/35 to 6/20. A significant improvement in grating acuity was also observed. However, no significant change in refractive error, measured using noncycloplegic autorefraction, was found. These results demonstrate significant blur adaptation in subjects with uncorrected myopia, which does not result from a change in refractive state. We hypothesize that the improvement in visual resolution results from perceptual adaptation to the blurred image, which may occur at central sites within the visual cortex.

An autosomal recessive form of bilateral frontoparietal polymicrogyria maps to chromosome 16q12.2-21.

Polymicrogyria is a cerebral cortical malformation that is grossly characterized by excessive cortical folding and microscopically characterized by abnormal cortical layering. Although polymicrogyria appears to have one or more genetic causes, no polymicrogyria loci have been identified. Here we describe the clinical and radiographic features of a new genetic form of polymicrogyria and localize the responsible gene. We studied two consanguineous Palestinian pedigrees with an autosomal recessive form of bilateral frontoparietal polymicrogyria (BFPP), using linkage analysis. Five affected children had moderate-to-severe mental retardation, developmental delay, and esotropia, and four of the five affected children developed seizures. Brain magnetic-resonance imaging revealed polymicrogyria that was most prominent in the frontal and parietal lobes but involved other cortical areas as well. A genomewide linkage screen revealed a single locus that was identical by descent in affected children in both families and showed a single disease-associated haplotype, suggesting a common founder mutation. The locus for BFPP maps to chromosome 16q12.2-21, with a minimal interval of 17 cM. For D16S514, the maximal pooled two-point LOD score was 3.98, and the maximal multipoint LOD score was 4.57. This study provides the first genetic evidence that BFPP is an autosomal recessive disorder and serves as a starting point for the identification of the responsible gene.