Spatial interactions in amblyopia: effects of stimulus parameters and amblyopia type.

Adults with amblyopia were recently shown to perform abnormally in tasks requiring integration of local features into global percepts. Moreover, spatial interactions in amblyopic patients, though often found to be abnormal, showed marked variability. Here we measured collinear lateral interactions using Gabor patches in a large number of amblyopic (N=75) and normal subjects (N=25), testing four spatial frequencies (1.5, 3, 6, 9 cpd). We used the lateral masking paradigm, in which the contrast-detection threshold is measured in the presence of high-contrast flankers at different distances from a central target. Whereas in normal subjects spatial interaction patterns were evident across all spatial frequencies, amblyopic subjects showed abnormal spatial interactions and increasing deficiencies with increasing spatial frequencies. These abnormalities depended on the axis of astigmatism (in meridional amblyopia) and were more pronounced in strabismic than in anisometropic amblyopia. Spatial interactions were independent on the contrast-detection thresholds. Thus, adults with amblyopia might perform as well as normal observers for some stimulus parameters and abnormally for others. Our results indicate a close relationship between abnormal visual input to the visual cortex during development and abnormal functionality of the collinear spatial interactions in adults with amblyopia.

Early postoperative intraocular pressure pattern in glaucomatous and nonglaucomatous patients.

PURPOSE: To evaluate intraocular pressure (IOP) changes in the 24 hours following cataract extraction in glaucomatous and nonglaucomatous patients. SETTING: General Eye Service and Glaucoma Service of the Goldschleger Eye Institute, Tel Hashomer, Israel. METHODS: Twenty-six nonglaucomatous patients and 13 glaucomatous patients scheduled for routine cataract extraction and intraocular lens implantation were evaluated. In each patient, IOP was measured before cataract surgery and every 4 hours for 24 hours postoperatively. Thirteen of the nonglaucomatous patients were randomly treated with one drop of timolol maleate at the end of surgery (NG-T group). The other 13 nonglaucomatous patients (NG group) and all glaucoma patients (G group) were not treated. RESULTS: In the NG group, mean preoperative IOP was 13.9 mm Hg. Following surgery, IOP rose steadily to 22.2 mm Hg at 12 hours; it returned to almost presurgical levels at 24 hours. The IOP exceeded 35 mm Hg in only one patient. In the NG-T group, mean preoperative IOP was 16.5 mm Hg and increased to 21.2 mm Hg at 12 hours. The IOP returned to almost presurgical levels at 24 hours. In the G group, mean IOP was 18.8 mm Hg preoperatively and rose to 29.9 mm Hg at 8 hours after surgery. In seven eyes the IOP exceeded 35 mm Hg. COMMENTS: Our findings of elevated IOP emphasize the need for prophylactic treatment (medical or combined cataract and glaucoma surgery) to prevent IOP spikes in high-risk patients.