Initial models proposed that these operations are weighted sums, with weights given by a neuron’s receptive field. These models explain the basic features of response selectivity. They were later extended to explain a number of suppressive effects originating within and outside the region of the receptive field. The resulting models rely on division. In this division, the receptive field feeds ...

It has been suggested that attentional resolution is greater in the lower than in the upper visual field. As there is no corresponding asymmetry between the areas in the primary visual cortex where the input from upper and lower visual fields is processed, an 'attentional filter' has been proposed to act in one or more higher visual cortical areas in order to constrict the availability of visua...

purpose: to report a case of posterior ischemic optic neuropathy (pion) following percutaneous nephrolithotomy (pcnl). patient and findings: a 57-year-old male who underwent pcnl because of renal stone was referred due to painless bilateral visual loss to the level of light perception immediately after the operation. the patient had history of diabetes mellitus, hyperlipidemia, and mild anemia....

Visual fields were examined with a tangent screen in 54 patients with multiple sclerosis (MS) or optic neuritis (ON). Visual fields were abnormal in all patients with definite MS, 94% with probable MS and 81% with possible MS. Three-quarters of the MS patients with no history of visual symptoms had abnormal fields. The commonest defect found was an arcuate scotoma. As a diagnostic test of visua...

purpose: to report a case of butterfly-shaped macular dystrophy. patient and findings: a 34-year-old woman presented with metamorphopsia in both eyes from 2 years ago. visual acuity was 9/10 in right eye and 10/10 in left eye. there was no pathologic finding on slit lamp biomicroscopy and funduscopy other than mild macular retinal pigment epithelium mottling. visual fields and electroretinogram...