Abstract
Purpose: :
Lesions affecting the visual pathway from the optic tract to the occipital lobe can produce a homonymous hemianopia (HH). A dictum in neuro-ophthalmology is that the lesion location can be predicted by comparing the shape/form of the nasal and temporal components of the HH. This dictum which originated from kinetic perimetry testing stated that more congruous HHs arise from lesions at or close to the occipital lobe. Since automated static perimetry is the gold standard of perimetry, we sought to know if differences in mean deviation (MD) density, arising from asymmetry of the nasal and temporal components of the HH, could be predictive of lesion location.
Methods: :
The MD threshold sensitivity was examined from 178 patients with HHs. The MD of the eye with the nasal visual field defect was compared with the fellow eye with temporal visual field defect, with respect to clinical and radiologic location of the lesion, cause of the injury, age and gender. .
Results: :
The mean (± standard deviation) of the eye with the nasal component of the HH was -10.9 (± 7.5) dB, and -13.3 (±7.2) dB for the eye with the temporal component. A lack of a nasal-temporal disparity of greater than 1 decibel was identified in only 17 (9.5%) of the 178 HHs. There was no consistent pattern in the etiology or anatomical location in patients having a nasal-temporal disparity.
Conclusions: :
Disparity in the MD density on automated static perimetry does not help to localize the lesion causing a HH.
Keywords: visual fields • neuro-ophthalmology: diagnosis