Effect of visual field defect on stereopsis: In cases with lesions of optic chiasm and macular hole

Stereopsis in patients with lesions of the optic chiasm and unilateral macular hole was evaluated using the Titmus stereo test (Titmus) and Lang stereo I test (Lang). The difficulty with stereopsis in patients with optic chasmal lesions is most likely caused by the compression of the decussating optic nerve fibers resulting in the loss of an overlapping visual field at the fixation point. Conflicting results regarding the binocular visual field test (starlight test) in monocular and binocular conditions needs further investigation. In monocular testing, essentially normal stripes were observed in each eye but in binocular testing, stripes, which were projected upon the nasal retina were suppressed bilaterally (bitemporal hemianopsia). In 20 cases of unilateral macular hole, preoperatively the results of the Lang were better than the Titmus circle in the same stereo disparity of 800″ (0.22°). This discrepancy depends on the size of the stimulus of 2 charts; each circle in Titmus subtends 0.7° at fovea and falls within the affected hole (average maximum diameter was 1.7°), but the Lang projects normal parafoveal regions. Postoperatively, patients obtained better results in the circle test. They were also able to perceive Haidinger brush, which is visible to individuals with normal maculae.