Dynamics of visual improvement following chiasmal decompression. Quantitative pre- and postoperative observations.

Purpose: To study early visual restoration following surgical removal of pituitary adenomas compressing the optic chiasm.

Methods: Eleven patients were examined with high-pass resolution perimetry (HRP) before and after trans-sphenoidal adenomectomy. Visual fields were examined on the second postoperative day. The result was interpreted in terms of the estimated fraction of functioning retino-cortical connections.

Results: In the upper and lower temporal visual field quadrants, the mean increases in the fraction of functioning neural channels were 19% (p < 0.001) and 17% (p = 0.001), respectively, on day 2 after surgery. These increased to 35% on day 12. The nasal hemifield showed no change on day 2, but functioning neural channels had increased by 15% on day 5 (p = 0.017). Mean visual acuity improved from 0.6 preoperatively to 1.0 on day 2 (p = 0.030) but did not change significantly thereafter.

Conclusion: All visual field sectors and visual acuity improved after surgery. Improvement starting in the temporal hemifield was already evident on the second postoperative day.