BRAIN SPECT EVALUATION OF THE VISUAL-CORTEX IN AMBLYOPIA

In amblyopia, the number of visual cortical neurons are reduced and ab normal or absent sensitivity to retinal light stimulation of the ambly opic eye is demonstrated. Ten amblyopic patients were studied to evalu ate the response of the visual cortex to visual stimulation. Methods: All patients with unilateral amblyopia received 500-550 MBq (TC)-T-99m -HMPAO during Visual stimulation. Strobe light flashing was used as th e stimulus for five patients and a checkerboard pattern reversal was u sed in the other five patients, closing one eye. For both groups a 2-H z frequency was used. One week later, the same procedure was repeated with the opposite eye closed. SPECT images were reconstructed with pre filtering techniques and sliced along the orbitomeatal line. Results: For all patients, the amblyopic eye demonstrated less radioactivity in the visual cortex than in the normal eye. The mean cerebral-to-cerebe llar ratios were 0.95 +/- 0.05 and 1.09 +/- 0.07 for amblyopic and nor mal eyes, respectively (p < 0.0001). Conclusion: Visual cortex respons e of the amblyopic eye to light stimulation was severely reduced when compared to the normal eye.