Course of pattern-reversed visual evoked cortical potentials in 30 eyes after bony orbital decompression in dysthyroid optic neuropathy
Résumé
Aim: To investigate optic nerve function using the pattern-reversed visual evoked potentials (VECP) before and after bony orbital decompression in dysthyroid optic neuropathy (DON) due to Grave´s disease. Methods: A total of 30 eyes of 15 patients (n=14 female) were observed over 30 ± 13 months after bony 3-wall orbital decompression. We examined visual acuity (VA), VECP P100 amplitudes and latencies as well as proptosis using Hertel´s exophthalmometry. Results: Mean logMAR VA increased, statistically significant, by 2.4 lines during 30 ± 13 months (from 0.38 ± 0.25 before surgery to 0.14 ± 0.1 at the end of observation, p=0.0001). All eyes maintained or improved vision by at least one line. Mean postoperative reduction of proptosis was 6.4 ± 3 mm. While VECP P100 amplitudes improved significantly, P100 latencies remained abnormal in 18 eyes (60%) during follow-up of 10 ± 7 months. 9 eyes (30%) with previous latency defects improved in at least one check test, 5 of which normalised completely. Worsening was evident in 7 eyes (23%), 3 previously normal eyes developed new pathologic latencies. P100 latencies in 14 eyes (47%) remained unchanged. Conclusion: After decompression surgery, DON remission was observed in all patients regarding vision and VECP amplitudes. New or persistent P100 latency defects were seen in 60% of eyes after surgery. DON is considered to be caused by compressive ischemic damage which further underlines the importance of early decompression surgery.
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