Purpose: Some patients with unilateral idiopathic epiretinal membrane (U-ERM) experience metamorphopsia under binocular vision. This study evaluated the efficacy of vitrectomy and characteristics of metamorphopsia under binocular vision in such patients.
Patients and methods: From December 2019 to April 2022,40 patients with U-ERM who underwent vitrectomy at the Department of Ophthalmology, Tokyo Medical University Hospital, were classified into two groups based on the presence or absence of metamorphopsia under binocular vision. The visual function was compared between the two groups. In the metamorphopsia (+) group, the visual function was evaluated 6 months after vitrectomy. The test items included the amount of metamorphopsia in both horizontal and vertical meridians, mean value of the two amounts measured using M-CHARTS™, and stereoscopic parallax measured using the Titmus Stereo Test. The dominant eye was identified via the hole-in-card prior to vitrectomy.
Results: Twelve patients (30%) were classified into the metamorphopsia (+) group. The mean amount of metamorphopsia in the affected eyes of the metamorphopsia (+) group was 1.45° (median), which was significantly higher than that (0.60°) of the metamorphopsia (-) group (p< 0.001). The cutoff value was 1.15° (p< 0.0001, area under the curve [AUC]: 0.90, sensitivity: 83%, specificity: 86%). In nine patients who did not experience metamorphopsia under binocular vision despite having a high mean amount of metamorphopsia in the affected eye (≥1.0°), the proportion of patients whose dominant eye remained unaffected was significantly higher (eight cases, 89%, p< 0.05). In the metamorphopsia (+) group, the mean amount of metamorphopsia under binocular vision significantly decreased from 0.25° (median) before vitrectomy to 0°after vitrectomy (p< 0.05). In seven cases (58%), metamorphopsia under binocular vision disappeared, and stereoscopic parallax improved from 200" before vitrectomy to 100" after vitrectomy (p< 0.05).
Conclusions: Patients with U-ERM who have severe metamorphopsia may experience metamorphopsia even under binocular vision. This study revealed that vitrectomy reduced metamorphopsia under binocular vision and improved stereopsis in such patients.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 128: 320-325,2024.