Perception of tilt following counter-rotation surgery.

Abstract

BACKGROUND: Macular translocation surgery (MTS) is one of the treatment options for age-related macular degeneration (AMD) followed by counter-rotation surgery (CRS) to correct the resulting tilt. The objective of this paper is to determine the perception of tilt following CRS and identify factors that influence the perception of tilt in the presence of residual cyclorotation following CRS. METHODS: Thirty-four AMD patients treated with MTS and CRS were investigated; and all measurements were made preoperatively, and after each surgical procedure. Fundus photographs were analysed with computer software to determine the degree of retinal rotation and reliability was assessed by two independent assessors. The degree of perceptual rotation was measured with Maddox rod and the subjective appreciation of tilt was established by direct questioning. Fixation preference was determined by cover test and convergence. Bagolini glasses were used to determine binocular outcome. RESULTS: Post CRS, 20 of the 34 patients had adapted to tilt. There was a significant difference of 5 degrees +/- 7 degrees (95% confidence intervals: 1-8 degrees , t = 2.9, degree of freedom = 19, P = 0.008) between the degree of rotation measured from the fundus photographs and the Maddox rod measurement following CRS. Patients with residual retinal rotation less than or equal to 15 degrees did not appreciate tilt in free space. More importantly, fixation with the operated eye and ignoring the image from the non-operated eye was significantly associated with being free of tilt in natural viewing conditions (P < 0.05). CONCLUSION: Despite the presence of residual cyclorotation of the macula following CRS of up to 27 degrees , a significant proportion (59%) of patients did not perceive the world as tilted in natural viewing conditions. Differences between retinal rotation and perceptual tilt provide evidence of sensory adaptation. It was patients who fixed with their operated eye and ignored the image from the non-operated eye who did not perceive tilt post CRS.