Observer variation in quantitative assessment of retinal shortening with ultrasound in patients of total rhegmatogenous retinal detachment.

Purpose: To evaluate the interobserver variation in the assessment of retinal length to choroidal length ratio (RCR) as a marker for proliferative vitreoretinopathy (PVR) in cases of rhegmatogenous retinal detachment (RRD). Methods: This was a double-masked, prospective study at a tertiary center. Ultrasound was used to calculate RCR in 50 eyes with total RRD by two observers. Both observers were trained after the first round of calculations, and all the calculations were repeated as before. Difference between the RCR values was stratified into four categories (<0.01, 0.01-0.05, 0.06-0.1, and >0.1) for descriptive analysis. A difference of 0.05 was set as the maximal limit for defining interobserver agreement. Correlation between RCR and interobserver difference was assessed. Results: The mean interobserver difference in RCR values was found to be 0.06 ± 0.0 (P = 0.41) and was reduced to 0.04 ± 0.02 (P = 0.81) following training. The interobserver difference was <0.1 in 82% of the cases before training and in 98% of cases after training. The worst interobserver agreement was noted in cases with RCR < 0.8, and there was a good negative correlation between RCR and interobserver difference (r = -0.6, P ≤ 0.001). Conclusion: There is good interobserver agreement in assessing RCR with ultrasound in eyes with RRD, which improves further with training. RCR needs careful assessment in eyes with very low RCR. This technique may be useful in prognostication of surgical outcomes in cases with advanced PVR.