Comment on: Evaluation of retinal nerve fiber layer thickness after optic canal decompression.

Sir,

We read with interest the article by Bhattacharjee et al.[1] The improvement in visual parameters of patients is interesting to observe. However, we would like to discuss a few points which might be of importance to readers.

The two cases reported are essentially different in their time of presentation, 6 weeks in case 1 and 6 days in case 2. Hence, it may be presumed that case 1 supposedly must have had a more significant retinal nerve fiber layer (RNFL) damage as compared to case 2. The percentage change in RNFL after surgery in case 1 is not expected to be significant, although apparent changes may have been observed by the authors. However, because the authors have not mentioned raw data, the amount of improvement is unclear. In addition, because maximum RNFL reduction happens at 6 weeks, it is highly improbable to obtain a significant thinning of the optic nerve after just 6 post trauma (case 2).

Further, the signal strength of the left eye preoperative optical coherence tomographyin case 2 was 3/10, which rendered the data unreliable. Average RNFL thickness was seen to reduce from 90 μm to 84 μm, which is against the hypothesis suggested by the authors. After extensive literature search, we could not find any longitudinal study which has evaluated the change of RNFL after optic canal decompression. However, one long-term study evaluating RNFL thickness after chiasmal decompression in 20 patients showed significant reduction in RNFL even at 3 months after surgery, with a 2.82% improvement at 6 months.[2] However, a net thinning was still observed from the baseline. Hence, we feel it is premature to comment on the effect of optic canal decompression on RNFL thickness based on these observations.

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