We want to congratulate Lim and Na for their study entitled, “A comparative study between intravitreal triamcinolone and bevacizumab for macular edema due to central retinal vein occlusion with poor vision.” Briefly, the authors reported that intravitreal bevacizumab and intravitreal triamcinolone were associated with a reduction in macular edema; however, neither treatment achieved significant visual acuity improvement by the 12-month follow-up.
The authors reported that macular thickness reduced from a baseline of 713.6 ± 179.3 μm to 310.8 ± 205.2 μm (P < 0.001). The reduction in macular thickness did not differ between the treatment groups (P = 0.324). Significant central macular thickness reduction, but insignificant visual acuity change (P = 0.673), suggests irreversible macular damage due to macular edema. The duration of the macular edema is probably one of the most important factors determining the reversibility of the damage. It is possible that significant central macular thickness reduction may not be associated with a significant visual acuity increase if the damage in the macula is irreversible due to the chronicity of the macular edema.
The patients in both groups had multiple intravitreal injections of triamcinolone and bevacizumab. The authors reported that the difference in the number of injections between groups (3.6 ± 0.8 in the bevacizumab group and 2.4 ± 0.5 in the triamcinolone group, P = 0.08) was not significant. However, the p-value of 0.08, in fact, is very close to the significance. There is a marked difference for mean injection numbers between the groups.
From the paper, we do not know the mean duration of macular edema in the treatment groups. We think that both the duration of macular edema and the number of injections may significantly affect the visual acuity and central macular thickness results. For this reason, we kindly ask the authors to perform (1) the statistical difference for the duration of macular edema between the treatment groups and (2) disease duration-adjusted and number of injection-adjusted central macular thickness–visual acuity correlations between the groups. We believe that these new statistics will further explore the effects of triamcinolone and bevacizumab on the central macular thickness and visual acuity.
1. Lim JW, Na KI. A comparative study between intravitreal triamcinolone and bevacizumab for macular edema due to central retinal vein occlusion with poor vision Indian J Ophthalmol. 2011;59:93–6