Macular thickness after cataract surgery with intracameral cefuroxime

Abstract

We read with interest the article by Gupta et al.1 using optical coherence tomography (OCT) to compare retinal thickness after cataract surgery with and without intracameral cefuroxime. The OCT 2 was used to measure macular thickness in areas of concentric circles of 1.00 mm and 3.45 mm diameter, both centered on the fovea, approximating central and entire macular regions. Using OCT, this is achieved by having patients fixate on a central light. The machine then takes 6 consecutive scans in a radial spoke pattern, intersecting at the fixation point. The standard deviation (SD) of these 6 values provides an estimate of the measurement reproducibility and degree of patient fixation. Hee et al.2 found the SD to be 11 μm in normal subjects. A recent study (Ching et al.3) excluded any scans with a variation of more than 50 μm. Gupta et al.1 did not mention this variation, let alone exclude scans if the SD exceeded a certain value. In fact, the values obtained by Gupta et al.1 for central macular thickness were not significantly different from the entire macular thickness in both treatment and control groups. Brancata and Lubroso report 170 to 190 μm for foveal thickness compared with 200 to 275 μm general retinal thickness in their normal database (R. Brancato, MD, et al., “Guide to Optical Coherence Tomography Interpretation,” Innovation-News-Communication, 2004, pages 10–15). Other studies show similar results.2,3 Without any reference to SD in the 6 radial scans and with a central macular thickness not statistically different from the control group's entire macular thickness, it follows that results obtained by Gupta et al.1 were not a true reflection of macular thickness in their study. We feel there is a need to address the question of whether intracameral antibiotic injections result in increased macular thickness. However, the failure of the authors to provide evidence of patient fixation invalidates their results and leaves this question unanswered.