Abstract
Purpose: :
To describe a method for quantifying the amount of macroscopic fluid pockets in the macula on spectral domain optical coherence tomography (OCT) and to use this as a part of evaluation to compare the efficacy of bevacizumab with triamcinolone acetonide on diabetic macular edema (DME).
Methods: :
24 eyes of 24 patients received intra vitreal bevacizumab and 39 eyes of 39 patients received intravitreal triamcinolone acetonide for DME. None had prior intra vitreal injections. Laser photocoagulation if done, was at least 3 months before injection. Pre and post injection OCT (Cirrus, Zeiss) pictures were evaluated for overall macular thickness, component of fluid pockets, and the spongy tissue swelling. The quantification was done with three lines drawn manually on the OCT pictures- one through the fovea and two 150 microns on either side. The average measurements of the three were analyzed.
Results: :
For both drugs, significant reduction was seen (p<0.05) in overall macular thickness and fluid space (not for spongy swelling). Triamcinolone achieved greater reduction in total macular thickness than bevacizumab (P=0.002). The baseline total macular thickness, fluid space and baseline percentage of fluid space (expressed as a fraction of total macular thickness) were predictive of extent of reduction in macular thickness for both drugs. Visual improvement reached significance only for triamcinolone and that too only for eyes with foveal detachment and not for bevacizumab. Baseline percentage space occupied by fluid, predicted significant visual improvement for eyes receiving triamcinolone. Quantum of reduction of overall macular thickness and fluid space did not correlate with visual improvement for both drugs. Foveal detachment completely resolved in 64.2% of 28 eyes in triamcinolone group and 42.8% of 7 eyes in bevacizumab group. We have also developed a computerized approach for analyzing the fluid compartments in OCT using volumetric analysis.
Conclusions: :
Overall macular thickness may not be the only parameter to look at in the analysis of DME. Fluid compartments -specifically foveal detachment plays an important role in predicting the extent of visual improvement. Triamcinolone appears to have better affect on the macular thickness than bevacizumab. The computerized volumetric analysis of the subcomponents of the macular OCT scan could potentially be a better way of OCT evaluation in DME.
Keywords: diabetic retinopathy • imaging/image analysis: clinical