Abstract
Purpose :
To study the effect of monthly 0.3 mg intravitreal ranibizumab injections on intraretinal hard exudates (HEs) and to correlate HE with macular thickness using spectral domain optical coherence tomography (SD-OCT) images of eyes with diabetic macular edema (DME).
Methods :
Twenty-two eyes of 22 subjects with DME were included in this IRB-approved prospective longitudinal study. All subjects underwent SD-OCT imaging on a single instrument (Cirrus OCT) at the South Coast Retinal Center in Long Beach, CA. All eyes were imaged using a 512 x 128 macular cube protocol (6 x 6 mm) centered on the fovea, at baseline and monthly for 12 months. For this study, we used the previously published en face grading technique for HE quantification. The en face OCT image and macular thickness values were obtained using commercial instrument software (Cirrus OCT en face analysis and macular thickness analysis 7.5). The en face slab was positioned between the outer border of the ganglion cell layer (GCL) and the external limiting membrane (ELM). HEs appear as sharply demarcated bright foci in these en face images. HEs were segmented and quantified with computer software (Photoshop version CC; Adobe). The mean HE area and the mean macular thickness at baseline and month 12 were compared using a paired t-test and correlated with Pearson analysis.
Results :
The average age of the 22 study participants was 65 (+/-8) years and there were 13 females and 9 males. There was a significant decrease (p = 0.003) in mean HE area from a baseline area of 0.48 (+/-0.45) mm2 to a month 12 area of 0.17 (+/-0.20) mm2. The mean absolute difference in HE area from baseline to month 12 was 0.30 mm2. The mean rate of reduction in HE area was 0.025 mm2 per month. Macular thickness significantly decreased (p<0.001) from baseline (332 µm) to month 12 (288 µm). At baseline, HE area significantly correlated with macular thickness (r= 0.5; p= 0.02). Similarly, decrease in HE area significantly correlated with decrease in macular thickness at month 12 visit (r= 0.46; p= 0.04).
Conclusions :
In the eyes with DME, monthly intravitreal ranibizumab injections resulted in significant reduction in intraretinal hard exudates which paralleled reductions in macular thickness. En face OCT quantification of HE may be a useful tool for following the progress of lipid exudate resolution during the treatment of DME.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.