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Adam C Janot, Jessica Randolph, Vikram Brar; Utilizing Spectral-Domain Optical Coherence Tomography to Measure Panretinal Photocoagulation’s Effect on Retinal Nerve Fiber Layer Thickness in Patients with Proliferative Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1808.
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© ARVO (1962-2015); The Authors (2016-present)
Panretinal photocoagulation (PRP) is the standard of care in the treatment of proliferative diabetic retinopathy (PDR). Prior studies have attempted to measure PRP’s effect on peripapillary retinal nerve fiber layer (RNFL) thickness using older optical coherence tomography (OCT) technology, but have shown inconsistent results. We utilized a prospective-cohort study design to quantify the RNFL’s response to PRP using spectral-domain optical coherence tomography (SD-OCT) with image registration, allowing scans to align precisely with prior scans and facilitate more accurate measurements over time.
Study inclusion criteria were patients who underwent a single treatment of first-time PRP, with a minimum of 1000 spots in a 360-degree fashion. Exclusion criteria included any history of optic neuropathy, glaucoma, ocular hypertension, and poor scans that could not be re-segmented. Pre-PRP SD-OCTs were completed, using a Heidelberg Spectralis OCT, in all patients and compared to SD-OCTs done at all follow-up visits. To compare the data over time, the SD-OCTs were divided in 6 post-PRP groups (1-60, 61-120, 121-240, 241-360, 361-480, and >480 days). Data was normalized by measuring percent-change from pre-PRP values. A two-sided, pairwise, t-test for the mean was used to determine the significance of RNFL changes from baseline.
22 eyes from 17 patients were enrolled in the study. The 1-60 day post-PRP scans showed statistically significant RNFL thickening in global thickness (10.8±0.9%, p=0.004) as well as the inferonasal (10.1±1.0%, p=0.002), inferotemporal (11.1±1.0%, p=0.001), temporal (13.0±1.5%, p=0.007), and supratemporal (7.1±0.7%, p=0.003) regions. After 60 days, there was a return to baseline RNFL thickness that was maintained throughout the follow-up period (see figure 1).
Following PRP, there is an initial thickening of the peripapillary RNFL followed by a return to pre-PRP thickness. In patients with PDR and glaucoma, RNFL thickness measured by SD-OCT can be used reliably to monitor for progression of disease beginning 60 days after PRP, especially in those whose laser pattern may affect visual field results.
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