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Florian M. Heussen, Yanling Ouyang, Srinivas R. Sadda, Alexander C. Walsh; Simple Estimation of Fluid Volumes using SD-OCT in Neovascular AMD. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4795.
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To evaluate simple methods of estimating cystoid macular edema (CME), subretinal (SRF) and pigment epithelial detachment (PED) volumes from spectral domain OCT (SD-OCT) that can be implemented by clinicians or reading centers without the need for additional analysis software.
Using a database of neovascular age-related macular degeneration (AMD) cases collected at our institute over a 3 year period that had macular cube (512 x 128) volume SD-OCT scans using either a Topcon 3D-OCT-1000 or Cirrus HD-OCT, we retrospectively selected single cases with multiple features associated with choroidal neovascularization (CME, SRF or PED). Cases with 3 or more follow-up visits were also selected for longitudinal analysis. Manual quantitative grading of CME, SRF and PED was performed using validated grading software (titled "3D-OCTOR") in accordance to our reading center protocol. In addition to detailed volumetric analysis, simplified measurements were made for each lesion including: # of B-scans involved, # of A-scans involved, and maximum height. Measurements derived from these parameters, such as estimated area and volume, were also computed. Linear correlation coefficients between the cube root of the volume and the latter variables were calculated. Longitudinal data was analyzed separately from cross-sectional data.
15 eyes were included in the cross-sectional analysis (CSA) while 19 scans from 4 eyes were included in the longitudinal analysis (LA). In the CSA group, maximum lesion height correlated well with manual grading with r2 values of 0.89, 0.85 and 0.42 for CME, SRF, and PED respectively while estimated lesion volume (max height * B-scan count) demonstrated the highest correlations (r2 = 0.89, 0.97 and 0.78 for CME, SRF, and PED respectively). In the LA group, B-scan count correlated best with SRF volumes (r2=0.92) while maximum height correlated best with CME and PED volumes (r2 0.97 and 0.62 respectively).
Our data suggests that simplified estimators of CME, SRF and PED volumes exist and are accessible for use by clinicians without the need for specialized software or exhaustive manual segmentation. These simple approaches could facilitate the use of more quantitative disease monitoring strategies in patients undergoing therapy for neovascular AMD.
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