Purpose:
Cystoid macular edema (CME) represents a common pathological appearance of the retina in various ocular diseases. Currently Spectral Domain Optical Coherence Tomography (SD-OCT) allows measurement of central foveal thickness and total macular volume. We describe a novel automated method for measuring intraretinal cysts and tissue and total volume of the macula, allowing correlation between these parameters and other clinical parameters in patients with CME.
Methods:
Implementing image analysis algorithms, we have developed software ("Cystometer") that can automatically delineate retinal tissue and intraretinal cystic borders and compute macular tissue volume and cystic volume. These volumes were determined by examining OCT movies (Audio Video Interleave files, each representing 128 SD-OCT B Scans of 1 examination). We correlated these values with logMar visual acuity (VA) in patients with CME secondary to diabtetic retinopathy (DR) , branch retinal vein occlusion (BVO) and pseudophakia (PK). Generalized Estimating Equation regression, which accounts for correlated data, was used for statistical analysis.
Results:
Analysis of 113 movies representing 16 eyes of 13 patients with CME showed the software to be reliable in delineating retinal tissue borders compared to the lines delineated by Cirrus SD-OCT (Carl Zeiss Meditec, Dublin, CA) software. We found an inverse correlation between increasing tissue volume and cystic volume with VA (p=0.004, p=0.003 respectively). In CME related to BVO the cystic volume had less effect on visual acuity than in diabetic and pseudophakic CME (p=0.094).
Conclusions:
Analysis of OCT images using this software can provide reliable quantitative information that can be useful in the follow-up of patients with CME and allows correlation with VA. Increasing cystic and tissue volumes have a deleterious effect on visual acuity, the former to a lesser extent in BVO than in DM and PK CME.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina