Optical Coherence Tomography Grid Decentration and Its Effect on Macular Thickness Measurements

Purpose: To evaluate the rate of optical coherence tomography (OCT) grid decentration in a routine practice and its effect on thickness measurements Methods: Topcon spectral domain OCT scans from various macular diseases including age related macular degeneration, diabetic macular edema, macular pucker and central serous chorioretinopathy (CSCR) were studied in all patients visited during seven consecutive days. In each scan, the macular EDTRS grid was evaluated for decentration. After grid adjustment, the changes in central subfield thickness (CST) measurements were recorded. Differences >1 μm and >8.5 μm between automatically determined and manually adjusted CST measurements were recorded as grid decentration and significant grid decentration. Results: Ninety-three OCT scans of 93 eyes were evaluated. Thirty-three scans were unreliable for grid adjustment. In the remaining 60 eyes, grid decentration was found in 32 eyes (53.3%). The mean change in CST after grid adjustment was 41.1±55.01 (3-251) microns. Clinically significant CST changes were found in 24 eyes (40%). No significant relationship was found between underlying disease and corrected CST, and grid decentration. Conclusion: Abnormal retinal thickness map was found in a significant number of scans. Topcon OCT scans should be evaluated routinely for grid decentration.