Comparison of the Efficacy between Time and Spectral Domain Optical Coherence Tomography for the Identification of Vitreomacular Interface

PURPOSE: To compare the efficacy of time domain (TD) and spectral domain (SD) optical coherence tomography (OCT) in determining vitreomacular interface (VMI). METHODS: VMIs were evaluated with TD and SD OCT images crossing the fovea horizontally in 69 eyes (mean age 52.7 +/- 15.4 years) and were classified as follows: (1) no vitreomacular separation (VMS), (2) incomplete VMS, and (3) unknown. RESULTS: In TD OCT, no VMS was observed in 2 eyes (2.9%), incomplete VMS in 2 eyes (2.9%), and unknown in 65 eyes (94.2%). In SD OCT, no VMS was observed in 31 eyes (45.0%), incomplete VMS in 13 eyes (18.8%), and unknown in 25 eyes (36.2%). In 31 eyes with no VMS on SD OCT, 29 eyes (93.5%) presented unknown on TD OCT (p<0.0001). In 13 eyes with incomplete VMS on SD OCT, 2 eyes (15.4%) showed incomplete VMS and 11 eyes (84.6%) showed unknown on TD OCT (p<0.0001). TD OCT was also non-informative in all 25 eyes with unknown on SD OCT. CONCLUSIONS: SD OCT allows better visualization of VMI than TD OCT, especially in patients with no VMS.

A Formula to Predict Spectral Domain Optical Coherence Tomography (OCT) Retinal Nerve Fiber Layer Measurements Based on Time Domain OCT Measurements

PURPOSE: To establish and validate a formula to predict spectral domain (SD)-optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness from time domain (TD)-OCT RNFL measurements and other factors. METHODS: SD-OCT and TD-OCT scans were obtained on the same day from healthy participants and patients with glaucoma. Univariate and multivariate linear regression relationships were analyzed to convert average Stratus TD-OCT measurements to average Cirrus SD-OCT measurements. Additional baseline characteristics included age, sex, intraocular pressure, central corneal thickness, spherical equivalent, anterior chamber depth, optic disc area, visual field (VF) mean deviation, and pattern standard deviation. The formula was generated using a training set of 220 patients and then evaluated on a validation dataset of 105 patients. RESULTS: The training set included 71 healthy participants and 149 patients with glaucoma. The validation set included 27 healthy participants and 78 patients with glaucoma. Univariate analysis determined that TD-OCT RNFL thickness, age, optic disc area, VF mean deviation, and pattern standard deviation were significantly associated with SD-OCT RNFL thickness. Multivariate regression analysis using available variables yielded the following equation: SD-OCT RNFL = 0.746 x TD-OCT RNFL + 17.104 (determination coefficient [R2] = 0.879). In the validation sample, the multiple regression model explained 85.6% of the variance in the SD-OCT RNFL thickness. CONCLUSIONS: The proposed formula based on TD-OCT RNFL thickness may be useful in predicting SD-OCT RNFL thickness. Other factors associated with SD-OCT RNFL thickness, such as age, disc area, and mean deviation, did not contribute to the accuracy of the final equation.

Comparison of Retinal Nerve Fiber Layer Thickness between Stratus and Spectralis OCT

PURPOSE: To compare the peripapillary retinal nerve fiber layer (RNFL) thickness of normal patients and those with various glaucoma diseases by time domain (Stratus) and spectral domain (Spectralis) optical coherence tomography (OCT). METHODS: The RNFL thickness as measured by the Stratus and Spectral OCT was compared (paired t-test). The relationship and agreement of RNFL thickness between the two OCT modalities were evaluated by Pearson correlation, Bland-Altman plot, and area under the receiver operating characteristic curve. RESULTS: Two-hundred seventeen eyes of 217 patients, including twenty-four normal eyes, ninety-one glaucoma suspects, seventy-six normal tension glaucoma cases, and twenty-six primary open angle glaucoma cases (POAG) were analyzed. The peripapillary RNFL thicknesses as measured by Stratus OCT were significantly greater than those measured by Spectralis OCT. However, in quadrant comparisons, the temporal RNFL thickness obtained using Stratus OCT were significantly less than those obtained using Spectralis OCT. Correlations between RNFL parameters were strong (Pearson correlation coefficient for mean RNFL thickness = 0.88); a high degree of correlation was found in the POAG group. Bland-Altman plotting demonstrated that agreement in the temporal quadrant was greater than any other quadrant. CONCLUSIONS: Both OCT systems were highly correlated and demonstrated strong agreement. However, absolute measurements of peripapillary RNFL thickness differed between Stratus OCT and Spectralis OCT. Thus, measurements with these instruments should not be considered interchangeable. The temporal quadrant was the only sector where RNFL thickness as measured by Spectralis OCT was greater than by Stratus OCT; this demonstrated greater agreement than other sectors.