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C. Cheng, L. W. Yip, M. G. Natividad, V. Yong, B. Lim, H. Wong; Comparison of Influence of Cataract and Small Pupil on Retinal Nerve Fiber Layer Thickness Measurements Between Time Domain and Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):234.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of cataract and small pupil on retinal nerve fiber layer (RNFL) thickness measurements using spectral domain optical coherence tomography (SD-OCT) and compare the measurements with time domain optical coherence tomography (TD-OCT).
25 eyes from 25 normal subjects undergoing cataract surgery were analysed. RNFL thickness was measured three times before and after dilation in a single sitting, pre-operatively and one-month after surgery, using TD-OCT (Stratus Fast RNFL 3.4 acquisition protocol) and SD-OCT (Cirrus 200x200 Optic Disc Scan).
Mean RNFL thickness measured by TD-OCT was thicker compared to SD-OCT and the difference was significant (p<0.001). Pupil dilatation caused RNFL measurements to increase in both modalities but the mean differences were not significant (p>0.05). Removal of cataract caused significant increase in RNFL measurements in both modalities (p< 0.02). Reproducibility for both machines showed marked improvement with pupil dilatation and further improvement after removal of cataract. The intraclass correlation coefficient (ICC) at 95% confidence interval (CI) for pre-operative undilated, dilated, and post-operative dilated global measurements were 0.69, 0.87, and 0.95 for TD-OCT, and 0.74, 0.90, 0.91 for SD-OCT respectively. This pattern was reflected in the quadrants except in the nasal quadrant for TD-OCT, which remained poor (< 0.75).
Cataracts, not pupil size, appear to have significant influence on RNFL measurement in both modalities. The effect on each modality does not seem to be different except in the nasal quadrant. Reproducibility of both modalities is good with dilated pupil and clear media but in the presence of cataract and small pupil, reproducibility is better with the SD-OCT. RNFL thickness measurements are generally higher in TD-OCT than with SD-OCT and cannot be directly compared.
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