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F. Berisha, G. T. Feke, T. Hirose, J. W. McMeel, N. Pfeiffer, L. R. Pasquale; Evaluation of Glaucomatous Damage Using Concomitant OCT Peripapillary Retinal Nerve Fiber Layer and Peripapillary Total Retinal Thickness Measurements. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4654. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify peripapillary retinal nerve fiber layer (RNFL) thickness as percentage of peripapillary total retinal (pTR) thickness in healthy subjects and glaucoma patients using optical coherence tomography (OCT), and to investigate whether pTR thickness measurements allow accurate discrimination between normal and glaucomatous eyes.
Seventeen patients with early open angle glaucoma (mean age 67.1 ± 9.2 years, cup-to-disc ratio 0.75 ± 0.7 and mean deviation of better than -6 dB) and 13 age-matched controls (mean age 63.8 ± 8.2 years) were studied. Peripapillary RNFL thickness was measured using the standard RNFL thickness circle scan mode of the Stratus OCT. The same circle scans were also used for pTR thickness measurements, and the RNFL percentage of total retinal thickness was calculated. The measurements were compared between the patients and the controls using unpaired t-tests.
In control subjects, peripapillary RNFL thickness in the superior quadrant is 42 ± 0.3 % of the total retinal thickness; in the inferior quadrant, 44 ± 0.3 %; in the temporal quadrant, 33 ± 0.4 %; and in the nasal quadrant, 30 ± 0.5 %. Average RNFL percentage of total retinal thickness was 37 ± 0.2 %. In the glaucoma group, percentage values were: superior 39 ± 0.4 %, inferior 36 ± 0.6 %, temporal 28 ± 0.6 % and nasal 28 ± 0.4%. The average value was 33 ± 0.3 %. The difference between the groups for the average RNFL percentage values was highly significant (p<0.0001). The difference between the groups for the RNFL percentage values was significant for the superior (p=0.006), inferior (p=0.0001), and temporal quadrants (p=0.038). The difference in the nasal quadrant was not statistically significant. Average pTR thickness was 262.4 ± 10.2 µm in the controls and 242.6 ± 11.5 µm in the patients (p<0.0001). The differences in pTR thickness in the superior (p=0.03) and inferior (p<0.0001) quadrants were significant, while the differences in the temporal and nasal quadrants were not significant.
The results suggest that average or inferior pTR thickness values can be used clinically as accurate parameters for quantitative evaluation of glaucomatous damage. These parameters may be particularly useful when RNFL thickness measurements are not obtainable due to failure of the OCT algorithm for detection of the RNFL boundaries.
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