ABSTRACT. This review article discusses the relationship between ocular perfusion pressure and glaucoma, including its definition, factors that influence its calculation and epidemiological studies investigating the influence of ocular perfusion pressure on the prevalence, incidence and progression of glaucoma. We also list the possible mechanisms behind this association, and discuss whether it is secondary to changes in intraocular pressure, blood pressure or both. Finally, we describe the circadian variation of ocular perfusion pressure and the effects of systemic and topical medications on it. We believe that the balance between IOP and BP, influenced by the autoregulatory capacity of the eye, is part of what determines whether an individual will develop optic nerve damage. However, prospective, longitudinal studies are needed to better define the role of ocular perfusion pressure in the development and progression of glaucoma.

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These findings indicate that RNFL measurements with spectral-domain OCT display excellent reproducibility, with low intrasession, intersession, and interexaminer variabilities.

Purpose To evaluate the influence of pupil dilation on retinal nerve fibre layer (RNFL) measurements with spectral domain optical coherence tomography (OCT). Patients and Methods In total, 29 healthy individuals and 26 glaucoma patients underwent RNFL measurements with the Cirrus HD-OCT Model 4000 (Carl Zeiss Meditec Inc.) before and 30-40 min after pupil dilation with one drop of tropicamide 1%. Average thickness, quadrant thickness, and clock-hour thickness measurements were compared with the paired Student's t-test. We also compared the quality scores of the images obtained pre-and post-pupil dilation. Results Mean ages in the glaucoma and control groups were 58.3±13.4 and 41.6±16.4 years respectively (Po0.001). Mean deviation values were À6.96 þ 6.31 dB in the glaucoma group and À1.26 þ 0.79 dB in the control group (Po0.001). Mean RNFL measurements obtained in the glaucoma group were significantly lower than those obtained in the control group (Po0.001). There were no statistically significant differences between mean quality scores obtained before and after dilation neither in the glaucoma group (7.73±0.92 vs 7.54±1.10, P ¼ 0.232) nor in the control group (8.14 ± 0.88 vs 8.00 ± 0.71, P ¼ 0.380). There was no statistically significant difference between mean RNFL measurements obtained pre-and post-pupil dilation neither among normal individuals (P40.05), nor among glaucoma patients (P40.05). Conclusion The results of this study indicate that RNFL measurements obtained with spectral domain OCT are not influenced by pupil size.

Purpose. To investigate the sensitivity and specificity of machine learning classifiers (MLC) and spectral domain optical coherence tomography (SD-OCT) for the diagnosis of glaucoma. Methods. Sixty-two patients with early to moderate glaucomatous visual field damage and 48 healthy individuals were included. All subjects underwent a complete ophthalmologic examination, achromatic standard automated perimetry, and RNFL imaging with SD-OCT (Cirrus HD-OCT; Carl Zeiss Meditec, Inc., Dublin, California, USA). Receiver operating characteristic (ROC) curves were obtained for all SD-OCT parameters. Subsequently, the following MLCs were tested: Classification Tree (CTREE), Random Forest (RAN), Bagging (BAG), AdaBoost M1 (ADA), Ensemble Selection (ENS), Multilayer Perceptron (MLP), Radial Basis Function (RBF), Naive-Bayes (NB), and Support Vector Machine (SVM). Areas under the ROC curves (aROCs) obtained for each parameter and each MLC were compared. Results. The mean age was 57.0±9.2 years for healthy individuals and 59.9±9.0 years for glaucoma patients (p=0.103). Mean deviation values were -4.1±2.4 dB for glaucoma patients and -1.5±1.6 dB for healthy individuals (p<0.001). The SD-OCT parameters with the greater aROCs were inferior quadrant (0.813), average thickness (0.807), 7 o'clock position (0.765), and 6 o'clock position (0.754). The aROCs from classifiers varied from 0.785 (ADA) to 0.818 (BAG). The aROC obtained with BAG was not significantly different from the aROC obtained with the best single SD-OCT parameter (p=0.93). Conclusions. The SD-OCT showed good diagnostic accuracy in a group of patients with early glaucoma. In this series, MLCs did not improve the sensitivity and specificity of SD-OCT for the diagnosis of glaucoma.