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Viswanathan Ramasubramanian, Shreya Gupta; Can Central Intraocular Pressure Be Predicted Accurately from Peripheral Intraocular Pressure?. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5332.
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© ARVO (1962-2015); The Authors (2016-present)
Eyes with central corneal pathologies and post-refractive surgeries often preclude accurate measurement of intraocular pressure (IOP). The goal of the current study was to try to predict the central IOP from peripheral IOP in emmetropic and myopic eyes.
The study population included 25 emmetropes (ES) and 25 myopes (MS) aged 18 to 30 years. Three measurements of IOP were obtained using a non-contact air puff tonometer (Topcon CT80) at 5 corneal locations: central (cIOP), superior (sIOP), inferior (iIOP), nasal (nIOP) and temporal (tIOP). All peripheral corneal locations were approximately 2 mm from the limbus. Subsequently, three measurements of corneal thickness (CT) were taken using a specular microscope (Topcon SP-3000P) at the same central (cCT) and peripheral corneal (sCT, iCT, nCT, tCT) locations. All measurements were performed in the right eyes between 9 am and 3 pm.
A one-way repeated measures ANOVA showed statistically significant differences in the mean IOP and CT measured at the central and peripheral cornea within each subject groups (p<0.05). The mean SD of the IOP measurements were: sIOP: 0.88 mmHg (ES); 0.96 mmHg (MS), iIOP: 0.79 mmHg (ES); 0.63 mmHg (MS), nIOP: 0.64 mmHg (ES); 0.69 mmHg (MS), tIOP: 0.70 mmHg (ES); 0.73 mmHg (MS).There were statistically significant linear relationships between the central and peripheral IOPs in both the subject populations (p<0.05). Peripheral CTs, except for iCT were significantly linearly correlated with cIOP, in emmetropes (p<0.05). No significant relationships were observed between peripheral CTs and cIOP in myopes. The mean ± SD of the absolute differences between measured and predicted cIOP from peripheral IOP and CT measurements using linear regression equations for the two populations were: sIOP: 1.05 ± 0.70 mmHg (ES); 0.86 ± 0.71 mmHg (MS), iIOP: 0.78 ± 0.62 mmHg (ES); 0.72 ± 0.48 mmHg (MS), nIOP: 0.77 ± 0.59 mmHg (ES); 0.60 ± 0.49 mmHg (MS), tIOP: 0.94 ± 0.54 mmHg (ES); 0.61 ± 0.62 mmHg (MS), sCT: 1.07 ± 0.84 mmHg (ES), nCT: 1.12 ± 0.63 mmHg (ES), tCT: 1.03 ± 0.73 mmHg (ES).
Peripheral IOP and CT measurements can, on average, predict the central IOP in a population with a SD of 1 mmHg or less, with nasal and temporal IOP being the best predictors. Linear regression equations described in this study could be useful to estimate central IOP in conditions where direct measurement is not possible.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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