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Danilo Andrade de Jesus, Maryam Mousavi, Izabela Katarzyna Garaszczuk, Irene Siso-Fuertes, Hema Radhakrishnan, Robert Iskander; The role of corneal macro and micro-structure on Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4329.
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© ARVO (1962-2015); The Authors (2016-present)
In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements.
Fifty-six subjects aged 44.6 ± 19.3 years (mean ± standard deviation) ranging from 22 to 78 years were recruited for this study. IOP was measured using a non-contact tonometer, Corvis ST (Oculus, Wetzlar, Germany). Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as the central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. They were measured with IOLMaster 700 (Carl Zeiss Meditec AG, Germany). Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT (Copernicus HR, Optopol, Poland) was modelled with the Generalised Gamma distribution that is characterised with a scale and two shape parameters.
In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R2=0.25, p<0.001). Regarding the micro-structure, the scale and the ratio of the shape parameters of Generalised Gamma distribution presented a statistically significant correlation with IOP (R2=0.19, p<0.001 and R2=0.17, p<0.001, respectively). These correlations remained significant after correcting the IOP (using the Dresden table). For the studied group, a weak, although significant correlation was found between age and IOP (R2=0.053, p=0.04). However, it became non-significant after correcting the IOP with the CCT (p>0.05). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R2=0.39, p<0.001) to study the role of the corneal structure on IOP.
We show that IOP calibration in applanation tonometry must be considered from the macro and micro-structure perspective. OCT speckle statistics have the potential to be employed to infer the corneal micro-structure and hence, to further calibrate the IOP measurements.
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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