New Approach to the Analysis of Raw Data from the Ocular Response Analyzer

Abstract

Purpose: The aim of this research was to present a new approach for the potential characteristics of the anterior eye, based on numerical analysis of the raw data from multiple measurements on 1 eye captured with use of the Ocular Response Analyzer (ORA). Methods: The measurements were carried out 6 times on every eye, one by one, on 29 patients using the ORA. Dependencies between values of 6 applanation pressures P₁ and P₂ from 1 eye and the new proposed time-dependent parameters sm and smm, obtained from the raw data, were used to determine new characteristic features of the anterior eye. Results: Obtained values for multiple applanation pressures P₁ and P₂ and their average value P_a from all measurements on 1 eye show strong linear dependencies with the new proposed time-dependent parameter smm. Conclusions: The new parameters based on slope coefficients a₁ and a₂, their difference Δa, and respective y-intercept values b₁, b₂, and Δb show some characteristic stability for a multiply measured eye and can be used for its characterization. These parameters can be used for differentiation of the eyes with higher accuracy than those obtained from a single measurement. They are likely related to some biomechanical properties of the anterior eye.

Correlations between corneal biomechanics and specular microscopy in patient with cataract

“…Corneal hysteresis (CH) represents the difference between the two pressure determinations, P1 and P2, reflecting the capacity for absorption of kinetic energy in the tissue, an indicator of corneal viscosity. The mean of the two pressure measurements (P1 and P2) determines the Goldmann correlated intraocular pressure (IOPg) [ 11 - 13 ].…”

Corneal Buckling during Applanation and Its Effect on the Air Pressure Curve in Ocular Response Analyzer

“…Additionally, the measurements performed on a rigid glass lenses [12] presented the lack of applanation associated with almost identical air pressure curves for every single measurement, due to complete pressure ejection from the pump. Access to raw data offered by ORA device, gives possibility to define own, new parameters of the anterior eye, which can be useful in new approach to ophthalmic diagnosis [13].…”

Raw data from Ocular Response Analyzer applied for differentiation of normal and glaucoma patients

“…The averaged values obtained from these few measurements can be used as characteristic value of obtained parameters. However, as it was shown in the paper [22] there exists some individual dependency between P 1 , P 2 pressures and some other raw parameters from different measurements, characteristic for the patient. So, such approach needs a few measurements on a single patient eye to define new characteristic parameters.…”

“…First, the Gaussian filter (size of window 17 data points) was applied for smoothing both curves. As in our previous work, measurements below 2 in the waveform score quality parameter were rejected from further processing due to their noise [22]. Four consecutive measurements with the waveform score greater than 2 were analyzed.…”

“…So, such approach needs a few measurements on a single patient eye to define new characteristic parameters. These parameters, characterizing different measurements (multimeasurements parameters) for the same patient eye, can be also used for differentiations of the eye properties [22]. Despite the differences in the form of these two curves given by the ORA for individual measurements on the same eye, there still exist some characteristic dependences and correlations between selected parameters for the individual eye.…”