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Hetal Buckhurst, Bernard Gilmartin, Robert Cubbidge, Manbir Nagra, Nicola Logan; The relationship between anterior segment biometry and corneal biomechanics in myopia. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1639.
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© ARVO (1962-2015); The Authors (2016-present)
The Reichert Ocular Response analyser (ORA) provides data on corneal biomechanics via measures of corneal hysteresis (CH), corneal resistance factor (CRF) and additional waveform parameters (AWPs). Utilising the Scheimplug principle the Pentacam (Oculus) provides data on the biometry of the cornea and anterior segment (AS). Given the premise that there is correspondence between the biomechanical and biometric properties of the AS we examine the nature of the correspondence and whether it is altered in myopia.
Data were collected from adults 18-40 yrs of British-White and British-South-Asian descent [MSE (D) 20 non-myopes (≥-0.50) 0.64±1.38; 22 myopes (<-0.50) -6.24±4.28]. The Pentacam was used to measure minimum corneal thickness (CT), central CT (CCT), peripheral CT, anterior chamber volume (ACV) and depth (ACD), corneal volume (CV), anterior and posterior best fit sphere (BFS) and front (FS) and back surface (BS) keratometry flat (Kf) and steep (Ks). The ORA was used to record CH, CRF and 37 AWPs. Refractive error (Rx) and axial length were measured using autorefraction and the Zeiss IOLMaster. Correlations between Pentacam and ORA parameters were tested using Pearson’s correlation coefficient. Multiple linear regression was used to determine the level of association between Pentacam and ORA data. One-way repeated measures ANOVAs tested differences in Pentacam and ORA parameters for Rx, ethnicity and age.
No significant effect of Rx, age and ethnicity was found for the Pentacam and ORA metrics. CV was associated with CH (p=0.006), explaining 17.7% of its variability, whereas CRF was related to CCT (p<0.001) explaining 29.1% of its variability. Several AWPs were found to be associated with 7 Pentacam parameters (Anterior BFS, ACD, ACV, FSKs, FSKf, CCT and inferior CT, all p<0.05) e.g. respectively anterior BFS explained 19.1%, 25.8%, 23.1% and 13.6% of the variability of P1area, P2area, P2area1 and Dive2 and ACD explained 15.9%, 14.2%, 10.4% and 11.4% of the variability of Aspect1, Aspect21, Uslope11 and Dslope21.
The study demonstrates significant correspondence between ORA and Pentacam parameters that is limited to specific combinations of AWPs and biometric parameters. The correspondence was shown to be independent of Rx. Of interest would be investigation of the relationship between anterior biometric and biomechanical properties in myopia in young developing eyes.
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