Abstract
To compare fixation deviation and stability with soft contact lens correction and device built-in auto-focus system during optical coherence tomography angiography (OCTA). This observational study measured OCTA metrics first with contact lens correction, followed by removal of contact lenses, using the device auto-focus system at a University Optometry Clinic, Hong Kong. All participants were habitual soft contact lens wearers with either low or high myopia. OCTA measurements were obtained using a spectral domain OCTA. Fixation deviation was distance (in pixels) of the fovea to the center of the OCTA measurement grid. Fixation stability was test–retest repeatability (TRR) and coefficient of variation (CV) of fixation deviation from three consecutive OCTA measurements. OCTA metrics included vessel length density (VD), perfusion density (PD), and foveal avascular zone (FAZ) area. Averaged OCTA metrics were calculated from three measurements and compared between the two correction methods. The mean ± SD spherical equivalent of 74 eyes from 74 myopes measured was − 1.94D ± 0.75D in low myopes (n = 37) and − 7.97D ± 1.31D in high myopes (n = 37). When corrected with contact lenses, visual acuities of high myopes (median [IQR], − 0.06 [0.08] logMAR) and low myopes (− 0.02 ± 0.08 logMAR) were similar (P = 0.060), and with similar fixation deviation (5.0 ± 2.2 pixels vs 5.3 [3.6] pixels; P = 0.689). High myopes had poorer fixation stability than low myopes (TRR: 10.2 pixels vs 7.5 pixels; CV: 65% vs 54%, respectively). The worst fixation stability occurred when high myopes were corrected using the auto-focus system (TRR: 12.5 pixels, CV: 72%). The difference in VD and PD was within 1 mm−1 and 1%, respectively. The FAZ area was similar. Difference in OCTA metrics was small in each refractive group (< 1 mm−1 in VD, and < 2% in PD). High myopes had more stable fixation when corrected when wearing contact lenses. Subjects with good contact lens corrected visual acuity should wear their contact lenses during OCTA measurements.
Highlights
MethodsHealthy adult myopes with habitual soft contact lens wear were recruited. This included low and high myopia according to the spherical equivalent (sphere plus half the refractive astigmatism)
To compare fixation deviation and stability with soft contact lens correction and device built-in autofocus system during optical coherence tomography angiography (OCTA)
An average Fixation deviation (FD) from three consecutive OCTA measurements was calculated for each eye and the average FD of all subjects was computed
Summary
Healthy adult myopes with habitual soft contact lens wear were recruited. This included low and high myopia according to the spherical equivalent (sphere plus half the refractive astigmatism). Thereafter, subjects were required to remove their contact lenses After measuring their unaided vision, non-cycloplegic auto-refraction and axial biometry (Nidek AL-Scan, Nidek Co. Ltd., Japan), OCTA measurements were conducted again using the same OCTA device and following the same protocol. OCTA measurements were obtained using a commercially available spectral-domain OCT (Cirrus 5000, Carl Zeiss Meditec, Inc., CA, USA). Triplicate OCTA scans centered at the fovea were obtained in each eye using the two correction methods, i.e. contact lens and auto-focus. An average FD from three consecutive OCTA measurements was calculated for each eye and the average FD of all subjects was computed. Coefficient of variation (CV) of fixation deviation, the ratio of the standard deviation to the mean, from three OCTA measurements was calculated. Data are presented as mean ± standard deviation (SD) or median (interquartile range, IQR)
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