2015-06: Visual Strehl ratio metric derived from wave aberrations to predict visual performance in cataract eyes
Rationale: The image-forming properties of the eye can be fully described by the wave aberrations (1). The wavefront error of the eye can be described by normalized Zernike (2) (3), expansion since, with few coefficients, it traces an entire wavefront aberration map. Furthermore, each Zernike function (known as mode) corresponds to one optical aberration. In one study (4), it has been presented that the visual Strehl ratio (VSR) metric accounts for 81% of the variance in high-contrast logMAR visual acuity (VA) which makes the metric a strong predictor of visual performance in normal eyes. In the present study, the method will applied to investigate the correlation between the VA and the VSR metric calculated using the modulation transfer function (MTF) (5) method (VSMTF) on eyes with cataract. As a strong correlation is expected, the metric is potentially a reliable predictor of visual performance in cataract (6) eyes.
Part 1 - To test the use of ocular aberrometry (1) as a means to quantify the severity of cataract in terms of VA.
Part 2 - To test the use of intraocular aberrometry as a means to quantify the severity of cataract in terms of VA.
Study design: Exploratory observational case series.
Study population: Patients with cataract eyes of any type (i.e., nuclear, cortical, posterior subcapsular, and mixed cataract).
Main study parameters/endpoints: Zernike coefficients of ocular aberrations, Zernike coefficients of intraocular aberrations, visual acuity (logMAR), spatial frequencies (cpd), pupil diameter (mm), wavelength of the aberrometers (nm), and lens opacities classification system (LOCS)
Nature and extent of the burden and risks associated with participation, benefit and group relatedness: There is neither benefit nor risk for the participants. Measurements will be performed once at the time of a regular visit. Measurements are non-invasive and take 15 minutes.