Abstract
Purpose :
It is of interest to determine how aberrations across the wide visual field and eye shape change over time in children. The study aims to demonstrate the following features of a scanning Shack-Hartmann wavefront sensor (WFS): (1) compact size, (2) natural open-view central fixation, (3) invisible laser and (4) rapid scanning speed.
Methods :
We have designed an innovative scanning mechanism with compact motorized stages to achieve scanning along horizontal, vertical, and diagonal meridians. Scanning the horizontal meridian uses the rotary stage only, while scanning in the vertical direction is achieved by translating the x-z linear stage and tilting the hot mirror. Diagonal scanning involves both operations. A high sensitivity CCD sensor ensured each scan was completed within a blink interval, and an invisible 980 nm laser minimized visual distractions. An open-view design allows participants to maintain their central fixation while minimizing instrumental myopia and providing accommodation control without cycloplegia. The accuracy of the WFS was tested by comparing an optical ray-tracing simulation in Zemax to horizontal scan measurements from a model eye. The model eye consisted of a 25 mm focal length doublet with a diffuser at its focal point. Optical ray tracing was performed at 0 to 30° degrees in 5° steps and compared with the measured aberrations.
Results :
Zernike coefficients from the Zemax simulation for vertical astigmatism (z5) and horizontal coma (z8) were plotted against data from wavefront measurements collected with the sensor and the model eye. The r2 values from linear regression were 0.9835 (z5) and 0.9805 (z8), representing a good correlation. As expected, z5 and z8 increased in magnitude with eccentricity, while z12 remained stable at 0.008 ± 0.006 µm (mean ± stdev) across the horizontal meridian. A single scan, up to ±30°, was completed in less than 3 seconds.
Conclusions :
We have demonstrated a new version of a compact scanning WFS covering up to ±30°, ±35°, and ±20° along horizontal, diagonal, and vertical meridians, respectively. The WFS can be easily transported to measure the children’s eye’s aberrations across the visual field in a clinical or school setting.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.