Abstract
Purpose::
The purpose of this research project was to investigate the effects of dynamic pupil changes on wavefront aberrations of the human eye. Specifically, we were interested in non-dilated, natural pupil behavior.
Methods::
A real-time Hartman-Shack wavefront sensor was designed where the key components are two very fast (up to 30 frames per second) and sensitive (12 bit) synchronized CCD cameras. Thus, we are able to measure pupil fluctuations and wavefront aberrations simultaneously. The speed allows for real-time measurements of pupil size changes and the sensitivity allows wavefront measurements with small pupils.For this proof-of-concept experiment, measurements were obtained for ten subjects. Four of the subjects had measurements made in both eyes and the remaining 6 had measurements made with their right eye only.Subjects were asked to rest in the dark room for at least 10 minutes to allow for some dark adaptation (pupil expansion). Next, the subjects positioned their head in a head rest. Once the eye was aligned using a fixation target (focused at infinity), a laser beam was shown in the eye for just over 2 seconds and images of the eye and centroids were simultaneously captured at a rate of 15 Hz.The wavefront error for each image of a sequence was calculated and the results plotted as a function of pupil diameter. In addition, for each eye, three artificial pupils were simulated and wavefront errors were calculated. A comparison of the wavefront errors for the artificial pupils versus the natural pupils was then made.
Results::
The results demonstrate that the aberration values show a strong dependence on pupil diameter. We also show that for some eyes, constructing an artificial pupil from larger natural pupils can result in errors in the predicted aberration values when compared to those measured with a natural pupil.
Conclusions::
We have developed a new technique to monitor real-time wavefront aberrations as the natural pupil varies in diameter. This tool is useful because we are able to monitor the eye as a function of its natural variations. We plan to extend our dynamic measurements to include such changes as accommodation and gaze.
Keywords: optical properties • refraction • pupil