Abstract
Abstract: :
Purpose: The purpose of our research is to develop and test a simple eye model, incorporating a phase plate to represent the interior ocular aberrations that may be used to improve wavefront based refractive treatment planning. Methods: As a first step, we create an aberrated eye model (in Zemax) based on the Liou–Brennan model eye complete with a gradient refractive index for the crystalline lens. Ocular aberrations are controlled by modifying either the lenticular or corneal surfaces. We then obtain a postoperative eye by applying a wavefront based treatment using the current approach. The postoperative aberrations of the treated eye are then calculated to quantify the errors resulting from this treatment algorithm. In the second step, a simple eye model using as single corneal surface and a phase plate to represent internal aberrations is constructed for the complete eye variation. The phase plate is calculated from a scaling of the difference between cornea and ocular aberrations. The scaling ensures that interaction between the cornea and the internal aberrations is taken into account and predict accurately the impact of the wavefront treatment. Finally, we compare the ocular aberrations of the complete eye model variations to those of their phase plate model counterparts. Results: The eye models have a range of preoperative defocus values from –4 D to +4 D, and spherical aberration values from –2 µm to +2 µm. The maximum RMS value of the higher order aberrations is 1.5 µm. In all cases, the phase plate model ocular aberrations matches the complete eye aberrations to within 97% for on–axis aberrations and within 93% for off–axis aberrations. The postoperative residuals (as a percent of the preoperative values) for defocus are on average 1.4% and 1.8% for the complete eye and phase plate models, respectively. The average residuals for spherical aberration are 3.1% (complete) and 2.7% (phase plate), and for higher order aberrations they are1.4% for both models. In addition, the maximum residual value (of spherical aberration) was 26% for the complete eye, and 28% for the matching phase plate model. Conclusions: We have designed a phase plate model that demonstrates good agreement of preoperative and postoperative aberrations with a complete eye model. This demonstrates that given corneal and ocular aberration data (both clinically available), we can construct a simplified eye model for predicting outcomes of wavefront based refractive surgery that may then be used to modify current treatments to optimize wavefront based refractive treatments.
Keywords: refractive surgery: optical quality • optical properties • refractive surgery: other technologies