First Author: A.J POLAND
Co Author(s): M. Lewandowska M. Mulak D. Siedlecki M. Zaj?c
Purpose:
Cataract treatment is based on removing cloudy lens and replacing it with an artificial implant (Intraocular Lens, IOL). This could cause serious change in the imaging properties of the eye optical system and significantly affect the quality of the retinal image, which provides input information to the whole visual system. Therefore it is important to study retinal image quality, depending on IOL parameters and implanting technique or implant location. The aim of this study is to examine the quality of retinal image in the eye with IOL implanted using computer simulation and measurements on artificial eye.
Setting:
: Quality of retinal image in the eye with IOL depends not only on the design of implanted IOL but also on its exact location. The implantation procedure not always assures correct fixation of the IOL so the analysis of the impact of this factor on the retinal image is important.
Methods:
Testing of the retinal image quality in vivo is difficult, if even possible at all. In particular it is impossible to direct compare the performance of IOL of different designs or the influence of its improper location in the eyeball. It can be done, however, with help of numerical simulation or measurements on artificial eye model.
In the first method a Point-Spread Function (PSF) of the eye with IOL was calculated using a computer programme for optical systems design ZEMAX® with eye parameters according to Dubbelman model. On this basis such quality measures characterizing optical performance as Strehl ratio and Modulation Transfer Function (MTF) were evaluated.
The second method uses the optomechanical eye model consisting of artificial retina and the chamber filled with immersion liquid. The IOL placed in this chamber is fixed in a holder enabling controllable translations and rotationions. The light intensity distribution in the image of an edge (Line Spread Function, LSF) was measured and then PSF and MTF were calculated.
Results:
Both methods: numerical simulations and experimental measurements show that longitudinal displacement of the IOL does not influence seriousle the retinal image (except of inducing refraction error). Decentration of IOL greater than about 0.3 mm causes noticeable widening of the LSF half-width. IOL tilt on more than 2 degrees causes about 10% decrease of Strehl ratio.
Conclusions:
Both proposed methods of retinal image evaluation create a unique possibility to compare the optical performance of different designs of IOLs and to study the influence of its improper location inside the eyeball without burdening the real patients.
The work was done in the framework of the Research Project N N518 414138 funded by Polish Ministry of Science and Higher Education
Financial Disclosure:
None
