Research Proposal Summary

AIM: To measure the refractive index change with respect to the accommodation of an animal ocular lens. APPARATUS: 1. Swept Source OCT system. 2. 2-d galvo scanning set up. 3. Glass eye lens and a real eye. Description of apparatus: 1. Building of Swept Source Optical Coherence System a. The present Spectral Domain OCT system is incomplete. First task is to get the false color images from the Spectral Domain OCT system using the lab view software and perform some experiments on a known refractive index lens. b. A system similar to the above is built but with a broadband laser swept source. This source sweeps in a very narrow bandwidths (around 0.02nm) which increases the depth of penetration of the signal. Calculations of how broad the source should be and the sweeping resolutions are not yet done for the scanning of a human eye. c. Once the above step is done, the system is tested for any other errors and if any calibration etc is required. 2. 2-d scanning set up a. Purchase of Galvos which can scan the whole eye lens. All the specifications are to be very specific. b. To make the 2-d scanning system an automatic system, we have to install an ADC card to the computer and using a LabView program we control the speed etc. of the 2-D scanning set up. c. Set up the mirror on this stage and then test the system on the customized OCT system. Again some calibration and zero set up with the spatial co-ordinates is required. 3. Glass Lenses and real eyes are ready to use.

METHODS: 1. Measurement of accommodation: The eye lens is imaged completely and using the SS-OCT system and then from that image we find out the curvature. This measurement gives the amount of accommodation in every stage. 2. Measurement of Refractive index: The Signal coming out of the SS-OCT system will be having 2 high peaks spatially separated by a distance of say OD. After passing through the lens of the eye at a predefined thickness and the back scattered signal will be having the peaks spatially separated by some other distance say PD. Then RI can be calculated by OD/PD. EXPERIMENTS: 1. 1st set of experiments are to be done for a glass lens using the SD-OCT. In this experiment, we find the refractive index of the glass lens at different thickness because of curvature. 2. 2nd set of experiments use SS-OCT. In this, the first experiment is done to observe the changes in the OCT signal with the change in the thickness of glass. This is to see the depth of penetration and resolution of the system. Next experiment is by passing different fluids (glucose etc.) of different refractive index through the glass and measures the refractive indices. We then do it for a glass lens. Finally, we take some 5-10 pig eyes and then stretch, i.e, basically perform the accommodation using a stretching device and get the data 3. Extend this method to measure the aberrations. After August we do some in-vitro and in-vivo measurements to find the refractive index changes with the accommodation.