DESIGN OF GAUSSIAN SPATIAL FILTER TO DETERMINE THE AMOUNT OF REFRACTION ERROR IN HUMAN EYE

The subjective method of eye testing (Myopia/Hyperopia) involves the communication between the optometrist and the Patient. Communication about the vision/clarity of an eye chart, which the Patient experiences, to the Optometrist and the communication which the Optometrist does to Patient would decide the final prescription. Though the Optometrist is expert in communication, if the Patient gives incorrect responses, it leads to inaccurate prescription. To overcome the above problem, the idea is to develop a novel eye testing method called “Patient Subjective Eye Testing (PSET)”, in which a Myopia/Hyperopia Patient interacts with a software application installed on a tablet. A standard eye chart is projected on to a screen. A similar eye chart is also displayed on the tablet. Now the Patient blurs the eye chart that is displayed on the tablet device by applying power in the units of 0.0625 diopters until he/she experiences no difference in the blurness of the optotypes in the projected chart and the displayed chart. The power is recorded and written in to prescription. For the realization of the above method, a Gaussian spatial filter is designed, which blurs the optotypes of the displayed eye chart similar to the blurness experienced in human eye. To design the filter, the amount of Gaussian blur per unit refraction error in human eye is determined by designing a human eye model using ZEMAX tool. For every unit of 0.0625 diopters ( in the range-2 diopters to +2 diopters) change in refraction power of the eye the amount of deviation in Gaussian energy distribution, on the retina, is determined. With these deviation values Gaussian masks are generated which are used by Gaussian filter to blur the eye chart image