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Measurement of stray light without using flicker

Poster Details

First Author: N.Ito JAPAN

Co Author(s):    K. Ohnuma   M. Fukui   T. Noda        

Abstract Details



Purpose:

Psychophysical and physical approaches have been proposed to measure the intensity of stray light on the retina. C-quant® (Oculus) using flicker, a psychophysical method based on the research of van den Berg and colleagues. However, this method is unsuitable for children and subjects with startle epilepsy or a similar neural response. We developed a method that does not use flicker in a psychophysical manner.

Setting:

Center for Frontier Medical Engineering, Chiba University

Methods:

The proposed measurement method consists of a high-intensity light-emitting diode (LED) positioned in the center of a liquid crystal display. Observers gaze at an optotype positioned near the LED, and the intensity of the optotype is decreased until the observers cannot identify it using stray light. The stray light intensity is determined by the next set-up that consists of a glass plate or half-mirror placed on the optotype at a 45-degree angle. The light from another source positioned by the side of the glass is reflected by the glass and overlaps the light from the optotype. By changing the intensity, we can obtain the intensity of the unidentified characters as the equivalent intensity of the stray light. Two men with normal eyes and 20/20 vision were tested with and without a diffusing filter :Black Promist 3®(Tiffen). The emission time of the LED is 1 second. The viewing angle is set from 1 to 2 degrees.

Results:

The stray light intensity with the diffusing filter was about 8 times as strong as that without a filter when tested with the two volunteers. This magnitude is nearly the same as the intensity difference of the stray light obtained by the physical method.

Conclusions:

The proposed method can measure the intensity of stray light. The next steps is to measurement stray light with more eyes including those with cataracts and confirm the validity of the method. The modified method using two parallel light sources or a ring source can be applied. The modified system has the ability to be used commercially. FINANCIAL INTEREST: NONE

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