Florian Gekeler develops photorefraction techniques to measure human astigmatism.

The light emitted by infrared LEDs is returned from the back of the eye. Due to the special arrangement of the LEDs, the light is distributed across the pupil with an intensity gradient that depends on the refractive error of the eye.

	The refractive error is measured in 3 meridians (twice in each) by the 6 segments of the retinoscope. Measurement takes place at 25 Hz. Data (left and below) were collected in collaboration with Howard Howland (Cornell University, NY). x-axis: infrared photoretinoscope y-axis: Canon autorefractor R-1, serving as a reference

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