Purchase this article with an account.
Mikhail Levin, Michael Campos, Anthony Dennison, Patrick De Guzman, Alireza Malek Tabrizi, Hong Fu; Measurement of light reflection and scatter from eyes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1483.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study is to compare the reflection and scattering signals from eye interfaces at several different wavelengths
Confocal optical measurements were used, based on several lasers in IR and visible spectrums (power 3-10mW). The light signals were detected with 1nW resolution. Dynamic range of measurements was increased up to 60dB by inserting an optical isolation unit allowed to detect almost all back reflected light. The signal to noise ratio of measurements was optimized by pinhole diameter variation. The measurements accuracy and reproducibility were within 1%. For setup testing, the reflection coefficients of various surfaces and interfaces were measured; they coincided to their values known from literature. The refraction indexes were determined from the measured surface reflection. The eyes were placed in a special container with low vibration sensitivity and ability of 3D precise scanning relative to the focused laser beam. The rabbit, pig and cadaver eyes were studied in air and liquid environments.
The confocal setups allow measuring the reflected signals from all eye interfaces in the liquid environments. The measured cornea reflection coefficients in air were close to ~2.4% and the signals from deeper interfaces were 0.0025-0.00025% for 1054nm beam. The scattering signals from eyes were 10-100 times less than the reflected ones from corresponding surfaces/interfaces (0.001-0.0001%). In turn, scattering from deeper layers were 2-4 times less than ones from the cornea surface that can reflect the structure difference between its anterior and posterior segments. The scattering signals from cornea and lens increased approximately proportional to the third power of the relative decrease in wavelength. The confocal setups were used for various liquids refraction index determination by surface reflection.
Using the confocal setups, we measured the light reflection and scattering for rabbit, pig and cadaver eyes in visible and IR spectrums. The scattering signals from eyes were 10-100 times less than the reflected ones from corresponding surfaces/interfaces and decreased from surface to depth. The scattering signals from cornea and lens increased approximately proportional to the third power of the relative decrease in wavelength. The refraction indexes for several eye immersion liquids were determined by surface reflection.
This PDF is available to Subscribers Only