Small-angle straylight in the eye is affected by the wavelength-dependent properties of the fundus. At those small angles, measurements using wavelengths near the peak of the spectral sensitivity of the eye might be better correlated with the visual aspects of straylight. However, the impact of fundus reflectance on the values of the straylight parameter at larger angles did not depend on the measuring wavelength.
Optical measurement of straylight in the human eye is a challenging task. Issues such as illumination geometry, detector sensitivity and dynamic range as well as various inherent artifacts must be addressed. We developed a novel instrument based on the principle of double-pass optical integration adapted for fast measurements in a clinical setting. The experimental setup was validated using four different diffusers introduced in front of the eyes of ten subjects. Measurement limitations and future implications of rapid optical measurement of straylight in ophthalmic diagnosis are discussed.
CXL causes corneal dehydration that can be detected immediately after the procedure. This phenomenon may contribute to increased mechanical stiffness of the cornea. A change in stiffness by means of compressibility could not be detected in porcine corneas.
Citation: Benito A, Hervella L, Tabernero J, et al. Environmental and genetic factors explain differences in intraocular scattering. Invest Ophthalmol Vis Sci. 2016;57:163-168. DOI:10.1167/iovs.15-17897 PURPOSE. To study the relative impact of genetic and environmental factors on the variability of intraocular scattering within a classical twin study. METHODS.A total of 64 twin pairs, 32 monozygotic (MZ) (mean age: 54.9 6 6.3 years) and 32 dizygotic (DZ) (mean age: 56.4 6 7.0 years), were measured after a complete ophthalmologic exam had been performed to exclude all ocular pathologies that increase intraocular scatter as cataracts. Intraocular scattering was evaluated by using two different techniques based on a straylight parameter log(S) estimation: a compact optical instrument based in the principle of optical integration and a psychophysical measurement. Intraclass correlation coefficients (ICC) were used as descriptive statistics of twin resemblance, and genetic models were fitted to estimate heritability. RESULTS.No statistically significant difference was found for MZ and DZ groups for age (P ¼ 0.203), best-corrected visual acuity (P ¼ 0.626), cataract gradation (P ¼ 0.701), sex (P ¼ 0.941), optical log(S) (P ¼ 0.386), or psychophysical log(S) (P ¼ 0.568), with only a minor difference in equivalent sphere (P ¼ 0.008). Intraclass correlation coefficients between siblings were similar for scatter parameters: 0.676 in MZ and 0.471 in DZ twins for optical log(S); 0.533 in MZ twins and 0.475 in DZ twins for psychophysical log(S). For equivalent sphere, ICCs were 0.767 in MZ and 0.228 in DZ twins. Conservative estimates of heritability for the measured scattering parameters were 0.39 and 0.20, respectively. CONCLUSIONS.Correlations of intraocular scatter (straylight) parameters in the groups of identical and nonidentical twins were similar. Heritability estimates were of limited magnitude, suggesting that genetic and environmental factors determine the variance of ocular straylight in healthy middle-aged adults.
Intraocular scattering affects fundus imaging in a similar way that affects vision; it causes a decrease in contrast which depends on both the intrinsic scattering of the eye but also on the dynamic range of the image. Consequently, in cases where the absolute intensity in the fundus image is important, scattering can lead to a wrong estimation. In this paper, a setup capable of acquiring fundus images and estimating objectively intraocular scattering was built, and the acquired images were then used for scattering compensation in fundus imaging. The method consists of two parts: first, reconstruct the individual's wide-angle Point Spread Function (PSF) at a specific wavelength to be used within an enhancement algorithm on an acquired fundus image to compensate for scattering. As a proof of concept, a single pass measurement with a scatter filter was carried out first and the complete algorithm of the PSF reconstruction and the scattering compensation was applied. The advantage of the single pass test is that one can compare the reconstructed image with the original one and see the validity, thus testing the efficiency of the method. Following the test, the algorithm was applied in actual fundus images in human eyes and the effect on the contrast of the image before and after the compensation was compared. The comparison showed that depending on the wavelength, contrast can be reduced by 8.6% under certain conditions. of the human rod photoreceptor mosaic using a confocal adaptive optics scanning ophthalmoscope," Biomed. Opt.
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