This study establishes a normal database for corneal thickness and all its layers in healthy young adults with spectral-domain optical coherence tomography. This device exhibited a high degree of intraobserver repeatability and interobserver reproducibility for all regions except Bowman's layer.

PURPOSE. We evaluated the photoreceptor response of pigmented P23H and normal pigmented Long Evans (LE) rats over time using functional tests in variable lighting conditions. METHODS.Pigmented P23H rats were studied by optomotor testing and electroretinogram (ERG) recordings at P30, P150, and P240. Pigmented LE rats were used as a normal wild-type control. Stimuli were modified with colored filters. Neutral density filters were used to reduce luminance.RESULTS. Age-related decreases in visual acuity (VA) and contrast sensitivity (CS) were observed in P23H rats. Good correlations in measurements without filter and with green filter were observed between LE and P23H P30 rat values. Differences between groups were smaller with red and purple filters. A strong relationship with luminance was observed in LE rats (VA and CS) and with P23H P30 rats (CS). A decline in the ERG responses of P23H rats was consistent with the gradual loss of photoreceptors. Differences in a-and b-wave amplitudes with different colored filters were negligible with the exception of the red filter, which resulted in smaller responses.CONCLUSIONS. Visual function parameters decreased with age in pigmented P23H rats. Irrespective of luminance, color filter, and retinal degeneration, minimum thresholds of VA and CS were found. Smaller differences than expected were found using color filters. Responses to functional tests at long wavelengths were observed, where there is very low photoreceptor spectral sensitivity. The use of filters with functional testing could minimize light-induced retinal damage in rats.Keywords: P23H, retinitis pigmentosa, optokinetic tracking, electroretinogram R ats are nocturnal animals with a rod-dominated retina. However, their retina also contains a small number of cones.1 Rats maintain an order of magnitude difference in the numbers of cones with maximum sensitivity in the short wavelength (S-cones, with a peak of 358 nm) compared to the middle and long wavelengths (ML-cones, peaking at approximately 509 nm).2,3 Middle and long wavelength cones constitute approximately 90% of cones; the other 10% are Scones that are thought to be UV-sensitive elements, but they probably do not appreciably contribute to the photopic system of the rat. 4 The maximum responses of the two types of cones and rods of rats have been widely studied by electroretinography (ERG), however the contribution of each type of cone to the visual system is not clear. 3,5 Retinitis pigmentosa (RP) is the most common form of inherited photoreceptor degeneration. 6,7 It comprises a group of diseases characterized by a progressive anatomical and functional loss of rod and cone photoreceptors.8 Autosomal dominant RP is responsible for most RP cases, 9 and most cases are due to rhodopsin mutations. Cones are lost after the rod degeneration. The transgenic albino P23H rat is a well-studied model of autosomal dominant RP. In pigmented RP rodent models, a progressive deterioration also occurs in retinal function and anatomy. Because an important role of retinal...

Purpose. To assess the normal values and the repeatability of the Galilei Dual Scheimpflug Analyzer (GDSA), the biometer IOL Master, and the autokerato/refractometer WAM 5500 in anterior segment examinations. Methods. Eighty-eight eyes from 88 healthy volunteers were prospectively and consecutively recruited. The repeatability was assessed, calculating the intraclass correlation coefficient (ICC). Results. The correlations among the repeated measurements showed nearly perfect reliability (ICC > 0.81) for all of the parameters, except corneal astigmatism Galilei (0.79) and WAM (0.68). There were statistically significant differences (P < 0.001) between the values of the flat simulated keratometry (SimK) and the steep SimK measured by GDSA and the other methods; however, there were no statistically significant differences for the values obtained with the IOL Master and WAM 5500 (P = 0.302 and P = 0.172, resp.) or between the values of the ACD (P < 0.001) and WTW (P = 0.007) measured by the IOL Master and GDSA. Conclusions. The anterior segment measurements from the IOL Master and WAM 5500 were highly repeatable, comparable, and well correlated. In healthy young persons, the evaluated parameters had very good repeatability, although significant differences were found between the GDSA and IOL Master and between the GDSA and WAM 5500.