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.

Purpose. To assess the repeatability of the Galilei dual Scheimpflug analyzer (GDSA) in anterior segment examination. Methods. Fifty-two eyes from 52 healthy volunteers were prospectively and consecutively recruited. Anatomic, axial, refractive, and instantaneous parameters were measured with GDSA to provide a complete characterization of the anterior segment. Repeatability was assessed calculating intraclass correlation coefficient (ICC), and coefficient of variation (COV). Results. Correlation among repeated measurements showed almost perfect reliability (ICC > 0.81) for all parameters except thinnest central corneal thickness (CCT) (0.78), corneal thickness average out (0.79), and posterior axial curvature average out (0.60). Repeatability was excellent (COV < 10%) for all parameters except anterior chamber volume and, superior iridocorneal angle and eccentricities. In these last three parameters, repeatability limits were excessively high compared to the mean. Conclusions. GDSA in healthy young persons had an almost perfect correlation in measuring anatomic, axial, instantaneous, and refractive parameters with greater variability for peripheral terms. Repeatability of anatomical parameters like pachymetry, anterior chamber, or iridocorneal angle and eccentricity were limited. In healthy young persons, the other evaluated parameters had very good repeatability and their limits of agreement showed excellent clinical results for this device.

This study assessed anterior chamber parameters in healthy young adults using spectral-domain optical coherence tomography. This technique reveals the spatial relationships of the ocular structures, provides high-resolution images, and results in high degrees of intraobserver and interobserver repeatabilities.

Purpose To evaluate the relationship between intraocular pressure (IOP) measurements and corneal biomechanical parameters obtained with Ocular Response Analyser (ORA) in healthy subjects. Methods Sixty‐five eyes from 65 healthy subjects were prospective and consecutively selected. All of them underwent a full optometric examination, including central corneal thickness (CCT) and IOP measured with ORA: ORA Goldmann‐corrected IOP (IOPg) and ORA corneal resistance‐corrected IOP (IOPcc). Pearson correlation coefficients between IOP values and corneal biomechanics parameters obtained by ORA were also calculated. Results IOP parameters, evaluated by Pearson correlation coefficients were significantly correlated with p<0.001; r=0.826 for IOPcc‐IOPg. IOPg was linearly associated with corneal resistance factor (CRF; r=0.619) and with CCT (r=0.579). IOPcc had a linear relationship with CH (r=‐0.482); similar results were obtained with CRF and corneal hysteresis (CH; r=0.841), CRF and CCT (r=0.681) or between CH and CCT (r=0.466). Conclusion IOPcc and IOPg have a positive linear correlation. ORA biomechanics parameters CRF, CH and CCT show also a linear positive relation between them.

Purpose To study the relationship between visual acuity (VA) and fluctuation of accommodation and aberrometric data in a population of no presbyopic eyes. Methods Forty‐two no presbyopic eyes with natural pupil and scotopic lighting conditions were involved in the study. Subjects were studied with an autorefractor to determine the refraction and accommodation fluctuations, a ray tracing aberrometer to measure the refraction as well as aberrometric data, and a system to generate charts and determine the subjective refraction and the AV. The equipments were calibrated with an artificial eye before the tests were done. The subjects were divided in several subgroups of 1) subjective refraction (≥|‐0.50|D or <|‐0.50|D); 2) fluctuation of accommodation (≤0.1D or >0.1D) and 3) RMS of different high order (HO) aberrations: 3a) RMS of HO total (≤0.25µm or >0.25µm), 3b) RMS of spherical aberration (≤0.15µm or >0.15µm), 3c) RMS of coma (≤0.15µm or >0.15µm) and 2d) RMS of trefoil (≤0.15µm or >0.15µm) Results The mean value for VA was 1.28 and 0.16 D for fluctuations of accommodation. No significant differences among fluctuations of accommodation and VA were found in any group. We found normal values about RMS of HO (0.34 μm), RMS of coma (0.19 μm), RMS of trefoil (0.17 μm) and spherical aberration (0.11 μm). No differences between RMS and VA were found in any group. A moderate correlation (R2=0.19) between the VA and the spherical aberration was observed. Conclusion The values of fluctuation of accommodation and aberrometric data were within normal ranges reported in the literature. Differences between VA and other optical parameters were not found.

SIGNIFICANCE: Ocular light exposure therapy has been used in optometric therapies to improve binocular anomalies such as accommodative or vergence dysfunctions, amblyopia therapy or to increase the visual field. Currently, syntonic phototherapy is used worldwide by behavioral optometrists, vision trainers, or occupational therapists, among others, although these treatments are supported by only a few research studies that lack consensus on the efficacy of this approach. PURPOSE: In this article, we highlight the optical characteristics of lamps without evaluating the efficacy of their use in optometric procedures.METHODS: Our work analyzes four devices often used in clinical practice in terms of spectral power distribution, illuminance levels at the corneal plane, and both theoretical photopic and melanopic contributions to the visual system.RESULTS: First, illuminance levels reaching the corneal plane depend on the characteristics of each lamp and their distance from where the eye should be positioned; for example, delta-theta filter photopic illuminance is 13.1, 93.7, 22.7, or 41.6 lux with the four evaluated devices. Second, filters or modes named the same differ in terms of their spectral power distribution. Third, substantial difference in color appearance has been found among the same configurations. CONCLUSIONS:The spectral and iluminance characteristics of syntonic systems used for vision therapy vary widely, including variations among filters with the same identifying characteristics. This provides significant sources of variability, which limit the ability to conduct evidence-based medicine clinical trials to assess the true efficacy of syntonic therapy. This study furthers our knowledge of syntonic phototherapy from a technical perspective; however, longitudinal research examining patients' evolution pre-lighting and post-lighting treatments is required to justify and understand the effects of light exposure and its impact on optometric and ocular parameters more clearly.