Purpose. Wavefront sensors provide quite useful information on the optical quality of the eye. However, in eyes where very high-order aberrations and scattered light are prominent, wavefront sensors may overestimate retinal image quality. This study showed that, in those cases, the double-pass technique is a complementary tool for better estimation of ocular optical quality. methods. A double-pass (DP) instrument was used, based on recording images of a point source in near-infrared light after reflection in the retina and double-pass through the ocular media. The aberrations were also measured with a prototype of near-infrared Hartmann-Shack (HS) wavefront sensor adapted to the clinical environment. From the wave aberrations, the modulation transfer function (MTF) was calculated (MTF_HS). The MTF was also obtained from the double-pass images (MTF_DP). Both techniques were applied in normal young subjects as the control and in three other groups of eyes: older subjects, after LASIK refractive surgery, and after IOL implantation. results. The MTFs obtained from DP and HS techniques were compared. In the group of normal eyes with low levels of intraocular scattering, these estimates were quite similar, indicating that both techniques captured well most of the optical degradation. However, in eyes where scatter was more predominant (e.g., early cataract, posterior capsular opacification after IOL implantation) the MTF provided by the HS sensor was always higher than the MTF obtained from DP. A single parameter was used to indicate the differences. conclusions. In eyes with low scattering, DP and HS techniques provided similar estimates of the retinal image quality. However, in a patient’s eye with mild to severe amount of scatter, wavefront sensors might overestimate image quality, whereas the DP technique produces a more accurate description of the optical quality, better correlated with the quality of vision.

We describe a new wavefront sensor for ocular aberration determination, based on the curvature sensing principle, which adapts the classical system used in astronomy for the living eye’s measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann–Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.

Heterophoria is the relative deviation of the eyes in absence of fusional vergence. Fusional vergence can be deprived by, for example, occluding one eye while the other fixates a visual target. Then, the occluded eye will presumably deviate from its initial position by an amount that corresponds to the heterophoria. Its assessment in clinical practice is crucial for the diagnosis of non-strabismic binocular dysfunctions such as convergence insufficiency. Traditional clinical methods, like the cover test or the modified Thorington test, suffer from practitioner’s subjectivity, impossibility to observe the occluding eye or unusual viewing conditions. These limitations could be overcome by using eye tracking systems to measure objectively the heterophoria. The main purpose of this study was to compare the performance of an automated and objective method to measure near heterophoria using an eye-tracker with two conventional methods: the cover-uncover test and the modified Thorington test. The eye tracking method gave us the possibility to measure the heterophoria as the deviation of the occluded eye (mimicking the cover test) or as the deviations of the occluded and fixating eyes (adhering to the theoretical definition of heterophoria). The latter method provided smaller results than the former, although on average the differences might not be clinically relevant. The proposed objective method exhibited considerably better repeatability than the two conventional clinical methods. It showed better agreement with the modified Thorington test than with the cover-uncover test, and a similar level of agreement was obtained between the two clinical methods. To conclude, the use of eye-trackers to measure heterophoria provides objective and more repeatable measures. As eye-trackers become common tools in clinical settings, their use to measure heterophoria should be the new gold standard.

Optical imaging systems for noninvasive ocular diagnosis remain crucial to assist ophthalmologists in their daily clinical practice. To promptly diagnose ocular and systemic diseases that manifest early in the retina,^{1 – 4} efforts have focused on the acquisition of good-quality fundus images. Commercial fundus cameras widely used in the clinical setting include digital cameras that produce color images, with only three spectral bands (R, G, and B). As a result, some retinal structures and substances with different spectral signatures associated with specific ocular diseases^5,6 may go undetected due to metamerism or limited spectral range. The capability of identifying these spectral absorption properties in-vivo is key to clinical diagnosis and treatment. Multispectral imaging (MSI) technology, which increases the amount of extractable spectral information from biological tissues using more than three spectral bands, has been used in the last few years to advance the diagnosis of many diseases.^{7 – 10} Newly developed fundus cameras that include MSI hold great promise for the analysis of the retina, since they combine the usefulness of spectroscopy with imaging, thus providing both spectral and spatial information of retinal landmarks. For instance, they can spotlight vascular occlusions, vein hemorrhages, drusen, and exudates, and also build oxygenation maps of the retinal vasculature, contributing in this way to the early diagnosis and treatment of conditions such as age-related macular degeneration (AMD) and diabetic retinopathy.^{11 – 16}