Bart Jaeken

Optical Quality of Emmetropic and Myopic Eyes in the Periphery Measured with High-Angular Resolution

PURPOSE On average, myopic eyes present a relative hyperopia in the peripheral retina. This has been associated with the possibility that by modifying the peripheral refraction, the progression of central myopia could be controlled. The authors explored how refractive errors and optical aberrations interact in the formation of the retinal image in the periphery, in eyes with different central refractions. METHODS The authors used a fast and high-angular resolution scanning wavefront sensor to measure the optical image quality of the eye in the horizontal meridian (± 40°) in 202 eyes of 101 subjects, 54 males and 47 females with an average age (std) of 27.5 (± 7.2) years and an average foveal refraction (std) of -0.8 (± 1.3 D) of which 64 were non-myopes (refraction ± std: 0.01 ± 0.46 D) and 37 myopes (-2.12 ± 1.08 D). They evaluated the relationship between peripheral optical properties and central refraction using different metrics. RESULTS The authors observed a significant tendency to a relative hyperopia in the periphery of the myopic eyes. The relative peripheral refraction (RPR) was significantly different between the emmetropic and myopic eyes from 15°-40° temporal retina and from 20°-40° nasal retina. The mean RPR metric correlated with the central refraction of the subject (r = -0.552 / -0.560 [OD / OS]). The image quality presented only minor differences between the various refractive groups at angles of 30°-40° when the central refraction was corrected. CONCLUSIONS Peripheral overall blur is mostly influenced by the interaction of defocus and oblique astigmatism, and at larger eccentricities is similar for the different refractive groups. This could argue against the hypothesis that a relative peripheral hyperopia could drive eyes toward myopia.

Fast scanning peripheral wave-front sensor for the human eye

We designed and built a fast scanning peripheral Hartmann-Shack (HS) wave-front sensor to measure the off-axis wave-front aberrations in the human eye. The new instrument is capable of measuring the optical quality over the central 80° horizontal visual field in 1.8 seconds with an angular resolution of 1°. The subject has an open field of view without any moving elements in the line-of-sight and the head is kept in place by a head-chin rest. The same efficiency, reliability and measurement quality as the current static HS sensor were found but with much higher acquisition speed and comfort for the patients. This instrument has the potential to facilitate and improve future research on the peripheral optical quality of the eye in large groups of subjects.

Evaluating the peripheral optical effect of multifocal contact lenses

Multifocal soft contact lenses have been used to decrease the progression of myopia, presumably by inducing relative peripheral myopia at the same time as the central image is focused on the fovea. The aim of this study was to investigate how the peripheral optical effect of commercially available multifocal soft contact lenses can be evaluated from objective wavefront measurements.

Peripheral aberrations in the human eye for different wavelengths: off-axis chromatic aberration

The interest in the eyes off-axis aberrations has increased strongly. On-axis the conversion of the aberration magnitude between different wavelengths is well known. We verified if this compensati ...

Wide-field optical model of the human eye with asymmetrically tilted and decentered lens that reproduces measured ocular aberrations

Eye models are valuable tools that can help delineate the role of anatomical parameters on visual performance and guide the design of advanced ophthalmic instrumentation. We propose an optically accurate wide-field schematic eye that reproduces the complete aberration profile of the human eye across a wide visual field. The optical performance of the schematic eye is based on experimentally measured wavefront aberrations taken with a four mm pupil for the central 80° of the horizontal meridian (101 eyes) and 50° of the vertical meridian (10 eyes). Across the entire field of view, our model shows excellent agreement with the measured data both comprehensively and for low-order and high-order aberrations. In comparison to previous eye models, our schematic eye excels at reproducing the aberrations of the retinal periphery. Also unlike previous models, tilt and decentering of the gradient refractive index crystalline lens, which arose naturally through the optimization process, permits our model to mimic the asymmetries of real human eyes while remaining both anatomically and optically correct. Finally, we outline a robust reverse building eye modeling technique that is capable of predicting trends beyond those defined explicitly in the optimization routine. Our proposed model may aid in the design of wide-field imaging instrumentation, including optical coherence tomography, scanning laser ophthalmoscopy, fluorescence imaging, and fundus photography, and it has the potential to provide further insights in the study and understanding of the peripheral optics of the human eye.

Comparison of the Optical Image Quality in the Periphery of Phakic and Pseudophakic Eyes

PURPOSE The natural lens may provide some compensatory optical effect in the periphery. When it is substituted by an IOL during cataract surgery, the quality of the peripheral optics will be modified. We compared the peripheral image quality in the eyes of patients with one eye implanted with a monofocal IOL and the fellow eye still with the natural precataract lens. METHODS We used a scanning peripheral Hartmann-Shack wavefront sensor to measure the central 80° of visual angle along the horizontal meridian. Twelve patients with ages ranging between 65 to 81 years were evaluated. The results of the phakic and pseudophakic eyes were compared using the spherical equivalent, astigmatism, higher order aberrations, and the Strehl ratio. The statistical differences at each angle between the two eyes were evaluated. RESULTS In the eyes implanted with IOLs, the peripheral mean spherical equivalent was slightly more myopic than in the phakic eyes, although the differences were only significant for some angles. Astigmatism increased much faster in the periphery for the pseudophakic eyes as compared with the phakic eyes. The mean values were significantly different from 9° and 17° outwards at the temporal and nasal retina, respectively. As an example, at 30°, eyes implanted with IOLs presented 1.5 diopters (D) of additional astigmatism. The higher order aberrations were not significantly different between the two groups. CONCLUSIONS Eyes implanted with monofocal IOLs present more astigmatism in the periphery than the healthy older eyes. This suggests that the crystalline lens provides a beneficial effect to partially compensate off-axis astigmatism. The degradation of the peripheral retinal image may reduce the pseudophakic patients performance in common visual tasks.

Symmetries in peripheral ocular aberrations

A mirror symmetry in the aberrations between the left and right eyes has previously been found foveally, but while a similar symmetry for the peripheral visual field is likely, it has not been investigated. Nevertheless, the peripheral optical quality is often evaluated in only one eye, because it is more time efficient than analyzing the whole visual field of both eyes. This study investigates the correctness of such an approach by measuring the peripheral wavefront aberrations in both eyes of 22 subjects out to ±40° horizontally. The largest aberrations (defocus, astigmatism, and coma) were found to be significantly correlated between the left and right eyes when comparing the same temporal or nasal angle. The slope of the regression line was close to ±1 (within 0.05) for these aberrations, with a negative slope for the horizontally odd aberrations, i.e. the left and right eyes are mirror symmetric. These findings justify that the average result, sampled in one of the two eyes of many subjects, can be generalized to the other eye as well.

Comparison of two scanning instruments to measure peripheral refraction in the human eye

To better understand how peripheral refraction affects development of myopia in humans, specialized instruments are fundamental for precise and rapid measurements of refraction over the visual field. We compare here two prototype instruments that measure in a few seconds the peripheral refraction in the eye with high angular resolution over a range of about ±45 deg. One instrument is based on the continuous recording of Hartmann-Shack (HS) images (HS scanner) and the other is based on the photorefraction (PR) principle (PR scanner). On average, good correlations were found between the refraction results provided by the two devices, although it varied across subjects. A detailed statistical analysis of the differences between both instruments was performed based on measurements in 35 young subjects. Both instruments have advantages and disadvantages. The HS scanner also provides the high-order aberration data, while the PR scanner is more compact and has a lower cost. Both instruments are current prototypes, and further optimization is possible to make them even more suitable tools for future visual optics and myopia research and also for different ophthalmic applications.