Peripheral Refraction Measurements Research Articles

Study of peripheral blur in retinal electrical activity

Aims/Purpose: The aim of this study was to evaluate changes in peripheral refraction by the use of a contact lens to control the progression of myopia. In addition, the response of electrophysiological activity in different areas of the retina with and without contact lens was also determined.Methods: We recruited 7 myopic individuals (23.71 ± 5.41 years) with refraction up to −4.50D (spherical equivalent), without eye pathologies and surgeries. Visual acuity was recorded, high and low contrast, with the updated refraction and with the Misight 1 Day contact lens. Peripheral refraction measurements were obtained using an open‐field autorefractometer. Multifocal electrophysiology measurements were performed binocularly with and without contact lens, with dilated pupil. Topography and aberrometry values were also recorded.Results: lens, peripheral refractions become significantly more myopic. The change in peripheral refraction induced at 30° Nasal is −0.66D. High Contrast Visual Acuity was always superior to Low Contrast VA in both conditions. The Misight 1 Day contact lens manifests a different behaviour along the anterior surface of the cornea. LC induces a significant increase in high‐order aberrations, especially in comatic aberrations, which increase three times their initial value.Conclusions: Regarding the electrophysiological response of the retina, with the use of the LC Misight 1 Day, it presented a greater implicit time and amplitude of the P1 component, in the superior temporal retina, these differences being statistically significant. The implicit time of the P2 component increased in the temporal retina and in the retinal area delimited by Rings 3, 4 and 5.

Peripheral Refraction Validity of the Shin-Nippon SRW5000 Autorefractor.

To investigate the operation of the Shin-Nippon/Grand Seiko autorefractor and whether higher-order aberrations affect its peripheral refraction measurements. Information on instrument design, together with parameters and equations used to obtain refraction, was obtained from a patent. A model eye simulating the operating principles was tested with an optical design program. Effects of induced defocus and astigmatism on the retinal image were used to calibrate the model eye to match the patent equations. Coma and trefoil were added to assess their effects on the image. Peripheral refraction of a physical model eye was measured along four visual field meridians with the Shin-Nippon/Grand Seiko autorefractor SRW-5000 and a Hartmann-Shack aberrometer, and simulated autorefractor peripheral refraction was derived using the Zernike coefficients from the aberrometer. In simulation, the autorefractor's square image was changed in size by defocus, into rectangles or parallelograms by astigmatism, and into irregular shapes by coma and trefoil. In the presence of 1.0 D oblique astigmatism, errors in refraction were proportional to the higher-order aberrations, with up to 0.8 D sphere and 1.5 D cylinder for ±0.6 μm of coma or trefoil coefficients with a 5-mm-diameter pupil. For the physical model eye, refraction with the aberrometer was similar in all visual field meridians, but refraction with the autorefractor changed more quickly along one oblique meridian and less quickly along the other oblique meridian than along the horizontal and vertical meridians. Simulations predicted that higher-order aberrations would affect refraction in oblique meridians, and this was supported by the experimental measurements with the physical model eye. The autorefractor's peripheral refraction measurements are valid for horizontal and vertical field meridians, but not for oblique field meridians. Similar instruments must be validated before being adopted outside their design scope.

New Perspective on Myopia Control with Orthokeratology.

To compare peripheral refraction along both the horizontal and vertical retinal meridians before and after orthokeratology (OK) lens wear. Nineteen young adult myopic subjects (mean age, 28 ± 7 years) were fitted with OK lenses in both eyes. Central and peripheral refraction and corneal topography measurements were taken before and after 14 nights of OK. All measurements were taken with no correction or OK lens in place. At baseline before OK, peripheral spherical equivalent refraction (M) across the horizontal meridian did not vary significantly from center. M across the vertical meridian was more myopic than the center (p < 0.05). After OK, there was a significant hyperopic shift in M (p < 0.001); both meridians now experienced myopic peripheral refraction. At baseline, J180 across the horizontal meridian was more negative than the center, and along the vertical meridian, it was more positive than the center (all p < 0.05). At baseline, J45 was more positive than center with increased eccentricity in the temporal and inferior retina and more negative than center with increased eccentricity in the nasal and superior retina. Orthokeratology caused greater rate of change of peripheral J180 across both retinal meridians (p < 0.001). Furthermore, compared with baseline, J45 became more positive in the nasal and superior retina and more negative in the temporal and inferior retina (all p < 0.05). Orthokeratology lenses induced significant changes in peripheral refraction along the horizontal and vertical meridians. As peripheral myopia was measured at baseline along the vertical meridian, the results of our study suggest that inducing greater degrees of myopic defocus on to the peripheral retina, more than habitually experienced, may be required for effective myopia control. Further investigation into the critical threshold of retinal area receiving myopic defocus and the impact of duration of exposure is necessary to improve the efficacy of current myopia control treatments.

The BHVI-EyeMapper: peripheral refraction and aberration profiles.

ABSTRACTPurposeThe aim of this article was to present the optical design of a new instrument (BHVI-EyeMapper, EM), which is dedicated to rapid peripheral wavefront measurements across the visual field for distance and near, and to compare the peripheral refraction and higher-order aberration profiles obtained in myopic eyes with and without accommodation.MethodsCentral and peripheral refractive errors (M, J180, and J45) and higher-order aberrations (C[3, 1], C[3, 3], and C[4, 0]) were measured in 26 myopic participants (mean [±SD] age, 20.9 [±2.0] years; mean [±SD] spherical equivalent, −3.00 [±0.90] diopters [D]) corrected for distance. Measurements were performed along the horizontal visual field with (−2.00 to −5.00 D) and without (+1.00 D fogging) accommodation. Changes as a function of accommodation were compared using tilt and curvature coefficients of peripheral refraction and aberration profiles.ResultsAs accommodation increased, the relative peripheral refraction profiles of M and J180 became significantly (p < 0.05) more negative and the profile of M became significantly (p < 0.05) more asymmetric. No significant differences were found for the J45 profiles (p > 0.05). The peripheral aberration profiles of C[3, 1], C[3, 3], and C[4, 0] became significantly (p < 0.05) less asymmetric as accommodation increased, but no differences were found in the curvature.ConclusionsThe current study showed that significant changes in peripheral refraction and higher-order aberration profiles occurred during accommodation in myopic eyes. With its extended measurement capabilities, that is, permitting rapid peripheral refraction and higher-order aberration measurements up to visual field angles of ±50 degrees for distance and near (up to −5.00 D), the EM is a new advanced instrument that may provide additional insights in the ongoing quest to understand and monitor myopia development.

Peripheral Refractive Changes Associated with Myopia Progression

To evaluate the changes in peripheral refraction profiles associated with myopia progression and treatment modalities used in the Cambridge Anti-Myopia Study. one hundred and seventy-seven myopes in the age range of 14 to 22 years were enrolled in the study. The mean spherical equivalent refractive error was 3.12 1.87 diopters (D) and the refractive error of each participant was corrected with contact lenses. The participants were randomly assigned to one of four treatment groups, which included: altered spherical aberration and vision training, altered spherical aberration only, vision training only, and control. Peripheral refractive error was measured using an open field autorefractor in the central 60° of the retina in 10° steps. The refractive error was measured using cycloplegic autorefraction. Two-year refractive progression data and initial peripheral refraction measurements were available in 113 participants. Measurements of peripheral refraction and cycloplegic refraction were obtained at three visits over 2 years in 12-month intervals for 92 participants. All subjects showed a relative peripheral hyperopia, especially in the nasal retina. A limited magnitude of myopia progression of -0.34 ± 0.36 D over 2 years was found in each of the four groups on average. There were no significant differences in the rate of progression between any of the treatment groups (P > 0.05). Initial peripheral J45 astigmatic refractive error at 20° and 30° in the nasal retina was weakly correlated with progression of myopia over 2 years (r = -0.27, P = 0.004 and r = -0.20, P = 0.040, respectively; n = 113). The change in spherical equivalent peripheral refractive error at 30° nasal retina over time was also significantly correlated with progression of myopia especially at 24 months (r = -0.24, P = 0.017, n = 92). Relative peripheral hyperopia is associated with myopia. Myopia progression may be weakly linked to changes in the peripheral refraction profiles in the nasal retina. However, a causative link between peripheral refractive error and myopia progression could not be established.

Repeatability of Relative Peripheral Refraction in Untreated and Orthokeratology-Treated Eyes

To determine the repeatability of relative peripheral refraction (RPR) measurements using an open-view automatic refractor in untreated and orthokeratology (ortho-k)-treated eyes of children. Cycloplegic central (CR) and peripheral refraction (PR) across the central 60° horizontal field at 10° intervals were measured in children (6-9 years) using a Shin-Nippon NVision K5001 autorefractor. In experiment 1, measurements were repeated at the same visit for 59 untreated (right) eyes, whereas in experiment 2, measurements were repeated at the same visit and another visit (1-2 weeks apart) for 24 ortho-k-treated (right) eyes to determine the intra- and intervisit repeatability, respectively. Measurements were transposed into M, J0, and J45 vectors, and RPR were calculated by subtracting central refraction from PR values. Intra- and intervisit differences and coefficients of repeatability (COR) of RPR were determined. The mean intravisit differences in RPR for all three vectors were ≤0.05 D for untreated eyes, and both intra- and intervisit differences in RPR were ≤0.32 D for ortho-k-treated eyes. No significant intra- and intervisit differences in RPR were found at any field angle in this study. COR of measurements were <±0.71 D in the untreated eyes, and <±1.25 D (intravisit) and <±3.00 D (intervisit) in ortho-k-treated eyes. The COR increased with field angles in all situations and were greater in ortho-k-treated than in untreated eyes. In ortho-k-treated eyes, intervisit COR of measurements beyond central 40° field were larger than the intravisit COR. The mean intra- and intervisit differences of RPR measurements were small in both untreated and ortho-k-treated eyes. Variability of PR measurements increased with field angle and with ortho-k treatment.

Correction of peripheral refractive errors and its impact on visual performance

AbstractPurpose There has been considerable recent interest in modifying peripheral refraction for the purpose of treating myopia. Correcting peripheral refraction can affect peripheral visual performance. The purpose of this study was to consider the extent of such improvement and the feasibility of making spectacle lenses for this purpose.Methods Peripheral refraction was used as a basis for designing lenses to correct refraction out to 30 degrees along the horizontal meridian. Visual performance tests were conducted at 20 degrees nasal, 30 degrees nasal and 25 degrees temporal visual field. Tests were detection acuity for high contrast sinusoidal gratings and contrast thresholds for 1 min arc diameter spots.Results Correcting peripheral vision has limited influence on visual acuity as this and other resolution‐like tasks are limited more by retinal sampling than by image quality. However, Lewis et al (ARVO abstract 2012) found that correcting vision at 20 degrees nasal visual field could improve low contrast resolution acuity by an average of 0.06 log unit and up to 0.16 log unit for people with large off‐axis astigmatism. Detection tasks, such as deciding in which of two presentations a grating appears without necessarily being resolvable, give up to 0.7 log unit (5 times) better acuity than resolution tasks at 20 deg N, but are sensitive to defocus such that performance reduces close to those of resolution tasks with about 2 D defocus (Wang et al, IOVS 1997). Results like the above indicate the potential value of peripheral correction for people with macular lesions. Our own results with specially designed lenses will be presented.Conclusion The lenses were partially successful in improving peripheral vision. Difficulties included variability in peripheral refraction measurements and lack of sensitivity of some subjects to peripheral correction. Whether or not correcting peripheral refractive errors will influence myopia progression is not yet known.

78 The importance of autorefractor alignment for peripheral refraction measurements

78 The importance of autorefractor alignment for peripheral refraction measurements

Cross-sectional Sample of Peripheral Refraction in Four Meridians in Myopes and Emmetropes

The study of peripheral refractive error is of growing interest as degradation of the retinal image quality in the periphery is known to affect central refractive error development and ocular shape in animal models. The purpose of this study was to measure peripheral refraction across the horizontal, vertical, and two oblique meridians in a group of myopic and emmetropic adults and to investigate retinal asymmetry in the human retina. Thirty-one myopes (spherical equivalent between -2.00 and -9.62 D) and 20 emmetropes (spherical equivalent between -0.50 and +0.50 D) with astigmatism less than -0.75 D, participated in the project. Noncycloplegic peripheral refraction measurements were captured with an autorefractor (NVision K-5001; Shin-Nippon, Tokyo, Japan) at the fovea and up to 30° eccentricity in the horizontal, vertical, and two oblique meridians in 10° steps. RPR was calculated by subtracting the foveal spherical equivalent refraction from that obtained at each eccentric location. Along all measured meridians, myopic eyes showed a relative hyperopic shift in the periphery, with the superior-temporal portion of the retina exhibiting the smallest shift. Emmetropic eyes, however, exhibited a relatively consistent refractive profile across all meridians and eccentricities, confirming a spherical retinal shape for this group. In addition, off-axis astigmatism increased with eccentricity in all meridians. These results suggest that the myopic eye tends toward an ellipsoid shape, rather than the globular shape of an emmetropic eye.

The effect of instrument alignment on peripheral refraction measurements by automated optometer

Interest in peripheral refraction measurement has grown in recent years in response to the insight it may provide into myopia development. In light of the likely increase in the clinical use of open-field autorefractors for peripheral refraction measurements, the question of instrument alignment and its impact on the accuracy of refraction measurements is raised. The aim of this study was to investigate the accuracy and precision when an open-field device was moved away from alignment with the corneal reflex towards the pupil margins, and to determine the optimum alignment position for peripheral refraction measurements. Autorefractions were performed on the right eyes of 10 healthy participants using the Shin-Nippon NVision-K 5001 autorefractor. At least five measurements were taken with the subject fixating a distance target in the primary position of gaze, and then four peripheral fixation targets located along the horizontal meridian (10° and 20° eccentricities in the nasal and temporal retina). Measurements were taken at seven alignment positions across the pupil for each fixation angle. Refraction was recorded as the spherical and cylindrical power. The central objective refraction achieved under cycloplegia based on the autorefraction result for the whole sample, ranged between -5.62 D and +1.85 D for the value of sphere, with a maximum astigmatism of -1.00 D. Acceptable alignment position range varied with fixation angle but was -1.0 to +1.0 mm in width across the pupil. Peripheral refraction measurements centred on the entrance pupil were as reliable as those centred on the corneal reflex. Our data suggest that for peripheral refraction measurements, there is a range of acceptable positions and operators can be confident of the validity of results obtained if aligned half way between the pupil centre and corneal reflex. The alignment becomes more critical at greater eccentricities.

Effect of Orthokeratology on Peripheral Aberrations of the Eye

To investigate the effect of orthokeratology on peripheral aberrations in two myopic volunteers. The subjects wore reverse geometry orthokeratology lenses overnight and were monitored for 2 weeks of wear. They underwent corneal topography, peripheral refraction (out to +/-34 degrees along the horizontal visual field) and peripheral aberration measurements across the 42 degrees x 32 degrees central visual field using a modified Hartmann-Shack aberrometer. Spherical equivalent refraction was corrected for the central 25 degrees of the visual fields beyond which it gradually returned to its preorthokeratology values. There were increases in axial coma, spherical aberration, higher order root mean square aberrations, and total root-mean-squared aberrations (excluding defocus). The rates of change of vertical and horizontal coma across the field changed in sign. Total root mean square aberrations showed a quadratic rate of change across the visual field which was greater subsequent to orthokeratology. Although orthokeratology can correct peripheral relative hypermetropia it induces dramatic increases in higher-order aberrations across the field.

The influence of oblique viewing on axial and peripheral refraction for emmetropes and myopes

Refraction may be affected by the forces of lids and extraocular muscles when eye direction and head direction are not aligned (oblique viewing) which might potentially influence past findings on peripheral refraction of the eye. We investigated the effect of oblique viewing on axial and peripheral refraction. In a first experiment, cycloplegic axial refractions were determined when subjects' heads were positioned to look straight-ahead through an open-view autorefractor and when the heads were rotated to the right or left by 30 degrees with compensatory eye rotation (oblique viewing). Subjects were 16 young emmetropes (18-35 years), 22 young myopes (19-36 years) and 15 old emmetropes (45-60 years). In a second experiment, cycloplegic peripheral refraction measurements were taken out to +/-34 degrees horizontally from fixation while the subjects rotated their heads to match the peripheral refraction angles (eye in primary position with respect to the head) or the eyes were rotated with respect to the head (oblique viewing). Subjects were 10 emmetropes and 10 myopes. We did not find any significant changes in axial or peripheral refraction upon oblique viewing for any of the subject groups. In general for the range of horizontal angles used, it is not critical whether or not the eye is rotated with respect to the head during axial or peripheral refraction.

Aberrations of emmetropic subjects at different ages

We made on-axis aberrations and horizontal peripheral refraction measurements of emmetropic subjects (spherical equivalent −0.88 D to +0.75 D) aged between 19 and 70 years. We found smaller changes in on-axis aberrations with age than has previously been reported, possibly because of the small refractive error range of our subject group. Higher order root-mean-squared aberrations increased by 26% across the age range (5 mm pupils), with significant age related changes in 4th- and 6th-order aberrations. The only aberration co-efficient to change significantly was horizontal coma co-efficient C(3, 1). Several aberration co-efficients were significantly different from zero across the group of subjects. The only changes in peripheral refraction with increase in age were shifts in the turning points of the spherical equivalent and horizontal/vertical astigmatism towards less temporal visual field angles.

Validation of aberrometry‐based relative peripheral refraction measurements

To validate aberrometry-based relative peripheral refraction (RPR) measurements and to examine RPR differences in the nasal and temporal horizontal visual field. Thirty subjects underwent cycloplegia in the right eye. Ten measurements each were made centrally, 30 degrees nasally on the retina and 30 degrees temporally on the retina using the Complete Ophthalmic Analysis System (COAS) aberrometer and the Grand Seiko WR-5100K autorefractor in random order. A 2-mm COAS analysis diameter was used to approximate the Grand Seiko autorefractor measurement beam diameter. Nasal and temporal RPR were calculated as the difference between the average nasal or temporal spherical equivalent and the average central spherical equivalent. Repeated measures ANOVAs were used to test for significant differences between the RPR readings of each instrument in each retinal location (nasal or temporal) and to examine refractive error in each direction of gaze for both instruments. Central spherical equivalent refractive error as measured by the Grand Seiko autorefractor ranged from +0.63 D to -8.41 D (mean +/- S.D. = -2.63 D +/- 2.05 D). There were no significant differences between the instruments for RPR measurements (p = 0.34). The nasal RPR was significantly more hyperopic than the temporal RPR (mean +/- S.D. = +0.45 D +/- 1.04 D, p = 0.02). Spherical equivalent refractive error in all directions of gaze was more myopic with the COAS than with the Grand Seiko autorefractor (mean +/- S.D. = -0.41 D +/- 0.61 D, p < 0.0001). RPR measurements with the COAS are feasible and equivalent to those made with the Grand Seiko autorefractor. The COAS can be used to simultaneously collect RPR and peripheral aberration data. Nasal and temporal RPR measurements were significantly different in our sample.