Repeatability of topographic and aberrometric measurements at different accommodative states using a combined topographer and open-view aberrometer

Spherical aberrations and their role in modern ophthalmology

Spherical aberration is an imperfection of the optical system of the human eye. The role of spherical aberration of the human eye in the quality of vision and pseudoaccommodation is reviewed. Spherical aberration is an imperfection of the optical system of the human eye. In most cases, due to well-developed neuroadaptation, it is insignificant for the perception of the image. Nevertheless, its role in modern ophthalmology is far from straightforward. On the one hand, there are clinical scenarios in which an excess of spherical aberration degrades the retinal image and leads to a high dissatisfaction rate among patients.©Recently, there is a growing interest in the modulation of spherical aberration in the clinical setting. Modern intraocular lenses as well as laser refractive procedures are aimed at interfering with spherical aberrations of the optical system in order to increase range of pseudoaccommodation. Here, we review the role of spherical aberration of the human eye in the quality of vision and pseudoaccommodation.

The effect of different optical zone diameters on the results of high-order aberrations in femto-laser-assisted in situ keratomileusis

PURPOSE

To evaluate the postoperative high-order aberration differences of femto-LASIK surgery in 6.5 and 7 mm optic zones.

PATIENTS AND METHODS

We retrospectively reviewed 80 eyes of 40 patients with myopia or myopia with astigmatism who underwent femtosecond LASIK surgery. Q values, z3, 3 (h. trefoil), z3, -3 (v. trefoil), z3, 1 (h. coma), z3, -1 (vertical coma), z4, 0 (spherical aberration), z5, -1 (second other v. coma), aberration coefficients were evaluated 3 months after surgery. Central corneal thicknesses, intraocular pressures, patient ages and genders, optical zone diameters and ablation depths are collected from patients' medical records.

RESULTS

The mean age was 28.4 ± 0.69 years (range, 20-47 years). Lower z4, 0 spherical aberrations and aberration coefficient values were associated with larger optical zones (7 mm) (z4, 0 spherical aberrations = 1.25, p = 0.01; coefficient value = -1.21, p < 0.01). Although a smaller optical zone (6.5 mm) was associated with an increase in most of the wave-front aberration variables, measurements were not statistically different between the two groups other than z4, 0 spherical aberrations and aberration coefficients.

DISCUSSION

LASIK treatment with 6.5 and 7 mm optical zones is safe and effective for correcting myopia and myopic astigmatism and has statistically similar visual outcomes. Moreover, larger optical zone (7 mm) was found to be associated with lower spherical aberration induction and smaller aberration coefficient values compared to 6.5 mm optical zone. This can be important for decision-making in femto-LASIK surgery for better postoperative results.

Clinical evaluation of the repeatability of ocular aberrometry obtained with a new pyramid wavefront sensor

PURPOSE

To evaluate the intrasubject repeatability of the ocular aberrometry obtained with a new ocular pyramidal aberrometer technology in a sample of normal eyes.

METHODS

A total of 53 healthy eyes of 53 subjects with ages ranging from 18 to 45 years were included in this study. In all cases, three consecutive acquisitions were obtained. Intrasubject repeatability of the measurements with a pyramidal aberrometer was calculated. Intrasubject repeatability for 4.0- and 6.0-mm pupils was evaluated within the subject standard deviation (S_w) and intraclass correlation coefficient.

RESULTS

Low values of the S_w and intraclass correlation coefficient outcomes close to 1 were observed for the sphere and cylinder at 3.0-mm pupil size. Most low S_w and intraclass correlation coefficient values close to 1 were observed for total, low-order aberrations and higher-order aberrations root mean square and for each Zernike coefficient analysis (intraclass correlation coefficient ⩾0.798) at 4.0-mm pupil size, with more limited outcomes for the aberrometric coefficient of Z(4, 4) with an intraclass correlation coefficient of 0.683. For a 6.0 mm pupil diameter, low S_w and intraclass correlation coefficient values close to 1 were observed for all aberrometric parameters or Zernike coefficients analyzed (intraclass correlation coefficient ⩾0.850).

CONCLUSION

The new pyramidal aberrometer Osiris provides repeatable and consistent measurements of ocular aberrometry measurements in normal eyes.

[Wavefront and accommodation parameters under different conditions of correction in myopia and hyperopia]

PURPOSE

To compare the wavefront and accommodation parameters without correction and in soft contact lenses (SCL) in natural and cycloplegic conditions in eyes with myopia and hyperopia.

MATERIAL AND METHODS

A total of 142 myopic (mean -5.6±1.4 D) and 48 hyperopic (mean +3.5±1.1 D) eyes were examined in 95 patients aged 5-32 years (mean age 16.9±0.9 years) to compare the wavefront aberrations without correction and with different SCL before and after cycloplegia (two drops of cyclopentolate hydrochloride 1%). The device was set up for 4 mm zone for both narrow and wide pupils. To compare the accommodation parameters under different correction conditions, 85 patients aged 8-23 years (mean age 14.9±0.6 years) with average myopia of (-)5.27±1.4D (123 eyes) and average hyperopia of +3.53±1.2 D (46 eyes) were chosen from the study group. Among the measured parameters are objective accommodative response (OAR), relative accommodation reserves (RAR), pseudoaccumulation amplitude (PA), higher-order aberrations: RMSHOAs, 6-9 Trefoil, 7-8 Coma, spherical aberration (SA).

RESULTS

In myopic eyes with SCL Coma 7 decreases, Coma 8 increases with transition to positive values, and Trefoil 9 increases. In hyperopic eyes, trefoil 6 decreases, Coma 7-8 go negative. In myopic or hyperopic eyes with SCL, SA goes from positive to negative. In both myopia and hyperopia, accommodation and PA rates are higher in SCL than in glasses.

CONCLUSION

SCL change certain wavefront parameters for myopia and hyperopia in different ways. The accommodation parameters in SCL are elevated in both myopia and hyperopia. The negative spherical aberration induced by contact lenses improves the accommodative response. The revealed features should be considered in the development of correction methods that target refractogenesis.

Validation of refraction and anterior segment parameters by a new multi-diagnostic platform (VX120)

BACKGROUND

The VX120 (Visionix Luneau, France) is a novel multi-diagnostic platform that combines Hartmann-Shack based autorefraction, Placido-disk based corneal-topography and anterior segment measurements made with a stationary-Scheimpflug camera. We investigate the agreement between different parameters measured by the VX120 with accepted or gold-standard techniques to test if they are interchangeable, as well as to evaluate the repeatability and reproducibility.

METHODS

The right-eyes of healthy subjects were included in the study. Autorefraction of the VX120 was compared to subjective refraction. Agreement of anterior segment parameters was compared to the Sirius (CSO, Italy) including autokeratometry, central corneal thickness (CCT), iridiocorneal angle (IA). Inter and intra-test repeatability of the above parameters was assessed. Results were analyzed using Bland and Altman analyses.

RESULTS

A total of 164 eyes were evaluated. The mean difference between VX120 autorefraction and subjective refraction for sphere, spherical equivalent (SE), and cylinder was 0.01±0.43D, 0.14±0.47D, and -0.26±0.30D, respectively and high correlation was found to all parameter (r>0.75) except for J₄₅ (r=0.61). The mean difference between VX120 and the Sirius system for CCT, IA, and keratometry (k1 and k2) was -3.51±8.64μm, 7.6±4.2°, 0.003±0.06mm and 0.004±0.04mm, respectively and high correlation was found to all parameter (r>0.97) except for IA (r=0.67). Intrasession repeatability of VX120 refraction, CCT, IA and keratometry yielded low within-subject standard deviations. Inter-session repeatability showed no statistically significant difference for most of the parameters measured.

CONCLUSIONS

The VX120 provides consistent refraction and most anterior segment measurements in normal healthy eyes, with high levels of intra and inter-session repeatability.

Reliability of Ocular Aberration Measurements in Children with Moderate and Low Myopia under Scotopic Conditions

Purpose

To investigate the reliability of ocular aberration measurement in myopic children under scotopic conditions and to validate the mathematical Zernike pupil scaling-down technique.

Methods

Ocular aberrations of 45 myopic children were examined under scotopic conditions via iTrace aberrometer. The intra- and intersession repeatability was evaluated for both the measured values with the true pupil sizes and the estimated ones that were determined by scaling down the pupil sizes to the largest integer value across all measurements.

Results

The intra- and intersession difference of clinically measured aberration was generally insignificant, and the ICCs for each aberration component exhibited good to excellent reliability (ICCs > 0.4). Similar results were found for the estimated aberration using the scaling-down technique. Although the majority of the estimated Zernike components were comparable with the corresponding measured one, the estimated values of defocus, coma, and the corresponding total aberrations were found significantly smaller than the measured values (all P < 0.01).

Conclusions

The ocular aberration measurements in myopic children under the circumstances described are reliable. The scaling-down technique is a useful option for comparing the results obtained from different pupil sizes, but the estimated Zernike coefficients were not always comparable with the corresponding measured values.

Precision and agreement of higher order aberrations measured with ray tracing and Hartmann-Shack aberrometers

BACKGROUND

To assess the precision and agreement of measurements of higher order aberrations (HOAs) obtained with a ray tracing aberrometer (iTrace) and a Hartmann-Shack aberrometer (Topcon KR-1 W).

METHODS

Prospective evaluation of the diagnostic test. Data from the right eyes of 92 normal subjects obtained using the two devices were included in this study. Two observers performed 3 consecutive scans to determine the intraobserver repeatability and interobserver reproducibility. About one week later, one observer performed an additional 3 consecutive scans to obtain the intersession reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and intraclass correlation coefficient (ICC) were used to assess the precision, while Bland-Altman plots were performed to assess the agreement.

RESULTS

For intraobserver repeatability of the ocular, corneal and internal HOAs, Topcon KR-1 W showed a 2.77Sw of 0.079 μm or less and ICCs of 0.761 or more; and iTrace showed a 2.77Sw of 0.105 μm or less and ICCs of 0.805 or more. The ICCs of the internal HOAs of interobserver reproducibility were less than 0.75 except for spherical aberration (SA) (0.862), and interobserver reproducibility of the counterpart showed similar but lower results. For the ocular, corneal and internal HOA measurements, statistically significant differences existed between the Topcon KR-1 W and iTrace (all P < 0.05). No significant differences were observed in the ocular SA and internal coma.

CONCLUSIONS

The ray tracing and Hartmann-Shack method aberrometers provided excellent repeatability but less reliable reproducibility in the measurement of HOAs (except for SA). The two aberrometers should not be interchangeable in clinical application because of the significant differences in HOA measurements between them.

[Wavefront aberrations and accommodation in myopes and hyperopes]

AIM

to comparatively investigate accommodation, pseudoaccommodation, and higher-order aberrations in children and young adults with myopia and hyperopia.

MATERIAL AND METHODS

A total of 39 myopic (the mean error of (-)5.2±1.5 diopters) and 53 hyperopic (the mean error of (+)3.1±1.15 diopters) eyes of 46 patients aged 5-20 years (11.6±0.6 years on average) were enrolled. Examination included evaluation of the objective accommodative response, relative accommodation reserves, pseudoaccommodation volume (calculated as the difference between the (+)3.0-diopter lens that is necessary for cycloplegic reading at a 33-cm distance and the weakest possible plus lens that enables reading), and higher-order aberrations (HOA), particularly the root mean square (RMS) value, vertical and horizontal trefoil, vertical and horizontal coma (coma7, coma8), and spherical aberration (SA).

RESULTS

Both objective and subjective parameters of accommodation were reliably lower in myopia as compared to hyperopia, while wavefront aberrations (RMS HOA, vertical trefoil, coma7) and pseudoaccommodation - reliably greater. SA was found to be reliably more pronounced in those myopes, who demonstrated larger volume of pseudoaccommodation. At the same time, there was a mismatch in wavefront parameters of myopes and hyperopes at different levels of accommodation and pseudoaccommodation. In myopic eyes, vertical trefoil decreased down to negative values as the accommodative response improved. In contrast to that, in hyperopic eyes with large volume of pseudoaccommodation, SA decreased below zero.

CONCLUSION

Myopia has been shown to be associated with reduced accommodation parameters as well as stronger HOA and pseudoaccommodation. Wavefront and accommodation parameters interrelations differ in myopic and hyperopic eyes. The nuances revealed should be taken into account when developing correction methods that purposefully influence refractogenesis.

Eccentric small-zone ray tracing wavefront aberrometry for refraction in keratoconus

PURPOSE

To compare objective refraction using small-zone eccentric laser ray tracing (LRT) wavefront aberrometry to standard autorefraction in keratoconus (KC), and whether the visual acuities achieved with these refractions differ from corresponding values in healthy eyes.

METHODS

Twenty-nine eyes of 29 patients with KC and 29 eyes of 29 healthy controls were included in this prospective unmasked case-control study. The uncorrected (UCVA) and spectacle-corrected (SCVA) Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuities based on refractions derived from LRT in central and four eccentric zones were compared to those achieved with standard autorefraction. The spherical equivalent (M) and two astigmatic power vectors (C0 and C45) were calculated for all refractions. Pentacam HR^® was used to generate keratometry readings of the corresponding zones.

RESULTS

In KC, the refraction from the upper nasal zone rendered a higher SCVA than the standard autorefraction more often than in the controls (p < 0.001). There were no significant variation in M between the different LRT measurement points in the control group, but central data provided the best SCVA. The UCVA:s and SCVA:s were worse in KC, and the KC eyes showed inferior myopia and superior hyperopia. Multiple refractions rendered similar SCVA:s in KC. Pentacam HR^® showed higher keratometry readings infero-temporally, but also lower readings supero-nasally, compared to controls.

CONCLUSION

In KC, eccentric LRT measurements gave better SCVA than standard autorefraction more often than in healthy eyes. Eccentric LRT may become a valuable tool in the demanding task of subjective refraction in KC.