Clinical Ocular Wavefront Analyzers

Assessment by the Scheimpflug imaging system of corneal clarity and anterior segment properties in rosacea patients

OBJECTIVE

To evaluate the effects of rosacea on ocular surface changes such as alterations in dry eye parameters, corneal densitometry, and aberrations, in comparison with healthy controls.

METHODS

A total of 88 eyes of 44 patients diagnosed with rosacea and 88 eyes of 44 healthy controls were enrolled in this cross-sectional study. All participants underwent a comprehensive dermatologic and ophthalmic examination and Tear Break-Up Time (TBUT) and Schirmer-1 tests were performed. The rosacea subtype and Demodex count and OSDI scores of all participants were recorded. Corneal topographic, densitometric, and aberrometric measurements were obtained using the Scheimpflug imaging system.

RESULTS

The mean age of the 44 patients was 41.2 ± 11.0 years of whom 31 (70.5%) were female. The mean TBUT and Schirmer-1 test values were significantly decreased and OSDI scores were significantly increased in the rosacea group compared to healthy controls (p < 0.01 for all). The most common subtype of rosacea was erythematotelangiectatic rosacea (70.4%). The severity grading of rosacea revealed that 18 (40.9%) patients had moderate erythema. The median (min-max) Demodex count was 14.0 (0-120) and the disease duration was 24.0 (5-360) months. The comparison of the corneal densitometry values revealed that the densitometry measurements in all concentric zones, especially in central and posterior zones were higher in rosacea patients. Corneal aberrometric values in the posterior surface were also lower in the rosacea group compared to healthy controls. The topographic anterior chamber values were significantly lower in the rosacea group.

STUDY LIMITATIONS

Relatively small sample size, variable time interval to hospital admission, and lack of follow-up data are among the limitations of the study. Future studies with larger sample sizes may also enlighten the mechanisms of controversial anterior segment findings by evaluating rosacea patients who have uveitis and those who do not.

CONCLUSION

Given the fact that ocular signs may precede cutaneous disease, rosacea is frequently underrecognized by ophthalmologists. Therefore, a comprehensive examination of the ocular surface and assessment of the anterior segment is essential. The main priority of the ophthalmologist is to treat meibomian gland dysfunction and Demodex infection to prevent undesired ocular outcomes.

The visual impact of higher-order aberrations in patients with pediatric blepharokeratoconjunctivitis

PURPOSE

To analyze higher-order aberrations (HOAs) and their visual impact in a pediatric blepharokeratoconjunctivitis (PBKC) cohort compared with healthy controls.

METHODS

Prospective case-control study of pediatric patients (≤ 16 years old). Subjects underwent wavefront aberrometry analysis to compare HOAs and their impact on visual quality.

RESULTS

A total of 150 eyes from 76 patients were included in the analysis. The PBKC group consisted of 50 eyes and the control group of 100 healthy eyes. Mean age was 10.39 ± 3.81 years for the PBKC group and 10.80 ± 3.61 years for the controls. Mean corrected-distance visual acuity (CDVA) was 0.24 ± 0.21 logMAR in the PBKC group and 0.07 ± 0.1 in the controls (P < 0.001). Mean astigmatism was 1.6 ± 1.98D in the PBKC group vs. 0.67 ± 0.76D in the control group (P = 0.01). Mean RMS of HOAs was 1.05 ± 1.7mm in the PBKC group and 0.41 ± 0.18mm in the controls (P < 0.001). The mean modulation transfer function (MTF) in the PBKC group was significantly lower (16.37 ± 16.32) than controls (30.3 ± 23.57) (P < 0.001). Corneal leukomas, stromal vascularization, peripheral nummular subepithelial scars, and pannus formation are associated with increased HOAs.

CONCLUSIONS

There was a significant increase in total HOAs of eyes with PBKC compared to healthy controls. Corneal opacity, vascularization, and scarring are associated with increased HOAs. The PBKC eye aberration profile: coma, secondary astigmatism, quadrafoil, and pentafoil, were associated with decreased CDVA and visual quality (PSF and MTF).

Sub-Bowman keratomileusis versus femtosecond laser in situ keratomileusis on the long-term visual recovery: A comparative study

Purpose

To explore the long-term visual quality of the same subjects after sub-Bowman keratomileusis (SBK) or femtosecond laser in situ keratomileusis (FS-LASIK).

Methods

This prospective study included patients screened for corneal refractive surgery at the Refractive Surgery Center of our Hospital between November 2017 and March 2018. One eye underwent SBK, while the other eye underwent FS-LASIK. Total higher-order aberrations, coma aberrations, and clover aberrations were evaluated before and at 1 month and 3 years after the procedure. The visual satisfaction of both eyes was investigated, respectively. The participants completed a surgical satisfaction questionnaire.

Results

Thirty-three patients were included. There were no significant differences in total higher-order aberrations, coma aberrations, and clover aberrations between the two procedures before and 1 month and 3 years after surgery (all P > 0.05), except for the total coma aberrations in FS-LASIK were significantly higher compared with the SBK group at 1 month after surgery [0.51 (0.18, 0.93) vs. 0.77 (0.40, 1.22), P = 0.019]. The surgical satisfaction questionnaire scores of the SBK group and the FS-LASIK group were 9.8 ± 0.8 and 9.8 ± 0.8, respectively, at 1 month, and 9.7 ± 0.9 and 9.7 ± 1.0, respectively, at 3 years (all P > 0.05).

Conclusion

There were no differences in corneal aberrations and satisfaction between SBK and FS-LASIK procedures at 1 month and 3 years.

Performance of Zernike polynomials in reconstructing raw-elevation data captured by Pentacam HR, Medmont E300 and Eye Surface Profiler

PURPOSE

To investigate the capability of Zernike polynomials fitting to reconstruct corneal surfaces as measured by Pentacam HR tomographer, Medmont E300 Placido-disc and Eye Surface Profiler (ESP).

METHODS

The study utilised a collection of clinical data of 527 participants. Pentacam HR raw elevation data of 660 eyes (430 healthy and 230 keratoconic) were fitted to Zernike polynomials of order 2 to 20. Same analyses were carried out on 158 eyes scanned by Medmont E300 Placido-disc and 236 eyes were scanned by ESP for comparison purposes. The Zernike polynomial ​fitting was carried out using a random 80% of each individual eye surface's data up to a corneal radius of 5 mm and the root means squared fitting error (RMS) was calculated for the unused 20% portion of the surface data. The process was carried out for the anterior and posterior surfaces of the corneal measurements of the Pentacam HR and the anterior surfaces only with the ESP and the Medmont E300 measurements.

RESULTS

Statistical significances in reduction of RMS were noticed up to order 14 among healthy participants (p < 0.0001 for right eyes, p = 0.0051 for left eyes) and up to order 12 (p < 0.0001 for right eyes, p = 0.0002 for left eyes) in anterior surfaces measured by the Pentacam. Among keratoconic eyes, statical significance was noticed up to order 12 in both eyes (p < 0.0001 for right eyes, p = 0.0003 for left eyes). The Pentacam posterior corneal data, both right and left, healthy and keratotic eyes recorded significance (p < 0.0001) in reduction of RMS up to order 10 with same RMS values of 0.0003 mm with zero standard deviation. RMS of fitting Zernike polynomials to Medmont data up to order 20 showed a consistent reduction in RMS with the increase of the fitting order with no rise at high fitting orders. Minimum RMS = 0.0047 ± 0.0021 mm, 0.0046 ± 0.0019 mm for right and left eyes respectively were recorded at order 20 and were more than 15 times the minimum RMS of the Pentacam. RMS of fitting Zernike polynomials to ESP data also showed a consistent reduction in RMS with the increase of the fitting order with no sign of any rise at high fitting orders. Similar to the Medmont, minimum RMS of 0.0005 ± 0.0003 mm, 0.0006 ± 0.0003 mm was recorded at order 20 for right and left eyes respectively and was 2 times the minimum RMS of the Pentacam for right eyes and 1.7 times the minimum RMS of the Pentacam for left eyes.

CONCLUSIONS

Orders 12 and 10 Zernike polynomials almost perfectly matched the raw-elevation data collected from Pentacam for anterior and posterior surfaces, respectively for either healthy or keratoconic corneas. The Zernike fitting could not perfectly match the data collected from Medmont E300 and ESP.

Digital ocular swept source optical coherence aberrometry

Ocular aberrometry is an essential technique in vision science and ophthalmology. We demonstrate how a phase-sensitive single mode fiber-based swept source optical coherence tomography (SS-OCT) setup can be employed for quantitative ocular aberrometry with digital adaptive optics (DAO). The system records the volumetric point spread function at the retina in a de-scanning geometry using a guide star pencil beam. Succeeding test-retest repeatability assessment with defocus and astigmatism analysis on a model eye within ± 3 D dynamic range, the feasibility of technique is demonstrated in-vivo at a B-scan rate of >1 kHz in comparison with a commercially available aberrometer.

Accuracy of Intraoperative Aberrometry, Barrett True-K With and Without Posterior Cornea Measurements, Shammas-PL, and Haigis-L Formulas After Myopic Refractive Surgery

PURPOSE

To assess the accuracy of intraoperative aberrometry, the Barrett True-K No History (Barrett TKNH), Barrett TKNH with posterior corneal measurements (Barrett TKNH with PC), Shammas-PL, and Haigis-L formulas in patients with cataract who had prior myopic refractive surgery.

METHODS

This was a retrospective consecutive case series of patients with prior myopic refractive surgery undergoing cataract extraction. Mean absolute error (MAE) and median absolute error (MedAE) of refraction prediction were compared for each formula. Interactions of each biometry measurement were modeled for each formula to evaluate those with the most significant impact on refraction prediction.

RESULTS

One hundred sixteen eyes of 79 patients were analyzed. MAE was 0.40 ± 0.33 diopters (D) for intraoperative aberrometry and 0.42 ± 0.31 D for the Barrett TKNH, 0.38 ± 0.30 D for the Barrett TKNH with PC, 0.47 ± 0.38 D for the Shammas-PL, and 0.56 ± 0.39 D for the Haigis-L formulas. Comparisons between formulas were significant for Barrett TKNH versus Barrett TKNH with PC formulas (P = .046), Barrett TKNH with PC versus Shammas-PL formulas (P = .023), and for all comparisons with the Haigis-L formula (P < .001), and not significant for all other comparisons (P > .05). Eyes were within ±0.50 D of prediction 73%, 72%, 69%, 62%, and 52% of the time for intraoperative aberrometry, the Barrett TKNH with PC, Barrett TKNH, Shammas-PL, and Haigis-L formulas, respectively. Corneal asphericity (Q value) was significantly associated with prediction error for all five methods. Changes in anterior chamber depth had a significant impact on Shammas-PL prediction errors.

CONCLUSIONS

Newer technology using information from the posterior cornea modestly improved outcomes when compared to established methods for intraocular lens selection in eyes that had previous laser refractive surgery for myopia. [J Refract Surg. 2021;37(1):60-68.].

Repeatability and Agreement of Wavefront aberrations of Pentacam AXL Wave- a new hybrid topographer and aberrometer with ITrace in healthy eyes

PURPOSE

To assess repeatability and agreement of Pentacam AXL Wave, with iTrace aberrometer.

SETTING

Narayana Nethralaya, Bangalore, India.

DESIGN

Prospective ,cross-sectional study.

METHODS

One hundred eyes of 100 patients underwent three sets of measurements, at a single visit, using Pentacam AXL Wave (Oculus, Germany) and iTrace (Tracey Technologies, USA).Lower-order aberration (LOA), higher-order aberration (HOA), Coma and Spherical Aberrations (SA) were analyzed. Repeatability was assessed using within-subject standard deviation (Sw), test-retest variability (TRT), within-subject coefficient of variation (COV) and Intraclass Correlation Coefficient (ICC). The Bland-Altman analysis was used to assess 95% limits of agreement (LoA) and the correlation coefficient (r) to determine strength of relationship between measurements.

RESULTS

All measurements with Pentacam AXL Wave had repeatability with an ICC for total ocular aberrations ranging from 0.84 for HOAto 0.92 for LOA and corneal from 0.76 for HOA to 0.86 for LOA The Sw, TRT, COV of all aberrations were significantly lower (better) than those of iTrace (p < 0.001). The mean differences between 2 devices were insignificant for the comparison of all parameters, except for spherical aberration (0.011(0.002571 to 0.02008; P= 0.01). Both devices showed excellent corelations for ocular aberrations (tHOA (P=0.12,LoA= -0.52 to 0.025; r= 0.89); LOA (P=0.14, LoA = -2.71 to 2.61  ; r= 0.96) coma (P=0.27, LoA = -0.11 to 0.12; r= 0.89) and in SA (P=0.01,  LoA = -0.09 to 0.07;r=0.97)).

CONCLUSIONS

The repeatability estimates for wavefront aberrations using Pentacam AXL Wave were significantly better than that using iTrace. Both devices showed excellent corelations for total ocular aberrations.

Time Utilization and Refractive Prediction Enhancement Associated with Intraoperative Aberrometry Use During Cataract Surgery

Purpose

To evaluate the time cost of intraoperative aberrometry (IA), to compare IA prediction error to the prediction error associated with conventional formulas using preoperative calculations (PC) and evaluate when IA provides clinically relevant benefit.

Methods

This is a retrospective study of eyes that underwent cataract phacoemulsification surgery with IA at an academic eye center. IA versus PC prediction error were compared amongst various preoperative and intraoperative characteristics. Additionally, a dichotomous variable indicating clinically relevant benefit of IA, where IA absolute prediction error was less than 0.5D and PC absolute prediction error greater than 0.5D, was associated with clinical factors.

Results

Five hundred eyes of 341 patients were included in the analysis. The quantitative difference between mean absolute prediction errors for IA versus PC was between 0.0D and 0.03D in most subgroups. For the 11.0% of eyes that had clinically relevant benefit to IA, the multivariable model identified the following strongest predictors: prior myopic corneal refractive surgery (Odds ratio (OR) 3.9, p<0.01 for myopic LASIK/PRK, OR 5.5, p=0.01 for radial keratotomy), toric or multifocal/EDOF lens implantation (OR 2.7, p=0.03 for toric monofocal lenses, OR 3.1, p=0.01 for EDOF/multifocal lenses), and short and long axial lengths (p<0.01). On average, IA implementation added 3.0 minutes to surgery (p<0.01).

Conclusion

For greatest likelihood of a clinically meaningful improvement in outcomes despite increased surgical time, surgeons and patients should consider using IA for eyes with extremes in axial length, eyes with prior myopic corneal refractive surgery, or when implanting lenses with toric or extended-depth-of-focus/multifocal properties.

Evaluation of Corneal Higher-Order Aberrations by Scheimpflug-Placido Topography in Patients with Different Refractive Errors: A Retrospective Observational Study

Purpose

To report the characteristics of anterior and posterior corneal high-order aberrations in patients with different refractive errors.

Setting

This study was conducted at Sohag Refractive Center, Sohag, Egypt.

Design

This is a retrospective observational study.

Methods

This study evaluated 750 patients (750 eyes) who were seeking refractive surgery. The eyes were stratified into five groups (150 eyes/group) based on refractive error: mild-to-moderate myopia, high myopia, hyperopia, simple myopic astigmatism, and simple hypermetropic astigmatism. All patients were subjected to comprehensive ophthalmological examination including corneal topography and corneal aberrometry using the Scheimpflug–Placido topography (Sirius, CSO, Italy).

Results

Coma aberration was statistically significant when compared in all five groups (P=0.01). It was highest in the hypermetropia group (0.26 ± 0.12 μm) but lower in the moderate myopia, high myopia, myopic astigmatism, and hypermetropic astigmatism groups. Spherical aberration was lowest in the hypermetropia group and significantly different from that in the other groups. Trefoil was statistically insignificant when all groups were compared (P=0.062) but was highest in the myopic astigmatism group (0.24 ± 0.25 μm). Total RMS peaked in the hypermetropia group (0.99 ± 0.70).

Conclusions

In normal corneas and regular refractive errors, the cornea-induced high-order aberration was minimal, and all types of refractive errors were associated with certain types of high-order aberrations, with a significant increase in spherical aberration in the hypermetropia group.

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.

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.

Comparison of Higher Order Aberrations with Spherical and Aspheric Iols Compared to Normal Phakic Eyes

Purpose

To compare higher order aberrations (HOA) in AcrySof SN60AT and Acrysof IQ SN60WF intraocular lenses (IOLs) and natural crystalline lenses in an age-matched population.

Methods

Sixty-nine eyes of 55 patients were examined. Group I included AcrySof spheric lenses, group II AcrySof aspheric lenses, and group III included patients with the natural crystalline lens. The HOA data were obtained with a LADARWave aberrometer (Alcon Inc.). Analysis was based on the RMS of coma, spherical aberrations (SA), and HOA. Statistical comparisons were performed with Kruskal Wallis variance analysis.

Results

In the case of coma, there were statistically significant differences between spheric and aspheric AcrySof (p<0.005) and between spheric AcrySof and natural crystalline lenses (p<0.005). The differences between aspheric AcrySof and natural crystalline lens group were not significant (p>0.05). SA were significantly different between spheric and aspheric AcrySof group, and spheric AcrySof and natural crystalline lens group (p<0.005), as well as between aspheric AcrySof and natural crystalline lens group (p<0.05). In case of HOA no significant differences were observed between aspheric AcrySof and natural crystalline lens group (p>0.05), but differences between groups AcrySof spheric and aspheric, and spheric AcrySof and natural crystalline lens, showed high significance (p<0.005).

Conclusions

The AcrySof Natural IQ aspheric model SN60WF IOL did not change the optical quality of vision compared to a healthy population of 60–80 years of age. The AcrySof Natural model SN60AT spherical IOL resulted in higher HOAs relative to both the natural crystalline lens population and eyes after aspheric AcrySof IQ model SN60WF IOL implantation.

Bigaussian Wavefront Model for Normal and Keratoconic Eyes

PURPOSE

To report bigaussian multivariate wavefront models capable of stochastically generating an unlimited amount of plausible wavefront data for either normal or keratoconic eyes.

METHODS

The models use centroid wavefront data measured previously with an iTrace in 330 healthy right eyes and 122 keratoconic right eyes. These centroids were fitted to an 11th-order Zernike series, followed by principal component analysis to reduce dimensionality and remove correlations. The remaining parameters were then fitted to a sum of two multivariate Gaussian distributions. This fit then forms the core of the stochastic model, which may be used to generate synthetic data. Finally, the agreement between the original and synthetic data was tested using two one-sided t tests.

RESULTS

For normal eyes, the first eigenvectors mostly represent pure Zernike polynomials, with a decreasing degree of purity with increasing order. For keratoconic eyes, eigenvector purity was considerably lower than for normal eyes. Depending on the data set, series of 22 to 29 eigenvectors were found sufficient for accurate wavefront reconstruction (i.e., root-mean-square errors below 0.05 μm). These eigenvectors were then used as a base for the stochastic models. In all models and all Zernike coefficients, the mean of the synthetic data was significantly equal to that of the original data (two one-sided t test, P > .05/75), but the variability of the synthetic data is often significantly lower (F test, P < .05/75).

CONCLUSIONS

This synthetic wavefront model may be safely used in calculations as an alternative to actual measurements should such data not be available.

Higher order aberrations of the eye: Part one

This article is the first in a series of two articles that provide a comprehensive literature review of higher order aberrations (HOAs) of the eye. The present article mainly explains the general principles of such HOAs as well as HOAs of importance, and the measuring apparatus used to measure HOAs of the eye. The second article in the series discusses factors contributing to variable results in measurements of HOAs of the eye.Keywords: Higher order aberrations; wavefront aberrations; aberrometer

Evaluation of the impact of persistent subepithelial corneal infiltrations on the visual performance and corneal optical quality after epidemic keratoconjunctivitis

PURPOSE

Aim was to measure the effect of persistent subepithelial corneal infiltrates (SEIs) after epidemic keratoconjunctivitis (EKC) on visual performance and corneal optical quality.

METHODS

We examined 53 patients divided into two groups. Patients with previous EKC constituted the study group (Group 1, n: 27). Healthy age matched subjects constituted the control group (Group 2, n: 26). Study group was subdivided into eyes with SEI (Group 1A, 40 eyes) and healthy fellow eyes (Group 1B, 14 eyes). Patients were submitted to a complete examination including high- and low-contrast visual acuities (HCVA, LCVA), corneal topography and aberrometry.

RESULTS

The mean interval between epidemic conjunctivitis and examination was 7.25 ± 5.63 months. Mean number of corneal infiltrates was 17.30 ± 14.38. The mean HCVA and LCVA were significantly lower in the eyes with SEI than fellow eyes and control group (p = 0.001). LCVA value was also worse in the fellow eyes when compared to control (p = 0.048). Corneal topography values were significantly higher in the eyes with SEI from both fellow eyes and control group. During corneal aberrometry, the mean root mean square value of spheric aberration, irregular astigmatism and total aberration were significantly higher in SEI group when compared to fellow eyes and control group (p < 0.05). Total aberrations were higher than control subjects in the fellow eyes. Trefoil aberration was higher in SEI group only when compared to control subjects, while there was no significant difference in coma aberration values between the groups (p > 0.05).

CONCLUSION

Results of this study suggested that visual performance is compromised in patients with EKC by aberrations and changes in topographic variables.

A comparison of a traditional and wavefront autorefraction

PURPOSE

To evaluate the agreement between the autorefraction function of the Canon RK-F2, an autorefractor/keratometer based on the ray deflection principle, and the Carl Zeiss Vision i.Profiler(Plus), an wavefront aberrometer, compared with each other and with a noncycloplegic subjective refraction.

METHODS

Objective refraction results obtained using both instruments were compared with noncycloplegic subjective refractions for 174 eyes of 100 participants. Analysis of sphere, cylinder, and axis using spherical equivalent difference and a new measurement, cross-cylinder difference, was performed. The spherical equivalent refraction and cross-cylinder difference for the manifest refraction were compared using Bland-Altman limits of agreement and 95th percentile analysis.

RESULTS

The 100 participants represent 52 women and 48 men with a mean (±SD) age of 51.7 (±13.8) years, an average (±SD) spherical power of -0.67 (±2.53) diopters (D), and an average (±SD) cylinder power of -0.94 (±0.87) D. The spherical equivalent difference is 0.03 D (Canon) and -0.11 D (Zeiss). The 95% limits of agreement for the spherical equivalent are -0.69 to 0.75 D (Canon) and -0.75 to 0.75 D (Zeiss). The mean cross-cylinder power difference is -0.08 D (Canon) and 0.02 D (Zeiss). The 95% limits of agreement for the cross-cylinder power difference are 0.63 to 0.50 D (Canon) and 0.49 to 0.75 D (Zeiss). The mean axis power difference is -0.04 D (Canon) and 0.05 D (Zeiss). The 95% limits of agreement for axis power difference are -0.71 to 0.63 D (Canon) and -0.78 to 0.78 D (Zeiss). The double-angle astigmatic plot center of distribution for the RK-F2 is 0.035 D at 70 degrees, and that for the i.Profiler(Plus) is 0.053 D at 32 degrees.

CONCLUSIONS

Both instruments provided clinically useful spherical equivalent refractive data compared with a subjective refraction, whereas the Canon RK-F2 was slightly more accurate in determining the cylinder power compared with a subjective refraction.

A pilot study on total, corneal, and internal aberrations in insulin-dependent and non-insulin-dependent diabetes mellitus patients

PURPOSE

To explore the distribution of total, corneal, and internal higher-order aberrations (HOAs) in both insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic patients.

METHODS

Pilot study including seven patients with IDDM (14 eyes) and 11 patients with NIDDM (22 eyes). Ocular HOAs were examined using ray tracing aberrometry (i-Trace, Tracey Technologies Corp., Houston, TX) and the measurements of anterior segment using Scheimpflug imaging (Pentacam, Oculus Inc. Germany).

RESULTS

Total HOAs was slightly higher in IDDM (0.634 ± 0.228 μm, 95% IC ± 0.131) than in NIDDM patients (0.527 ± 0.245 μm, 95% IC ± 0.108) (p = 0.267). The greatest contributor for total ocular HOAs was internal vertical coma (Z3 (- 1)) for both diabetic groups. In NIDDM, age and central corneal thickness (CCT) were correlated with total HOAs (p < 0.001, p = 0.0180 respectively); however, anterior chamber volume (ACV) was inversely correlated with total HOAs (p = 0.019). In IDDM, total HOAs were correlated with posterior asphericity (Q) (p = 0.002) and inversely correlated with ageing (p = 0.013).

CONCLUSIONS

Diabetic patients showed high values of total and internal vertical coma (Z3 (- 1)). There might be a role for optical quality measurements in monitoring changes due to DM.

Analysis of four aberrometers for evaluating lower and higher order aberrations

PURPOSE

To compare the measurements of lower and higher order aberrations (HOA) of 4 commonly used aberrometers.

SETTING

Massachusetts Eye & Ear Infirmary, Boston, USA.

DESIGN

Prospective, cross-sectional study, in a controlled, single-blinded fashion.

METHODS

Multiple readings were obtained in 42 eyes of 21 healthy volunteers, at a single visit, with each of the following aberrometers: Alcon LADARWave®, Visx WaveScan®, B & L Zywave®, and Wavelight Allegro Analyzer®. Results were compared and analyzed in regards to the lower and HOA, to the different wavefront sensing devices and software, Tscherning and Hartmann-Shack and between the Fourier and Zernike algorithms. Statistical analysis included Bland-Altman plots, Intraclass Correlation Coefficient (ICC), multiple comparison tests with Analysis of Variance and Kruskal-Wallis. Significant level was set to p<0.05 and alpha level correction was adjusted under the Bonferroni criteria.

RESULTS

Most measurements of all 4 aberrometers were comparable. However, statistically significant differences were found between the aberrometers in total HOA (tHOA), spherical aberration (SA), horizontal coma and astigmatism (2,2). LADARwave and Wavescan showed significant differences in tHOA (P<0.001, ICC = 0.549, LoA = 0.19±0.5) and in SA (P<0.001, ICC = 0.733, LoA = 0.16±0.37). Wavescan showed a significant difference compared to Zywave (p<0.001, ICC = 0.920, LoA = 0.09±0.13) in SA. Comparisons between Allegro Analyzer and Zywave demonstrated significant differences in both Horizontal Coma (3,1) (p<0.001, ICC = -0.207, LoA = -0.15±0.48) and Astigmatism (2,2) (P = 0.003, ICC = -0.965, LoA = 0.2±2.5). Allegro Analyzer also differed from Wavescan in Horizontal Coma (3,1) (P<0.001, ICC = 0.725, LoA = -0.07±0.25).

CONCLUSIONS

Although some measurements were comparable predominately in the lower order aberrations, significant differences were found in the tHOA, SA, horizontal coma and astigmatism. Our analysis suggests that sensor design contributes to agreement in lower order aberrations, and Fourier and Zernike expansion might disagree in higher order aberrations. Therefore, comparison between aberrometers was generally possible with some exceptions in higher order measurements.

Intrasubject repeatability of internal aberrometry obtained with a new integrated aberrometer

PURPOSE

To evaluate the intrasubject repeatability of the internal aberrometry obtained with a new integrated aberrometer in a sample of normal eyes to assess its clinical usefulness.

METHODS

Twenty-six healthy eyes of 26 participants, aged 20 to 50 years, were included in the study. All eyes achieved corrected distance visual acuity of 1.0 (Snellen decimal notation) and did not undergo previous ocular surgeries. Three consecutive measurements of internal aberrations were obtained with the KR-1W system (Topcon Corp) by an experienced examiner. Intrasubject repeatability for 4- and 6-mm pupils was evaluated by the within-subject standard deviation (S(w)) and intraclass correlation coefficient (ICC).

RESULTS

Low values of S(w) and values of ICC close to 1 were found for the 4-mm pupil astigmatism and for several aberrometric coefficients: primary spherical aberration and higher order, third order, and trefoil root-mean-square (RMS). Significant correlations of the S(w) for the 4-mm pupil higher order aberrations RMS with the magnitude of different aberrometric coefficients were found (r≥0.611, P<.01). In addition, tetrafoil RMS for 4-mm pupils correlated significantly with the S(w) for some higher order errors (r≥0.675, P<.01). Significantly larger values of S(w) for 6-mm pupils were found for trefoil (P<.01) and secondary astigmatism RMS (P=.02).

CONCLUSIONS

The KR-1W provided repeatable measurements of internal astigmatism and some higher order aberrations, although consistency of such measurements appears to be limited by the level of aberration.

Higher Order Aberrations Using the NIDEK OPD-Scan and AMO Wavescan

Purpose:

To compare higher order aberrations measured with the NIDEK OPD-Scan and AMO WaveScan.

Methods:

Third- to sixth-order higher order aberrations were measured in 1072 eyes using the OPD-Scan and WaveScan. Means, standard deviations, confidence intervals, limits of agreement, and intraclass correlation coefficients (ICC) were calculated.

Results:

Aberrations of greatest magnitude with the OPD-Scan were Z 3 − 3 (−0.113±0.243 μ m), Z 4 0 (0.073±0.137 μ m), and Z 3 − 1 (−0.058±0.165 μ m), and with the WaveScan, Z 3 − 3 (−0.054±0.103 μ m), Z 4 0 (0.049±0.083 μ m), and Z 3 1 (−0.017±0.100 μ m). The largest difference in magnitude between the two aberrometers was with Zernike polynomial Z 3 − 3 (−0.060±0.205 μ m). Medium consistency (0.6<ICC<0.8) was found between the two instruments for Z 3 − 1 and Z 4 0 . All other Zernike polynomials had a poor consistency (ICC<0.6) including the total root-mean-square (RMS) higher order aberrations.

Conclusions:

Poor consistency was found for all aberrations except Z 3 − 1 and Z 4 0 , which demostrated medium consistency. Expected aberration reference values are reported for both instruments.

Pupil size, white-to-white corneal diameter, and anterior chamber depth in patients with myopia

PURPOSE

To evaluate anatomical parameters in a population of patients with myopia.

METHODS

Nine hundred sixty-four myopic eyes (-3.00 to -20.00 diopters [D] spherical equivalent refraction) were evaluated to measure mesopic and photopic pupil size with an infrared pupillometer; anterior chamber depth and white-to-white corneal diameter were obtained with Orbscan II (Bausch & Lomb). Correlation analysis was performed to evaluate the relationships among anatomical parameters of the anterior segment of the eye.

RESULTS

Average change in pupil size between mesopic and photopic conditions shows a uniform gap of 1.5 mm in patients aged 18 to 62 years with a slight insignificant trend to decrease with age. Photopic and mesopic pupil size were highly correlated (r=0.694, P<.001) and the difference between both measures was positively correlated with mesopic pupil size (r=0.207, P<.001) and inversely correlated with photopic pupil size (r=0.561, P<.001). Anterior chamber depth and white-to-white corneal diameter were positively correlated (r=0.389, P<.001). White-to-white corneal diameter and anterior chamber depth were not correlated with age (r=-0.096, P<.001) or anterior chamber depth (r=-0.183, P<.001-0.183) as a function of age.

CONCLUSIONS

Average difference between photopic and mesopic pupil size remained constant across the range of ages included in this cohort. A positive correlation was noted between anterior segment dimensions, and anterior chamber depth decreased with age.

A pilot study on the differences in wavefront aberrations between two ethnic groups of young generally myopic subjects

A comparative population-based cross-sectional study design was used to examine the prevalence of wavefront patterns in two different ethnic groups, and the relationship of these patterns with ocular biometrics and gender. The Shin-Nippon SRW5000 open field autorefractor, the Wavefront Analysis Supported Customized Ablation (WASCA) wavefront analyser and the IOLMaster were used to determine wavefront aberrations, mean spherical equivalent (SE) refractive error and axial length (AL). Seventy-four eyes from 74 young healthy subjects (44 British Asians, 30 Caucasians; 36 men, 38 women; mean age 22.51 +/- 3.89 years) with mean SE averaging -1.90 +/- 2.76 D (range -10.88 to +2.19 D) were examined. Relationships between ethnicity, gender, AL and SE, against the wavefront high-order root mean square, and aberration components up to the fifth order, were assessed by using multiple regression and correlation analysis. AL on its own accounted for 4.7% of the variance in trefoil component Z(-3)(3) (F(1,72) = 4.602; p = 0.035), 13.7% of coma component Z(1)(3) (F(1,72) = 12.536; p = 0.001), 6.1% of trefoil component Z(3)(3) (F(1,72) = 5.705; p = 0.020) and 9.8% of coefficient Z(-2)(4) (F(1,72) = 8.908; p = 0.004). A significant model emerged (F(2,71) = 6.164; p = 0.003) for ethnicity and axial length, accounting for 12.4% of variance in primary spherical aberration with ethnicity accounting for 8.4% of that variance. For Caucasian subjects, a significant correlation was found between axial length and (Pearson's correlation coefficient -0.500; p = 0.005) and Z(0)(4) (Pearson's correlation coefficient -0.423; p = 0.020). For British Asian subjects, AL was only correlated with coefficient Z(-2)(4) (Pearson's correlation coefficient -0.358; p = 0.017). Ethnicity is a factor to be considered in the variability of wavefront aberration, particularly spherical aberration. Relationship between AL and wavefront aberrations seems to vary between ethnicities. If higher order aberrations play a role in the emmetropization process, this may be different for different populations.

Optical quality in eyes with aspheric intraocular lenses and in younger and older adult phakic eyes: comparative study

PURPOSE

To compare ocular higher-order aberrations (HOAs) in eyes with aspheric intraocular lenses (IOL) and in phakic eyes.

SETTING

Department of Ophthalmology, Military Health Service Institute, Warsaw, Poland.

METHODS

Higher-order aberrations with a 5.0 mm pupil and best spectacle-corrected visual acuity (BSCVA) were analyzed in a young phakic group (age 20 to 40 years), older phakic group (age 40 to 60 years), and a pseudophakic group (age 62 to 84 years; SN60WF aspheric IOL).

RESULTS

The mean coma was 0.13 microm+/-0.07 (SD) in the younger phakic group, 0.18+/-0.08 microm in the older phakic group, and 0.16+/-0.08 microm in the pseudophakic group; the difference between the 2 phakic groups was statistically significant (P< .005). The mean spherical aberration was 0.07+/-0.05 microm, 0.11+/-0.05 microm, and 0.06+/-0.04 microm, respectively; the only statistically significant difference was between the 2 phakic groups (P< .005). The mean HOA value was 0.54+/-0.18 microm, 0.76+/-0.12 microm, and 0.92+/-0.31 microm, respectively; the difference was statistically significant between the 2 phakic groups or between the younger phakic group and the pseudophakic group (both P< .005). There were no statistically significant differences in BSCVA between the 3 groups.

CONCLUSIONS

Spherical and coma aberrations were similar in eyes with an aspheric IOL and younger phakic eyes, although HOAs were higher in pseudophakic eyes. There were no differences between pseudophakic eyes and older phakic eyes in coma and HOA, although pseudophakic eyes had lower spherical aberration.