Total and Corneal Optical Aberrations Induced by Laser in situ Keratomileusis for Hyperopia

Changes in Corneal Higher-Order Aberrations and Ocular Biometric Measurements after Phacoemulsification Combined with Goniosynechialysis in Primary Angle Closure/Glaucoma Patients

Purpose

To compare corneal higher-order aberrations (HOAs), refractive error, and ocular biological parameters before and after phacoemulsification combined with goniosynechialysis (Phaco-GSL) in primary angle closure/glaucoma (PAC/PACG) patients with different axial lengths (ALs).

Methods

In this prospective study, cataract patients diagnosed with PAC/PACG were categorized into two groups based on their ALs: the short AL group (AL ≤ 22.5 mm) and the normal AL group (22.5 < AL ≤ 24.5 mm). The pre- and postsurgery measurements of intraocular pressure (IOP) and best-corrected visual acuity (BCVA) were conducted at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months. Additionally, the assessments included corneal HOAs, the number of antiglaucoma medications, visual field parameters, manifest refraction, and other ocular biological parameters before surgery and at the final follow-up.

Results

Prior to surgery, the two groups exhibited no significant differences, except for AL, curvature value, and Z (4, 0) of the posterior corneal surface (all P < 0.01). Following surgery, BCVA improved, and IOP decreased significantly in both groups (P < 0.01). Both anterior and total corneal HOAs, along with Z (3, -3), increased in the two groups (all P < 0.05), with the normal AL group exhibiting a significantly greater increase in total cornea Z (3, -3) than the short AL group (P=0.047). The normal AL group also exhibited a slight tendency towards hyperopia (P < 0.01). Significant changes were observed in the visual field index and mean deviation in both groups (P < 0.05).

Conclusions

Phaco-GSL resulted in an increased corneal HOAs, particularly trefoil, with variations based on the patient's AL. Patients with normal ALs tended to shift towards hyperopia after surgery.

Comparison of Visual Outcomes and Higher-order Aberrations Between FS-LASIK and SMI-LIKE for Moderate to High Hyperopia: A 2-Year Result

PURPOSE

The aim of the study was to evaluate and compare the long-term visual outcomes and higher-order aberrations (HOAs) between femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule intrastromal keratoplasty (SMI-LIKE) in the correction of moderate to high hyperopia.

METHODS

In this study, 16 subjects (20 eyes) underwent FS-LASIK and 7 subjects (10 eyes) underwent SMI-LIKE. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, mean keratometry (Km), anterior asphericity (Q), and HOAs preoperatively and 2 years postoperatively were obtained in both procedures.

RESULTS

The efficacy indices of the FS-LASIK group and the SMI-LIKE group were 0.85 ± 0.14 and 0.87 ± 0.17, respectively. The safety indices of the FS-LASIK and SMI-LIKE groups were 0.99 ± 0.15 and 1.08 ± 0.24, respectively. No significant difference in safety index or efficacy index was found between the FS-LASIK and SMI-LIKE groups (all P > 0.05). The correlation coefficient of the attempted versus achieved spherical equivalent postoperatively was 0.69 ( P < 0.01) and 0.89 ( P < 0.01) in the FS-LASIK group and SMI-LIKE groups, respectively. The front Km, negative Q value, negative spherical aberrations (SAs), coma, and total HOAs significantly increased postoperatively in the 2 groups ( P < 0.05). The FS-LASIK group had greater changes in Q value and SA postoperatively than the SMI-LIKE group ( P < 0.01).

CONCLUSIONS

SMI-LIKE had similar safety and efficacy to FS-LASIK in the correction of moderate to high hyperopia. However, SMI-LIKE may equip better visual quality postoperatively for its lower Q value and SA changes than FS-LASIK.

Defocus Curve and Satisfaction of Patients with Presbyopia After LASIK Using the Differential Modulation of Binocular Longitudinal Spherical Aberration

Purpose

To investigate the visual acuity and satisfaction of patients after Zhang & Zheng's corneal laser-enhanced accommodation refraction Q (ZZ-CLEAR-Q) surgery utilizing differential modulation of binocular longitudinal spherical aberration and determine its clinical significance.

Patients and Methods

This prospective observational study enrolled a consecutive cohort of patients with presbyopia who underwent ZZ-CLEAR-Q surgery between December 2020 and January 2023. The study assessed visual acuity, distance-corrected defocus curve, satisfaction, Q factor, manifest spherical equivalent, and primary spherical aberration, among others, at 3 months postoperatively. Additionally, the study conducted a binocular comparison to analyze the clinical significance of setting the different longitudinal spherical aberrations.

Results

A total of 232 eyes of 116 patients were included. The binocular uncorrected distance visual acuity was 20/20 for all patients. At 3 months postoperatively, the binocular uncorrected near visual acuity was Jaeger 1 for 96% of the patients and Jaeger 2 for 100% of the patients. Furthermore, 93.1% of the patients expressed satisfaction. The monocular distance-corrected defocus curve revealed that the dominant eyes had significantly better visual acuity at 0 D (P<0.001), while the non-dominant eyes had significantly better visual acuity across various defocus levels except 0 and -0.50 D (All P<0.05). At 3 months, there were no significant differences between the expected and achieved manifest spherical equivalents, corneal Q factor values, and ocular primary spherical aberration values of both groups.

Conclusion

Patients with presbyopia who underwent ZZ-CLEAR-Q surgery were likely to achieve normal uncorrected visual acuity and be satisfied. The increased depth of field has clinical significance for assisting near vision.

Computational simulation of the optical performance of an EDOF intraocular lens in post-LASIK eyes

PURPOSE

To evaluate computationally the optical performance of AcrySof IQ Vivity extended depth-of-focus (EDOF) intraocular lenses (IOLs) in post-laser in situ keratomileusis (LASIK) eyes.

SETTING

Visual Optics and Biophotonics Laboratory, Madrid, Spain.

DESIGN

Experimental study.

METHODS

Computer pseudophakic eye models were implemented using reported post-LASIK corneal aberrations (refractive corrections from -7.5 to +4.5 diopters [D]) and virtually implanted with monofocal (AcrySof IQ) or EDOF (AcrySof IQ Vivity) IOLs. Retinal image quality was quantified through visual Strehl (VS). The depth of focus (DOF) was calculated from the through-focus VS curves. Halos were estimated from the light spread in the image of a pinhole. Those quantitative parameters were obtained for 5.0 and 3.0 mm pupil diameters.

RESULTS

Simulated virgin eyes showed VS of 0.89/0.99 with monofocal IOLs and 0.74/0.52 with EDOF IOLs for 5.0/3.0 mm pupils at best focus. VS decreased with induced spherical aberration (SA) by 25% and with induced SA + coma by 61% on average (3.0 mm pupils). The DOF was 2.50 D in virgin eyes with EDOF IOLs, 1.66 ± 0.30 and 2.54 ± 0.31 D ( P < .05) on average in post-LASIK eyes for 3.0 mm pupils, monofocal and EDOF IOLs, respectively. Halos were more sensitive to SA induction for 5.0 mm pupils, and induction of positive SA (myopic LASIK) resulted in reduced halos with the EDOF when compared with the monofocal IOLs, by 1.62 (SA) and 1.86 arc min (SA + coma), on average.

CONCLUSIONS

Computer post-LASIK pseudophakic eye models showed that the DOF was less dependent on the presence of SA and coma with EDOF IOLs and that halos were reduced with EDOF IOLs compared with the monofocal IOL for a range of SA.

Visual performance and impact of residual refractive errors with trifocal intraocular lenses of different aspheric design

BACKGROUND

To assess the visual quality and the tolerance to low refractive errors of two trifocal intraocular lenses (IOL) with different amounts of spherical aberration (SA).

METHODS

The study included patients having bilateral implantation of the AcrySof® IQ PanOptixTM (aberration-correcting) or the RayOneTM (aberration-free) Trifocal IOL. Three months after the surgery patients underwent: monocular/binocular and uncorrected/corrected distance visual acuity (VA) and binocular defocus curves. Binocular contrast sensitivity (CSF) and subjective halo perception were assessed with the best distance correction (CDVA), with a positive defocus of + 0.50D and with a negative defocus of -0.50D. Patient's satisfaction was evaluated with the Catquest9-SF questionnaire.

RESULTS

This study included 54 eyes (28 with PanOptix and 26 with RayOne) of 27 patients. Both groups achieved corrected/uncorrected and monocular/binocular distance VA values better than 0.0 logMAR (1.0 decimal) with no statistically significant differences between them (p > 0.05 for all cases). Defocus curves showed a VA of 0.1 logMAR or better between -2.5 and + 1.0D with no differences between groups (p > 0.05 at all distances). Overall CSF values remained stable under the induced residual refractions for both groups. The halo effect remained stable for the PanOptix group but increased with myopization in the RayOne group (p = 0.02). The questionnaire showed high rates of patient's satisfaction with no differences between groups.

CONCLUSION

Both lenses showed overall good visual outcomes and offered high rates of patient's satisfaction. Moreover, in normal patients with trifocal IOLs, the combination of residual refractive errors and certain amounts of SA may increase some visual disturbances.

On the Relationship between Corneal Biomechanics, Macrostructure, and Optical Properties

Optical properties of the cornea are responsible for correct vision; the ultrastructure allows optical transparency, and the biomechanical properties govern the shape, elasticity, or stiffness of the cornea, affecting ocular integrity and intraocular pressure. Therefore, the optical aberrations, corneal transparency, structure, and biomechanics play a fundamental role in the optical quality of human vision, ocular health, and refractive surgery outcomes. However, the inter-relationships of those properties are not yet reported at a macroscopic scale within the hierarchical structure of the cornea. This work explores the relationships between the biomechanics, structure, and optical properties (corneal aberrations and optical density) at a macro-structural level of the cornea through dual Placido–Scheimpflug imaging and air-puff tonometry systems in a healthy young adult population. Results showed correlation between optical transparency, corneal macrostructure, and biomechanics, whereas corneal aberrations and in particular spherical terms remained independent. A compensation mechanism for the spherical aberration is proposed through corneal shape and biomechanics.

Recent advances in measurement of monochromatic aberrations of human eyes

The field of aberrations of the human eye is moving rapidly, being driven by the desire to monitor and optimise vision following refractive surgery. It is important for ophthalmologists and optometrists to have an understanding of the magnitude of various aberrations and how these are likely to be affected by refractive surgery and other corrections. In this paper, I consider methods used to measure aberrations, the magnitude of aberrations in general populations and how these are affected by various factors (for example, age, refractive error, accommodation and refractive surgery) and how aberrations and their correction affect spatial visual performance.

Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology

As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.

Corneal Topography for Intraocular Lens Selection in Refractive Cataract Surgery

The purpose of this review is to evaluate the usefulness of corneal topography to select premium intraocular lenses (IOLs), including aspherical IOLs, toric IOLs, and multifocal IOLs, in refractive cataract surgery. Corneal topography can detect corneal regular astigmatism, corneal irregular astigmatism (higher-order aberrations [HOAs]) including spherical aberration, and corneal shape abnormalities after corneal refractive surgery. Surgeons can explain to the patients with significant corneal HOAs about its effect on postoperative visual function before surgery. Multifocal IOLs should not be selected for such eyes. For eyes with abnormal corneal shape, appropriate IOL power calculation formulae can be applied. In the case of toric IOLs, regular astigmatism and corneal HOAs should be checked. Before implanting an aspheric IOL, it is ideal to confirm spherical aberration of the cornea is not below the normal range. Because corneal HOAs, abnormal corneal shape after corneal refractive surgery, corneal regular astigmatism, and corneal spherical aberration increase postoperative refractive errors and poor vision quality with premium IOLs, corneal topography before cataract surgery is helpful in screening patients who are not appropriate candidates for premium IOLs.

The Pathogenesis and Treatment of Complications in Nanophthalmos

Microphthalmos is a type of developmental disorder ophthalmopathy, which can occur isolated or combined with other ocular malformations and can occur secondary to a systemic syndrome. Nanophthalmos is one of the clinical phenotypes of microphthalmos. Due to the special and complex structure of nanophthalmic eyes, the disorder is often associated with many complications, including high hyperopia, angle-closure glaucoma, and uveal effusion syndrome. The management of these complications is challenging, and conventional therapeutic methods are often ineffective in treating them. The purpose of this paper was to review the concept of nanophthalmos and present the latest progress in the study of the pathogenesis and treatment of its complications. As it is considerably challenging for ophthalmologists to prevent or treat these nanophthalmos complications, timely diagnosis and a suitable clinical treatment plan are vital to ensure that nanophthalmos patients are treated and managed effectively.

Hyperopic laser keratorefractive surgery: Do steep corneas have worse outcomes?

PURPOSE

To report the visual and refractive outcomes of hyperopic patients undergoing laser keratorefractive surgery in preoperatively steep corneas versus a matched control group.

METHODS

Retrospective cohort study. All patients underwent photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) at Care-Vision Laser Centers, Tel-Aviv, Israel, between 1/2000 and 11/2016. Patients were divided into two groups: steep corneas (mean keratometry ≥ 44.00 D) and control group (mean keratometry < 44.00 D). The two study groups were matched by age, gender, sphere and cylinder. Only the right eye of each patient was included. Outcomes included postoperative uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), safety and efficacy indexes, refractive outcomes and retreatment rates.

RESULTS

Five hundred and two patients were included. Both groups were similar in demographic data, visual acuity and refraction. Postoperatively, the steep corneas group had a significantly higher mean keratometry as compared to the control group (46.52 ± 1.43 D vs 44.58 ± 1.68 D, p < 0.001), K_min (46.04 ± 1.50 D vs 44.12 ± 1.76 D, p < 0.001) and K_max (46.99 ± 1.51 D vs 45.03 ± 1.77 D, p < 0.001). Both groups had similar postoperative UDVA and CDVA and achieved a similar final sphere (0.64 ± 0.19 vs 0.54 ± 1.19, p = 0.44) and cylinder (- 0.89 ± 0.59 vs - 0.86 ± 0.72, p = 0.67). Both groups had a similar efficacy index (0.92 ± 0.22 vs 0.90 ± 0.25, p = 0.33) and similar retreatment rates (4.2% vs 3.5%, p = 0.74). None of the patients in either group underwent more than one retreatment throughout the follow-up period.

CONCLUSIONS

Hyperopic patients with steep corneas undergoing laser keratorefractive surgery can achieve adequate visual and refractive outcomes, similar to control group.

Varifocal Versus Monofocal LASIK in Presbyopic Hyperopic Eyes

PURPOSE

To compare varifocal (SupraCor; Technolas Perfect Vision GmbH, Munich, Germany) to monofocal (Zyoptix TissueSaving; Bausch & Lomb, Rochester, NY) LASIK in patients with hyperopic presbyopia.

METHODS

In this prospective, non-randomized, comparative case series, consecutive patients with hyperopia, presbyopia, and emmetropia as target refraction were bilaterally treated with varifocal (8 patients) or monofocal (7 patients) LASIK. The study was designed for 35 patients, but was terminated early after interim analysis. Outcomes (preoperative and 1 day, 1 week, 1 month, and 3 months postoperative) were: monocular and binocular uncorrected near visual acuity (UNVA), distance-corrected near visual acuity (DCNVA), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), low-contrast UDVA and CDVA, efficacy, and safety.

RESULTS

Preoperative data were similar in both groups. Monocular and binocular UNVA were not significantly different between both groups at any follow-up visit. At 3 months, mean monocular UNVA was 0.40 logMAR in both groups. Monocular DCNVA and binocular CDVA were not significantly different between groups. Monocular mean CDVA was 0.00 ± 0.06 logMAR after varifocal LASIK and -0.06 ± 0.04 logMAR after monofocal LASIK. The efficacy index was 0.9 after vari-focal LASIK and 0.88 after monofocal LASIK (not significant). The safety index was 1.08 after varifocal LASIK and 1.125 after monofocal LASIK (not significant).

CONCLUSIONS

With emmetropia as target refraction, varifocal ablations yielded no additional benefit compared to monofocal ablations in hyperopic presbyopic LASIK. The authors speculate that epithelial remodeling masks the impact of a varifocal ablation pattern and that a myopic postoperative refraction (modified monovision) may be necessary to further improve near and intermediate vision. These results demonstrate the value of a control group in studies evaluating presbyopia corrections. [J Refract Surg. 2019;35(7):459-466.].

Presbyopia management with Q-factor modulation without additive monovision: One-year visual and refractive results

PURPOSE

To analyze refractive results after hyperopic presbyopia surgery by Q-factor modulation without additive monovision.

SETTING

Quinze-Vingts National Ophthalmology Hospital, Paris, France.

DESIGN

Prospective nonrandomized study.

METHODS

Forty-five hyperopic presbyopic patients not tolerating monovision were included. The target for the dominant eye was emmetropia, whereas that for the nondominant eye was emmetropia associated with a target Q factor of -0.8. The postoperative follow-up included assessments of spherical equivalent (SE) refraction, monocular and binocular corrected and uncorrected (UDVA) distance visual acuities, and binocular corrected and uncorrected (UNVA) near visual acuities. Corneal pachymetry, topography, aberrometry and an analysis of patient satisfaction were performed at the 12-month examination.

RESULTS

The study comprised 90 eyes of 45 consecutive patients. The mean age at surgery was 53.8 years ± 4.99 (SD). The mean preoperative SE was +2.33 ± 1.16 diopters (D) in the dominant eyes and +2.26 ± 1.17 D in the nondominant eyes. At 12 months postoperatively, 42 patients (93%) had a binocular UDVA of Snellen 20/20 and 37 patients (82%) had a binocular UNVA of Jaeger 2 (Parinaud 3). The mean SE at 12 months was -0.22 ± 0.35 D in the dominant eyes (P < .0001) and -0.83 ± 0.50 D in the nondominant eyes (P < .0001). Two eyes required retreatment. Overall, 39 patients (87%) said that they were satisfied and would recommend the intervention.

CONCLUSION

The Q-factor modulation without additive monovision aims to compensate for presbyopia by changing the Q factor of the nondominant eye to generate a greater depth of field in hyperopic presbyopic patients who are unable to tolerate monovision. The visual outcomes and quality of vision were satisfactory, and only a few patients required additional correction.

Changes of Functional Optical Zone After LASIK for Hyperopia and Hyperopic Astigmatism

PURPOSE

To evaluate which factors may influence the size of the postoperative functional optical zone after hyperopic LASIK.

METHODS

Thirty-three eyes with a mean spherical equivalent of +3.55 ± 1.28 diopters (D) underwent LASIK with a Technolas 217 C-LASIK laser (Bausch & Lomb Surgical, Munich, Germany). After 1 week and 1, 4, and 12 months, the authors examined refraction, corneal refractive power by means of computerized videokeratography (Technomed C-Scan; Baesweiler, Germany), and uncorrected/corrected distance visual acuity (UDVA/CDVA). According to the degree of hyperopia, they were divided into low hyperopia (spherical equivalent ≤ 3.00 D) and high hyperopia (spherical equivalent > 3.00 D) groups.

RESULTS

One year postoperatively, 82% of all eyes had a UDVA of 0.5 or better; in 88%, the spherical equivalent did not deviate more than 1.00 D from the attempted value. Three eyes were slightly undercorrected. After an initial overcorrection (-0.27 D) with subsequent regression, the refraction remained stable at +0.17 D from the fourth postoperative month (low hyperopia group: +0.14 D; high hyperopia group: +0.19 D after 1 year). After 1 year, the functional optical zone diminished by 32%; the reduction was more pronounced in eyes with higher hyperopia: -1.85 ± 1.09 mm (range: +0.5 to -3.4 mm) in the low hyperopia group (P < .0001) and -2.25 ± 1.24 mm (range: +1 to -3.9 mm) in the high hyperopia group (P < .0001). Preoperative spherical equivalent and preoperative corneal refractive power affected the postoperative size of the functional optical zone additively.

CONCLUSIONS

An expected small functional optical zone in high hyperopia may not be regarded as a compelling exclusion criterion, but can induce possible side effects such as glare and halos. [J Refract Surg. 2018;34(7):476-481.].

Presbyopic Correction Using Monocular Bi-aspheric Ablation Profile (PresbyMAX) in Hyperopic Eyes: 1-Year Outcomes

PURPOSE

To present the 1-year outcomes of combining monocular bi-aspheric ablation profile and contralateral monofocal LASIK in hyperopic patients with presbyopia.

METHODS

In this retrospective case series, 36 consecutive patients (72 eyes) who underwent simultaneous bi-aspheric ablation (PresbyMAX: SCHWIND Eye-Tech-Solutions GmbH and Co KG, Kleinostheim, Germany) in the non-dominant eye and monofocal regular LASIK in the dominant eye for correction of hyperopia and presbyopia were reviewed for 1 year. Binocular uncorrected distance (UDVA), near (UNVA), corrected distance (CDVA), and distance corrected near (DCNVA) visual acuity and manifest refraction were analyzed postoperatively.

RESULTS

At 1 year, the mean binocular UDVA improved significantly from 0.26 ± 0.25 to 0.039 ± 0.088 logMAR (P < .001). Binocular UNVA also improved from 0.73 ± 0.30 to 0.10 ± 0.22 logRAD (P < .001). Eighty-seven percent of patients achieved UDVA of 20/25 or better and 90% had UNVA of J3 or better. Simultaneous binocular distance and near vision of 20/25 and J2 or better was achieved in 70%. Only 17% of patients had a binocular DCNVA of J2 or better. No patient suffered from a loss of 2 lines of CDVA. Refractive stability was achieved for both eyes from 1 month postoperatively. The re-treatment rate was 14% for improvement of near vision within 6 months to 1 year.

CONCLUSIONS

Presbyopic correction using monocular PresbyMAX combined with monofocal regular LASIK in the fellow eye is safe and acceptable in hyperopic patients. [J Refract Surg. 2017;33(1):37-43.].

Changes to Corneal Aberrations and Vision After Monovision in Patients With Hyperopia After Using a Customized Aspheric Ablation Profile to Increase Corneal Asphericity (Q-factor)

PURPOSE

To evaluate the visual outcomes and fourth-order Zernike spherical aberrations induced with a customized change in corneal asphericity (ΔQ) correction of presbyopia combined with monovision for hyperopic patients.

METHODS

Consecutive hyperopic patients who underwent presbyopic LASIK between September 2013 and July 2014 were included. For the non-dominant eyes, the aspheric ablation profile associated with a myopic refraction was planned using the Custom-Q nomogram (Alcon Laboratories, Inc., Fort Worth, TX). Uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), spherical equivalent refraction, ΔQ, and change in corneal spherical aberration coefficient (ΔC₄⁰) were analyzed. Postoperative data were collected at 1, 3, and 6 months.

RESULTS

Sixty-five patients were included. The mean age was 56.5 ± 5.7 years (range: 47 to 70 years). At the 6-month follow-up, the spherical equivalent refraction for non-dominant and dominant eyes was -1.07 ± 0.74 and 0.32 ± 0.55 diopters (D), respectively. The mean binocular UDVA was 0.01 ± 0.04 logMAR (range: -0.12 to 0.30 logMAR); 91% of patients achieved 20/20 or better binocular UDVA and 83% of patients had Jaeger 3 (Parinaud 4) or better binocular UNVA. The ΔQ for non-dominant and dominant eyes was -0.61 ± 0.15 and -0.33 ± 0.25, respectively, for a 6-mm pupil diameter and was significantly higher for non-dominant eyes (P < .0001). The achieved ΔC₄⁰ was -0.49 ± 0.23 µm for non-dominant eyes (for a theoretical ideal value of -0.40 µm) and -0.30 ± 0.18 µm for dominant eyes. For non-dominant eyes, the attempted ΔQ (-0.60) was close to the achieved value (-0.61 ± 0.15).

CONCLUSIONS

For hyperopic patients, combining the customized corneal aspheric ablation profile with monovision is safe, effective, and reproducible, inducing intended changes in corneal spherical aberrations. [J Refract Surg. 2016;32(11):734-741.].

Hyperopic Q-optimized algorithms: a theoretical study on factors influencing optical quality

In this work, we analyze the way in which pupil size, optical zone, and initial hyperopic level influence optical quality for hyperopic Q-optimized corneal refractive surgery. Different Q-optimized algorithms and the Munnerlyn formula were tested to analyze the optical quality of the final retinal image for initial hyperopic errors from 1D to 5D. Three optical zones (5.5, 6, and 6.5 mm) and two pupil diameters (5 and 7 mm) were considered. To evaluate optical quality, we computed the modulation transfer function (MTF) and the area under MTF (MTFa). Q-optimized values at around Q = -0.18 were found to provide the best optical quality for most of the conditions tested. This optimum final asphericity for hyperopic ablation was not depending on the degree of hyperopia corrected, the optical zone or the pupil size being this information important for clinical practice.

Changes in Keratometric Values and Corneal High Order Aberrations After Hydrogel Inlay Implantation

PURPOSE

We sought to analyze surgically induced refractive change (SIRC) and change in high-order aberration after Raindrop corneal inlay insertion (ReVision Optics, Lake Forest, CA), and assess the extent to which Raindrop corneal inlay insertion could correct presbyopia.

DESIGN

Interventional case series.

METHODS

Seventeen patients were included if they had a corneal thickness ≥500 μm and a stable manifest spherical equivalent refraction between 0.50 and +1.00 diopters (D). The Raindrop corneal inlay was implanted on the stromal bed of a femtosecond laser-assisted generated flap of nondominant eyes. Manifest refraction, corneal powers, and corneal high-order aberrations were measured preoperatively and at 3 and 12 months postoperatively.

RESULTS

The SIRC by manifest refraction was 0.99 ± 0.26 D. The changes derived from simulated keratometry (K), true net power, and equivalent K reading (EKR) at 1.0-4.0 mm were greater than the SIRC (all P < .01) while the change in EKR at 6.0 mm was less than the SIRC (P < .01). The changes in EKR 5.0 mm, automated K, and EKR 4.5 mm did not differ significantly from the SIRC (P = .81, .29, and .09, respectively), and the difference was the least for EKR 5.0 mm. In analysis of high-order aberrations, only spherical aberration showed statistically significant difference between preoperative and postoperative on both anterior cornea and total cornea (all P < .01).

CONCLUSION

Raindrop corneal inlay corrects presbyopia via increasing negative spherical aberration. The equivalent K reading at 5.0 mm accurately reflected the SIRC, and would be applicable for intraocular power prediction before cataract surgery.

Factors Predicting the Need for Retreatment After Laser Refractive Surgery

PURPOSE

To identify the potential risk factors that increase the likelihood of requiring retreatment after refractive surgery.

METHODS

This retrospective study included patients who underwent laser in situ keratomileusis or photorefractive keratectomy between January 2005 and December 2012 at the Care-Vision Laser Centers, Tel-Aviv, Israel. Patients were divided into 2 groups according to whether they underwent additional refractive surgery (retreatment) during the study period.

RESULTS

Overall, 41,504 eyes (n = 21,313) were included in the final analysis of this study. Throughout the study period, there was a significant reduction in the 2-year annual retreatment rates with a decline from 4.52% for primary surgeries done in 2005 to 0.18% for surgeries performed in 2012 (quadratic R = 0.96, P < 0.001). The retreatment group had significantly higher preoperative age, maximum keratometric power, sphere, cylinder, and better best-corrected visual acuity. They were more likely to have preoperative hyperopia, photorefractive keratectomy as opposed to laser in situ keratomileusis, intraoperative higher humidity conditions and lower temperature, and higher ablation depths. Significant differences in retreatment rates were found between the 5 high-volume surgeons (>1500 procedures performed) ranging from 0.48 to 3.14% (P < 0.0001). Multiple logistic regression analysis demonstrated that age, astigmatism, hyperopia, temperature, and surgeon's experience all significantly affected the need for retreatment.

CONCLUSIONS

The following factors significantly increase the need for refractive retreatment: older preoperative age, higher degrees of astigmatism, hyperopia, colder operating room temperature, and less surgeon experience. Some of these factors may be incorporated into nomograms to reduce future retreatment rates.

Laser in Situ Keratomileusis for High Hyperopia with Corneal Vertex Centration and Asymmetric Offset

Purpose

To investigate refractive outcomes and induction of corneal higher order aberrations (HOA) in eyes that underwent laser-assisted in situ keratomileusis (LASIK) for high hyperopia correction using an aberration neutral profile with corneal vertex centration and asymmetric offset.

Methods

A total of 24 consecutive patients (38 eyes) who underwent LASIK by one surgeon using AMARIS 750S excimer laser and a Carriazo-Pendular microkeratome for flap creation were retrospectively analyzed. Eyes targeted for plano and with correction in the maximum hyperopic meridian strictly higher than +4D were included in the retrospective analysis. Patients were reviewed at 1, 3, and 6 months postoperatively. Postoperative monocular corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA), manifest refraction, and corneal wavefront aberrations were compared with respective preoperative metrics.

Results

Mean preoperative spherical equivalent and refractive astigmatism was +4.07 ± 0.90 D and 1.37 ± 1.26 D, respectively, reducing to +0.28 ± 0.58D (p<0.0001) and 0.49 ± 0.47 D (p = 0.0001) at the last postoperative visit. Six months postoperatively, 78% of eyes achieved a UDVA of 20/25 or better. No eye lost more than 2 Snellen lines of CDVA at any follow-up. There was a statistically significant induction of vertical trefoil (+0.104 ± 0.299 µm, p<0.05), vertical coma (-0.181 ± 0.463 µm, p<0.01), horizontal coma (+0.198 ± 0.663 µm, p<0.05), spherical aberration (-0.324 ± 0.281 µm, p<0.0001), secondary vertical trefoil (+0.018 ± 0.044 µm, p<0.01), and secondary horizontal coma (+0.026 ± 0.083 µm, p<0.05)

Conclusions

Laser-assisted in situ keratomileusis for high hyperopia using corneal vertex centration with asymmetric offset results in significant improvement in refraction and visual acuity although affected by significant induction of some higher order aberrations.

Control of Induced Spherical Aberration in Moderate Hyperopic LASIK by Customizing Corneal Asphericity

PURPOSE

To compare differences in induced aberrations and visual acuity after wavefront-optimized LASIK and aspheric-customized LASIK for the treatment of hyperopia.

METHODS

Forty consecutive eyes underwent uneventful LASIK for treatment of moderate hyperopia (+3.82 ± 0.63 diopters [D] [+2.75; +5.125]). A standard procedure was performed in the wavefront-optimized LASIK group (n = 24), whereas a postoperative Q-factor equal to zero was scheduled in the aspheric-customized LASIK group (n = 16).

RESULTS

At 6 months, mean spherical aberration for a 6-mm pupil diameter was -0.39 ± 0.23 µm (range: -0.76 to 0.01 µm) and Q-factor was -0.52 ± 0.22 (range: -1.00 to -0.12 µm) in the wavefront-optimized group and 0.04 ± 0.18 µm (range: -0.34 to 0.29 µm) and -0.04 ± 0.25 (range: -0.64 to 0.40 µm) in the aspheric-customized LASIK group (P ≤ .05). All remaining outcomes showed no significant differences between groups. UDVA was 20/18.69 ± 0.15 (range: 0.80 to 1.20) in the wavefront-optimized LASIK group and 20/20 ± 0.17 (range: 0.50 to 1.20) in the aspheric-customized LASIK group. One patient in the wavefront-optimized LASIK group lost two or more lines of CDVA and no lines were lost in the aspheric-customized LASIK group.

CONCLUSIONS

The results in this small cases series suggest that using an aspheric-customized ablation profile with a target Q-factor equal to 0 in moderate hyperopic LASIK is statistically compatible with a diminishing induced spherical aberration without altering procedural safety when the WaveLight Allegretto 400-Hz excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX) is used.

Hydrogel Inlay for Presbyopia: Objective and Subjective Visual Outcomes

PURPOSE

To evaluate changes in visual performance and ocular optical quality after implantation of a corneal hydrogel inlay as a treatment for presbyopia.

METHODS

A Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, CA) was implanted monocularly on the stromal bed of a femtosecond laser-assisted generated corneal flap of non-dominant eyes of 22 patients with emmetropic presbyopia (preoperative spherical equivalent range: -0.50 to 1.00 diopters). Efficacy was determined by measuring near and distance visual acuities and ocular aberrations, and satisfaction was assessed by a patient questionnaire.

RESULTS

The preoperative monocular uncorrected near visual acuity of the inlay inserted eye was 20/129 ± 1 Snellen (range: 20/135 to 20/61 Snellen) and improved to 20/35 ± 2 Snellen (range: 20/61 to 20/20 Snellen) (P < .01) at 6 months postoperatively. The monocular uncorrected distance visual acuity of the eye receiving the inlay was 20/25 ± 2 Snellen (range: 20/50 to 20/20 Snellen) preoperatively and 20/25 ± 1 Snellen (range: 20/50 to 20/20 Snellen) at 6 months postoperatively (P =.257). According to the questionnaire responses, 82% of patients were satisfied. This was despite near glasses needs remaining in 13.6% of the cohort and the presence of glare and a decrease in night vision in approximately 40% of patients. The primary spherical aberration coefficient Z4(0) changed from positive to negative values in all patients (P < .01). However, the point spread function showed no significant change.

CONCLUSIONS

Hydrogel corneal inlays improve uncorrected near visual acuity in patients with presbyopia with only moderate effect on visual quality. However, the satisfaction with this therapy was relatively lower in these Korean patients than that reported previously in Western patients.

Focus correction in an apodized system with spherical aberration

We performed a theoretical and computational analysis of the through-focus axial irradiance in a system with a Gaussian amplitude pupil function and fourth- and sixth-order spherical aberration (SA). Two cases are analyzed: low aberrated systems, and the human eye containing significant levels of SA and a natural apodization produced by the Stiles-Crawford effect. Results show that apodization only produces a refraction change of the plane that maximized the Strehl ratio for eyes containing significant levels of negative SA.

Computational aspects of the through-focus characteristics of the human eye

Calculating through-focus characteristics of the human eye from a single objective measurement of wavefront aberration can be accomplished through a range of methods that are inherently computationally cumbersome. A simple yet accurate and computationally efficient method is developed, which combines the philosophy of the extended Nijboer-Zernike approach with the radial-basis-function-based approximation of the complex pupil function. The main advantage of the proposed technique is that the increase of the computational cost for a vector-valued defocus parameter is practically negligible in comparison to the corresponding scalar-valued defocus parameter.

Corneal curvature gradient map: a new corneal topography map to predict the corneal healing process

PURPOSE

To evaluate a new curvature gradient topography map to predict postoperative corneal remodeling.

METHODS

In this retrospective study, 32 eyes of 16 patients with myopia underwent excimer ablation surgery with a postoperative high curvature gradient. The new curvature gradient map (acquired immediately postoperatively) shows the difference between the curvatures of two points over the distance between them; it was compared to the tangential curvature difference map between 1 and 12 months postoperatively to determine their relationship. Corneas were divided into 12 regions for analysis: four 90°-wide sectors centered on 0°, 90°, 180°, and 270°. There were three subdivisions in each sector: central (radius: 0 to 2.75 mm), paracentral (radius: 2.75 to 3.25 mm), and peripheral (radius: 3.25 to 4.5 mm). Linear regression analysis was performed by region.

RESULTS

The following regions had significant relationships between the initial curvature gradient and curvature difference between 1 and 12 months postoperatively: the paracentral zone of the 90° sector (P = .0145; R(2) = 0.1832) and both the central (P = .0034; R(2) = 0.2522) and paracentral (P = .0452; R(2) = 0.1271) zones of the 270° sector. The greatest average initial tangential curvature was in the 270° sector.

CONCLUSIONS

The initial curvature gradient after surgery predicted change in tangential curvature over the subsequent 12 months in areas where initial tangential curvature was greatest. When the curvature gradient was high, the surface curvature modification remained in progress months after surgery.

Changes in spherical aberration after various corneal surface ablation techniques

Purpose

The corneal change induced by refractive procedures influence both the postoperative refractive status and the ocular spherical aberration (SA). We evaluated changes in corneal SA after three types of surface ablation: phototherapeutic keratectomy (PTK), myopic photorefractive keratectomy (PRK), and myopic wavefront-guided laser epithelial keratomileusis (LASEK).

Methods

Twenty-six eyes (25 patients) were subjected to PTK 26 eyes (14 patients) to PRK, and 34 eyes (17 patients) to wavefront-guided LASEK. Corneal SA was measured with the iTrace in all patients both preoperatively and 6 months postoperatively.

Results

Six months after surgery, mean corneal SA was -0.173 ± 0.171 µm in the PTK group, 0.672 ± 0.200 µm in the PRK group, and 0.143 ± 0.136 µm in the wavefront-guided LASEK group. The mean difference between the preoperative and postoperative corneal SA (ΔSA) was -0.475 µm in the PTK group, 0.402 µm in the PRK group, and -0.143 µm in the wavefront-guided LASEK group.

Conclusions

Surgically induced changes in corneal SA vary with procedure. The prediction of the pattern of SA change induced by various surface ablation procedures may be helpful for developing future surgical procedures.

Laser in situ keratomileusis for high hyperopia (>5.0 diopters) using optimized aspheric profiles: efficacy and safety

PURPOSE

To evaluate the clinical outcomes of laser in situ keratomileusis (LASIK) for high hyperopia using an excimer laser and optimized aspheric profiles.

SETTING

Vissum Corporation and Miguel Hernández University, Alicante, Spain, and Research Institute of Ophthalmology, Giza, Egypt.

DESIGN

Case series.

METHODS

Eyes of patients with high hyperopia or hyperopic astigmatism (spherical equivalent [SE] ≥ 5.64 diopters [D]) had uneventful LASIK with an aspheric optimized ablation profile centered on the corneal vertex using an Amaris 500 kHz excimer laser and a femtosecond platform for flap creation with a temporal hinge.

RESULTS

There was a significant improvement in uncorrected distance visual acuity 3 months postoperatively (P<.01), with no significant changes afterward (P=.72). At 6 months, the corrected distance visual acuity (CDVA) remained unchanged or improved in 90.48% of eyes; 2 eyes (9.52%) lost 2 lines of logMAR CDVA. The postoperative SE was within ± 0.50 D of emmetropia in 70.37% of eyes. The LASIK enhancement rate at the end of the follow-up was 29.4%. Significant induction of corneal primary spherical aberration and coma was found with 6.0 mm pupils (P<.01). The safety index was 0.94 and the efficacy index, 0.85.

CONCLUSION

Laser in situ keratomileusis for high hyperopia using optimized aspheric profiles requires further improvement in terms of safety but was still an effective and a predictable procedure.

Visual simulation through an aspheric aberration-correcting intraocular lens in subjects with different corneal profiles using adaptive optics

BACKGROUND

The aim of this study was to analyse the visual quality of the AcrySof IQ SN60WF(®) intraocular lens (IOL) when combined with different corneal profiles.

METHODS

Ten eyes of 10 participants with no prior history of refractive or cataract surgery were evaluated. An adaptive optics visual simulator was used to simulate the wavefront aberration pattern of an aspheric aberration-correcting IOL (AcrySof IQ SN60WF(®)). Normal corneas (group A), low and high myopic corneal ablations (groups B and C, respectively) and low and high hyperopic corneal ablations (groups D and E, respectively) were also simulated. Monocular distance visual acuities at 100, 50 and 10 per cent of contrast were measured.

RESULTS

At 100, 50 and 10 per cent contrast, no differences were found between groups A and B (p > 0.06 for all contrasts). Group A obtained better values than groups C, D and E for all contrasts (p = 0.031, p = 0.038, p = 0.032 at 100, 50 and 10 per cent of contrast, respectively). At the same time, group B obtained better values than groups C, D and E (p = 0.041, p = 0.042, p = 0.036 at 100, 50 and 10 per cent of contrast, respectively). Within the five groups, the worst results were always obtained for group E (p = 0.017, p = 0.021 and p = 0.025 at 100, 50 and 10 per cent of contrast, respectively).

CONCLUSIONS

The results suggest that the aspheric aberration-correcting IOL studied provides comparable results, when it is combined with normal corneas and with corneas with simulated low myopic ablations. When negative amounts of residual spherical aberration after cataract surgery are expected to be achieved, IOLs with more positive spherical aberration should be considered.

Pilot study of hyperopic LASIK using the solid-state laser technology

BACKGROUND

To evaluate and report the visual, refractive, and aberrometric outcomes of LASIK for the correction of low to moderate hyperopia in a pilot group using a commercially available solid-state laser

METHODS

Prospective pilot study including 11 consecutive eyes with low to moderate hyperopia of six patients undergoing LASIK surgery using the Pulzar Z1 solid-state laser (CustomVis Laser Pty Ltd., currently CV Laser). Visual, refractive, and aberrometric changes were evaluated. Potential complications were evaluated as well. Mean follow-up time was 6.6 months (range, 3 to 11 months).

RESULTS

A significant improvement in LogMAR uncorrected distance visual acuity (UDVA) was observed postoperatively (p = 0.01). No significant change was detected in LogMAR corrected distance visual acuity (CDVA) (p = 0.21). Postoperative LogMAR UDVA was 0.1 (about 20/25) or better in ten eyes (90.9 %). Mean overall efficacy and safety indices were 1.03 and 1.12. Postoperatively, no losses of lines of CDVA were observed. Postoperative spherical equivalent was within ± 1.00 D in ten eyes (90.9 %). With regard to aberrations, no statistically significant changes were found in higher order and primary coma RMS postoperatively (p ≥ 0.21), and only minimal but statistically significant negativization of primary spherical aberration (p = 0.02) was observed. No severe complications were observed.

CONCLUSION

LASIK surgery using the solid-state laser technology seems to be a useful procedure for the correction of low to moderate hyperopia, with minimal induction of higher order aberrations.

Depth of focus through different intraocular lenses in patients with different corneal profiles using adaptive optics visual simulation

PURPOSE

To evaluate the depth of focus with monofocal intraocular lenses (IOLs) in patients with different corneal profiles using adaptive optics (AO) visual simulation.

METHODS

An AO visual simulator (crx1, Imagine Eyes) was used to simulate the aberration pattern of three monofocal IOLs (Acrysof IQ SN60WF [Alcon Laboratories Inc]; Akreos Adapt AO [Bausch & Lomb]; and Triplato [AJL Ophthalmic]) of different optic designs. Five groups were considered: patients without any corneal refractive surgery (normal cornea group) and with prior low and high myopic and hyperopic ablations (low myopic ablation, high myopic ablation, low hyperopic ablation, and high hyperopic ablation groups). Defocus curves for all situations were measured, with the target being moved from -5.00 to +2.50 diopters (D) in 0.25-D steps, and visual acuity was measured at all vergences.

RESULTS

Ten eyes from 10 patients were evaluated. The higher residual spherical aberration (SA) for all IOLs was obtained for the high myopic ablation group and the most negative residual SA was obtained for the high hyperopic ablation group. The best compromise between distance visual and depth of focus for the normal cornea, low myopic ablation, and high myopic ablation groups was obtained with the aspheric designs, whereas the best results for the low hyperopic and high hyperopic ablation groups were obtained with the spherical IOL.

CONCLUSIONS

The results of this study suggest that the better compromise between distance visual acuity and depth of focus with the three IOLs and the different corneal profiles relies on a certain amount of positive SA. Above a certain limit of residual SA (positive or negative), visual acuity decreases at all vergences, worsening the depth of focus.

[Monochromatic aberration in accommodation. Dynamic wavefront analysis]

BACKGROUND

Monochromatic aberrations may influence the visual acuity of the eye. They are not stable and can be affected by different factors. The subject of the following paper is the dynamic investigation of the changes in wavefront aberration with accommodation.

METHOD

Dynamic measurement of higher and lower order aberrations was performed with a WASCA Wavefront Analyzer (Carl-Zeiss-Meditec) and a specially constructed target device for aligning objects in far and near distances on 25 subjects aged from 15 to 27 years old.

RESULTS

Wavefront aberrations showed some significant changes in accommodation. In addition to the characteristic sphere reaction accompanying miosis and changes in horizontal prism (Z(1) (1)) in the sense of a convergence movement of the eyeball also occurred. Furthermore defocus rose (Z(2) (0)) and astigmatism (Z(2) (-2)) changed. In higher-order aberrations a decrease in coma-like Zernike polynomials (Z(3) (-1), Z(3) (1)) was found. The most obvious change appeared in spherical aberration (Z(4) (0)) which increased and changed from positive to negative. In addition the secondary astigmatism (Z(4) (-2)) and quadrafoil (Z(4) (4)) rise also increased. The total root mean square (RMS), as well as the higher-order aberrations (RMS-HO) significantly increased in accommodation which is associated with a theoretical reduction of visual acuity. An analysis of the influence of pupil size on aberrations showed significant increases in defocus, spherical aberration, quadrafoil, RMS and RMS HO by increasing pupil diameter. By accommodation-associated miosis, the growing aberrations are partially compensated by focusing on near objects. Temporal analysis of the accommodation process with dynamic wavefront analysis revealed significant delays in pupil response and changing of prism in relation to the sphere reaction. In accommodation to near objects a discrete time ahead of third order aberrations in relation to the sphere response was found.

CONCLUSION

Using dynamic wavefront measurement achieved a sequential analysis of aberrations during accommodation. Significant changes in the lower and higher-order aberrations could be detected. These are additionally varied by the associated pupillary response. Moreover, the synchronicity of wave front reaction in the accommodation process was proven.

Wavefront analysis and Zernike polynomial decomposition for evaluation of corneal optical quality

Wavefront-guided excimer laser refractive surgery and new customized intraocular lens and contact lens designs are major clinical applications of corneal wavefront analysis. Other therapeutic applications include corneal disorders, conventional excimer laser refractive surgery, incisional techniques and cataract surgery, corneal transplantation, intrastromal corneal ring segment implantation, and crosslinking therapy. Basic data regarding corneal wavefront aberrations, such as distribution in the population and changes with aging, are essential for understanding the nature of each aberration and correcting it. Corneal aberrometry also improved our comprehension of the optical effects of the aforementioned topics while helping us assess the success of the procedures. Zernike polynomials are representations of the higher- and lower-order aberrations of the cornea, allowing a mathematical approach to their determination. Polynomials are used to model individual components of the wavefront in familiar terms. This article reviews the current knowledge of the wavefront aberrations of the human cornea and analyzes studies in the fields of anterior segment surgery and/or therapy, diseases, and optical quality in the context of this knowledge.

Aspheric Optical Zones in hyperopia with the SCHWIND AMARIS

Purpose

To evaluate the corneal Functional Optical Zone (FOZ) and the Effective Optical Zone (EOZ) of the ablation, among eyes that underwent LASEK/Epi-LASEK treatments for hyperopic astigmatism.

Methods

Twenty LASEK/Epi-LASEK treatments with mean defocus +2.21 ± 1.28 D performed using the SCHWIND AMARIS were retrospectively evaluated at 6-month follow-up. In all cases pre-/post-operative Corneal-Wavefront analyses using the Keratron-Scout (OPTIKON2000) were performed. FOZ-values were evaluated from the Root-Mean-Square of High-Order Wave-Aberration (RMSho), whereas EOZ-values were evaluated from the changes of Root-Mean-Square of High-Order Wave-Aberration (ΔRMSho) and Root-Mean-Square of the change of High-Order Wave-Aberration (RMS(ΔHOAb)). Correlations of FOZ and EOZ with Planned Optical Zone (POZ) and Defocus correction (SEq) were analyzed using a bilinear function.

Results

At six-month, defocus was −0.04 ± 0.44 D, ninety percent eyes were within ± 0.50 D from emmetropia. Mean RMSho increased 0.18 ± 0.22 μm, SphAb −0.30 ± 0.18 μm, and Coma 0.07 ± 0.18 μm 6-month after treatment (6-mm diameter). Mean FOZPre was 7.40 ± 1.48 mm, mean POZ was 6.76 ± 0.22 mm, whereas mean FOZPost was 5.53 ± 1.18 mm (significantly smaller, p < 0.0001; bilinear correlation p < 0.005), mean EOZΔRMSho 6.47 ± 1.17 mm (bilinear correlation p < 0.005), EOZRMS(ΔHOAb) 5.67 ± 1.23 mm (significantly smaller, p < 0.0005; bilinear correlation p < 0.05). EOZ positively correlates with POZ and declines steadily with SEq. A treatment of +3 D in 6.50-mm POZ results in 5.75-mm EOZ (7.75-mm NPOZ), treatments in 7.00-mm POZ result in about 6.25-mm EOZ (8.25-mm nomogrammed POZ).

Conclusions

FOZPost was significantly smaller than FOZPre. EOZΔRMSho was similar to POZ, whereas EOZRMS(ΔHOAb) was significantly smaller. Differences were larger for smaller POZ or larger Defocus. SEq up to +2 D result in EOZ, at least, as large as POZ. For SEq higher than +2 D, a nomogram for OZ can be applied.

Temporal evolution of ocular aberrations following laser in situ keratomileusis

PURPOSE

To study the temporal evolution of ocular aberrations after standard LASIK to correct myopia.

METHODS

The ocular, corneal and internal aberrations for a 6-mm pupil were measured in 22 young myopic eyes (n = 12 subjects; range -2.0 to-7.6 D) before and during a 9-month follow-up after standard myopic LASIK. Ocular aberrations were measured with a Hartmann-Shack wavefront sensor, while corneal aberrations were estimated from the elevation data obtained by corneal topography. For every patient and condition the eye's modulation transfer function (MTF) and Strehl ratio (SR) were calculated.

RESULTS

Compared to preoperative results, we found that standard myopic LASIK produced a significant increase of ocular high-order aberrations at 1 month after surgery. During the next 8 months, we found a small increase of ocular and corneal positive spherical aberration (SA), although with a large inter-subject variability. However, all eyes treated for myopia higher than -5 D showed a significant increase of positive SA during the first 6 months after surgery.

CONCLUSIONS

Standard myopic LASIK decreases ocular optical quality. For most subjects, the increase in aberrations induced by the surgery was stable during the next 9 months after LASIK. However, further changes of the ocular SA after myopic LASIK are possible in patients treated for higher amounts of myopia. The changes in aberrations mainly appeared between the first and the sixth month after surgery, which suggests the need to wait at least 6 months after myopic LASIK before comparing outcomes, especially for patients treated for higher myopias.

[The influence of eye movements on monochromatic wavefront aberrations]

BACKGROUND

Wavefront-guided corneal surgery is a standard therapeutic option for correcting refractive errors. If the wavefront measured preoperatively is influenced by an incorrect alignment of the bulb, the ablation profile could be distorted and the quality of vision reduced.

METHOD

Wavefront analysis was done on 49 eyes, examining the primary gaze of the bulb as well as abduction, adduction, elevation, and depression.

RESULTS

The study demonstrated a significant influence of eye movements on astigmatic aberrations. Horizontal eye movements have a stronger influence than vertical ones do. Adduction especially leads to changes; here, RMS showed a significant difference.

CONCLUSIONS

Eye movements have a significant effect on wavefront profiles. The amount of aberration induced is generally very low. In individual cases, the numbers of aberrations induced by eye movements are in ranges reported to reduce the postoperative quality of vision when the ablation profile is taken into account.

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.