Small Incision Lenticule Extraction (SMILE) for the Correction of High Myopia With Astigmatism

PURPOSE

To report the outcomes of small incision lenticule extraction (SMILE) for high myopia between -9.00 and -14.00 diopters (D).

METHODS

This was a prospective study of SMILE for high myopia using the VisuMax femtosecond laser (Carl Zeiss Meditec). Inclusion criteria were attempted spherical equivalent refraction (SEQ) between -9.00 and -14.00 D, cylinder up to 7.00 D, corrected distance visual acuity (CDVA) of 20/40 or better, age 21 years or older, and suitable for SMILE. The sub-lenticule thickness was 220 µm or greater, and the total uncut stromal thickness was 300 µm or greater. Patients were to be followed up for 1 year. Standard outcomes analysis was performed using 12-month data where available or 3-month data otherwise.

RESULTS

Of 187 eyes treated, data were available at 12 months for 181 eyes (96.8%) and 3 months for 4 eyes (2.1%), and 2 eyes (1.1%) were lost to follow-up. Mean attempted SEQ was -10.55 ± 1.00 D (range: -9.00 to -12.99 D). Mean cylinder was -1.19 ± 0.83 D (range: 0.00 to -4.00 D). Preoperative CDVA was 20/20 or better in 73% of eyes. Postoperative uncorrected distance visual acuity was 20/20 or better in 57% and 20/25 or better in 82% of eyes. Mean SEQ relative to target was -0.22 ± 0.48 D (range: -1.63 to +1.38 D), 66% ± 0.50 D and 93% ±1.00 D. Mean SEQ 12-month change was -0.08 ± 0.34 D (range: -1.75 to +0.88 D). There was loss of one line of CDVA in 4% of eyes, and no eyes lost two or more lines. Contrast sensitivity was unchanged. Patient satisfaction was 8 or more out of 10 in 94% and 6 or more in 99% of patients.

CONCLUSIONS

Outcomes of SMILE for myopia greater than -9.00 D at 3 to 12 months showed excellent efficacy, safety, stability, and predictability, with high patient satisfaction. [J Refract Surg. 2022;38(5):262-271.].

Effect of refractive surgery on binocular vision and ocular alignment in patients with manifest or intermittent strabismus

OBJECTIVE

To evaluate the effect of refractive surgery on binocular vision and ocular alignment in patients with manifest or intermittent strabismus, with or without vertical component.

SETTING

University Hospital Antwerp, Edegem, Belgium.

PATIENTS AND METHODS

13 patients (22 eyes) with strabismus underwent refractive surgery. Five of these patients presented with an esotropia and four of them with a small vertical deviation. Five patients had a manifest exotropia, of whom two presented with a small vertical deviation. Two patients had an intermittent exotropia with binocular vision, of whom one patient had a vertical deviation. One patient had a hypertropia with a dissociated vertical deviation.

RESULTS

Ocular alignment and binocular function remained unchanged postoperatively in all except two patients with high anisometropia who experienced an improvement in binocular function. In these patients, the preoperative manifest deviation became intermittent or latent after surgery, allowing fusion and stereopsis. Vertical deviation was found preoperatively in 8 of the 13 patients. This vertical deviation remained unchanged postoperatively, but improved in one patient with anisometropia.

CONCLUSION

Preoperative intermittent or manifest strabismus is not a contraindication for refractive surgery provided some specific recommendations are taken into account, such as an adequate preoperative orthoptic examination and aiming at emmetropia for both eyes.

The 2014 Bowman Lecture-Bowman's and Bruch's: a tale of two membranes during the laser revolution

To describe the historical evolution of the role of lasers in effecting therapeutic changes in the four acellular membranes of the eye. Over the past 50 years, iterative developments have been instituted in lasers used for various forms of eye surgery predominately on the basis of data generated in early experiments in the 1960s to determine thresholds for damage and their incorporation in codes of practice for laser safety. The evolutionary steps are described. Excimer laser technology resulted in the generation of the new field of laser refractive surgery with over 40 million individuals now having undergone procedures such as photorefractive keratectomy and LASIK. Developments in lasers used for various forms of retinal surgery have undergone changes involving shorter and shorter pulse durations together with changes in beam energy distribution with implications for potential intervention in AMD prophylactically. Lasers have made a major impact on surgical treatment on all four acellular membranes of the eye but particularly Bowman's membrane in refractive surgery, where it has been demonstrated that it can be removed without significant consequences for eye health or vision.

Racial Differences in Central Corneal Thickness and Refraction Among Refractive Surgery Candidates

PURPOSE

To examine the preoperative central corneal thickness and refractive status of Caucasians, Hispanics, Asians, and African Americans in a refractive surgery patient population.

METHODS

In a retrospective case series, a total of 803 consecutive eyes, which had no history of anterior segment surgery, underwent central corneal thickness and refraction measurement as part of a preoperative evaluation for refractive surgery from December 1999 to October 2002. Preoperative central corneal thickness was measured by a DGH-550 ultrasonic pachymeter, and spherical equivalence was determined by manifest refraction.

RESULTS

This study included Caucasian (34.4%), Hispanic (34.5%), Asian (20.7%), African American (8.9%), and other (1.5%) patients. A one-way analysis of variance (ANOVA) revealed no significant differences in the central corneal thickness measurements among Asians, Hispanics, and Caucasians. However, mean central corneal thickness was 14 microm thinner in African Americans compared to Caucasians, and was significantly different at the 95% confidence interval. A one-way ANOVA revealed a significant difference in the preoperative spherical equivalence among the four groups (F=4.91; df=3; P<.05) but no significant differences were noted in the preoperative astigmatism among any of the four groups (F=1.08; df=3; P>.05). A significant difference was noted in age in the four preoperative groups.

CONCLUSIONS

Among the refractive population, African Americans were found to have thinner central corneal thickness than Caucasians. Asians were significantly (P<.05) more myopic compared to Caucasians, Hispanics, and African Americans. No difference was noted in the preoperative astigmatism among any of the four groups. Asians sought refractive surgery at a younger age whereas Caucasians sought it at an older age.

Retrospective evaluation of the influence of pupil size on visual acuity after KAMRA inlay implantation

PURPOSE

To investigate the influence of pupil size on visual acuity after KAMRA inlay (AcuFocus, Inc., Irvine, CA) implantation.

METHODS

Five hundred eighty-four presbyopic eyes of 584 patients who underwent LASIK were evaluated. Uncorrected near visual acuity (UNVA), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and corrected near visual acuity (CNVA) were measured. Two groups were classified: small pupil (pupil diameter < 6 mm) and large pupil (pupil diameter ≥ 6 mm) for both mesopic (pupil diameter < 4 mm) and photopic (pupil diameter ≥ 4 mm) pupil size parameters. The follow-up period was 6 months.

RESULTS

There were no significant differences in UNVA (P = .98) and CNVA (P = .16) between the mesopic pupil size groups; however, there were significant differences in UDVA (P = .023) and CDVA (P = .039). There was a weak correlation between pupil size and UDVA of the large mesopic pupil size group (rs = 0.129, P = .04). There were no significant differences in UNVA (P = .78), CNVA (P = .92), UDVA (P = .19), and CDVA (P = .60) for the photopic pupil size groups.

CONCLUSIONS

Pupil size does not have an influence on the resultant visual acuity after KAMRA inlay implantation. No correlation was found between preoperative and postoperative pupil size and visual acuity for the mesopic pupil groups.

Tear Neuromediator and Corneal Denervation Following SMILE

PURPOSE

To investigate the changes in tear neuromediators and corneal subbasal nerve plexus following small incision lenticule extraction (SMILE) and to study its association with different refractive power of corrections.

METHODS

Thirty patients were included for tear neuromediator analysis (40 eyes) and corneal nerve analysis using in vivo confocal microscopy scans (20 eyes). Tear samples were collected preoperatively and 1 week and 1, 3, 6, and 12 months postoperatively and analyzed for the substance P, calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF) concentrations using the enzyme-linked immunosor-bent assay (ELISA).

RESULTS

Corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), and corneal nerve branch density (CNBD) decreased significantly postoperatively, then gradually increased from 3 months onward, but did not recover to the baseline levels at 12 months. Tear substance P and CGRP levels remained stable over 12 months. Tear NGF levels demonstrated a small peak at 1 week before decreasing significantly compared to preoperative levels at 6 months (P = .03) and 12 months (P = .007). The 1-month reduction in CNFL, tear substance P, and CGRP concentrations were significantly correlated with the corrected spherical equivalent (SE) (r = 0.71 for CNFL; r = -0.33 to -0.52 at different time points for substance P and CGRP, respectively, all P < .05). Compared to the low to moderate myopia group, the high myopia group (corrected SE greater than -6.00 diopters) had a significantly greater decrease in CNFD, significantly higher tear substance P concentrations at 1 week, 1 month, and 6 months, and significantly higher tear CGRP concentrations at 1 and 6 months.

CONCLUSIONS

These results provide new insight into the neurobiological responses and their potential implications in corneal nerve damage and recovery after SMILE. High myopia treatment was associated with greater corneal denervation and neuroinflammation. [J Refract Surg. 2021;37(8):516-523.].

Corneal Epithelial Thickness Changes Following SMILE for Myopia With High Astigmatism

PURPOSE

To evaluate the corneal epithelial thickness (CET) profile changes after small incision lenticule extraction (SMILE) surgery for myopic astigmatism correction of greater than 2.00 diopters (D).

METHODS

This prospective observational study included 40 eyes (23 patients) treated with SMILE for myopia with cylinders of -2.25 to -4.50 D. Along with standard ophthalmic examinations, CET maps with a diameter of 9 mm were measured by high-resolution spectral-domain optical coherence tomography preoperatively and postoperatively. Correlations between the degree of residual astigmatism and the difference in CET values between preoperative flat and steep meridians were analyzed.

RESULTS

The CET showed significant changes in the central (2 mm), paracentral (2 to 5 mm), midperipheral (5 to 7 mm), and peripheral (7 to 9 mm) zones 6 months after SMILE (P < .001). Among the regions, the CET in the paracentral zones displayed the largest increase (9.75%) with the highest average thickness (57.29 µm). Moreover, symmetrical regional epithelial thickening at the preoperative astigmatism axis was observed in the midperipheral zones. The difference in CET between preoperative flat and steep meridians in the mid-peripheral zones continuously increased from postoperative 1 day to 6 months. This difference was positively correlated with the residual cylinder errors at 6 months postoperatively (r = -0.334, P = .035).

CONCLUSIONS

The 9-mm diameter CET in eyes with high astigmatism significantly increased 6 months after SMILE. Additionally, the difference in CET between preoperative flat and steep meridians in midperipheral zones may be related to astigmatic undercorrection in SMILE. [J Refract Surg. 2021;37(4):224-230.].

Corneal inlay implantation in a young pseudophakic patient

We describe the surgical correction of a 32-year-old pseudophakic patient with the Kamra corneal inlay. To our knowledge, this is the youngest patient to have such a procedure.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Comparison of Central Corneal Thickness Between Fourier-Domain OCT, Very High-Frequency Digital Ultrasound, and Scheimpflug Imaging Systems

PURPOSE

To compare corneal thickness measurements between three imaging systems.

METHODS

In this retrospective study of 81 virgin and 58 post-laser refractive surgery corneas, central and minimum corneal thickness were measured using optical coherence tomography (OCT), very high-frequency digital ultrasound (VHF digital ultrasound), and a Scheimpflug imaging system. Agreement between methods was analyzed using mean differences (bias) (OCT - VHF digital ultrasound, OCT - Scheimpflug, VHF digital ultrasound - Scheimpflug) and Bland-Altman analysis with 95% limits of agreement (LoA).

RESULTS

Virgin cornea mean central corneal thickness was 508.3 ± 33.2 µm (range: 434 to 588 µm) for OCT, 512.7 ± 32.2 µm (range: 440 to 587 µm) for VHF digital ultrasound, and 530.2 ± 32.6 µm (range: 463 to 612 µm) for Scheimpflug imaging. OCT and VHF digital ultrasound showed the closest agreement with a bias of -4.37 µm, 95% LoA ±12.6 µm. Least agreement was between OCT and Scheimpflug imaging with a bias of -21.9 µm, 95% LoA ±20.7 µm. Bias between VHF digital ultrasound and Scheimpflug imaging was -17.5 µm, 95% LoA ±19.0 µm. In post-laser refractive surgery corneas, mean central corneal thickness was 417.9 ± 47.1 µm (range: 342 to 557 µm) for OCT, 426.3 ± 47.1 µm (range: 363 to 563 µm) for VHF digital ultrasound, and 437.0 ± 48.5 µm (range: 359 to 571 µm) for Scheimpflug imaging. Closest agreement was between OCT and VHF digital ultrasound with a bias of -8.45 µm, 95% LoA ±13.2 µm. Least agreement was between OCT and Scheimpflug imaging with a bias of -19.2 µm, 95% LoA ±19.2 µm. Bias between VHF digital ultrasound and Scheimpflug imaging was -10.7 µm, 95% LoA ±20.0 µm. No relationship was observed between difference in central corneal thickness measurements and mean central corneal thickness. Results were similar for minimum corneal thickness.

CONCLUSIONS

Central and minimum corneal thickness was measured thinnest by OCT and thickest by Scheimpflug imaging in both groups. A clinically significant bias existed between Scheimpflug imaging and the other two modalities.

Influence of Cap Thickness on Corneal Curvature and Corneal Biomechanics After SMILE: A Prospective, Contralateral Eye Study

PURPOSE

To evaluate the impact of cap thickness for small incision lenticule extraction (SMILE) on changes in corneal curvature and biomechanics.

METHODS

One hundred eyes (50 patients) were enrolled in this prospective contralateral eye study. The difference in manifest refraction spherical equivalent (MRSE) in the same patient was less than 0.50 diopters. SMILE was performed with a randomized cap thickness of 110 µm in one eye and 140 µm in the other eye. MRSE, uncorrected distance visual acuity (UDVA), and corneal curvature and biomechanics were evaluated. The anterior and posterior surfaces of the corneal curvature (mean keratometry [Km] values 2, 4, and 6 mm from the pupil center) were measured by Pentacam HR (Oculus Optikgeräte, Wetzlar, Germany) and changes in corneal biomechanics at 6 months postoperatively by Scheimpflug technology.

RESULTS

There was no significant between-group difference in UDVA or MRSE postoperatively. Postoperative changes in Km at the anterior surface (ΔKm-ant) in the 4-mm zone were significantly higher in the 110-µm group than in the 140-µm group at 1 day and 1, 3, and 6 months postoperatively (P = .043, .045, .003, and .049, respectively); at 3 months, the ΔKm-ant in the 6-mm zone was higher in the 110-µm group (P = .035). The changes in second appla-nation time, deformation amplitude, and integrated radius were significantly less in the 110-µm group (P = .031, .049, and < .001, respectively).

CONCLUSIONS

A thicker corneal cap caused less change in anterior surface curvature after SMILE for moderate or low myopia, with no significant difference in UDVA and MRSE. [J Refract Surg. 2020;36(2):82-88.].

Combining refractive and topographic data in corneal refractive surgery for astigmatism: a new method based on polar value analysis and mathematical optimization

PURPOSE

To provide a theoretical approach for combining refractive and topographic data in the planning of corneal laser refractive surgery for astigmatism.

METHODS

Refractive and topographic data for astigmatism were transformed to the corneal plane. Net astigmatisms were converted to polar values. An optimization process was performed with the use of differential calculus.

RESULTS

With this method, the magnitude of the corneal astigmatism is reduced or unaltered, while its orientation is maintained. The method identifies the reduction in corneal astigmatism, which will yield the largest reduction in refractive astigmatic magnitude.

CONCLUSIONS

The advantage of the optimization method described in this article is a consistent reduction in corneal astigmatism towards sphericity. No new corneal astigmatism is carved on the cornea, and probably less tissue is ablated. The optimization method may also be used to combine refractive and topographic data for higher order aberrations with sinusoidal components. However, compared to the traditional purely refractive driven treatment, more refractive astigmatism will remain in the eye in most cases. A controlled clinical trial is necessary for comparing these two treatment modalities.

Effective corneal refractive diameter as a function of the object tangent angle in visual space

PURPOSE

To determine whether the currently accepted method of selecting a minimum optical zone diameter for laser refractive surgery that is equal to or slightly greater than the dark-adapted pupil diameter provides a sufficient diameter of corneal surface to focus light arising from objects in the paracentral and peripheral visual field.

SETTING

Department of Ophthalmology and Visual Sciences, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.

METHODS

An optical model of the anterior segment was developed to calculate the effective corneal refractive diameter (ECRD), which is the diameter of the area of cornea that refracts all incident light rays arising from an object through the physical pupil (PP). This model incorporates the patient variables of central anterior chamber depth (ACD), central corneal curvature (K(c)), and the diameter of the apparent entrance pupil (EP). The model was expanded to incorporate distant objects off the line of sight (LOS), described by their angular displacement from the fixation object in visual space (the object tangent angle delta(ob)). Results were calculated for the 360 meridian degree visual field (ie, for all objects in visual space perceptually displaced from the fixation object by angle delta(ob)). The effect of the prolate nature of the cornea was also investigated.

RESULTS

The ECRD expanded rapidly as a function of PP and delta(ob) but was minimally influenced by K(c). Beyond a critical object tangent angle delta(c), light rays striking the corneal vertex were not refracted through the PP, and the ECRD became an annular surface centered on the corneal vertex. The delta(c) was not a function of K, but increased as the PP increased and decreased as the ACD increased. The prolate nature of the cornea had little influence on the ECRD, even for very peripheral light rays.

CONCLUSIONS

The ECRD expands rapidly when considering distant objects only slightly displaced from the LOS. A patient treated with an optical zone equal to or slightly greater than the dark-adapted pupil diameter may experience vision quality loss for paracentral and midperipheral objects even under conditions of ambient indoor lighting.

Femtosecond Laser-Assisted Allogenic Lenticule Implantation for Corneal Ectasia After LASIK: A 3-Year In Vivo Confocal Microscopic Investigation

PURPOSE

To investigate morphological changes in the cornea and the implanted lenticule in patients with corneal ectasia after laser in situ keratomileusis (LASIK) and implantation using a lenticule from small incision lenticule extraction (SMILE).

METHODS

Eight eyes of 8 patients with ectasia after LASIK from 2015 to 2018 at the Eye and ENT Hospital of Fudan Unversity were analyzed. For recipient eyes, lenticules were transferred with a mean cryopreserved time of 20 ± 21 days extracted from SMILE donors to the exposed stromal bed after lifting the flaps and the flap was repositioned. Uncorrected and corrected distance visual acuity, manifest refraction, and corneal topography were performed. Patients were followed up for 3 years. Changes in lenticules and recipient corneas were analyzed using in vivo confocal microscopy.

RESULTS

Activated keratocytes in the anterior and posterior stroma were observed near the lenticule at the first 6 months. Elongated, deformed keratocyte nuclei were found in the implanted lenticules in postoperative year 1. The anterior and posterior interfaces showed an absence or decrease of keratocytes and the presence of small particles of varying brightness. Nerve fibers in the implanted lenticules were detected in one case. No obvious difference was detected between cryopreserved and fresh lenticules.

CONCLUSIONS

The preliminary findings suggest that recipient keratocytes repopulate the lenticules and the keratocytes in lenticules gradually return to their normal morphology. [J Refract Surg. 2020;36(11):714-722.].

Human graft cornea and laser incisions imaging with micrometer scale resolution full-field optical coherence tomography

Micrometer scale resolution full-field optical coherence tomography (FF-OCT) is developed for imaging human graft corneas. Three-dimensional (3-D) images with ultrahigh resolution (respectively, 1 and 1.5 μm in the axial and transverse directions), comparable to traditional histological sections, are obtained allowing the visualization of the cells and the precise structure of the different layers that compose the tissue. The sensitivity of our device enables imaging the entire thickness of the cornea, even in edematous corneas more than 800 μm thick. Furthermore, we provide tomographic 3-D images of laser incisions inside the tissue at various depths without slicing the studied corneas. The effects of laser ablations can be observed, along various optical sections, directly in the bulk of the sample with high accuracy, providing information on the interface quality and also imaging tiny changes of the tissue structure. FF-OCT appears to be a powerful tool for subcellular imaging of the corneal structure and pathologies on the entire thickness of the tissue as well as interface quality and changes in the collagen structure due to laser incisions on ex vivo human cornea.

Risk Evaluation of Human Corneal Stromal Lenticules From SMILE for Reuse

PURPOSE

To investigate the pathogenicity and immunogenicity of human corneal stromal lenticules from small incision lenticule extraction (SMILE).

METHODS

Serological testing was completed prior to sample collection to rule out infectious diseases. Pathogens herpes simplex viruses (HSV) type 1 and type 2 were screened for by real-time fluorescent quantitative polymerase chain reaction, and bacteria, fungi, and Acanthamoeba from 128 lenticules of 64 patients were cultured. A total of 132 lenticules from 93 patients were randomly assigned to the fresh group, -78 °C anhydrous glycerol preservation group (glycerol group), and 0.1% sodium dodecyl sulfate decellularization group (SDS group) in pairs and detected by immunohistochemistry, Western blot, transmission electron microscopy, transmittance, and nanoindentation.

RESULTS

The fresh lenticules were all negative for HSV-1, HSV-2, bacteria, fungi, and Acanthamoeba. HLA-I A/B/C and HLA-II DR antigens were all expressed in fresh lenticules but were clearly reduced after preservation at -78 °C in anhydrous glycerol or decellularization in 0.1% SDS. The collagen fibers of the lenticules in the fresh group were regularly arranged, and the keratocytes were intact. The fibers in the glycerol group were regularly arranged, and the integrity of keratocytes was destroyed. The fibers in the SDS group were disordered and had no cellular structure. The transmittance and Young's modulus were highest in the fresh group, lower in the glycerol group, and lowest in the SDS group.

CONCLUSIONS

Risk of infection is low, but risk of rejection exists on the reuse of fresh human corneal stromal lenticules from SMILE. Anhydrous glycerol preservation at -78 °C is an ideal method for reducing antigens without damaging the structure and function of lenticules. [J Refract Surg. 2021;37(1):32-40.].

Effect of cytochrome c peroxidase on corneal epithelial healing process after photorefractive keratectomy

PURPOSE

To evaluate the role of commercially prepared cytochrome c peroxidase eyedrops in corneal epithelial healing after photorefractive keratectomy (PRK).

SETTING

Department of Pathophysiological Optics, Faculty of Medicine, University of Bologna, Bologna, Italy.

METHODS

Seventy-two eyes of 36 patients affected by low to moderate refractive error (myopia and myopic astigmatism) had uneventful bilateral photorefractive keratectomy (PRK). In each patient, 1 eye (32 eyes) received standard postoperative therapy plus cytochrome c peroxidase eyedrops (3 times a day for 1 week or until corneal reepithelialization was completed, corresponding to 15 000). The fellow eye served as the control and received standard postoperative therapy plus placebo. Patients were monitored daily starting the day after surgery for 7 days to evaluate the corneal reepithelialization rate using a video slitlamp camera with a cobalt blue light. Mean diameter of corneal wounds was measured. Videotaped images were recorded and analyzed by computer planimetry.

RESULTS

All the eyes treated with cytochrome c peroxidase eyedrops healed completely before day 5 postsurgery, with a mean reepithelialization time of 91 hours +/- 14 (SD); the mean reepithelialization time was 154 +/- 9 in eyes receiving placebo (P<.05); the mean reepithelialization rate was 0.066 +/- 0.007 mm/hour in the cytochrome c peroxidase group and 0.039 +/- 0.006 mm/hour in the control group (P<.05). There were no statistically significant differences between groups in corneal haze presentation during follow-up (P =.70), perhaps because the time period was too brief (7 days). However, corneal clarity, on slitlamp biomicroscopy in the study group was greater than in the control group. No side effects or toxic effects were documented.

CONCLUSIONS

These data suggest that cytochrome c peroxidase significantly accelerates epithelial healing after PRK. Further clinical study should be performed to prove the results obtained in this pilot study and the long-term efficacy of cytochrome c peroxidase to prevent corneal haze.

Custom selection of aspheric intraocular lens in eyes with previous hyperopic corneal surgery

PURPOSE

To determine the optimum amount of spherical aberration in intra-ocular lenses (IOLs) to maximize optical quality in eyes with previous hyperopic corneal surgery.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

DESIGN

Theoretical simulation study.

METHODS

The amount of spherical aberration in the IOL was varied to produce residual ocular spherical aberration ranging from -0.50 to +0.50 μm. With the use of the Zernike Tool Program, the polychromatic point-spread function with Stiles-Crawford effect was calculated for 6.0 mm and 4.0 mm pupils and defocus of 0.00 diopter (D), -0.50 D, and +0.50 D. The IOL spherical aberration at which maximum image quality was achieved was determined. Stepwise multiple regression analysis was performed to assess the predictors of optimum IOL spherical aberration.

RESULTS

Aspheric IOL implantation was simulated in 106 eyes of 80 patients; ages ranged from 40 to 59 years. With 0.00 D, -0.50 D, and +0.50 D defocus, respectively, the ranges of 25th to 75th percentiles of the optimum IOL spherical aberration were -0.12 to +0.20 μm, +0.10 to +0.42 μm, and -0.35 to -0.03 μm for the 6.0 mm pupil and -0.14 to +0.26 μm, +0.41 to +0.86 μm, and -0.74 to -0.24 μm for the 4.0 mm pupil. The amount of optimum IOL spherical aberration could be predicted on the basis of other higher-order aberrations (HOAs) of the cornea with multiple correlation coefficients up to 0.98.

CONCLUSIONS

The amount of IOL spherical aberration producing the best image quality in eyes with previous hyperopic corneal surgery varied widely and could be predicted on the basis of the full spectrum of corneal HOAs.

FINANCIAL DISCLOSURE

Supported in part by an unrestricted grant from Research to Prevent Blindness, New York, New York. No author has a financial or proprietary interest in any material or method mentioned.

Fulfilling the Promise of Laser Refractive Surgery

PURPOSE

To review the characteristics required to perform accurate and precise laser refractive surgery relative to the current state of the art and the technology improvements needed in the future.

METHODS

The general characteristics for laser refractive surgery are identified and their relative contributions to a successful result considered. For each characteristic, the degree to which improvements in technology are likely to improve results is discussed.

RESULTS

The environment (surgeon, site), technology (laser, aberrometer), and patient are identified as key factors affecting results. Although aberrometers appear to be clinically sufficient, improvements in laser beam characteristics and delivery should improve system consistency. Current registration technology may be a factor in variability from patient to patient, but the greatest contribution in this regard would appear to be patient biomechanical and healing response factors.

CONCLUSIONS

Wavefront-guided laser refractive surgery has demonstrated an ability to be better than conventional surgery. Improvements in laser technology, registration technology, and biomechanical diagnostics are expected to further improve results. These potential improvements are expected to reduce variability and suggest that the final potential of this technology has not yet been realized.

Comparison of Clinical Outcomes and Visual Quality Using a Medium Versus Small Contact Glass in Patients Undergoing SMILE With Large Corneal Diameters

PURPOSE

To compare the clinical outcomes and visual quality using a small (S) versus medium (M) size contact glass in eyes with large white-to-white (WTW) distance undergoing bilateral small incision lenticule extraction (SMILE) for myopia correction.

METHODS

This contralateral eye study involved 60 eyes of 30 patients (mean age: 27.20 years) undergoing bilateral SMILE for myopia/myopic astigmatism with a WTW distance of 12 mm or greater in both eyes, which were randomized to receive treatment with an S-contact glass in one eye and an M-contact glass in the fellow eye. Opaque bubble layer (OBL) was graded using a new grading system. On postoperative 1 day, 2 weeks, and 3 months, UDVA, CDVA, contrast sensitivity, Objective Scatter Index, and modulation transfer function cut-off values were compared between the two groups.

RESULTS

The mean OBL score was significantly lower in the S-contact glass group (28.18%) compared to the M-contact glass group (67.13%) (P < .01). At 1 day postoperatively, the UDVA, Objective Scatter Index score, and contrast sensitivity values for all spatial frequencies were significantly better in eyes treated with the S-contact glass compared to the M-contact glass (P ⩽ .05). At 3 months postoperatively, however, the UDVA, Objective Scatter Index score, modulation transfer function cut-off, and contrast sensitivity values were comparable for both groups. No eye in either group had intraoperative complications such as suction loss, incision/lenticule tears, or lenticule retention.

CONCLUSIONS

In corneas with a WTW distance of 12 mm or greater, docking with the S-contact glass resulted in significantly better immediate visual results due to less OBL formation and smoother tissue dissection compared to the M-contact glass. [J Refract Surg. 2021;37(3):150-157.].

Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

PURPOSE

To investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.

METHODS

This study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.

RESULTS

One month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).

CONCLUSIONS

One month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

CIRCLE Software for Management of Epithelial Ingrowth After SMILE

PURPOSE

To report a novel therapeutic use of CIRCLE software (Carl Zeiss Meditec) to manage visually significant epithelial ingrowth following small incision lenticule extraction surgery (SMILE).

METHODS

Case series.

RESULTS

In this case series, the authors describe three eyes with progressive and visually significant epithelial ingrowth following an uneventful SMILE procedure. The management of epithelial ingrowth following SMILE is challenging, given the small access incision to the interface and the risk of incomplete removal. All cases were successfully managed by converting the SMILE cap into a flap using the CIRCLE software, which provided the necessary access to the original SMILE interface. Once the flap was lifted, the epithelial in-growth was completely debrided from the underlying stroma and undersurface of the flap, followed by a thorough interface wash. Postoperative recovery was uneventful, with no recurrence noted in any of the eyes.

CONCLUSIONS

Use of CIRCLE software provides a novel and unique approach to successfully treating vision-threatening epithelial ingrowth after SMILE. [J Refract Surg. 2021;37(11):776-780.].