Wound Healing, Inflammation, and Corneal Ultrastructure After SMILE and Femtosecond Laser-Assisted LASIK: A Human Ex Vivo Study

PURPOSE

To assess the wound healing, inflammation, and tissue ultrastructure in the human corneal stroma after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK).

METHODS

Sixteen corneoscleral discs of 16 human donors unsuitable for corneal transplantation were obtained from an eye bank. Eight eyes underwent SMILE with -5.00 diopters (D) of myopic correction; in 3 of them the lenticule was not extracted. Further 5 donor corneas were subjected to FS-LASIK with -5.00 D ablation, and 3 eyes served as the control group without surgical intervention. Postoperatively, specimens were incubated in organ culture medium for 72 hours before being subjected to immunofluorescence staining for CD11b, Ki67, fibronectin, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay, and high-magnification scanning electron microscopy.

RESULTS

Keratocyte apoptosis, keratocyte proliferation, and infiltration of immune cells were generally mild and comparable between FS-LASIK and SMILE (irrespective of surgical lenticule extraction). By staining for fibronectin, we observed a trend toward milder fibrotic response in the corneal stroma after SMILE than after FS-LASIK. On the contrary, scanning electron microscopy analysis revealed a smoother, more regular ultrastructural appearance of the residual corneal bed after FS-LASIK.

CONCLUSIONS

Corneal stromal wound healing after SMILE and FS-LASIK was virtually identical with respect to keratocyte proliferation and apoptosis in the human donor eye model. Although reactive fibrosis adjacent to the laser application site appeared less marked after SMILE, the stromal bed after LASIK exhibited a smoother surface texture. [J Refract Surg. 2018;34(6):393-399.].

Biological Lenticule Implantation for Correction of Hyperopia: An Ex Vivo Study in Human Corneas

PURPOSE

To evaluate changes in corneal tomography after stromal lenticule implantation ex vivo, with respect to the dependency of the lenticule thickness and implantation depth on the corneal curvature and the postoperative biomechanical strength at increased chamber pressure.

METHODS

Twenty-eight human donor corneas underwent pocket implantation of refractive stromal lenticules. Four groups were created by the combination of two implantation depths (110 and 160 µm) and two lenticule thicknesses (95 µm = 4.00 diopters [D], 150 µm = 8.00 D). Sagittal keratometry and total corneal refractive power (TCRP_{4mm,apex,zone}) were obtained for the front and back curvature with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) at chamber pressures of 15 and 40 mm Hg.

RESULTS

The anterior curvature steepening was comparable between the 4.00 D and 8.00 D groups (P > .141), but more pronounced with 110 µm implantation depth (P < .038). The posterior curvature flattened significantly more after implantation of 8.00 D than 4.00 D lenticules (P < .002), but was similar at 110 and 160 µm implantation depths (P > .071). Average ΔTCRP for the 4.00 D and 8.00 D groups was 3.10 ± 0.60 and 5.30 ± 1.66 diopters (D) at 110-µm depth, respectively (P = .003), but 1.99 ± 0.79 and 3.36 ± 1.45 D at 160-µm depth, respectively (P = .066). The relative correction achieved was 66% to 78% at 110-µm depth and 42% to 50% at 160-µm depth, but similar when using 4.00 D and 8.00 D lenticules. Increased chamber pressure caused significant anterior and posterior curvature steepening after implantation in all four groups (P < .001), but not before implantation (P > .632).

CONCLUSIONS

The power of the implanted lenticule must be higher than the intended correction, and customized to the chosen implantation depth. Biomechanical strength seems to decrease after lenticule implantation. [J Refract Surg. 2018;34(4):245-252.].

Intraoperative Patient Experience and Postoperative Visual Quality After SMILE and LASIK in a Randomized, Paired-Eye, Controlled Study

PURPOSE

To compare intraoperative and postoperative subjective patient experience after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK.

METHODS

In a prospective, randomized, paired-eye, single-masked clinical trial at Singapore National Eye Centre, 70 patients were randomly treated with SMILE and LASIK in each eye. The intraoperative questionnaire was completed immediately after surgery and included light perception and levels of anxiety, fear, and discomfort. The postoperative 1- and 3-month questionnaires evaluated severity of light sensitivity, eye discomfort, eye dryness, excessive tearing, gritty sensation, glare, halos, blurring, and fluctuations in vision.

RESULTS

Average discomfort scores were higher during tissue manipulation in SMILE (1.9 ± 0.9) than flap lifting in LASIK (1.59 ± 0.8) (P = .020) but comparable during docking and laser application (P > .249). Fear scores were lower in SMILE than LASIK during docking (2.6 ± 1.6 vs 3.4 ± 1.9, P = .024) but similar during occasional blackout, laser application, and lenticule/flap manipulation (P > .364). Fear scores were generally higher in patients with intraoperative suction loss (n = 3). For SMILE, light sensitivity, eye discomfort, blurring, and fluctuations in vision improved from 1 to 3 months (P < .039). For LASIK, improvements were reported for light sensitivity, eye discomfort, eye dryness, gritty sensation, and fluctuations in vision from 1 to 3 months (P < .046). At 1 month, patients experienced more blurring after SMILE than LASIK (2.1 ± 0.8 vs 1.8 ± 0.7, P = .025), but with no differences in any of the visual symptoms at 3 months.

CONCLUSIONS

Tissue manipulation may be more uncomfortable during SMILE than LASIK, but not more frightening. Subjective visual symptoms were comparable after 3 months. [J Refract Surg. 2018;34(2):92-99.].

Visual outcomes and management after corneal refractive surgery: A review

Corneal refractive surgery procedures are widely performed to permanently correct refractive errors. Overall, refractive surgeries are safe, predictable and present high rates of satisfaction. Nevertheless, the induced epithelial, stromal and nerve damage alters corneal integrity and function, triggering a regenerative response. Complications that arise from corneal wound healing process might directly impact on visual outcomes of keratorefractive procedures. Most of these complications can be prevented or effectively treated with minimal consequences and minor impact on optical quality. Nevertheless, it is crucial to accurately and timely identify these corneal regeneration-related complications for successful counseling and management. Optometrists, as primary eye care providers, play an essential role in detecting anatomic and functional alterations in vision. It is therefore of great interest for optometrists to be familiar with the principal postoperative complications derived from alterations in regenerative process after corneal laser refractive surgeries. This review aims to provide a basis for optometrists to better understand, identify and manage the main wound healing-related complications after refractive surgery.

[Problems and challenges in the development of corneal refractive surgery]

Corneal refractive surgery, as one of the common visual correction methods, has been increasingly accepted in China. There are a large number of people in China who undergo the corneal refractive surgery due to the high incidence of myopia in the country. It is essential that the safest and most effective surgery should be used to correct refractive errors in the cases involved with relatively normal eyes and corneas. In recent years, corneal refractive surgery has been rapidly developing with new technologies and techniques emerging all the time, such as SMILE (small incision lenticule extraction) surgery, which has been extensively applied in China since five years ago when it was approved by FDA. However, little known are these new technologies and techniques, and the clinical and basic researches need further investigations by various approaches including histopathology and molecular biology, combined with mathematics, computer science, physics, chemistry and corneal biomechanics. To achieve minimal tissue damage and optimal clinical outcomes on visual quality by corneal refractive surgery requires the multidisciplinary partnerships of medical practitioners and researchers. (Chin J Ophthalmol, 2018, 54: 3-6).

Unusual Internal Astigmatism Due to Severe Capsule Contraction Syndrome

PURPOSE

To describe a case of severe capsule contraction syndrome causing significant astigmatism due to intraocular lens (IOL) folding.

METHODS

Case report.

RESULTS

Capsule fibrosis and contraction resulted in bending of the hydrophilic IOL along its long axis. Anterior Nd:YAG capsulotomy resolved the situation and restored the patient's visual acuity.

CONCLUSIONS

Hydrophilic IOLs are more susceptible to capsule contraction due to the increased flexibility of highly hydrated materials. They should be avoided in patients at risk of capsule contraction to prevent ocular complications. [J Refract Surg. 2018;34(1):65-67.].

Tomographic Analysis of Anterior and Posterior and Total Corneal Refractive Power Changes After Femtosecond Laser-Assisted Keratotomy

PURPOSE

To analyze the effect of penetrating femtosecond laser-assisted keratotomy (pFLAK) during laser lens surgery on anterior and posterior corneal astigmatism and total corneal refractive power (TCRP) astigmatism (CA_ant, CA_post, CA_TCRP) measured with Scheimpflug tomography.

DESIGN

Prospective, interventional case series.

METHODS

This institutional study included 27 eyes of 23 patients (aged 65 ± 8 years) with low-to-moderate CA_TCRP determined with Scheimpflug tomography (Pentacam HR; Oculus, Wetzlar, Germany) after penetrating femtosecond laser-assisted keratotomy (pFLAK) and laser lens surgery. The CA_ant, CA_post, and CA_TCRP were determined before and 1 and 3 months after surgery. Vector analysis according to the Alpins method was used to calculate surgically induced astigmatism (SIA).

RESULTS

The mean preoperative CA_ant (0.97 ± 0.30 diopter [D]) was significantly reduced to 0.63 ± 0.34 D (P < .001). SIA_ant was 0.71 ± 0.37 D. The CA_post showed no significant change, from preoperative 0.26 ± 0.12 D to 0.26 ± 0.10 D postoperatively (P = .625). In line with this finding, SIA_post was low (0.12 ± 0.07 D). The CA_TCRP showed similar results as CA_ant.

CONCLUSION

pFLAKs planned according to Scheimpflug-based CA_TCRP result in a significant reduction of the CA_ant and CA_TCRP, but do not affect the posterior corneal curvature significantly, as measured by Scheimpflug tomography. Further research is required to develop a new valid nomogram for laser-assisted lens surgery.

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.

SMILE Procedures With Four Different Cap Thicknesses for the Correction of Myopia and Myopic Astigmatism

PURPOSE

To study the feasibility of performing myopic femtosecond small incision lenticule extraction (SMILE) with four different cap thicknesses (130, 140, 150, and 160 μm).

METHODS

In this retrospective, comparative, non-randomized clinical trial, a refractive lenticule of intrastromal corneal tissue was cut with the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) using different depths of the non-refractive lenticule cut. Manifest refraction, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and Objective Scattering Index (OSI) were evaluated. Minimum follow-up time was 1 year.

RESULTS

Ninety-four eyes of 47 patients with myopia with (14 patients) and without (33 patients) astigmatism were treated. One year after the surgery, mean log-MAR UDVA, logMAR CDVA, SE, and OSI were 0.07 ± 0.12, 0.01 ± 0.37, 0.07 ± 0.57, and 0.88 ± 0.17, respectively (P < .05). There were no significant statistical differences in logMAR UDVA, logMAR CDVA, SE, or OSI (P > .05) variables when the different groups were compared for the same periods of time.

CONCLUSIONS

No differences in visual acuity, refractive outcomes in optical visual quality, or complications were observed when using SMILE at four different depths.

Comparison of Early Changes in Ocular Surface and Inflammatory Mediators between Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction

Purpose

To evaluate the short-term changes in ocular surface measures and tear inflammatory mediators after femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) procedures.

Methods

Eighteen subjects (18 eyes) underwent FLEx and 23 subjects (23 eyes) underwent SMILE in this single-center and prospective study. Central corneal sensitivity, Schirmer I test (SIT), noninvasive tear breakup time (NI-TBUT), tear meniscus height, corneal fluorescein (FL) staining, and ocular surface disease index (OSDI) were assessed in all patients. Concentrations of interleukin-1α (IL-1α), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) in collected tears were measured by multiplex antibody microarray.

Results

Central corneal sensitivity was reduced in both groups, but the scores in the SMILE group were higher than those in the FLEx group at all time points postoperatively (P<0.01). Lower FL scores and longer NI-BUT were observed in the SMILE group 1 week after surgery (P<0.05). OSDI scores in both groups increased rapidly at 1 day and 1 week postoperatively, then returned to their preoperative levels within 1 month (P<0.05). There were no significant differences in SIT or tear meniscus height between the two groups. Lower and faster recovery of tear NGF, TGF-β1 and IL-1α concentration were found in the SMILE group compared to the FLEx group postoperatively. No significant difference was found in tear TNF-α, IFN-γ and MMP-9 for either group before or after surgery. Tear NGF, TGF-β1 and IL-1α show a correlation with ocular surface changes after FLEx or SMILE surgery.

Conclusion

SMILE has superiority over FLEx in early ocular surface changes and NGF, TGF-β1 and IL-1α may contribute to the process of ocular surface recovery.

Trial Registration

ClinicalTrials.gov NCT02540785

Treatment of Presbyopia in Emmetropes Using a Shape-Changing Corneal Inlay: One-Year Clinical Outcomes

PURPOSE

To report 1-year safety and efficacy clinical outcomes of a shape-changing corneal inlay for the treatment of presbyopia.

DESIGN

Prospective, nonrandomized, multicenter United States Food and Drug Administration Investigational Device Exemption clinical trial (clinicaltrials.gov identifier, NCT01373580).

PARTICIPANTS

Nondominant eyes (N = 373) of emmetropic presbyopic subjects were implanted at 11 sites with the Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, CA); 340 eyes underwent the 1-year follow-up visit.

METHODS

The corneal inlay was implanted under a corneal flap at the center of the light-constricted pupil created with a femtosecond laser.

MAIN OUTCOME MEASURES

For subjects completing the 1-year follow-up, monocular and binocular uncorrected and corrected visual acuity, refractive stability, contrast sensitivity (CS; photopic and mesopic), symptom and satisfaction questionnaire results, and adverse events.

RESULTS

At 1 year in the treated eye, on average, uncorrected near visual acuity (UNVA) improved by 5.1 lines, uncorrected intermediate visual acuity (UIVA) improved by 2.5 lines, and uncorrected distance visual acuity (UDVA) decreased by 1.2 lines. From 3 months through 1 year, 93% of subjects achieved UNVA of 20/25 or better, 97% achieve UIVA of 20/32 or better, and 95% achieved UDVA of 20/40 or better. Binocularly, the mean UDVA exceeded 20/20 from 3 months through 1 year. Contrast sensitivity loss occurred only at the highest spatial frequencies, with no loss binocularly. Absent or mild scores were reported in 96% of subjects for visual symptoms (glare, halos, double vision, and fluctuations in vision), in 99% for ocular symptoms (pain, light sensitivity, and discomfort), and in 95% for dryness. Adverse events were treatable and resolved. Eighteen inlays were replaced, usually soon after implantation because of decentration, but UNVA was little affected in this group thereafter. In the 11 cases requiring inlay explantations, 100% achieved a corrected distance visual acuity of 20/25 or better by 3 months after explant.

CONCLUSIONS

The Raindrop Near Vision Inlay provides significant improvement in near and intermediate visual performance, with no significant change in binocular distance vision or CS. Subject satisfaction is improved significantly with minimal ocular or visual symptoms.

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.

[Treatment of large corneal perforations with acellular multilayer of corneal stromal lenticules harvested from femtosecond laser lenticule extraction]

OBJECTIVE

To describe a novel surgical technique for the treatment of large corneal perforations by using acellular multilayer of corneal stromal lenticules.

METHODS

Prospective study. The acellular tissue used for the repair was harvested from myopic patients during the femtosecond laser (FS) refractive surgery. Informed consent, blood test and donor eligibility were obtained in each case. Three or four layers of lenticules were stacked up and stored at -80°C in pure sterile glycerin. The diameter is 6.0 to 6.5 mm and central thickness was 300 to 400 µm. If the diameter of the corneal ulcer perforation was larger than 3 mm and corneal grafts were not available, we used this kind of patches to seal the perforations. It was a retrospective case series study. Five cases of corneal ulcer perforation were enrolled in this study. One was neuropathic keratitis, one was atopic keratoconjunctivitis, and the other three were fungal keratitis. Acellular multilayer of stromal lenticules were used in these cases for emergent therapy.

RESULTS

The sealing of the perforation and the re-establishment of the anterior chamber were achieved successfully in all the cases. For the pericentral perforations, visual recovery was achieved. And efficient palliative management was done for the central perforations.

CONCLUSIONS

The reported technique seems to represent a good alternative emergency procedure for the management of large corneal perforations. It is a very useful method for Chinese hospitals where the shortage of cornea donors is a very serious problem and the amount of FS surgeries are increasing.

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.

Relationship between corneal thickness, corneal curvature, and intraocular pressure before and after laser treatment for simple myopia

PURPOSE

To determine the relationship of central corneal thickness (CCT), curvature (CC), and intraocular pressure (IOP) as determinative factors for corneal biomechanics and in refractive surgery.

METHODS

The study investigated 48 eyes from subjects who visited the Excimer Laser Surgery Clinic at the Department of Ophthalmology. The refractive error, IOP, CCT, and CC were measured in all participants. After 3 months, all examinations were repeated.

RESULTS

Linear regression demonstrated a significant positive relationship between pre- and postoperative CCT, CC, and IOP values. The IOP showed a significant correlation with CCT (P = 0.033) for pre-PRK, but no significant relationship was seen post-PRK. The CCT also correlated significantly with CC both pre- and post-PRK (P < 0.05).

CONCLUSION

The IOP was significantly correlated with CCT before PRK, but its behavior differed after surgery. Nearly the same correlation was seen between CCT and CC before and after the PRK; nevertheless, IOP measurements should be calculated or estimated more precisely after PRK based on CCT corrections.

Optical coherence tomography-based corneal power measurement and intraocular lens power calculation following laser vision correction (an American Ophthalmological Society thesis)

PURPOSE

To use optical coherence tomography (OCT) to measure corneal power and improve the selection of intraocular lens (IOL) power in cataract surgeries after laser vision correction.

METHODS

Patients with previous myopic laser vision corrections were enrolled in this prospective study from two eye centers. Corneal thickness and power were measured by Fourier-domain OCT. Axial length, anterior chamber depth, and automated keratometry were measured by a partial coherence interferometer. An OCT-based IOL formula was developed. The mean absolute error of the OCT-based formula in predicting postoperative refraction was compared to two regression-based IOL formulae for eyes with previous laser vision correction.

RESULTS

Forty-six eyes of 46 patients all had uncomplicated cataract surgery with monofocal IOL implantation. The mean arithmetic prediction error of postoperative refraction was 0.05 ± 0.65 diopter (D) for the OCT formula, 0.14 ± 0.83 D for the Haigis-L formula, and 0.24 ± 0.82 D for the no-history Shammas-PL formula. The mean absolute error was 0.50 D for OCT compared to a mean absolute error of 0.67 D for Haigis-L and 0.67 D for Shammas-PL. The adjusted mean absolute error (average prediction error removed) was 0.49 D for OCT, 0.65 D for Haigis-L (P=.031), and 0.62 D for Shammas-PL (P=.044). For OCT, 61% of the eyes were within 0.5 D of prediction error, whereas 46% were within 0.5 D for both Haigis-L and Shammas-PL (P=.034).

CONCLUSIONS

The predictive accuracy of OCT-based IOL power calculation was better than Haigis-L and Shammas-PL formulas in eyes after laser vision correction.

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.

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.

[Advances in biomechanical effects of laser corneal refractive surgery]

Corneal biomechanical properties will change after laser refractive surgery, which can be evaluated by several biomechanical parameters. The biomechanical stress will decrease remarkably after LASIK, but thin flap is helpful to maintain its stress. Excimer laser surface ablation has biomechanical advantages over LASIK procedure. The femtosecond laser technology can achieve smooth and regular incision and make the angle design. Flap adhesion is stronger when completed by a femtosecond laser. Laser refractive surgery will become safer and achieve more stable outcomes with the emphasis on biomechanical effects.

Effect of TGFβ and PDGF-B blockade on corneal myofibroblast development in mice

The purpose of this study was to investigate the role of transforming growth factor beta (TGFβ) and/or platelet-derived growth factor-B (PDGF-B) blockade on the differentiation of vimentin and alpha-smooth muscle actin (αSMA)-expressing myofibroblasts associated with haze in mice. Mouse corneas had haze-generating irregular PTK (phototherapeutic keratectomy) and topical treatment with the vectors. Six study groups of PTK treated corneas, with four corneas per group in each experiment, were Group 1) treated with TGFβ-KDEL vector interfering with TGFβ signaling through anomalous sorting of cytokine bound to the expressed altered receptor; Group 2) treated with PDGF-B-KDEL vector interfering with PDGF signaling through anomalous sorting of cytokine bound to the expressed altered receptor; Group 3) treated with both TGFβ-KDEL vector and PDGF-B-KDEL vector to interfere with signaling of both cytokines; Group 4) empty pGFPC1 vector; Group 5) empty pCMV vector; and Group 6) no vector treatment control. At one month after surgery, the corneas were analyzed by immunocytochemistry (IHC) for central stromal cells expressing myofibroblast markers vimentin and αSMA. The stroma of corneas treated with the TGFβ-KDEL vector alone (p < 0.05) or both the TGFβ-KDEL and PDGF-B-KDEL vectors (P < 0.05) had significantly lower density of vimentin-positive cells compared to the corresponding control group. The central stroma of corneas treated with the TGFβ-KDEL vector (p < 0.05) or the PDGF-B-KDEL vector (p < 0.05) had lower density of αSMA-positive cells compared to the corresponding control group. The density of αSMA-positive stromal cells was also significantly lower (p < 0.05) when both the TGFβ-KDEL and PDGF-B-KDEL and vectors were applied together compared to the corresponding control groups. This study provides in situ evidence that TGFβ and PDGF-B have important roles in modulating myofibroblast generation in the mouse cornea after haze-associated injury.

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.