Laser in situ keratomileusis in 2010 - a review

Clinical Applications of Anterior Segment Optical Coherence Tomography: An Updated Review

Since its introduction, optical coherence tomography (OCT) has revolutionized the field of ophthalmology and has now become an indispensable, noninvasive tool in daily practice. Most ophthalmologists are familiar with its use in the assessment and monitoring of retinal and optic nerve diseases. However, it also has important applications in the assessment of anterior segment structures, including the cornea, conjunctiva, sclera, anterior chamber, and iris, and has the potential to transform the clinical examination of these structures. In this review, we aim to provide a comprehensive overview of the potential clinical utility of anterior segment OCT (AS-OCT) for a wide range of anterior segment pathologies, such as conjunctival neoplasia, pterygium, scleritis, keratoconus, corneal dystrophies, and infectious/noninfectious keratitis. In addition, the clinical applications of AS-OCT (including epithelial mapping) in preoperative planning and postoperative monitoring for corneal and refractive surgeries are discussed.

Impact of Topical Cyclosporine-A or Topical Chloroquine on Post-LASIK Ocular Surface Stability - A Randomized Controlled Trial

PURPOSE

To compare effect of topical cyclosporine-A 0.05% (CsA) and chloroquine phosphate 0.03% (CHQ) as an adjunct to standard therapy in maintaining post-laser assisted in situ keratomileusis (LASIK) ocular surface stability.

METHODS

Randomized controlled trial on 100 eyes undergoing femtosecond-LASIK randomized into three groups: 33 eyes in Group I (Standard Treatment group), 34 eyes in Group II (CsA group) and 33 eyes in Group III (CHQ group). Standard treatment included topical moxifloxacin, topical prednisolone and carboxymethyl cellulose. Group II received topical CsA 0.05% twice daily for three months and group III received topical CHQ 0.03% twice daily for three months in addition to standard treatment. Primary outcome measure was change in ocular surface disease index (OSDI) at 6 months. Secondary outcome measures were tear break up time (TBUT), Schirmer-I score, tear film osmolarity, tear film MMP-9 and visual acuity. Follow-up was performed at postoperative 1, 3 and 6 months.

RESULTS

At 6 months, OSDI score, MMP-9, tear osmolarity, TBUT and Schirmer score were significantly better in both CsA and CHQ groups as compared with controls (p < 0.001). OSDI, Tear osmolarity, TBUT, MMP-9 levels were comparable in CsA and CHQ group (p > 0.05). In CsA group, tear film MMP-9 levels at 6 months were comparable to preoperative baseline (p = 0.09). There was no significant change in the Schirmer score from baseline in the CsA group; in addition, the Schirmer score was significantly better than the CHQ group at 6 months (p = 0.02). Visual acuity was comparable in all three groups. Adverse effects including burning sensation, stinging, pain and redness were reported by ten patients (CsA group- 3, CHQ group-7; p = 0.28).

CONCLUSION

Both CsA and CHQ are useful adjuncts to standard therapy in maintaining ocular surface stability after refractive surgery. Cyclosporine A has more potent and sustained anti-inflammatory effect with less ocular irritative effects.

Patients’ Awareness of the Ocular Side Effects of Isotretinoin Therapy: A Study From Saudi Arabia

Introduction

Isotretinoin is one of the most commonly prescribed drugs among dermatologists because it's used in the treatment of Acne vulgaris. Despite having an adequate safety profile, isotretinoin-related adverse events are common, with ocular manifestations being one of them. Although being generally mild, ophthalmologic manifestations associated with isotretinoin may cause significant ocular morbidity.

Objectives

The objective is to evaluate the awareness of the ocular side effects of isotretinoin treatment in patients with acne and to understand the treating physicians' practice of prescribing isotretinoin from the patient's point of view.

Method

A descriptive cross-sectional study was conducted on a Saudi Arabian population from June to September 2021. We used a self-administered questionnaire to collect data on drug dose, treatment duration, ocular adverse effects, patients' awareness, and patients' perception of treating physicians' practice.

Results

Of 1,157 responders, 452 (39.1%) consisted of participants who met the inclusion criteria, therefore they were enrolled in the study. Out of our responders, 308 (68.1%) were women. Approximately, 91.6% of participants had a dermatologist's prescription for isotretinoin. Eye dryness was the most commonly reported ocular adverse effect (83.4%). Blepharitis and conjunctivitis were the most commonly diagnosed complications after starting isotretinoin (5.4% for each).

Approximately, 71.2% participants were not advised to see an ophthalmologist for ophthalmological screening. Physicians asked only 78 (17.3%) respondents about a recent refractive surgery before starting isotretinoin or if they intended to undergo a refractive surgery in the next six months. Approximately, 57.5% participants were unaware of possible contact lens intolerance. Lubricant eye drops were prescribed to 305 (67.5%) respondents during isotretinoin treatment. Approximately, 36.7% participants were advised to consult their treating physicians if they had any serious ocular signs or symptoms.

Approximately, 67.9% participants reported their awareness of the ocular side effects of isotretinoin therapy. However, 236 (52.2%) participants responded that they were not provided with sufficient information on the ocular side effects of isotretinoin therapy.

Laser in situ keratomileusis (LASİK) in patients with superior steepening on corneal topography: Is it safe and predictable?

BACKGROUND

Attention is usually given to inferior steepening on corneal topography in the evaluation of a patient's suitability for LASIK surgery. The aim of this study is to investigate long-term refractive results with superior steepening.

METHODS

Patients who underwent LASIK surgery between 2015 and 2019 in our refractive surgery department were retrospectively reviewed. The patients with a ≥ 1.0 D superior-inferior (S-I) quadrant difference in the tangential map, using a Scheimpflug camera with a Placido disc topographer (Sirius), were included in the study. Preoperative and postoperative best-corrected and uncorrected visual acuity (Snellen), cylindrical refraction values, and spherical equivalent (SE) values were compared. Adverse events were recorded.

RESULTS

Fifty eyes of 28 patients participated in the study. The mean age of the patients was 27.5 ± 8.0 (19-59). Sixteen patients were female (57.1%), and 12 (42.8%) patients were male. The average follow-up time was 29.8 ± 11.1 months (12-61). Average central corneal thickness was 549.4 ± 26.0 (498-602) μm. Average minimal corneal thickness was 549.1 ± 26.9 (497-598) μm. Preoperative S-I quadrant difference (D) was 1.87 ± 0.7 (1.0-3.99). Posterior elevation (Kvb) was 11.2 ± 1.9 (9-17) μm. The preoperative SE value was - 1.7 ± 2.1 (- 6.25-3.25) and improved to - 0.3 ± 0.44 D (- 1.25-0.75) (p < 0.001). Preoperative cylindrical refraction values were - 2.04 ± 1.7 (- 6.25-0), and postoperative values were - 0.47 ± 0.4 (- 2-0) D (p < 0.001). Uncorrected visual acuity was median 1.0 (0.4-1.0) with 38 eyes (76%) having 20/20 postoperative uncorrected visual acuity. No sight threatening complications or ectasia findings were observed during the 2 years postoperative follow-up time.

CONCLUSIONS

Abnormal corneal topographies with (S-I) asymmetry result in predictable results after LASIK.

Incidence, Indications, and Outcomes of Eyes Needing Early Flap Lifting After LASIK

PURPOSE

To analyze the incidence, indications, and outcomes associated with early flap relifting after uncomplicated laser in situ keratomileusis (LASIK).

METHODS

All LASIK cases from a single surgical center between 2007 and 2015 were reviewed. Early postoperative flap lift cases (<15 d after surgery) were identified.

RESULTS

Overall, 25,712 eyes were included, of which 366 (1.42%) underwent early postoperative flap lifting. There was a significant reduction in early postoperative flap lifting rates from 2006 (2.46%) to 2015 (0.92%) (P = 0.001). Reasons for early flap lifting included striae (n = 301, 1.17%), diffuse lamellar keratitis (n = 62, 0.24%), flap dislocation (n = 20, 0.08%), epithelial ingrowth (n = 18, 0.07%), and interface debris (n = 15, 0.06%). There was a significant difference in rates and outcomes of flap relifting among high-volume surgeons (P < 0.001). The flap lift group had a significantly lower final safety index (0.95 ± 0.16 vs. 1.01 ± 0.15, P < 0.001), efficacy index (0.85 ± 0.26 vs. 0.94 ± 0.26, P < 0.001), and a higher distance from target refraction (0.39 ± 0.61 vs. 0.21 ± 0.46 D). In unilateral cases, the study eye had a lower safety index (P < 0.001), efficacy index (P < 0.001), and greater distance from target refraction (P = 0.003) compared with the fellow eye. After intervention, 81.1% of cases achieved full resolution, 10.1% achieved partial resolution, 4.1% required additional flap relifting, and 4.7% were nonresolved by the end of follow-up.

CONCLUSIONS

The main indication for early flap relifting after LASIK was striae, and most cases achieved full resolution. Although refractive and visual outcomes are lower in this group, they are, nevertheless, satisfactory.

Predictive Factors for Successful High Myopia Treatment Using High-Frequency Laser-In-Situ Keratomileusis

Aim

To evaluate the predictive factors of LASIK procedure for high myopia with or without astigmatism using a combination of high-frequency femtosecond-assisted LASIK followed by an excimer laser.

Methods

This study was a retrospective interventional case series study to evaluate myopic eyes undergoing high platform LASIK with FEMTO LDV Z2 intervention, followed by WaveLight®EX500 excimer laser machine. Subjects were divided into 2 groups: high myopia (SE of -6.01 to -9.00 D) and very high myopia (SE of -9.01 D or higher). Myopic eyes (Spherical Equivalent/SE) less than -13 D were included in this study. Visual Acuity (VA) was evaluated 1 day and 60 days after the procedure. Predictive factors, such as age, degree of sphere, degree of astigmatism, keratometric reading and axial length were analyzed to detect any influences affecting the final VA results.

Results

A total of 316 myopia eyes underwent intervention, mean age: 25.3±3.8 years. Target treatment was achieved in 96.1% of patients with high myopia and 69.9% of patients with very high myopia. High degree of sphere and astigmatism constitutes an important factor influencing final VA.

Conclusion

Modern machines provide a more promising efficacy and success of LASIK procedure in high myopia: important predictive factors were a high degree of sphere and astigmatism for achieving the optimal final outcome.

Wound healing in rabbit corneas after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser

PURPOSE

To characterize corneal wound healing in a rabbit model after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser.

SETTING

Departments of Ophthalmology and Anatomy II, University of Erlangen-Nürnberg and Wavelight GmbH, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Flapless refractive lenticule extraction was performed in 1 eye each of 20 New Zealand white rabbits (-5.0 diopters). Groups of 4 animals were euthanized after 48 hours, 1 week, 2 weeks, 4 weeks, and 3 months, respectively. Corneal samples were prepared for histology and fluorescence microscopy. To assess corneal cell death, proliferation, and myofibroblastic transdifferentiation, terminal uridine deoxynucleotidyl nick end-labeling (TUNEL) assay as well as immunostaining for Ki67 and α-smooth muscle actin (αSMA) were performed on sagittal cryosections.

RESULTS

Histology revealed a zone of keratocyte depletion with a thickness of approximately 50 μm around the extraction site. At 48 hours, pronounced TUNEL staining of keratocytes was detected around the interface (159.9 cells/mm ± 18.4 [SD]), which steadily decreased to 74.9 ± 19.8 cells/mm at 1 week and 5.7 ± 4.8 cells/mm at 2 weeks. Ki67 staining of keratocytes was evident at 48 hours (10.0 ± 3.8 cells/mm), which then decreased at 1 week (5.2 ± 1.7 cells/mm) and 2 weeks (0.4 ± 0.5 cells/mm). From 4 weeks onward, no TUNEL or Ki67 staining was detected. The corneal stroma was αSMA-negative at all timepoints.

CONCLUSION

Application of the 345 nm laser showed no signs of problematic repair processes in the cornea, which supports the initiation of the clinical phase.

Corneal Lenticule Allotransplantation After Femtosecond Laser Small Incision Lenticule Extraction in Rabbits

PURPOSE

To investigate the feasibility of allotransplanting extracted lenticules after femtosecond laser-assisted small incision lenticule extraction (SMILE) in rabbits and the subsequent healing process.

METHODS

Fourteen New Zealand white rabbits were divided evenly into 2 groups. The rabbits in group A received SMILE procedures with a -6.00 D correction. The lenticules from group A were immediately inserted into a femtosecond laser-created corneal stromal pocket in group B. After surgery, the anterior segment was assessed in vivo by slit-lamp microscopy, corneal topography, optical coherence tomography, and confocal microscopy. All eyes were enucleated for hematoxylin-eosin staining and transmission electron microscopy after the animals were killed.

RESULTS

At postoperative day 1, there was moderate corneal edema in the implanted lenticule stroma. At 6 months, the lenticules were integrated with the surrounding tissue, and the boundary could not be identified through slit-lamp microscopy; regenerated branches of the corneal nerves were thicker than at postoperative month 1 as observed through confocal microscopy. The central corneal thickness increased by 58.75 ± 21.58 μm. The lenticules were gradually integrated with the surrounding tissue, and their density was similar to the adjacent tissue according to optical coherence tomography; however, a clear boundary between the lenticule and surrounding tissue was detectable using light microscopy and transmission electron microscopy, revealing disordered fibers and decreased keratocytes in implanted lenticules.

CONCLUSIONS

In this model it is feasible and safe to allotransplant extracted corneal lenticules after SMILE. Healing of implanted lenticules after SMILE is stable at postoperative 6 months, but collagen fiber rearrangement requires further investigation.

Corneal flap thickness with the Moria M2 single-use head 90 microkeratome in 72 consecutive LASIK procedures

Purpose

This study aimed to evaluate the accuracy and consistency of corneal flap thickness in laser-assisted in situ keratomileusis (LASIK) with the Moria M2 single-use head 90 microkeratome.

Methods

The central corneal thickness of 72 (37 right, 35 left) eyes of 37 patients was measured by ultrasonic pachymetry preoperatively and intraoperatively after flap cut. The Moria M2 single-use head 90 microkeratome was used to create a superior hinged flap in all eyes. The right eyes were always operated on before the left eyes in each patient, using the same blade in all bilateral cases. All patients underwent LASIK for myopia and/or myopic astigmatism using VISX Star S4 platform.

Results

The mean preoperative spherical equivalent refraction was −3.55±2.30 D (range: −0.625 to −11.00 D), preoperative central corneal thickness by ultrasonic pachymetry was 541±26.82 µm (490–600 µm) and steepest K was 44.08±1.49 D (40–46.75 D) in all eyes. The mean flap thickness was 136.97±20.07 µm (106–192 µm), 131.2±19.5 µm (91–192 µm), and 134.16±19.85 µm (91–192 µm) in the right, left, and both eyes, respectively. A positive significant relationship was found between flap thickness and preoperative ultrasonic pachymetry thickness. No significant relationship was found between flap thickness and the age, preoperative spherical equivalent, and preoperative steepest K. The difference between the first and second eyes was not significant. There were no major intraoperative and postoperative complications in all eyes.

Conclusion

The Moria M2 single-use head 90 microkeratome cut relatively thicker flaps than were intended. The flap thickness range was quite wide. This was a disadvantage for the accuracy and consistency of corneal flap thickness.

Laser Vision Correction in Treating Myopia

Myopia is a generally benign refractive error with an increasing prevalence worldwide. It can be corrected temporarily with glasses and contact lenses and permanently with laser vision correction. The 2 main procedures currently being performed for myopia correction are photorefractive keratectomy and laser-assisted in situ keratomileusis. Each technique has its advantages, but they appear to yield similar visual outcomes 1 year after surgery. Laser vision correction for myopia was considered a paradigm shift because healthy eyes could now undergo a surgical procedure to permanently and safely correct the error by altering the center of the cornea, which was previously off limits because of the potential for loss of transparency. Customized ablation using wavefront aberrometry and its optimized profiles were created to correct higher-order aberrations and give more vision quality to patients. Topography-guided ablation, initially used for complex retreatments, shows potential to make vision even better than glasses and contact lenses in a recent study on previously untreated eyes. One major concern is to identify corneas that are at risk of developing ectasia after the procedure. Topographic and tomographic screening indices have been implemented clinically, but there is still much to learn about corneal biomechanics. A more recently developed procedure for myopia correction is small-incision lenticule extraction, in which a lenticule is created in the cornea's stroma with a femtosecond laser and extracted through a small corneal incision. Long-term outcomes and new complication risks need to be better understood as this procedure develops.

Three-Year Longitudinal Survey Comparing Visual Satisfaction with LASIK and Contact Lenses

PURPOSE

To assess patient satisfaction and perceived outcomes with different methods of refractive error correction through annual surveys administered over a 3-year period.

DESIGN

Prospective, longitudinal, parallel-group, multicenter survey.

PARTICIPANTS

A total of 1800 subjects, aged 18 to 60 years, who had LASIK or continued using contact lenses.

METHODS

Twenty sites across the United States enrolled subjects who completed a study-specific baseline survey during a contact lens examination or while being evaluated as a candidate for LASIK. Links to follow-up surveys were emailed annually for 3 years. Between-group differences were assessed by analysis of variance, and associations were assessed by logistic multivariate regression.

MAIN OUTCOME MEASURES

Visual satisfaction.

RESULTS

Of 1800 subjects, 694 (39%) comprised the control group who continued contact lens wear, 819 (45%) wore contacts at baseline and had LASIK, and 287 (16%) wore glasses at baseline and had LASIK. Most contact lens users had worn them successfully ≥5 years. The proportion expressing strong satisfaction with their current vision correction method decreased from 63% at baseline to 54% at year 3 in the contact lens control group, whereas 88% of former contact lens wearers and 77% of former glasses wearers were strongly satisfied with LASIK at year 3. Patients 40 years of age or younger when they had LASIK were somewhat more likely to be strongly satisfied than older patients. LASIK significantly reduced difficulties with night driving and nighttime visual disturbances among former contact lens users and former glasses users. The proportion with dry eye symptoms at 1, 2, or 3 years after LASIK was not significantly increased relative to baseline contact lens wear but was significantly increased relative to baseline glasses use, consistent with many glasses users having tried and abandoned contact lenses because of latent dry eye problems. Compared with continued contact lens wear, LASIK significantly reduced the self-reported rates of eye infections, ulcers, and abrasions each year.

CONCLUSIONS

Compared with contact lens wear, current LASIK technology improved ease of night driving, did not significantly increase dry eye symptoms, and resulted in higher levels of satisfaction at 1, 2, and 3 years follow-up.

Angiopoietin 2 expression in the cornea and its control of corneal neovascularisation

PURPOSE

To define proangiogenic angiopoietin 2 (ANG2) expression and role(s) in human and mouse vascularised corneas. Further, to evaluate the effect of ANG2 inhibition on corneal neovascularisation (CNV).

METHODS

CNV was induced in FVB mice by means of intrastromal suture placement. One group of animals was sacrificed 10 days later; corneas were immunostained for ANG2 and compared with (i) mouse non-vascularised corneas and (ii) human vascularised and non-vascularised corneas. A second group of CNV animals was treated systemically with an anti-ANG2 antibody. After 10 days, the corneas were whole-mounted, stained for CD31 and LYVE1 and lymphatic/blood vessels quantified. In another set of experiments, the corneal basal Bowman membrane was either (i) removed or (ii) left in place. After 2 or 10 days the corneas were removed and immunostained for collagen IV, ANG2, CD31, LYVE1, CD11b and MRC1 markers.

RESULTS

In human beings and mice, ANG2 is expressed only in the epithelium, and, mildly, in the endothelium, of the avascular cornea. Instead, it is expressed in the epithelium, endothelium and stroma of vascularised corneas. Disruption of the Bowman membrane is associated with a significant increase of (i) ANG2 stromal expression and (ii) proangiogenic macrophage infiltration in the corneal stroma. Finally, blocking ANG2 significantly reduced hemangiogenesis, lymphangiogenesis and macrophage infiltration.

CONCLUSIONS

Balancing proper healing and good vision is crucial in the cornea, constantly exposed to potential injuries. In this paper, we suggest the existence of a mechanism regulating the onset of inflammation (and associated CNV) depending on injury severity.

Factors Affecting Long-term Myopic Regression after Laser In Situ Keratomileusis and Laser-assisted Subepithelial Keratectomy for Moderate Myopia

PURPOSE

High myopia is known to be a risk factor for long-term regression after laser refractive surgery. There have been few studies about the correction of moderate myopias that did not need retreatment after long-term follow-up. We evaluated 10 years of change in visual acuity and refractive power in eyes with moderate myopia after laser refractive surgery.

METHODS

We included patients that had undergone laser in situ keratomileusis (LASIK) or laser-assisted subepithelial keratectomy (LASEK) to correct their myopia and that had at least 10 years of follow-up. We evaluated the stability of visual acuity in terms of safety, efficacy, and refractive changes at examinations 6 months and 1, 2, 5, 7, and 10 years after surgery.

RESULTS

The study evaluated 62 eyes (36 eyes in LASIK patients and 26 eyes in LASEK patients). In both groups, the efficacy index tended to decrease, and it was consistently higher in the LASEK group compared to the LASIK group over the 10 years of follow-up. The safety index improved over 10 years and was always higher than 0.9 in both groups. The difference between the spherical equivalent at 6 months postoperatively and later periods was statistically significant after 5, 7, and 10 years in both groups (LASIK, p = 0.036, p = 0.003, and p < 0.001, respectively; LASEK, p = 0.006, p = 0.002, and p = 0.001, respectively). Ten years after surgery,26 eyes (66.7%) in the LASIK group and 19 eyes (73.1%) in the LASEK group had myopia greater than 1 diopter. In comparison with the thickness at 6 months postoperatively, central corneal thickness was significantly increased after 5, 7, and 10 years in both LASIK and LASEK groups (LASIK, p < 0.001, p < 0.001, and p < 0.001, respectively; LASEK, p = 0.01, p < 0.001, and p < 0.001, respectively).

CONCLUSIONS

Moderately myopic eyes showed progressive myopic shifting and corneal thickening after LASIK and LASEK during 10 years of follow-up. We also found that early refractive regression may indicate the long-term refractive outcome.

Comparison of performances of femtosecond laser and microkeratome for thin-flap laser in situ keratomileusis

OBJECTIVE

To compare the clinical outcomes of femtosecond laser (FS) and microkeratome (MK) for thin-flap in situ keratomileusis (LASIK).

MATERIALS AND METHODS

Data from patients with moderate to high myopia (spherical equivalent, >-4 diopters [D]) who underwent thin-flap LASIK using FS (199 eyes/110 patients) and MK (157 eyes/86 patients) were analyzed in this retrospective study. Preoperative and postoperative data were recorded from day 1 and months 1 and 3, postoperatively. Visual and refractive outcomes were compared for efficacy, safety, predictability, stability, and the efficacy and safety indices.

RESULTS

Three months postoperatively, more eyes in the FS group had an uncorrected distance visual acuity (UCVA) of 20/40 or better compared to MK group (relative risk [RR] 1.01, 95% confidence interval [CI], 0.97-1.05, P = 0.58); significantly more eyes in FS group had an UCVA of 20/20 or better (RR, 1.26, 95%CI, 1.08-1.48, P = 0.003). Intraoperative bleeding occurred in 5% and 36.7%, respectively, of FS and MK groups. There were no significant differences in the refractive predictability within spherical equivalents of 0.5 D (FS, 72%; MK, 63%) and 1.0 D (FS, 90%; MK, 86%). Both groups showed good stability 3 months, postoperatively. The efficacy index in FS group was 113.4%; that in MK group was 102.5% at 3 months postoperatively (P < 0.05). The safety indices for FS and MK groups at 3 months postoperatively were 116.4% and 108.2%, respectively (P < 0.05).

CONCLUSIONS

Both methods of thin-flap created LASIK were effective, safe, predicable, and stable. FS group had significant improvements in efficacy and safety, confirmed by the efficacy and safety indices, compared to MK group. Lasers Surg. Med. 48:596-601, 2016. © 2016 Wiley Periodicals, Inc.

Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser

PURPOSE

To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery.

SETTING

Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium.

RESULTS

Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable.

CONCLUSION

The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty.

FINANCIAL DISCLOSURES

Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned.

Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components

The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

Evaluation of a 345 nm Femtosecond Laser for Corneal Surgery with Respect to Intraocular Radiation Hazard

PURPOSE

We report our findings from a preclinical safety study designed to assess potential side effects of corneal ultraviolet femtosecond laser treatment on lens and retina.

METHODS

Refractive lenticules (-5 dpt) with a diameter of 6 mm were created in the right cornea of eight Dutch Belted rabbits. Radiant exposure was 0.5 J/cm² in two animals and 18 J/cm² in six animals. The presence of lens opacities was assessed prior to and up to six months following laser application using Scheimpflug images (Pentacam, Oculus) and backscatter analysis (Opacity Lensmeter 702, Interzeag). Ganzfeld flash and flicker electroretinogram (ERG) recordings were obtained from both eyes prior to and up to six weeks following laser application. At the study endpoint, retinas were examined by light microscopy.

RESULTS

Independent of energy dose applied, no cataract formation could be observed clinically or with either of the two objective methods used. No changes in ERG recordings over time and no difference between treated and untreated eye were detected. Histologically, retinal morphology was preserved and retinal pigment epithelium as well as photoreceptor inner and outer segments appeared undamaged. Quantitative digital image analysis did not reveal cell loss in inner or outer nuclear layers.

CONCLUSIONS

Our analysis confirms theoretical considerations suggesting that ultraviolet femtosecond laser treatment of the cornea is safe for intraocular tissues. Transmitted light including stray light induces no photochemical effects in lens or retina at energy levels much higher than required for the clinical purpose. These conclusions cannot be applied to eyes with pre-existing retinal damage, as these may be more vulnerable to light.

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.

[Corneal morphometric predictive models from ametropia to excimer laser treatment]

OBJECTIVE

To develop corneal morphometric models with refractive error in excimer laser surgery.

METHOD

A prospective-longitudinal study was conducted on 78 patients (151 eyes) using the LASIK surgical technique, and 56 patients (111 eyes) with myopic astigmatism using ESIRIS (Schwind-Germany) equipment with pendulous microkeratome. The results were analyzed using descriptive statistics. A NIDEK Confoscan microscope was used to obtain and study the images.

RESULTS

After LASIK treatment 84.3% of the variations in epithelium thickness variations were due to the magnitude of refractive error and the epithelium thickness before LASIK treatment. More than two-thirds (68.8%) of the variations in keratocyte density variations in posterior flap and 48.2% of the variations in the anterior retroablation zone were due to the magnitude of the refractive error. Variations of 90% were found in the corneal thickness after LASEK, which were due to the magnitude of the refractive error before LASEK.

CONCLUSIONS

Predictive models reveal that morphometrical variations depend of the magnitude of the refractive error. These models are very important in the selection of patient for refractive surgery, and also for the specific technique to use.

Histopathological study of corneal flap striae following laser in situ keratomileusis in rabbits

The aim of the present study was to investigate the histopathological changes and wound healing process of rabbit corneas following conventional laser in situ keratomileusis (LASIK) with and without the complication of flap macrostriae. The right eyes of 14 rabbits underwent LASIK with the formation of flap striae (macrostriae group) and the left underwent LASIK alone (control group). Two rabbits were selected at random for sacrifice on days 1, 3, 7 and 14, and at 1, 3 and 6 months postoperatively. The histopathological characters of the corneas were compared by hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) and Masson staining. In the control group, the epithelial basement membrane of the cornea exhibited microstriae and the arrangement of stromal collagen fibers was regular. The width of the microstriae in the flap was 20-40 μm one week after surgery and the microstriae were no longer visible two weeks postoperatively. In the macrostriae group, infiltration of polymorphonuclear cells occurred around the incision and irregular hyperplasia of the epithelium was observed due to undulation of the epithelial basement membrane on the first postoperative day. The collagen fibers and striae of the corneal stroma exhibited irregular undulation one month postoperatively. The area between the corneal flap and stromal bed was distinctly stained by PAS and Masson stains. Macrostriae with a width of 80-120 μm affecting two-thirds of the entire cornea remained visible six months postoperatively. In conclusion, the inflammatory reactions and clinical impact of flap macrostriae were severe. Macrostriae involving two-thirds of the entire cornea remained visible six months postoperatively. Longer-term studies are required to further elucidate the issues associated with corneal flap striae.

Changes in the accommodation-convergence relationship after the Artisan phakic intraocular lens implantation for myopic patients

Purpose

To evaluate the change of accommodation-convergence parameters after implantation of Artisan phakic intraocular lens (PIOL).

Methods

Prospective study for the patients with the Artisan PIOL implantation was performed. A total of 37 patients (3 males and 34 females) enrolled the study. Preoperatively, convergence amplitude, the stimulus accommodative convergence per unit of accommodation (AC/A) ratio and the near point of convergence (NPC) were evaluated. After the Artisan PIOL implantation, the identical evaluations were repeated at 1 week, 1, 3, and 6 months after the surgery.

Results

Mean age was 24.3 ± 4.8 years old, and preoperative refractive error was -8.92 ± 4.13 diopters (D). After the implantation, mean refractive errors significantly decreased to within ±1.00 D, and noticeable complications were not found. The convergence amplitude and the stimulus AC/A ratio increased 1 month after the surgery, but progressively stabilized afterward to near preoperative values. NPC didn't show any significant change over follow-up period up to 6 months.

Conclusions

These results regarding implantation of the Artisan PIOL revealed the increase of accommodation-convergence relationship within first 1 month after the surgery, but progressive stabilization was noted during follow-up periods.

Post-LASIK dry eye

Laser-assisted in situ keratomileusis (LASIK) is a frequently performed corneal refractive surgery with excellent refractive outcomes. The most common complication of LASIK is dry eyes, with virtually all patients developing some degree of dryness in the immediate postoperative period. Identifying preoperative dry eyes, and conscientious attention and treatment in the perioperative time period, can lead to enhanced patient satisfaction and more accurate visual outcomes. Improved understanding of the development of dry eyes after LASIK will advance our understanding of the complex pathophysiology of dry eye disease.

Acupuncture for dry eye syndrome after refractive surgery: study protocol for a randomized controlled trial

BACKGROUND

Dry eye syndrome is a frequent complication of refractive surgery. Acupuncture has been widely used to alleviate the associated symptoms. However, the use of acupuncture for patients who suffer from dry eye syndrome following refractive surgery has certain drawbacks. This pilot study aims to evaluate the efficacy of acupuncture treatment in treating the signs and symptoms of dry eye syndrome after refractive surgery.

METHODS/DESIGN

Forty participants will be randomly assigned to the acupuncture plus usual care group or the usual care control group. The acupuncture plus usual care group will undergo treatments on seventeen acupuncture points, three times per week for four weeks. The control group will receive only usual care during the same period. The primary outcomes will be scores on the Ocular Surface Disease Index (OSDI) and the results of examinations at 1, 3, 5, and 13 weeks. The secondary outcomes will be Tear Film Break-up Time (TBUT), as well as scores on the Schirmer-I test, visual analog scale (VAS), and quality of life (QOL) questionnaire for the self-assessment of ocular discomfort. Digital photographs will be taken to document the pattern of fluorescein staining observed on the corneal surface. The results of the Schirmer-I test, TBUT, and fluorescein-stained corneal surface digital photographs will be assessed at the screening and at week 13. VAS scores will be assessed at the screening, as well as at 1, 3, 5, and 13 weeks. QOL will be evaluated at 1, 3, 5, and 13 weeks.

DISCUSSION

This trial will provide primary data with which to investigate the clinical effectiveness and safety of acupuncture treatment for dry eye syndrome after refractive surgery.

TRIAL REGISTRATION

Current Controlled (Identifier: KCT0000727).

The role of corneal innervation in LASIK-induced neuropathic dry eye

Almost half the patients who undergo laser in situ keratomileusis (LASIK) experience dry eye following the procedure. However, the etiology of LASIK-induced dry eye is unclear. The purpose of this review is to examine and summarize the current evidence for the etiology of LASIK-induced dry eye, with a focus on ocular surface sensitivity and corneal innervation. Evidence suggests that the alteration of corneal nerves after LASIK is the most likely cause of the subjective symptoms of LASIK-induced dry eye, even though corneal sensitivity and the clinical indicators of dry eye return to apparently normal values within a year due to the partial recovery of the corneal nerve plexus. The hypothesis is explored that dry eye symptoms following LASIK may result from abnormal sensation due to LASIK-induced corneal neuropathy. Other factors, such as alterations in conjunctival goblet cell density, might also contribute to the symptoms and signs of LASIK-induced dry eye. Inter-relationships between nerve morphology, tear neuropeptide levels and dry eye require further investigation. A better understanding of this phenomenon may result in improved management of post-LASIK dry eye.

Combined hydrogel inlay and laser in situ keratomileusis to compensate for presbyopia in hyperopic patients: one-year safety and efficacy

PURPOSE

To perform a feasibility study of the safety and efficacy of a corneal-contouring inlay with concurrent laser in situ keratomileusis (LASIK) to treat hyperopic presbyopia.

SETTING

Private clinic, Tijuana, Mexico.

DESIGN

Prospective interventional case series.

METHODS

Hyperopic patients received LASIK in both eyes and a corneal inlay under the femtosecond laser flap in the nondominant eye. The inlay is designed to reshape the anterior corneal curvature, creating a near-center multifocal refractive effect. Main safety outcomes were retention of preoperative corrected distance and near visual acuities and reports of adverse events. Efficacy was determined through measurements of near, intermediate, and distance visual acuities and patient questionnaires on visual task ability and satisfaction.

RESULTS

The study enrolled 16 patients. All eyes with an inlay achieved an uncorrected near visual acuity (UNVA) of 20/32 or better by the 1-week postoperative examination and at every visit thereafter. The mean monocular and binocular UNVA was 20/27 or better at all visits. The mean binocular uncorrected distance visual acuity improved significantly from 20/53 preoperatively to 20/19 postoperatively (P<10(-5)). One inlay was explanted during the study. At 1 year, all 14 patients analyzed were satisfied or very satisfied with their near, distance, and overall vision.

CONCLUSIONS

The hydrogel corneal inlay with concurrent LASIK improved uncorrected near, intermediate, and distance visual acuity in hyperopic presbyopic patients with high patient satisfaction and visual task ability. This represents a new indication for this recently developed technology.

Laser in situ keratomileusis in 2012: a review

Laser in situ keratomileusis (LASIK) is a safe and effective treatment for refractive error. A combination of technological advances and increasing surgeon experience has served to further refine refractive outcomes and reduce complication rates. In this article, we review LASIK as it stands in late 2012: the procedure, indications, technology, complications and refractive outcomes.

One-year safety and efficacy results of a hydrogel inlay to improve near vision in patients with emmetropic presbyopia

PURPOSE

To conduct a feasibility study of the safety and efficacy of a corneal contouring inlay as a treatment for emmetropic presbyopia.

METHODS

The Raindrop corneal inlay (ReVision Optics, Inc., Lake Forest, CA) was implanted on the corneal stromal bed beneath a keratotomy flap in 20 nondominant eyes of 20 patients. The implant is designed to cause a change in the curvature of the overlying cornea, with a subsequent multifocal change in refractive power. Efficacy outcome was defined as at least 75% of eyes with uncorrected near visual acuity of 0.3 logMAR (20/40 Snellen) or better at 6 months. Main safety outcomes were retention of preoperative best-corrected distance visual acuity and reports of adverse events. Other outcome measures included contrast sensitivity; near, intermediate, and distance visual acuities; patient satisfaction; spectacle use; and complications.

RESULTS

All implanted eyes achieved uncorrected near visual acuity of 0.3 logMAR (20/40 Snellen) or better by the 1-week postoperative examination and remained so throughout the 1-year follow-up period, also averaging less than 0.1 logMAR (20/25 Snellen) monocularly and binocularly throughout that period. Mean binocular uncorrected distance visual acuity remained within 0.02 logMAR of the preoperative mean throughout the study. One patient who was dissatisfied with the resulting vision underwent explantation. At 1 year, 16 of 19 patients seldom or never wore glasses and all 19 were satisfied or very satisfied with their overall vision.

CONCLUSIONS

The hydrogel corneal inlay improved uncorrected near and intermediate visual acuity in patients with emmetropic presbyopia, with high patient satisfaction and little effect on distance visual acuity.

Laser-assisted in-situ keratomileusis (LASIK) versus photorefractive keratectomy (PRK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

To compare the effectiveness and safety of LASIK and PRK for correction of myopia by examining post-treatment uncorrected visual acuity, refractive outcome, loss of best spectacle-corrected visual acuity, pain scores, flap complications in LASIK, subepithelial haze, adverse events, quality of life indices and higher order aberrations.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 11), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2012), EMBASE (January 1980 to November 2012), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to November 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 November 2012. We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing LASIK and PRK for the correction of any degree of myopia.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We summarised data using the odds ratio and mean difference. We combined odds ratios using a random-effects model after testing for heterogeneity.

MAIN RESULTS

We included 13 trials (1135 participants, 1923 eyes) in this review. Nine of these trials randomised eyes to treatment, two trials randomised people to treatment and treated both eyes, and two trials randomised people to treatment and treated one eye. None of the paired trials reported an appropriate paired analysis. We considered the overall quality of evidence to be low for most outcomes because of the risk of bias in the included trials. There was evidence that LASIK gives a faster visual recovery than PRK and is a less painful technique. Results at one year after surgery were comparable: most analyses favoured LASIK but they were not statistically significant.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery and is a less painful technique than PRK. The two techniques appear to give similar outcomes one year after surgery. Further trials using contemporary techniques are required to determine whether LASIK and PRK as currently practised are equally safe. Randomising eyes to treatment is an efficient design, but only if analysed properly. In future trials, more efforts could be made to mask the assessment of outcome.

Increased preference of surface ablation over laser in situ keratomileusis between 2008-2011 is correlated to risk of ecatasia

PURPOSE

To evaluate the trends in corneal refractive procedure selection for the correction of myopia, focusing on the relative proportions of laser in situ keratomileusis (LASIK) and surface ablation procedures.

METHODS

Only eyes that underwent LASIK or surface ablation for the correction of myopia between 2008-2011 were included in this retrospective study. Additional recorded parameters included patient age, preoperative manifest refraction, corneal thickness, and calculated residual corneal bed thickness. A risk score was given to each eye, based on these parameters, according to the Ectasia Risk Factor Score System (ERFSS), without the preoperative corneal topography.

RESULTS

This study included 16,163 eyes, of which 38.4% underwent LASIK and 61.6% underwent surface ablation. The risk score correlated with procedure selection, with LASIK being preferred in eyes with a score of 0 and surface ablation in eyes with a score of 2 or higher. When controlling for age, preoperative manifest refraction, corneal thickness, and all parameters, the relative proportion of surface ablation compared with LASIK was found to have grown significantly during the study period.

CONCLUSIONS

Our results indicate that with time, surface ablation tended to be performed more often than LASIK for the correction of myopia in our cohort. Increased awareness of risk factors and preoperative risk assessment tools, such as the ERFSS, have shifted the current practice of refractive surgery from LASIK towards surface ablation despite the former's advantages, especially in cases in which the risk for ectasia is more than minimal (risk score 2 and higher).

Influence of anterior segment power on the scan path and RNFL thickness using SD-OCT

PURPOSE

Retinal nerve fiber layer (RNFL) thickness measures with spectral domain-optical coherence tomography (SD-OCT) provide important information on the health of the optic nerve. As with most retinal imaging technologies, ocular magnification characteristics of the eye must be considered for accurate analysis. While effects of axial length have been reported, the effects of anterior segment optical power on RNFL thickness measures have not been described fully to our knowledge. The purpose of our study was to determine the influence of the optical power change at the anterior corneal surface, using contact lenses, on the location of the scan path and measurements of RNFL thickness in normal healthy eyes.

METHODS

We recruited 15 normal subjects with less than 6 diopters (D) of ametropia and no ocular pathology. One eye of each subject was selected randomly for scanning. Baseline SD-OCT scans included raster cubes centered on the optic nerve and macula, and a standard 12-degree diameter RNFL scan. Standard 12-degree RNFL scans were repeated with 10 separate contact lenses, (Proclear daily, Omafilcon A/60%) ranging from +8 to -12 D in 2-D steps. The extent of the retinal scan, and RNFL thickness and area measures were quantified using custom MATLAB programs that included ocular biometry measures (IOL Master).

RESULTS

RNFL thickness decreased (0.52 μm/D, r = -0.33, P < 0.01) and the retinal region scanned increased (0.52%/D, r = 0.97, P < 0.01) with increase in contact lens power (-12 to +8). The normalized/percentage rates of change of RNFL thickness (-0.11/mm, r = -0.67, P < 0.01) and image size (0.11/mm, r = 0.96, P < 0.01) were related to axial length. Changes in the retinal region scanned were in agreement with transverse scaling, computed with a three surface schematic eye (R(2) = 0.97, P < 0.01). RNFL area measures, that incorporated the computed transverse scaling, were not related significantly to contact lens power (863 μm(2)/D, r = 0.06, P = 0.47).

CONCLUSIONS

Measurements of RNFL thickness by SD-OCT are dependent on the optics of the eye, including anterior segment power and axial length. The relationships between RNFL thickness measures and optical power are a direct reflection of scan path location with respect to the optic nerve head rim, caused by relative magnification. An incorporation of transverse scaling to RNFL area measures, based on individualized ocular biometry, eliminated the magnification effect.

Optical and visual quality comparison of implantable Collamer lens and laser in situ keratomileusis for myopia using an adaptive optics visual simulator

Purpose. To compare optical and visual quality of the implantable Collamer lens (ICL) and laser in situ keratomileusis (LASIK) for myopia. Methods. An adaptive optics visual simulator (CRX1, Imagine Eyes, France) was used to simulate the vision after ICL implantation and LASIK procedure from the wavefront aberration pattern for -3 and -6 D. Monocular visual acuity (VA) at different contrasts and contrast sensitivity (CS) at 10, 20, and 25 cycles/degree (cpd) were measured for 3- and 5-mm pupils. Modulation transfer function (MTF) and point spread function (PSF) were calculated for a 5-mm pupil. Results. The ICL showed a MTF near of diffraction-limited MTF, but the post-LASIK of MTF worsened moving away from both curves. Statistically significant differences were found in VA between both procedures for all conditions (p<0.05). For -3 D ICL and LASIK, we did not find statistically significant differences in CS between the procedures for both pupils and any spatial frequencies (p>0.05). But for -6 D ICL and LASIK, the effect of aberrations became apparent, finding statistically significant differences in CS between both procedures for 2 pupils and all spatial frequencies evaluated (p<0.05). In all cases optical and visual quality was better with the ICL procedure. Conclusions. Both ICL and LASIK procedures provide good optical and visual quality, although the ICL provides better outcomes, especially for large refractive errors and pupil sizes. These outcomes are due to the LASIK procedure inducing higher higher-order aberrations than ICL implantation.

Outcomes of refractive surgery in patients with topographic superior corneal steepening

PURPOSE

To evaluate the outcomes of refractive surgery in patients with topographic superior corneal steepening.

METHODS

This retrospective, noncomparative, interventional, clinical study included 16 patients (29 eyes) with persistent superior corneal steepening as a variation of corneal curvature (inferior to superior topographic corneal difference of at least 1.00 diopter [D] at a 3-mm zone) not related to any underlying disease or condition who underwent corneal refractive surgery. Refractive, keratometric, and visual outcomes were evaluated preoperatively and at 1, 3, 6, 12, and 24 months postoperatively.

RESULTS

Twenty-two eyes underwent photorefractive keratectomy and 7 eyes underwent LASIK. Mean follow-up was 27.38±2.37 months (range: 25 to 32 months). Mean preoperative inferior to superior keratometric difference was 1.61±0.36 D (range: 1.20 to 2.63 D). Mean preoperative spherical equivalent refraction was -4.45±1.66 D (range: -2.25 to -8.00 D), which decreased to -0.09±0.61 D (range: +0.75 to -1.38 D) (P<.05) at last follow-up. Mean preoperative topographic corneal astigmatism was 1.44±0.79 D (range: 0.52 to 3.83 D), which decreased to 0.66±0.39 D (P<.05) 3 months postoperatively and remained stable during follow-up (P<.54). Mean preoperative uncorrected distance visual acuity and corrected distance visual acuity in logMAR units were 1.57±0.62 and 0.02±0.06, respectively, which improved at last follow-up to 0.00±0.05 and -0.02±0.04, respectively. No intra- or postoperative complications were noted; specifically, no patients developed postoperative ectasia.

CONCLUSIONS

Corneal refractive surgery in patients with isolated topographic superior corneal steepening provided acceptable refractive and visual outcomes without any intra- or postoperative complications. Diligence is required to screen for the potential of ectatic corneal disorders in this population. Photorefractive keratectomy may be a safer option for these patients than LASIK.

Meta-analysis of wavefront-guided vs. wavefront-optimized LASIK for myopia

PURPOSE

To detect possible differences in clinical outcomes between wavefront-guided laser in situ keratomileusis (LASIK) and wavefront-optimized LASIK for the treatment of myopia.

METHODS

A comprehensive literature search of Cochrane Library, MEDLINE, and EMBASE to identify relevant trials comparing LASIK with wavefront-guided and wavefront-optimized. A meta-analysis was performed on the results of the reports. Statistical analysis was performed using RevMan 5.0 software.

RESULTS

Seven articles describing a total of 930 eyes were identified. There were no statistically significant differences in the final proportion of eyes achieving uncorrected distance visual acuity of 20/20 or better [odds ratio, 1.04; 95% confidence interval (CI), 0.66 to 1.65; p = 0.86], manifest refractive spherical equivalent within ± 0.50 D of the target (odds ratio, 0.96; 95% CI, 0.53 to 1.75; p = 0.90). No patient lost ≥ 2 lines of distance-corrected visual acuity at posttreatment. The changes in higher order aberrations were not statistically significant different between the two groups with preoperative root-mean-square (RMS) higher order aberrations <0.3 μm (weighted mean difference, 0.01; 95% CI, -0.02 to 0.04; p = 0.57). However, wavefront-guided had a significant better postoperative aberration profile than wavefront-optimized with preoperative RMS higher order aberrations >0.3 μm (weighted mean difference, -0.10; 95% CI, -0.15 to -0.06; p < 0.00001).

CONCLUSIONS

Both wavefront-guided and wavefront-optimized LASIK have shown excellent efficacy, safety, and predictability. The wavefront-guided technology may be a more appropriate choice for patients who have preoperative RMS higher order aberrations >0.3 μm.

Timing of eyelid surgery in the setting of refractive surgery: preoperative and postoperative considerations

PURPOSE OF REVIEW

With any operation, the surgeon should be aware of predisposing factors that may lead to postoperative complications. Here we review the major factors due for consideration in both eyelid and refractive eye surgery, preoperatively and postoperatively, and consider the importance of timing to lessen the inherent risks of each procedure.

RECENT FINDINGS

Refractive surgery can affect corneal sensation by ablating the corneal nerves and can cause serious corneal complications if followed by eyelid surgery. Studies find that patients undergoing eyelid surgery have a change in astigmatic error of as much as 1.0 D during the first 3 postoperative months. The longest reported follow-up period of astigmatic changes in adult patients following eyelid ptosis surgery is 1 year and a considerable number of patients had a change in cylinder of up to 0.3 D postoperatively. Blepharoplastic surgery is also reported to cause astigmatic changes postoperatively, significantly more if entire fat pads are removed.

SUMMARY

To prevent corneal exposure, postrefractive eyelid surgery should be performed at least 6 months after lamellar ablative procedures and at least 3 months after surface ablative procedures. Refractive surgery revision may be necessary when astigmatic error occurs and should be carried out no earlier than 6 months postoperatively to allow for stabilization. Cosmetic blepharoplasty with fat pad debulking should be performed at least 6 months prior to refractive surgery to allow for any potential corneal astigmatic change to stabilize, for regained strength in the orbicularis, and for improved tear film distribution.

Refractive surgery: a treatment for and a cause of strabismus

PURPOSE OF REVIEW

The purpose of this article is to review refractive surgery as a means of treatment for strabismus and as a potential cause of strabismus and binocular diplopia.

RECENT FINDINGS

Numerous studies have reported that refractive surgery is effective in correcting certain types of strabismus such as accommodative and partially accommodative esotropia. Studies on the treatment of exotropia related to anisometropia have demonstrated less favorable outcomes. In patients without manifest strabismus preoperatively, recent studies have shown that strabismus and diplopia can occur after refractive surgery. Appropriate clinical testing and risk stratification are essential to determine whether a patient is at increased risk for postoperative strabismus and diplopia.

SUMMARY

Refractive surgery can be useful in patients with accommodative and partially accommodative esotropia. A thorough history and clinical examination is extremely important to expose potential risk factors in all patients undergoing refractive surgery. Based on the designated risk level, more advanced testing may be warranted.

Real-time measurement of ArF excimer laser corneal tissue ablation rates using cross-correlation of laser waveforms

The current popularity of excimer laser refractive surgery suggests a need for continued research and refinements to further improve clinical outcomes. A fundamental limitation of current clinical systems is the lack of real-time feedback specifically addressing the laser-tissue interactions as directly related to laser ablation rates. This paper reports data to assess the feasibility of a novel approach that holds promise as a real-time feedback scheme based on comparison of the incident and reflected laser pulse waveforms, as quantified using a cross-correlation algorithm. The approach is evaluated for ablation of bovine cornea over a range of clinically relevant laser fluences. A linear relationship was observed between several cross-correlation metrics and the directly measured corneal ablation rate, yielding an average RMS predictive error of 3.9% using a 25-shot average reflected waveform. Assessment of the cross-correlation approach for single-shot ablation data revealed a brief transient corresponding to the first few laser pulses, which is attributed to a slight hydration gradient near the surface of the de-epithelialized cornea. Clinical refractive data are necessary to assess the precision of this approach for actual refractive surgery.