Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia

[Excimer laser in keratoconus management]

Visual rehabilitation in keratoconus is a challenge, notably because of the significant irregular astigmatism and optical aberrations that it induces. Many surgical techniques have been developed in addition to, or in the case of failure of, spectacles and rigid gas permeable contact lenses: intracorneal ring segments, intraocular lenses, excimer laser and, as a last resort, keratoplasty. Excimer laser photoablates the cornea, allowing remodeling of its surface. There are various treatment modes (wavefront-optimized, wavefront-guided and topography-guided), allowing performance of a customized treatment if needed. Its use in keratoconus has been described since the 2000s, alone or in combination with other procedures. For example, the combination of photoablation and corneal cross linking, a technique that increases corneal rigidity and in so doing can slow or even stop the progression of keratoconus, proved its efficacy and safety in many studies, and various protocols have been described. A triple procedure, including intracorneal ring segments, excimer laser and cross linking, has also given some very promising results in progressive keratoconus, providing a significative improvement in visual acuity and topographic data. The combination of excimer laser and intraocular lenses remains a poorly explored lead that might provide some satisfactory results. The objective of this review is to summarize the recent data on excimer laser in keratoconus management.

Interventions to slow progression of myopia in children

BACKGROUND

Nearsightedness (myopia) causes blurry vision when one is looking at distant objects. Interventions to slow the progression of myopia in children include multifocal spectacles, contact lenses, and pharmaceutical agents.

OBJECTIVES

To assess the effects of interventions, including spectacles, contact lenses, and pharmaceutical agents in slowing myopia progression in children.

SEARCH METHODS

We searched CENTRAL; Ovid MEDLINE; Embase.com; PubMed; the LILACS Database; and two trial registrations up to February 2018. A top up search was done in February 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs). We excluded studies when most participants were older than 18 years at baseline. We also excluded studies when participants had less than -0.25 diopters (D) spherical equivalent myopia.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods.

MAIN RESULTS

We included 41 studies (6772 participants). Twenty-one studies contributed data to at least one meta-analysis. Interventions included spectacles, contact lenses, pharmaceutical agents, and combination treatments. Most studies were conducted in Asia or in the United States. Except one, all studies included children 18 years or younger. Many studies were at high risk of performance and attrition bias. Spectacle lenses: undercorrection of myopia increased myopia progression slightly in two studies; children whose vision was undercorrected progressed on average -0.15 D (95% confidence interval [CI] -0.29 to 0.00; n = 142; low-certainty evidence) more than those wearing fully corrected single vision lenses (SVLs). In one study, axial length increased 0.05 mm (95% CI -0.01 to 0.11) more in the undercorrected group than in the fully corrected group (n = 94; low-certainty evidence). Multifocal lenses (bifocal spectacles or progressive addition lenses) yielded small effect in slowing myopia progression; children wearing multifocal lenses progressed on average 0.14 D (95% CI 0.08 to 0.21; n = 1463; moderate-certainty evidence) less than children wearing SVLs. In four studies, axial elongation was less for multifocal lens wearers than for SVL wearers (-0.06 mm, 95% CI -0.09 to -0.04; n = 896; moderate-certainty evidence). Three studies evaluating different peripheral plus spectacle lenses versus SVLs reported inconsistent results for refractive error and axial length outcomes (n = 597; low-certainty evidence). Contact lenses: there may be little or no difference between vision of children wearing bifocal soft contact lenses (SCLs) and children wearing single vision SCLs (mean difference (MD) 0.20D, 95% CI -0.06 to 0.47; n = 300; low-certainty evidence). Axial elongation was less for bifocal SCL wearers than for single vision SCL wearers (MD -0.11 mm, 95% CI -0.14 to -0.08; n = 300; low-certainty evidence). Two studies investigating rigid gas permeable contact lenses (RGPCLs) showed inconsistent results in myopia progression; these two studies also found no evidence of difference in axial elongation (MD 0.02mm, 95% CI -0.05 to 0.10; n = 415; very low-certainty evidence). Orthokeratology contact lenses were more effective than SVLs in slowing axial elongation (MD -0.28 mm, 95% CI -0.38 to -0.19; n = 106; moderate-certainty evidence). Two studies comparing spherical aberration SCLs with single vision SCLs reported no difference in myopia progression nor in axial length (n = 209; low-certainty evidence). Pharmaceutical agents: at one year, children receiving atropine eye drops (3 studies; n = 629), pirenzepine gel (2 studies; n = 326), or cyclopentolate eye drops (1 study; n = 64) showed significantly less myopic progression compared with children receiving placebo: MD 1.00 D (95% CI 0.93 to 1.07), 0.31 D (95% CI 0.17 to 0.44), and 0.34 (95% CI 0.08 to 0.60), respectively (moderate-certainty evidence). Axial elongation was less for children treated with atropine (MD -0.35 mm, 95% CI -0.38 to -0.31; n = 502) and pirenzepine (MD -0.13 mm, 95% CI -0.14 to -0.12; n = 326) than for those treated with placebo (moderate-certainty evidence) in two studies. Another study showed favorable results for three different doses of atropine eye drops compared with tropicamide eye drops (MD 0.78 D, 95% CI 0.49 to 1.07 for 0.1% atropine; MD 0.81 D, 95% CI 0.57 to 1.05 for 0.25% atropine; and MD 1.01 D, 95% CI 0.74 to 1.28 for 0.5% atropine; n = 196; low-certainty evidence) but did not report axial length. Systemic 7-methylxanthine had little to no effect on myopic progression (MD 0.07 D, 95% CI -0.09 to 0.24) nor on axial elongation (MD -0.03 mm, 95% CI -0.10 to 0.03) compared with placebo in one study (n = 77; moderate-certainty evidence). One study did not find slowed myopia progression when comparing timolol eye drops with no drops (MD -0.05 D, 95% CI -0.21 to 0.11; n = 95; low-certainty evidence). Combinations of interventions: two studies found that children treated with atropine plus multifocal spectacles progressed 0.78 D (95% CI 0.54 to 1.02) less than children treated with placebo plus SVLs (n = 191; moderate-certainty evidence). One study reported -0.37 mm (95% CI -0.47 to -0.27) axial elongation for atropine and multifocal spectacles when compared with placebo plus SVLs (n = 127; moderate-certainty evidence). Compared with children treated with cyclopentolate plus SVLs, those treated with atropine plus multifocal spectacles progressed 0.36 D less (95% CI 0.11 to 0.61; n = 64; moderate-certainty evidence). Bifocal spectacles showed small or negligible effect compared with SVLs plus timolol drops in one study (MD 0.19 D, 95% CI 0.06 to 0.32; n = 97; moderate-certainty evidence). One study comparing tropicamide plus bifocal spectacles versus SVLs reported no statistically significant differences between groups without quantitative results. No serious adverse events were reported across all interventions. Participants receiving antimuscarinic topical medications were more likely to experience accommodation difficulties (Risk Ratio [RR] 9.05, 95% CI 4.09 to 20.01) and papillae and follicles (RR 3.22, 95% CI 2.11 to 4.90) than participants receiving placebo (n=387; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Antimuscarinic topical medication is effective in slowing myopia progression in children. Multifocal lenses, either spectacles or contact lenses, may also confer a small benefit. Orthokeratology contact lenses, although not intended to modify refractive error, were more effective than SVLs in slowing axial elongation. We found only low or very low-certainty evidence to support RGPCLs and sperical aberration SCLs.

Main Complications of Photorefractive Keratectomy and their Management

Photorefractive keratectomy (PRK) was the first surface ablation procedure introduced for the treatment of refractive errors and has been proven to be effective and safe. In some cases, however, the patient may not be totally satisfied with the final result and retreatment may be necessary. We performed a literature review to describe the main conditions that may arise following PRK that may require retreatment and new promising techniques to allow customized and effective treatments for patients. There is currently no gold standard for retreatment of residual refractive error after PRK. The surgeon must take into account the patient's history and type of problem when choosing the most appropriate technique. LASIK and PRK are the main options. Haze can be treated with good results with phototherapeutic keratectomy and mytomicin C. High order aberrations and decentration may be addressed with topographically-guided excimer photoablation or with wavefront-guided PRK.

Femtosecond-assisted laser in situ keratomileusis for high myopia correction: Long-term follow-up outcomes

OBJECTIVE

Report the outcomes of laser in situ keratomileusis (LASIK) for high myopia correction after long-term follow-up.

METHODS

Retrospective, consecutive, clinical study including 70 eyes that underwent LASIK using a 500 Hertz (Hz) repetition rate excimer laser and femtosecond technology for flap creation. Visual, refractive, corneal aberrations, and correlation among the variables were evaluated during 3 years. In addition, 34 eyes were followed during 5 years.

RESULTS

Significant improvement of 17 logMAR lines was observed in uncorrected vision at 5 years (p < 0.01). This was consistent with spherical equivalent reduction that came from mean preoperative -7.79 diopters (D) to 5 years postoperative -0.24 D (p < 0.01). Significant induction of primary spherical aberration and coma aberration was also found (p < 0.01) at 3 months with levels of 0.61 µm and 0.47 µm, respectively, with no further changes at 5 years (p > 0.05). Pearson correlation showed that the amount of high-order aberrations at 3 months postoperativeley was significantly correlated with the changes in the keratometry throughout the 5 years (delta K) (R2 0.242 p = 0.05). Finally, preoperative corneal asphericity showed an inverse correlation with the delta K (R2 -308 p = 0.01).

CONCLUSIONS

Results from this study suggests that LASIK for high myopia correction using 500 Hz repetition rate excimer laser provides stable visual, refractive and aberrometric results after 5 years of follow-up. A more prolate cornea and the amount of higher-order aberrations induced after LASIK are factors that negatively impact in the long-term stability of the procedure.

Changes in the anterior cornea during the early stages of severe myopia prior to and following LASIK, as detected by confocal microscopy

The present study aimed to assess the microscopic changes of the epithelium and Bowman's layer under confocal microscopy during the early stages of severe myopia following laser in situ keratomileusis (LASIK). The study comprised 54 patients (54 eyes) with severe myopia and 65 patients (65 eyes) with low and moderate myopia, who underwent LASIK surgery at Tianjin Medical University Eye Hospital (Tianjin, China). In all patients, the epithelium, Bowman's layer and anterior stroma were examined prior to and 1, 7, 30, 90 and 180 days after the surgery, using in vivo confocal microscopy. Six (6 eyes) of the 54 patients with severe myopia (11.1%) exhibited corneal epithelial changes following the surgery, as examined by a slit lamp. Three patients (3 eyes) exhibited epithelial changes under confocal microscopy. In 40 eyes (74.1%) with severe myopia, brown yellow changes were observed at the epithelial layer and in the central part of the cornea 6 months after the surgery; the same was observed in 35 eyes (53.8%) with low and moderate myopia. Microfolds in the Bowman's layer of eyes with severe myopia were detected in 48 eyes (88.9%), and in 54 eyes (100.0%) in the anterior stroma following LASIK, whereas microfolds were observed in 51 (78.5%) and 65 eyes (100%), respectively, in patients with low to moderate myopia. In the severe myopia group, 54 eyes (100%) exhibited nerve fibers below the epithelium that were detectable 1 day post-surgery; in 16 eyes (29.6%), 1 or 2 sub-epithelial nerve fibers were detected 7 days after the surgery, and in 24 eyes (44.4%), 1 or 2 sub-epithelial nerve fibers were observed 6 months after the surgery. In eyes with low and moderate myopia, the figures were 100, 38.5 and 64.8%, respectively. The nerves of neither group returned to the pre-operative level. In conclusion, neurotrophic epitheliopathy, microfolds in Bowman's layer and anterior stroma were detected in the present patients with severe myopia of the cornea following LASIK, and the recovery of nerve fibers required an extended period of time.

The quality of systematic reviews about interventions for refractive error can be improved: a review of systematic reviews

BACKGROUND

Systematic reviews should inform American Academy of Ophthalmology (AAO) Preferred Practice Pattern® (PPP) guidelines. The quality of systematic reviews related to the forthcoming Preferred Practice Pattern® guideline (PPP) Refractive Errors & Refractive Surgery is unknown. We sought to identify reliable systematic reviews to assist the AAO Refractive Errors & Refractive Surgery PPP.

METHODS

Systematic reviews were eligible if they evaluated the effectiveness or safety of interventions included in the 2012 PPP Refractive Errors & Refractive Surgery. To identify potentially eligible systematic reviews, we searched the Cochrane Eyes and Vision United States Satellite database of systematic reviews. Two authors identified eligible reviews and abstracted information about the characteristics and quality of the reviews independently using the Systematic Review Data Repository. We classified systematic reviews as "reliable" when they (1) defined criteria for the selection of studies, (2) conducted comprehensive literature searches for eligible studies, (3) assessed the methodological quality (risk of bias) of the included studies, (4) used appropriate methods for meta-analyses (which we assessed only when meta-analyses were reported), (5) presented conclusions that were supported by the evidence provided in the review.

RESULTS

We identified 124 systematic reviews related to refractive error; 39 met our eligibility criteria, of which we classified 11 to be reliable. Systematic reviews classified as unreliable did not define the criteria for selecting studies (5; 13%), did not assess methodological rigor (10; 26%), did not conduct comprehensive searches (17; 44%), or used inappropriate quantitative methods (3; 8%). The 11 reliable reviews were published between 2002 and 2016. They included 0 to 23 studies (median = 9) and analyzed 0 to 4696 participants (median = 666). Seven reliable reviews (64%) assessed surgical interventions.

CONCLUSIONS

Most systematic reviews of interventions for refractive error are low methodological quality. Following widely accepted guidance, such as Cochrane or Institute of Medicine standards for conducting systematic reviews, would contribute to improved patient care and inform future research.

Dry eye and corneal sensitivity after small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis: a Meta-analysis

AIM

To assess the corneal sensitivity and the incidences of dry eye after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK).

METHODS

The Meta-analysis was performed using RevMan 5.3. We searched on PubMed from inception to March 2016. Summary weighted mean difference (WMD) and 95% confidence intervals (CIs) were used to analyze the datum. Random-effects or fixed-effects models were chosen up to between-study heterogeneity. The main outcomes were composed of the Ocular Surface Disease Index (OSDI) scores, tear film break-up time (TBUT), Schirmer Test and corneal sensitivity.

RESULTS

Eight eligible studies including 772 eyes (386 in SMILE group and 386 in FS-LASIK group) were identified. The parameters have no significiant difference heterogeneity between SMILE and FS-LASIK group preoperatively. There were significant differences between the two groups in OSDI scores at one and three months postoperatively, in TBUT at one and three months postoperatively, in corneal sensitivity at one week, about one month and three months postoperatively. However, there was no significant difference observed in Schirmer Test at the follow-up periods.

CONCLUSION

Compare to FS-LASIK, dry eye and the corneal sensitivity recover better in the SMILE group, in first three months after the surgery.

Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia

BACKGROUND

Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review.

OBJECTIVES

To assess the effects of LASEK versus LASIK for correcting myopia.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials.

SELECTION CRITERIA

We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were assigned randomly to receive either LASEK or LASIK in one or both eyes. We also included paired-eye studies in which investigators randomly selected which of the participant's eyes would receive LASEK or LASIK and assigned the other eye to the other procedure. Participants were men or women between the ages of 18 and 60 years with myopia up to 12 diopters (D) and/or myopic astigmatism of severity up to 3 D, who did not have a history of prior refractive surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all reports and assessed the risk of bias in trials included in this review. We extracted data and summarized findings using risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes. In the absence of clinical and methodological heterogeneity across trials, we used a random-effects model to calculate summary effect estimates. We used a fixed-effect model when including fewer than three trials in a meta-analysis. When clinical, methodological, or statistical heterogeneity was observed across trials, we reported our findings in a narrative synthesis.

MAIN RESULTS

We identified four eligible trials with 538 eyes of 392 participants for the review, but only three trials (154 participants) provided outcome data for analysis. We found no ongoing trials. Two of four trials were from China, one trial was from Turkey, and the location of one trial was not reported. The risk of bias for most domains was unclear due to poor reporting of trial methods; no trial had a protocol or trial registry record. Three trials enrolled participants with mild to moderate myopia (less than -6.50 D); one trial included only participants with severe myopia (more than -6.00 D).The evidence showed uncertainty in whether there is a difference between LASEK and LASIK in uncorrected visual acuity (UCVA) at 12 months, the primary outcome in our review. The RR and 95% confidence interval (CI) at 12 months after surgery was 0.96 (95% CI 0.82 to 1.13) for UCVA of 20/20 or better and 0.90 (95% CI 0.67 to 1.21) for UCVA of 20/40 or better based on data from one trial with 57 eyes (very low-certainty evidence). People receiving LASEK were less likely to achieve a refractive error within 0.5 diopters of the target at 12 months follow-up (RR 0.69, 95% CI 0.48 to 0.99; 57 eyes; very low-certainty evidence). One trial reported mild corneal haze at six months in one eye in the LASEK group and none in the LASIK group (RR 2.11, 95% CI 0.57 to 7.82; 76 eyes; very low-certainty evidence). None of the included trials reported postoperative pain score or loss of visual acuity, spherical equivalent of the refractive error, or quality of life at 12 months.Refractive regression, an adverse event, was reported only in the LASEK group (8 of 37 eyes) compared with none of 39 eyes in the LASIK group in one trial (low-certainty evidence). Other adverse events, such as corneal flap striae and refractive over-correction, were reported only in the LASIK group (5 of 39 eyes) compared with none of 37 eyes in the LASEK group in one trial (low-certainty evidence).

AUTHORS' CONCLUSIONS

Overall, from the available RCTs, there is uncertainty in how LASEK compares with LASIK in achieving better refractive and visual results in mildly to moderately myopic participants. Large, well-designed RCTs would be required to estimate the magnitude of any difference in efficacy or adverse effects between LASEK and LASIK for treating myopia or myopic astigmatism.

Comparison of Higher Order Aberrations after Wavefront-guided LASIK and PRK: One Year Follow-Up Results

PURPOSE

To evaluate the changes and predictability of higher order aberrations (HOAs) after personalized laser in situ keratomileusis (LASIK) and personalized photorefractive keratectomy (PRK) for simple myopia and compound myopic astigmatism.

METHODS

In this prospective cross-sectional study, 100 eyes were included. A total of 50 eyes underwent personalized LASIK and 50 eyes underwent personalized PRK. Preoperative and postoperative wavefront data were compared between the two groups. The influential factors and predictability of HOAs were also assessed.

RESULT

Total HOA increased in the amount of 0.01 ± 0.14 μm for the 5 mm pupil (P = 0.55) and 0.08 ± 0.22 μm for the 6 mm pupil (P = 0.02) after PRK; however after LASIK the corresponding values for the 5 and 6 mm pupil sizes were 0.05 ± 0.12 and 0.15 ± 0.18 μm, respectively (P < 0. 001). Mean changes were not significantly different between the PRK and LASIK groups for both 5 and 6 mm pupil sizes (P = 0.21 and P = 0.13, respectively). Spherical aberration increased following LASIK more than following PRK (P < 0.001). Changes in the root mean square (RMS) of total HOA had a statistically significant negative correlation (P < 0.001) with its preoperative value. HOA and spherical aberration reduced in majority of eyes when the preoperative spherical equivalent refraction was low.

CONCLUSION

For the 6mm pupil size, the total HOA increased following both personalized PRK and LASIK with no significant difference between the two groups. Change of the total HOA RMS was influenced by the preoperative values. The known influencing factors could predict nearly 50% of the changes in total HOA.

Cochrane systematic reviews and co-publication: dissemination of evidence on interventions for ophthalmic conditions

BACKGROUND

Systematic reviews of interventions provide a summary of the evidence available on intervention effectiveness and harm. Cochrane systematic reviews (CSRs) have been published electronically in the Cochrane Database of Systematic Reviews (CDSR) since 1994, and co-publication (publication of a Cochrane review in another journal) has been allowed since that time, as long as the co-publishing journal has agreed to the arrangement. Although standards for co-publication were established in 2008, the frequency of co-publication and adherence to the standards have remained largely unexamined. Our objective was to examine the frequency of co-publication of Cochrane Eyes and Vision Group (CEVG) reviews, adherence to the co-publication policy, the relative numbers of citations of the two modes of publishing, and differences in times cited in CSRs with and without a co-publication.

METHODS

We identified all CEVG reviews published by May 30, 2014 in The Cochrane Library. Using keywords from the title, author names, and "Cochrane Eyes and Vision Group", we searched Google Scholar, Web of Science, Scopus, and PubMed databases to identify possible co-publications. We also emailed contact authors of all identified CEVG reviews to ask them whether they had published their CSR elsewhere. We compared each co-publication to the corresponding CEVG review for adherence to the Cochrane Policy Manual (dated June 10, 2014). We recorded the number of times each CEVG review and each co-publication had been cited by others according to Google Scholar, Web of Science, and Scopus, as of June 11, 2014.

RESULTS

We identified 117 CEVG reviews;19 had been co-published in 22 articles. Adherence to Cochrane policy on co-publication was moderate, with all authors complying with at least one of four requirements we addressed. Co-publications were cited more often than the corresponding CEVG reviews; CEVG reviews with at least one co-publication were cited approximately twice as often as CEVG reviews without a co-publication. The number of citations varied considerably depending on whether the CEVG review had a co-publication or not.

CONCLUSIONS

The findings support encouraging co-publication while maintaining the primacy of the Cochrane systematic review. Support for co-publication may be tempered by other factors such as the possibility that CEVG reviews with a co-publication covered more clinically important and timely topics than those without a co-publication. Assuming that citations are a valid measure of dissemination effectiveness, the 15-year CEVG experience with co-publication of systematic reviews suggests that Cochrane authors should be encouraged to co-publish in traditional medical journals.

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.

One-step transepithelial topography-guided ablation in the treatment of myopic astigmatism

PURPOSE

To evaluate one-step topography-guided transepithelial ablation in the treatment of low to moderate myopic astigmatism using a 1KHz excimer laser.

METHODS

Retrospective study of 117 consecutive eyes available for evaluation 12 months after surgery. Pre- and post-operative visual and refractive data as well as post-operative pain and haze were analyzed. A novel technique integrating custom refractive- and epithelial- ablation in a single uninterrupted procedure was used.

RESULTS

The mean pre-operative spherical equivalent (SE) and the mean cylinder were: -3.22 diopters (D) ±1.54 (SD) (range -0.63 to -7.25 D) and -0.77 D ±0.65 (range 0 to -4.50 D), respectively. At 12 months after surgery: no eyes lost ≥2 lines of corrected distant visual acuity (CDVA). Safety and efficacy indexes were 1.27 and 1.09, respectively. Uncorrected distant visual acuity (UDVA) was ≥20/20 in 96.6% of the eyes. Manifest refraction spherical equivalent was within ±0.5 D of the desired refraction in 93.2% of the eyes. Average root mean square (RMS) wavefront error measured at central 6 mm, increased from 0.38 pre-operatively to 0.47 µm post-operatively. Refractive stability was achieved and sustained 1 month after surgery. No visually significant haze was registered during the observation period. Post-operative pain was reported in 4.5% of patients.

CONCLUSIONS

One-step transepithelial topography-guided treatment for low to moderate myopia and astigmatism performed with a 1 KHz laser, provided safe, effective, predictable and stable results with low pain and no visually significant haze.

Risk factors and visual results in cases of LASIK flap repositioning due to folds or dislocation: case series and literature review

The presence of a corneal flap is a hallmark of laser in situ keratomileusis (LASIK), which offers advantages in terms of speed of visual recovery; however, it also carries the risk of postoperative flap displacement. We conducted a retrospective review of all consecutive eyes on which LASIK was performed by one single surgeon at an ophthalmological institute in Colombia between May 2005 and January 2011, looking for eyes that required flap repositioning. Demographic data, preoperative refraction, hinge position, and visual outcomes following flap repositioning were evaluated. A literature review on the subject was also conducted. We found 37 eyes on which flap repositioning was performed-12 eyes (32.4 %) with subluxation and 25 eyes (67.6 %) with folds; 21 eyes (56.8 %) had a temporal hinge and 16 eyes (43.2 %) had a superior hinge. With regard to the total number of eyes on which LASIK was performed (2,595), the overall incidence was 1.4 %. Sixteen out of 2,093 eyes (0.8 %) with a superior hinge and 21 out of 502 eyes (4.2 %) with a temporal hinge had flap-related postoperative complications (p < 0.00). A final best-corrected visual acuity (BCVA) between 20/20 and 20/25 was found in 75.7 % and a final BCVA between 20/30 and 20/40 was found in 21.6 %. Only one eye had less than 20/40 (previous amblyopia). From the eight eyes with a BCVA between 20/30 and 20/40, three had residual microstriae and one had corneal haze. Six eyes (16.2 %) lost two or more lines of BCVA. Flap subluxation or folds requiring flap repositioning were significantly more frequent when a temporal hinge was used.

Interventions to slow progression of myopia in children

BACKGROUND

Nearsightedness (myopia) causes blurry vision when looking at distant objects. Highly nearsighted people are at greater risk of several vision-threatening problems such as retinal detachments, choroidal atrophy, cataracts and glaucoma. Interventions that have been explored to slow the progression of myopia include bifocal spectacles, cycloplegic drops, intraocular pressure-lowering drugs, muscarinic receptor antagonists and contact lenses. The purpose of this review was to systematically assess the effectiveness of strategies to control progression of myopia in children.

OBJECTIVES

To assess the effects of several types of interventions, including eye drops, undercorrection of nearsightedness, multifocal spectacles and contact lenses, on the progression of nearsightedness in myopic children younger than 18 years. We compared the interventions of interest with each other, to single vision lenses (SVLs) (spectacles), placebo or no treatment.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 10), MEDLINE (January 1950 to October 2011), EMBASE (January 1980 to October 2011), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to October 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) and ClinicalTrials.gov (http://clinicaltrials.gov). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 11 October 2011. We also searched the reference lists and Science Citation Index for additional, potentially relevant studies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in which participants were treated with spectacles, contact lenses or pharmaceutical agents for the purpose of controlling progression of myopia. We excluded trials where participants were older than 18 years at baseline or participants had less than -0.25 diopters (D) spherical equivalent myopia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias for each included study. When possible, we analyzed data with the inverse variance method using a fixed-effect or random-effects model, depending on the number of studies and amount of heterogeneity detected.

MAIN RESULTS

We included 23 studies (4696 total participants) in this review, with 17 of these studies included in quantitative analysis. Since we only included RCTs in the review, the studies were generally at low risk of bias for selection bias. Undercorrection of myopia was found to increase myopia progression slightly in two studies; children who were undercorrected progressed on average 0.15 D (95% confidence interval (CI) -0.29 to 0.00) more than the fully corrected SVLs wearers at one year. Rigid gas permeable contact lenses (RGPCLs) were found to have no evidence of effect on myopic eye growth in two studies (no meta-analysis due to heterogeneity between studies). Progressive addition lenses (PALs), reported in four studies, and bifocal spectacles, reported in four studies, were found to yield a small slowing of myopia progression. For seven studies with quantitative data at one year, children wearing multifocal lenses, either PALs or bifocals, progressed on average 0.16 D (95% CI 0.07 to 0.25) less than children wearing SVLs. The largest positive effects for slowing myopia progression were exhibited by anti-muscarinic medications. At one year, children receiving pirenzepine gel (two studies), cyclopentolate eye drops (one study), or atropine eye drops (two studies) showed significantly less myopic progression compared with children receiving placebo (mean differences (MD) 0.31 (95% CI 0.17 to 0.44), 0.34 (95% CI 0.08 to 0.60), and 0.80 (95% CI 0.70 to 0.90), respectively).

AUTHORS' CONCLUSIONS

The most likely effective treatment to slow myopia progression thus far is anti-muscarinic topical medication. However, side effects of these medications include light sensitivity and near blur. Also, they are not yet commercially available, so their use is limited and not practical. Further information is required for other methods of myopia control, such as the use of corneal reshaping contact lenses or bifocal soft contact lenses (BSCLs) with a distance center are promising, but currently no published randomized clinical trials exist.

Trends in refractive surgery at an academic center: 2007-2009

BACKGROUND

The United States officially entered a recession in December 2007, and it officially exited the recession in December 2009, according to the National Bureau of Economic Research. Since the economy may affect not only the volume of excimer laser refractive surgery, but also the clinical characteristics of patients undergoing surgery, our goal was to compare the characteristics of patients completing excimer laser refractive surgery and the types of procedures performed in the summer quarter in 2007 and the same quarter in 2009 at an academic center. A secondary goal was to determine whether the volume of astigmatism- or presbyopia-correcting intraocular lenses (IOLs) has concurrently changed because like laser refractive surgery, these "premium" IOLs involve out-of-pocket costs for patients.

METHODS

Retrospective case series. Medical records were reviewed for all patients completing surgery at the Wilmer Laser Vision Center in the summer quarter of 2007 and the summer quarter of 2009. Outcome measures were the proportions of treated refractive errors, the proportion of photorefractive keratectomy (PRK) vs. laser-assisted in-situ keratomileusis (LASIK), and the mean age of patients in each quarter. Chi-square test was used to compare the proportions of treated refractive errors and the proportions of procedures; two-tailed t-test to compare the mean age of patients; and two-tailed z-test to compare proportions of grouped refractive errors in 2007 vs. 2009; alpha = 0.05 for all tests. Refractive errors were grouped by the spherical equivalent of the manifest refraction and were considered "low myopia" for 6 diopters (D) of myopia or less, "high myopia" for more than 6 D, and "hyperopia" for any hyperopia. Billing data were reviewed to obtain the volume of premium IOLs.

RESULTS

Volume of laser refractive procedures decreased by at least 30%. The distribution of proportions of treated refractive errors did not change (p = 0.10). The proportion of high myopes, however, decreased (p = 0.05). The proportions of types of procedure changed, with an increase in the proportion of PRK between 2007 and 2009 (p = 0.02). The mean age of patients did not change [42.4 ± 14.4 (standard deviation) years in 2007 vs. 39.6 ± 14.5 years in 2009; p = 0.4]. Astigmatism-correcting IOL and presbyopia-correcting IOL volumes increased 15-fold and three-fold, respectively, between 2007 and 2009.

CONCLUSIONS

Volume of excimer laser refractive surgery decreased by at least 30% between 2007 and 2009. No significant change in mean age or in the distribution of refractive error was seen, although the proportion of high myopes decreased between summer quarters of 2007 and 2009. PRK gained as a proportion of total cases. Premium IOL volume increased, but still comprised a very small proportion of total IOL volume.

Evaluation of the retinal nerve fiber layer measurements, after photorefractive keratectomy and laser in situ keratomileusis, using scanning laser polarimetry (GDX VCC)

BACKGROUND

To evaluate the impact of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK), on retinal nerve fiber layer (RNFL) measurements, by means of scanning laser polarimetry (SLP) GDx VCC (with variable corneal compensation).

METHODS

Two groups of 119 myopic patients each were treated by PRK and LASIK respectively; one eye of each patient was randomly selected for the study. RNFL measurements (around the entire calculation circle) was performed in all eyes 1 day before and 1, 3, 6 and 12 months after treatment by using SLP GDx VCC. Corneal compensation was performed in all eyes preoperatively, and in every examination step postoperatively, in order to neutralize the new corneal birefringence.

RESULTS

No statistical differences were found between the PRK and LASIK groups, in all preoperative and postoperative RNFL measurements. Only the p values for CCT and mean K-readings preoperatively were statistically significant.

CONCLUSIONS

PRK and LASIK do not seem to influence the RNFL measurements at 1st, 3rd, 6th and 12th postoperative months when measured with SLP GDx VCC. The corneal compensation reset is necessary in every step of the examination in order to have reproducible results.