Laser In Situ Keratomileusis Eyes Research Articles

LASIK Videos on TikTok: A Content Analysis of the Top 100 Videos.

Social media has increasingly become a prominent source of health information. Platforms like TikTok that allow for videos to reach millions of viewers have become among the most common platforms to share and receive health information. Laser in situ keratomileusis (LASIK) videos and patients' experiences are commonly discussed on social media. The quality of these videos remains to be assessed. The aim of this study is to evaluate the content, quality, and reach of the top 100 videos related to LASIK eye surgery on TikTok. Video quality was assessed using the DISCERN, JAMA, and GQS instruments which have all been proven to be both reliable and valid. 100 videos were included in the study. Results showed that the videos have an immense reach with a total view count of 245 million views and 21.9 million likes. Two thirds of the videos were posted by personal accounts as compared ophthalmologists that only constituted 26% of the content. Healthcare professionals produced higher quality videos compared to nonhealthcare professionals (p < 0.0001) although there was no significant difference in video duration (p=0.18). Increased duration, view count, comments, shares, saves, and views/day were all associated with increased DISCERN score and quality of the videos. Educational videos were of higher quality compared to entertainment videos, and videos outlining the procedure details had the highest quality score. LASIK videos on TikTok have established a wide reach, whereby viewers are highly interacting and viewing these videos. It appeared that viewers interacted more with the higher quality videos. Ophthalmologists approximately only contributed to a quarter of the videos analyzed in this study. This highlights the need for ophthalmologists to establish a presence on TikTok and produce high quality videos.

Comparison of refractive and visual acuity results after Contoura® Vision topography-guided LASIK planned with the Phorcides Analytic Engine to results after wavefront-optimized LASIK in eyes with oblique astigmatism.

To compare visual acuity and refractive results between topography-guided laser in situ keratomileusis (LASIK) planned with the Phorcides Analytic Engine (PAE) to results after wavefront-optimized (WFO) LASIK in subjects with preoperative oblique astigmatism in their manifest refraction. This was a retrospective chart review of clinical results from eyes treated with topography-guided LASIK planned with PAE compared to eyes treated with WFO LASIK using the same Wavelight® excimer laser system. All included subjects had preoperative oblique astigmatism. Residual refractive error and visual acuity (uncorrected and corrected) were the measures of interest, at the visit closest to 90 days postoperative. A matched data set from 100 WFO and 97 PAE eyes was extracted from clinical records. At the postoperative visit the PAE group showed lower residual refractive cylinder (p = 0.04), uncorrected distance visual acuity (UDVA) (-0.06 PAE vs. -0.02 WFO, p < 0.01) and distance corrected visual acuity (CDVA) (p < 0.01). The percentage of eyes with a mean refraction spherical equivalent (MRSE) magnitude within 0.25 D and 0.50 D of plano was statistically significantly higher in the PAE group (p = 0.04 and 0.01, respectively). A statistically significantly higher percentage of eyes in the PAE group had UDVA better than or equal to -0.10 logMAR (20/16 Snellen, 36% vs 22%, p = 0.04). More eyes gained CDVA after surgery in the PAE group (53% vs 32%, p < 0.01). There were five enhancements in the WFO group versus none in the PAE group, a statistically significant difference (p = 0.03). Visual acuity and refractive outcomes after LASIK using PAE in eyes with oblique astigmatism in their preoperative refraction were statistically significantly better than those obtained when WFO treatment was used. The number of refractive outliers and the number of retreatments were also significantly lower with PAE treatment.

Corneal Epithelium Thickness and Refractive Changes After Myopic Laser Corneal Refractive Surgery

To evaluate the postoperative changes in corneal epithelium thickness and refractive power after femtosecond laser-assisted laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) for myopia correction using anterior segment optical coherence tomography (OCT) with an integrated Placido disc topographer. The VisuMax 500-kHz femtosecond laser (Carl Zeiss Meditec AG) and Amaris 750 excimer laser (SCHWIND eye-tech-solutions) were used. Central, paracentral, and 6-mm epithelial thickness values were obtained, and the change in the value of epithelial thickness was calculated. Changes in the refractive power of the epithelium were also evaluated. The repeatability of this new measurement was also analyzed using the intraclass correlation (ICC). The total follow-up period was 6 months. A total of 77 LASIK eyes were matched with 77 SMILE eyes. Mean spherical equivalent was -3.92 ± 1.67 diopters (D) for LASIK versus -4.02 ± 1.63 D for SMILE (P = .356). Epithelial thickness parameters significantly and equally thickened in both types of surgery. The change in the value of epithelial thickness was positively correlated with spherical aberration. Analysis of the refractive power of the corneal epithelial layer (ICC > 0.70) showed a tendency for the postoperative myopization of the refractive component of this layer (-0.11 D for SMILE and -0.53 D for LASIK at 3 mm) and an increase in its cylinder and aberrometry. Increasing postoperative spherical aberration and epithelial thickness increased myopization of the epithelial refractive sphere (P < .05). Corneal epithelium thickens similarly after LASIK and SMILE, being slightly higher after SMILE. This correlates with the induced spherical aberration. Corneal epithelium thickening induces myopization of its refractive power, which accounts for a slight regression of the net refractive power change on the treated cornea. [J Refract Surg. 2022;38(9):602-608.].

Effect of photorefractive keratectomy versus laser in situ keratomileusis on corneal hysteresis in moderate myopic eyes

IntroductionAblation procedures used for vision correction such as photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) flap creation produce massive changes within the corneal structure and biomechanical properties. These changes are due to thinning of the central cornea and disruption of continuity of the collagen lamellae. Several approaches to assessment of the biomechanical properties have been proposed. Refractive photoablation procedures that decrease corneal hysteresis (CH) and corneal resistance factor (CRF) have been shown by several studies; therefore, here in our study we are going to discuss the effect of PRK versus LASIK on the corneal biomechanics and stability over time.AimTo compare the postoperative biomechanical properties of the cornea after PRK and after LASIK in eyes with moderate myopia.Patients and methodsThe study is 'prospective, controlled, and randomized.' In all, 40 eyes with moderate myopia (−2.0 to − 5.0 D) underwent refractive correction of myopia; 20 of them (group A) were enrolled for PRK while the other 20 of them (group B) were enrolled for LASIK surgery. CH and CRF were measured with an ocular response analyzer preoperatively and 1and 3 months postoperatively. All eyes were subjected to corneal topography preoperatively and 1 and 3 months postoperatively ocular response analyzer was used preoperatively and 1 and 3 months postoperatively.ResultsAll patients were followed up postoperatively at 1 and 3 months. The CH and CRF were measured in both groups preoperatively and postoperatively. In group A, the mean preoperative CH was 10.7 ± 0.4 (range: 10–11.1) and CRF was 10.2 ± 0.11 (range: 10.1–10.5), whereas in group B it was 10.57 ± 0.38 (range: 10–11.2) and the CRF was 10.21 ± 0.1 (range: 10–10.5), respectively, with no significant difference (P = 0.43 and 0.25, respectively).After 1 month, CH and CRF were 8.4 ± 0.27 (range: 7.9–9.1) and 8.2 ± 0.23 (range: 7.8–8.6) in group A and 8.3 ± 0.25 (range: 8.0–9.0) and 8.17 ± 0.19 (range: 7.9–8.5) in group B, respectively, with no significant difference (P = 0.28 and 0.45, respectively). At 3 months, CH and CRF were 8.6 ± 0.28 (range: 8.1–9.2) and 8.3 ± 0.21 (range: 7.8–8.6) in group A and 8.55 ± 0.26 (range: 8.2–9.1) and 8.28 ± 0.18 (range: 7.9–8.6) in group B, respectively, with no significant difference (P = 0.56 and 0.32, respectively). The corneal biomechanical parameters decreased after both PRK and LASIK procedures. The corneal biomechanical parameters decreased after both PRK and LASIK procedures. The postoperative measurements of CH and CRF at 3 months were lower than the preoperative values in both groups with a significant amount (P < 0.001).ConclusionBoth PRK and LASIK substantially weaken the biomechanical strength of the cornea, the greater the amount of myopic correction, the more the change in corneal biomechanics.

LASIK versus PRK for high astigmatism.

To compare the refractive outcomes of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for myopic astigmatism of 3 diopters (D) or more. Retrospective matched comparative study. This study include consecutive myopic patients (SE 0 to -10 D) undergoing LASIK or PRK between 2007 and 2016 with astigmatism of 3 to 6 D, and postoperative follow-up of at least 30days for LASIK and 60days for PRK, compared outcomes of LASIK and PRK eyes. The LASIK and PRK groups comprised 175 eyes of 175 patients each, with median follow-up of 39 and 139days, respectively (P < 0.001). Mean preoperative manifest astigmatism was -3.35 ± 0.46 and -3.42 ± 0.51 D (P = 0.92), postoperative SE was -0.43 ± 0.55 and -0.16 ± 0.64 D (P < 0.001), and arithmetic astigmatism was -0.59 ± 0.46 and -0.88 ± 0.60 D (P < 0.001), for the LASIK and PRK groups, respectively. Fifty-seven and 64.0% eyes had postoperative SE within ± 0.5 D of emmetropia (P = 0.19), and 57.7 and 38.8% eyes were within 0.5 D of attempted astigmatic correction (P < 0.001) for the LASIK and PRK groups, respectively. More PRK eyes were overtreated regarding both SE and astigmatism than LASIK eyes (P < 0.001). The efficacy and safety indices were close to 1.0 in both groups. The surgically induced astigmatism, magnitude of error, index of success, correction index and flattening index were all better in the LASIK group. Both LASIK and PRK achieve good outcomes in high astigmatism. LASIK achieved mild superiority over PRK.

Cross-sectional Study on Corneal Denervation in Contralateral Eyes Following SMILE Versus LASIK.

To compare long-term corneal nerve status following small incision lenticule extraction (SMILE) versus laser in situ keratomileusis (LASIK). Twenty-four patients were randomized to receive SMILE in one eye and LASIK in the other eye. In vivo confocal microscopy examination and dry eye assessments were performed at a mean of 4.1 years postoperatively. The patients were further divided into two groups based on the mean assessment time: 2.7 years postoperatively (2.7 years group) and 5.5 years postoperatively (5.5 years group). Another 6 age-matched normal patients were recruited. At 4.1 years, LASIK eyes had significantly less corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), and corneal total branch density and significantly more nerves with beading than SMILE eyes. The CNFD, CNBD, CNFL, and number of nerves with sprouting were significantly higher in the 5.5 years group than in the 2.7 years group, in both types of surgery, suggesting persistent nerve regeneration. The CNBD and CNFD in the 5.5 years group, regardless of surgical types, were significantly lower than those in the control group, indicating the nerve status had not recovered to normal ranges even at 5.5 years. High myopic treatment resulted in significantly reduced CNFD with LASIK but not with SMILE. There were no significant differences in the dry eye parameters between the two procedures at 4.1 years postoperatively. The impact on corneal nerves following refractive surgery is long-lasting. SMILE had better nerve preservation and regeneration than LASIK, but neither procedure had recovered nerve status to normal levels even at 5.5 years. [J Refract Surg. 2020;36(10):653-660.].

Visual outcomes after SMILE from the first-year experience at a U.S. military refractive surgery center and comparison with PRK and LASIK outcomes.

To assess the visual outcomes of small-incision lenticule extraction (SMILE) after the first year of treatments at a military refractive surgery center and compare with photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) outcomes during the same period. Warfighter Refractive Eye Surgery Program and Research Center, Fort Belvoir, VA. Retrospective study. Records of service members who underwent SMILE, PRK, or LASIK for myopia from March 2017 to February 2018 were reviewed. Preoperative and up to 6-month postoperative data were collected. Visual outcomes were compared between treatments. Of 563 treated eyes, 173 (30.7%) underwent SMILE, 304 (54.0%) PRK, and 86 (15.3%) LASIK. In comparing SMILE with PRK 1 month postoperatively, SMILE (145 eyes [87.9%]) attained uncorrected distance visual acuity (UDVA) ≥20/20 more vs PRK (214 eyes [73.8%]; P < .01). Similarly, SMILE (152 eyes [94.4%]) achieved more eyes with manifest spherical equivalent (MSE) within ±0.50 diopters (D) from intended target vs PRK (250 eyes [85.9%]; P = .01). None lost ≥1 line of corrected distance visual acuity in SMILE vs PRK (16 eyes [5.5%]; P < .01). Thereafter, there were no other significant differences except SMILE had 117 eyes (95.1%) vs PRK with 224 eyes (99.6%) achieving UDVA ≥20/20 at 3 months postoperatively (P = .01). In assessing SMILE vs LASIK, all parameters were comparable; however, 77 SMILE eyes (96.3%) had MSE within ±0.50 D from target vs 31 LASIK eyes (83.8%) at 6 months postoperatively (P = .02). The first year after SMILE treatments in a U.S. military center demonstrated early postoperative outcomes superior to PRK. SMILE seemed more predictable compared with LASIK.

Vector analysis of high (≥3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis

To compare the astigmatic correction in high myopic astigmatism between small-incision lenticule extraction and laser insitu keratomileusis (LASIK) using vector analysis. Hong Kong Laser Eye Center, Hong Kong. Retrospective case series. Patients who had correction of myopic astigmatism of 3.0 diopters (D) or more and had either small-incision lenticule extraction or femtosecond laser-assisted LASIK were included. Only the left eye was included for analysis. Visual and refractive results were presented and compared between groups. The study comprised 105 patients (40 eyes in the small-incision lenticule extraction group and 65 eyes in the femtosecond laser-assisted LASIK group.) The mean preoperative manifest cylinder was -3.42 D±0.55 (SD) in the small-incision lenticule extraction group and -3.47±0.49 D in the LASIK group (P=.655). At 3months, there was no significant between-group difference in uncorrected distance visual acuity (P=.915) and manifest spherical equivalent (P=.145). Ninety percent and 95.4% of eyes were within ± 0.5 D of the attempted cylindrical correction for the small-incision lenticule extraction and LASIK group, respectively (P=.423). Vector analysis showed comparable target-induced astigmatism (P=.709), surgically induced astigmatism vector (P=.449), difference vector (P=.335), and magnitude of error (P=.413) between groups. The absolute angle of error was 1.88±2.25 degrees in the small-incision lenticule extraction group and 1.37±1.58 degrees in the LASIK group (P=.217). Small-incision lenticule extraction offered astigmatic correction comparable to LASIK in eyes with high myopic astigmatism.

Outcomes of presbyopia-correcting intraocular lenses after laser in situ keratomileusis.

Laser in situ keratomileusis (LASIK) is the most common refractive surgery in young patients, which aims at providing a clear distance vision without the use of spectacles. With time, these patients develop symptomatic cataract, which affects activities of daily living, and to improve visual acuity, intraocular lens (IOL) implantation can be considered. In post-myopic LASIK patients, to allow continuation of spectacle independence, the implantation of presbyopia-correcting IOLs is a suitable option. The purpose of this retrospective case series is to report the visual outcome and quality in post-myopic LASIK eyes after the implantation of AT LISA tri839MP IOL. Twenty eyes of 13 patients with history of myopic LASIK within 20years underwent phacoemulsification by one single surgeon. All eyes were implanted with AT LISA tri839PMP IOL, and their outcomes were evaluated at 6months postoperation. The mean postoperative uncorrected distance visual acuity (VA) is 0.28 ± 0.29, while the corrected distance VA is 0.06 ± 0.14. The mean postoperative uncorrected near VA is 0.02 ± 0.05, while the corrected near VA is 0.01 ± 0.02. The mean postoperative manifest refraction spherical equivalent (SE) is - 0.92 ± 0.76D. There is a statistically significant difference between the preoperative and postoperative refraction (p = 0.02), which shows a postoperative myopic shift. There is also a statistically significant difference between the mean targeted SE and postoperative manifest refraction SE (p = 0.00). Only one out of 20 eyes (5%) reported halo and glare symptoms. Ten out of 20 eyes (50%) are able to achieve spectacles independence. In conclusion, in post-myopic LASIK eyes, AT LISA tri839MP provides a good visual outcome at both near and distance, but is more predictable at near than at distance. There is a myopic shift in the postoperative SE. Visual quality is satisfactory and has not been exacerbated. Most patients can remain to be spectacles free at all distances.

Corneal Biomechanical Changes and Tissue Remodeling After SMILE and LASIK.

To evaluate transient corneal tissue healing and biomechanical changes between laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) eyes. In each patient, one eye underwent LASIK and the other underwent SMILE. Optical coherence tomography (OCT) and dynamic Scheimpflug imaging (Corvis-ST) was used to assess tissue healing and biomechanics, respectively. Analyses of OCT scans yielded corneal speckle distribution (CSD) and Bowman's roughness index (BRI). Waveform analyses of deformation amplitude yielded corneal stiffness. Further, corneal force versus corneal deformation data helped compare the two procedures. BRI increased and then decreased transiently after both treatments (P < 0.05). However, SMILE eyes had BRI similar to that of their preoperative state compared to LASIK eyes at 6-month follow-up. CSD indicated a marked increase in the number of bright pixels and a decrease in the number of dark pixels after SMILE (1-month follow-up) and LASIK eyes (3-month follow-up), respectively. CSD returned to near preoperative state thereafter, respectively. Corneal stiffness change from preoperative state was similar between LASIK and SMILE eyes. However, deformation at discrete values of corneal force indicated some recovery of biomechanical strength after SMILE, but not in LASIK eyes. BRI and CSD indicated earlier tissue healing in SMILE eyes than in LASIK. CSD results may indicate delayed cell death in LASIK eyes and increased light scatter due to interface fluid in SMILE eyes. Corneal biomechanical strength remodeled better in SMILE. This may indicate some hydration-related recovery.

Quality of vision after wavefront-guided laser in situ keratomileusis or photorefractive keratectomy: Contralateral eye evaluation

To compare quality of vision between laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California, USA. Prospective randomized case series. Patients had refractive surgery, with 1 eye treated with LASIKand the other with PRK. Eyes were randomized for dominance. The patients completed a questionnaire assessing quality of vision in each eye at the initial visit and 1, 3, 6, and 12months postoperatively. The study comprised 34 patients (68 eyes). There were no initial differences in quality of vision. The PRK eyes had worse clarity during the day (P=.001) and at night (P=.001), worse overall vision (P=.024), more vision fluctuation (P=.006), and more double vision (P=.022) at 1month. Eyes with higher preoperative higher-order aberrations (HOAs) having PRK had worse clarity during the day and at night (P=.006 and P=.012, respectively) and more vision fluctuation (P=.041); PRK eyes with lower preoperative HOAs had worse daytime clarity (P=.036) at 1month. After 1month, there were no differences. The quality of vision was better in LASIK eyes after 1month. At subsequent visits, there was no significant difference in quality of vision.

Outcomes and complications of excimer laser surgery in patients with collagen vascular and other immune-mediated inflammatory diseases

To assess refractive and visual outcomes and postoperative complications in a large number of patients with well-controlled collagen vascular and other immune-mediated inflammatory diseases. Optical Express, Glasgow, United Kingdom. Retrospective case series. The files were reviewed of patients who had collagen vascular and other immune-mediated inflammatory diseases and who had excimer laser surgery between 2008 and 2015. In all cases, the disease was well controlled with no flare or symptoms for a minimum of 6months preoperatively. The study comprised 622 patients (1224 eyes) with 1 of the following underlying diseases: rheumatoid arthritis (50.6% of patients), systemic lupus erythematosus (19.5%), psoriatic arthritis (10.5%), sarcoidosis (10.0%), ankylosing spondylitis (6.4%), multiple sclerosis (1.9%), or scleroderma (1.1%). Laser in situ keratomileusis (LASIK) was performed in 1114 eyes (91.0%) and photorefractive keratectomy (PRK) in 110 eyes (9.0%). The mean follow-up was 10.9months. The preoperative spherical equivalent ranged between -10.13 diopters (D) and +4.13 D (LASIK) and -9.50 D and +4.00 D (PRK). Postoperatively, 81.8% LASIK eyes and 82.3% PRK eyes were within ±0.50 D. The uncorrected distance visual acuity was 20/20 or better in 76.8% and 73.4%, respectively. Complications were mostly those that would be expected after excimer laser surgery in a population of patients without disease with the exception of 1 peripheral flap melt that responded to treatment with topical steroids. Excimer laser surgery can be safely performed in patients with well-controlled collagen vascular or other immune-mediated inflammatory disease. Dr. S.C. Schallhorn is a consultant to Abbott Medical Optics, Inc., Acufocus, Inc., and Carl Zeiss Meditec AG, and a global medical director for Optical Express. No other author has a financial or proprietary interest in any material or method mentioned.

Effect of Laser in Situ Keratomileusis on Schiøtz, Goldmann, and Dynamic Contour Tonometric Measurements.

To assess the effect of laser in situ keratomileusis (LASIK) on ocular rigidity and compare its effect on intraocular pressure (IOP) readings with Goldmann applanation tonometry (GAT), Schiøtz indentation tonometry (ST), and dynamic contour tonometry (DCT). Prospective, observational, single-masked study. Eighty-one patients who underwent myopic LASIK and 108 unoperated myopic control patients were included in the study. The IOP was measured using GAT, DCT, and ST. The coefficient of ocular rigidity (Ko) was obtained from the regression analysis of the 3 readings obtained with each weight of the ST. Linear multiple regression analysis was performed with dummy variables to assess the effects of age, central corneal thickness (CCT), and refractive surgery on measured IOP values. Age, CCT, and previous LASIK explained 39.41% of the IOP readings with GAT, 25.31% with DCT, and 3.28% with ST. LASIK caused a mean decrease of -2.51 mm Hg in IOP readings (P=0.000) with GAT, -1.29 mm Hg (P=0.036) with DCT, and no significant change in IOP readings with ST (P=0.299). Significant differences in the Ko were observed between the LASIK and control groups. The Ko values were unrelated to age and CCT in the LASIK and control groups. ST seems to be less affected by previous LASIK procedures. There is a difference in the ocular rigidity between the unoperated and LASIK eyes that is not correlated with the CCT. Therefore, ST seems to measure changes in the biomechanical behavior of corneas that underwent LASIK surgery.

Phakic foldable angle-supported intraocular lens versus laser in-situ keratomileusis for correction of moderate and high myopia

Objective The objective of this study was to compare the role of phakic foldable angle-supported intraocular lens (IOL) with laser in-situ keratomileusis (LASIK) for correction of moderate and high myopia. Patients and methods Twenty eyes received phakic foldable angle-supported IOL, and 20 eyes received LASIK. Main outcome: slit-lamp microscopy, manifest refraction, uncorrected and best-corrected visual acuity (BCVA), pentacam, IOL calculation (for group 1) with the IOL Master, and specular microscopy were performed before surgery, and 3 and 6 months after surgery. Results At 6 months, the mean spherical equivalent refraction was −0.31 ± 0.44 D (ranging from 0.5 to −1.25 D) in Cachet eyes and −1.04 ± 0.94 D (ranging from 0.25 to −3.5 D) in LASIK eyes. Neither Cachet eyes nor LASIK eyes lost two or more LogMar lines of preoperative BCVA. No Cachet eyes and one LASIK eye lost one LogMar line of preoperative BCVA. The mean percentage of endothelial cell loss in the Cachet group was 8.0% at 6 months, whereas in the LASIK group it was 0.84% at 6 months. Conclusion In this study, Cachet lens implantation and LASIK were found to be effective for the correction of moderate and high myopia. The endothelial cell loss in Cachet eyes was high, which makes it less safe compared with LASIK.

Vector analysis of astigmatic correction after small-incision lenticule extraction and femtosecond-assisted LASIK for low to moderate myopic astigmatism

AimTo compare astigmatic correction between femtosecond-assisted laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE).MethodsA total of 111 patients were included in this prospective study. Fifty-seven eyes were treated...

Wavefront-Guided Versus Wavefront-Optimized Laser in situ Keratomileusis for Patients With Myopia: A Prospective Randomized Contralateral Eye Study

To compare the clinical outcomes of wavefront-guided and wavefront-optimized laser in situ keratomileusis (LASIK). Prospective, randomized, fellow-eye-controlled study. The setting was a single academic institution. The study population included 110 eyes of 55 patients with myopia with and without astigmatism. One eye of each patient was randomized to undergo wavefront-guided LASIK by the AMO Visx CustomVue S4 IR excimer laser system; the fellow eye received wavefront-optimized LASIK by the Alcon Allegretto Wave Eye-Q 400 Hz excimer laser system. Corneal flaps were constructed using the Intralase FS 60 Hz femtosecond laser. Patients were followed at postoperative months 1, 3, 6, and 12. The study's main outcome measures were uncorrected visual acuity, stability of refractive correction, contrast sensitivity, and wavefront aberrometry. After 12 months, LASIK eyes had achieved visual acuity of 20/12.5 or better (30 eyes, 56%) in the wavefront-guided group compared to those receiving wavefront-optimized treatment (22 eyes, 41%) (P = 0.016). Average spherical equivalent refractions were -0.13 ± 0.46 diopters in wavefront-guided eyes whereas in wavefront-optimized eyes the refractions were -0.41 ± 0.38 diopters at 12 months. Wavefront-guided eyes also achieved better best-corrected visual acuity at both the 5% and 25% contrast levels (P = 0.022 and P = 0.004, respectively). There were no differences in levels of residual astigmatism (P = 0.798) or in higher order aberrations (P = 0.869). Both wavefront-guided and wavefront-optimized treatments are able to correct myopia safely and effectively in eyes with and without astigmatism. However, wavefront-guided treatment platforms appear to offer significant advantages in terms of residual refractive error, uncorrected distance acuity and contrast sensitivity.

Meta-analysis of Pentacam vs. ultrasound pachymetry in central corneal thickness measurement in normal, post–LASIK or PRK, and keratoconic or keratoconus-suspect eyes

The aim of this meta-analysis is to evaluate the central corneal thickness (CCT) measurement differences between Pentacam (Oculus Inc., Germany) and Ultrasound Pachymetry (USP) in normal (unoperated eyes , myopic and astigmatic eyes without corneal disease or topographic irregularity), after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK), and keratoconic or keratoconus suspected eyes. We assess whether Pentacam and USP have similar CCT differences in normal, thinner corneas after LASIK or PRK procedures, and kerotoconic or keratoconus suspected eyes. Data sources, including PubMed, Medline, EMBASE, and Cochrane Central Registry of Controlled Trials on the Cochrane Library, were searched to find the relevant studies. Primary outcome measures were CCT measurement between Pentacam and USP. Three groups of eyes were analyzed: normal; LASIK or PRK eyes; and keratoconus suspected or keratoconic eyes. Nineteen studies describing 1,908 eyes were enrolled in the normal group. Pentacam results were 1.47μm ,95% confidence interval (CI) -2.32 to 5.27, higher than USP without statistically significant difference (P = 0.45). Nine studies with total 539 eyes were included in the corneas after LASIK or PRK. The mean difference in the CCT measurement with Pentacam and ultrasound pachymetry was 1.03μm, with the 95% CI -3.36 to 5.42, there was no statistically difference (P = 0.64). Four studies with a total of 185 eyes were included in the keratoconic eyes or keratoconus-suspect group, however,the mean difference was -6.33μm (95% CI -9.17 to-3.49), which was statistically different between Pentacam and ultrasound pachymetry in the CCT measurement (P < 0.0001). Pentacam offers similar CCT results to ultrasound pachymetry in normal eyes, thinner corneas after LASIK or PRK procedures. However, in keratoconic or keratoconus-suspect eyes, Pentacam slightly underestimates the central corneal thickness than does ultrasound pachymetry, which may result from the difficulty in fixation of keratoconic eyes, misalignment of Pentacam and the variation of ultrasonic velocity due to the histological deformation.

Visual performance after conventional LASIK and wavefront-guided LASIK with iris-registration: results at 1 year.

To compare visual performance of wavefront-guided laser in situ keratomileusis (LASIK) with iris-registration (Wg-LASIK group) and conventional LASIK (LASIK group) one year after surgery and analyze the correlation between wavefront aberrations and visual performance. Eight hundred and fifty-two myopic eyes of 430 patients were enrolled in this prospective study and divided into two groups: Wg-LASIK group (436 eyes) and LASIK group (416 eyes). A Wavescan Wavefront aberrometer was used to analyze Zernike coefficients and the root-mean-square (RMS) of higher order aberrations, and Optec 6500 visual function instrument was used to measure contrast sensitivity (CS) before and 3, 6, 12 months after surgery. The mean spherical equivalent (SE) in Wg-LASIK group was significantly better than those in LASIK group one year after surgery (P=0.024). Wg-LASIK eyes showed better CS values than LASIK eyes at all spatial frequencies with and without glare after surgery (P all<0.01). Moreover, the increase of higher RMS (RMSh), coma, RMS3, RMS4, RMS5 in Wg-LASIK group were significantly lower than those in LASIK group 1 year after surgery (P all<0.05). The increase of coma, spherical aberration (SA), RMS3 and RMS4 in Wg-LASIK and coma and RMS3 in LASIK group were negatively correlated with reduction of contrast sensitivity 1 year after surgery. A significant better visual performance is got in Wg-LASIK group compared with LASIK group 1 year after surgery, and the Wg-LASIK is particularly suitable for eyes with high-magnitude RMSh.

The Accuracy of the Double-K Adjustment for Third-Generation Intraocular Lens Calculation Formulas in Previous Keratorefractive Surgery Eyes

To evaluate the effect of the double-K (DK) modification on third-generation formulas. Thirty-eight previously myopic and 24 previously hyperopic eyes that underwent phacoemulsification with intraocular lens (IOL) insertion after Laser in situ keratomileusis (LASIK) were evaluated. Pre-LASIK refraction and keratometry, post-LASIK topography, axial length (AL), IOL type and power, and 1-month postphacoemulsification refraction were recorded spherical equivalent after phacoemulsification (SE(postphaco)). Measured corneal power was adjusted using published and validated methods for postmyopic and posthyperopic LASIK. For each eye, and using SE(postphaco), different DK-IOL formulas were used to calculate the corresponding IOL power, the outcome measure, which was compared with the implanted IOL. DK-Holladay 1 yielded the highest Pearson correlation coefficient (PCC), 0.955 for myopes and 0.943 for high myopes (AL>26 mm). Mean error (ME) and mean absolute error (MAE) for myopes for DK Sanders-Retzlaff-Kraff theoretical formula [DK-SRK/T] were 0.44±0.84 D and 0.75±0.61 D for DK-SRK/T compared with -0.04±0.67 D and 0.52±0.40 D for DK-Holladay 1 (P<0.001 and P=0.016, respectively), and 0.03±0.88 and 0.64±0.58 for DK-Hoffer Q. For high myopes, ME and MAE were 0.75±0.81 D and 0.84±0.69 D for DK-SRK/T, and -0.05±0.74 D (P<0.0001) and 0.57±0.45 D (P=0.019) for DK-Holladay 1. About 29% of DK-SRK/T eyes with large AL had MAE>1.5 D, compared with 0% for DK-Holladay 1 and 14% for DK-Hoffer-Q. Eyes with previous hyperopic LASIK faired similarly for all formulas, with similar PCCs, and only 8% in each category with MAE>1.5 D. DK-SRK/T overestimates IOL power in eyes with large AL, especially with concomitant steep pre-lasik keratometry. Among third-generation formulas, DK-Holladay 1 seems more accurate to use in postmyopic LASIK eyes.

Comparison of dry-eye disease severity after laser in situ keratomileusis and laser-assisted subepithelial keratectomy

To evaluate the effects of laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK) on dry-eye disease markers including tear osmolarity, Schirmer testing, and the ocular surface disease index (OSDI). Laser Suite, Mater Private Hospital, Dublin, Ireland. Prospective controlled cross-sectional observation study. In a single center, consecutive eyes that had LASIK or LASEK had dry-eye disease markers assessed preoperatively and 3, 6, and 12 months postoperatively. In LASIK eyes (n = 50), the mean tear osmolarity was significantly elevated (by 2.8%) at 12 months (P=.009, Student t test). The mean Schirmer test values were not significantly altered postoperatively in either group. The mean OSDI was maximum in LASIK eyes at 3 months (mean follow-up 7.2 months ± 8.2 [SD]) and in LASEK eyes (n = 35) preoperatively (mean follow-up 9.1 ± 9.7 months). There were no significant differences in dry-eye disease markers or tear osmolarity between LASIK and LASEK patients at any stage after surgery up to 1 year. Although tear osmolarity remains one of the highest predictive tests of dry eye, it is complementary with other diagnostic criteria in the context of dry eye after refractive surgery.