Could the percent tissue altered (PTA) index be considered as a unique factor in ectasia risk assessment?

PURPOSE: To evaluate the efficacy, safety, predictability and stability of the percent tissue altered (PTA) formula in post-LASIK (laser-assisted in situ keratomileusis) ectasia risk assessment. METHODS: One hundred and ninety-three eyes from 104 patients with low to moderate myopia that underwent femtosecond LASIK were included in this retrospective, observational and longitudinal study. Seventy-eight eyes were classified in the higher-PTA (> 40%) group and 115 eyes in the lower-PTA (< 40%) group. Spherical manifest refraction, cylinder manifest refraction, logMAR and Snellen previous corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), anterior face Baiocchi Calossi Versaci index (BCVf) and posterior face (BCVb), central corneal thickness (CCT), estimated residual stromal bed (RSB), spherical aberration (SA) and root mean square (RMS) were reported. All patients were followed up for 4 years. RESULTS: In the higher-PTA group, 97% of eyes reported UDVA 20/20 or better, and in the lower-PTA group, all eyes achieved 20/20 or better. No group reported decreased visual acuity. The higher-PTA group obtained 55% of eyes within ± 0.50 D and 90% within ± 1.00 D; and the lower-PTA group obtained 63% of eyes within ± 0.50 D and 90% within ± 1.00 D. Both groups showed a refraction correction of 0.50 D or more in 36% and 31% of eyes, in the higher-PTA and the lower-PTA groups, respectively. CONCLUSION: Percent tissue altered index should not be considered as a unique variable in post-LASIK ectasia risk assessment. Ectasia susceptibility screening should integrate tomography and biomechanical variables in order to help us to decide any refractive treatment choice and increasing refractive surgery safety.

Long-term assessment of visual and refractive outcomes of laser in situ keratomileusis for hyperopia using the AMARIS® 750S Excimer laser.

PURPOSE: To evaluate the long-term efficacy and safety of hyperopic laser in situ keratomileusis (LASIK) using the AMARIS® 750S (Schwind, Eye-tech-solutions, GmbH) excimer laser. METHODS: The medical records of one hundred eleven eyes of 62 patients who underwent LASIK for hyperopia using the AMARIS® 750S excimer laser were reviewed retrospectively. Patients were divided into three groups based on preoperative spherical equivalent (SE) refraction: low hyperopia (less than +2.50 diopters [D]), moderate hyperopia (+2.75D to +4.00D), and high hyperopia (over +4.00D). Uncorrected and best corrected visual acuity (BCVA), long-term stability of refraction, and complications were evaluated. RESULTS: Of the entire sample, the mean preoperative SE was +3.64D±1.22D. The mean age was 37.4±11.2 years (20-59). The mean follow-up for all eyes was 51 months. At the last visit, the mean SE was +0.85D±0.34D (SD) in the low hyperopia group, +1.09D±0.43D in the moderate hyperopia group, and +1.63D±0.47D in the high hyperopia group. (+1.15D±0.49D overall). Preoperative uncorrected visual acuity (UCVA) was 0.52±0.34 logMAR and increased to 0.18±0.15 logMAR at 4 years follow-up (P<0.01). There was no statistically significant difference between preoperative and postoperative BCVA. The UCVA was 0.30 logMAR or better in 100% of eyes in the low hyperopia group, 93.7% in the moderate hyperopia group, and 69.9% in the high hyperopia group (%89.2 overall). CONCLUSIONS: LASIK is safe and effective for correcting hyperopia in the short term; however, the efficacy of the procedure is limited in the patients with high hyperopia and longer follow-up.

Validation of an Objective Scoring System for Forme Fruste Keratoconus Detection and Post-LASIK Ectasia Risk Assessment in Asian Eyes.

PURPOSE: To investigate the efficacy of the SCORE Analyzer (Bausch+Lomb TechnoLas, Germany) in detecting forme fruste keratoconus (FFKC) in Asian eyes and validate its usefulness as a risk assessment system for post-laser in situ keratomileusis (LASIK) keratectasia. METHODS: We retrospectively evaluated corneal topographies with the Orbscan IIz system and independently tested them with the SCORE Analyzer through masked investigators. Eyes were classified into 2 groups: (1) The FFKC group included clinically and topographically normal eyes with definite keratoconus in the contralateral eye. (2) The control group included normal preoperative topographies of patients with LASIK performed at least 4 years before with no resultant keratectasia. The main outcome measures were accuracy indicators: sensitivity, specificity, positive, and negative predictive values. Parameters in the calculation of the SCORE including irregularity at 3 mm, thinnest pachymetry, the difference between central and thinnest pachymetry (CP - TP), vertical decentration of the thinnest point, maximum posterior elevation, and anterior elevation of the thinnest point were compared in both groups. RESULTS: We analyzed 128 Orbscans of 128 Asian patients. There were 24 FFKC eyes and 104 control eyes. SCORE was negative in 7 eyes (false negative) in the FFKC group and was positive in 2 eyes in the control group (false positive). The sensitivity was 70.8%, specificity 98.1%, positive predictive value 89.5%, and negative predictive value 93.6%. Irregularity at 3 mm, thinnest pachymetry, CP - TP, thinnest point decentration, maximum posterior elevation, and anterior elevation of the thinnest point were significantly different in both groups. CONCLUSIONS: The SCORE Analyzer algorithm, developed and validated in eyes of white subjects, was found to be valid and consistent in Asian eyes, showing good sensitivity and specificity in FFKC detection, and to be useful in objectively identifying cases at risk of post-LASIK keratectasia.

Laser in situ keratomileusis versus long-term contact lens wear: decision analysis.

PURPOSE: To compare the risk for vision loss from laser in situ keratomileusis (LASIK) versus long-term contact lens wear using decision analysis. SETTING: Oregon Health & Science University, Portland, Oregon, USA. METHODS: Based on previously published data, a decision tree was constructed using Markov modeling to calculate the probability of vision loss from LASIK versus contact lenses over time. An outcome variable, visual acuity-adjusted life-year (VALY), was defined to account for timing and severity of vision loss. The VALYs were tallied over a 30-year simulation to determine whether the risk for vision loss with contacts exceeded that with LASIK. Sensitivity analyses were performed to test the effect of changes in key variables including probability of contact lens-related keratitis, probability of ectasia after LASIK, and probability of early post-LASIK vision loss. RESULTS: The model's conclusions were highly sensitive to changes in several variables tested, especially risk for post-LASIK ectasia, risk for early vision loss after LASIK, and risk for contact lens-related keratitis (which correlated with type of lenses worn). Rigid gas-permeable lenses were safer than LASIK in every analysis. The safety of LASIK exceeded that for daily-wear soft lenses only when assumptions were most favorable to LASIK, whereas the safety of LASIK always exceeded that for extended-wear lenses except when assumptions were least favorable to LASIK. CONCLUSION: This decision analysis found that the risk for vision loss associated with LASIK and with long-term contact lens wear might be closer than generally assumed.

Quantitative assessment of post-LASIK corneal infiltration with frequency domain anterior segment OCT: a case report.

We present the use of frequency domain (FD) optical coherence tomography (OCT) for quantitative assessment of the infiltration in the eye with post-laser in situ keratomileusis (LASIK) corneal inflammation. Serial OCT images are taken in a patient with post-LASIK inflammation and are used to see the response to treatment over a time period. Clinical value of FD-OCT as a diagnostic tool in objective assessment of corneal inflammation and response to treatment is shown.

Upper disparity limit after LASIK.

We evaluate the effect of the emmetropization technique LASIK (laser-assisted in situ keratomileusis) on stereoscopic vision. For this, we used a mirror stereoscope to measure the upper disparity limit D(max) before (with best correction) and after LASIK for 30 patients. The results show that the upper disparity limit declines from 41.1 min of arc on average to 31.3 min of arc after LASIK, being significant in 83% of the patients. This deterioration is significantly correlated with an increase in the postsurgical interocular differences in higher-order aberrations, corneal asphericity, and presurgical anisometropia. New ablation algorithms should minimize interocular differences in order to improve binocular visual performance.

[Assessment of tears secretion after refractive surgery]. / Ocena wydzielania lez u pacjentów po chirurgii refrakcyjnej.

PURPOSE: One of the complications of the corneal refractive surgery is a transient disturbance in tears secretion, which can lead to the dry eye syndrome. The aim of the study was to evaluate the tears secretion in patients after PRK, LASEK and LASIK surgery for myopia. MATERIAL AND METHODS: We examined 115 eyes of 69 patients (46 woman and 23 men), mean age 30.82, with myopia and myopic astigmatism, treated with three different refractive procedures. The patients included in this study were divided into three groups: Group I: 35 eyes of 22 patients (15 woman and 7 men) treated with PRK. The mean spherical equivalent of the refractive error was -4.18 dioptres (from -8.75 to -2.0). Group II: 41 eyes of 23 patients (13 woman and 10 men) treated with LASEK. The mean spherical equivalent of the refractive error was -5.73 dioptres (from -12.0 to -2.75). Group III: 39 eyes of 24 patients (18 woman and 6 men) treated with LASIK. The mean spherical equivalent of the refractive error was -7.49 dioptres (from -10.75 to -3.75). In this study the amount of tears secreted was analyzed on the base of Schirmer I test, performed before and after surgery. Test was always performed in the same room, in the morning hours (before noon), with constant temperature and air humidity values. RESULTS: In the PRK group the mean value of Schirmer I test was 20.91 mm before surgery. 14 days after surgery the mean value decreased to 14.09 mm, 1 month after surgery to 11.66 mm. Then increase in tears secretion was observed: 2 months after surgery the mean value of Schirmer I test was 13.94 mm, 3 months after surgery 15.23 mm, and 6 months after surgery 17.4 mm. In the LASEK group the mean value of Schirmer I test was 20.39 mm before surgery. 14 days after surgery the mean value decreased to 15.78 mm, 1 month after surgery to 13.05 mm. Two months after surgery the mean value of Schirmer I test was 15.24 mm, 3 months after surgery 16.17 mm, and 6 months after surgery 18.15 mm. In the LASIK group the mean value of Schirmer I test was 20.72 mm before surgery. 14 days after surgery the mean value decreased to 12.97 mm, 1 month after surgery to 5 mm. 2 months after surgery mean value of Schirmer I test was 12.79 mm, 3 months after surgery 15.05 mm, and 6 months after surgery 17.82 mm. CONCLUSIONS: Corneal refractive surgery causes transient reduction of tears secretion, especially during the first three postoperative months. The tears secretion was reduced most significantly in the LASIK group. In patients treated with PRK and LASEK tears secretion during the postoperative period was comparable with slightly better secretion in the LASEK patients.

Loss of vision after laser in situ keratomileusis.

PURPOSE: To research the incidence of visual loss after laser in situ keratomileusis (LASIK). METHODS: We reviewed an extensive review of the literature published by The Ophthalmic Technology Assessment Committee of the American Academy of Ophthalmology regarding the safety and efficacy of LASIK. We also reviewed other recent literature. RESULTS: For low to moderate myopia and astigmatism, LASIK is efficient, safe, and predictable with few eyes losing two or more lines of best-corrected visual acuity (BCVA). For moderate to high myopia, the results are more variable and more eyes lost two or more lines BCVA. In both cases, this BCVA occurred in studies published on or before 1999. CONCLUSION: Serious adverse complications leading to significant visual loss are probably rare. Continued development of microkeratomes and laser technology are continuing to reduce the rare complications that do occur and improve functional outcomes and patient satisfaction.

Assessment of anterior chamber flare and cells after laser in situ keratomileusis.

PURPOSE: To determine the presence of anterior chamber flare and cells after laser in situ keratomileusis (LASIK) for the correction of myopia. SETTING: Hermann Eye Center and the University of Texas Medical School, Department of Ophthalmology and Visual Science, Houston, Texas, USA. METHODS: Forty-three eyes of 23 consecutive patients ranging in age from 24 to 62 years had LASIK for myopia. All surgeries were performed by a single surgeon using a VISX Star laser and the same technique. Patients received no preoperative antiinflammatory medications. Postoperatively, all patients were instructed to use 1 drop of ofloxacin (Ocuflox) and 1 drop of fluorometholone 0.1% (FML) in the operated eye 4 times daily while awake for 7 days. At baseline and postoperative days 1, 7, and 28, anterior chamber flare was measured and cells were counted using a Kowa laser flare meter (FM-500) and laser cell counter (LC-500), respectively. RESULTS: Flare and cells increased significantly on day 1 (P <.0001 for both flare and cells) and returned to preoperative levels by day 7. No statistically significant correlation was detected between the amount of inflammation and the number of laser pulses (P =.2922) or the ablation time (P =.8383). CONCLUSIONS: A significant increase in anterior chamber inflammation occurred during the first 24 hours after LASIK. Inflammation levels then subsided to preoperative levels by day 7 with steroid use. Anterior chamber inflammation did not appear to correlate with the duration of the ablation or the number of laser pulses.

[Bilateral simultaneous LASIK. Pro and contra]. / Bilaterale simultane LASIK. Pro und Kontra.

Until recently simultaneous bilateral laser in situ keratomileusis (LASIK) was regarded as contraindicated in Germany. However, the procedure was sporadically performed, because it offers patient comfort and is more cost effective than sequential LASIK. Even though the complication rate is below the calculated rate of 0.01%, bilateral complications may have catastrophic effects on the patient. In addition, there is the theoretical disadvantage that the results from the first eye cannot be used for the second eye. However, this effect has yet to be clinically proven.

Communicating with laser vision correction patients.

Laser vision correction or LASIK has a long and excellent history with significant benefits and unlikely risks. Adequately educating patients should allay their fears and allow good candidates to enjoy the life changing benefits of improvement in the natural vision through laser vision correction.