Laser In Situ Keratomileusis Eyes Research Articles

Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis

Purpose To study the accuracy and predictability of intraocular lens (IOL) power calculation in eyes that had laser in situ keratomileusis (LASIK). Setting Gimbel Eye Centre, Calgary, Alberta, Canada. Methods Refractive outcomes in 6 cataract surgery and lensectomy eyes after previous LASIK were analyzed retrospectively. Target refractions based on measured and refraction-derived keratometric values were compared with postoperative achieved refractions. Differences between target refractions calculated using 5 IOL formulas and 2 A-constants and achieved refractions were also compared. Results The refractive error of IOL power calculation in postoperative LASIK eyes was significantly reduced when refraction-derived keratometric values were used for IOL power calculation. Persistent residual hyperopia still occurred in some cases; this was corrected by hyperopic LASIK. Refractive results appeared more accurate and predictable when the Holladay 2 or Binkhorst 2 formula was used for IOL power calculation. Conclusion Hyperopic error after cataract surgery in post-LASIK eyes was significantly reduced by using refraction-derived keratometric values for IOL power calculation. Persistent hyperopic error was corrected by hyperopic LASIK.

A comparison of visual acuity, predictability, and visual function outcomes after intracorneal ring segments and laser in situ keratomileusis. Suiter BG, Twa MD, Ruckhofer J, Schanzlin DJ. Tr Am Ophth Soc 2000;98:51–57.

The authors compared the correction of low myopia by intrastromal corneal ring segments (IRCS) and by laser in situ keratomileusis (LASIK) with respect to early visual recovery and refractive outcomes. Eighty-two eyes implanted with ICRS in a phase III study for US Food and Drug Administration review were matched with 133 eyes treated with LASIK by criteria of age (>18 years, <65 years), preoperative myopia (−1.00–−3.50 diopters [D]), astigmatism (≤1.00D), single treatment, and attempted full correction. Examinations were performed preoperatively and postoperatively at days one and seven and months one and three. Visual acuity and manifest refraction data were collected retrospectively. Visual function scores were assigned, and summarized results were compared. Uncorrected visual acuity was 20/20 or better at day 1 in 24% of eyes (20/82) after ICRS and in 55% of eyes (73/133) after LASIK, and at month three in 75% of eyes (58/77) after ICRS and in 67% of eyes (84/126) after LASIK. Spherical equivalent refraction at month three was within ±1.00D of intended correction in 99% of eyes (76/77) after ICRS and in 96% of eyes (121/126) after LASIK. Excellent visual function scores were noted at month three in 90% of eyes (69/77) after ICRS and in 78% of eyes (98/126) after LASIK. Patients treated with LASIK showed better uncorrected visual acuity immediately following surgery; however, beyond one month, patients treated with ICRS achieved better uncorrected visual acuity that continued to improve with time. Visual function scores indicate that ICRS eyes see at higher levels of uncorrected visual acuity than LASIK eyes do with the same refractive error. The authors conclude that the ICRS and LASIK were comparable in the correction of mild myopia.—Thomas J. Liesegang

Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis

Purpose To evaluate and compare tear secretion and tear film instability following photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Setting Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea. Methods In a prospective study, 36 eyes (21 patients) had PRK and 39 eyes (25 patients) had LASIK to correct myopia. Tear secretion and tear film instability were tested preoperatively and 3 and 6 months postoperatively using Schirmer test values, tear breakup time (BUT) scores, and tear osmolarity. Results Six months after surgery, the change in Schirmer test values from preoperative levels was –14.57% ± 6.39% (SD) in the PRK eyes and –23.40% ± 5.94% in the LASIK eyes and the change in BUT scores, –12.54% ± 8.28% and –18.79% ± 13.01%, respectively. The change in tear osmolarity was 14.95% ± 6.46% and 35.63% ± 8.51%, respectively. Conclusions The decrease in tear secretion was greater after LASIK than after PRK at 6 months. Proper treatment of dry eye is required after LASIK and PRK, particularly in the LASIK postoperative period.

Pathogenesis and management of laser in situ keratomileusis flap buttonhole

PurposeTo describe the clinical features and outcomes in patients who had a flap buttonhole during laser in situ keratomileusis (LASIK) and propose an etiopathogenic mechanism for this complication. SettingUniversity Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. MethodsRetrospective review of case records of 6 patients (6 eyes) who had a flap buttonhole during LASIK. ResultsThe mean patient age was 38.2 years ± 4.1 (SD) and the mean preoperative spherical equivalent (SE) refraction, −8.13 ± 4.04 diopters (D). Mean keratometry was 44.20 ± 1.30 D. Retreatment was performed after a mean interval of 9.2 ± 3.2 months. Final postoperative SE refraction was −0.44 ± 0.58 D after a mean follow-up of 59.0 ± 5.3 weeks. No patient experienced loss of best spectacle-corrected visual acuity. ConclusionsRetreatment of eyes that have a flap buttonhole during LASIK is associated with good visual outcomes. Flap buttonholes can produce alterations in refraction, so retreatment is best performed after the refractive error has stabilized. Microkeratome malfunction may be responsible for the occurrence of a flap buttonhole during LASIK in eyes that do not have significant corneal steepening.

Photoastigmatic Refractive Keratectomy or Laser in situ Keratomileusis for Moderate and High Myopic Astigmatism

To compare the efficacy and safety of laser in situ keratomileusis (LASIK) and photoastigmatic refractive keratectomy (PARK) to treat moderate and higher myopic astigmatism. A retrospective nonrandomized study of 78 eyes with myopic astigmatism (range, 2.00 to 6.00 D) was undertaken. Thirty-eight eyes were treated with LASDK and 40 eyes were treated with PARK. Groups were similar in terms of baseline sphere and refraction. Photoablation for both LASDX and PARK was performed by single pass for correction of -6.00 D or less spherical equivalent refraction or multi-pass, multi-zone at 4, 5, and 6 mm for corrections greater than -6.00 D. Astigmatism was corrected using a single-pass ablation at 6.0 mm diameter. Visual acuity, manifest refraction, corneal topography, and patient satisfaction were measured preoperatively and postoperatively. Six months postoperatively, uncorrected visual acuity was 20/40 or better in 100% of LASEK eyes and 90.0% of PARK eyes; 20/25 in 86.84% LASEK eyes and 47.5% of PARK eyes; 20/20 in 65.75% of LASEK eyes and 15% of PARK eyes. Postoperative residual cylinder was -0.54 ± 0.32 D in LASEK eyes and -1.28 ± 0.80 D in PARK eyes. Postoperative residual cylinder axis remained stable (within 15° at 1 month postoperatively) in 61.1% of LASEK eyes and 40% of PARK eyes. In 5.3% of the LASEK eyes, corneal haze developed; 95.5% of PARK eyes developed corneal haze. One LASIK eye lost best spectacle-corrected visual acuity and 3 eyes (7.89%) had a cap complication. Three eyes (7.5%) lost 2 lines of spectacle-corrected visual acuity due to severe corneal haze. Among LASEK patients, 92.1% were highly satisfied and 62.5% of PARK patients were highly satisfied. For myopic astigmatism between 2.00 and 6.00 D, LASEK provided better accuracy, fewer complications, and higher patient satisfaction than PARK. PARK may achieve an incomplete cylindrical correction and may have a higher associated rist of loss of best spectacle-corrected visual acuity. [J Refract Surg 2000;16(suppl):S268-S271).

Photorefractive keratectomy versus laser in situ keratomileusis: A control-matched study

ObjectivePhotorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) outcomes were compared at 1, 3, 6, and 12 months after surgery. DesignRetrospective, nonrandomized, comparative study. ParticipantsOne hundred seven LASIK-treated eyes (58 patients) and 107 PRK-treated eyes (91 patients) having myopia between −1 and −9.50 diopters (D). All LASIK-treated eyes were analyzed retrospectively and matched with PRK-treated eyes having sphere within ±0.25 D, ±1 D of cylinder, and ± 7 years of age. InterventionFor PRK and LASIK, the refractive surgery was performed with the slit-scanning excimer laser Nidek EC-5000, (Nidek Co. Tokyo, Japan) Main outcome measuresManifest refraction, best-spectacle and uncorrected Snellen visual acuity, haze, halos, and keratometry were evaluated before surgery and up to 12 months after surgery. ResultsSeventy percent of eyes were evaluated at the 12-month postoperative exam. Of these eyes, 83% of LASIK cases and 86% of PRK cases had uncorrected visual acuities of 20/20 or better. Refractions within ±0.5 D represented 78% of the LASIK eyes and 83% of the PRK eyes at that follow-up. Patients who underwent LASIK reported halos twice as often as patients who underwent PRK using a subjective scale. The odds ratio of high halos for LASIK versus PRK was 3.50 (95% confidence interval, 1.89–6.46; P < 0.0001). At 1 month after surgery, 64% of the LASIK eyes were within ±0.50 D compared with 77% of the PRK eyes. No eye lost 2 Snellen lines of best corrected visual acuity at 6 or 12 months after surgery. Ten PRK eyes (9.3%) and three LASIK eyes (2.8%) were retreated. ConclusionsPRK and LASIK achieved equal refractive outcomes at all postoperative follow-ups, but LASIK patients were twice as likely to experience halos.

Ablation centration after active eye-tracker-assisted photorefractive keratectomy and laser in situ keratomileusis

PurposeTo evaluate the ablation centration after active eye-tracker-assisted photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and to investigate the effect of surgery, patient, and surgeon on the centration. SettingDepartment of Ophthalmology, China Medical College Hospital, Taichung, Taiwan, Republic of China. MethodsThis retrospective study comprised 177 eyes of 101 patients: 16 eyes had PRK and 161, LASIK. All laser treatments were performed with the aid of an eye tracker. The amount of decentration was analyzed by corneal topography. The factors influencing centration were divided into surgery related (PRK/LASIK), patient related (low/high myopia and effect of learning), and surgeon related (learning curve). ResultsThe mean decentration was 0.33 mm in PRK eyes and 0.35 mm in LASIK eyes. For the surgery-related factor, there was no significant difference between the PRK and LASIK eyes. For the patient-related factors, centration was better in the second eye (effect of learning) and decentration was more severe in eyes with high myopia (low/high myopia). For the surgeon-related factor, there was no significant difference between eyes that had the first 50 LASIK procedures and those that had the last 50 procedures. ConclusionsAn eye tracker, which makes the laser beam follow the eye’s movements, helps to avoid severe decentration. This study showed, however, that an active eye-tracking system alone cannot ensure good centration. Patient cooperation and fixation are important.

Optical coherence tomography evaluation of the corneal cap and stromal bed features after laser in situ keratomileusis for high myopia and astigmatism

ObjectiveTo study the corneal microstructure by optical coherence tomography (OCT) after laser in situ keratomileusis (LASIK) for high myopia with and without astigmatism. DesignNonrandomized self-controlled comparative trial. ParticipantsSixty-three consecutive LASIK eyes with spherical equivalent refraction between −6.0 and −17.0 diopters (D) and astigmatism between 0.0 and −5.0 D were prospectively recruited for examination. InterventionLASIK was performed with the Chiron Hansatome microkeratome (160-μm fixed plate) and Summit Apex Plus excimer laser using a 5.5/6.0/6.5-mm multizone pattern. Proper preoperative calculations were performed to ensure stromal beds thicker than 250 μm. Main outcome measuresOCT imaging and measurement of corneal thickness was performed preoperatively. In addition, corneal cap and stromal bed thickness measurements were performed 1 day, 1 month, and 3 months postoperatively. ResultsThe average central corneal pachymetry was 538.9 ± 26.2 μm preoperatively. Mean corneal cap thickness measured 124.8 ± 18.5 μm 1-day postoperatively. Mean stromal bed thickness was 295.2 ± 37.1 μm on the first postoperative day. Compared with the 1-day postoperative examination, the average stromal bed thickness increased significantly by 5.9 μm (P = 0.001) and 7.2 μm (P = 0.001) at the 1-month and 3-month postoperative examinations, respectively. Mean difference between actual (118.7 ± 27.8 μm) and predicted (104.1 ± 20.8 μm) central ablation depths was 14.6 ± 16.7 μm (P = 0.0001). A weak but statistically significant positive association was found between preoperative refraction and the difference between expected and real ablation depth values (R = 0.26; P = 0.042). Posterior stromal beds were more than 250-μm thick in 58 eyes (89.9%) 1 day postoperatively. This safety requirement improved at the 1-month postoperative examination, when the partial regression accounted for slightly thicker stromal beds and only two cases (3.2%) exhibited posterior stromal tissue thinner than 250 μm. These two cases were seen only for corrections exceeding 12 D (P = 0.04). ConclusionsOCT appears to be a useful tool for the evaluation of both the qualitative and quantitative anatomic outcome of LASIK. Corrections of higher degrees of ametropia run a higher risk of producing a thinner than expected central cornea. Particularly, corrections greater than 12 D may lead eventually to stromal beds thinner than 250 μm, despite proper preoperative calculations. Because corneal flaps are usually thinner than expected with the microkeratome used herein, adequate posterior corneal stroma is preserved in most instances.

Comparison of objective and subjective refraction before and after laser in situ keratomileusis

Purpose To compare the accuracy and reliability of objective and subjective refractions before and after laser in situ keratomileusis (LASIK) for myopia, hyperopia, and astigmatism. Setting Augenchirurgie und Laserzentrum Hochrum, Innsbruck, Austria. Methods In this prospective study, the objective refraction obtained with the Nidek AR-K 900 autorefractor was compared with the subjective refraction in 159 eyes (125 with myopia and 34 with hyperopia) operated on with 2 different lasers. Refractions were done before and 6 months after LASIK. Results Preoperatively, the objective and subjective refractions correlated better in eyes with low myopia than in those with high myopia ( P < .01). Postoperatively, objective refraction was less accurate and reliable than preoperatively. The difference between the objective and subjective spherical refractions was statistically significant ( P < .0001) after LASIK in eyes with hyperopia. The correlation between the objective and subjective cylindrical refractions was stronger preoperatively. Especially after LASIK for hyperopia, the objective refraction did not reliably assess the magnitude and axis of the cylinder. The preoperative refractive error did not significantly affect the preoperative and postoperative difference between the objective and subjective refractions or the change between the preoperative and postoperative mean differences. The type of excimer laser used significantly affected the difference between the objective and subjective refractions. Conclusions Especially after LASIK for hyperopia, the objective refraction determined with the Nidek AR-K 900 autorefractor delivered erroneous results, which have implications for postoperative care and preoperative measurements for ocular surgery such as enhancement procedures or cataract surgery.

Surgically induced astigmatism after photorefractive keratectomy and laser in situ keratomileusis

Purpose: To compare the axis and magnitude of surgically induced astigmatism inphotorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Setting: Multicenter clinical trial. Methods: In this prospective, randomized trial, 220 eyes of 220 patients entered the study cohort; 105 randomized to PRK and 115 to LASIK. All patients received a single-pass, multizone excimer laser ablation as part of a PRK or LASIK procedure. Attempted corrections ranged from −6.00 to −15.00 diopters (D). The LASIK procedures were performed with nasal hinges. Absolute changes in astigmatism and axis and magnitude of surgically induced astigmatism were analyzed. Patients were followed for up to 6 months. Results: In the PRK group, the mean change in absolute astigmatism was +0.14,+0.16, and +0.32 D at 1, 3, and 6 months, respectively; in the LASIK group, the mean change was −0.15, −0.08, and −0.03 D, respectively. At all time points, a greater proportion of PRK than LASIK eyes had an increase in absolute magnitude of astigmatism. In the PRK group, the axis of vectoral-induced astigmatism was significantly different from random at 3 and 6 months ( P = .01, P < .001, respectively) with a tendency for induced with-the-rule shifts postoperatively. In the LASIK group, the axis of vectoral-induced astigmatism was significantly different from random at only 1 month ( P = .04), and there was no preponderant direction of axis shift. Despite these findings, other analyses ,showed no statistically significant between-group differences in vectoral axis or magnitude of surgically induced astigmatism. Conclusions: Induced astigmatism was generally less and more random in axis in LASIK than in PRK; a general trend for induced with-the-rule astigmatism in PRK. was not seen in LASIK. Hypothetically, the lamellar corneal flap in LASIK may counteract the tendency toward steepening at 90 degrees seen in PRK by retracting toward the hinge, by masking underlying induced astigmatism in, the ablation zone, or by its mitigating influence on postoperative corneal healing.

Laser in situ keratomileusis versus arcuatekeratotomy to treat astigmatism

Purpose: To analyze the effectiveness of laser in situ keratomileusis (LASIK) andarcuate keratotomy (AK) to treat simple myopic, compound myopic, and mixed astigmatism. Setting: Instituto de la Vision, Buenos Aires, Argentina. Methods: This retrospective nonrandomized study comprised 821 cases treated with LASIK and 46 cases treated with AK. Patients were divided into 4 groups, which had the following preoperative cylinder corrections: simple myopic astigmatism (Group 1) (LASIK: n = 76, −3.91 diopters [D] ± 1.29 [SD]; AK: n = 5, −3.85 ± 0.65 D); compound myopic astigmatism up to 2.00 D (Group 2) (LASIK: n = 401, −1.69 ± 0.76 D; AK: n = 14, −1.48 ± 0.41 D); compound myopic astigmatism over 2.00 D (Group 3) (LASIK: n = 253, −3.61 ± 0.89 D; AK: n = 16, −3.09 ± 0.84 D); mixed astigmatism (Group 4) (LASIK: n = 91, +3.65 ± 1.62 D; AK: n = 11, 4.39 ± 0.92 D). Results: Six months postoperatively, the cylinder's vector-corrected change was as follows: Group 1, LASIK 3.75 ± 1.08 D, AK 3.16 ± 0.84 D; Group 2, LASIK 1.55 ± 1.12 D, AK 1.34 ± 0.44 D; Group 3, LASIK 3.39 ± 0.98 D, AK 2.70 ± 1.21 D; Group 4, LASIK 3.77 ± 1.43 D, AK 3.75 ± 0.89 D. Respective mean uncorrected visual aeuities in each group were as follows: Group 1, 0.71 ± 0.12 and 0.60 ± 0.12; Group 2, 0.83 ± 0.12 and 0.78 ± 0.24; Group 3, 0.78 ± 0.18 and 0.48 ± 0.24; Group 4, 0.69 ± 0.21 and 0.55 ± 0.18. Conclusions: The vector-corrected change and visual acuity achieved with LASIK were better, although not significantly, than those attained with AK except for the UCVA obtained with LASIK in eyes with compound myopic astigmatism over 2.00 D. Both methods proved to be safe.

Comparison of photorefractive keratectomy with excimer laser in situ keratomileusis in correcting low myopia (from −2.00 to −5.50 diopters): A randomized study

Objective To compare laser in situ keratomileusis (LASIK) with photorefractive keratectomy (PRK) in the correction of myopia from −2.00 to −5.50 diopters. Design Prospective, randomized, paired clinical trial. Participants Fifty-two eyes of 26 myopic patients were enrolled in the study. Intervention Each patient received PRK on one eye (PRK eye) and LASIK on the other (LASIK eye); the procedure assigned to each eye, and the sequence of surgeries for each patient was randomized. Main outcome measures Slit-lamp microscopy, manifest refraction, uncorrected and spectacle-corrected visual acuity, and videokeratography were done before operation, and 2 weeks, 6 weeks, 3 months, 6 months, and 12 months after operation. Patient satisfaction and preference were assessed by a subjective questionnaire. Results All LASIK eyes had fast, painless recovery. At 1 year, 24 patients (92.3%) were examined, the mean spherical equivalent refraction was −0.08 ± 0.38 diopter in the PRK eyes and −0.14 ± 0.31 diopter in the LASIK eyes, and the uncorrected visual acuity was 20/20 or better in 15 PRK eyes (62.5%) and 19 LASIK eyes (79.2%); no eye lost 2 or more Snellen lines of spectacle-corrected visual acuity. Both procedures were stable throughout the first year. One PRK eye developed dense subepithelial corneal haze. The strongest correlate to spectacle-corrected visual acuity after the two procedures was the coefficient of variation of corneal power over the pupil. Nineteen patients (79.2%) preferred the LASIK procedure because of the fast, painless recovery. Conclusions In the current study, PRK and LASIK were found to be similarly effective, predictable, stable, and reasonably safe for the correction of myopia between −2.00 and −5.50 diopters. Laser in situ keratomileusis has the advantage of fast, painless recovery. Patients prefer LASIK.

Laser in situ keratomileusis for undercorrection after radial keratotomy.

To assess the safety and efficacy of excimer laser in situ keratomileusis (LASIK) in treating residual myopia and/or astigmatism following refractive keratotomy. Fourteen eyes that had previously undergone radial and/or arcuate keratotomy were included. The surgeries were performed using the Chiron Automated Microkeratome and the VISX 20/20B excimer laser. Average follow-up was 12.64+/-5.02 months. Mean spherical equivalent refraction was reduced from -3.48+/-3.52 D preoperatively to -0.04+/-0.87 D postoperatively. At the last follow-up examination there were 8 eyes (57.1%) with a refraction within+/-0.50 D, and 10 eyes (71.4%) within +/-1.00 D of emmetropia. Uncorrected visual acuity was 20/20 or better in 4 eyes (28.6%) and 20/40 or better in 10 eyes (71.4%). Vector analysis of the astigmatic correction showed an index of success of 80%. There was no significant loss (> or = or =2 lines) of spectacle-corrected visual acuity. We observed interface epithelial ingrowth in one eye. The correction of residual myopia and/or astigmatism with LASIK in eyes with prior refractive keratotomy proved to be safe and effective. Careful preoperative evaluation may help to avoid complications such as reopening of incisions during surgery or postoperative ingrowth of epithelium beneath the corneal flap.

Incidence and management of intraoperative and early postoperative complications in 1000 consecutive laser in situ keratomileusis cases

Objective To identify intraoperative and early postoperative complications of laser in situ keratomileusis (LASIK) surgery learning curve and to offer recommendations on prevention and management. Design Retrospective noncomparative case series. Participants The first 1000 consecutive myopic LASIK eyes (April 1995-February 1997) operated on by one surgeon (HVG) were examined. Intervention Myopic LASIK surgery was performed with the Chiron Corneal Shaper and NIDEK EC-5000 excimer laser. Main outcome measures The preoperative and 6-month postoperative spherical equivalent, best-corrected visual acuity, and corneal status were recorded, as was the incidence of intraoperative and early postoperative complications. The rate of retreatments was also recorded. Results There were 32 (3.2%) intraoperative complications and surgical events recorded, including 19 (1.9%) microkeratome-related flap complications and 13 (1.3%) nonmicrokeratome-related surgical events such as inability to obtain sufficient suction. There were 18 (1.8%) postoperative complications requiring repositioning of microwrinkled or shifted flaps. Six-month spherical equivalent was −0.52 diopter [D] ± 1.19 D for eyes with microkeratome complications, −0.56 D ± 1.07 D for the group with nonmicrokeratome-related intraoperative events, and −0.78 D ± 0.92 for eyes requiring postoperative flap repositioning. None of the 32 eyes with intraoperative complications and surgical events lost 2 or more lines of vision. One eye in the postoperative complications group lost two lines of vision. The rate of microkeratome complications related to surgical technique and the overall surgery times decreased over the course of the first 1000 myopic LASIK cases. Conclusion The complications encountered during the early learning curve of LASIK surgery have not in this series resulted in a significant loss of best-corrected visual acuity. With increasing surgical experience, the incidence of complications, along with surgical times, has decreased.