Laser in situ Keratomileusis Retreatment for Residual Myopia and Astigmatism

Clinical Outcomes of an Optimized Prolate Ablation Procedure for Correcting Residual Refractive Errors Following Laser Surgery

Purpose

The purpose of this study was to investigate the clinical efficacy of an optimized prolate ablation procedure for correcting residual refractive errors following laser surgery.

Methods

We analyzed 24 eyes of 15 patients who underwent an optimized prolate ablation procedure for the correction of residual refractive errors following laser in situ keratomileusis, laser-assisted subepithelial keratectomy, or photorefractive keratectomy surgeries. Preoperative ophthalmic examinations were performed, and uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction values (sphere, cylinder, and spherical equivalent), point spread function, modulation transfer function, corneal asphericity (Q value), ocular aberrations, and corneal haze measurements were obtained postoperatively at 1, 3, and 6 months.

Results

Uncorrected distance visual acuity improved and refractive errors decreased significantly at 1, 3, and 6 months postoperatively. Total coma aberration increased at 3 and 6 months postoperatively, while changes in all other aberrations were not statistically significant. Similarly, no significant changes in point spread function were detected, but modulation transfer function increased significantly at the postoperative time points measured.

Conclusions

The optimized prolate ablation procedure was effective in terms of improving visual acuity and objective visual performance for the correction of persistent refractive errors following laser surgery.

Photorefractive Keratectomy for Residual Myopia after Myopic Laser In Situ Keratomileusis

Purpose. To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) on the corneal flap for correction of residual myopia following myopic laser in situ keratomileusis (LASIK). Patients and Methods. A retrospective study on eyes retreated by PRK on the corneal flap for residual myopia after LASIK. All eyes had no enough stroma after LASIK sufficient for LASIK enhancement. Data included spherical equivalent (SE), uncorrected and best corrected visual acuity (UCVA and BCVA), central pachymetry, corneal higher order aberrations (HOAs), corneal hysteresis (CH), corneal resistance factor (CRF), and corneal haze. Results. The study included 64 eyes. Before PRK, the mean central pachymetry was 400.21 ± 7.8 μm, the mean SE was -1.74 ± 0.51 D, and the mean UCVA and BCVA were 0.35 ± 0.18 and 0.91 ± 0.07, respectively. 12 months postoperatively, the mean central corneal thickness was 382.41 ± 2.61 μm, the mean SE was -0.18 ± 0.32 D (P < 0.01), and the mean UCVA and BCVA were 0.78 ± 0.14 (P = 0.01) and 0.92 ± 0.13 (P > 0.5), respectively. The safety index was 1.01 and the efficacy index was 0.86. No significant change was observed in corneal HOAs. Conclusions. Residual myopia less than 3 D after LASIK could be safely and effectively treated by PRK and mitomycin C with a high predictability. This prevents postoperative ectasia and avoids the flap related complications but has no significant effect on HOAs.

Aspheric Ablation Depth as the Target Depth for Enhanced Wavefront-Guided Myopic Retreatments After Laser-Assisted In Situ Keratomileusis

PURPOSE

To propose a new adjustment method and present the clinical result of wavefront-guided myopic laser-assisted in situ keratomileusis (LASIK) retreatment with an aspheric program-targeted central ablation depth to avoid refractive overcorrection.

METHODS

Thirty-two eyes (of 20 consecutive patients) that underwent wavefront-guided LASIK myopic retreatment between January 2009 and February 2012 after primary wavefront-guided LASIK for myopia were included. Wavefront-guided retreatments were performed using the Bausch and Lomb Technolas 217z100 excimer laser system. Wavefront-guided retreatments were adjusted by setting the ablation depth corresponding to the ablation depth determined by the aspheric program. The refractive outcome, visual outcome, and outcome of high-order aberrations (HOAs) were analyzed. Linear mixed models were also used to evaluate the predicting factors for retreatment offset.

RESULTS

Mean age was 29.5 ± 3.1 years. Spherical equivalent (SE) before retreatment was -1.0 ± 0.44 diopters (D) (range, -2.25 to -0.5). Twelve months postoperatively, SE was -0.03 ± 0.12 D, and 31 of 32 eyes had an uncorrected visual acuity 20/20 or better. All eyes were within ±0.5 D. None of the eyes had lost >2 lines of Snellen visual acuity. Safety and efficacy indices were 1.03 and 1.00, respectively. Total HOA, coma, and trefoil were reduced significantly (P = 0.028, P = 0.036, P = 0.034, respectively). Predictive factors for the amount of offset required are significantly related to preoperative SE (P = 0.006) and spherical aberration (P = 0.03, adjusted by SE).

CONCLUSIONS

Setting the target ablation depth using the aspheric program provided high refractive predictability with a satisfactory visual outcome, significant reduction of HOAs, and no overcorrections.

A retrospective comparison of efficacy and safety of 680 consecutive lasik treatments for high myopia performed with two generations of flying-spot excimer lasers

PURPOSE

To compare the visual refractive outcome and complication of laser in situ keratomileusis (LASIK) carried out with a Carl Zeiss-Meditec MEL-70 Excimer laser and a MEL-80 laser for treatment of high myopia.

METHODS

Journal records of 680 consecutive eyes that underwent LASIK with a Schwind Supratome microkeratome and a MEL-70 Excimer laser (Group A), or a Moria M2 microkeratome and a MEL-80 Excimer laser (Group B) were reviewed. Manifest refraction, uncorrected and best spectacle-corrected visual acuity (BSCVA), corneal topography and central corneal thickness (CCT) were recorded before and 3 months after treatment. Pre- and postoperative complications, visual and refractive outcome and frequency of retreatments were registered.

RESULTS

Mean preoperative spherical equivalent refraction was -8.52 dioptres (-5.50- -18 dioptres), and the mean attempted laser correction was -8.02 dioptres (-5.50- -11 dioptres). Three months after LASIK, the average treatment error (difference between achieved and attempted correction) was 1.20 (SD=1.19) dioptres of under correction in Group A and 0.52 (SD=1.00) dioptres in Group B. Four eyes lost more than two lines of BSCVA (0.6%). In 110 eyes (16%), a re-LASIK procedure was performed to reduce remaining myopia after the primary procedure.

CONCLUSIONS

Laser in situ keratomileusis treatment for high myopia can effectively reduce high degrees of myopia. Under correction was observed in both treatment groups but Group B has a slightly better predictability. Significant loss of BSCVA occurs infrequently after LASIK for even considerable grades of myopia (0.6% in each group).

Efficacy of laser in situ keratomileusis in correcting anterior and non-anterior corneal astigmatism: comparative study

PURPOSE

To compare the efficacy of conventional laser in situ keratomileusis (LASIK) in treating corneal astigmatism and in treating noncorneal ocular residual astigmatism.

SETTING

Private practice, Nashville, Tennessee, USA.

DESIGN

Retrospective case series.

METHODS

The records of dominant eyes of consecutive patients who had LASIK were retrospectively analyzed to compare the efficacy of LASIK in eyes with predominantly anterior corneal astigmatism with the efficacy in eyes with predominantly ocular residual astigmatism (ORA). The ORA was determined by vector analysis using refractive cylinder and topographic astigmatism. Preoperatively, the ratio of ORA to preoperative refractive cylinder (R) was used to divide the patients into 2 groups; that is, eyes with predominantly anterior corneal astigmatism (ORA/R ratio <1.0) and eyes with predominantly ORA (ORA/R ratio ≥1.0). Efficacy was determined by examining the magnitude of the remaining uncorrected astigmatism and comparing the index of success (proportion of preoperative refractive astigmatism that remained uncorrected by LASIK) between the 2 groups.

RESULTS

The study evaluated 61 eyes of 61 patients. Conventional LASIK was twice as efficacious in the low-ORA group as in the high-ORA group. The index of success was 0.24 and 0.50, respectively, and the difference between groups was statistically significant (P = .036).

CONCLUSION

The efficacy of astigmatic correction by LASIK was significantly higher in eyes in which the preoperative refractive astigmatism was located mainly on the anterior corneal surface than in eyes in which it was mainly located posterior to the anterior corneal surface.

Variables affecting refractive outcome following LASIK for myopia

AIM

To investigate factors affecting refractive outcome following LASIK for myopia.

METHOD

Six hundred and seventy-four consecutive uncomplicated myopic LASIK surgeries, performed by a single surgeon, either using the Technolas 217 planoscan (n=372) or the NIDEK EC 5000 (n=302), were evaluated. Stratified random sampling was used to match the groups for refractive error, patient age, and gender. The final analysis included 302 patients from each treatment group. Conditions were identical for both surgeries, and pre-operative refractive errors were between -1.00 and -14.00 DS and <-1.50 DC. Refractive success was defined as -0.50 to +0.50 DS of the targeted refraction measured 3 months after surgery. A stepwise logistical regression analysis was used to determine variables associated with refractive failure.

RESULTS

A successful refractive outcome was achieved in 78% (235/302) of surgeries using the Technolas laser and in 88% (266/302) using the NIDEK laser. Predictor variables for not achieving refractive success were pre-operative refractive error of above -5.00 DS, age more than 40 years, and surgery performed with the Technolas laser.

CONCLUSION

Both the Technolas 217 and the NIDEK EC-5000 excimer lasers achieve a successful refractive outcome in the majority of cases. However, patient and surgical factors can influence refractive outcome.

Retreatment of LASIK

PURPOSE

To review the indications, techniques, and results of retreatment LASIK.

METHODS

Review of the literature and the authors' experience.

RESULTS

Patient selection is the key to successful LASIK enhancement. The enhancement procedure should generally be undertaken 3 months after the initial LASIK procedure. Relifting of the flap may be done easily within 1 year of previous LASIK surgery. A new LASIK flap is required in cases with previously complicated LASIK. LASIK retreatment by lifting the flap is an effective and safe procedure. Overall improvement is seen in uncorrected visual acuity (> or = 20/20 and > or = 20/40) and postoperative spherical equivalent refraction within +/- 0.5 D and +/- 1.0 D.

CONCLUSIONS

LASIK retreatment is an effective modality to treat regressions and residual refractive errors.

Enhancement outcomes after photorefractive keratectomy and laser in situ keratomileusis using topographically guided excimer laser photoablation

PURPOSE

To evaluate the efficacy and safety of topographically guided excimer laser photoablation to retreat unsuccessful myopic and hyperopic photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Eye Clinic, San Salvatore Hospital, University of L'Aquila, L'Aquila, Italy.

METHODS

At least 3 months after primary PRK (Group A) or primary LASIK (Group B), 48 eyes of 42 patients were submitted to PRK or LASIK enhancements. The eyes were treated with an excimer laser linked to a computerized videokeratography unit with a topographically supported customized ablation workstation.

RESULTS

The mean follow-up was 27.8 months +/- 8.2 (SD). In Group A, the uncorrected visual acuity (UCVA) changed from 0.5 +/- 0.7 logarithm of the minimum angle of resolution (logMAR) (range 20/600 to 20/200) to 0.1 +/- 0.7 logMAR (range 20/60 to 20/20); the mean best spectacle-corrected visual acuity (BSCVA) changed from 0.1 +/- 0.7 logMAR (range 20/50 to 20/20) to 0 +/- 0.7 logMAR (range 20/50 to 20/20) after the enhancement. In Group B, the UCVA changed from 0.7 +/- 0.8 logMAR (range 20/600 to 20/40) to 0.1 +/- 0.7 logMAR (range 20/40 to 20/20); the mean BSCVA improved from 0.2 +/- 0.8 logMAR (range 20/30 to 20/20) to 0 +/- 1.3 logMAR (range 20/25 to 20/20) after surgery.

CONCLUSIONS

The enhancements using topographically guided excimer laser photoablation with a topographically supported customized ablation method resulted in satisfactory and stable visual outcome with good safety and efficacy after unsuccessful PRK and LASIK.

Laser in situ keratomileusis for refractive error after cataract surgery

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) to correct refractive error following cataract surgery.

SETTING

The Eye Institute, Sydney, Australia.

METHODS

This retrospective study reviewed 23 eyes (19 patients; 10 female, 9 male) treated with LASIK for refractive error following cataract surgery. The Summit Apex Plus and Ladarvision excimer laser and the SKBM microkeratome were used. The mean age was 63.5 years (range 50 to 88 years). The mean length of follow-up was 8.4 months (range 1 to 12 months) and mean interval between cataract surgery and LASIK was 12 months (range 2.5 to 46 months).

RESULTS

The mean preoperative spherical equivalent refraction (SEQ) for myopic eyes was -3.08 +/- 0.84 diopters (D) (range -4.75 to -2.00 D) and for hyperopic eyes was +1.82 +/- 1.03 D (range +0.75 to +3.00 D). The mean improvement following LASIK surgery was greater for myopic than hyperopic eyes (myopic, 2.54 +/- 1.03 D versus hyperopic, 1.73 +/- 0.62 D; P=.033). The percentage of patients within +/-0.5 D of intended refraction post-LASIK surgery was 83.3% for myopic eyes and 90.9% for hyperopic eyes and all eyes were within +/-1.0 D of intended (P<.001). The percentage of eyes with uncorrected visual acuity of 20/40 or better in the myopic group improved from none preoperatively to 91.7% postoperatively (P<.001) and in the hyperopic group improved from 27.3% preoperatively to 90.9% postoperatively (P=.008). No eyes lost 2 or more lines of best corrected visual acuity.

CONCLUSION

Laser in situ keratomileusis appears to be effective in correcting refractive error following cataract surgery. Longer-term studies are required to determine refractive stability.

Factors Influencing the Need for Enhancement After Laser in situ Keratomileusis

PURPOSE

To confirm that enhancements after primary laser in situ keratomileusis (LASIK) are effective in dealing with residual refractive errors, and to determine if any variables prior to or during the primary LASIK procedure predisposed eyes to require subsequent enhancement.

METHODS

A retrospective study of eyes undergoing primary LASIK with the VISX S2 or S3 laser and Hansatome microkeratome between January 1, 2000 and January 1, 2002 was done. Of the 393 eyes of 207 patients, 58 eyes (14%) underwent enhancement within a 16-month window of the primary procedure. Statistical comparisons were made between enhanced (n = 37) and non-enhanced (n = 148) patients, and enhanced (n = 48) and non-enhanced (n = 303) eyes, treated for myopia only.

RESULTS

In comparing the primary LASIK parameters of enhanced to non-enhanced eyes in myopic patients, no significant difference was found in right vs left eye, season of the primary treatment, preoperative astigmatism, pachymetry, or amount of attempted astigmatism correction. A multivariate logistic regression analysis revealed that male gender, patient age over 45 years, and a history of recent rigid contact lens use within 6 months of primary LASIK were significantly associated with the need for enhancement.

CONCLUSION

Enhancements were an effective way of dealing with residual refractive errors after primary LASIK. Age greater than 45 years or a history of recent rigid contact lens use were significantly associated with the need for enhancement in patients with myopia or myopic astigmatism.

Peripheral corneal relaxing incisions after excimer laser refractive surgery

PURPOSE

To evaluate the effectiveness of peripheral corneal relaxing incisions (PCRIs) for correcting corneal astigmatism after excimer laser refractive surgery.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

METHODS

In this retrospective case series, PCRIs were performed in 33 eyes (30 patients) that had residual astigmatism after photorefractive keratectomy or laser in situ keratomileusis according to a nomogram based on age and preoperative refractive astigmatism. Uncorrected visual acuity (UCVA) and refractive and keratometric astigmatism were evaluated, and vector analysis using the Holladay-Cravy-Koch formula was performed.

RESULTS

The percentage of eyes with a UCVA of 20/20 or better increased significantly from 6% (2/33) preoperatively to 61% (20/33) postoperatively (P<.001). Refractive astigmatism was reduced significantly, and the effect was stable up to 1 year after PCRIs. The percentage of eyes within +/-0.5 diopter (D) and +/-1.0 D of cylinder increased by 73% and 52%, respectively (both P<.001). No eye lost 1 or more lines of best spectacle-corrected visual acuity.

CONCLUSION

Peripheral corneal relaxing incisions are an effective approach for correcting low amounts of corneal astigmatism in eyes that have had excimer laser refractive surgery.

Incidence and associations of retreatment after LASIK

PURPOSE

To determine the incidence and risk factors for laser in situ keratomileusis (LASIK) retreatment and to present a novel retreatment technique.

DESIGN

Retrospective noncomparative consecutive case series.

PARTICIPANTS

Two thousand four hundred eighty-five eyes (1306 patients) underwent LASIK surgery for myopia, hyperopia, or astigmatism using either the Summit Apex Plus or the Alcon LADARVision excimer laser systems. Only retreatments for residual refractive error were included.

MAIN OUTCOME MEASURES

Prevalence and incidence of retreatments were determined. Potential risk factors for retreatment, including age, gender, and attempted correction, were assessed. Refractive error and a ratio of residual sphere to cylinder in retreated eyes were also analyzed.

RESULTS

Of the total cohort studied, 288 eyes of 233 patients underwent one retreatment, and 3 eyes of 3 patients required two retreatment procedures. The overall 1-year incidence of retreatment was 10.5%. The average length of time between initial treatment and enhancement was 7.3 +/- 6.4 months; 85% of retreatments took place within 1 year. Two hundred eighty-five of the 288 retreatments were accomplished using a manual flap lift approach; 3 eyes required a repeat microkeratome cut. Higher initial corrections and residual astigmatism were associated with a significantly higher rate of retreatment. Patients older than 40 years were at greater risk for retreatment. There was no gender difference.

CONCLUSIONS

Higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment. Most LASIK flaps can be lifted using the manual technique described up to 3 years after initial surgery.

Undersurface ablation of the flap for laser in situ keratomileusis retreatment

OBJECTIVE

To develop a novel technique, undersurface ablation of the flap (UAF), for laser in situ keratomileusis (LASIK) retreatment in eyes with insufficient posterior stroma.

DESIGN

Noncomparative, interventional case series.

PARTICIPANTS

From 30 eyes examined, 25 eyes with a spherical equivalent residual refraction between -0.75 and -3.25 diopters (D) and astigmatism between 0.0 and -1.5 D were prospectively included in the study. In these eyes, calculated postenhancement flap thickness was >150 micro m using micropachymetric optical coherence tomography (OCT), whereas with further ablation of the bed, posterior stromal thickness would have been <250 micro m. Primary LASIK procedures had been performed with the Hansatome microkeratome.

INTERVENTION

The flap was lifted and the eye deviated downward, so that the corneal visual axis mark aligned with the laser beam. Mirror pattern ablations with an optical zone of 5 mm were performed on the flap stroma using either the Summit Apex Plus excimer laser or the Technolas Keracor 217 spot-scanning excimer laser. New axis orientation for toric ablations was calculated with the formula: beta = 180 degrees - alpha.

MAIN OUTCOME MEASURES

Refraction, visual acuity, OCT pachymetry, tangential videokeratography, and patient satisfaction.

RESULTS

The average follow-up was 6.36 +/- 2.64 months (range, 3-12 months). Mean preenhancement spherical equivalent (-2.05 +/- 0.75 D) was reduced to -0.19 +/- 0.38 D at the last visit (P = 0.001). Mean cylinder decreased from -0.48 +/- 0.53 D before retreatment to -0.23 +/- 0.28 D at the last follow-up (P = 0.003). Best-corrected visual acuity worsened by 1 line in two eyes (8%), and no eye lost 2 or more lines. Satisfactory globe stabilization and stromal smoothness during ablation were more difficult to achieve than with conventional LASIK enhancements. The average central flap thickness before UAF, 187 +/- 13 micro m, decreased to 164 +/- 12 micro m after 1 month (P = 0.001). No keratectasia developed. Finally, 92% of cases were satisfied with surgery compared with 48% before UAF retreatment (P = 0.001).

CONCLUSIONS

UAF retreatment for low residual refractive errors after LASIK in eyes with sufficient flap stroma seems to be effective and may prevent future keratectasia.

Astigmatism and LASIK

Although laser in situ keratomileusis (LASIK) enjoys a high success rate, postoperative residual or induced astigmatism may limit uncorrected visual acuity and cause starbursts and glare at night. Irregular astigmatism can also cause loss of best-corrected visual acuity, monocular diplopia, and ghosting of images. Astigmatism may be measured by keratometry and refraction, while corneal topographic techniques help to define irregular astigmatism, in particular. Further information may be obtained regarding induced higher-order aberrations with aberrometry. Because astigmatism has both direction and magnitude, its analysis is more complex than that of the spherical component of the treatment. There are multiple approaches to the analysis of surgically induced astigmatism, including vector analysis, conversion to a Cartesian coordinate system, matrix formalism, and linear optics. Both excimer laser and incisional techniques may be used to correct astigmatism after LASIK, but the treatment of irregular astigmatism requires selective zonal ablation techniques or customized corneal ablations, using topographic or wavefront derived data.

Laser in situ Keratomileusis for Correction of High Astigmatism After Penetrating Keratoplasty

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) for correction of high astigmatism after penetrating keratoplasty, and to assess the refractive results and predictability of the procedure.

METHODS

LASIK was performed on 19 patients (19 eyes) with high astigmatism after penetrating keratoplasty, using the Chiron Automated Corneal Shaper and the Chiron-Technolas Keracor 116 excimer laser. The amount of preoperative refractive astigmatism ranged from 6.50 to 14.50 D (mean, 9.21 +/- 1.95 D) and the spherical component of manifest refraction ranged from -7.00 to +1.25 D (mean, -2.14 +/- 2.11 D). All patients completed a minimum follow-up of 12 months.

RESULTS

Refraction was stable after 3 months. At 1 year after LASIK, the amount of refractive astigmatism was reduced to a mean of 1.09 +/- 0.33 D (range, 0.50 to 1.75 D), with 57.9% of the eyes within +/- 1.00 D of refractive astigmatism. The mean percent reduction of astigmatism was 87.9 +/- 3.7%. The postoperative spherical component of manifest refraction ranged from -1.00 to +1.75 D with a mean of +0.43 +/- 0.82 D. Vector analysis showed that the mean amount of axis deviation was 1.1 +/- 1.3 degrees and the mean percent correction of preoperative astigmatism was 92.6 +/- 8.4%. There were no intraoperative complications. Spectacle-corrected visual acuity was not reduced in any eye, and improved by 2 or more lines in 42.1% of eyes after LASIK.

CONCLUSION

LASIK with the Chiron-Technolas Keracor 116 excimer laser was effective for correction of both astigmatism and myopia after penetrating keratoplasty. The procedure proved to be safe and gave fairly predictable and stable refractive results.