Excimer laser photorefractive keratectomy for high myopia and myopic astigmatism.

BACKGROUND AND OBJECTIVE: To determine the efficacy, safety, and predictability of excimer laser photorefractive keratectomy of high myopia and myopic astigmatism. PATIENTS AND METHODS: 76 eyes of 52 patients with myopia from -8.00 to -23.50 diopters (D) with or without astigmatism up to -5.50D were treated with the VISX 20/20 excimer laser (VISK, Santa Clara, CA) and a multi-zone ablation technique. Visual acuity, manifest refraction, corneal haze, and topography were evaluated at 1 week and 1, 3, 6, 12, and 18 months postoperatively. RESULTS: Postoperative refractions were generally stable after 12 months. At the last follow-up all patients were within - 1.96 D of the intended correction. Eighteen months postoperatively, 68% of patients undergoing photorefractive keratectomy (PRK), and 65% of patients undergoing photo astigmatic refractive keratectomy (PARK), were within 1 D of planned refraction. Furthermore, 87% of patients after PRK and 80% of patients after PARK had a visual acuity of 20/40 or better. CONCLUSIONS: High myopia with or without astigmatism was successfully treated in most of the patients using PRK. The stability of the postoperative refraction during the first 18 months seems to be good. The incidence of adverse effects was low but improvements in the future should further reduce complications, thus increasing the safety of refractive procedures.     

Surgically induced astigmatism after hyperopic and myopic photorefractive keratectomy

PURPOSE: To compare the axis and magnitude of surgically induced refractive astigmatism (SIA) after hyperopic and myopic photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: In this single-center retrospective study, the VISX Star S2 excimer laser was used to create a peripheral annular ablation profile to correct spherical hyperopia in 23 eyes of 16 consecutive patients. Attempted corrections ranged from +0.50 diopter (D) to +4.25 D with 0 to 1.00 D of astigmatism. The same laser was used to create a central ablation profile to correct spherical myopia in 25 eyes of 17 consecutive patients. Attempted corrections ranged from -2.25 to -6.50 D with 0 to 1.00 D of astigmatism. The absolute change in refractive astigmatism was calculated by taking the difference in magnitudes of astigmatism before and after laser treatment without regard to axis. Axis and magnitude of SIA were analyzed by vector differences. Magnitudes were compared using the Student t test, and axial shifts were compared using the chi-square test. All patients were followed for a minimum of 6 months. RESULTS: The mean changes in absolute astigmatism were 0.29 +/- 0.28 D at 3 months and 0.34 +/- 0.29 D at 6 months after hyperopic PRK and 0.40 +/- 0.35 D at 3 months and 0.39 +/- 0.36 D at 6 months after myopic PRK. The mean vectoral magnitudes were 0.49 +/- 0.29 at 3 months and 0.52 +/- 0.25 at 6 months after hyperopic PRK and 0.48 +/- 0.39 at 3 months and 0.44 +/- 0.38 at 6 months after myopic PRK. The mean values for SIA (the centroid) were 0.10 +/- 0.57 D x 113 degrees at 3 months and 0.15 +/- 0.57 D x 131 degrees at 6 months after hyperopic PRK and 0.04 +/- 0.63 D x 160 degrees at 3 months and 0.08 +/- 0.58 D x 171 degrees at 6 months after myopic PRK. There was no statistically significant difference between the 2 groups in vectoral axis or magnitude of SIA. CONCLUSION: Surgically induced astigmatism after hyperopic PRK was comparable to astigmatism induced by myopic PRK. A peripheral annular ablation for hyperopic correction, similar to a central ablation in myopic PRK, did not appear to result in uneven corneal healing causing astigmatism.     

Excimer laser retreatment of residual myopia following photoastigmatic refractive keratectomy for compound myopic astigmatism

PURPOSE: To prospectively evaluate the safety, efficacy, and visual performance of excimer laser enhancement following photoastigmatic refractive keratectomy (PARK) with the Summit Apex Plus. SETTING: Stanford University School of Medicine Eye Laser Clinic, Stanford, California, USA. METHODS: As part of a Food and Drug Administration clinical trial, 93 eyes of 56 patients with a mean spherical equivalent (SE) of -4.98 diopters (D) +/- 1.80 (SD) (range -1.75 to -8.50 D) had PARK for compound myopic astigmatism using the Summit Apex Plus excimer laser and a poly(methyl methacrylate) erodible mask. Seventeen eyes with a mean SE of -2.08 +/- 0.76 D required excimer laser refractive keratectomy for residual spherical myopia or compound myopic astigmatism. Patients were prospectively followed 1, 3, 6, 9, and 12+ months after the enhancement procedure. Primary outcome variables included uncorrected visual acuity (UCVA), refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA) under standard ambient conditions (photopic, scotopic, and glare), corneal clarity, and contrast sensitivity function curve under photopic and scotopic conditions. RESULTS: At the last postoperative visit, the mean sphere had been corrected 82% to a residual of -0.29 +/- 1.23 D and mean SE had been corrected 65% to a residual of -0.74 +/- 1.27 D. Eighty-two percent of eyes were within +/-1.0 D of attempted correction. Eighty-eight percent had a UCVA of 20/40 or better. Vector analysis demonstrated a difference vector of within +/-1.0 D in 75% of eyes that had PARK retreatment. There was no significant loss in the contrast sensitivity curve. Late regression associated with corneal haze and loss of BSCVA occurred in 2 eyes (11.7%). CONCLUSIONS: Retreatment following PARK for compound myopic astigmatism results in effective reduction in residual spherical myopia and compound myopic astigmatism. An improvement in UCVA without loss of contrast sensitivity can be expected in most eyes. However, regression, corneal haze, and loss of BSCVA may occur. Further studies are indicated to predict risk factors for these complications.     

Eight-year follow-up of photorefractive keratectomy for myopia

PURPOSE: We evaluated 8-year results of excimer laser photorefractive keratectomy (PRK) for myopia in terms of stability and late complications. METHODS: Ninety-two myopic eyes of 55 patients were treated with a single-step method using an Aesculap-Meditec MEL 60 excimer laser with a 5.0-mm ablation zone. Treated eyes were divided into three groups according to preoperative refraction: low myopes (< or = -6.00 D), medium myopes (-6.10 to -10.00 D), and high myopes (>-10.00 D). RESULTS: Change in myopic regression stabilized in all myopia groups within 12 months, although a small myopic shift occurred up to 8 years after PRK. Mean change in refraction between 2 and 8 years was -0.42 +/- 0.48 D for low myopes, -0.37 +/- 0.34 D for medium myopes, and -0.41 +/- 0.50 D for high myopes. The percentage of eyes within +/- 1.00 D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the medium myopia group, and 57.1% in the high myopia group. One eye lost 2 lines of best spectacle-corrected visual acuity due to irregular astigmatism. In 13.0% of eyes, a residual trace corneal haze was observed, which had no effect on visual acuity. Apart from the loss of 2 lines of BSCVA in one eye, there were no other late complications during the study period. CONCLUSIONS: The mean change in refraction between 2 and 8 years was less than -0.50 D, regardless of preoperative refraction, and may be attributed to natural age-related refractive change. The appearance of residual corneal haze after 8 years correlated with the amount of myopic correction. PRK was a safe and stable surgical procedure in this group of patients.     

Photoastigmatic refractive keratectomy for low, moderate, and high astigmatism using a broad beam excimer laser: evaluataion according to new international criteria

BACKGROUND: Photorefractive keratectomy (PRK) is an accepted procedure to correct myopia in Germany. The purpose of this study was to evaluate photoastigmatic refractive keratectomy (PARK) for myopic astigmatism. MATERIAL AND METHODS: PARK using the VISX 20/20 excimer laser was performed in 50 eyes of 36 patients (25 female, 16 male) aged 22 to 68 years (mean 38 +/- 10 years) in the period of 1995 to 1996. Retrospective evaluation was done after dividing the patients into three astigmatic groups between -0.5 diopters (D) and -1.5 D (group I, n = 28), between -1.75 D and -3.0 D (group II, n = 16) und between -3.25 D and -5.5 D (group III, n = 6). The correction of myopic astigmatism was assessed concerning the criteria safety, efficacy, predictability and stability. Mean follow-up was 12 months (8-15 months). RESULTS: Seventy-eight % of all eyes achieved an uncorrected visual acuity of > 0.5. Sixty-eight % of the eyes were within +/- 1.0 D of the desired correction. Loss of 2 or more lines of best corrected visual acuity occurred in 6 eyes (12.0%). We observed in group I an astigmatic reduction of 36.0%, in group II of 66.5% and in group III of 68.0%. The surgically induced astigmatism was calculated with 1.29 +/- 1.0 D. Mean axis rotation of the refractive cylinder was 22.12 +/- 23.05 degrees. CONCLUSIONS: PARK using the VISX 20/20 excimer laser is an acceptable procedure to correct myopic astigmatism. However, the study revealed that astigmatic reduction with a broad beam laser is not yet perfect in terms of efficacy, predictability and safety.     

Correlation among refractive, keratometric and topographic astigmatism after myopic photorefractive keratectomy

BACKGROUND: Photorefrative keratectomy can be used to flatten the curvature of the anterior cornea and reduce the myopic refraction of the eye. This leads to unphysiological topographical changes of the cornea and may alter the conditions for examinations of corneal surface topography. The purpose of this study was to check for mutual agreement of three different methods of assessment of astigmatism before and after myopic photorefractive keratectomy (PRK). PATIENTS AND METHODS: Forty-seven eyes of 28 patients (age 32.7+/-6.6 years) following PRK using an 193-nm excimer laser were included in this study. 37 eyes were treated for pure myopia (-4.9+/-2.4 D) and 10 eyes for myopic astigmatism (sphere -2.0 to -7.0 D, cylinder -1.0 to -3.0 D). Preoperatively and at 18 months postoperatively, subjective refractometry, keratometry and topography analysis were performed. The axes of topographic and keratometric cylinder were standardized periodically (180 degrees) with respect to the refractive cylinder axis. RESULTS: Pre- and postoperatively, the absolute astigmatism values correlated highly significantly between all three methods (P< or =0.001). The mean refractive cylinder was 0.65+/-0.61 D preoperatively and 0.46+/-0.41 D postoperatively (P=0.2). The mean keratometric astigmatism was 1.14+/-0.64 D before and 0.94+/-0.50 D after PRK treatment (P=0.2). Among the three methods, the mean topographic astigmatism was the highest (P<0.001) preoperatively (1.31+/-0.56 D) and postoperatively (1.21+/-0.52 D) (P=0.3). In eyes treated for pure myopia, no difference between pre- and postoperative refractive, keratometric and topographic astigmatism was detected (P>0.5). The axes of both topographic and keratometric astigmatism correlated highly significantly with the refractive cylinder axis (R> or =30.9, P<0.0001). CONCLUSION: Up to 2 years after myopic PRK, the difference between refractive and keratometric astigmatism does not differ from the preoperative value, indicating an even corneal surface. The absolute astigmatism values and the cylinder axis correlated well between subjective and objective methods of astigmatism assessment. Thus, objective measurements may be helpful in determining the cylinder component of best spectacle correction after PRK. However, topographic analysis overestimates astigmatism values systematically before and after PRK.     

Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism

PURPOSE: To determine the safety, effectiveness, and predictability of photorefractive keratectomy (PRK) for the correction of myopia and astigmatism after penetrating keratoplasty. SETTING: Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. METHODS: Photorefractive keratectomy was performed in 16 eyes of 16 patients with postkeratoplasty myopia and astigmatism who were unable to wear glasses due to anisometropia and were contact lens intolerant. They were examined for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and corneal transplant integrity before and after surgery. RESULTS: The mean follow-up after PRK was 26.0 months +/- 15.7 (SD) (range 12 to 63 months). The mean preoperative spherical equivalent refraction of -4.47 +/- 1.39 diopters (D) was -3.39 +/- 1.84 D (P >.05) at the last postoperative visit and the mean preoperative cylinder of -5.62 +/- 2.88 D was -3.23 +/- 1.70 D (P <.05); refractive regression correlated with the amount of ablation performed. The BSCVA decreased in 3 eyes (18.8%), and the UCVA decreased in 2 (12.5%). Six eyes (37.5%) had grade 2 to 3 haze, which resolved spontaneously in 4 eyes within a relatively long time but caused a decrease in BSCVA in 2 (12.5%). Two of the eyes (12.5%) had a rejection episode after PRK and were successfully treated with topical steroids. CONCLUSIONS: Photorefractive keratectomy to correct postkeratoplasty myopia and astigmatism appears to be less effective and less predictable than PRK for naturally occurring myopia and astigmatism. Corneal haze and refractive regression are more prevalent, and patient satisfaction is not good.     

Predictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser

PURPOSE: To evaluate the effect of astigmatic correction on the accuracy of the myopic and astigmatic correction in patients having photorefractive astigmatic keratectomy (PARK) and in those having photorefractive keratectomy (PRK). SETTING: Specialist excimer laser refractive clinic. METHODS: This prospective consecutive case series comprised 6097 eyes with a preoperative mean spherical equivalent (MSE) of -4.63 diopters (D) +/- 1.95 (SD) (range -0.75 to -13.00 D) and a mean cylinder of -1.13 +/- 0.73 D (range -0.50 to -6.00 D) having PARK with a Nidek EC-5000 excimer laser. Visual and refractive outcomes were assessed 12 months postoperatively and compared with those in 3004 eyes that had spherical PRK. RESULTS: At 12 months, the MSE was -0.02 +/- 0.79 D and the mean cylinder was -0.49 +/- 0.47 D in the PARK group; the MSE was -0.07 +/- 0.66 D in the PRK group. An MSE within +/-0.05 D of emmetropia was achieved by 69.8% and within +/-1.00 D, by 87.9%. The uncorrected visual acuity (UCVA) was 20/20 or better in 42.6% and 20/40 or better in 91.2%. Statistical significance (P <.001, analysis of variance) was achieved for MSE, sphere, cylinder, haze, and visual acuity (best corrected [BCVA] and UCVA) based on the preoperative cylinder. The loss of BCVA varied from 1.1% to 5.8% depending on the degree of astigmatism treated. Accuracy varied with the attempted myopic correction and the attempted astigmatic correction. CONCLUSIONS: Excimer laser PARK was an effective treatment for compound myopic astigmatism, but predictability decreased and complications increased as the attempted astigmatic correction increased.     

Photorefractive keratectomy with aspheric profile of ablation versus conventional photorefractive keratectomy for myopia correction: six-month controlled clinical trial

PURPOSE: To analyze ocular wavefront error and corneal asphericity (Q) in patients treated with aspheric profile photorefractive keratectomy (PRK) compared with patients having conventional PRK to correct myopia and myopic astigmatism and to evaluate the effect of postoperative corneal shape on visual performance. SETTING: Eye Clinic, University G. d'Annunzio, Chieti-Pescara, Italy. METHODS: Fifty eyes were treated with aspheric profile PRK using the MEL 80 flying-spot excimer laser, and 24 eyes were treated with standard PRK using the MEL 70 flying-spot excimer laser. RESULTS: Postoperative wavefront error increased in both groups. Six months after surgery, there was a smaller increase in root mean square (RMS) of total higher-order aberrations and spherical aberration (59% and 106%, respectively) in the aspheric profile PRK group than in the conventional PRK group (94% and 136%, respectively) (P<.01).The aspheric profile PRK group showed more prolate corneal asphericities (mean Q of 0.15 +/- 0.26) than the conventional group (mean Q of 0.45 +/- 0.26) (P<.001), with increasing oblateness for higher attempted corrections. A higher percentage of patients with better low-contrast uncorrected visual acuity and best corrected visual acuity was observed in the aspheric PRK group than in the conventional PRK group (P<.05). CONCLUSIONS: Aspheric profile and conventional PRK were safe and efficient for the correction of myopia and myopic astigmatism. Moreover, aspheric profile PRK induced a smaller increment of total wavefront error, was related to a smaller increase in spherical aberration, and better maintained the physiology of the corneal surface than conventional treatment.     

Laser in situ keratomileusis for the correction of myopia and myopic astigmatism

PURPOSE: To evaluate the efficacy, safety, predictability, and surgically induced astigmatism (SIA) of laser in situ keratomileusis (LASIK) for the correction of myopia and myopic astigmatism. SETTING: Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan. METHODS: This retrospective study comprised 69 eyes that had LASIK to correct myopia and 74 eyes that had LASIK to correct myopic astigmatism. The excimer laser keratectomy was performed using a Summit Apex Plus machine. Refraction, visual acuity, and computerized corneal videokeratography data from the preoperative and postoperative examinations were collected. The astigmatic change was calculated by the Alpins vector analysis method. RESULTS: The preoperative spherical equivalent at the glasses plane in the myopia and myopic astigmatism groups was -8.08 diopters (D) and -9.73 D, respectively. At 6 months, the spherical equivalent and residual corneal astigmatism were -0.25 D and 0.85 D, respectively, in the myopia group and -0.71 D and 0.82 D, respectively, in the myopic astigmatism group. In the myopia group, 88% of eyes were within +/-1.0 D of the intended myopia correction and in the myopic astigmatism group, 85% were within +/-1.0 D of the targeted spherical equivalent and 90% were within +/-1.0 D of the intended astigmatism correction. The uncorrected visual acuity was 20/40 or better in 94.1% of eyes in the myopia group and 92.5% of eyes in the myopic astigmatism group. The SIA magnitude was 0.66 D with the axis randomly distributed in the myopia group. The mean astigmatism correction index was 0.97, the mean magnitude of error was 0.13 D +/- 0.62 (SD), and the mean angle of error was -3.70 +/- 13.73 degrees in the myopic astigmatism group. CONCLUSION: Laser in situ keratomileusis had similar predictability, safety, and efficacy in the treatment of myopia and myopic astigmatism. The astigmatism correction was effective, but the results suggest that subjective astigmatism of less than 1.0 D need not be treated with the Summit Apex Plus laser.     

Prospective study of photorefractive keratectomy for myopia using the VISX StarS2 excimer laser system

PURPOSE: To evaluate the safety, efficacy, and predictability of excimer laser photorefractive keratectomy (PRK) for compound myopic astigmatism using the VISX StarS2 excimer laser system with international version 3.1 software. METHODS: We report a prospective consecutive study of myopic excimer laser PRK, performed in a multi-surgeon environment with 200 eyes of 117 patients, to correct naturally occurring compound myopic astigmatism of between -0.50 to -5.90 D manifest refractive sphere and up to -3.50 D manifest refractive astigmatism. Patients were assessed prior to surgery and at 1, 3, 6, and 12 months after treatment. RESULTS: One hundred and ninety-eight of 200 treatments (99%) were reviewed 1 year after surgery; 193 of 198 eyes (97%) achieved 20/40 or better uncorrected visual acuity and 163 of 198 eyes (82%) achieved 20/20 or better. One eye lost two lines of Snellen visual acuity assessed at 12 months but recovered acuity when assessed at 18 months. Mean spherical equivalent corneal plane power was reduced from -3.50 to +0.90 D 1 month after treatment and 0 D at 12 months (SD 0.67 D). Three eyes of three patients underwent further treatment, two with LASIK and one with PRK for residual refractive error. Refractive astigmatism of >1.00 D was reduced from a mean -1.70 to -0.70 D at 1 year after treatment. Vector magnitude was 79% of that intended and mean vector axis error (absolute) was 8.5 degrees. No eye had a severe haze response. Pelli-Robson contrast acuity was significantly reduced after treatment from a mean 1.72 D preoperatively to 1.63 D at 12 months (P<.01). CONCLUSIONS: PRK for myopia using the VISX StarS2 excimer laser system was effective in the treatment of low myopic astigmatism, although there was a significant reduction in Pelli-Robson contrast sensitivity.     

Correction of myopic astigmatism by combined treatment with PRK and T-incision and photoastigmatic refractive keratectomy

Background: In contrast to the correction of simple myopia there is no widely accepted technique for the correction of myopic astigmatism. Currently two techniques are available: the photoastigmatic refractive keratectomy (PARK) and the combination of arcuate keratotomies with standard PRK (PRK-T). Methods: In two groups, 67 patients underwent a correction of myopic astigmatism in a total of 87 eyes (19 by PRK-T and 68 by PARK), and were followed for 1 year. The spherical equivalent was − 6.7 D in both groups and the refractive astigmatism ranged from − 1.0 to − 6.5 D. The PARK procedure was performed by means of an elliptic ablation (Kertom I, Schwind) with a 5.8 × 8.1 mm zone. The PRK-T technique consisted of two arcuate keratotomies with a free optical zone of 7 mm and a standard myopic PRK at least 6 weeks later. Results: The 1 year follow-up was completed in 57 out of 87 eyes included in the study. At 1 year post-operation, 83 % of the PRK-T group and 80 % of the PARK group had an uncorrected visual acuity of 20/40 or better. The refractive astigmatism was reduced by 76 % in the PRK-T group and by 67 % in the PARK group. The spherical equivalent was − 0.59 ± 1.1 D at 1 year after PRK-T and − 0.28 ± 1.04 D after PARK. In three eyes of the PARK group (6.7 %) a visual loss of more than one Snellen line occured. Two of these eyes had a preoperative myopia of more than − 6 diopters. Conclusion: Both techniques have the potential to reduce myopic astigmatism, however, the success rate is not as high compared to spherical PRK. Also, the complication rate of 2.5 % in corrections to − 6 D is significantly higher than that with spherical myopic PRK.      

Photorefractive keratectomy for residual myopia after cataract surgery

PURPOSE: To evaluate the effectiveness, predictability, and safety of photorefractive keratectomy (PRK) for correcting residual myopia and myopic astigmatism after cataract surgery with intraocular lens implantation. SETTING: Refractive Surgery and Cornea Unit, Instituto Oftalmológico de Alicante, Alicante, Spain. METHODS: Thirty consecutive eyes (30 patients) had PRK for residual myopia after cataract surgery. Surface PRK with a VISX Twenty-Twenty excimer laser was used in all patients. Follow-up was 1 year. RESULTS: Before PRK, no eye had an uncorrected visual acuity (UCVA) of 20/40 or better. Twelve months after PRK, 16 eyes (53.33%) had a UCVA of 20/40 or better. After PRK, best corrected visual acuity (BCVA) improved 1 line or more in 14 eyes (46.66%) over the preoperative values, and 15 eyes (50.00%) had the same BCVA as before PRK. Mean pre-PRK refraction of -5.00 diopters (D) +/- 2.50 (SD) decreased significantly to -0.25 +/- 0.50 D at 12 months (P < .001). At 12 months, the spherical equivalent was within +/- 1.00 D of emmetropia in 27 eyes (90.00%). No vision-threatening complications occurred. CONCLUSION: Photorefractive keratectomy was an effective, predictable, and safe procedure for correcting residual myopia and myopic astigmatism after cataract surgery.     

Wavefront-supported photorefractive keratectomy: 12-month follow-up

PURPOSE: To evaluate safety, efficacy, predictability, and stability of wavefront-supported photorefractive keratectomy (PRK) for correction of myopia and myopic astigmatism, with 12-month follow-up. METHODS: Thirty eyes of 23 patients with myopia less than -8.00 D (mean -3.76 +/- 1.90 D) and cylinder less than -3.50 D (mean -0.81 +/- 0.71 D) were selected. Aberrometry measurements were taken with the Asclepion aberrometer in order to perform customized wavefront-supported PRK. Eyes were treated with the Asclepion MEL 70 excimer laser and were followed for 12 months. RESULTS: UCVA of 20/16 or better was achieved by 47% (14 eyes) at 1 month, 67% (20 eyes) at 3 months, 77% (23 eyes) at 6 months, 90% (27 eyes) at 9 months, and 83% (25 eyes) after 1 year. No eye lost more than 1 line of BSCVA at 3, 6, 9, or 12 months. Two eyes (7%) gained more than 2 lines 1 month postoperatively, and 13% (4 eyes) gained more than 2 lines at 6, 9, and 12 months postoperatively. BSCVA of 20/10 or better was achieved in nine eyes (30%) at 1 and 12 months. Visual acuity under low contrast at 3 and 12 months after PRK was unchanged in 87% (26 eyes). Visual acuity under glare remained unchanged at 3 months after PRK in 86% (26 eyes) and at 12 months in 83% (25 eyes). CONCLUSION: Excimer laser wavefront-supported PRK with the Asclepion MEL 70 laser was safe and effective for the treatment of myopia and myopic astigmatism. Daylight visual acuity and mesopic visual acuity outcomes remained stable over 1 year.     

Bioptics by angle-supported phakic lenses and photorefractive keratectomy

PURPOSE: To assess efficacy and safety of the combination of angle-supported phakic intraocular lenses (IOLs) and photorefractive keratectomy (PRK) for the correction of myopia and astigmatism. METHODS: Prospective, non-randomized single-surgeon study on 48 patients (76 eyes) undergoing angle-supported phakic IOL implantation with surgical peripheral iridectomy, followed 2 to 3 months later by PRK to correct residual refractive error. Twenty-three patients (33 eyes) achieved good uncorrected visual acuity with IOL implantation alone and did not undergo PRK. Thus, the study was completed by 25 patients (43 eyes) with preoperative mean defocus equivalent (DEQ) of 15.73 D (SD 4.67 D) and mean astigmatism of -2.87 D (SD 1.39 D). RESULTS: Eight months after PRK, mean spherical equivalent was -0.08. Mean DEQ was 0.47 D (SD 0.37); 42/43 eyes (98%) were within +/-1 D of DEQ, and 33/43 eyes (77%) within +/-0.5 D. Mean uncorrected visual acuity was 0.7 (SD 1.9). Safety index was 1.25; efficacy index 1.11. Best-corrected visual acuity improvement (0.16) was statistically significant (95% CI: 1.1 to 2). Halos were moderate in 6/25 patients (24%); severe in 1/25 patients (4%). Endothelial cell density decreased by -6.6%. Pain after PRK was severe in 3/25 patients (12%) and moderate in 13/25 patients (52%). Complications were recurrent iridocyclitis in one eye, transient ocular hypertension in two eyes, and incomplete iridectomy in one eye. CONCLUSIONS: Angle-supported phakic IOLs followed by adjustment by PRK offer good efficacy, predictability, and safety to manage large refractive myopic errors.     

Photorefractive keratectomy or laser in situ keratomileusis for residual refractive error after phakic intraocular lens implantation

PURPOSE: To evaluate the results of combining phakic posterior chamber intraocular lens (IOL) implantation and excimer corneal surgery to treat high myopia or myopia with astigmatism. SETTING: Service d'Ophtalmologie, H?pital Purpan, University of Toulouse, Toulouse, France. METHODS: Thirty-two eyes of 28 patients with extreme myopia or myopia combined with astigmatism were treated by implantation of a phakic posterior chamber IOL. Residual refractive errors were treated no earlier than 6 weeks after IOL implantation by photorefractive keratectomy (PRK) in eyes with low refractive errors or by laser in situ keratomileusis (LASIK) in eyes with higher residual refractive errors. RESULTS: The mean preoperative spherical equivalent (SE) refraction was -18.7 diopters (D). The refractive astigmatism ranged from 0 to 3.5 D. After excimer laser treatment, the SE refraction ranged from -0.5 to -2.5 D and the refractive astigmatism, from 0 to 1.5 D in the PRK group. In the LASIK group, spherical ametropia ranged from -1.5 to +1.5 D and astigmatism, from 0 to 1.0 D. After excimer laser treatment, the uncorrected visual acuity improved in all eyes but a loss of 1 line of the corrected vision after IOL implantation occurred in 22.2% of PRK-treated eyes and in 13.6% of LASIK-treated eyes. CONCLUSIONS: Bioptic treatment of extreme myopia and myopia associated with astigmatism appears to be safer and more predictable than other methods of treatment.     

准分子激光屈光性角膜切削术矫正散光的准确性及预测性

目的 探讨准分子激光屈光性角膜切削术（ｅｘｃｉｍｅｒ ｌａｓｅｒ ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅ ｋｅｒｅｃｔｏｍｙ,ＰＲＫ）矫正散光的准确性及预测性。方法 根据角膜地形图提供的角膜屈光力数值,用Ｈｏｌｌａｄａｙ法计算复性近视散光３０例（５３只眼）和单纯近视２３例（３３只眼）患者术前与术后６个月角膜屈光力的差值,确定实际矫正散光度及轴位,及预期矫正散光度及轴位进行对比分析。结果 复性近视散光组５３     

Photorefractive keratectomy for compound myopic astigmatism with the MEL-70 G-Scan excimer laser

PURPOSE: To assess the safety, efficacy, predictability and stability of photorefractive keratectomy in compound myopic astigmatism with a moderate and high cylinder component. METHODS: Photorefractive keratectomy was done in 42 eyes with compound myopic astigmatism with the spherocylindrical algorithm of the MEL-70 excimer laser, with wide ablation zones. RESULTS: Spherical equivalent refraction changed from -4.19 +/- 1.65D to -0.05 +/- 0.31D, refractive cylinder from -2.01 +/- 0.71D to -0.09 +/- 0.20D and mean sphere from -3.22 +/- 1.76D to -0.02 +/- 0.26D. Mean uncorrected visual acuity rose from 0.12 +/- 0.17 to 0.91 +/- 0.10. No eye lost lines of spectacle-corrected visual acuity. The safety index was 1.03 and the efficacy index 0.98. Six months from the treatment all eyes were within +/- 1D, 8.9% of eyes were within 0.50D and 44% were plano of target refraction. Refractive and topographical stability were achieved between one and three months after treatment. Transient haze was observed between one and three months after PRK. CONCLUSIONS: Photorefractive keratectomy with the MEL-70 excimer laser to correct myopic astigmatism was a safe and effective procedure with good stability at six months' follow-up. Refractive and visual outcome confirmed that excellent predictability can be expected.     

Effect of amniotic membrane after laser-assisted subepithelial keratectomy on epithelial healing: clinical and refractive outcomes

PURPOSE: To evaluate the effect of an amniotic membrane (AM) on reepithelialization time, corneal haze, and postoperative visual and refractive outcomes after laser-assisted subepithelial keratectomy (LASEK) for myopia and myopic astigmatism. SETTING: Department of Ophthalmology, Yonsei University College of Medicine, and Balgeunsesang Ophthalmology Clinic, Seoul, Korea. METHODS: One hundred fifty-two eyes of 84 patients with myopia or myopic astigmatism were prospectively evaluated for 6 months after LASEK. An AM was placed as a strip on the inferior limbus in 94 eyes of 54 patients after LASEK; 58 eyes of 30 patients served as the control group. Postoperative epithelial healing time, uncorrected visual acuity (UCVA), best corrected visual acuity, remaining refractive error, and corneal haze were examined. RESULTS: The reepithelialization time was shorter in the AM group (2.40 days +/- 0.94 [SD]) than in the control group (3.90 +/- 0.97 days) (P<.001). At 6 months, 86 eyes (91.5%) in the AM group had a UCVA of 20/25 or better and 90 eyes (95.7%) had a UCVA of 20/40 or better; 48 eyes (82.8%) and 53 eyes (91.4%) in the control group had a UCVA of 20/25 or better and 20/40 or better, respectively. The mean spherical equivalent in the AM group was -0.48 +/- 0.54 diopter (D) and in the control group, -0.94 +/- 0.60 D (P<.001). The corneal haze was significantly less in the AM group than in the control group (P<.001). CONCLUSION: Amniotic membrane use after LASEK induced rapid epithelial healing with more favorable visual and refractive outcomes and lower corneal haze scores than conventional LASEK.     

Topography-controlled excimer laser photorefractive keratectomy

PURPOSE: To assess whether photorefractive keratectomy (PRK) controlled by videokeratography can successfully treat refractive errors in eyes with corneal irregularities and improve spectacle-corrected visual acuity. METHODS: In a prospective clinical study, PRK was performed in 10 eyes of 10 patients. Reason for surgery was irregular astigmatism after penetrating keratoplasty, corneal irregularity after corneal scarring, corneal astigmatism in keratoconus, and decentration after myopic and hyperopic PRK. Excimer ablation was controlled by preoperative videokeratography (Orbscan II, Orbtek) using the MEL-70 system from Aesculap Meditec. Follow-up was 6 months. RESULTS: Concerning manifest refraction, the sphere was reduced on average from +1.92 to +0.57 D, 6 months postoperatively. Cylinder changed from -1.95 D on average to -0.30 D at 6 months postoperatively. There was improvement of uncorrected visual acuity of 2 or more lines in 5 eyes and no change in 5 eyes 6 months postoperatively. Spectacle-corrected visual acuity improved in 2 eyes by 2 to 3 lines, in 9 eyes by 1 to 3 lines, and showed no change in 1 eye. CONCLUSION: Videokeratography-controlled PRK improved refractive errors in irregular corneas with improvement of spectacle-corrected visual acuity.