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.     

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.     

Photorefractive keratectomy for low-to-moderate myopia and astigmatism with a small-beam,tracker-directed excimer laser

ObjectiveTo assess the safety and effectiveness of the Autonomous Technologies Corporation LADARVision excimer laser system for photorefractive keratectomy correction of myopia and astigmatism.DesignA multicenter, prospective, noncomparative case series.ParticipantsThe cohort consisted of 467 eyes corrected for spherical myopia and 211 eyes corrected for myopia with astigmatism.InterventionTreatments were performed at six sites in the United States using a 6-mm ablation zone for spherical myopes and a 5.5-mm zone with a 1.0-mm blend for astigmats.Main outcome measuresVisual acuity, subjective refraction, corneal haze, intraocular pressure, complications, adverse reactions, patient satisfaction, and corneal endothelial changes.ResultsTwelve-month follow-up was available on 414 spherical eyes and 175 astigmatic eyes. The results for spherical eyes with correction between −1 and −5.99 diopters (D) were: uncorrected visual acuity (UCVA) of 20/40 or better achieved by 98.1%, 20/20 or better by 72%, 1.8% lost 2 lines and 0.3% lost greater than 2 lines of best spectacle-corrected visual acuity (BSCVA); 76.4% were within 0.50 D of the target correction and 94.4% were within 1.00 D. The results for myopia with astigmatism with spherical equivalent correction between −1 and −5.99 D were: UCVA of 20/40 or better in 97.4%, 20/20 or better in 61.7%, 2.5% lost 2 lines and no eyes lost greater than 2 lines BSCVA; 73.9% were within 0.50 D of the target correction and 95% were within 1.00 D. For spherical myopes combined with myopic astigmats corrected for 6 to 10 D, results were: UCVA of 20/40 or better in 93.4%, 20/20 or better in 61.2%, 2.3% lost 2 lines and no eyes lost greater than 2 lines of BSCVA; 67.2% were within 0.50 D of the desired correction and 87.8% were within 1.00 D. Refractive stability was achieved between 3 and 6 months for the spherical and astigmatic groups. No eyes had corneal haze graded as moderate or greater, and there was no significant decrease in endothelial cell density.ConclusionsPatients treated for 1 to 10 D of spherical equivalent myopia, with or without astigmatism, showed early refractive stability, excellent UCVA, no significant loss of BSCVA, no loss of endothelial cell density, and very low levels of corneal haze to 12 months after surgery.     

Photorefractive keratectomy for myopia with the Meditec MEL 70G-Scan flying spot laser

PURPOSE: To evaluate the efficacy, predictability, stability, and safety of the Meditec MEL 70G-Scan flying spot excimer laser. METHODS: One hundred thirty myopic eyes were treated with the Aesculap Meditec Mel 70G-Scan ArF flying spot excimer laser with photorefractive keratectomy (PRK). Patient groups: low myopia (Group 1) from -1.50 to -6.00 D (90 eyes), medium myopia (Group 2) from -6.10 to -9.00 D (31 eyes), high myopia (Group 3) from -9.10 to -14.00 D (9 eyes). RESULTS: At 12 months in the low myopia group, uncorrected visual acuity (UCVA) of 20/40 or better was achieved in 95.5% (86 eyes), 20/20 or better in 77.7% (70 eyes); 2.2% (two eyes) lost two or more lines of best spectacle-corrected visual acuity (BSCVA); 73.3% (66 eyes) were within +/-0.50 D of the target correction and 98.8% (89 eyes) were within +/-1.00 D. In the medium myopia group, UCVA of 20/40 or better was achieved in 74.2% (23 eyes), 20/20 or better in 25.8% (eight eyes); 3.2% (one eye) lost two lines, 61% (19 eyes) were within +/-0.50 D of desired correction and 83.8% (26 eyes) were within +/-1.00 D. In the high myopia group, UCVA of 20/40 or better was achieved in 22.2% (two eyes); 20/25 or better in 11.1% (one eye); none of the eyes achieved 20/20 UCVA; 22.2% (two eyes) lost two lines of BSCVA; 44.4% (four eyes) were within +/-0.50 D and 66.6% (six eyes) were within +/-1.00 D of the target correction. Refractive stability was achieved between 3 and 6 months. Increased intraocular pressure was detected overall in 7.69%. CONCLUSIONS: The results of predictability, safety, and efficacy in low and medium myopia with the Meditec MEL 70G-Scan flying spot excimer laser were good, but poorer predictability, regression, and a significant loss of BSCVA were observed in the high myopia group.     

Photorefractive keratectomy for myopia in the setting of adenoviral subepithelial infiltrates

PURPOSE: To report a patient with persistent subepithelial corneal opacities 18 months after adenoviral keratoconjunctivitis who underwent photorefractive keratectomy for the correction of myopia.METHODS: Case report, review of medical literature, and slit-lamp photography.RESULTS: The patient underwent photorefractive keratectomy in each eye, 1 week apart, with ablation of central corneal opacities and resultant best-corrected visual acuity of BE, 20/20. Symptomatic subepithelial stromal infiltrates recurred in the peripheral but not the central cornea of each eye 3 months after laser treatment.CONCLUSIONS: Photorefractive keratectomy was successful in the correction of myopia and prevented the recurrence of adenoviral subepithelial corneal infiltrates within the laser-treated central cornea.     

Photorefractive keratectomy for myopia in the setting of Thygeson's superficial punctate keratitis

PURPOSE: To describe a patient with Thygeson's superficial punctate keratitis who underwent photorefractive keratectomy for the correction of myopia. METHODS: A 49-year-old woman with unilateral Thygeson's keratitis was examined before and after photorefractive keratectomy. RESULTS: A myopic patient underwent photorefractive keratectomy in the left eye and gained 20/20 uncorrected visual acuity. Seventeen months after surgery, symptomatic Thygeson's keratitis lesions recurred in the peripheral but not the central cornea. CONCLUSION: Photorefractive keratectomy reliably corrected myopia in a patient with previous Thygeson's keratitis. The recurrence of lesions only in the peripheral untreated cornea suggests that the inflammatory signal in Thygeson's keratitis may reside in the superficial corneal stroma.     

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.     

Photorefractive keratectomy with mitomycin-C for the treatment of compound moderate myopia with astigmatism in buccal pemphigus vulgaris

We report a case of controlled buccal pemphigus vulgaris with compound moderate myopia with astigmatism that was treated with photorefractive keratectomy with mitomycin-C (PRK+MMC) in both eyes. The preoperative manifest refraction was -6.50 sphere and -5.5 -0.75 x 20 in the right eye and left eye, respectively, with a best corrected visual acuity of 10/10 in both eyes. Seven months after surgery, the uncorrected visual acuity was 10/10 in both eyes. The manifest refraction was 0.75 sphere and 0.50 -0.75 x 120 in the right eye and left eye, respectively. Haze was not detected in the follow-up examinations. Reepithelialization was complete 5 days after surgery in both eyes. The results show that PRK+MMC for compound moderate myopia with astigmatism in a patient with controlled pemphigus vulgaris may be an effective and safe treatment.     

Photorefractive keratectomy with mitomycin C versus LASIK in custom surgeries for myopia: a bilateral prospective randomized clinical trial

PURPOSE: To compare photorefractive keratectomy (PRK) with prophylactic use of mitomycin C (MMC) and LASIK in custom surgeries for myopic astigmatism. METHODS: Eighty-eight eyes of 44 patients with a minimum estimated ablation depth of 50 microm were randomized to receive PRK with MMC 0.002% for 1 minute in one eye and LASIK in the fellow eye. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cycloplegic refraction, slit-lamp microscopy, contrast sensitivity, specular microscopy, aberrometry, and a subjective questionnaire were evaluated. Forty-two patients completed 6-month follow-up. RESULTS: Mean spherical equivalent refraction error before surgery and mean ablation depth were -3.99+/-1.20 diopters (D) and 73.09+/-14.55 microm in LASIK eyes, and -3.85+/-1.12 D and 70.7+/-14.07 microm in PRK with MMC eyes, respectively. Uncorrected visual acuity was significantly better in PRK with MMC eyes 3 months (P=.04) and 6 months (P=.01) after surgery. Best spectacle-corrected visual acuity and spherical equivalent refraction did not differ significantly in the groups during follow-up (P>.05). Significant haze was not observed in any PRK with MMC eye. Mean higher order aberration was lower in PRK with MMC eyes postoperatively compared with LASIK eyes (P=.01). Better contrast sensitivity was observed in PRK with MMC eyes than LASIK eyes (P<.05). The endothelial cell count did not differ significantly between groups (P=.65). In terms of visual satisfaction, PRK with MMC eyes were better rated. CONCLUSIONS: Photorefractive keratectomy with MMC appears to be more effective than LASIK in custom surgery for moderate myopia. During 6-month follow-up, no toxic effects of MMC were evident. Long-term follow-up is necessary to attest its safety.     

Photorefractive keratectomy: a case report

A case of a 52-year-old male who underwent photorefractive keratectomy is reported. The major complications included variable refraction, deteriorating visual acuity, corneal scarring and haze, monocular polyopia and dry eye. (CM Exp Optom 1995: 78: 4:130–134)     

Photorefractive keratectomy with intraoperative mitomycin-C application

PURPOSE: To evaluate the efficacy and safety of photorefractive keratectomy (PRK) with intraoperative application of mitomycin-C (MMC). SETTING: Yonsei Eye Center, Seoul, South Korea. METHODS: This retrospective noncomparative case series included 536 patients (1011 eyes) who had had PRK with intraoperative application of MMC using the Nidek EC-5000 excimer laser. Preoperative and postoperative best spectacle-corrected and uncorrected visual acuities, spherical equivalent (SE) refraction, corneal haze graded by slitlamp biomicroscopy, and endothelial cell density measured by specular microscopy were evaluated. RESULTS: The mean preoperative SE was -7.82 diopters (D) +/- 2.64 (SD); 72% of eyes (732) were more than -6.00 D, and 28% (287) were more than -9.00 D. The mean follow-up was 13 months (range 6 to 27 months). Six months postoperatively, the mean postoperative SE was -0.14 +/- 0.62 D; 86% were within +/-0.50 D and 93% were within +/-1.00 D of desired refraction. Eighty-six percent had 20/20 or better visual acuity, and 98% were 20/40 or better. Regression of more than 1.00 D occurred in 78 eyes (7.6%), and it was more common in eyes with a preoperative SE of -9.00 D or worse (18%). Haze occurred in 32 eyes (3.17%), but in most cases it was limited to grade 1. Grades 2 and 3 haze occurred in 3 eyes and 2 eyes, respectively. The postoperative endothelial cell density measured by specular microscopy did not show a significant difference from preoperative measurements. Delayed epithelial healing was observed in 2 eyes. CONCLUSION: Photorefractive keratectomy with intraoperative application of MMC was a safe procedure that produced excellent visual outcomes with few complications.     

Photorefractive keratectomy for compound myopic astigmatism

PURPOSE: To evaluate the safety and efficacy of photorefractive keratectomy for the treatment of primary compound myopic astigmatism. METHODS: In a prospective study, 93 eyes from 56 patients with a mean spherical equivalent of -4.98 +/- 1.80 diopters (range, -1.75 to -8.5) underwent photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser using erodible mask technology and were followed for 2 years. Primary outcome measures included an assessment of astigmatic correction through vector analysis, manifest refraction, uncorrected visual acuity, corneal clarity, and the presence of adverse symptoms.RESULTS: Eighty-five eyes (91.4%) were available for analysis at 6 months. Mean spherical equivalent refraction was reduced 85% (mean, -0.75 +/- 0.85 diopter) and the target-induced astigmatism was reduced 70% (mean, 0.98 +/- 1.88 diopters). Forty-eight eyes (56%) had an uncorrected visual acuity of 20/20 or greater, whereas 70 eyes (82%) had an uncorrected visual acuity of 20/40 or greater. Twenty-four eyes (26% ) required re-treatment because of undercorrection of the spherical equivalent and astigmatic components after the 6-month follow-up. Fifty-nine of the remaining eyes were available at the 24-month visit. Mean spherical equivalent refraction was reduced to -0.39 +/- 0.72 diopter (91.8%). The target-induced astigmatism was reduced 64% from 1.74 diopters. Forty-one eyes (81.3%) were within +/-1.0 diopter of attempted spherical equivalent correction. Stability within a spherical equivalent of +/-0.5 diopter occurred after the first postoperative month. Fifty-six eyes (94.9%) had an uncorrected visual acuity of 20/40 or greater, whereas 34 eyes (57.6 %) demonstrated an uncorrected visual acuity of 20/20 or greater. One eye (1.7%) lost 2 or more lines of best spectacle-corrected visual acuity.CONCLUSION: Photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser is a safe and effective method of reducing compound myopic astigmatism. However, higher re-treatment rates may result from significant undercorrections because of current laser algorithms and variability in the mean angle of error.     

Photorefractive keratectomy with a small spot laser and tracker

BACKGROUND: The Autonomous Technologies LADARVision excimer laser system utilizes an eye tracking mechanism and a small spot for photorefractive keratectomy. METHODS: One hundred and two eyes of 102 patients were treated for -1.50 to -6.25 D of spherical myopia at the spectacle plane using a 6-mm diameter ablation zone. One year follow-up was available for 93 eyes (91%). RESULTS: Uncorrected visual acuity for eyes treated for distance vision was 20/40 or better in 99% (n = 90), and 20/20 or better in 70% (n = 64) of eyes at 12 months. Spectacle-corrected visual acuity was 20/25 or better in all 92 eyes reported; no eye lost more than 2 lines of spectacle-corrected visual acuity, and only 1 eye (1.0%) experienced a loss of 2 lines (20/12.5 to 20/20) at 1 year. The refractive result was within +/- 0.50 D of the desired correction in 75% (n = 70), and within +/- 1.00 D in 93% (n = 86) of eyes at 12 months. Refractive stability was achieved between 3 and 6 months. Corneal haze was graded as trace or less in 100% of the 93 eyes. No significant reductions were noted in contrast sensitivity or endothelial cell density. CONCLUSIONS: Patients treated with the Autonomous Technologies LADARVision excimer laser system for -1.50 to -6.25 D of spherical myopia with 1 year follow-up had uncorrected visual acuity of 20/20 or better in 70%, no significant loss of spectacle-corrected visual acuity, no reduction of endothelial cell density or contrast sensitivity, and low levels of corneal haze.     

Photorefractive keratectomy: a technique for laser refractive surgery

The excimer laser offers entirely new corneal surgery procedures. In this paper, we describe conditions for one such procedure, photorefractive keratectomy, the direct reshaping of the cornea's central optical zone using tissue ablation with far ultraviolet radiation. We present equations for the required tissue ablation to achieve required refractive corrections. Conditions for beam uniformity are presented and a method of achieving better beam uniformity using beam integration by rotation is demonstrated. The healing of rabbit corneas after area ablation was observed. Five days after treatment, the surface quality of deep cuts was very irregular; the shallow cuts produced more regular results, as predicted by our calculations of beam characteristics.