准分子激光角膜切削术矫治白内障摘除术后屈光参差

目的　观察准分子激光屈光性角膜切削术 (PRK)矫治白内障摘除术后屈光参差的疗效。方法　对 2 4例 (31只眼 )白内障摘除术后屈光参差患者行PRK ,观察手术前、后患者的视力、屈光度数、屈光参差度数 ,以及手术并发症的情况。随访时间 12 2个月。结果　PRK术后术眼的视力明显提高 ,与术前比较差异有非常显著意义 (P <0 0 1) ;PRK术后术眼的球镜屈光度数为 (1 12± 0 5 5 )D ,散光度数为 (0 4 9± 0 38)D ,均较术前明显下降 ,差异均有非常显著意义 (P <0 0 1)。PRK术后患者双眼的屈光参差度数由术前的 (3 4 4± 1 0 7)D降至 (0 5 8± 0 31)D ,差异有非常显著意义(P <0 0 1)。术中和术后无严重并发症发生。结论　在临床尚无法进一步提高人工晶状体屈光度数计算结果准确性时 ,PRK可有效矫治白内障摘除术后的屈光参差 ,且具有安全、可靠等优点。     

Photorefractive keratectomy after cataract surgery in uncommon cases: long-term results

AIM: To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens (IOL) implantation in uncommon cases. METHODS: Totally 24 patients with high residual refractive error after cataract surgery with IOL implantation were examined. Twenty-two patients had a history of phacoemulsification and IOL implantation, and two had extra-capsular cataract extraction with IOL implantation. Detailed examination of preoperative medical records was done to explain the origin of the post-cataract refractive errors. All patients underwent photorefractire keratectomy (PRK) enhancement. The mean outcome measures were refraction, uncorretted visual acuity (UCVA), best corrected visual acuity (BCVA) and corneal transparency and follow up ranged from 1 to 8y. RESULTS: The principal causes of residual ametropia was inexact IOL calculation in abnormal eyes with high myopia and congenital lens abnormalities, followed by corneal astigmatism both suture induced and preexisting. After cataract surgery and before the laser enhancement the mean spherical equivalent (SE) was -0.56±3 D ranging from -4.62 to +2.25 D in high myopic patients, instead it was -1±1.73 D ranging from -3.25 to +3.75 D in the astigmatic eyes, with a mean cylinder of -3.75±0 ranging from -3 to +5.50 D. After laser refractive surgery the mean SE was 0.1±0.73, ranging from -0.50 to +1.50 in the myopic group, and it was -0.50±0.57 ranging from -1.25 to +0.50 in astigmatic patients, with a mean cylinder of -0.25±0.75. In myopic patients the mean UCVA and BCVA were 0.038±0.072 logMAR and 0.018±0.04 respectively, both ranging from 0.10 to 0.0. In astigmatic patients, the mean UCVA and BCVA were 0.213±0.132 and 0.00±0.0 respectively, UCVA ranging from 0.50 to 0.22 and BCVA was 0.00. All patients presented normal corneal transparency. No ocular hypertension was detected and no corneal haze was observed. All registered values remained stable also at the end line evaluation. CONCLUSION: The excimer laser treatment of residual refractive errors after cataract surgery with IOL implantation in abnormal eyes resulted in satisfactory and stable visual outcome with good safety and efficacy.     

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.     

Laser in situ keratomileusis for residual myopia after photorefractive keratectomy

PURPOSE: To evaluate the efficacy and safety of laser in situ keratomileusis (LASIK) for myopic regression and undercorrection after photorefractive keratectomy (PRK). SETTING: The Eye Institute, Sydney, Australia. METHODS: Fifty eyes of 32 patients were treated by LASIK for residual myopia following primary PRK. The mean spherical equivalent refraction (SEQ) was -2.92 diopters (D) +/- 1.57 (SD) (range -0.75 to -7.88 D). The mean refractive cylinder was 0.96 +/- 0.74 D (range 0 to 3.50 D). For analysis, the eyes were divided into 2 groups: those with 0 or low corneal haze (Group 1) and those with severe corneal haze (Group 2). In Group 1, the SEQ was -1.99 +/- 0.79 D (range -0.75 to -3.75 D) and in Group 2, -3.77 +/- 1.62 D (range -0.75 to -7.90 D). The procedure was performed using the Chiron Automated Corneal Shaper and the Summit Apex Plus laser. The mean interval between PRK and LASIK was 25 months (range 9 to 59 months). The following parameters were studied before and after LASIK retreatment: SEQ, mean refractive cylinder, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Complications after LASIK retreatment were evaluated. RESULTS: Six months after LASIK, the mean SEQ in all eyes was -0.65 +/- 0.86 D (range +1.50 to -3.35 D); 70.0% of eyes were within +/-1.00 D of emmetropia and the UCVA was 6/12 or better in 72.5%. The mean SEQ in Group 1 was -0.22 +/- 0.55 D (range -0.88 to -1.50 D) and in Group 2, -0.97+/- 0.92 D (range 0.12 to -3.25 D); the UCVA was 6/12 or better in 94.0% of eyes in Group 1 and in 56.0% in Group 2. No statistically significant between-group difference was found in lines of Snellen acuity lost or gained at 6 months. No eye lost more than 1 line of BCVA. CONCLUSIONS: Laser in situ keratomileusis appears to be a safe, effective, and predictable procedure for treating eyes with 0 or low haze with residual myopia after PRK. It is less predictable in eyes with severe haze.     

准分子激光角膜原位磨镶术矫治高度近视准分子激光屈光性角膜切削术后屈光回退的临床观察

目的评价准分子激光角膜原位磨镶术（LASIK）矫治高度近视准分子激光屈光性角膜切削术（PRK）后屈光回退的疗效。方法回顾性临床研究。对PRK术后2年以上、屈光回退且屈光度稳定的患者8例14眼行LASIK,对LASIK术后术眼进行评价。患眼PRK术前屈光度为-6.25～-12.50 D,PRK术后屈光度为-1.50～-6.25 D。随访观察LASIK矫正1年后术眼的裸眼视力、最佳矫正视力、屈光度、上皮下雾状混浊（haze）形成和角膜厚度的变化。结果所有患眼术后主观症状较轻。LASIK术后1年平均球镜度数为（-0.62±0.94）D。LASIK术后0.5≤裸眼视力〈0.8者4眼,≥0.8者9眼,1眼（7.1%）最佳矫正视力下降2行。4眼术后出现不同程度的haze,包括2级haze 3眼、3级haze 1眼。应用氟米龙滴眼液1个月后,haze及屈光回退减轻;术后1年,1级haze 2眼,2级haze 2眼,3级haze 1眼。LASIK术前角膜厚度为（467±38）μm,术后为（422±21）μm。结论高度近视PRK术后屈光回退行LASIK矫治是一种可行的方法,但少数患者术后可出现haze,仍需治疗。     

Laser in situ keratomileusis to correct residual myopia after cataract surgery

PURPOSE: To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) for correcting residual myopia after cataract surgery with intraocular lens implantation. METHODS: Twenty-two eyes of 22 patients underwent LASIK for the correction of residual myopia after cataract surgery. LASIK was carried out using the Chiron Automated Corneal Shaper and the NIDEK EC-5000 excimer laser. In all eyes, the follow-up was 12 months. RESULTS: Before LASIK, 1 eye (4.5%) had an uncorrected visual acuity of 0.5 or better; 12 months after LASIK, 10 eyes (45.4%) achieved this level of visual acuity and 0 eyes achieved 1.00 or better. Before LASIK, mean refraction was -2.90 +/- 1.80 D; 12 months after LASIK it decreased significantly to 0.40 +/- 0.60 D (P < .01). In 18 eyes (81.8%) at 12 months after LASIK, spherical equivalent refraction was within +/-1.00 D of emmetropia; 11 eyes (50%) were within 0.50 D. No vision-threatening complications occurred. CONCLUSION: LASIK with the Automated Corneal Shaper and Nidek EC-5000 excimer laser was an effective, predictable, stable, and safe procedure for correcting residual myopia after cataract surgery. No intraocular lens or cataract incision related complications occurred when LASIK was performed at least 3 months after phacoemulsification.     

Photorefractive keratectomy for myopia with a 15 Hz repetition rate

PURPOSE: To evaluate excimer laser photorefractive keratectomy (PRK) for myopia using a repetition rate of 15 Hz instead of 10 Hz. SETTING: The Cornea and Laser Eye Institute, Teaneck, and Department of Ophthalmology, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA. METHODS: Photorefractive keratectomy using a 15 Hz repetition rate was performed in 23 eyes of 14 patients by a single surgeon at 1 center. The attempted corrections ranged from -2.8 diopters (D) to -5.5 D. Preoperative and postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), predictability, corneal haze, and subjective glare/halo were evaluated over 6 months. RESULTS: At 6 months, UCVA was 20/32 or better in all eyes and at least 20/20 in 14 eyes (73.7%). Two eyes (10.5%) lost 2 or more Snellen lines of BSCVA; postoperative BSCVA was at least 20/25 in 100% of eyes and 20/20 or better in 95.0%. Fifteen eyes (78.9%) were within +/-0.5 D of attempted correction, and 19 (100%) were within +/-1.0 D. Mean spherical equivalent refraction was -4.62 D preoperatively, +0.15 D at 1 month, -0.09 D at 3 months, and -0.37 D at 6 months. At 6 months, 4 eyes (21.0%) had no corneal haze and 14 (73.7%) had trace subepithelial haze. Fifteen eyes (78.9%) had no glare/halo effect at 6 months, and 4 (21.0%) had minimal glare/halo effect. CONCLUSIONS: Clinical outcomes after excimer laser PRK for myopia using an increased repetition rate of 15 Hz were good and similar to those in studies conducted with a 10 Hz repetition rate.     

准分子激光再次角膜切削术治疗残余近视

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Laser in situ keratomileusis for treatment of residual myopia after photorefractive keratectomy

PURPOSE: To evaluate the results of laser in situ keratomileusis after photorefractive keratectomy. METHODS: Eighty eyes of 80 patients with residual myopia after photorefractive keratectomy were reoperated with laser in situ keratomileusis. The study was retrospective. Laser in situ keratomileusis was performed using the automated corneal shaper microkeratome and Chiron Technolas 217-C d1 excimer laser. Data measured after laser in situ keratomileusis included uncorrected visual acuity, best-corrected visual acuity, refraction, haze, pachymetry, and keratometry. The follow-up was at least 12 +/- 1.6 months (range, 12 to 15 months). RESULTS: After laser in situ keratomileusis the mean spherical equivalent was -0.24 diopters +/- 0.78. (range, -3 to +1.5) at 12 months, and the mean uncorrected visual acuity was 0.76 diopters +/- 0.24 (range, 0.1 to 1). Sixty-five eyes (81.3%) had various degrees of haze after laser in situ keratomileusis. One eye (1.2%) lost 2 lines of best-corrected visual acuity. CONCLUSIONS: Laser in situ keratomileusis enhancement may be a good alternative to correct residual myopia and astigmatism after primary photorefractive keratectomy. Corneal haze is a common problem in these eyes, and the treatment after laser in situ keratomileusis enhancement should be the same as the treatment after primary photorefractive keratectomy.     

Photorefractive keratectomy retreatment after LASIK

PURPOSE: To study the results of late photorefractive keratectomy (PRK) in corneas originally subjected to LASIK. METHODS: Seven eyes of seven patients who had LASIK for myopia were retreated with PRK at least 2 years after LASIK. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, and haze were evaluated before and after LASIK and after retreatment by PRK. RESULTS: Photorefractive keratectomy retreatment improved BSCVA in six (86%) of seven eyes, and one (14%) eye showed no changes. None of the eyes lost lines of BSCVA. Five of seven eyes developed mild haze, which disappeared before the last postoperative follow-up. CONCLUSIONS: Photorefractive keratectomy retreatment performed at least 2 years after LASIK can improve visual acuity. We hypothesize that LASIK-induced corneal nerve damage disturbs corneal wound healing by increasing the tendency for development of haze.     

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 0.02% mitomycin C for treatment of residual refractive errors after LASIK

PURPOSE: To evaluate the efficacy and safety of prophylactic mitomycin C (MMC) during photorefractive keratectomy (PRK) over LASIK flaps for the treatment of residual refractive errors following LASIK. METHODS: In this single center, retrospective clinical study, 30 eyes of 33 patients (mean age 37.2 years) who had MMC (0.02%, 30 to 120 seconds) during PRK for the treatment of residual refractive errors following myopic LASIK were evaluated. The retreatment procedures were performed with a VISX S4 laser with iris registration. All patients underwent slit-lamp microscopy, manifest and cycloplegic refraction, corneal topography, pachymetry, pupillometry, and wavefront analysis pre- and postoperatively. All patients underwent follow-up at 1 day, 1 week, and 1, 3, and 6 months and thereafter as required. RESULTS: Mean time between LASIK and PRK retreatment was 67.3 months (range: 7 to 113 months). No intra- or postoperative complications occurred during primary LASIK or PRK retreatment. Mean spherical equivalent refraction of attempted correction with PRK was -0.94 diopters (D) (range: -2.38 to +0.75 D). At mean 7.1-month follow-up, the average uncorrected visual acuity (UCVA) improved from 20/50 (range: 20/30 to 20/200) to 20/28 (range: 20/15 to 20/70). Twenty-seven of 30 eyes showed improvement in UCVA. Two eyes had subjective improvement of glare symptoms (and objective improvement in higher order aberrations), and one eye lost one line of best spectacle-corrected visual acuity due to unrelated corneal abrasion in the postoperative period. None of the eyes in the cohort developed postoperative haze. CONCLUSIONS: Photorefractive keratectomy with prophylactic MMC (0.02%) is a safe and effective option for treating myopic regression following LASIK. A single intraoperative application of 0.02% MMC for as few as 30 seconds was effective in preventing postoperative haze formation.     

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.     

Photorefractive keratectomy

Photorefractive keratectomy (PRK) is the alteration of corneal curvature by photoablation with an excimer laser to eliminate or significantly reduce refractive errors. In this paper, we present a comprehensive review of the literature on this procedure, from the principles and development of the laser system, to its clinical application, Melbourne particularly for the correction of myopia. Both animal and human studies have shown promising results and the procedure is fundamentally superior to radial keratotomy and other refractive surgical procedures; patient response is encouraging, refractive results are reasonably predictable and serious adverse effects on the cornea are infrequent. However, a number of concerns remain, including stromal haze and opacification, regression and instability of the refractive effect, decreased visual performance, due to light scattering and an imperfect refracting surface, and potential long-term side-effects. Optometrists should be well informed regarding PRK, so as to provide expert, independent advice for prospective patients, as well as pre- and post-operative follow- up care.     

Photorefractive keratectomy

In this chapter, we have reviewed important aspects of PRK. A thorough understanding of the preoperative assessments, techniques, and postoperative management is essential to achieve satisfactory visual outcomes. Laser safety checks are mandatory. A well-functioning excimer laser with good optics is required. The surgeon must avoid any decentration or global tilt. All aspects of the technique must be performed with attention to detail. The postoperative management requires frequent follow-up visits and psychological reinforcement of a healing process that is not instantaneous. PRK is a procedure in evolution. Although the results today are impressive, the complications in the future will continue to decrease with changes in lasers, techniques, and pharmacological management.