Phototherapeutic keratectomy for decentration and central islands after photorefractive keratectomy

PURPOSE: To determine visual outcomes after treatment of decentration and central islands occurring after photorefractive keratectomy (PRK). DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Patients (n = 14) who exhibited decentration or central islands after PRK and photoastigmatic keratectomy (PARK). METHODS: Fourteen eyes with post-PRK decentration (group I) or central islands (group II) were treated by transepithelial phototherapeutic keratectomy guided by epithelial fluorescence without modulating agents, and subsequently were treated with PRK or PARK. Mean follow-up time was 9 months (range, 45 days-21 months). MAIN OUTCOME MEASURES: We analyzed pre- and postoperative keratometry, refractive errors, uncorrected visual acuity (UCVA), best-corrected visual acuity, and haze. In group I, we also measured pre- and postoperative decentration; in group II, we compared pre- and postoperative central island power. RESULTS: Group I showed improvement in centration (P = 0.003). Group II showed decreased central island power (P = 0.18). -LogMAR UCVA improved from 0.59 (20/80(+1)) to 0.17 (20/30) (P = 0.03) and from 0.74 (20/100(-1)) to 0.21 (20/30(-1)) (P = 0.01) after retreatment of groups I and II, respectively. CONCLUSIONS: Retreatment of patients having decentration and central islands after PRK results in improved visual outcomes.     

Phototherapeutic keratectomy of a corneal scar due to presumed infection after photorefractive keratectomy

This case involves a 25-year-old patient who suffered from corneal ulceration several days after photorefractive keratectomy (PRK). A central scar developed, resulting in discomfort and reduction in visual acuity. Four months later, the scar was treated by phototherapeutic keratectomy (PTK) (25 microns depth, 5 mm ablation zone). Some scar tissue was left, but it cleared slowly and steadily over the next few years. The induced hyperopia decreased from 5.00 to 1.37 diopters spherical equivalent within 28 months postoperatively. Best corrected visual acuity increased from 20/60 preoperatively to 20/20 at 28 months postoperatively. Surgeons can encourage patients with postinfectious scars after PRK to try at least 1 PTK treatment.     

Phototherapeutic keratectomy with mitomycin C for corneal haze following photorefractive keratectomy for myopia

PURPOSE: To evaluate the safety and efficacy of phototherapeutic keratectomy (PTK) with single application of mitomycin C for patients with severe corneal haze following photorefractive keratectomy (PRK) for high myopia. METHODS: Eight eyes of seven patients were treated with PTK and intraoperative topical application of mitomycin C (0.02%) for severe corneal haze (grade 3) following PRK for myopia. RESULTS: All patients' visual performance improved significantly. Mean preoperative visual acuity (20/200 for both UCVA and BSCVA) improved significantly to 20/33 (0.6) and 20/30 (0.7) for UCVA and BSCVA, respectively. Six eyes (85.7%) had improved UCVA to 20/40 or better and gained five or more lines of UCVA. The corneal haze score decreased from grade 3 initially (for all eyes prior to PTK and mitomycin C) to a final mean haze score of 0.3 (range 0 to 0.5). Mean final spherical equivalent refraction achieved was -1.30 +/- 1.60 D (range -3.75 to +1.25 D). One eye gained only three lines of visual acuity due to regression and residual haze. No adverse effects related to the use of mitomycin C were recorded. CONCLUSION: PTK with a single intraoperative application of mitomycin C was safe and effective in reducing corneal haze and improving visual acuity in patients with severe corneal haze following PRK.     

准分子激光治疗性切削联合屈光性切削治疗伴有角膜混浊的近视眼

目的　了解准分子激光治疗性切削 (PTK)联合屈光性切削 (PRK)治疗伴有角膜混浊近视眼的方法及疗效。方法　激光加刮除去除角膜上皮 ,PTK切削混浊角膜 ,直径为 7 0mm。PRK作近视切削 ,直径为 6 0mm。对于角膜不平者术中用黏弹剂填平后再行上皮去除及PTK。PTK切削深度为影响视力的角膜混浊深度减去PRK及上皮切削厚度。结果　 5 4例 (79只眼 )伴有角膜混浊的近视眼治疗后随访 1年以上 ,术前平均屈光度数为 (- 6 73± 4 17)D ,平均最佳矫正视力为 0 6 3,角膜混浊原因包括感染、机械外伤、化学烧伤、热烧伤、手术后瘢痕及其他原因。术中PTK联合PRK平均切削深度为 (12 4 6 3± 5 3 31) μm。术后 5 0只眼 (6 3 3% )切削区角膜上皮下雾状混浊 (Haze)≤Ⅰ级 ,6 9只眼(89 9% )裸眼视力等于或超过术前最佳矫正视力 ,平均为 0 74。角膜表面较术前光滑 ,散光减轻。结论　PTK联合PRK是治疗伴有角膜混浊近视眼的一种安全有效的方法。     

Histology of rabbit corneas after 10-diopter photorefractive keratectomy for hyperopia.

PURPOSE: To measure histological changes in the optical and transition zones of rabbit corneas treated with excimer laser photorefractive keratectomy (PRK) to correct hyperopia and to estimate the optical effect of these changes on the induced power profile. METHODS: Corrections of +10.00 D were ablated by means of a Questek 2620 excimer laser and rotational masks on 8 rabbit eyes. On frozen sections of 4 stained corneas and historesine sections of 4 other corneas, stromal, new stromal, epithelial, and total corneal thickness were measured on four significant locations. The optical effect of each parameter on the axial power profile was estimated in a computer simulation. RESULTS: Mean stromal regrowth was 50% of the ablated tissue. Deposition was lenticular and could account for -5.00 D of regression. Stromal thickening without regrowth occurred in the optical zone and over the shoulder, causing augmentation instead of regression. The epithelium thickened 20% in the mid-transition zone and was thinner over the shoulder, accounting for 1.00 D of regression and an increase in asphericity in the optical zone. CONCLUSION: In these hyperopic rabbit PRK corneas, stromal regrowth and epithelial hyperplasia were lenticular and contributed to regression of the optical effect. Stromal swelling around interrupted collagen lamellae seemed to occur, augmenting the optical effect. The epithelium filters high spatial frequency stromal irregularities.     

Cellular effects of mitomycin-C on human corneas after photorefractive keratectomy

PURPOSE: To investigate the effects of mitomycin-C (MMC) on epithelial and keratocyte cell kinetics after photorefractive keratectomy (PRK) using an in vitro human cornea model. SETTING: Department of Academic Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom. METHODS: Twenty-four human eye-bank corneas were placed in a specially designed acrylic corneal holder and cultured using the air-interface organ culture technique for up to 4 weeks. The corneas were divided into 3 groups. Group 1 consisted of 8 human corneas that had -9.00 diopter (D) myopic PRK without MMC application. Group 2 consisted of 8 corneas that had -9.00 D PRK with MMC (0.2 microg/mL) application for 1 minute on the stromal surface after ablation. Group 3 consisted of 8 corneas that had -9.00 D PRK with 2-minute exposure to MMC (0.2 microg/mL). Temporal events in epithelial and keratocyte cell kinetics were evaluated using digital imaging, confocal microscopy, and light microscopy. RESULTS: Epithelial latency was significantly delayed with MMC application in Groups 2 and 3 (P<.001). Epithelial migration was delayed in Group 3 (2-minute exposure) compared to migration in Group 2 (P<.04), with a consequent delay in epithelial closure (P<.001). Group 3 corneas had poorly differentiated epithelium that was significantly thinner than in Groups 1 and 2 (P<.0001). A significant delay in keratocyte regeneration occurred after MMC application (P<.0005). At 4 weeks, the anterior stromal cell density was significantly lower in Group 3 than Group 2 (P<.001). There were no significant differences in the mid- and posterior stromal keratocyte density between the groups. CONCLUSIONS: Results suggest that epithelial healing after MMC is characterized by prolonged latency and decreased migration rate dependent on exposure time. Mitomycin C application did not result in increased loss of keratocytes, but it significantly delayed keratocyte repopulation in the anterior stroma. The use of MMC 0.2 microg/mL for 1 minute resulted in optimum modulation of healing characterized by reduced keratocyte activation with normal epithelial differentiation.     

Phototherapeutic keratectomy in children

PURPOSE: Children with dense superficial opacities of the cornea are at risk for developing amblyopia. This study evaluated the efficacy of phototherapeutic keratectomy (PTK) in severe cases of anterior stromal scarring. METHODS: Five eyes of five patients, aged 6 to 8 years, were included. Three children suffered from uveitis-associated band keratopathy, one child had anterior corneal stromal scarring due to viral infection, and one child had anterior basement membrane dystrophy. Phototherapeutic keratectomy was performed under general anesthesia using the 200 Hz ALLEGRETTO excimer laser. Optical treatment zone was 7.0 mm (one eye) and 8.0 mm (four eyes), and ablation depths were between 20 and 100 microm. Postoperative treatment consisted of bandage soft contact lens, topical preservative-free antibiotics, steroids, and artificial tears. Part-time occlusion therapy was continued, as prior to PTK. Because of the small cohort, statistical evaluation was not performed. RESULTS: Mean follow-up was 23.4 +/- 13.7 months (range: 10 to 41 months). Surgery and postoperative follow-up were uneventful, and no signs of infection or haze were noted. Preoperative best spectacle-corrected visual acuity was 0.4 to 3.0 logMAR (mean: 1.22 +/- 1.07 logMAR). Best spectacle-corrected visual acuity improved in four eyes and stabilized in one eye due to uveitis recurrence (mean 0.64 +/- 0.65 logMAR). Mean preoperative keratometric values changed from 45.60 +/- 0.90 to 44.90 +/- 3.00 diopters postoperatively. CONCLUSIONS: Dense superficial corneal opacity in children may be successfully treated with PTK. Phototherapeutic keratectomy was performed to increase corneal transparency and corneal surface smoothing thereby avoiding amblyopia.     

准分子激光屈光性角膜切削术术后角膜愈合的组织学定量研究

目的：定量描述准分子浙江屈光性角膜切削术（ＰＲＫ）术后早期角膜愈合的组织学变化规律。方法：２０只（４０只眼）新西兰白兔,行－５．０Ｄ ＰＲＫ手术。于术后３天、１周、２周、３周和４周观察角膜的组织学改变,并通过计算机图像处理系统,对其定量化。同时用苦味酸天狼星红偏振光法观察角膜胶原变化。结果：ＰＲＫ术后２周内上皮增生速度较快,２￣４周时,速度缓慢。基质内成纤维细胞密度于术后１周呈持续性增长。ＰＲＫ术     

Phototherapeutic keratectomy for anterior scarring in an epikeratophakia lenticule.

PURPOSE: To present a case of anterior scarring in an epikeratophakia lenticule and its partially successful treatment with the excimer laser. METHODS: Excimer laser phototherapeutic keratectomy (PTK) was used to reduce corneal scarring in an epikeratophakia lenticule. RESULTS: Visual acuity improved after two sessions of PTK. CONCLUSIONS: PTK is an alternative to epikeratophakia lenticule removal.     

Phototherapeutic keratectomy for bullous keratopathy.

AIMS--This study was designed to investigate the therapeutic potential of excimer laser for recurrent painful erosions in patients not suited to treatment with penetrating keratoplasty. METHODS--Phototherapeutic keratectomy (PTK) with the excimer laser was performed prospectively on a series of 13 eyes of 12 patients with recurrent corneal erosions in connection with bullous keratopathy of varied aetiology. The main complaint of the patients before the treatment was frequent attacks of pain. The patients selected either refused corneal grafting or could not for a variety of reasons expect to profit visually from an operation. The treatment was performed with the MEL 60 Aesculap Meditec excimer laser using either a spot mode (five cases), a scanning mode (three cases), or a combination of both (five cases). RESULTS--All patients responded well to the treatment, and the pain subsided after a couple of weeks. In five cases (38.5%) a second treatment was necessary because of persistent pain, which was, however, much less than before the initial treatment. In four of these five patients small corneal bullae persisted. The visual performance of the seven patients with visual acuity better than 20/200 ameliorated in two cases and remained unchanged in four cases. One patient lost two Snellen lines after the laser treatment for terminal glaucoma. The mean follow up was 14.1 months (range 1-28 months). No complications were seen so far. CONCLUSION--It was concluded that PTK is a very promising and effective outpatient treatment for patients with bullous keratopathy. This therapeutic approach is not thought to have been described before.     

Phototherapeutic keratectomy in treating keratomycosis

PURPOSE: To evaluate the efficacy of using phototherapeutic keratectomy (PTK) in the treatment of superficial keratomycosis. METHODS: We studied 9 patients with superficial keratomycosis that had infiltrated less than half of the corneal thickness and responded poorly to topical antifungal therapy. Using a 193-nm excimer laser, we performed PTK to try to eradicate the infiltrates and facilitate antifungal therapy. We compared our study group findings with those of a control group made up of 31 cases of keratomycosis, also involving infiltration of less than half of the corneal thickness that had been treated with traditional surgical procedures and topical antifungal agents. RESULTS: Using PTK and short-term antifungal eyedrops, we were able to eradicate keratomycosis without recurrence in all 9 study patients. Much less time was needed to treat the PTK group (12.9 +/- 3.6 days) than the control group (40.8 +/- 26.4 days) (P <0.05). After PTK, the ablated area underwent rapid reepithelialization (average, 3.6 +/- 1.8 days). Final vision ranged from 20/200 to 20/20. The PTK group had an average visual improvement of 2.9 +/- 2.1 lines, which was significantly better than final improvement found in the control group (average, 0.6 +/- 1.7 lines) (P < 0.05). PTK complications included mild corneal haze, astigmatism, and thinning cornea. CONCLUSIONS: Because PTK can shorten treatment time, hasten reepithelialization, and restore reasonably good vision, it can be a valuable therapeutic alternative for superficial keratomycosis, especially in instances in which there is poor response to treatment by topical antifungal agents alone.     

Wound healing in rabbit corneas after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE: To compare the wound-healing process in the rabbit cornea after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the same refractive correction. SETTING: Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. METHODS: Adult albino rabbits (N = 24) were used. One eye of each animal had PRK or LASIK with the same refractive correction. Each animal was killed after an interval of up to 6 months. The expression pattern of corneal stromal injury-related molecules with the 2 treatments were compared. Paraffin sections of the cornea were processed immunohistochemically for alpha-smooth muscle actin (alpha-SMA), collagen type IV [alpha1(IV)](2),alpha2(IV), and heat shock protein (HSP) 47 as well as other HSPs. Sections were also examined after hematoxylin and eosin or periodic acid-Schiff staining. RESULTS: Hematoxylin and eosin staining showed the central epithelium to be thick in PRK-treated corneas. The thick epithelium was restricted to the area around the corneal flap edge adhesion in LASIK-treated corneas at 3 months. Periodic acid-Schiff staining showed an absence of or interruption in the epithelial basement membrane in PRK-treated corneas for up to 6 months. Heat shock protein 47 was detected in keratocytes on day 3 but not after that in PRK-treated corneas. There was no difference in the expression of other HSPs. Alpha-smooth muscle actin was expressed in keratocytes repopulated in the central anterior cornea of PRK-treated corneas at 28 days. Keratocytes with immunoreactivity for these 2 proteins were not seen in LASIK-treated corneas. Collagen IV [alpha1(IV)](2),alpha2(IV) was not detected in either group of corneas. The central epithelium became transiently thicker in PRK-treated corneas. CONCLUSION: Keratocyte responses to laser stromal ablation were more marked in corneas treated with PRK than in those treated with LASIK.     

Phototherapeutic keratectomy for macular corneal dystrophy.

PURPOSE: To report a case of early intervention with phototherapeutic keratectomy for treatment of macular corneal dystrophy. METHODS: We report a 21-year-old Saudi male with early macular corneal dystrophy, recurrent erosions, and decreased visual acuity, who underwent phototherapeutic keratectomy in the right eye and penetrating keratoplasty in the left eye with more than 2 years of follow-up. RESULTS: Following phototherapeutic keratectomy, uncorrected visual acuity in the right eye improved from 20/80 to 20/30. Following penetrating keratoplasty in the left eye, uncorrected visual acuity deteriorated from 20/80 to 20/120 due to irregular astigmatism; the eye was not amenable to improvement with spectacle correction, and the patient declined contact lens therapy. In the right eye, there has been no anterior recurrence, although some mid- to deep stromal haze, which is not visually significant, has developed. CONCLUSIONS: Early intervention for symptomatic, anterior macular corneal dystrophy with phototherapeutic keratectomy is relatively safe and preferable to observation or penetrating keratoplasty.     

Corneal wavefront-guided photorefractive keratectomy in patients with irregular corneas after corneal refractive surgery

PURPOSE: To evaluate the corrective potential of corneal wavefront-guided photorefractive keratectomy (PRK) in patients with high levels of corneal aberrations and symptoms after previous corneal refractive surgery. SETTING: Vissum-Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: This study comprised 25 eyes (20 patients) that had 1 or more previous unsuccessful keratorefractive procedure. All eyes had PRK retreatment using the Esiris excimer laser and ORK-CAM software for customized ablation design. All eyes had a high preoperative level of corneal higher-order aberrations (HOAs) (coma-like or spherical-like root mean square [RMS] >0.5 microm). Changes in refractive outcomes, subjective symptoms, and corneal aberrometry were evaluated during a 6-month follow-up. RESULTS: Uncorrected visual acuity improved significantly from preoperatively (mean 0.48) to 6 months after retreatment (mean 0.75) (P<.01). The mean best spectacle-corrected visual acuity (BSCVA) also improved significantly, from 0.78 to 0.90, respectively (P<.01). Forty-four percent of patients gained 1 or more lines of BSCVA. The reduction in cylinder at 6 months was statistically significant (P= .01). Corneal aberrometry at 6 months showed a statistically significant reduction in total (P= .01), spherical-like (P<.01), coma-like (P= .02), and primary coma (P<.01) RMS. At 6 months, 72% of patients had low or no perception of halos and all reported no glare. CONCLUSION: Corneal wavefront-guided PRK enhancement with the ORK-CAM system minimized corneal HOAs in eyes with previous unsuccessful keratorefractive surgery.     

Epithelial photorefractive keratectomy as an enhancement procedure after laser in situ keratomileusis.

The authors describe the refractive effect of epithelial photorefractive keratectomy (E-PRK) on 10 eyes that had undergone LASIK (group 1) and 13 eyes that had not been operated on (group 2). The central 6 mm was ablated. The mean corneal epithelium removed was 15.64 +/- 8.703 microm in group 1 and 25.23 +/- 7.069 microm in group 2. In group 1, the mean postoperative best uncorrected visual acuity (BUCVA) was 1.24 +/- 0.344, which was sustained for a mean of 2.75 +/- 3.456 months and returned to the preoperative value in 6.1 +/- 4.61 months. In group 2, all patients reported severe ocular pain and the BUCVA decreased except for 2 patients whose eyes reached 1.0 at 1 week postoperatively. All eyes reached the preoperative BUCVA by 1 month. This method is contraindicated for previously unoperated corneas but may be useful to enhance post-LASIK eyes when standard enhancement surgery is problematic.     

Arcuate transverse keratotomy remains a useful adjunct to correct astigmatism in conjunction with photorefractive keratectomy

PURPOSE: To retrospectively evaluate the effectiveness of paired, arcuate transverse keratotomy (Arc-T) performed prior to or after photorefractive keratectomy (PRK) to correct low to moderate amounts of natural or laser-induced astigmatism. METHODS: Spherical PRK was performed in 730 eyes for myopia of -1.00 to -7.00 D. PRK with arcuate transverse keratotomy was performed in 150 of these eyes; we studied 123 eyes that did not have PRK enhancement. Arc-T was performed prior to PRK in all 37 study eyes with astigmatism of 1.50 D or more at the preoperative examination. Arc-T keratotomy was performed after PRK in 86 study eyes for residual astigmatism of +0.75 D or more and uncorrected visual acuity of 20/30 or worse. RESULTS: Arc-T before PRK group: PRK was performed at a mean 1.0 +/- 1.5 months after Arc-T. Mean astigmatism decreased from +2.40 +/- 0.6 D (range, 1.00 to 4.00 D) before Arc-T to 0.60 +/- 0.60 D (range, 0 to 2.25 D) after Arc-T (P < .0001). Net change in astigmatism was 1.80 +/- 0.60 D (range, 0.80 to 2.80 D) and mean reduction was 75%. Spherical equivalent refraction changed from -4.10 +/- 1.90 D (range, -0.25 to -8.10 D) to -4.40 +/- 1.80 D after Arc-T (P = .002). Mean change in spherical equivalent refraction after Arc-T was -0.30 +/- 0.50 D (range, -1.10 to +0.40 D). Arc-T after PRK group: Arc-T was performed at a mean 3.5 +/- 1.9 months after PRK. Six months after Arc-T, astigmatism was decreased from +1.50 +/- 0.60 D to 0.40 +/- 0.40 D (P = .04). Net change in astigmatism at 6 months was 1.10 +/- 0.60 D and mean reduction was 74%. Vector change in astigmatism magnitude was 1.30 +/- 0.60 D (range, 0 to 4.00 D) at 6 months and vector change in astigmatism axis was 65 degrees +/- 68 degrees. Spherical equivalent refraction did not change when Arc-T was performed after PRK for eyes with low astigmatism (P = .4). Arc-T retreatment was performed in 6 of 37 (16%) eyes that had Arc-T before PRK and 18 of 86 (21%) eyes that had Arc-T after PRK (P = .12). CONCLUSION: Arcuate transverse keratotomy performed prior to PRK for high astigmatism or after PRK for lower levels of residual astigmatism effectively improved visual outcome. Coupling was less predictable for high levels of astigmatism correction with Arc-T.     

Phototherapeutic keratectomy in Salzmann's nodular degeneration

PURPOSE: To describe the outcome in vision and refraction of phototherapeutic keratectomy (PTK) in Salzmann's nodular degeneration (SND). METHODS: Five eyes of four patients underwent PTK with the objective of restoring an acceptable refractive status and improving visual acuity. This surgical technique aims to make the nodules level with the corneal surface using an excimer laser. RESULTS: Best corrected visual acuity (BCVA) improved in all five eyes. Astigmatism was reduced in four eyes and increased somewhat in one. During the observation period one eye suffered a late recurrence that required a penetrating graft. CONCLUSION: Salzmann's nodular degeneration is a rare disease that is sometimes difficult to diagnose as it has some resemblance to other diseases. The aetiology of the disease is unknown. Phototherapeutic keratectomy is a safe and effective mode of treatment. Recurrences occur with time.     

Confocal microscopy reveals persisting stromal changes after myopic photorefractive keratectomy in zero haze corneas

AIMS—Micromorphological examination of the central cornea in myopic patients 8-43 months after excimer laser photorefractive keratectomy (PRK), using the slit scanning confocal microscope.
METHODS—Patients were selected from a larger cohort of individuals on the basis of full corneal clarity (haze grading 0 to +1; mean 0.3) and their willingness to participate in the study. 15 eyes of 10 patients with myopic PRK (−4 to −11 D; mean 6.7) and an uneventful postoperative interval of 8-43 months (mean 26) were examined. Contact lenses had been worn by eight of the 10 patients for 4-11 years (mean 6.7) before surgery. Controls included the five untreated fellow eyes of PRK patients, 10 healthy, age matched volunteers without a history of ocular inflammation or contact lens wear, and 20 patients who had worn rigid gas permeable (n=10) or soft contact lenses (n=10) for 2-11 years. Subjects were examined with a real time flying slit, scanning confocal microscope using ×25 and ×50 objectives.
RESULTS—In PRK treated patients and contact lens wearers, basal layer epithelial cells sporadically displayed enhanced reflectivity. The subepithelial nerve plexus was observed in all individuals, but was usually less well contrasted in the PRK group, owing to the presence of a very discrete layer of subepithelial scar tissue, which patchily enhanced background reflectivity. Within all layers of the stroma, two distinct types of abnormal reflective bodies were observed in all PRK treated eyes, but in none of the controls. One had the appearance of long (>= 50 µm), slender (2-8 µm in diameter) dimly reflective rods, which sometimes contained bright, punctate, crystal-like inclusions, arranged linearly and at irregular intervals. The other was shorter (<25 µm), more slender in form (<1 µm in diameter), and highly reflective; these so called needles were composed of crystal-like granules in linear array, with an individual appearance similar to the bright punctate inclusions seen in rods, but densely packed. Both of these unusual structures were confined, laterally, to the ablated area, but were otherwise distributed throughout all stromal layers, with a clear predominance in the anterior ones. These rods and needles were observed in all PRK treated corneas, irrespective of previous contact lens wear. On the basis of qualitative inspection, the incidence of rods and needles did not appear to correlate with either the volume of tissue ablated or the length of the postoperative interval. In contact lens wearing controls, highly reflective granules, reminiscent of those from which the needles were composed, were found scattered as isolated entities throughout the entire depth and lateral extent of the corneal stroma, but rods and needles were never encountered. The corneal endothelium exhibited no obvious abnormalities.
CONCLUSION—Confocal microscopy 8-43 months after PRK revealed belated changes in the corneal stroma. These were manifested as two distinct types of abnormal reflective bodies, which had persisted beyond the stage when acute wound healing would have been expected to be complete. The clinical significance of these findings in the context of contrast visual acuity and long term status of the cornea is, as yet, unknown.

Keywords: photorefractive keratectomy; excimer laser; confocal microscopy; stromal pathology