Comparison of corneal wound-healing response in photorefractive keratectomy and laser-assisted subepithelial keratectomy

The use of topical nalbuphine in different concentrations to control pain after photorefractive keratectomy

PURPOSE

This is a randomized controlled study aiming to evaluate the safety and efficacy of two different concentrations of topical nalbuphine hydrochloride, when used to relieve pain in the first days following photorefractive keratectomy (PRK).

METHODS

This is a prospective double blinded randomized clinical trial that included 189 patients who had PRK for correction of low and moderate refractive errors. Patients were randomly assigned to three groups according to the eye drops given to relieve pain in the first three postoperative days; the first group received topical nalbuphine with a concentration of 2 mg/ml (Group A = 64 patients), the second group received topical nalbuphine in a concentration of 1 mg/ml (Group B = 69 patients) and the third group received topical artificial tears only (Group C = 56 patients).The patients were asked to rate their pain daily using a numeric rating scale and to record the number of drops instillation times/day. The time needed for complete epithelial healing, best-corrected visual acuity (BCVA) and spherical equivalent after three months were recorded in each group.

RESULTS

In the first three days, there was a statistically significant difference in pain score among the three groups with lower values in the two topical nalbuphine groups when compared with the control group receiving artificial tears. Moreover, the higher concentration group showed significantly lower pain score and less number of drops used /day in comparison with the lower concentration group.There were no statistically significant differences in epithelial healing time, BCVA and spherical equivalent after three months among the three groups.

CONCLUSION

The use of topical nalbuphine is effective in relieving pain in the first few days following PRK and this pain relief is not associated with any compromise regarding epithelial healing nor refractive outcome. The pain control with 2 mg/ml concentration is significantly higher than that with 1 mg/ml concentration of nalbuphine. Trial registration numberISRCTN21394752 https://doi.org/10.1186/ISRCTN21394752 The trial is retrospectively registered in ISRCTN registry at March 08, 2021.

Comparison of the effect of removing bandage contact lens on the days 3 and 5 following photorefractive keratectomy

AIM

To compare the outcomes of removing bandage contact lens (BCL) on days 3 and 5 after photorefractive keratectomy (PRK).

METHODS

One hundred patients who underwent PRK (a total of 200 eyes) were enrolled in the present study. The subjects were assigned to two groups. Group 1 consisted of the right eyes of subjects and bandage contact lenses removal were on the 3rd day; Group 2 consisted of the fellow eyes of same subjects and removed bandage contact lenses on the 5th day after PRK. Then, data obtained from both groups were compared. To evaluate complications, the subjects underwent a slit-lamp examination in all visits.

RESULTS

Filamentary keratitis was observed in one eye in both groups. The frequency of haze was higher in group 1; however, it was not significant between the two groups. Using mixed model analysis, significant differences were observed in the rate of complications as well as pain and eye discomfort scores between the groups (P < 0.05). No major complication was reported.

CONCLUSION

Majority of post-PRK corneal epithelial defect is healed on day 3. However, keeping BCL for 5 days postoperatively instead of the three days produces a slightly lower rate of total complication.

Impact of topical anti-fibrotics on corneal nerve regeneration in vivo

Recent work in vitro has shown that fibroblasts and myofibroblasts have opposing effects on neurite outgrowth by peripheral sensory neurons. Here, we tested a prediction from this work that dampening the fibrotic response in the early phases of corneal wound healing in vivo could enhance reinnervation after a large, deep corneal injury such as that induced by photorefractive keratectomy (PRK). Since topical steroids and Mitomycin C (MMC) are often used clinically for mitigating corneal inflammation and scarring after PRK, they were ideal to test this prediction. Twenty adult cats underwent bilateral, myopic PRK over a 6 mm optical zone followed by either: (1) intraoperative MMC (n = 12 eyes), (2) intraoperative prednisolone acetate (PA) followed by twice daily topical application for 14 days (n = 12 eyes), or (3) no post-operative treatment (n = 16 eyes). Anti-fibrotic effects of MMC and PA were verified optically and histologically. First, optical coherence tomography (OCT) performed pre-operatively and 2, 4 and 12 weeks post-PRK was used to assess changes in corneal backscatter reflectivity. Post-mortem immunohistochemistry was then performed at 2, 4 and 12 weeks post-PRK, using antibodies against α-smooth muscle actin (α-SMA). Finally, immunohistochemistry with antibodies against βIII-tubulin (Tuj-1) was performed in the same corneas to quantify changes in nerve distribution relative to unoperated, control cat corneas. Two weeks after PRK, untreated corneas exhibited the greatest amount of staining for α-SMA, followed by PA-treated and MMC-treated eyes. This was matched by higher OCT-based stromal reflectivity values in untreated, than PA- and MMC-treated eyes. PA treatment appeared to slow epithelial healing and although normal epithelial thickness was restored by 12 weeks-post-PRK, intra-epithelial nerve length only reached ∼1/6 normal values in PA-treated eyes. Even peripheral cornea (outside the ablation zone) exhibited depressed intra-epithelial nerve densities after PA treatment. Stromal nerves were abundant under the α-SMA zone, but appeared to largely avoid it, creating an area of sub-epithelial stroma devoid of nerve trunks. In turn, this may have led to the lack of sub-basal and intra-epithelial nerves in the ablation zone of PA-treated eyes 4 weeks after PRK, and their continuing paucity 12 weeks after PRK. Intra-operative MMC, which sharply decreased α-SMA staining, was followed by rapid restoration of nerve densities in all corneal layers post-PRK compared to untreated corneas. Curiously, stromal nerves appeared unaffected by the development of large, stromal, acellular zones in MMC-treated corneas. Overall, it appears that post-PRK treatments that were most effective at reducing α-SMA-positive cells in the early post-operative period benefited nerve regeneration the most, resulting in more rapid restoration of nerve densities in all corneal layers of the ablation zone and of the corneal periphery.

Comparison of bandage contact lens removal on the fourth versus seventh postoperative day after photorefractive keratectomy: A randomized clinical trial

PURPOSE

To compare the outcomes of bandage contact lens (BCL) removal on the fourth versus seventh post-operative day following photorefractive keratectomy (PRK).

METHODS

This study recruited eyes of patients who underwent PRK surgery. The patients were randomly assigned to 2 groups. In Group 1 BCL was removed on the 4th postoperative day, while in Group 2, BCL was removed on the 7th postoperative day. After BCL removal, patients were asked to express their pain score and eye discomfort. At one and three months follow-up examinations, visual acuity scale was assessed. Slit-lamp examination was performed in all visits to evaluate complications.

RESULTS

260 eyes of 130 patients underwent PRK. The age and sex ratio were not significantly different between the two groups. One month after the surgery, the logMAR uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were significantly lower in Group 2 (P value = 0.016, 0.001 respectively), however, the UDVA and CDVA were not significantly different after 3 months (P > 0.05). In Group 1, filamentary keratitis (FK) was observed in 10 (7.6%) eyes, 6 (4.61%) eyes were diagnosed with recurrent corneal erosion (RCE) and corneal haze was detected in 3 (2.3%) eyes. However, in Group 2, RCE was observed in 4 (2.3%) and FK was noted in 4 (3.07%) eyes. No haze was seen in Group 2. The difference in rate of complications was statistically significant (14.6% and 6.1% in Groups 1 and 2, respectively, P = 0.02). Pain and eye discomfort scores were not significantly different (P > 0.05). There was no major complications including infectious keratitis in either groups.

CONCLUSION

Following PRK surgery, BCL removal on the seventh postoperative day yields faster visual rehabilitation and lower rate of postoperative complications with no increase in eye pain, discomfort or infection.

Topical rosiglitazone is an effective anti-scarring agent in the cornea

Corneal scarring remains a major cause of blindness world-wide, with limited treatment options, all of which have side-effects. Here, we tested the hypothesis that topical application of Rosiglitazone, a Thiazolidinedione and ligand of peroxisome proliferator activated receptor gamma (PPARγ), can effectively block scar formation in a cat model of corneal damage. Adult cats underwent bilateral epithelial debridement followed by excimer laser ablation of the central corneal stroma to a depth of ~160 µm as a means of experimentally inducing a reproducible wound. Eyes were then left untreated, or received 50 µl of either 10 µM Rosiglitazone in DMSO/Celluvisc, DMSO/Celluvisc vehicle or Celluvisc vehicle twice daily for 2 weeks. Cellular aspects of corneal wound healing were evaluated with in vivo confocal imaging and post-mortem immunohistochemistry for alpha smooth muscle actin (αSMA). Impacts of the wound and treatments on optical quality were assessed using wavefront sensing and optical coherence tomography at 2, 4, 8 and 12 weeks post-operatively. In parallel, cat corneal fibroblasts were cultured to assess the effects of Rosiglitazone on TGFβ-induced αSMA expression. Topical application of Rosiglitazone to cat eyes after injury decreased αSMA expression and haze, as well as the induction of lower-order and residual, higher-order wavefront aberrations compared to vehicle-treated eyes. Rosiglitazone also inhibited TGFβ-induced αSMA expression in cultured corneal fibroblasts. In conclusion, Rosiglitazone effectively controlled corneal fibrosis in vivo and in vitro, while restoring corneal thickness and optics. Its topical application may represent an effective, new avenue for the prevention of corneal scarring with distinct advantages for pathologically thin corneas.

Comparison of optical quality parameters and ocular aberrations after wavefront-guided laser in-situ keratomileusis versus wavefront-guided laser epithelial keratomileusis for myopia

BACKGROUND

To compare optical quality, ocular scattering, and higher-order aberrations (HOAs) after laser in-situ keratomileusis (LASIK) versus laser epithelial keratomileusis (LASEK).

METHODS

A total of 47 eyes from 47 participants who had undergone LASIK (group I) or LASEK (group II) procedure at least 6 months prior were enrolled. Ocular aberrations and modulation transfer function (MTF) values measured using iTrace, a ray-tracing type aberrometer, were compared to MTF (modulation transfer function) cut-off values, Strehl ratio, and objective indices of scattering obtained using the Objective Quality Analysis System II (OQAS II).

RESULTS

There was no significant correlation between the postoperative optical quality parameters and the HOAs between both groups. In group I, the MTF cut-off value was significantly correlated with cylinder refraction (p = 0.037), and the objective scattering index (OSI) was positively correlated with spherical equivalent (p = 0.023). In group II, there was a statistically significant correlation between the OSI and achieved refractive correction (p = 0.001). Regression analysis showed that the OSI was the most significant predictor of MTF cut-off values after refractive surgery. Additionally, MTF values measured by OQAS were significantly lower than those measured by iTrace without correlation.

CONCLUSION

Optical quality after refractive surgery may be influenced by not only ocular aberrations but also by scattering. Even though the accuracies of the machines used in this study to measure optical quality have yet to be proven, this study showed limited correlation among the values measured using the two different machines after refractive surgery. Therefore, for more generalized evaluation of visual function after refractive surgery, more advanced optical devices still need to be developed.

Refractive Surgery in Children

Refractive surgery in children is controversial. The main indications are bilateral high ametropia and anisometropia where conventional treatment with spectacles or contact lens is not tolerated. Other reported indications include accommodative strabismus and previous cataract surgery. The most commonly performed procedures currently are surface ablation procedures using excimer laser. The main disadvantage of surface ablation procedures is refractive regression, which is more pronounced in higher degrees of ametropia. More recently, there is a growing number of studies evaluating the safety and effectiveness of phakic intraocular lenses (IOLs) as an alternative surgical management for children who are noncompliant with conventional treatment and unsuitable for laser ablative procedures. The advantages of phakic IOLs are reversibility, predictability, and lack of regression. The principal concern with phakic IOL insertion is long-term endothelial cell loss. Clear lens extraction has been performed in patients with shallow anterior chambers beyond the range of corneal laser refractive procedures; however, major drawbacks include loss of accommodation and significant risk of retinal detachment. In summary, results to date show that refractive surgery can be successfully performed in children and meets an important need in a select subgroup of patients who are recalcitrant to traditional therapy. Issues that remain controversial are the age at which to perform surgery, choice of procedure, need for anesthesia, instability of refractive errors in children, and long-term safety considerations.

Mitomycin C-assisted photorefractive keratectomy in high myopia: a long-term safety study

PURPOSE

To evaluate the long-term corneal safety of topical mitomycin C (MMC) used during photorefractive keratectomy to prevent haze formation in highly myopic eyes.

METHODS

Twenty-eight patients with bilateral high myopia underwent photorefractive keratectomy. One eye was randomly assigned to intraoperative 0.02% MMC and the fellow eye to conventional treatment. Each eye was checked at baseline and at 5 years after surgery using in vivo corneal confocal microscopy.

RESULTS

At baseline, the endothelial cell density was 2970 ± 295 cells per square millimeter in the MMC-treated eyes and 2839 ± 323 cells per square millimeter in the control eyes. At 5 years, it was 2803 ± 307 and 2780 ± 264 cells per square millimeter, respectively (P = 0.27). The number of corneal nerve fibers was 3.9 ± 1.6 in the MMC-treated eyes and 4.4 ± 1.3 in the control eyes. At 5 years, it was 3.0 ± 1.6 and 2.7 ± 1.3, respectively (P = 0.15). The density of corneal nerves was 9600 ± 2915 μm/mm(2) in the MMC-treated eyes and 11,352 ± 3898 μm/mm(2) in the control eyes. At 5 years, the density was higher in the MMC-treated eyes (6790 ± 2447 μm/mm(2)) than in the control eyes (6024 ± 2977 μm/mm(2)) (P = 0.003). The number of nerve beadings at baseline was 12.9 ± 1.7/100 μm in the MMC-treated eyes and 12.3 ± 2.0/100 μm in the control eyes. At 5 years, it was 9.9 ± 2.6/100 and 9.4 ± 2.9/100 μm, respectively (P = 1.00). At 5 years, corneal nerve branching and tortuosity were similar in the 2 groups (P = 0.88 and 0.54, respectively). Epithelium thickness remained statistically unchanged (P = 0.69).

CONCLUSIONS

Intraoperative use of topical 0.02% MMC compared with standard treatment does not induce significant long-term corneal changes, as assessed by in vivo corneal confocal microscopy.

Effect of basic fibroblast growth factor and cytochrome c peroxidase combination in transgenic mice corneal epithelial healing process after excimer laser photoablation

PURPOSE

To evaluate the role of prepared basic fibroblast growth factor (bFGF) and cytochrome c peroxidase (CCP) combination eyedrops in corneal epithelial healing of transgenic mice (B6(A)-Rpe(rd12)/J) after excimer laser photoablation.

MATERIALS AND METHODS

In this prospective study, 216 eyes of 108 mice underwent bilateral photorefractive keratectomy. We considered 4 groups: A, B, C, and D. Group A received standard topical postoperative therapy with tobramycin, diclofenac, and dexamethasone eyedrops plus CCP at 3 drops per day for a week or until corneal re-epithelialization was achieved. Group B received standard topical postoperative therapy plus bFGF eyedrops and phosphate-buffered saline (PBS) 3 drops per day for a week or until corneal re-epithelialization was complete. In group C, 1 eye received standard topical postoperative therapy plus CCP eyedrops, bFGF eyedrops, and PBS 3 drops per day for a week or until corneal re-epithelialization was complete. Control eyes (group D) received a standard topical postoperative therapy plus placebo eyedrops. Mice were followed-up for a week from the day after the surgery to evaluate the rate of corneal re-epithelialization.

RESULTS

Data were analyzed by ANOVA using the XLSTAT 2010 software. Eyes in group A, B, and C healed completely before the fifth postoperative day, achieving, respectively, a re-epithelialization time of 92 hours ± 10 SD, 90 hours ± 12 SD, and 86 hours ± 12 SD. Group D had a re-epithelialization time of 121 hours ± 8 SD (P < 0.05). No side effects or toxic effects were documented.

CONCLUSIONS

Results suggest that re-epithelialization after phototherapeutic keratectomy can benefit from topical therapy with CCP/bFGF combination eyedrops. Further clinical studies are needed to evaluate the long-term effectiveness of these eyedrops to prevent corneal haze.

Comparative in vivo confocal microscopical study of the cornea anatomy of different laboratory animals

PURPOSE

The aim of the present study was to analyze and compare in vivo morphology of healthy cornea of six different laboratory animals.

MATERIALS AND METHODS

One Pomeranian Coarsewool sheep, 5 Beagle dogs, 1 Norwegian and 2 Domestic Short-haired cats, 20 New Zealand White rabbits, 6 Wistar rats, and 10 Balb/c mice were included. The examination was performed bilaterally, using Heidelberg Retina Tomograph equipped with Rostock Cornea Module. The morphology of living corneal layers was visualized and compared between species. The central corneal thickness, density of keratocytes, and endothelial cells were quantified.

RESULTS

The epithelial multilayer showed a similarity in morphology between animal types, displaying three clearly distinguishable layers: superficial, intermediate, and basal. Subbasal nerve fibers were displayed as hyperreflective structures underneath basal cells. The subbasal fibers were confirmed in all species, however, the density varied between species. A pronounced Bowman's membrane was visualized in sheep. In all other species, however, a thin acellular layer with overlying nerve fibers could be seen between basal epithelial cells and anterior stroma. The keratocytes nuclei could be demonstrated in all species except for mice, where no nuclei but only reflective structures resembling keratocytes cell bodies were detected. Overall, the density of keratocytes nuclei was significantly higher in the anterior than in the posterior stroma. Besides endothelial cells density, the endothelial cells morphology was very similar among all species, except for sheep. The endothelial cells were displayed as polygonal structures with bright cytoplasm and dark borders. In sheep, the appearance of the endothelium was very poor because of a thick hyperreflective Descemet's membrane.

CONCLUSIONS

The present study will help researchers consider appropriate models for animal experiments, depending on focus of investigation. In vivo CLSM can be used for the characterization of the living cornea over time, thus, reducing the number of animal experiments.

Omega-3 fatty acids in dry eye and corneal nerve regeneration after refractive surgery

Dry eye (DE) is a multifactorial condition that affects the surface of the eye and induces an inflammatory response. Corneal nerves play an important role in the maintenance of a healthy ocular surface. Here we review corneal structure, nerve architecture, DE conditions, and nerve regeneration following corneal surgery and discuss how n-3 fatty acids affect the health of the cornea. Animal studies show that resolvins, compounds derived from eicosapentaenoic acid (EPA), increase tear volume and decrease inflammation induced by DE. After corneal surgery in rabbits, treatment with nerve growth factor (NGF) or pigment epithelial derived factor (PEDF) in conjunction with docosahexaenoic acid (DHA) increase nerve density and corneal epithelial cell proliferation. Increased synthesis of the novel docosanoid, neuroprotectin D1 (NPD1), was found in corneas after the animals were treated with PEDF and DHA. Topical application of these lipids derived from n-3 fatty acids could be useful in treating DE and prevent clinical complications such as cornea erosion and ulcerations.

Effect of topical 0.5% morphine on postoperative pain after photorefractive keratectomy

PURPOSE

To investigate safety and efficacy of 0.5% morphine drops for pain control after photorefractive keratectomy (PRK).

METHODS

In a double-blind prospective study, 40 patients were randomized to either 0.5% morphine drops (n=20) or vehicle control (n=20). Treatment occurred every 2 hours following PRK on the day of the procedure, then four times daily on postoperative days 1 through 3. Patients completed pain assessment questionnaires (visual descriptor, numerical rating, visual analog scales, and oral analgesic consumption) every 2 hours while awake during the treatment period. Daily average and maximum scores were compared between the two groups. Patients were examined daily for 4 days after PRK, weekly for 4 weeks, then monthly for 3 months. Epithelial healing, corneal haze, and refractive outcomes were compared.

RESULTS

Both average and maximum pain scores were lower in the morphine group than in the vehicle control group on all scales and during all 4 days after PRK. Statistical significance (P<.05) was reached on numeric rating scale on procedure day and on postoperative day 1. The difference between the groups on the visual analog scale was statistically significant on procedure day, and on postoperative days 1 and 2. Oral analgesic consumption was higher in the vehicle control group on postoperative day 2. No difference between groups was noted in epithelial healing or refractive outcomes. Stromal haze scores were lower in the morphine group, but the difference was not statistically significant.

CONCLUSIONS

Topical 0.5% morphine may be an effective and safe method of pain control after PRK.

Induction of corneal myofibroblasts by lens-derived transforming growth factor beta1 (TGFbeta1): a transgenic mouse model

PURPOSE

Transforming growth factor beta (TGFbeta) is an important cytokine in corneal development and wound healing. Transgenic mice that express an active form of human TGFbeta1 driven by a lens-specific promoter were used in the current study to determine the biological effects of lens-derived TGFbeta1 on postnatal corneal development and homeostasis.

METHODS

The postnatal corneal changes in the TGFbeta1 transgenic mice were examined by fluorescein labeling and histology. Epithelial/endothelial-to-mesenchymal transition (E/EnMT) in the transgenic mouse cornea was demonstrated by immunostaining for alpha-smooth muscle actin (alpha-SMA) and cadherin-11. Expression of E- and N-cadherin in the corneal epithelial and endothelial cells, respectively, was analyzed by in situ hybridization.

RESULTS

Among the established TGFbeta1 transgenic lines, mice from line OVE853 and OVE917 had normal-sized eyeballs but developed a corneal haze after eyelid opening. Histological examination showed that prenatal corneal development appeared to be normal. However, after postnatal day 7 (P7), the corneal endothelial cells in transgenic line OVE853 began to lose normal cell-cell contact and basement membrane structure. The endothelial layer was eventually absent in the inner surface of the transgenic mouse cornea. The morphological changes in the cornea correlated with abnormal expression of alpha-SMA, a molecular marker of EMT, and stress fiber formation in myofibroblast-like cells, which initially appeared in the corneal endothelial layer and subsequently in the corneal epithelial and stromal layers. The E/EnMT in the transgenic mouse cornea was further demonstrated by loss of E- and N-cadherin expression in the corneal epithelial and endothelial cells, respectively, and meanwhile increasing expression of cadherin-11 in both corneal epithelium and stroma.

CONCLUSIONS

Elevated levels of active TGFbeta1 in the anterior chamber can lead to myofibroblast formation in the corneal endothelial layer and subsequently in the corneal epithelial and stromal layers. Our data suggest that the levels of biologically active TGFbeta in the aqueous humor must be under tight control to maintain corneal homeostasis. TGFbeta1 is the major cytokine during wound healing. Therefore, our findings also suggest a potential mechanism to explain the loss of corneal endothelial barrier and corneal opacification after intraocular surgery or trauma.

Comparative study of higher-order aberrations after conventional laser in situ keratomileusis and laser epithelial keratomileusis for myopia using the technolas 217z laser platform

PURPOSE

To examine changes in higher-order aberrations (HOAs) after PlanoScan laser in situ keratomileusis and (LASIK) and laser epithelial keratomileusis (LASEK).

DESIGN

Prospective, comparative study.

METHODS

Myopic patients undergoing LASIK (65 eyes of 36 patients) and LASEK (50 eyes of 28 patients) at a private practice were selected randomly. Surgery was performed using the Technolas 217z laser (Bausch & Lomb, Surrey, United Kingdom). Main outcome measures included uncorrected visual acuity (UCVA), manifest refractive spherical equivalent (MRSE), and aberrometry (Zywave; Bausch & Lomb, Rochester, New York, USA) and were recorded before surgery and at three and 12 months after surgery.

RESULTS

There was no statistical difference between both groups in terms of MRSE (P = .91), ablation depth (P = .47), scotopic pupil size (P = .38), or optical zone (P = .07). Before surgery, there was no statistical difference in root mean square (RMS) of total (P = .70), third- (P = .79), fourth- (P = .23), and fifth- (P = .33) order aberrations and individual terms. Three months after surgery, RMS of total HOA was raised significantly more (P = .03) after LASIK (1.46-factor increase) than LASEK (1.25-factor increase). One year after surgery, a reduction in total HOAs was observed in 13.8% of LASIK- and 48.5% of LASEK-treated eyes compared with preoperative levels.

CONCLUSIONS

Postoperative increases in total HOA and vertical coma were significantly greater in LASIK- than in LASEK-treated eyes. Postoperative reduction in total HOAs was observed in a number of eyes with high preoperative levels and occurred more frequently in LASEK-treated eyes.

Epidermal growth factor synergism with TGF-beta1 via PI-3 kinase activity in corneal keratocyte differentiation

PURPOSE

To investigate the action of epidermal growth factor (EGF) on corneal keratocyte differentiation and its effects in conjunction with transforming growth factor (TGF)-beta1.

METHODS

Rabbit corneal keratocytes (RCKs) were treated with EGF, TGF-beta1, or EGF plus TGF-beta1 in the presence or absence of inhibitors of EGF-receptor (EGF-R), neutralizing concentrations of EGF antibody and of signaling kinases for 2 days to 1 week. RCK differentiation to myofibroblasts was identified with anti-aldehyde dehydrogenase (ALDH)-1 and alpha-smooth muscle actin (alpha-SMA) antibodies. Cell proliferation was evaluated with anti-Ki-67 antibody. Extracellular matrix (ECM) components were assayed by immunochemistry and Western blot. Cell migration images were captured with a camera attached to the microscope, and the area of the wound was calculated using imaging software.

RESULTS

RCKs cultured in serum-free DMEM/F12 without frequent changes of medium maintained the phenotype for more than 1 month. EGF stimulated differentiation into a proto-myofibroblast phenotype with the loss of dendritic shape and the expression of alpha-SMA. Treatment with TGF-beta1 stimulated 12% of the cells to differentiate to defined myofibroblasts, but in the presence of EGF, TGF-beta1 induced 90% of RCKs to transform into myofibroblasts. Inhibition of EGF-R activation and of the phosphatidylinositol-3 kinase (PI-3K)/Akt-1 pathway prevented the action of EGF on TGF-beta1 cell differentiation. TGF-beta1 in the presence of EGF also increased cell migration, which is inhibited by blocking EGF-R activation.

CONCLUSIONS

These data show that EGF contributes to the differentiation and migration of myofibroblasts induced by TGF-beta1 through EGF-R activation and that it is an important modulator of wound healing and scar tissue formation.

Mechanical corneal epithelium scraping and ethanol treatment up-regulate cytokine gene expression differently in rabbit cornea

PURPOSE

To explore inflammation and wound healing in the rabbit eye following topical ethanol treatment or mechanical debridement.

METHODS

Seventy-six pigmented rabbit corneas were divided into four groups: mechanical group (n = 33), which received mechanical epithelial debridement; ethanol-30 (n = 18) and ethanol-60 groups (n = 18), which were treated with 20% ethanol for 30 and 60 seconds, respectively; and control group (n = 7), which remained untreated. Corneal epithelial and stromal keratocyte changes were examined with hematoxylin-eosin and terminal deoxynucleotidyltransferase-mediated dUPT nick end labeling (TUNEL) staining at 3 hours (day 0) and days 1, 2, 3, 5, and 7. Interleukin (IL)-1alpha, IL-8, monocyte chemotactic protein (MCP-1), and transforming growth factor (TGF)-beta1 expression were examined using real-time polymerase chain reaction.

RESULTS

Stromal keratocyte cell death was higher in the mechanical group on day 0 (P = .002) and in the ethanol-60 group on days 3, 5, and 7 (P < .05). Keratocyte cell death was more pronounced in the ethanol-60 group than in the ethanol-30 group. In the mechanical group, IL-1alpha, IL-8, and MCP-1 expression was up-regulated starting on day 0 (P < .05) and returned to baseline on day 5 to 7. TGF-beta1 expression was up-regulated in the mechanical group throughout the experiment (P < .05). In the ethanol-30 and ethanol-60 groups, IL-1alpha expression was up-regulated on day 0, IL-8 expression was slightly up-regulated on day 0, and MCP-1 and TGF-beta1 expression were not up-regulated.

CONCLUSIONS

Mechanical epithelial removal initially induces more keratocyte cell death, but deep stromal keratocyte death persists longer with ethanol treatment. In this rabbit model, mechanical epithelial removal upregulated inflammatory cytokines and TGF-beta1 gene expression more than ethanol treatment.

Learning curve of laser-assisted subepithelial keratectomy

PURPOSE

To study the effect of the learning curve of laser-assisted subepithelial keratectomy (LASEK) on the visual and refractive results.

METHODS

This retrospective study comprised 56 eyes that had LASEK for myopia. The eyes were among the first 143 that had LASEK by the same surgeon with the same excimer laser and same nomogram. The 56 eyes were separated into 2 groups. Group 1 included the first 28 eyes to have LASEK by the surgeon. Group 2 comprised the last 28 eyes in the series whose refractive error could be matched with that in Group 1. The outcomes in the 2 groups were compared.

RESULTS

The mean preoperative spherical refraction was -3.90 diopters (D) +/- 1.90 (SD) in Group 1 and -3.70 +/- 2.53 D in Group 2 (P = .2). There were no significant differences in preoperative cylinder or best spectacle-corrected visual acuity (BSCVA) between groups. The postoperative uncorrected visual acuity (UCVA) was significantly worse in Group 1 on 1 day and 7 days postoperatively (P = .02 and P = .03, respectively); there was no significant difference at 1 month and 3 months. The safety index (postoperative BSCVA/preoperative BSCVA) and efficacy index (postoperative UCVA/preoperative BSCVA) were better in Group 2, although the difference was not statistically significant. The spherical refraction 3 months postoperatively was +0.50 +/- 0.83 D in Group 1 and +0.10 +/- 0.27 D in Group 2 (P = .02); 75.00% of eyes and 96.42% of eyes, respectively, were within +/-0.50 D of the intended correction (P = .01). Seven percent of eyes in Group 1 and no eye in Group 2 lost 2 or more lines of BSCVA.

CONCLUSIONS

Results indicate that the outcomes of LASEK depend on surgeon experience. Thus, caution is advised when interpreting LASEK results without knowing the surgeon's level of experience.

One-Year Clinical Results after Epi-LASIK for Myopia

PURPOSE

To evaluate the clinical results of epi-LASIK for the treatment of low to moderate myopia and myopic astigmatism.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Two hundred thirty-four eyes of 138 patients underwent epi-LASIK for the correction of low to moderate myopia. Mean preoperative spherical equivalent ranged from -1.0 to -7.25 diopters (D) (-3.74+/-1.46, mean+/-standard deviation [SD]) and baseline logarithm of the minimum angle of resolution (logMAR) best spectacle-corrected visual acuity (BSCVA) from 0.10 to -0.18 (mean+/-SD, 0.00+/-0.06).

METHODS

All enrolled eyes underwent epi-LASIK using the Centurion SES epikeratome (Norwood Abbey EyeCare, Victoria, Australia) and the Allegretto (Wavelight Laser Technologie AG, Erlangen, Germany) laser platform. The enrolled patients were followed up daily until the epithelial healing was complete as well as at the 1-, 3-, 6-, and 12-month postoperative intervals.

MAIN OUTCOME MEASURES

The main parameters assessed were subjective evaluation of postoperative pain, uncorrected visual acuity (UCVA) and BSCVA, manifest refraction, haze grade, and contrast sensitivity of the operated eyes.

RESULTS

The mean epithelial healing time was 4.70+/-0.87 days (range, 3-7 days), with mean logMAR UCVA on the day of reepithelization of 0.26+/-0.14 (range, 0.7-0.0). One year after the treatment, the spherical equivalent of the treated eyes (n = 222) ranged from -1.25 to +0.625 D (mean+/-SD, -0.18+/-0.6 D), with 80.33% of the eyes within 0.5 D (96.72% within 1 D) of the attempted correction. At the same interval, 86% of the eyes had clear corneas and 14% clinically insignificant (trace) haze, whereas 60% of the eyes had a line gain of 1 or more lines of BSCVA. Mean logMAR contrast sensitivity of the treated eyes at 4 different spatial frequencies was improved or remained unchanged throughout the follow-up period.

CONCLUSIONS

One-year visual and refractive results after epi-LASIK suggest that it is a safe and efficient method for the correction of low to moderate myopia and myopic astigmatism.

Effectiveness of laser-assisted subepithelial keratectomy to treat residual refractive errors after laser in situ keratomileusis

PURPOSE

To evaluate the effectiveness of laser-assisted subepithelial keratectomy (LASEK) to treat residual refractive errors after laser in situ keratomileusis (LASIK).

SETTINGS

Isik Eye Clinic, Ankara, Turkey.

METHODS

This retrospective study included 24 eyes of 15 patients who had retreatment by LASEK for residual refractive errors after myopic LASIK. All patients had examinations that included slitlamp biomicroscopy, subjective and cycloplegic refractions, uncorrected visual acuity (UCVA), best corrected visual acuity, corneal topography, and pachymetry preoperatively and postoperatively. Postoperative examinations were performed at 1 week and 1, 3, and 6 months.

RESULTS

The patient cohort comprised 9 men and 6 women. The median spherical equivalent (SE) of attempted correction for retreatment with LASEK was -1.25 diopters (D). The median follow-up after LASEK was 11.5 months (range 6 to 16 months). At the end of the follow-up, the median SE of the refractive error was -0.38 D. The median UCVA increased from 20/45 before LASEK to 20/25 at the last follow-up visit, which was statistically significant (P<.001). After LASEK, significant postoperative haze developed in 5 eyes. In all 5 eyes, the estimated ablation depth was more than 40 mum and the SE of attempted correction was -2.00 D or greater.

CONCLUSIONS

Laser-assisted subepithelial keratectomy retreatment in eyes with myopic regression after LASIK resulted in a significant improvement in UCVA that was comparable to the improvement after flap lifting. An SE of attempted correction greater than -2.00 D was associated with a significant rate of haze.

Effect of Cytochrome c Peroxidase on the Corneal Epithelial Healing Process after Excimer Laser Photo-Ablation in Transgenic Mice

AIM

To evaluate the role of commercially prepared cytochrome c peroxidase eye drops in corneal epithelial healing of transgenic B6(A)-Rpe65rd12/J mice after excimer laser photo-ablation.

MATERIALS AND METHODS

In our prospective animal series, 72 eyes of 36 mice had uneventful bilateral excimer laser photo-ablation. In each mouse, one eye received standard topical postoperative therapy with tobramycin, diclofenac, and dexamethasone eye drops plus cytochrome c peroxidase eye drops (two drops three times a day for 1 week or until corneal re-epithelialization was complete, corresponding to 15,000 IU/day). The fellow eye served as the control and received standard postoperative therapy plus placebo. The mice were monitored daily, commencing on the day after surgery, for 7 days to evaluate the corneal re-epithelialization rate using a video slit lamp camera with cobalt blue light. The mean diameter of the corneal wounds was measured. Videotaped images were recorded and analyzed by computer planimetry.

RESULTS

All eyes treated with cytochrome c peroxidase eye drops healed completely before day 5 after surgery, with a mean re-epithelialization time of 92 +/- (SD) 10 h; the mean re-epithelialization time was 121 +/- 8 h in the eyes receiving placebo (p < 0.05). There were no statistically significant differences between the two groups in corneal haze presentation during the follow-up period (p = 0.70), perhaps because the observation period was too short (7 days). However, the corneal clarity, on slit lamp biomicroscopy, in the study group was higher than that in the control group. No side effects or toxic effects were observed.

CONCLUSIONS

These data suggest that cytochrome c peroxidase significantly accelerates epithelial healing after phototherapeutic keratectomy. Further clinical studies should be performed to prove the results obtained in this study and the long-term efficacy of cytochrome c peroxidase to prevent corneal haze.

Pediatric refractive surgery

Refractive surgery in children is controversial; it is mainly performed when conventional treatment has failed. The primary indications are anisometropic amblyopia and bilateral high myopia. The major areas of concern are unstable refraction due to ongoing growth of the eye, and long-term implications. The most popular procedures are photorefractive keratectomy or laser-assisted subepithelial keratomileusis followed by laser-assisted in situ keratomileusis. There are technical difficulties involved in performing these procedures because of smaller palpebral apertures and the need for general anesthesia in younger children. Reports of minimal haze and regression in children who have undergone photorefractive keratectomy for high myopia are of interest, as this is contrary to what occurs in adults. Additional study may result in better long-term data and further indications for refractive surgery in children.

Ethanol Treatment Induces Significant Cell Death in Porcine Corneal Fibroblasts

PURPOSE

To explore the effect of ethanol treatment on corneal stromal cells.

METHODS

Primary porcine corneal fibroblasts from passages 3 to 5 were treated with ethanol at concentrations of 10%, 15%, 20%, and 50% for 30 seconds. A control group was treated with phosphate-buffered saline (PBS) for 30 seconds. Morphologic changes were documented with phase-contrast microscopy, and the growth curves were examined with a PicoGreen assay. Cellular viability was examined with an ethidium homodimer and calcein-AM stain, whereas cellular apoptosis and/or necrosis were analyzed by a YO-PRO-1 dye/propidium iodide apoptosis assay coupled with flow cytometry and further confirmed with a genomic DNA pattern assay. Cellular toxicity was examined with a lactate dehydrogenase (LDH) assay.

RESULTS

Significant cell rounding and detachment from the culture dish were noticed after 20% ethanol treatment of 30 seconds, despite that the cell morphology remained unchanged in the PBS and 10% and 15% ethanol groups. Twenty percent ethanol induced significant cellular toxicity, causing cell death as shown by ethidium homodimer and calcein-AM stain, YO-PRO-1 dye/propidium iodide apoptosis assay, and LDH assay, although 10% and 15% ethanol caused minimal changes to corneal fibroblasts. Cellular death was most significant 6 hours after the 20% ethanol treatment. The genomic DNA pattern revealed intact DNA in the control, 10% ethanol, and 15% ethanol groups at all times, whereas DNA smearing was noticed at 48 hours after the 20% ethanol treatment. However, none of the DNA examined revealed significant DNA laddering patterns of apoptosis. Fifty percent ethanol treatment of 30 seconds resulted in cell fixation and cell death.

CONCLUSION

Treatment with 20% ethanol for 30 seconds induced significant porcine corneal fibroblast cell death, whereas 10% and 15% ethanol treatment of 30 seconds caused minimal changes. We propose that, when applied for 30 seconds, 20% ethanol is the threshold level that causes cell death in cultured porcine corneal fibroblasts.

Development of late-onset subepithelial corneal haze after laser-assisted subepithelial keratectomy with prophylactic intraoperative mitomycin-C

We present a case of dense, visually significant reticular haze that developed approximately 17 months after uneventful laser-assisted subepithelial keratectomy with mitomycin-C (MMC). The patient was successfully treated with manual debridement coupled with phototherapeutic keratectomy and intraoperative MMC.

Corneal melting associated with topical diclofenac use after laser-assisted subepithelial keratectomy

We report a case of corneal melting associated with topically applied preservative-free diclofenac (Voltaren Ofta) after laser-assisted subepithelial keratectomy. Keratolysis was detected on day 5; further progression toward perforation was arrested by immediate suspension of diclofenac and prescription of topical dexamethasone with 24-hour patching. At the last follow-up, the visual acuity had improved from counting fingers to 20/20. Preservative-free diclofenac instillation had never been associated with keratolysis. Topical steroids may be useful in treating corneal melting associated with nonsteroidal antiinflammatory drugs.

Effects of Antibiotics and Corticosteroid Eyedrops on Cellular Proliferation in Cultured Human Corneal Keratocytes

The purpose of this study is to investigate the effects of antibiotics and glucocorticoid eyedrops, including gentamicin, sulfisomezole, fluorometholone, dexamethasone, and betamethasone, on cellular proliferation in cultured human corneal keratocytes. Human corneal keratocytes were cultured in RPMI-1640 containing 10% fetal bovine serum. Drugs were prepared from original concentrations to 1/10, 1/100, and 1/1,000 dilutions. After exposure to drugs for 100 minutes, cellular proliferation was estimated by [3H]-thymidine uptake. It was found that cellular proliferation in corneal keratocytes was not affected by any of the three dilutions of gentamicin but was inhibited by 1/10 and 1/100 dilutions of sulfisomezole to 82% and 90% of control. [3H]-thymidine uptake values were inhibited to 75% by 1/10 dilution of fluorometholone and by 1/10and 1/100 dilutions of betamethasone to 84% and 86% of control. Meanwhile, cellular proliferation was significantly inhibited by 1/10, 1/100, and 1/1,000 dilutions of dexamethasone to 82%,86%, and 90%, respectively, in comparison with control values. It was demonstrated that commercial eyedrops of glucocorticoids inhibit cellular proliferation in corneal keratocytes, which may modulate the wound healing of corneal stroma.

Epipolis laser in-situ keratomileusis: an evolving surface ablation procedure for refractive corrections

PURPOSE OF REVIEW

The aim of this article is to provide an update on epipolis laser in-situ keratomileusis--an alternative surface photorefractive surgical technique for the correction of myopia.

RECENT FINDINGS

In-vivo studies on animal models provide evidence that the replacement of the epithelial sheet on an ablated cornea can control corneal wound healing. Preliminary clinical data confirm that epipolis laser in-situ keratomileusis can provide excellent long-term visual and refractive results. The problems of late visual rehabilitation and postoperative pain, however, have not yet been fully addressed.

SUMMARY

Being a recently introduced surgical photorefractive technique for ametropias correction, epipolis laser in-situ keratomileusis is a fast evolving area of interest for refractive surgeons.

Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism

PURPOSE

To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty.

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation.

RESULTS

The mean preoperative spherical equivalent (SE) was -3.50 diopters (D) +/- 3.97 (SD) (range +1.625 to -9.25 D). The preoperative cylindrical error was -7.2 D (range -2.75 to -13.5 D). The programmed laser correction was -3.14 D (range +1.62 to -9 D) with a maximum attempted cylindrical correction of -7 D. Adherent LASEK epithelial flaps along suture lines and the graft-host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was -1.08 +/- 1.85 D (range +3 to -4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within +/-1 D of the intended correction. The mean postoperative cylindrical error was -2.72 D (range -0.5 to -6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection.

CONCLUSIONS

Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC.