Human tear fluid PDGF-BB, TNF-alpha and TGF-beta1 vs corneal haze and regeneration of corneal epithelium and subbasal nerve plexus after PRK.

The aim was to determine the association of tear fluid cytokine levels and post-PRK corneal haze evaluated by in vivo confocal microscopy. In addition, the possible association between subbasal neural regeneration and haze formation, or epithelial regeneration were investigated. Twenty eyes of 20 patients (16 women and four men, age 30.7 +/- 7.5 years, range 21-48 years) underwent a myopic PRK. The spherical equivalent (SE) of the intended correction was -4.7 +/- 1.5 D (range -2.75 to -9.00 D). ELISA-methods were used to assess tear fluid concentrations of TGF-beta1, PDGF-BB and TNF-alpha pre-operatively, and post-operatively on day 2 and at 3 months. Tear fluid flow in the collection capillary was recorded, and rates of cytokine release (= tear fluid flow-corrected concentrations) were calculated. In vivo confocal microscopy was performed at 3 months to evaluate the corneal morphology and to determine numerical haze estimate. There was wide interindividual variation between pre-operative and post-operative concentrations and rates of release of TGF-beta1, PDGF-BB and TNF-alpha. Subepithelial haze was observed in all corneas and the mean haze estimate was 506 +/- 401 U (100-1410 U). However, no association was found between tear fluid cytokine levels and post-PRK haze. Regenerating subbasal nerve plexus was found in 18 out of 20 corneas; in two corneas it was absent or could not be visualized due to subepithelial haze. The density of the subbasal nerve fiber bundles had a positive correlation with the epithelial thickness (Pearson correlation, r = 0.56, P = 0.011), but not with the haze estimate or the thickness of the haze area. At 3 months post-PRK, haze could be observed in all patients. The results suggest that tear fluid cytokine analysis, as measured, may not be suitable for screening the potential candidates for haze formation. We did not find any correlation between haze and regeneration of subbasal nerve plexus, but we demonstrated that the regeneration of subbasal nerve plexus might have significant influence on regulation of epithelial healing.

Corneal morphology and sensitivity in lattice dystrophy type II (familial amyloidosis, Finnish type).

PURPOSE: To describe the corneal abnormalities and to measure different modalities of corneal sensitivity in corneal lattice dystrophy type II (familial amyloidosis, Finnish type, also known as gelsolin-related amyloidosis and originally as Meretoja syndrome). METHODS: Twenty eyes of 20 patients were examined by in vivo confocal microscopy and noncontact gas esthesiometry. RESULTS: Pleomorphism of, and dense deposits between or posterior to, the basal epithelial cells were frequently observed, as well as a reduction of long nerve fiber bundles in the subbasal nerve plexus. The anterior stroma was altered in most cases, with fibrosis and abnormal extracellular matrix. In 15 corneas, thick anterior and midstromal filaments, corresponding to lattice lines, and in 11 corneas, thin undulated structures were observed. The average mechanical sensitivity threshold of 12 subjects was increased, and in the remaining 8 subjects there was no response, even to the highest intensity of stimuli used. Three patients did not respond to CO(2), 11 to heat, and 2 to cold, but those patients who responded had normal thresholds. Patients with more long nerve fiber bundles per confocal microscopic image had better mechanical and cold sensitivity than patients with fewer nerve fiber bundles. CONCLUSIONS: Lattice lines seem to be related to amyloid material and not to corneal nerves. However, the subbasal nerve density appears reduced, which results mainly in a decrease in mechanical and, to a lesser extent, thermal sensitivity. The location of stromal filaments and undulated structures changes with increasing age.

Photorefractive keratectomy in ophthalmic residents.

PURPOSE: To find out how ophthalmologists themselves experience the correction of myopia after photorefractive keratectomy. Visuomotor functions were of special interest. METHODS: Four ophthalmology residents and one medical engineer underwent photorefractive keratectomy for myopia. Objective measurements including refraction, corneal topography, perimetry, contrast sensitivity, pattern visual evoked potentials, in vivo confocal microscopy, and a car driving simulator test were performed preoperatively, postoperatively, and at 6 months. Subjective evaluation was reported. RESULTS: Performing ophthalmological examinations and microsurgery without spectacles was easier postoperatively and was appreciated by the four ophthalmology residents. Minimal haze formation, good accuracy, and normal performance in the car driving simulator were also observed. Visual fields, contrast sensitivity, and pattern visual evoked potentials did not show changes. Negative observations included postoperative pain for 2 to 4 days, dry eye symptoms, a period of anisometropia between operations, and hypersensitivity of the lids. CONCLUSIONS: The four ophthalmic residents were satisfied with the outcome of their refractive surgery. Low to moderate myopic correction did not affect the objective measurements of high and low contrast sensitivity, pattern visual evoked potentials, or simulated car driving in dark illumination.

Laser in situ keratomileusis flap margin: wound healing and complications imaged by in vivo confocal microscopy.

PURPOSE: To examine the healing response of laser in situ keratomileusis flap margin in vivo. METHODS: Forty-three eyes of 43 patients who had undergone myopic (n = 39) or hyperopic (n = 4) laser in situ keratomileusis were examined once after surgery. The flap margin was imaged by in vivo confocal microscopy at various depths, and the wound healing response, flap alignment, and complications were evaluated. Ten eyes were examined on day 3 postoperatively, 13 eyes at 1 to 2 weeks, 10 eyes at 1 to 2 months, five eyes at 3 months, and five eyes at 6 months or later. RESULTS: At 3 days after laser in situ keratomileusis, the surface epithelium and basal epithelium appeared normal. Keratocyte activation was strongest at 1 to 2 weeks and 1 to 2 months, and an increased amount of haze was observed correspondingly. Intrastromal epithelial cells forming a plug could occasionally be perceived in the wound gape. Wound constriction was completed in most cases by 3 to 6 months or later. Good alignment was observed in 12 of 43 flaps (27.9%) and moderate and poor alignment in 17 of 43 flaps (39.5%) and 13 of 43 flaps (30.2%), respectively. Poor alignment was not associated with lamellar epithelial ingrowth. Epithelial ingrowth was associated with dense haze at the interface. Diffuse lamellar keratitis was imaged in two corneas after hyperopic laser in situ keratomileusis. CONCLUSIONS: The laser in situ keratomileusis incision wound at the flap margin appears to heal after the sequence observed in incisional wounds in nonhuman primates. Complications, such as lamellar epithelial in growth and diffuse lamellar keratitis, were often observed, particularly after hyperopic laser in situ keratomileusis.

Confocal microscopy of a patient with irregular astigmatism after LASIK reoperations and relaxation incisions.

PURPOSE: Laser-assisted in situ keratomileusis (LASIK) is widely used for correcting refractive errors. If the predicted refractive result is not achieved after the first operation, a re-operation can be performed by ablating more stromal tissue after reopening the flap. The goal of this study was to analyze, by using in vivo confocal microscopy, the morphologic changes associated with repeated LASIKs. METHODS: Clinical examination, computed corneal topography, and real-time in vivo confocal microscopy were performed on both eyes of a 50-year-old patient with induced irregular astigmatism leading to decreased best-corrected vision in the left eye after LASIK. The left cornea had been operated on 5 times (LASIK with two reoperations followed by two relaxing incisions), and the right cornea twice (LASIK with one reoperation). RESULTS: Microfolds at the level of the Bowman's layer and highly reflective particles at the flap interface were observed in both corneas. The subbasal nerve plexus was severed in the left eye. In addition, we identified epithelial material in the flap margin and inside one of the two relaxing incisions placed inferotemporally. CONCLUSION: Repeated LASIKs may stretch the flap and result in microfolding at the Bowman's layer. This and deposition of particles in the flap interface may increase with the number of reoperations, challenging the healing response. Microfolding and occurrence of foreign material in the interface may add to the irregular astigmatism and poor visual outcome after LASIK. Clinical in vivo confocal microscopy offers new possibilities for the assessment of ultrastructural changes after corneal refractive surgery.

Corneal wound healing after laser in situ keratomileusis in rabbits.

BACKGROUND: The aim of this study was to characterize the cell biology of wound healing in rabbit corneas subjected to laser in situ keratomileusis (LASIK). METHODS: Rabbit corneas underwent LASIK with various multizone photoablations or only a lamellar keratotomy followed by repositioning of the flap. We looked for indications for an active wound healing process. Immunohistochemistry for the extradomain A cellular fibronectin (EDA-cFn) or tenascin (Tn) and routine histology were examined. RESULTS: Four days after LASIK or lamellar keratotomy followed by repositioning of the flap, epithelial plugs and prominent keratocytes as well as Tn and EDA-cFn immunoreactions-indicative of a wound-healing process-appeared in the wound margins. Epithelial plugs were less conspicous, and prominent, presumably activated, keratocytes were no longer identified at the wound margin at 2.5 and 5 months after wounding. However, EDA-cFn and Tn immunoreactivities could still be observed. Only the stromal cells located in the periphery of the flap and in relatively close contact with the epithelium were surrounded by scar tissue expressing immunoreactivity for EDA-cFn or Tn. The central corneal stroma was devoid of scar tissue. CONCLUSION: Results indicate that the wound healing reaction after LASIK takes place only at the periphery of the microkeratome wound, leaving the central optical zone clear.

Recovery of corneal nerve morphology following laser in situ keratomileusis.

Morphological changes in the corneal nerves after laser in situ keratomileusis (LASIK) were investigated and the changes were compared with those observed after creation of the keratectomy flap without subsequent photoablation. After creating the hinged flap, a multizone excimer laser photoablation (myopic correction from 6.00 to 6.66 D; diameter 6 mm) was performed on 27 rabbit corneas. Seven of these 27 rabbits received an automated keratectomy without laser photoablation on the fellow eye. A histochemical acetylcholinesterase reaction was used to demonstrate the changes in the morphology of the corneal nerves 3 days, 2.5 and 5 months after the operations. In all specimens the deepest stromal nerve bundles showed normal morphology. Cut nerve trunks were found at the wound margins and at the level of the flap interphase in the stromal bed. At 3 days, both epithelial and basal epithelial/subepithelial nerves were found at the hinge of the flap but the rest of the flap showed a major loss of epithelial, basal epithelial/subepithelial and superficial stromal nerves. A few new regenerating thin nerve fibers were found to emerge from the cut stromal nerve trunks. They appeared to pass the wound margin into the flap area below the epithelium. At 2.5 and 5 months an increasing number of regenerating nerve leashes were observed to emerge from the cut stromal nerve trunks. They appeared to send anastomosing fibers among the neighboring stromal nerves. By this time the epithelial, basal epithelial/subepithelial and anterior stromal innervation had gained an almost normal nerve density and architecture. In the corneas with the flap only, the epithelial innervation was slightly better spared in the center of the flap, and the stromal changes were somewhat less prominent compared with the LASIK corneas.

Photoastigmatic keratectomy for correction of astigmatism in corneal grafts.

BACKGROUND: The efficacy and safety of excimer laser photoastigmatic refractive keratectomy (PARK) for treatment of astigmatism after penetrating keratoplasty (PKP) was evaluated in this study. METHODS: A VisX 20/20 excimer laser was used to correct the regular astigmatic component of the grafts. The epithelium was removed manually in seven cases and in three patients with the PTK mode of the laser. The results were analyzed for uncorrected visual acuity (UCVA), best corrected acuity (BCVA), haze, and changes in the cylinder and axis. The vectorial change in astigmatism was measured using Alpins' method. RESULTS: Preoperative astigmatism ranged from 3.50 to 11.25 D (mean, 5.98 +/- 2.28) and the mean attempted correction of astigmatism was 6.28 +/- 1.56 D (range, 3.50-9.00 D). The induced reduction of net corneal astigmatism was 48.1%. The vector-corrected astigmatism, which was 6.40 +/- 3.49 D at 1 month postoperatively, was reduced at 12 months to 4.28 +/- 2.42 D. The Alpin Success Index varied in the range 0.06 to 1.0. Although the UCVA improved by > or = 2 lines in 60% of the eyes, the BCVA decreased in 40% of the eyes and three patients required a reoperation. CONCLUSION: Although PARK is relatively safe and effective in reducing post-PKP cylinder and improves UCVA, the frequently and surprisingly late-developing corneal haze often impairs the BCVA.

Schirmer test values and the outcome of photorefractive keratectomy.

PURPOSE: To evaluate whether relative tear deficiency, indicated by low standardized Schirmer test values, influences the outcome of photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, University of Heisinki, Finland. METHODS: Sixty-two patients were pair-matched by age and attempted myopic correction. They were divided into two groups: Group 1 (n = 31) comprised patients with standardized, eye-closed Schirmer test values of < or = 6 mm/5 min; Group 2 (n = 31), patients with Schirmer test values of > or = 10 mm/5 min. None of the eyes showed clinical signs of dry eye on slitlamp examination. Follow-up was 12 months. RESULTS: At 1 year, the visual acuity was 0.5 or better in 68.4% of Group 1 eyes and in 78.9% of Group 2 eyes. In Groups 1 and 2, 55.6% of eyes and 52.6%, respectively, were within 1.50 diopter (D) of attempted correction and 83.3% and 89.5%, respectively, were within 1.00 D. At 6 months, the mean overcorrection was + 1.32 +/- 1.13 D in Group 1 and + 0.77 +/- 0.57 D in Group 2 and at 1 year, + 0.96 +/- 1.13 D and +0.58 +/- 0.37 D, respectively. There was no difference between the two groups in visual acuity and obtained refractive correction or haze score at any postoperative examination. The minor tendency toward overcorrection in Group 1 could not be confirmed statistically. CONCLUSION: Subclinical tear deficiency indicated by low Schirmer test values did not influence the PRK outcome in patients matched by age and magnitude of refractive correction.

Release of calcitonin gene-related peptide in tears after excimer laser photorefractive keratectomy.

BACKGROUND: Sensory nerves known to affect corneal healing are damaged to a variable degree after photorefractive keratectomy (PRK). To search for nerve-bound factors involved in corneal healing, we monitored tear fluid calcitonin gene-related peptide (CGRP) levels of six human eyes undergoing PRK. METHODS: CGRP concentrations were determined using an immunoassay. RESULTS: Normal human tear fluid contains CGRP. The mean CGRP concentration was slightly increased postoperatively, despite a marked tear fluid hypersecretion. Consequently, an almost ten-fold increase in release of CGRP in tears was observed on days 1 and 2 after PRK. Values measured on day 7 had returned to a normal level. CONCLUSION: The observed postoperative increase in release of CGRP in tears may have an impact on the healing of PRK wounds. Extensive neural damage following deep photoablations may impair healing and should probably be avoided.

Excimer laser phototherapeutic keratectomy for corneal diseases: a follow-up study.

We performed phototherapeutic keratectomy (PTK) in 39 eyes of 38 patients with various corneal diseases. Patients were divided into four diagnostic entities: group 1 consistent of 11 eyes with postinfectious or posttraumatic corneal scars; 15 eyes with various corneal dystrophies or keratopathies comprised group 2; group 3 consisted to two eyes with recurrent corneal erosion; and 11 eyes with either primary or recurrent pterygia composed group 4. Postoperative follow-up ranged from 3 to 15 months (mean: 9 months). The goals of PTK (visual improvement, ocular comfort, or visibility for cataract extraction) were set individually for each patient and were achieved in 19 of 38 eyes (50%); one patient was lost to follow-up. Preoperatively, best corrected visual acuity improved two or more Snellen lines in nine of 31 eyes (29%). Both cases of recurrent corneal erosions were successfully treated. One eye lost two Snellen lines because of increased irregular astigmatism after PTK. In two eyes, corneal decompensation was observed 1 month after the operation, but no other serious complications were observed. The excimer laser was combined with surgical abrasions or use of topical EDTA, with good results. The excimer laser is a valuable tool for treating anterior corneal irregularities. It can also be combined with existing surgical methods. However, results can be improved with better patient selection criteria and by evaluating PTK on the basis of visual expectations and type and location of corneal pathology.

Recovery of corneal innervation following photorefractive keratoablation.

OBJECTIVE: To study the morphological recovery of rabbit corneal nerves for up to 12 months after photorefractive keratoablation. METHODS: The histochemical acetylcholinesterase reaction was used to demonstrate morphological features in rabbit corneal nerves at 1 hour, at 6 weeks, and at 3, 6, or 12 months after photorefractive keratoablation. RESULTS: Photorefractive keratoablation ablated the subepithelial nerve plexus, leaving sharply cut stromal nerves. Epithelial innervation was almost completely restored in 3 months, with innervation proceeding from the epithelial nerve plexuses at the wound margins, but the stromal nerves showed abnormal morphological features throughout the study. Abnormally coiled, regenerating axons emerged from the cut stromal nerves. The first of them were observed to penetrate into the epithelium 3 months postoperatively. The acetylcholinesterase reaction of the epithelial cell membranes was weaker in the wound area, except in the specimens that were observed at 12 months. CONCLUSIONS: Epithelial innervation was restored relatively quickly; otherwise, neural recovery was slow. The structure and architecture of the stromal nerves was abnormal even in the the specimens that were observed at 12 months. We hypothesize that corneal nerve damage induced by deep photoablations may correlate with the predictability problems and haze.