Corneal wound healing and immunohistological features of extracellular matrix following penetrating keratoplasty in rabbits]

PURPOSE: To analyze corneal wound healing after penetrating keratoplasty (PKP). MATERIALS AND METHODS: We performed PKP on 20 white rabbit eyes, and applied immunohistochemical techniques. The distribution of type I, III and IV collagens, large proteoglycan, chondroitin 6-sulfate, chondroitin 4-sulfate, and vimentin was determined at postoperative intervals of 3 days, 1 week, 2 weeks, 1 month and 3 months. RESULTS: By day 3, staining for type IV collagen was observed along the host-graft junction. By day 7, staining for type III collagen, large proteoglycan and chondroitin 6-sulfate had increased in the repair region, and then diminished with increasing postoperative time. Epithelial wound healing required more than one month, whereas the remodeling of Descemet's membrane did not terminate at 3 months after PKP. CONCLUSION: The data from this study suggest that type III collagen, large proteoglycan and chondroitin 6-sulfate play a crucial role in the corneal wound healing after PKP.     

Corneal wound dehiscence after penetrating keratoplasty

PURPOSE: To describe the clinical features of corneal wound dehiscence after penetrating keratoplasty (PK) after trauma and suture removal. METHODS: A retrospective review of all eyes needing resuturing in the 5-year period of July 2000 to June 2005 was performed. In total, 76 eyes of 76 patients needed wound resuturing. The indications were early wound leak, wound dehiscence, broken suture, or loose suture. In 29 of the 76 cases, the indication for resuturing after PK was wound dehiscence. Of these, 19 were caused by trauma, and in 10 eyes, dehiscence shortly followed suture removal. RESULTS: The interval between original PK and traumatic wound dehiscence caused by trauma ranged from 15 days to 33 years. In 5 eyes, it was >15 years. Nine eyes (47%) with traumatic dehiscence had final visual acuity better than 6/60, whereas 8 eyes (80%) with suture removal dehiscence had final visual acuity better than 6/18. Most of the dehiscence in the traumatic group was located in the inferior 2 quadrants, in contrast to temporally in the postsuture removal group. The time interval between PK and suture removal in the postsuture removal group was 16 +/- 4 months, and 7 (70%) patients had a continuous suture. Post-suture removal dehiscence was more common when corneal edema was the indication for grafting. CONCLUSIONS: Eyes with traumatic wound dehiscence have worse visual outcome than those with dehiscence after suture removal. Patients should be cautioned about the risks and consequences of wound dehiscence. The suture may be left in place longer in older patients or when corneal edema is the indication for grafting.     

Corneal wound healing after penetrating keratoplasty with EGF application. Experimental studies

PURPOSE: To check post penetrating keratoplasty (PK) corneal wound healing characteristics after epidermal growth factor (EGF) application and to compare it with controls. MATERIAL AND METHODS: The PK was performed in the group of 72 young, healthy New Zealand rabbits (36 females and 36 males). Slit-lamp examination, tonometry and corneal topography by Tomey's corneal modeling system (TMS-1) were carried out before and after surgery. The PK was performed in both eyes. Half of animals were used as a bilateral donor for the other half, with a rule: right eye cornea to the right eye and left eye cornea to the left eye. As a result, after completed surgery 36 rabbits had bilateral grafts. The animals were divided into 3 equal groups (12 in each). Two drops of the human recombined EGF dissolved in the saline solution with concentration varied from 500 to 1500 ng in each drop were applied to the right eye according to schedule. The left eye was used as a control and did not receive EGF. Time of observation varied from 24 hours to 6 months. The tensinometry and the histopathologic study--light and electron microscopy were performed to determine corneal scarring. RESULTS: The wound healing pattern after PK was characteristic and constant in each group. The corneal wound healing significantly accelerated in the EGF treated group of rabbits compared with the controls (p < 0.05). In the group of rabbits receiving 1000 ng of hrEGF 3 times/day, after two weeks of application we noted increase of the wound strength up to 600 folds, comparing with controls. Well-organized scar was histologically seen on the 21st post-surgery day. The post-operative corneal astigmatism was less expressed in the eyes treated with EGF comparing to controls. CONCLUSIONS: These preliminary results of our experimental study indicated accelerated effect on the corneal wound healing after PK with topical, low dose hrEGF application. Clinical observation of utilization of similar low doses of the hrEGF after PK--is in progress.     

Corneal epithelium following penetrating keratoplasty.

AIMS--This study was designed to observe any changes to the corneal epithelium after penetrating keratoplasty. METHODS--The corneal epithelia of 26 patients were observed by specular microscopy 1 week, 1 month, 3 months, and 6 months following penetrating keratoplasty. RESULTS--After re-epithelialisation was confirmed by biomicroscopy 1 week after surgery, specular microscopy revealed many abnormal cells, including spindle shaped cells, nucleated cells, large cells, as well as irregular cell configurations. Although these abnormal findings tended to decrease with time, they were still present in some cases as much as 6 months postoperatively. Computerised morphometric analysis yielded mean cell areas of 1121 (SD 168) microns 2, 1139 (675) microns 2, 1712 (496) microns 2, and 1400 (377) microns 2 at 1 week, 1 month, 3 months, and 6 months respectively, all significantly greater than that of age matched controls (710 (151) microns 2). The shape factor decreased with time, but was still greater than the control level at 6 months. CONCLUSIONS--This study demonstrates that epithelial abnormalities persist longer than expected after penetrating keratoplasty, and that these subtle changes can be detected by specular microscopic observation, potentially allowing for modification and enhancement of the wound healing process.     

Corneal wound healing after experimental penetrating keratoplasty after excimer laser trephination in free form

BACKGROUND: The postoperative clinical course after penetrating keratoplasty and trephination in free form using a guided excimer laser beam has been published before. Here the findings of light-microscopy comparing corneal wound healing after experimental penetrating keratoplasty after laser trephination and after conventional mechanical trephination are presented. MATERIALS AND METHODS: Homologous penetrating keratoplasty was performed on 12 NZW rabbits (6 animals with mechanical trephination, 6 animals with excimer laser trephination). The cutting edges achieved by both trephination techniques were examined by light microscopy in the remaining donor rings. During the postoperative follow-up animals were sacrificed at 3 and 6 weeks and at 3 months. Corneal specimens were retrieved and corneal healing processes were evaluated by light microscopy. RESULTS: The cutting edges of corneal excisions with the excimer laser demonstrated a high precision with only minimal collateral damage to adjacent tissue structures. At the different intervals both trephination groups demonstrated comparable stages of corneal wound healing regarding epithelial regeneration, stromal fibroblast migration with collagen synthesis and Descemet repair by endothelial synthesis of basement membrane. After 6 months corneal specimens of both groups demonstrated complete healing with nearly parallel orientation of newly synthesised collagen lamellae. Corneal thickness in the wound areas did not differ significantly from normal corneal tissue. CONCLUSIONS: Experimental follow-up studies to evaluate the feasibility of the developed technology of laser trephination in the living eye have shown no differences between conventional mechanical and excimer laser trephination with a guided beam. The present histology study also does not demonstrate any significant differences in corneal wound healing between the two trephination groups. Although excimer laser trephination along metal masks has now been established for several years, the here presented technique for trephination with individualised transplant geometries appears to be a valuable addition to the surgical repertoire in the presence of selected corneal pathologies.     

Excimer laser trephination in penetrating keratoplasty. Morphologic features and wound healing

The imprecision of trephination of donor and recipient corneas is a major factor in post-keratoplasty astigmatism. In order to improve the quality of trephination, the authors developed a rotating slit delivery system for noncontact penetrating keratoplasty trephination using the excimer laser at 193 nm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and light microscopy (LM) demonstrated the superior quality of excimer-cut buttons and recipient beds as compared with those obtained by free hand and suction trephines in human cadaver and rabbit eyes. The laser trephined more regularly and precisely without distortion of corneal topography and with less damage to adjacent corneal tissue. The authors morphologically examined wound healing at 6 hours, 12 hours, 3 days, 5 days, 2 weeks, 2 months, and 3 months after penetrating keratoplasty with laser and mechanical trephination in an animal autograft model. The laser did not cause any adverse alteration of wound healing processes including cellular migration, proliferation, and production of new tissue.     

Traumatic wound dehiscence following penetrating keratoplasty

BACKGROUND AND PURPOSE: Blunt ocular trauma to a corneal transplanted eye represents a higher risk for wound rupture at the donor-recipient interface. We have evaluated the causes, clinical characteristics, treatment and outcome, particularly the graft's clarity, in patients with traumatic wound dehiscence after penetrating keratoplasty. METHODS: Between March 1996 and April 2006, over a period of 10 years, 4 patients who had previously undergone successful penetrating keratoplasty and subsequently sustained traumatic wound dehiscence were treated at our department. All eyes underwent primary wound closure with interrupted 10-0 nylon sutures. RESULTS: Over the 10-year period, the incidence of traumatic wound dehiscence in which penetrating keratoplasty was performed was 2.35 % (4 of 170 patients). The ages of our patients at the time of injury were 6, 76, 78 and 39 years. The interval between penetrating keratoplasty and trauma varied from 12 through 16 and 17 to 30 months. All corneal dehiscences occurred at the graft-host junction. All dehiscences were at the temporal-superior quadrant (4 of 4 eyes) and at superior-nasal and temporal quadrants in 3 of 4 eyes. Two eyes that were pseudophakic had lost their implants and required anterior vitrectomy. In one of these patients (a 76-year-old women) delayed-onset expulsive choroidal haemorrhage occurred at the end of surgical repair. Visual outcome was correlated with the force of trauma, previous eye conditions and complications during surgery. All of the resutured grafts retained clarity. CONCLUSION: Traumatic wound dehiscence is a serious and not uncommon complication following penetrating keratoplasty. Despite severe trauma, graft transparency was achieved in all cases and there was no need for regrafting.     

Traumatic wound dehiscence following penetrating keratoplasty.

Four young male patients with keratoconus had traumatic dehiscence of the surgical wound after penetrating keratoplasty. Two were rendered aphakic by the trauma, and in one patient the lens was dislocated posteriorly. In each case the dehiscence was repaired by resuturing the original corneal graft. Despite marked corneal oedema in the immediate postoperative period all four grafts deturgesced and subsequently cleared. The follow-up has been a minimum of 23 months. We recommend therefore primary resuturing of traumatic wound dehiscence after keratoplasty, anterior vitrectomy if the lens dislodged, and prophylactic antibiotics postoperatively. The clearing of the initially oedematous grafts in each case illustrates the resilience of the corneal endothelium.     

Corneal endothelium in penetrating keratoplasty

Specular microscopy of endothelium after corneal transplantation has often shown a sharp reduction in its number density immediately after surgery and long-term cell loss during the next three to four years in addition to continuous morphologic changes. We examined flat preparations of the endothelium of three corneal buttons removed three weeks, eight weeks, and 11 months after penetrating keratoplasty and compared them to similar preparations from the corneal rims of the respective donors. We did not find significant morphologic changes, and direct endothelial cell counts disclosed an endothelial cell loss of 3.8% at three weeks, 2.6% at eight weeks, and 5.6% at 11 months after keratoplasty. We believe the lack of endothelial cell loss and absence of morphologic changes in these specimens are direct results of our surgical technique.     

Corneal lamellar flap retraction after LASIK following penetrating keratoplasty

PURPOSE: To describe a case of lamellar flap retraction after laser in situ keratomileusis (LASIK) to correct myopia and astigmatism after penetrating keratoplasty (PKP). METHODS: Eleven months after PKP, a 34-year-old man underwent uneventful LASIK. Preoperative manifest refraction was -5.50 + 4.00 x 55, giving a best-corrected visual acuity (BCVA) of 20/20. Three days after LASIK, the central cornea was clear with a 1- to 2-mm displacement and marked swelling of the inferior edge of the lamellar corneal flap, without central striae. The patient's uncorrected visual acuity (UCVA) was 20/60. The flap was repositioned, sutured with 6 10-0 nylon interrupted sutures, and covered with a bandage contact lens. RESULTS: Five months after the repair, the cornea was clear, UCVA was 20/400, and manifest refraction was -9.50 + 6.00 x 75, giving a BCVA of 20/60. Three years later, manifest refraction was - 9.00 + 4.00 x 70, giving a BCVA of 20/40+2. CONCLUSION: In LASIK surgery after PKP, there is a risk of flap edema leading to retraction of the transplant wound. It may therefore be advisable to wait at least 1-2 years after PKP before performing LASIK. Patients who have corneal transplants should also be warned that they might have unique risks in LASIK treatment that may result in the loss of vision.     

Traumatic wound dehiscence 14 years following penetrating keratoplasty

Penetrating keratoplasty eyes are at greater risk of laceration than intact corneas due to persistent wound weakness, even years after surgery. We report a case of traumatic wound dehiscence by fingertip injury 14 years following penetrating keratoplasty.     

Corneal wound healing following laser in situ keratomileusis (LASIK): a histopathological study in rabbits

AIMS: To investigate the histopathological changes of rabbit corneas after laser in situ keratomileusis (LASIK) and to evaluate the corneal wound healing process. METHODS: A LASIK was performed on white rabbit eyes. Postoperatively, rabbits were killed on days 1 and 7, and at 1, 3, and 9 months. RESULTS: Periodic acid Schiff (PAS) positive material and disorganised collagen fibre were seen along the interface of the corneal flap even 9 months after operation. CONCLUSIONS: The wound healing process still continued at 9 months after LASIK indicating that a much longer time than expected was required for corneal wound healing following LASIK.     

Corneal dynamics after single interrupted suture removal following penetrating keratoplasty.

PURPOSE: To evaluate corneal topographic changes after removal of a single interrupted suture in patients who underwent keratoplasty for keratoconus. METHODS: Fifteen interrupted sutures in 15 eyes after keratoplasty were removed to control astigmatism in a prospective clinical study. Videokeratography using an EyeSys Corneal Analysis System was performed before suture removal, and 1 hour, 1 day, 1 week, and 2 to 4 weeks after suture removal. Changes in dioptric power and axis of the steepest and flattest semimeridians were evaluated. RESULTS: The range of the dioptric change of the steepest semimeridian was from -0.43+/-0.34 D during the first hour to +0.70+/-0.39 D from 1 day to 1 week. The largest axis change of the steepest semimeridian (17.1 degrees+/-5.6 degrees, range 1 degree to 66 degrees ) occurred during the first hour (P = .006). The largest surgically induced vectorial change occurred during the first hour (16.10 @ 10.5 ), while relative stability of the steepest semimeridian was observed during the rest of the study period. Changes in power and axis of the flattest semimeridian were also demonstrated. A variety of topographic corneal patterns were demonstrated following suture removal, indicating unpredictable change of astigmatism. CONCLUSIONS: The steepest semimeridian of the central 3-mm zone showed maximal vectorial change 1 hour following suture removal. Reciprocal changes occurred at the same time in the flattest semimeridian. The response of the corneal surface to suture removal is unpredictable and complex.     

Corneal ulcer-infiltrate associated with soft contact lens use following penetrating keratoplasty

A review of 100 patients who underwent penetrating keratoplasty revealed 47 who required therapeutic soft contact lenses in the early postoperative period. Twelve corneal ulcer-infiltrates, 11 of which were culture positive, occurred during soft contact lens wear (23% incidence of this complication in contact lens fitted eyes). The most common offending organism was coagulase-negative staphylococcus. The only statistically significant risk factor for infection if a lens was used was the presence of a persistent epithelial defect (p = 0.03). Factors which could not be statistically correlated with corneal ulcer-infiltrate included keratoconjunctivitis sicca, the type of contact lens, the method of donor cornea preservation, lens hygiene, antibiotic and steroid usage, the presence of blepharitis, preoperative bacterial keratitis, and the history of a previously failed penetrating keratoplasty.     

Corneal endothelial cell damage in penetrating keratoplasty.

Fifty-eight corneal grafts were examined by specular microscopy to determine the corneal endothelial cell damage following penetrating keratoplasty. The average postoperative follow-up period was 10.1 months. The cell density decreased continuously during the observation period, and the endothelial cell loss of the central area of the cornea in all the cases averaged 10.4% at two weeks after the surgery, 16.0% at one month, 33.0% at three months, 39.4% at six months, and 48.2% at one year. However, the cell loss in the keratoconus group averaged -1.9, 1.2, 9.9, 30.6 and 33.4% for the corresponding postoperative periods. The cell loss in the bullous keratopathy eyes showed higher values compared to those in the keratoconus and the corneal leukoma eyes. It was concluded that cell loss in penetrating keratoplasty during the first postoperative year depends on the host diseases.     

Long-term follow-up of wound healing following epikeratophakia in rabbits

Epikeratophakia was performed on rabbit corneas using cryolathed keratolens and histological examinations were performed after long-term follow-up. On days 254 and 360 after the operation, pachymetry was performed, and corneas were excised, labeled with 3H-proline (10 muCi/ml) in DME for 4 hours, fixed by 2% glutaraldehyde and analyzed histologically using light and electron microscopy and by autoradiography. The results of pachometry revealed that postoperative increases of the corneal thickness on days 254 and 360 were both smaller than the expected value, 350 microns. However, on days 254 and 360, collagen fibril density (CFD) in the keratolens stroma to 95% and 99% of that of the control cornea (264 +/- 16/microns2). On day 254, activated keratocytes with well developed rough endoplasmic reticulum which were suggestive of active collagen production and keratocytes with extended pseudopoidia that suggested phagocytic activity were observed in the keratolens stroma. On day 360, most keratocytes in the keratolens stroma revealed a normal shape. In the epithelium over the keratolens, poor differentiation of basal cells and irregularity or lack of basement membrane were still observed. At both postoperative periods, the endothelium showed no remarkable morphologic abnormality on histological analysis under light and electron microscopy. These findings and the results of our previous study indicated that the reconstruction of the keratolens stroma continued for about one year postoperatively and complete healing after epikeratophakia including epithelial repair needs more than one year.