Corneal Copper Deposition Secondary to Monoclonal Gammopathy in a Patient With Chronic Lymphocytic Leukemia: A Case Report

Hypercupremia-induced corneal copper deposition secondary to monoclonal gammopathy is rare and shows a characteristic corneal opacity quite different from other causes of hypercupremia, such as Wilson's disease. This report describes a case of corneal copper deposition in a patient with monoclonal gammopathy associated with chronic lymphocytic leukemia. An 84-year-old man with slowly progressive corneal opacity was referred to our hospital. The corneal opacity was present at least five years ago. The patient's best-corrected visual acuity was 20/25 OU (in both eyes) at the initial visit to our hospital. Slit-lamp examination and anterior segment optical coherence tomography revealed bilateral brown-colored opacity localized to deep layers of the central cornea. In vivo confocal microscopy (IVCM) showed indistinct corneal stromal cells in the deep layer and endothelial cells. The possible differential diagnoses were corneal dystrophy and Wilson's disease, but the color, shape, or site of corneal opacity was inconsistent with the disease. As the patient had a history of chronic lymphocytic leukemia, which is often associated with monoclonal gammopathy, we suspected that the corneal opacity was copper deposition in association with the hematologic diseases. Laboratory examinations showed elevated serum copper and normal ceruloplasmin. Serum protein electrophoresis revealed significantly high IgG levels with depression of IgA, IgE, and IgM. These results supported our diagnosis. Followingly, we consulted the patient's attending hematologist, and the doctor initiated treatment for hypercupremia. In conclusion, hypercupremia secondary to monoclonal gammopathy should be considered a possible cause of central brown-colored corneal opacity.

Usefulness of smear microscopy for therapeutic decision-making in patients with infectious keratitis

PURPOSE

To determine the usefulness of smears in the diagnosis of infectious keratitis by comparing smears and 2 different culture methods.

STUDY DESIGN

Retrospective, observational study.

METHODS

The foci of 73 patients diagnosed with infectious keratitis at Hiroshima University Hospital between July 2011 and September 2015 were abraded, and smear microscopy and culturing were performed. The microorganism detection rates and other parameters were compared.

RESULTS

Microorganisms were detected in 47 of 73 specimens. Microorganisms were identified in 32 of 69 cases cultured on plain medium (detection rate, 46.4%) compared with 22 of 61 cases cultured on swab transport medium (detection rate, 36.1%). There was no significant difference in the microbial detection rate between the plain medium method and the swab transport medium method (P = 0.23). Smear microscopy and culture findings were concordant in 21 (28.8%) cases, and different microorganisms were detected in 9 cases. In 17 cases, the culture was negative, despite the presence of microorganisms on smear microscopy, and in 7 cases, the culture was positive, despite the absence of microorganisms on smear microscopy. The positivity rate of microbial detection was significantly higher when no antimicrobial agents had been administered previously (odds ratio 7.50, P = 0.017).

CONCLUSION

Smear microscopy of abrasions from lesions is useful for the initiation of treatment for infectious keratitis. However, culture studies should be conducted at the same time to confirm antimicrobial sensitivity. If possible, smear microscopy should be performed before the initiation of antimicrobial therapy.

Refractory Fungal Keratitis Caused by Acrophialophora fusispora: A Case Report and Literature Review

Acrophialophora fusispora is a filamentous fungus that is found in soil and rarely infects humans. We herein report the first case of fungal keratitis caused by A. fusispora in Japan and present a review of the literature on human infections with Acrophialophora species. A 62-year-old Japanese male on immunosuppressive therapy developed fungal keratitis after the removal of a corneal foreign body from his left eye. Voriconazole eye drops and systemic therapy for post-traumatic fungal keratitis did not resolve the infection, and the patient required a therapeutic corneal transplant. The isolate was identified as A. fusispora based on the nucleotide sequence of the internal transcribed spacer region. In a drug susceptibility test, the minimum inhibitory concentration of voriconazole was 0.5 μg/mL. Based on this case and previous cases from the literature review, fungal keratitis caused by A. fusispora is often refractory.

Matrix metalloproteinase and cytokine expression in Tenon fibroblasts during scar formation after glaucoma filtration or implant surgery in rats

Failure of surgery for glaucoma is usually due to post-surgical scarring (fibrosis), a process in which fibroblasts play a prominent role. We investigated the molecular mechanisms of such scarring by examining the expression of matrix metalloproteinases and cytokines in Tenon fibroblasts isolated from rats after glaucoma surgery. Filtration surgery was performed in one eye and implant surgery in the other; and Tenon fibroblasts were isolated from the tissue surrounding the bleb after surgery. The cells were cultured and examined for the expression of matrix metalloproteinases (MMPs) by reverse transcription-polymerase chain reaction, immunoblot and gelatin zymographic analyses. Culture supernatants were also assayed for cytokines with a multiplex array. The amounts of MMP-1 and MMP-3 mRNAs and proteins were greater in cells isolated after implant surgery than in those isolated after filtration surgery, with the progression of scar formation being more complete after the former surgery. The secretion of interleukin-6 (IL-6) by cells isolated after filtration surgery was greater than that for cells isolated after implant surgery. Depletion of IL-6 by RNA interference in cells isolated after filtration surgery increased the expression of MMP-1 and MMP-3 in these cells. These results thus suggest that the expression of MMP-1 and MMP-3 in Tenon fibroblasts is regulated by IL-6 during, and may play an important role in, scar formation after glaucoma surgery.

Differential contributions of impaired corneal sensitivity and reduced tear secretion to corneal epithelial disorders

BACKGROUND/AIMS

To determine the possible roles of impaired corneal sensitivity and reduced tear secretion in various types of corneal epithelial disorders.

METHODS

A total of 99 patients (179 eyes) with corneal epithelial disorders classified as persistent epithelial defects (PED), corneal erosion, or superficial punctate keratopathy (SPK) and 115 individuals (230 eyes) without apparent ocular surface disorders (controls) were enrolled in a prospective study. Corneal sensitivity was measured with a Cochet-Bonnet esthesiometer, and tear secretion was measured by the Schirmer test in each subject.

RESULTS

Corneal sensitivity of eyes in the PED and corneal erosion groups was significantly lower than that in the control group. Schirmer test values for eyes in the SPK group were significantly reduced compared with those in the control group.

CONCLUSION

A loss of corneal sensitivity may contribute to the development of PED and corneal erosion, whereas reduced tear secretion may be a contributing factor for SPK. Both results indicate the importance of corneal sensory innervation to the maintenance of corneal integrity.

Two cases of methicillin-resistant Staphylococcus aureus keratitis after Epi-LASIK

BACKGROUND

We describe two severe cases of methicillin-resistant Staphylococcus aureus (MRSA) keratitis following Epi-LASIK surgery.

CASES

One patient was a 23-year-old man who underwent Epi-LASIK surgery in both eyes. He developed an infectious corneal ulcer in one eye 2 days after surgery and was referred to us 7 days post-surgery with corneal perforation, for which we performed therapeutic penetrating keratoplasty. The other patient was a 32-year-old man who developed infectious keratitis in one eye 4 days after bilateral Epi-LASIK and was referred to us 2 days later.

OBSERVATIONS

Microbial testing revealed MRSA infection as the cause of the keratitis in both patients which was successfully treated with vancomycin eyedrops.

CONCLUSION

Infectious keratitis after refractive surgery is uncommon; it is important to diagnose this condition, identify the causative agent, and initiate treatment with appropriate antibiotics as soon as possible.

Localization of semaphorin 3A in the rat cornea

Semaphorin 3A (Sema3A) functions to guide the growth of neurons during development. We investigated the localization of Sema3A in the cornea, one of the most sensitive tissues in the body. Immunoblot analysis and reverse transcription-polymerase chain reaction analysis revealed that Sema3A protein and mRNA are expressed in the normal rat cornea. Immunofluorescence staining of frozen sections or tissue blocks prepared from the cornea revealed the presence of Sema3A in wing cells and basal cells (but not superficial cells) of the corneal epithelium, in keratocytes, and in the corneal endothelium. The expression pattern of Sema3A in the corneal epithelium differed from those of zonula occludens-1 and connexin43. These observations show that Sema3A is expressed in all cells of the rat cornea with the exception of superficial epithelial cells.

Abnormal retinal blood vessels in Ehlers-Danlos syndrome type VI

BACKGROUND

Ehlers-Danlos syndrome (EDS) is a hereditary connective tissue disorder caused by defective collagen synthesis and categorized into 11 types based on genetic mutations and clinical features.(1) Its principal clinical characteristics include hyperelasticity and vulnerability of the skin and joints to laxity, and fragility of blood vessels.

CASE

We recently performed vitreous surgery with introduction of an artificial cornea and corneal allograft transplantation in a boy with EDS type VI, whose visual acuity had decreased rapidly because of vitreous hemorrhage.

OBSERVATIONS

An ultrasound examination revealed posterior vitreous detachment with fresh vitreous hemorrhage. After vitrectomy with introduction of an artificial cornea and cornea allograft transplant were carried out, visual acuity improved to 0.05 and was maintained for at least 22 months.

CONCLUSIONS

Abnormal collagen synthesis is thought to lead to systemic disorders such as hyperelasticity, vulnerability to skin and joint laxity, and fragile blood vessels in patients with Ehlers-Danlos syndrome.

Delayed wound closure and phenotypic changes in corneal epithelium of the spontaneously diabetic Goto-Kakizaki rat

PURPOSE

To characterize wound closure and phenotypic changes in the corneal epithelium of the Goto-Kakizaki (GK) rat, a spontaneous model of type 2 diabetes.

METHODS

Corneal wound healing was monitored by fluorescein staining after epithelial debridement. Tear secretion was measured with the Schirmer test, and corneal sensation was evaluated with an esthesiometer in 13- to 15-week-old GK and Wistar (control) rats. The distributions of cytokeratin 12 (K12), K14, and connexin43 in the corneal epithelium were examined by immunohistofluorescence analysis. The proliferation capacity of epithelial cells in the intact cornea and during wound healing was evaluated by immunostaining for Ki-67.

RESULTS

Tear secretion, corneal sensation, and corneal epithelial wound closure rate were all decreased in GK rats compared with those in Wistar rats. Whereas connexin43, K14, and Ki-67 were all restricted to the single layer of basal cells in the corneal epithelium of Wistar rats, they were detected in the two layers of cells closest to the basement membrane in that of GK rats. The frequency of Ki-67-positive cells in the intact corneal epithelium was greater in GK rats than in Wistar rats, and it was increased to a greater extent in the peripheral cornea of GK rats than in that of Wistar rats during wound healing.

CONCLUSIONS

Spontaneously diabetic GK rats manifest characteristics similar to those of diabetic keratopathy in humans, including delayed wound closure, and they exhibit phenotypic changes in corneal epithelial cells.

Delayed corneal epithelial wound healing after penetrating keratoplasty in individuals with lattice corneal dystrophy

PURPOSE

To investigate whether corneal epithelial cells of individuals with lattice corneal dystrophy (LCD) possess an intrinsic defect.

DESIGN

Retrospective case-control study.

METHODS

The medical charts of nine individuals with LCD and those of 14 patients with keratoconus and 11 patients with corneal leukoma (controls), all of whom underwent penetrating keratoplasty (PKP) in one eye at Yamaguchi University Hospital between February 1998 and November 2001, were examined for the time for epithelial resurfacing after surgery.

RESULTS

The time required for resurfacing of the corneal epithelium after PKP was significantly greater in LCD patients (8.56 +/- 4.95 days, mean +/- SD) than in patients with either keratoconus (1.71 +/- 0.91 days, P = .006) or corneal leukoma (3.00 +/- 1.95 days, P = .03).

CONCLUSIONS

Corneal epithelial wound healing was delayed in LCD patients after PKP, suggesting that the keratoepithelin gene mutations responsible for this condition affect corneal epithelial cells.

Participation of p38 MAP kinase, but not p44/42 MAP kinase, in stimulation of corneal epithelial migration by substance P and IGF-1

PURPOSE

Substance P and insulin-like growth factor-1 (IGF-1) synergistically promote corneal epithelial migration both in vitro and in vivo. The mechanism of this action was investigated.

METHODS

The effects of various inhibitors and activators of intracellular signaling pathways on corneal epithelial migration were examined by measuring the length of the migration path in rabbit corneal blocks in culture.

RESULTS

Inhibitors of signaling by p38 or p44/42 isoforms of mitogen-activated protein (MAP) kinase or of phosphatidylinositol (PI) 3-kinase reduced the extent of spontaneous migration of the corneal epithelium, whereas modulators of signaling by cyclic AMP- or cyclic GMP-dependent protein kinases had no effect. The inhibitors of p38 MAP kinase and of PI 3-kinase also abolished the stimulatory effect of substance P and IGF-1 on epithelial migration, whereas inhibitors of signaling by p44/42 MAP kinase or modulators of cyclic nucleotide-dependent signaling did not.

CONCLUSIONS

These results suggest that various signal transduction systems participate in spontaneous corneal epithelial migration as well as in the combined effect of substance P and IGF-1 on this process. In particular, although both p38 and p44/42 isoforms of MAP kinase appear to regulate spontaneous corneal epithelial migration, the stimulatory effect of substance P and IGF-1 appears to be mediated by p38 MAP kinase but not by p44/42 MAP kinase.

Characterization of Tetracycline-Inducible BitransgenicKrt12rtTA/+/tet-O-LacZMice

PURPOSE

To prepare binary transgenic mouse lines that overexpress reporter genes in a corneal-epithelium-specific manner when induced by doxycycline.

METHODS

A gene-targeting construct containing an internal ribosomal entry site-reverse tetracycline transcription activator (IRES-rtTA) cassette was inserted into the Krt12 allele (keratin 12 gene) to produce a knock-in Krt12(rtTA/+) mouse line through gene-targeting techniques. The Krt12(rtTA/+) knock-in mice were bred with tet-O-LacZ reporter mice to obtain Krt12(rtTA/+)/tet-O-LacZ bitransgenic mice. The expression of the LacZ gene was induced in bitransgenic mice by administration of doxycycline in the drinking water and chow.

RESULTS

Administration of doxycycline induced a 15-fold increase of beta-galactosidase activity in the cornea of adult bitransgenic mice (Krt12(rtTA/+)/tet-O-lacZ). Administration of doxycycline either to single transgenic Krt12(rtTA/+) or tet-O-LacZ mice as a control did not induce overexpression of LacZ as it did in the bitransgenic mice. The induction of beta-galactosidase enzyme activity by doxycycline in bitransgenic mice took place in 24 hours and reached a plateau by 2 days. Histochemical analysis also showed that beta-galactosidase induction was limited to the corneal epithelium of bitransgenic mice fed doxycycline. The increased beta-galactosidase activity in corneal epithelium caused by doxycycline returned to basal levels in 4 weeks after the antibiotics were omitted from the diet.

CONCLUSIONS

A binary mouse model has been successfully established that conditionally overexpresses reporter genes in corneal epithelium. This mouse model will be useful in elucidating signaling pathways of various growth factors and cytokines and gene functions in the maintenance of homeostasis and pathogenesis in the adult mouse cornea.

Differential regulation of focal adhesion kinase and paxillin phosphorylation by the small GTP-binding protein Rho in human corneal epithelial cells

PURPOSE

Lysophosphatidic acid (LPA), which activates the small guanosine triphosphate (GTP)-binding protein Rho, was previously shown to promote migration of the rabbit corneal epithelium in culture. The signaling pathway responsible for this effect of LPA was examined in this study with a human corneal epithelial (HCE) cell line.

METHODS

The activation of Rho was detected with a pull-down assay. Tyrosine phosphorylation of paxillin and of focal adhesion kinase (FAK) were examined both by immunofluorescence staining and by immunoprecipitation and immunoblot analyses. Expression of integrins alpha5 and beta1 was evaluated by immunoblot analysis.

RESULTS

Incubation of cells with LPA (10 micro M) for 2 min resulted in marked activation of Rho, and this effect was blocked by pretreatment with the Rho inhibitor exoenzyme C3 (2 micro g/ml) for 24 h. Tyrosine phosphorylation of both paxillin and FAK was detected in HCE cells under basal conditions by immunofluorescence staining, immunoprecipitation, and immunoblot analyses. LPA induced a concentration- and time-dependent increase in the tyrosine phosphorylation of paxillin, which was maximal at a concentration of 10 micro M and a time of 2 min. Exoenzyme C3 inhibited LPA-induced paxillin phosphorylation. Neither LPA nor exoenzyme C3 affected tyrosine phosphorylation of FAK or expression of integrins alpha5 and beta1.

CONCLUSIONS

LPA induces Rho activation and the consequent tyrosine phosphorylation of paxillin in HCE cells, and these effects likely contribute to the promotion of corneal epithelial migration by this agent.

Enhancement by neutrophils of collagen degradation by corneal fibroblasts

Activated corneal fibroblasts and infiltrated leukocytes are thought to contribute to corneal ulceration. The potential roles of neutrophil-fibroblast and cell-matrix interactions in the degradation of stromal collagen associated with corneal ulceration have now been investigated with the use of three-dimensional cultures of rabbit cells in collagen gels. Degradation of collagen fibrils during culture was measured by spectrophotometric determination of released hydroxyproline. Whereas corneal fibroblasts alone degraded collagen fibrils to a small extent, neutrophils did not. However, the addition of neutrophils or neutrophil-conditioned medium (CM) to cultures of corneal fibroblasts resulted in a marked increase in the amount of collagen degraded by the fibroblasts. The effect of CM from neutrophils cultured in collagen gels on collagen degradation by corneal fibroblasts was greater than that of medium conditioned by neutrophils in monolayer culture. Immunoblot as well as reverse transcription and real-time polymerase chain reaction analyses revealed that neutrophil-CM stimulated the synthesis of matrix metalloproteinase (MMP)-1 and MMP-3 by corneal fibroblasts. The stimulatory effect of neutrophils on collagen degradation by corneal fibroblasts was inhibited by the synthetic MMP inhibitor ilomastat and by interleukin-1 (IL-1) receptor antagonist. These results suggest that factors secreted by collagen-stimulated neutrophils augment collagen degradation by corneal fibroblasts through a stimulatory effect on MMP synthesis and that IL-1 released by neutrophils may contribute to this effect.

Comparison of confocal biomicroscopy and noncontact specular microscopy for evaluation of the corneal endothelium

PURPOSE

To compare the clinical efficacy of confocal biomicroscopy with that of noncontact specular microscopy for the evaluation of the corneal endothelium.

METHODS

The corneal endothelium was examined in 14 normal subjects (28 eyes) and in 6 patients (11 eyes) with Fuchs corneal endothelial dystrophy using a noncontact specular microscope (SP-2000P, Topcon, Japan) and a confocal biomicroscope (ConfoScan, Tomey, Japan). The images and the calculated densities of corneal endothelial cells obtained by the 2 techniques were compared.

RESULTS

For normal subjects, the images of corneal endothelial cells obtained by the 2 techniques were almost identical, although the density of these cells determined by confocal biomicroscopy (2916 +/- 334 cells/mm2) was slightly higher than that determined by noncontact specular microscopy (2765 +/- 323 cells/mm2). In contrast, whereas clear images of corneal endothelial cells, allowing the determination of cell density, were obtained for all 11 eyes of the patient group by confocal biomicroscopy, clear images were obtained for only 4 of these 11 eyes (36.4%) by noncontact specular microscopy.

CONCLUSION

Both noncontact specular microscopy and confocal biomicroscopy revealed the shapes and number of endothelial cells in the normal cornea. However, for corneas with Fuchs dystrophy, clear images were obtained only by confocal biomicroscopy. Confocal biomicroscopy is thus an effective tool for evaluation of the diseased corneal endothelium.

Correlation of corneal sensation, but not of basal or reflex tear secretion, with the stage of diabetic retinopathy

PURPOSE

To examine the possible relation between corneal sensation or tear secretion and the stage of diabetic retinopathy in diabetic patients.

METHODS

Total reflex or basal tear secretion and corneal sensation were determined in 95 patients with type II diabetes mellitus and 58 nondiabetic control subjects. Tear secretion was measured by the Schirmer test and corneal sensation with a Cochet-Bonnet esthesiometer.

RESULTS

Corneal sensation and total or reflex tear secretion were significantly reduced in diabetic patients compared with nondiabetic controls. The loss of corneal sensation, but not that of tear secretion, was significantly correlated with stage of diabetic retinopathy in diabetic patients who were diagnosed with no diabetic retinopathy, simple diabetic retinopathy, preproliferative retinopathy, or proliferative retinopathy.

CONCLUSION

Both corneal sensation and total or reflex tear secretion are reduced in individuals with diabetes. The decrease in corneal sensation, but not that in each tear secretion, was correlated with the stage of diabetic retinopathy. Given that loss of corneal sensation is a manifestation of diabetic polyneuropathy, these results are consistent with the notion that both diabetic retinopathy and polyneuropathy result from a basement membrane abnormality.

Abnormal light scattering detected by confocal biomicroscopy at the corneal epithelial basement membrane of subjects with type II diabetes

AIMS/HYPOTHESIS

Abnormalities of the basement membrane are thought to contribute to the complications of diabetes. The suitability of the cornea for detecting such abnormalities was assessed by determining its light-scattering index, a quantitative measure of tissue reflectivity in the basement membrane zone, with a confocal biomicroscope.

METHODS

The light-scattering index was measured in 65 subjects with Type II (non-insulin-dependent) diabetes mellitus and 18 control subjects and was evaluated for its possible relation to the stage of diabetic retinopathy. Diabetic retinopathy was staged by ophthalmoscopic examination as non-diabetic (NDR), simple (SDR), preproliferative (PPDR), or proliferative (PDR).

RESULTS

Examination of the cornea layer-by-layer with a confocal biomicroscope did not show any marked differences in morphology between diabetic and control subjects. The LSI (mean +/- SD) was 0.81 +/- 0.13, 0.87 +/- 0.09, 0.90 +/- 0.09, 0.90 +/- 0.13, and 1.02 +/- 0.25 in control subjects and in diabetic subjects with NDR, SDR, PPDR, or PDR, respectively; the light-scattering index of diabetic subjects with PDR was significantly greater than that of the control subjects (p = 0.001). An LSI greater than 1.0 was detected in 5.6, 6.3, 15.0, 15.4, and 50.0% of control subjects and of patients with NDR, SDR, PPDR, or PDR, respectively; the percentage of subjects with an LSI greater than 1.0 was significantly increased in diabetic patients with PDR than for control subjects.

CONCLUSION/INTERPRETATION

These results suggest that the LSI increases with the stage of diabetic retinopathy, and that measurement of corneal light scattering could provide an index of basement membrane abnormality in people with diabetes.

Characterization of insulin-like growth factor-1 receptors in rabbit corneal epithelial cells

Substance P (SP) and insulin-like growth factor-1 (IGF-1) synergistically facilitate corneal epithelial wound healing in vitro and in vivo. This synergism is mediated through the NK-1 receptors for SP, and IGF-1 does not modulate the binding affinity of NK-1 receptors. To clarify the effect of SP on the binding characteristics of IGF-1 receptors, the binding affinity and number of binding sites for IGF-1 in rabbit corneal epithelial cells were studied using a binding assay for(125)I-IGF-1. The binding affinity and number of binding sites for IGF-1 were determined by Scatchard plot analysis. Cultured rabbit corneal epithelial cells bound specifically to IGF-1. For IGF-1 in corneal epithelial cells, the binding affinity was 4 n m and the number of binding sites was 1x10(5)binding sites cell(-1). Although IGF-2 and insulin also bind to IGF-1 receptors, their affinities were, respectively, eight- and 300-fold lower than that of IGF-1. IGF-1 and IGF-2 stimulated corneal epithelial migration in the presence of SP, but insulin did not. Pretreatment of the corneal epithelial cells with SP (2x10(-5)m) failed to change the binding affinity or number of binding sites for IGF-1. These results demonstrated that corneal epithelial cells possess specific receptors for IGF-1. The synergistic effect of SP and IGF-1 on corneal epithelial wound healing does not result from regulation at the receptor level.

Hyaluronan facilitates corneal epithelial wound healing in diabetic rats

We investigated the effect of hyaluronan on corneal epithelial wound healing in rats affected by diabetes. Furthermore, because hyaluronan is thought to affect corneal epithelial wound healing through the mechanism of binding of hyaluronan to provisional fibronectin in the wounded area, we compared the localization of fibronectin immunohistochemically during corneal epithelial wound healing in diabetic and non-diabetic rats. Streptozotocin was used to induce diabetes in half the rats. Two weeks after treatment, the whole corneal epithelium of diabetic and untreated rats was debrided. The rats were divided into groups (seven or eight rats per group), and hyaluronan eye drops at concentrations of 0.03, 0.1, or 0.3%, chondroitin sulfate (3%), or phosphate buffered saline (PBS) was given in eye drops 6 times a day for 4 days, starting immediately after debridement. The area of the corneal epithelial wound was measured immediately after debridement and at 12, 18, 24, 30, 48, 72, and 96 hours afterwards. Although the healing process was similar in non-diabetic and diabetic rats, the healing rate in diabetic rats was slower than that in normal controls. In both diabetic and non-diabetic rats, hyaluronan increased the healing rate in a dose-dependent manner; the difference was significant compared with the PBS-treated group, at hyaluronan doses of 0.1% and 0.3%. However, chondroitin sulfate did not affect corneal epithelial wound closure, regardless of whether the rats were diabetic or not; the healing rates were identical to those of PBS-treated diabetic and non-diabetic controls. In both diabetic and non-diabetic corneas, fibronectin was localized in the corneal subepithelial region, and in streaks between collagen fibers of the stroma. One day after debridement, a layer of fibronectin immunofluorescence was clearly visible on the surface of the denuded stroma. As healing progressed staining of fibronectin diminished at the interface between the new epithelium and the stroma. These changes in localization of fibronectin during corneal epithelial wound healing were similar in both diabetic and non-diabetic rats. Our results demonstrate that hyaluronan facilitates corneal epithelial wound healing in diabetic rats, and suggest that one possible mechanism of its stimulatory effect lies in its binding to a provisional fibronectin matrix, in both diabetic and non-diabetic rats.