Recombinant tissue plasminogen activator injected into the vitreous cavity may penetrate the retinal veins of a porcine model of vascular occlusion

AIM

To determine if recombinant tissue plasminogen activator (rtPA) injected into the vitreous cavity can penetrate the retinal vessels of porcine eyes with or without vascular occlusion.

METHODS

Eight eyes (group I) of four pigs underwent clamping of the optic nerve flush with the globe for 90 minutes. One hour after reperfusion, one eye of each pig was injected with 75 microg of rtPA, and the fellow eye was injected with balanced salt solution (BSS). Eyes were processed for immunohistochemistry. Four additional eyes (group II) of two pigs were subjected to the same injections, but without optic nerve clamping.

RESULTS

After reperfusion, the clinical picture was similar to that of a central retinal vein occlusion. Immunoperoxidase staining showed rtPA only in the retinal veins but not the retinal arteries in all eyes injected with rtPA in both groups I and II. Those eyes also showed intense rtPA staining at the level of the internal limiting membrane (ILM). No staining was seen at the level of the ILM or inside the retinal vessels in the BSS injected eyes. Immunofluorescence staining showed intense staining at the level of the ILM, but not inside the retinal vessels in the rtPA-injected eyes.

CONCLUSIONS

rtPA may penetrate the retinal veins, but not the arteries of porcine eyes with and without vascular occlusion. The ILM may play a part in preventing rtPA penetration.

Unexpected autopsy findings arising from postmortem ocular examination

BACKGROUND

A full autopsy at our institution includes removal of the eyes for pathologic examination. To our knowledge, the rate of ophthalmic findings at autopsy has not been documented previously.

DESIGN

We retrospectively reviewed 277 consecutive autopsies conducted between 1995 and 1999 in which the eyes were removed for examination. Ophthalmic findings were placed in the following categories: I, major findings included those that contributed to the patient's death, would have changed patient management, and/or may have important medical implications for close relatives; II, expected findings after ophthalmologic surgery and minor findings that may have eventually required treatment; and III, incidental findings.

RESULTS

Major findings (category I) were found in 32% of autopsies. Minor findings (category II) and incidental findings (category III) were documented in 62% and 34% of autopsies, respectively. Only 14% of autopsies revealed no ophthalmologic diagnoses.

CONCLUSION

In our series, postmortem ocular examination revealed a number of important findings, including several heritable and rare conditions. Eighty-six percent of autopsies disclosed at least one pathologic ophthalmologic finding, approximately one third of which demonstrated findings significant enough to have likely required management. Diabetic retinopathy was the most frequent major finding. Malignant melanoma of the choroid was the most commonly found intraocular neoplasm. Chronic uveitis was the most common minor finding. We conclude that important, often unexpected ophthalmic findings are frequently encountered at autopsy, underscoring the relevance of routine postmortem examination of the eyes.

Preoperative mobilization of circulating dendritic cells by Flt3 ligand administration to patients with metastatic colon cancer

PURPOSE

To evaluate preoperative dendritic cell (DC) mobilization and tumor infiltration after administration of Flt3 ligand (Flt3L) to patients with metastatic colon cancer.

PATIENTS AND METHODS

Twelve patients with colon cancer metastatic to the liver or lung received Flt3L (20 microg/kg/d subcutaneously for 14 days for one to three cycles at monthly intervals) before attempted metastasectomy. The number and phenotype of DCs mobilized into peripheral-blood mononuclear cells (PBMCs) were evaluated by flow cytometry. After surgical resection, metastatic tumor tissue was evaluated for DC infiltration. In vivo immune responses to recall antigens were measured.

RESULTS

After Flt3L administration, on average, the total number of leukocytes in the peripheral blood increased from 5.9 +/- 1.0 x 10(3)/mm(3) to 11.2 +/- 3.8 x 10(3)/mm(3) (mean +/- SD, P: =. 0001). The percentage of CD11c(+)CD14(-) DCs in PBMCs increased from 2.4% +/- 1.8% to 8.8% +/- 4.7% (P: =.004). Delayed-type hypersensitivity (DTH) responses to recall antigens (CANDIDA:, mumps, and tetanus) showed marginally significant increases in reactivity after Flt3L administration (P: =.06, P: =.03, and P: =.08, respectively). An increase in the number of DCs was observed at the periphery of the tumors of patients who received Flt3L compared with those of patients who had not.

CONCLUSION

Flt3L is capable of mobilizing DCs into the peripheral blood of patients with metastatic colon cancer and may be associated with increases in DC infiltration in the peritumoral regions. Flt3L mobilization is associated with a trend toward increased DTH responses to recall antigens in vivo. The use of Flt3L to increase circulating DCs for cancer immunotherapy should be considered.

8(S)-hydroxyeicosatetraenoic acid is the lipoxygenase metabolite of arachidonic acid that regulates epithelial cell migration in the rat cornea

BACKGROUND

We previously found that the inhibition of lipoxygenases resulted in delayed epithelial wound closure in organ-cultured rat corneas. The present study was undertaken to determine the lipoxygenase enzyme and metabolite(s) responsible for regulating reepithelialization and their mechanism of action.

METHODS

The effects of esculetin--an established lipoxygenase inhibitor--on endogenous hydroxyeicosatetraenoic acids (HETEs) production, epithelial wound closure, filamentous-actin (F-actin) cytoskeleton, and mitotic rate were investigated using a cell-culture assay and an organ-culture assay of rat corneal epithelium.

RESULTS

Lipoxygenase inhibition by esculetin, which resulted in the disruption of F-actin organization and a decrease in the mitotic rate, delayed wound closure in both cell- and organ-culture assays. Normal corneoscleral rims metabolized [3H]arachidonic acid to 12-HETE (major metabolite), 8-HETE, and 9-HETE. HETE synthesis was inhibited by esculetin in a dose-dependent fashion. Chiral-phase analysis revealed that they contained only (S)-enantiomers, which indicated that they were lipoxygenase metabolites. The inhibitory effects of esculetin on F-actin organization and epithelial wound closure in an organ-culture assay were totally reversed by exogenously added 8(S)-HETE, whereas 12- and 9-HETE had no effect. However, none of the HETEs reversed the decreased mitotic rate or achieved complete wound closure in the cell-culture assay.

CONCLUSIONS

These results suggest that 8(S)-HETE is the key metabolite of arachidonic acid that regulates corneal epithelial cell migration during wound healing. The metabolite responsible for cell proliferation remains to be determined.

Etomoxir-induced PPARalpha-modulated enzymes protect during acute renal failure

Regulation of fatty acid beta-oxidation (FAO) represents an important mechanism for a sustained balance of energy production/utilization in kidney tissue. To examine the role of stimulated FAO during ischemia, Etomoxir (Eto), clofibrate, and WY-14,643 compounds were given 5 days prior to the induction of ischemia/reperfusion (I/R) injury. Compared with rats administered vehicle, Eto-, clofibrate-, and WY-treated rats had lower blood urea nitrogen and serum creatinines following I/R injury. Histological analysis confirmed a significant amelioration of acute tubular necrosis. I/R injury led to a threefold reduction of mRNA and protein levels of acyl CoA oxidase (AOX) and cytochrome P4A1, as well as twofold inhibition of their enzymatic activities. Eto treatment prevented the reduction of mRNA and protein levels and the inhibition of the enzymatic activities of these two peroxisome proliferator-activated receptor-alpha (PPARalpha) target genes during I/R injury. PPARalpha null mice subjected to I/R injury demonstrated significantly enhanced cortical necrosis and worse kidney function compared with wild-type controls. These results suggest that upregulation of PPARalpha-modulated FAO genes has an important role in the observed cytoprotection during I/R injury.

A comparative study of bovine pericardium (periguard) and homologous sclera as lower eyelid spacer graft analogs in New Zealand white rabbits

PURPOSE

To compare bovine pericardium (Periguard; Bio-Vascular, Inc., St. Paul, MN, U.S.A.) and homologous sclera as spacer graft analogs in a rabbit model.

METHODS

A nonrandomized experimental animal study was conducted. Elliptical subconjunctival implants were placed in one lower eyelid each of 10 rabbits. Five rabbits received homologous sclera implants, and five received bovine pericardium implants. The rabbits were killed 7 weeks later, and the lower eyelids were examined clinically and histopathologically.

RESULTS

Rabbit eyelids implanted with Periguard had a more marked inflammatory reaction and more significant collagen lamellar disruption than eyelids implanted with homologous sclera, although clinically they appeared quite similar.

CONCLUSIONS

Although bovine pericardium elicited a more intense inflammatory response at the histopathologic level, both implants were similarly tolerated at the clinical level. These findings are consistent with animal and human investigations of bovine pericardium in other parts of the body, and warrant further studies into its potential use in the human eyelid.

The influence of hyperbaric oxygen therapy and irradiation on hydroxyapatite ocular implant exposure and fibrovascular ingrowth in New Zealand white rabbits

PURPOSE

Lack of adequate fibrovascular ingrowth has been implicated as a cause of exposure of hydroxyapatite (HA) implants in anophthalmic sockets. We investigated the vasculopathic effects of external beam irradiation, and the fibrovascular-enhancement effects of hyperbaric oxygen (HBO), on HA implant exposure and fibrovascular ingrowth in a rabbit model.

METHODS

Eighteen rabbits underwent enucleation with implantation of a 12-mm HA sphere. Six rabbits received 20 Gy of external beam orbital irradiation prior to enucleation. Three irradiated and 6 nonirradiated rabbits received postoperative HBO. Three weeks postoperatively, all rabbits were evaluated clinically for evidence of implant exposure. Implants were then removed, and histopathologic analysis of fibrovascular ingrowth was performed.

RESULTS

The amount of vascularization as measured by the depth of ingrowth was greater for nonirradiated (89% ingrowth) than for irradiated (71% ingrowth) animals. HA implant exposure occurred in 1 of 12 (8%) of the nonirradiated, and 4 of 6 (67%) of the irradiated rabbit orbits. HBO did not protect irradiated rabbits from exposure, but did enhance fibrovascular ingrowth in nonirradiated rabbits (100% ingrowth vs. 77% ingrowth).

CONCLUSION

Impaired orbital vascularization from prior irradiation appears to retard fibrovascular ingrowth into HA implants, and is associated with an increased incidence of exposure. While HBO did not diminish the likelihood of exposure in irradiated sockets, HA fibrovascular ingrowth in normal orbits appeared to increase with HBO. This may have beneficial clinical application in cases of exposure in nonirradiated orbits.

Bovine pericardium versus homologous sclera as wrapping materials for hydroxyapatite ocular implants: an animal study

PURPOSE

We compared bovine pericardium and homologous sclera as wrapping materials for hydroxyapatite (HA) ocular implants in enucleated New Zealand white rabbits.

METHODS

Eighteen rabbits were unilaterally enucleated and the sockets implanted with 10-mm HA spherical implants. Six implants were wrapped with homologous sclera, 6 with bovine pericardium, and 6 were not wrapped. The rabbits were killed 7 weeks later and the sockets were examined clinically for inflammation and implant exposure. Exenterated specimens were assessed histopathologically for inflammation and vascularization.

RESULTS

No clinical evidence of implant exposure or extrusion was detected in rabbits receiving sclera or bovine pericardium wrapped implants. Histopathologically, the bovine pericardium displayed more inflammation in its outer portion, as well as more disruption of its lamellar arrangement than did the sclera. Fibrovascular in-growth was complete in all wrapped implants.

CONCLUSION

Bovine pericardium behaves similar clinically to homologous sclera as a wrapping material for spherical HA ocular implants in a rabbit model, and may represent a reasonable alternative to sclera in such procedures in humans.

Clinicopathologic features and surgical management of dissecting glaucoma filtering blebs

Three patients are described in whom full-thickness glaucoma filtering procedures were complicated by marked extension of the bleb over the cornea, with subsequent symptoms that required surgical intervention. The surgical management in each case involved blunt dissection of the bleb from the cornea, with revision of the remaining portion of the bleb differing in each case according to the intraoperative findings. Light microscopic examination of one surgical specimen revealed a markedly attenuated epithelium covering hydropic corneal stroma. The authors postulate that the mechanism of formation involves aqueous humor dissection between corneal epithelium and stroma, leading to abnormal hydration of the superficial lamellae.

Cytomegalovirus keratitis after penetrating keratoplasty

We report the development of cytomegalovirus (CMV) keratitis in the penetrating keratoplasty of a 59-year-old human immunodeficiency virus-negative woman after uncomplicated corneal transplantation. Immunosuppression with topical cyclosporine A 2% in corn oil and topical prednisolone acetate 1% suspension was used postoperatively. The 15-month postoperative course was complicated by multiple episodes of endothelial rejection, medically controlled elevated intraocular pressure, polymicrobial bacterial (coagulase-negative staphlococcus and alpha-hemolytic streptococcus) keratitis, and endothelial plaque formation with associated hypopyon and epithelial defect. The graft failed and penetrating keratoplasty was repeated. Cytomegalovirus infection of superficial keratocytes in a region of scarring was identified in histological sections stained with hematoxylin and eosin and confirmed using mouse monoclonal anti-cytomegalovirus antibodies. Excision of the diseased corneal button with no additional treatment appears to have been curative. Low-grade keratitis was the only manifestation of the CMV infection, and it has not recurred 6 months postoperatively.

Coordinated activation of corneal wound response genes in vivo as observed by in situ hybridization

We used subtractive screening of a cDNA library prepared from corneoscleral rims after cauterizing rat corneas. We identified 76 clones whose corresponding mRNA increased during the wound healing process in an in vivo model of injury which damages the corneal epithelium, stroma, and endothelium. Of these clones, 31 sequences encode known proteins. Another 45 clones are novel sequences based on comparison with the GenBank/EMBL databases. Changes in the level of expression of the novel genes, and a selected number of the known genes, were examined by in situ hybridization 22 and 72 hr after corneal injury. The majority produced a 'wound pattern' of expression such that the mRNAs were highly induced in all cell types adjacent to the wound site at 22 hr post injury. This signal decreased in intensity with distance from the wound site. In a subset of corneoslceral rims examined by in situ hybridization, the mRNAs for these genes were also highly induced in the limbal epithelium, where the progenitor corneal epithelial stem cells reside. By 72 hr, when acute tissue damage had been repaired, the induced mRNA was only faintly present in the thickened epithelium. Our results provide a useful framework for further studies defining the pathophysiological roles of the known and novel proteins encoded by the isolated cDNA clones.

Removal of optic disc stalks during diabetic vitrectomy

BACKGROUND

The morphologic features and clinical consequences of removing residual optic disc stalks during vitrectomy for complications of diabetic retinopathy have not been described.

METHODS

Twenty-four residual optic disc stalks that were surgically removed from eyes with proliferative diabetic retinopathy and dense nonclearing vitreous hemorrhage and/or traction retinal detachment were studied histologically using conventional hematoxylin and eosin staining as well as a modified Glees staining technique.

RESULTS

Histologic examination demonstrated that 79% of the specimens consisted of vascularized glial tissue with an infiltrate of mononuclear cells and 21% consisted of glial membranes devoid of vasculature. Axons were identified in 33% of all tissues studied. Intra-operative hemorrhage occurred in three eyes with strongly adherent optic disc stalks and was controlled with transient elevation of the intraocular pressure. The presence of axons in the removed optic disc stalks was not correlated with a decreased final postoperative visual acuity (median time to follow-up 21 months).

CONCLUSIONS

Residual optic disc stalks removed during vitrectomy for proliferative diabetic retinopathy frequently contained axons. The presence of axons does not portend an unfavorable postoperative visual outcome.

Pyogenic granuloma of the cornea induced by "snake oil"

A pyogenic granuloma of the cornea developed on the vascularized cornea of a 79-year-old woman after "snake oil" accidentally dripped in her eye. The snake oil was being used to relieve forehead pain, which may have been referred. The five previously reported examples of corneal pyogenic granuloma are similar to this case in that trauma preceded development of the lesion. However, the chemical trauma induced by the snake oil appears to be a unique mechanism of injury.

The effect of angiostatic steroids and beta-cyclodextrin tetradecasulfate on corneal neovascularization in the rat

Folkman and coworkers have described angiostatic steroids that markedly inhibit neovascularization of the rabbit cornea when given topically with beta-cyclodextrin tetradecasulfate (beta-CD), yet have minimal or no glucocorticoid or mineralocorticoid activity. Our objective was to extend these observations to another species, the rat. We induced neovascularization by cauterizing rat corneas with silver nitrate/potassium nitrate; drugs were applied topically four times per day for 4 days in most experiments. Submicron sized emulsions of lipid-soluble dexamethasone and the angiostatic steroids 17 alpha-hydroxyprogesterone (1 or 10 mg ml-1) and cortexolone (1 or 10 mg ml-1) were prepared by lecithin encapsulation of drug microcrystals. The vehicle for water-soluble hydrocortisone 21-phosphate (HCP) +/- beta-CD (Molecusol; Pharmatec, Inc) was 10% Tween 20 in Tris-buffered 0.9% saline. Angiogenesis was significantly inhibited only by 1 mg ml-1 dexamethasone (-63.2% when compared with controls), 0.5 mg ml-1 HCP + 1 mg ml-1 beta-CD (-33.4%), and 1 mg ml-1 HCP (-40.2%). HCP (0.5 mg ml-1) or beta-CD (1 or 2 mg ml-1) alone had no significant effect on neovascularization; the inhibition by 1.0 mg ml-1 HCP was not potentiated by 2 mg ml-1 beta-CD. We also tested HCP and tetrahydro-S (TH-S) using 1.5% hydroxypropyl methylcellulose vehicle and beta-CD from Takeda Chemical Industries, Ltd., to simulate the procedure of Folkman and coworkers.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of inhibitors of arachidonic acid metabolism on corneal reepithelialization in the rat

We examined the ability of inhibitors of arachidonic acid metabolism to influence the rate of healing of organ-cultured rat corneas with 3-mm diameter central epithelial abrasions. In control corneas, and in the presence of the cyclooxygenase inhibitors indomethacin (1 microM), or flurbiprofen (1 microM), the defect was completely reepithelialized by 25 hr. In contrast, corneas cultured with the lipoxygenase inhibitors quercetin (100 microM), esculetin (100 microM), or baicalein (10 microM) or the dual cyclooxygenase/lipoxygenase inhibitors BW 775C (100 microM) or BW A540C (100 microM) had significantly delayed epithelial healing rates when compared with the controls; complete healing of the epithelial defects required 32.5-40 hr. Dose-response studies with esculetin and BW 755C demonstrated that the concentrations for 50% inhibition of reepithelialization (65.3 microM for esculetin, 39.6 microM for BW 755 C) were significantly greater than those for inhibition of 12-lipoxygenase activity (16.6 microM for esculetin, 21.1 microM for BW 755C), the major lipoxygenase activity in normal rat cornea. Addition of 12(S)-5,8,10,14- hydroxyeicosatetraenoic acid [12(S)-HETE, 0.01-10 microM], the main 12-lipoxygenase metabolite of arachidonic acid in normal rat cornea, to the organ cultures did not influence the rate of epithelial wound healing in the absence of presence of 100 microM esculetin. Our results suggest that lipoxygenase activity is an important factor in regulating corneal epithelial wound healing in the rat, presumably by influencing epithelial cell migration. The lipoxygenase enzyme and metabolite(s) responsible for regulating reepithelialization, and the mechanism of action, remain to be determined.

Calcific phacolysis

BACKGROUND AND METHODS

The authors report the clinical and ocular histopathologic findings in three patients with longstanding unilateral post-traumatic blindness. After one or more decades, acute pain associated with conjunctival hyperemia and apparent keratoprecipitates or a hypopyon developed in the affected eye of each individual. Phacoanaphylaxis was diagnosed preoperatively in two patients.

RESULTS

Calcified granular lens fragments were dispersed throughout all three eyes. The anterior chamber in all patients contained extracellular calcified lens particles, but only one eye contained conspicuous macrophages. Two eyes showed elevated intraocular pressure (IOP), and in one patient calcified particles extended into a glaucomatous optic nerve head.

CONCLUSION

To the authors' knowledge, this is the first report describing a rare condition involving the intraocular dispersal of calcified lens particles after disruption of the lens capsule. The authors have designated this entity as calcific phacolysis.

Effect of protein kinase C inhibitors and activators on corneal re-epithelialization in the rat

PURPOSE

To examine the ability of protein kinase C (PKC) inhibitors and activators to influence the rate of corneal re-epithelialization in the rat.

METHOD

Rat corneas with 3 mm diameter central epithelial abrasions were organ-cultured in control medium or in medium with inhibitors or activators of PKC.

RESULTS

In control corneas, the defect was completely re-epithelialized by 25 hr. In the presence of the PKC inhibitors staurosporine (100 nM), sphinganine (50 mumol/l), or H-7 (100 mumol/l) there were significantly larger epithelial defects than in controls after 5-25 hr of incubation. Re-epithelialization rates were similar to control corneas when the incubation medium contained HA1004 (100 mumol/l), an analogue of H-7 that is a potent inhibitor of cyclic adenosine monophosphate- and cyclic guanosine monophosphate-dependent protein kinases and a weak inhibitor of PKC. Two PKC activators, 1-oleoyl-2-acetyl-sn-glycerol (OAG) and phorbol 12-myristate 13-acetate (PMA), were unable to enhance the rate of epithelial wound healing.

CONCLUSIONS

Our results suggest that PKC activity is an important factor in regulating corneal epithelial wound healing, presumably by influencing cell migration. Moreover, the results with OAG and PMA suggest that PKC is maximally activated during re-epithelialization in this organ-culture assay.

Histopathological variation in keratoconus

During examination of 131 penetrating keratoplasty specimens from patients with keratoconus obtained in an 11-year period, we observed two histopathologic variants based on the appearance of Bowman's layer and the corneal epithelium. "Typical" keratoconus specimens had multiple breaks in Bowman's layer and central epithelial thinning, whereas "atypical" corneas lacked breaks in Bowman's layer and had less thinning of the central epithelium. Ninety-five corneas were from patients who underwent grafting in only one eye. Seventy-six (80%) of these corneas were "typical" and 19 corneas (20%) were "atypical" in appearance. Both variants had similar degrees of central stromal thinning. Patients with "typical" and "atypical" corneas differed demographically by race only; 49% of "typical" and 95% of "atypical" corneas were from white individuals. Thirty-six corneas were from 18 patients who underwent bilateral penetrating keratoplasty. The histologic appearance of these corneal pairs was concordant in 13 patients and discordant (one "typical" and one "atypical" cornea) in five patients. Statistical analysis indicated that this distribution is not significantly different from that predicted by chance and suggests that "typical" and "atypical" corneas are manifestations of the same disease process.

Corneal argyrosis associated with silver soldering

We report a patient who developed corneal argyrosis secondary to occupational silver soldering. Clinically, the cornea was notable for a green-brown discoloration localized to Descemet's membrane by slit-lamp biomicroscopy. Silver particles were identified within the anterior three eighths of Descemet's membrane by light and electron microscopy and energy-dispersive x-ray microanalysis. To our knowledge, the association between corneal argyrosis and silver soldering has not been previously reported.

Cat keratoplasty wound healing and corneal astigmatism

BACKGROUND

A major contributor to postkeratoplasty astigmatism may be donor/recipient disparity. Deficient or excess cornea at the wound is thought to influence the directions of the steep and flat meridians. Using an established model of penetrating keratoplasty in the cat, this study evaluated the morphometry of histopathologic wound features in the steep and flat meridians.

METHODS

Thirteen cats had successful penetrating keratoplasties after intentionally misshapen donor corneas were misaligned in misshapen recipient beds. At 9.50 +/- 0.32 (mean +/- 1 SEM) months after keratoplasty, photokeratography was performed and analyzed, corneas were sectioned along the steep and flat meridians, and four histologic sections were processed. Features of the wounds were measured using a Zeiss Videoplan. The relationships between the morphometry of each feature and every other feature, between the morphometry of each feature and eccentricity, and between the steep and flat section morphometry of each feature were statistically evaluated.

RESULTS

Epithelial thickness, area of lamellar alteration, length of Descemet's membrane produced postoperatively, and the depth that preoperative Descemet's membrane was embedded in the stroma were correlated with eccentricity (corneal astigmatism). Stromal thickness and the presence or absence of folded and fragmented Descemet's membrane were not correlated with eccentricity. Wound morphometry at the steep meridians was neither correlated with nor significantly different from wound morphometry at the flat meridians.

CONCLUSIONS

Differences between healing at the steep and flat meridians were not likely contributors to astigmatism. Disproportionate availability of tissue in wound regions may have affected healing throughout the entire wound over time. The absence of Bowman's layer in cats restricts application of our results to understanding the etiology of corneal astigmatism after penetrating keratoplasty in humans.

The effect of total-body irradiation on corneal neovascularization in the Fischer 344 rat after chemical cauterization

Previous investigations of corneal neovascularization after irradiation yielded discordant results. Most studies indicated that new blood vessel formation in the cornea is inhibited by irradiation. However, others reported that angiogenesis after corneal cauterization is similar in both irradiated and nonirradiated animals. To assess the effect of total-body irradiation on neovascularization further, the amount of angiogenesis was determined in irradiated rats after chemically induced corneal injury. Corneal tissue was evaluated quantitatively with computerized image analysis 2, 3, or 4 days postcautery in rats perfused with India ink and gelatin immediately after death. The rats were exposed to a single dose (9 Gy) of total-body irradiation 6 days before corneal cauterization. In both the nonirradiated and irradiated rats, neovascularization increased with the duration of the postcautery interval. The amount of corneal neovascularization was not significantly different in the irradiated and nonirradiated rats at any of the postcautery intervals studied. This investigation suggests that endothelial cell migration plays a more important role than cell replication in the pathogenesis of corneal angiogenesis in the Fischer 344 rat. Moreover, the suppression of corneal angiogenesis by irradiation may be dependent on the experimental conditions and species examined.