Vitreous and retinal amino acid concentrations in experimental central retinal artery occlusion in the primate.

PURPOSE: Vitreous and retinal amino-acid concentrations were evaluated in a primate model of central retinal artery occlusion (CRAO) to study the role of glutamate excitotoxicity in acute retinal ischaemia. METHODS: Unilateral, acute CRAO was produced by temporary clamping of the central retinal artery for 190 min in four elderly rhesus monkeys. Fundus photography, fluorescein angiography, and electroretinogram were performed before and during CRAO, and after unclamping the artery. Vitreous samples were obtained before and after CRAO in both eyes, and analysed for 13 amino-acid concentrations using high-pressure liquid chromatography. The animals were killed 350 min after retinal reperfusion, and the retinal tissue was submitted for amino-acid analysis. RESULTS: In all four eyes, the macula showed the 'cherry red spot'. The CRAO was confirmed by fluorescein angiography and decreased b-wave on electroretinogram. Retinal histology confirmed ischaemic changes in the inner retina. Changes in all 13 vitreous amino-acid concentrations after CRAO (including glutamate) were not significantly different between study and control eyes (P = 0.09 to 0.82). All retinal amino-acid concentrations (including glutamate) were not significantly different between two eyes (P = 0.07-0.93). CONCLUSIONS: In the primate model of acute inner retinal ischaemia induced by transient CRAO, we were unable to detect significantly elevated concentrations of vitreous and retinal glutamate. Our primate model has the advantage of closely modelling the CRAO in humans. Further basic and clinical studies are needed to elucidate the role of glutamate excitotoxicity in retinal ischaemia.

Traumatic macular hole: observations, pathogenesis, and results of vitrectomy surgery.

PURPOSE: To review our experience with vitrectomy surgery techniques for the treatment of traumatic macular holes and the biomicroscopic and surgical findings. DESIGN: Retrospective noncomparative, multicenter, case series. PARTICIPANTS AND INTERVENTION: Twenty-five patients with traumatic macular hole underwent surgical repair. INTERVENTION: Vitrectomy with membrane peeling and gas injection followed by prone positioning for 7 to 14 days. MAIN OUTCOME MEASURES: Postoperative evaluation included visual acuity testing, closure of the macular hole, and ocular complications. RESULTS: The macular hole was successfully closed in 24 of 25 cases (96%). The visual acuity improved two or more lines in 21 (84%) cases, and 16 (64%) achieved 20/50 or better vision. CONCLUSIONS: Vitrectomy surgery can successfully close macular holes associated with trauma and improve vision.

Microcirculation patterns other than loops and networks in choroidal and ciliary body melanomas.

PURPOSE: To provide ophthalmologists and pathologists with expanded criteria for separating patients at high risk of metastatic melanoma from those at low risk on the basis of microcirculation patterns in choroidal and ciliary body melanomas. DESIGN: Tissue culture studies and observational case series. PARTICIPANTS: The pattern-forming ability of four uveal melanoma cell lines of varying degrees of aggressive behavior was studied in vitro. Histologic sections of 234 eyes removed for choroidal or ciliary body melanoma were studied for the presence of microcirculation patterns. METHODS: The study was divided into two phases: the study of histologic sections of eyes removed for choroidal and ciliary body melanomas and observations on the in vitro behavior of cultured melanoma cells of varying degrees of invasive behavior. The presence or absence of each of nine microcirculation patterns was recorded from tissue sections, and interrelationships between different patterns were explored statistically. In vitro reconstitution of patterns and a study of the interrelationships of patterns in histologic sections was carried out. In the in vitro studies, uveal melanoma cell lines of varying degrees of aggressive potential were cultured to observe the development of architectural patterns other than loops and networks. MAIN OUTCOME MEASURES: In histologic studies, the outcome measure was the conditional probability of detecting loops or networks given the presence or absence of other patterns positive for periodic acid-SCHIFF: For tissue culture studies, the outcome measure was either the development or lack of development of patterns of different shapes in vitro. RESULTS: Histologic studies disclosed that given the presence of arcs without or with branching in a tissue section, it is likely that loops or networks will be detected in the same section plane, suggesting that the production of these patterns by aggressive tumor cells reflects a spectrum of architectural potential. In vitro studies confirmed this hypothesis by revealing that highly aggressive and metastatic uveal melanoma cell lines, but not poorly aggressive tumor cell lines, generated parallel channels with and without crosslinking and arcs with and without branching as well as loops and networks. CONCLUSIONS: The criteria for separating patients into low- and high-risk categories for metastasis from uveal melanoma should be expanded to include patterns other than loops or networks. In both the pathology laboratory as well as in a clinical setting, the detection of arcs or arcs with branching and parallel channels should prompt a careful search for loops and networks and for crosslinking parallel channels, respectively.

Collaborative ocular melanoma study (COMS) randomized trial of I-125 brachytherapy for medium choroidal melanoma. I. Visual acuity after 3 years COMS report no. 16.

OBJECTIVE: To report visual acuity during the first three years after iodine 125 (I(125)) brachytherapy for medium-sized choroidal melanoma and to identify important baseline and treatment factors associated with posttreatment visual acuity in a group of patients who were treated and observed prospectively as part of a large, randomized clinical trial. DESIGN: Observational case series within a randomized, multicenter study. PARTICIPANTS: Patients enrolled in the Collaborative Ocular Melanoma Study randomized trial of I(125) brachytherapy versus enucleation had choroidal melanoma of at least 2.5 mm but no more than 10.0 mm in apical height, and no more than 16.0 mm in largest basal dimension. One thousand three hundred seventeen patients enrolled from February 1987 through July 1998; 657 patients were assigned to I(125) brachytherapy. Visual acuity data for 623 patients who received I(125) brachytherapy as randomly assigned and who have been observed for at least 1 year were analyzed for this report. METHODS: Under study protocol, an ophthalmic evaluation, including best-corrected visual acuity measurement of each eye, was performed at baseline, every 6 months thereafter for 5 years, and once yearly thereafter. Two poor vision outcomes, visual acuity of 20/200 or worse that was confirmed at the next follow-up examination and loss of six lines or more of visual acuity from baseline that was confirmed at the next follow-up examination, were analyzed to identify baseline and treatment characteristics that were associated with posttreatment visual acuity. RESULTS: At baseline, median visual acuity in the eye with choroidal melanoma was 20/32, with 70% of eyes having 20/40 or better and 10% of eyes having 20/200 or worse visual acuity. Three years after I(125) brachytherapy, median visual acuity was 20/125, with 34% having 20/40 or better and 45% having 20/200 or worse visual acuity, including eyes that were enucleated within 3 years of treatment. Life-table estimates of percentages of patients who lost six or more lines of visual acuity from baseline, a quadrupling of the minimum angle of resolution, with this finding confirmed at the next 6-month follow-up examination, were 18% by 1 year, 34% by 2 years, and 49% by 3 years after treatment. Life-table estimates of percentages of patients with baseline visual acuity better than 20/200 whose visual acuity decreased to 20/200 or worse, confirmed at the next follow-up examination, were 17% by 1 year, 33% by 2 years, and 43% by 3 years after treatment. As soon as a poor vision outcome was observed, improvement of visual acuity to a level that no longer met the definition for a poor vision outcome was rare. Greater baseline tumor apical height and shorter distance between the tumor and the foveal avascular zone (FAZ) were the factors most strongly associated with loss of six or more lines of visual acuity after treatment. These two factors and baseline visual acuity also were strongly associated with visual acuity 20/200 or worse after treatment. Patient history of diabetes, presence of tumor-associated retinal detachment, and tumors that were not dome shaped also were associated with greater risk for both of the poor vision outcomes. CONCLUSIONS: Forty-three percent to 49% of treated eyes had substantial impairment in visual acuity by 3 years after I(125) brachytherapy, defined as a loss of six or more lines of visual acuity from the pretreatment level (49% of eyes) or visual acuity of 20/200 or worse (43% of eyes) that was confirmed at the next 6-month examination. Patients with a history of diabetes and patients whose eyes had thicker tumors, tumors close to or beneath the FAZ, tumor-associated retinal detachment, or tumors that were not dome shaped were those most likely to have a poor visual acuity outcome within 3 years after I(125) brachytherapy.

Evaluation of patients with visual field defects following macular hole surgery using multifocal electroretinography.

PURPOSE: To investigate patients with visual field defects following macular hole surgery to determine the cause of such defects, specifically with reference to ischemic damage versus mechanical trauma. METHODS: Five patients with known visual field defects following macular hole surgery were studied with Goldmann perimetry, Humphrey automated perimetry, and multifocal electroretinography (MERG). Three patients returned at a later date for nerve fiber layer analysis. RESULTS: None of the five patients demonstrated evidence of a- or b-wave loss on MERG in the regions corresponding to the visual field defects. Two of three patients studied with the nerve fiber layer analyzer demonstrated significant loss of nerve fiber layer thickness in the quadrant corresponding to the field defect. CONCLUSION: The normal MERG results indicate that the possibility of an arteriolar occlusion as the principal cause for the defects is unlikely in most cases. Data suggest that the site of damage is in the nerve fiber layer, although the specific cause of this damage remains to be determined.

Foveal cysts: a premacular hole condition associated with vitreous traction.

OBJECTIVE: To define the clinical findings, cause, and outcome of patients with foveal cysts due to vitreous traction. METHODS: Follow-up of 18 patients with foveal cysts and no posterior vitreous detachment (PVD). Changes were documented in visual acuity, the appearance of the fovea, or the development of a macular hole or PVD. We studied 8 eyes using the retinal thickness analyzer. RESULTS: On follow-up, 9 of 23 eyes did not develop a PVD and still had a foveal cyst; 8 of 23 developed a full-thickness macular hole; 4 of 23 developed a PVD with resolution of the cyst; and 2 eyes underwent vitrectomy for the cyst before a full-thickness hole developed. Analysis with the retinal thickness analyzer showed splitting within the middle retinal layers and in some cases unroofing or absent inner retinal layers in the center of the cyst. CONCLUSIONS: Foveal cysts are caused by vitreous traction. These eyes may remain stable, develop full-thickness holes, or develop a PVD with resolution of the cystic changes. A foveal cyst seems to be a common finding in patients with foveal traction from a variety of mechanisms.

Systemic small noncleaved cell lymphoma presenting as a posterior choroidal mass.

PURPOSE: To describe a patient with intraocular involvement by systemic, small noncleaved cell lymphoma. METHODS: Case report and review of the literature. RESULTS: A patient presented with a diffusely elevated choroidal mass. Systemic evaluation led to the diagnosis of unsuspected disseminated lymphoma. CONCLUSION: Small noncleaved cell lymphoma should be included in the differential diagnosis of a choroidal mass.

Regulation of uveal melanoma interconverted phenotype by hepatocyte growth factor/scatter factor (HGF/SF).

Human uveal melanoma disseminates initially and preferentially to the liver. This study describes the relationship between the expression of the c-met proto-oncogene (receptor for hepatocyte growth factor/scatter factor (HGF/SF)) in interconverted uveal melanoma cells (co-expressing vimentin and keratin intermediate filaments) and the regulation of their motogenic response to HGF/SF, a key step in local invasion and targeted dissemination to the liver. Expression of c-met in uveal melanoma cell lines correlates with both the appearance of an interconverted phenotype and invasive ability (measured in vitro). Using chemotactic checkerboard analysis, the greatest motogenic response to HGF/SF was achieved by invasive, interconverted, c-met-positive uveal melanoma cells. C-met was observed histologically in a uveal melanoma containing interconverted cells but was absent in a tumor composed of non-interconverted cells (vimentin positive/keratin negative). The c-met ligand, HGF/SF, although not expressed by uveal melanoma cell lines, was localized in tissue sections of primary uveal melanomas and metastatic melanoma to the liver. In the primary tumor, staining for HGF/SF was most intense at the level of the choriocapillaris, a finding that is significant because 1) highly remodeled neovascular loops and networks, which appear in tumors likely to disseminate, can be traced to the choriocapillaris and the draining vortex veins and 2) HGF/SF plays a role in tumor angiogenesis. Foci of metastatic melanoma to the liver stain diffusely for HGF/SF. Regulation of the uveal melanoma interconverted phenotype by HGF/SF may play an important role in the dissemination of this tumor.

Biologic determinants of uveal melanoma metastatic phenotype: role of intermediate filaments as predictive markers.

The long-range goal of our research is to develop intervention strategies based on newly discovered biologic mechanisms responsible for the invasive dissemination of metastatic uveal melanoma. To accomplish this goal, we have focused on the biologic relevance of novel marker proteins contributing to the uveal melanoma metastatic phenotype. The expression of vimentin intermediate filaments (IFs), a mesenchymal marker, is typical of melanomas, whereas carcinomas typically express keratin IFs, which are markers for epithelia. Thus, cells that coexpress both IFs are regarded as "interconverted" in that they display both mesenchymal and epithelial phenotypes. Although the biologic functions of IFs have remained enigmatic, there is substantial support to suggest that the significance of vimentin/keratin coexpression is linked with poor patient outcome in cutaneous melanoma. Our data demonstrate that human uveal melanoma cell lines (isolated from primary choroidal or ciliary body melanomas and from foci of metastatic uveal melanoma to the liver), which contain predominant populations of cells that coexpress vimentin/keratins 8 and 18 (keratins 8,18) IFs, were 6-fold more invasive through collagenous extracellular matrices in vitro, compared with uveal melanoma cells expressing vimentin only, and were 8- to 13-fold more invasive than normal uveal melanocytes. Colocalization of vimentin/keratins 8,18 in cell cultures was corroborated by immunohistochemistry in histologic sections of tumors from which the cell lines were derived. Minor populations of these cells also coexpressed keratins 13 and 17. Experimental down-regulation of the predominant keratins 8,18 in the interconverted cells, using 16-mer antisense oligonucleotides, resulted in a significant decrease in the migratory ability of the cells-similar to levels achieved by cells positive only for vimentin. These findings provide justification for additional studies of the association between coexpression of IFs vimentin/keratins 8,18 and uveal melanoma metastasis.

Imaging the microvasculature of choroidal melanomas with confocal indocyanine green scanning laser ophthalmoscopy.

OBJECTIVE: To image the microvasculature of choroidal melanoma with a new confocal scanning laser ophthalmoscope. METHODS: Eighteen consecutive patients, each with a unilateral choroidal melanoma, were examined prospectively. Indocyanine green angiography was performed with a new confocal scanning laser ophthalmoscope that enabled serial optical sectioning through the tumor. Two additional patients were studied with indocyanine green angiography and confocal scanning laser ophthalmoscopy just before enucleation for posterior choroidal melanomas. The histologic identification of microvasculature patterns was compared with the angiograms for these patients. RESULTS: In the series of 18 patients, 16 (89%) indocyanine green angiograms with optical sectioning revealed tubular structures within the melanoma that were identified as tumor vessels based on their angiographic appearance. The microvasculature patterns identified by indocyanine green angiography correlated well with the histologic appearance of these microvasculature patterns in both patients for whom histologic verification was available. CONCLUSIONS: This preliminary study suggests that indocyanine green angiography with confocal scanning laser ophthalmoscopy images the microvasculature of choroidal melanomas and may be capable of detecting microvasculature patterns that have been shown to be prognostically significant from histopathological studies.

Ferromagnetic hyperthermia: functional and histopathologic effects on normal rabbit ocular tissue.

Ferromagnetic (FM) hyperthermia has previously been evaluated in a rabbit tumour model of ocular melanoma. To study the effect of focal heating in normal rabbit eyes, FM seeds were implanted into a 14-mm episcleral plaque an heated to operating temperatures of 48 or 58 degrees C. Thermal induction was performed by placing rabbits in a uniform, oscillating (11 kHz) magnetic field operating at 1200 W and as H-field strength of 265 A/m. Eyes were heated for 60 min with continuous scleral temperature monitoring. Hyperthermic effects were monitored by direct opthalmic examination, fundus photography, serial electroretinography and histopathology. Intraocular temperatures were mapped with direct fiberoptic thermometry. All treatment effects were confined to the area covered by the episcleral plaque. Direct ophthalmoscopic examination revealed early retinal whitening during heat induction followed by localized exudative retinal detachments, limited to the area of the retinal surface overlying the plaque, that resolved spontaneously. Serial electroretinography was virtually indistinguishable between the 48 and 54 degrees C temperature groups. We noted a minimal alteration in a- and b-wave amplitudes with no changes in implicit times. Histopathology at 3 weeks post-treatment documented chorioretinal scarring overlying the thermal plaque treatment zone. No evidence of heamorrhage infection, cataract or scleral thinning was noted. This study documents the apparent focal containment of thermal effects with FM heating utilizing operating temperatures ad high as 54 degrees C for 60 min, and discloses no evidence of diffuse ocular toxicity.

Subacute sclerosing panencephalitis manifesting as viral retinitis: clinical and histopathologic findings.

PURPOSE AND METHODS: To describe the clinical and histopathologic features of a patient with viral retinitis secondary to subacute sclerosing panencephalitis. RESULTS: The patient was a human immunodeficiency virus-negative intravenous drug abuser with an acute retinitis that later progressed to encephalitis despite aggressive treatment for possible viral, protozoal, bacterial, and rickettsial infections. The patient had many of the characteristic findings of subacute sclerosing panencephalitis, including a history of measles in early childhood, myoclonus, periodic complexes on electroencephalographic testing, persistently elevated serum and cerebrospinal fluid antimeasles immunoglobulin G (IgG) titers, and a cerebrospinal fluid oligoclonal IgG gammopathy. Ultrastructural examination demonstrated numerous filamentous microtubular intranuclear viral inclusions in the nuclear layers of the retina consistent with the measles virus. This case is unusual in that our patient developed subacute sclerosing panencephalitis later in life and because there was an 8-year period between presumed viral infections in the two eyes. CONCLUSIONS: An acute retinitis in an intravenous drug abuser is not always caused by human immunodeficiency virus-related infections; not all viral retinitis responds to therapy; and mortality as well as the usual morbidity may be associated with viral retinitis. One might consider the diagnosis of subacute sclerosing panencephalitis in a young person with an acute retinitis with little or no vitreal inflammation and lack of response to anticytomegalovirus and antitoxoplasmosis therapy.

Correlation of ultrasound parameter imaging with microcirculatory patterns in uveal melanomas.

Previous studies demonstrated a correlation between acoustic backscatter parameters and survival in ocular melanoma. The histologic presence of microvascular networks in ocular melanoma is also associated with death from metastases. This study tests the hypothesis that melanomas grouped on the basis of these microvascular patterns are separable by ultrasound spectrum analysis. We scanned 40 melanomas using a 10-MHz ultrasound unit equipped for digitization of radio frequency data. After enucleation, tumors were sectioned in planes corresponding to the ultrasonographic examination and stained to demonstrate microcirculation. Acoustic spectral parameters were compared between 14 melanomas with a nevuslike microcirculation and 26 with foci of high-risk microvascular structures. Smaller scatterer size, lower acoustic concentration and greater spatial variability were found to correlate with high-risk microvascular patterns and areas of cystic degeneration. We suggest that nonvascular extracellular matrix components associated with microvessels may be responsible for the correlation of acoustic parameters with microvascular pattern and distribution.

Iatrogenic central retinal vein occlusion and hyperviscosity associated with high-dose intravenous immunoglobulin administration.

PURPOSE: To describe a patient with iatrogenically induced central retinal vein occlusions secondary to serum hyperviscosity from intravenous immunoglobulin administration. METHOD: Case report. RESULTS: The patient developed bilateral central retinal vein occlusions in association with high-dose intravenous immunoglobulins. The central retinal vein occlusions resolved when the immunoglobulins were withheld and serum hyperviscosity decreased. CONCLUSION: Administration of high-dose intravenous immunoglobulins can be associated with hyperviscosity syndrome manifested by central retinal vein occlusion.

Visual field defects after macular hole surgery.

PURPOSE: To describe a group of patients with dense visual field defects following macular hole surgery. METHODS: Nine (7%) of 125 patients reviewed noted onset of dense visual field defects following uncomplicated vitrectomy with gas-fluid exchange for the treatment of macular hole. Patient records were reviewed to investigate the etiology of these defects. RESULTS: Eight (89%) of nine eyes that had surgery for macular hole developed dense, wedge-shaped visual field defects in the temporal periphery. One eye had an inferonasal wedge-shaped defect extending to fixation. Seven (78%) of nine eyes had generalized or focal narrowing of the retinal arteriole extending into the area of retina corresponding to the visual field defect, and five (56%) of nine eyes developed mild to moderate segmental nasal optic disk pallor. Postoperative fluorescein angiography disclosed one eye with delayed filling of the retinal arteriole extending into the area of retina corresponding to the visual field defect. Vitrectomy specimens showed no evidence of nerve fiber layer or internal limiting membrane in eight (89%) of nine eyes. CONCLUSIONS: Visual field defects can occur following vitrectomy and gas-fluid exchange for macular hole. The most common visual field defect is dense and wedge-shaped and involves the temporal visual field. Although unclear, the etiology may involve trauma to the peripapillary retinal vasculature or nerve fiber layer during elevation of the posterior hyaloid or during aspiration at the time of air-fluid exchange, followed by compression and occlusion of the retinal peripapillary vessels during gas tamponade.

Expression of type VI collagen in uveal melanoma: its role in pattern formation and tumor progression.

Choroidal and ciliary body melanomas disseminate exclusively by a hematogenous route because there are no lymphatics inside the eye. Although angiogenesis is an absolute precondition for metastasis in this tumor system, not all morphologic expressions of tumor angiogenesis are associated with metastasis from choroidal and ciliary body melanomas. Specifically, the remodeling of the microcirculation to form vascular networks is very strongly associated with metastasis. Type VI collagen is upregulated in tissue remodeling and the generation of tissue patterns and is either not present in the normal choroid or present at very low levels. This study was designed to investigate the possible expression of type VI collagen in the stroma of choroidal and ciliary body melanomas. Type VI collagen was detected in tissue sections from five primary choroidal melanomas and three melanomas involving the choroid and ciliary body in the subendothelial compartment of the microcirculation and in avascular areas by immunohistochemistry. Melanoma cell lines were established from each of these tumors. Cultured melanoma cells invaded into type I collagen gels and expressed type VI collagen by immunohistochemistry. Using specific primers for human type VI collagen, the expected band size (413 base pairs) was isolated from one of the cell lines by reverse transcriptase PCR. The presence of type VI collagen in the melanoma tumor stroma reflects active remodeling of the uveal extracellular matrix microenvironment by the melanoma cells themselves. Before the formation of the microvasculature, the expression of type VI collagen and of the other matrix components, such as hyaluronan, to which it binds, may erect a scaffold permitting the formation of higher order stromal patterns such as vascular networks. These stromal patterns, which are markers of tumor progression, may be detectable clinically by a specialized form of ultrasonography that detects backscatterers of the same dimension as tissue compartments encircled by vascular loops in networks.

The use of intravitreal tissue plasminogen activator in the treatment of experimental subretinal hemorrhage in the pig model.

PURPOSE: To clinically and surgically evaluate clot lysis in an animal model of subretinal hemorrhage after intravitreal injection of tissue plasminogen activator. METHODS: Autologous subretinal hemorrhages were created via a transvitreal approach in 18 pigs. The next day (day 1) animals were randomly selected to receive either an intravitreal injection of 0.1 mL balanced salt solution or 0.1 mL tissue plasminogen activator (25 micrograms) followed by observation or vitrectomy a day later. On day 2, six pigs (all treated with tissue plasminogen activator) underwent a vitrectomy in which aspiration of the subretinal hemorrhage was attempted. The other eyes were evaluated for clot lysis by ophthalmoscopy at days 3, 10, and 30. All eyes were examined histopathologically. RESULTS: The eyes that had been treated with tissue plasminogen activator demonstrated a color change at the peripheral margin, which suggested that clot lysis had occurred. At the time of the vitrectomy, the clots were liquefied partially; removal by aspiration alone, however, was not possible. Photoreceptor damage was moderate to severe by day 10 in all eyes, whether they were treated with tissue plasminogen activator or balanced salt solution. All eyes that underwent vitrectomy had moderate to severe photoreceptor damage. CONCLUSIONS: In this animal model, intravitreal tissue plasminogen activator was associated with features that suggested partial clot lysis; tissue plasminogen activator did not produce sufficient lysis to allow surgical removal by aspiration alone, however.

Evaluation of anterior segment tolerance to short-term intravitreal perfluoron.

PURPOSE: A study was performed to evaluate corneal and anterior segment toxicity from short-term (24-hour) intravitreal use of perfluoro-n-octane. METHODS: Forty aphakic, vitrectomized eyes of pigmented rabbits underwent intravitreal injection of either 0.5 ml of perfluoro-n-octane (Perfluoron; Infinitech, St. Louis, MO; treated) or 0.5 ml balanced saline solution (control). Perfluoron was allowed to remain in the vitreous cavity for 24 hours. Serial measurements of corneal pachymetry and pneumotonometry were performed at 1, 4, 12, and 24 hours after injection. After 24 hours, endothelial cell morphology and barrier function were evaluated. RESULTS: No significant differences in corneal thickness or intraocular pressure were noted between the two groups at any of the time points studied, and no differences in endothelial cell density/hexagonality or endothelial cell barrier function were observed 24 hours after injection. CONCLUSIONS: In the absence of sustained corneal contact, no evidence of significant acute corneal or anterior segment toxicity was observed in response to short-term intravitreal perfluoro-n-octane in aphakic, vitrectomized rabbit eyes.