Change in retinal vessel diameter and choroidal thickness in patients with severe COVID-19: Change In Retinal Parameters In Patients With Severe COVID-19.

PURPOSE: To compare the differences in retinal vascular structure and choroidal thickness between the active disease and post-recovery periods in COVID-19 patients and healthy controls. MATERIAL AND METHODS: This prospective, cross-sectional study included 30 eyes from 30 patients with severe COVID-19 and 30 eyes of 30 sex-matched healthy controls. Central macular thickness (CMT), subfoveal choroidal thickness (CT) and retinal vascular changes of patients were measured after positive polymerase chain reaction (PCR) (where the patient had COVID-19-related symptoms) and then three months after two negative PCRs. Laboratory parameters, including C-reactive protein and d-dimer levels, were also recorded. RESULTS: The mean age of the patients was 47.90 ± 9.06 years in patients group, 49.07 ± 8.41 years in control goups (p = 0.467). In terms of choroidal thicknesses subfoveal, nasal and temporal region were significantly higher in the active disease period than control group (p = 0.019, p = 0.036, p = 0.003, respectively). When the after recovery period was compared with the control group in terms of choroidal thickness, although the choroidal thickness was higher in all regions, this difference was not found statistically significant. There was no statistically significant difference in CMT between groups (p = 0.506).The mean venous and arterial wall thicknesses were significantly higher in the active period than after recovery (p = 0.023, p = 0.013, respectively) but there were no differences between after recovery and control groups in the pairwise comparison (p = 0.851, p = 0.715, respectively). CONCLUSION: In patients with severe COVID-19, there are changes in thickness of the choroid and retinal vessel walls. While vascular wall thickness increases due to inflammation, the absence of lumen changes may be associated with hemodynamic variables.

Severe COVID-19 and Retina: Are There Any Retinal Manifestations?

PURPOSE: To investigate whether there are retinal lesions associated with severe COVID-19. METHODS: We studied 232 symptomatic subjects aged 18 - 65 years who had severe COVID-19 and had received treatment. The evaluations included ophthalmological examinations, optical coherence tomography (OCT), imaging modalities with near infrared reflectance (NIR), fundus autofluorescence (FAF), and fundus photography (FP). RESULTS: The mean age of the patients was 49 years, and 67.6% of them were men. There were no findings of microhemorrhage, cotton wool spots (CWS), vitritis, or retinitis in the examination and imaging. CONCLUSIONS: This study indicates that retinal involvement as a complication associated with COVID-19 is questionable, although some reports have demonstrated a relationship that may occur secondary to existing systemic diseases.

Ocular penetration of topically applied 1% tigecycline in a rabbit model.

AIM: To evaluate ocular penetration of topically applied 1% tigecycline. METHODS: Forty-two New Zealand White rabbits were divided into 3 groups. A 50 µL drop of 1% tigecycline was administered in group 1. In groups 2 and 3, the drop was administered every 15min for 60min (keratitis protocol). Aqueous humor samples in groups 1 and 2 were collected under general anesthesia at 15, 30, 45, 60, 120, and 180min after the last drop. All animals in group 3 were euthanatized. Cornea, vitreous and blood samples were collected 60 and 120min after the last drop. Tigecycline concentrations were measured using high performance liquid chromatography-mass spectrometry (LC-MS/MS). RESULTS: The peak aqueous humor tigecycline concentration [mean 0.73±0.14 mg/L (SD) and 2.41±0.14 mg/L, respectively] occurred 45min after topical drug application in groups 1 and 2. Group 3 mean values in the cornea, and vitreous, were 3.27±0.50 µg/g, and 0.17±0.10 mg/L at 60min and 3.17±0.77 µg/g and 0.20±0.07 mg/L at 120min, respectively. Tigecycline serum concentrations were negligible. CONCLUSION: Tigecycline levels in the aqueous humor in groups 1 and 2, and in the cornea in group 3 exceeded the minimum inhibitory concentrations of most gram-positive organisms that cause bacterial keratitis and endophthalmitis.

Effect of topical cyclopentolate on post-operative pain after pterygium surgery.

OBJECTIVES: The aim was to evaluate the effectiveness of topical cyclopentolate following pterygium surgery for post-operative ocular pain. METHODS: All participants had nasal pterygium and underwent pterygium excision and conjunctival autografting with fibrin glue. Participants were randomised into two groups. Participants in group 1 received one per cent cyclopentolate eye drops and artificial tears upon completing surgery and were prescribed self-administered drops three times daily for three days, while participants in group 2 received a control (artificial tears) in a manner identical to group 1. Data were gathered regarding post-operative pain intensity experienced during each of the three days. Pain was graded from zero to 10 according to a visual analogue scale, in which zero signified no pain and 10 signified severe, unbearable pain. RESULTS: This study analysed data regarding 38 participants in group 1 and 40 participants in group 2. Results were defined as median with interquartile range (IQR); median of the pain scores at days one, two and three were as follows, respectively: 4 (IQR 2), 2.5 (IQR 1) and 2 (IQR 1.25) for group 1 and 5 (IQR 1), 3 (IQR 1.75) and 3 (IQR 1) for group 2. Pain scores were significantly lower for group 1 compared with group 2 at days one, two and three (p < 0.05). CONCLUSIONS: Topical cyclopentolate seems to be effective and well tolerated following pterygium surgery for post-operative ocular pain.

Daptomycin versus Vancomycin in an Enterococcus faecalis Endophthalmitis Rabbit Model.

PURPOSE: To compare bactericidal activities of daptomycin (DAP) and vancomycin (VAN) in an experimental rabbit model of Enterococcus faecalis endophthalmitis. MATERIALS AND METHODS: The right vitreous cavities of 24 New Zealand rabbits were inoculated with 100 colony-forming units of E. faecalis; and after 24 h, rabbits were randomly divided into three groups. DAP group (n = 8, 0.2 mg/0.05 ml intravitreally), VAN group (n = 8, 1 mg/0.05 ml intravitreally) and balanced salt solution group (BSS, n = 8, 0.05 ml intravitreally). Clinical examination scores were recorded, and vitreous aspirates were obtained for microbiological analysis on days 0, 1, 2, 3 and 4. Rabbits were sacrificed, and the eyes were enucleated for histopathological assessment. RESULTS: There was no difference between the DAP, VAN and BSS groups in terms of the clinical grading of endophthalmitis 24 h after the inoculation. The bacterial counts were similar between the VAN and DAP groups except on day 1, where it was significantly lower than those in the VAN group (p = 0.003). On day 4, 62% of the eyes treated with DAP, and 50% of the eyes treated with VAN were sterilized. All of the eyes from the BSS group showed increasing bacterial growth from day 0 to day 4. There was no difference between the DAP and VAN groups in terms of the histopathological and clinical examination scores, while they were significantly lower than those in the BSS group. CONCLUSIONS: This study demonstrates evidence of the effectiveness of DAP for the treatment of experimental E. faecalis endophthalmitis.

Ozurdex completely located inside a crystallized lens - Results of 14 months.

PURPOSE: To report the therapeutic efficacy and results of an accidentally injected intralenticular sustained-release dexamethasone implant (Ozurdex) in a patient with macular edema secondary to central retinal vein occlusion at 14 months after injection. OBSERVATIONS: We present a 70-year-old female patient with central retinal vein occlusion who underwent an Ozurdex injection. Patient discontinued from the treatment period during the 14-month and there was no ophthalmologic examination of the patient. Detailed ophthalmological examination was performed. Ozurdex localization was determined by Pentacam rotating Scheimpflug System. The implant was accidentally injected into the crystalline lens. It did not cause a totally lens opacification but did result only in a posterior subcapsular cataract. The macular edema did not resolve, and the patient underwent phacoemulsification surgery. CONCLUSIONS AND IMPORTANCE: Ozurdex that totally located inside the crystallize lens may not have the therapeutic effects.

Peripapillary choroidal thickness in patients with chronic obstructive pulmonary disease.

OBJECTIVE: To evaluate the peripapillary choroidal thickness of patients with chronic obstructive pulmonary disease (COPD) via enhanced depth imaging optical coherence tomography (EDI-OCT). MATERIALS AND METHODS: A total of 80 patients with COPD (80 eyes) and 50 control subjects (50 eyes) were enrolled. Choroidal scans and the retinal nerve fiber layer (RNFL) thickness were obtained for all eyes using OCT. RESULTS: The average peripapillary choroidal thickness measurements of the COPD group (147.58 ± 53.53 µm) were lower than the control group (160.84 ± 44.73 µm) (p = 0.068). Inferior segment thicknesses were significantly thinner than the other segments (p < 0.05). Subfoveal choroidal thickness and RNFL thickness measurements of the COPD group were also lower than those of the control group (p = 0.111). CONCLUSION: Hypoxia in COPD seems to affect the choroidal thickness. Thinning of the choroid may be attributed to increased vascular resistance and reduced blood flow in patients with COPD. The possible effects of the disease to the eye may be clarified through the role of the choroidal vasculature in the blood supply of the anterior optic nerve head.

Effect of nepafenac eye drops on pain associated with pterygium surgery.

OBJECTIVE: To assess the effects of nepafenac ophthalmic suspension 0.1% for control of pain in patients undergoing pterygium surgery. METHODS: This randomized, double-masked placebo-controlled study included 62 adults undergoing pterygium surgery. Patients were randomly assigned to receive nepafenac ophthalmic suspension 0.1% or balanced salt solution placebo. They were asked to assess the level of pain using an 11-point numeric rating scale at 6, 12, 24, 48, and 72 hr after surgery. Patients also were evaluated daily for the progression of corneal epithelial healing until complete closure was observed. RESULTS: Except at 72 hr after surgery, the patients reported significantly less pain in eyes receiving nepafenac than in eyes receiving placebo. There was no statistical difference between the two groups in corneal epithelial healing. CONCLUSIONS: Treatment with nepafenac ophthalmic suspension 0.1% significantly reduced postoperative pain compared with placebo after pterygium surgery.

The effect of rebreathing and hyperventilation on retinal and choroidal vessels measured by spectral domain optical coherence tomography.

OBJECTIVE: The purpose of this study was to examine the vasoreactivity in retina and choroid of the healthy eyes in response to experimentally altered partial arterial pressure of carbon dioxide (PaCO(2)) using a non-invasive technique, spectral domain optical coherence tomography (SD-OCT). MATERIALS AND METHODS: The study included non-smoking participants between 18 and 35 years of age, having visual acuity of 20/20 and with no systemic and ocular diseases. At baseline, the participants breathed room air (normocapnia). Hypocapnia was created with the help of hyperventilation; for this, the participants were instructed to draw deep and quick breaths, resulting one breathing cycle per 2 s. To create hypercapnia subjects rebreathed from a 5 l bag at least 3 min. Choroidal thickness and retinal artery diameter were measured at baseline, and hyperventilation and rebreathing conditions by SD-OCT. RESULTS: Twenty eyes of 20 healthy subjects were included in this study. Their mean age was 24.90 ± 5.32 years. Hyperventilation caused a significant reduction in choroidal thickness, compared with baseline, at all points; whereas rebreathing caused no significant change at all points. The mean diameters of the arteries were 151.80 ± 7.88 µm, with a significant decline to 148.90 ± 7.25 µm at hyperventilation condition and a significant increase to 153.50 ± 7.88 µm at rebreathing condition (p = 0.018, p = 0.043, respectively). CONCLUSION: This study demonstrated that, SD-OCT was a useful tool in measuring the ocular vascular response under hypercapnia and hypocapnia conditions. These findings may be helpful for further understanding the physiological nature of ocular blood flow and this preliminary study provides a basis for future studies.

Clearance of intravitreal daptomycin in uveitis-induced rabbit model.

PURPOSE: To investigate the elimination rate of daptomycin after intravitreal injection in uveitis-induced rabbits. MATERIALS AND METHODS: Intravitreal injection of the single dose of 200 µg/0.05 mL daptomycin was administered to rabbits starting 24 h after induction of uveitis by an intravitreal endotoxin injection. Aqueous humor and vitreous humor samples of eight eyes per time point were collected at selected time intervals (1, 3, 6, 24, 48, 72 and 96 h), and the in vitreous half-life was calculated. Daptomycin concentrations in vitreous and aqueous humor were assayed with high-performance liquid chromatography. RESULTS: The vitreous concentration was noted to decline slowly with time. The mean vitreous concentration was 23.25 ± 10.99 µg/mL and 11.10 ± 3.33 µg/mL at 96 h in inflamed and normal eyes, respectively. The vitreous daptomycin concentration showed an exponential decay with a half-life of 25.67 h in normal eyes and 34.6 h in inflamed eyes. The aqueous levels of daptomycin in normal eyes were low but remained significantly higher than those of inflamed eyes. CONCLUSIONS: Given that the injected dose corresponds to several times the minimum inhibitory concentrations of organisms most involved in endophthalmitis, and that therapeutic levels are present up to 96 h after injection, intravitreal daptomycin should be considered for the treatment of endophthalmitis caused by Gram-positive bacteria.

New therapy option for treatment of methicillin-resistant Staphylococcus aureus keratitis: tigecycline.

PURPOSE: The aim of the present study was to evaluate the effectiveness of topically applied tigecycline for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) in a rabbit model. METHODS: Experimental bacterial keratitis was induced in rabbits by a corneal intrastromal injection of 100 colony-forming units (CFUs) of MRSA bacteria. Sixteen hours after the injection, 28 rabbits were randomly divided into 4 treatment groups of 7 rabbits each. In each group, the rabbits' eyes were treated topically with 19 doses of topical tigecycline (10 or 50 mg/mL), vancomycin (50 mg/mL), or isotonic saline. Slit lamp examinations were performed before and after the inoculation by two observers masked to the study for the determination of clinical severity. Corneas were harvested for bacterial quantitation and histopathologic examination. RESULTS: No significant differences were observed in the clinical scores between pretreatment and posttreatment in the 4 groups (P>0.05). The mean difference between the pretreatment and posttreatment clinical scores from the 4 treatment groups was also not significant (P>0.05). All treatment groups had significantly lower CFUs compared with the control group. There were no significant differences in the bacterial load among the treatment groups. The minimum inhibitory concentration (MIC) for tigecycline was 0.12 µg/mL, whereas the MIC for vancomycin was 2.2 µg/mL. The tigecycline 10 mg/mL group had the lowest mean epithelial erosion values among the treatment groups. CONCLUSIONS: Topical tigecycline significantly reduced the bacterial load in infected rabbit corneas and may be as effective as vancomycin for the topical treatment of MRSA keratitis.

Discrimination of Epithelial Face of Conjunctival Autograft in Pterygium Surgery with Fibrin Glue.

A 48-year-old male patient was operated for pterygium. During surgery, the autograft surface was lost because of sponge contact. Presumed epithelial face of the autograft subsequently was attached to the bare sclera with fibrin glue. It was observed that the center of the autograft was freely movable with sponge. This finding showed the inverse implantation of the autograft. Because the glue does not stick to intact corneal or conjunctival epithelium, free movement of the center of the autograft shows that the graft is inversely implanted.

Evaluation of peripapillary choroidal and retinal nerve fiber layer thickness in eyes with tilted optic disc / Avaliação espessura da camada de fibras nervosas peripapilares da retina e coroide em olhos com disco óptico inclinado

Purpose: This study was performed to evaluate the retinal nerve fiber layer (RNFL) and peripapillary choroidal thickness in eyes with tilted optic disc in order to identify characteristic RNFL and peripapillary choroid patterns verified by optical coherence tomography (OCT). Methods: Twenty-nine eyes of 29 patients with tilted optic discs were studied with spectral-domain (SD)-OCT and compared with age and sex-matched control subjects in a prospective design. The imaging of RNFL was performed using circular scans of a diameter of 3.4 mm around the optic disc using OCT. For measurements of peripapillary choroidal thickness, the standar d protocol for RNFL assessment was performed. Results: SD-OCT indicated significantly lower superotemporal (p<0.001), superonasal (p=0.001), and global (p=0.005) RNFL thicknesses in the tilted disc group than those of the control group. Peripapillary choroid was significantly thicker at the site of the elevated rim of eyes with tilted disc (p<0.001). Conclusion: This study demonstrated a clinical characterization of the main tilted disc morphologies that may be helpful in differentiating a tilted disc from other altered disc morphologies. Further studies are recommended to study the comparison between glaucoma and tilted disc groups. .

Objetivo: Avaliar camada de fibras nervosas da retina (RNFL) e a espessura da coroide peripapilar em olhos com disco óptico inclinado a fim de identificar as características da RNFL e os padrões de coroide peripapilar verificados pela tomografia de coerência óptica (OCT). Métodos: Vinte e nove olhos de 29 pacientes com discos ópticos inclinadas foram estudados prospectivamente com OCT de domínio espectral (SD) e comparados com controles pareados por sexo e idade. As imagens da RNFL foi obtidas por meio de varreduras circulares com um diâmetro de 3,4 mm em torno do disco óptico usando OCT. Para as medições de espessura da coroide peripapilar, o protocolo padrão para avaliação da RNFL foi realizado. Resultados: O OCT SD indicou diminuição das espessuras significativas da RNFL superotemporal (p<0,001), superonasal (p=0,001), e global (p=0,005) no grupo disco inclinado em relação aos do grupo controle. A coroide peripapilar foi significativamente mais espessa no local da borda elevada dos olhos com disco inclinado (p<0,001). Conclusões: Este estudo demonstrou que a caracterização clínica das principais morfologias disco inclinado pode ser útil na diferenciação entre um disco inclinado de outras alterações morfológicas de disco. Seria importante a comparação entre grupos com glaucoma e com discos inclinados, estudos futuros. .

Measurement of choroid thickness in pregnant women using enhanced depth imaging optical coherence tomography.

PURPOSE: To investigate choroidal thickness in healthy pregnant women during different trimesters using enhanced depth imaging optical coherence tomography (EDI-OCT). METHODS: This prospective study included 90 healthy pregnant women in their first, second, or third trimester (groups 1, 2, and 3, respectively) and 30 non-pregnant healthy women (group 4). The age range for all groups was 18-40 years. Spectral domain optical coherence tomography scans were obtained to estimate the average choroidal thickness. Using EDI-OCT, we measured choroidal thickness manually from the outer border of the retinal pigment epithelium to the inner scleral border at the subfovea, 3 mm temporal, and 3 mm nasal to the fovea. Differences among groups were analyzed by one-way ANOVA. RESULTS: We found a statistically significant difference between groups 2 and group 4 for subfoveal, temporal, and nasal mean choroidal thickness (p=0.007, p<0.001, p=0.026, respectively). The mean choroidal thickness for group 2 was 395 ± 80 µm, 338 ± 74 µm, and 233 ± 61 µm at the regions subfoveal, temporal, and nasal to the fovea, respectively. In comparison, the mean choroidal thickness for group 4 was 335 ± 86 µm, 274 ± 54 µm, and 200 ± 53 µm at the regions subfoveal, temporal, and nasal to the fovea, respectively. No statistically significant differences were found for choroidal thickness among groups 1-4 (p=0.214, p=0.177, p=0.094, respectively) and between groups 3-4 (p=0.105, p=0.261, p=0.695, respectively) for all measured points. CONCLUSION: Our results suggest that choroidal thickening can occur at the regions subfoveal, temporal, and nasal to the fovea in the second trimester.

Antiangiogenic effect of itraconazole on corneal neovascularization: a pilot experimental investigation.

PURPOSE: To investigate the antiangiogenic effect of itraconazole for the prevention of experimentally induced corneal neovascularization and whether the efficacy depends on the route of administration. MATERIALS AND METHODS: Thirty-six rats were randomly divided into 6 groups with 6 rats in each group. Chemical cauterization of the cornea was performed using silver nitrate/potassium nitrate sticks, and the rats were subsequently treated daily with topical (10 mg/ml), subconjunctival (10 mg/ml) or intraperitoneal (19 mg/kg) itraconazole for 7 days. Control rats received topical, subconjunctival or intraperitoneal 0.9% saline. On the 8th day of the experiment, the rat corneas were photographed to determine the percentage area of the cornea covered by neovascularization. The maximum density of corneal neovascularization was determined by microscopy. RESULTS: The median percentage of corneal neovascularization for group 1 was 31.5% (95% confidence interval, 27.5-35.5%); in group 3, it was 32% (23.5-39.8%); in group 5, it was 47% (36.3-60.0%). The percentages of corneal neovascularization in groups 2, 4 and 6 (the control groups) were 70% (95% confidence interval, 60.7-77.3%), 69% (63.0-77.7%) and 68% (56.5-78.5%), respectively. The area of neovascularization was smaller after itraconazole treatment as compared to saline treatment. Further, the area of neovascularization was smaller after topical and subconjunctival administration than after intraperitoneal administration. Histological evaluation of the corneas showed the most extensive corneal neovascularization in the control group. No local or systemic adverse effects were seen from either treatment group. CONCLUSION: Itraconazole reduces corneal neovascularization shortly after chemical burn. However, a larger experimental study is necessary to confirm the data of this investigation.

Inhibition of corneal neovascularization by topical and subconjunctival tigecycline.

Objective. To investigate the effects of topical and subconjunctival tigecycline on the prevention of corneal neovascularization. Materials and Methods. Following chemical burn, thirty-two rats were treated daily with topical instillation of 1 mg/mL tigecycline (group 1) or subconjunctival instillation of 1 mg/mL tigecycline (group 3) for 7 days. Control rats received topical (group 2) or subconjunctival (group 4) 0.9% saline. Digital photographs of the cornea were taken on the eighth day after treatment and analyzed to determine the percentage area of the cornea covered by neovascularization. Corneal sections were analyzed histopathologically. Results. The median percentages of corneal neovascularization in groups 1 and 3 were 48% (95% confidence interval (CI), 44.2-55.8%) and 33.5% (95% CI, 26.6-39.2%), respectively. The median percentages of corneal neovascularization of groups 1 and 3 were significantly lower than that of the control group (P = 0.03 and P < 0.001, resp.). Histologic examination of samples from groups 1 and 3 showed lower vascularity than that of control groups. Conclusion. Topical and subconjunctival administration of tigecycline seems to be showing promising therapeutic effects on the prevention of corneal neovascularization. Furthermore, subconjunctival administration of tigecycline is more potent than topical administration in the inhibition of corneal neovascularization.

Pharmacokinetics of intravenously administered tigecycline in eye compartments: an experimental study.

PURPOSE: The purpose of this study was to evaluate the ocular distribution of intravenously administered tigecycline in a rabbit uveitis model. METHODS: Tigecycline, which has a broad spectrum of activity against many gram-positive, gram-negative, and anaerobic organisms, was given intravenously to rabbits at 7 mg/kg of body weight starting 24 h after induction of uveitis by intravitreal endotoxin injection. Tigecycline concentrations were determined by high performance liquid chromatography-mass spectrometry (LC-MS/MS) assay in the aqueous humor, vitreous humor, and plasma 1, 3, 6, and 24 h after administration of a single dose. RESULTS: The maximum concentrations were found within 1 h after the end of the intravenously given tigecycline, and were 1,308.60 ± 301.76 ng/mL in plasma, 181.40 ± 51.32 ng/mL in vitreous humor and 145.00 ± 55.29 ng/mL in aqueous humor of the inflamed eye. After 24 h, no drug was detectable in the aqueous and vitreous of the normal eyes, whereas small amounts of drug were detectable in inflamed eyes and in plasma. CONCLUSIONS: Tigecycline did not reach therapeutically significant levels in the aqueous and the vitreous humor of rabbit eyes. The findings suggest a limited role for intravenously administered tigecycline in the treatment of bacterial endophthalmitis.

Ocular penetration of intravenously administered colistin in rabbit uveitis model.

PURPOSE: The purpose of this study was to evaluate the ocular distribution of intravenously administered colistin in a rabbit uveitis model. METHODS: Colistin, a polypeptide antibiotic against the multidrug-resistant (MDR) Gram-negative organisms, was given intravenously to rabbits at 5 mg/kg of body weight starting 24 h after induction of uveitis by intravitreal endotoxin injection. Colistin concentrations were determined by high-performance liquid chromatography-mass spectrometry assay in the aqueous humor, vitreous humor, and plasma 0.5, 3, 6, and 24 h after administration of a single dose. RESULTS: The maximum colistin concentrations (mean±standard deviation) were found 0.5 h after the end of the intravenous administration and were 9.48±2.0 µg/mL in plasma and 0.62±0.07 µg/mL in the aqueous humor of the inflamed eye. After 24 h, no drug was detectable in the aqueous of the inflamed eyes. Colistin was undetectable in the aqueous of contralateral normal eyes at all time points. Drug concentrations in all the vitreous samples from both inflamed and normal eyes were undetectable, except at the 3-h inflamed eye group, and a colistin concentration of 0.02±0.01 µg/mL was found. Plasma levels of colistin fell to 0.93±0.07 and 0.24±0.08 µg/mL, after 3 and 6 h, respectively, and were not detectable 24 h after the given dose. CONCLUSIONS: In our model, colistin did not reach therapeutically relevant levels in the aqueous and in the vitreous humor of rabbit eyes. The findings suggest a limited role for intravenously administered colistin in the treatment of Gram-negative bacterial endophthalmitis.