Biomedical subjects

Mohan N Iyer

Publications and source records attributed to Mohan N Iyer.

8 recordsLinked to original sources

PubMed2007

Long-term retinal toxicity of intravitreal commercially available preserved triamcinolone acetonide (Kenalog) in rabbit eyes.

PURPOSE: To investigate whether intravitreal Kenalog (IVTK; Bristol Meyers Squibb Company, Princeton, NJ) produces histologic or electroretinographic changes in the rabbit retina up to 3 months after injection. METHODS: Ten Dutch-belted rabbits were injected with 4 mg/0.1 mL Kenalog in one eye and 0.1 mL physiologic salt solution (PSS) in the fellow eye. Simultaneous bilateral dark-adapted electroretinography was performed 2 weeks and 12 weeks after injection in 10 and 6 rabbits, respectively. Saturated a-wave amplitude, maximal scotopic b-wave amplitude, and individual a-wave and b-wave amplitudes of IVTK-injected and control eyes were compared at 2 and 12 weeks after injection. Light microscopy was performed on both eyes of three animals 3 months after injection. Immunohistochemistry was performed with antibodies recognizing vimentin and human alveolar macrophage (HAM)-56, markers of glial cells and macrophages, respectively. RESULTS: No significant difference was observed in the saturated a-wave or maximal scotopic b-wave amplitudes between the PSS-injected eyes and the IVTK-injected eyes at 2 weeks (P = 0.95 and P = 0.56, respectively) and 12 weeks (P = 0.82 and P = 0.17) after injection. Light microscopy and immunohistochemistry disclosed only rare macrophages in the vitreous of IVTK-injected eyes. Retinal layers, retinal pigment epithelium, and choriocapillaris in treatment and control eyes were unremarkable. CONCLUSIONS: No demonstrable electroretinographic or histologic changes occurred to suggest immediate or delayed widespread retinal toxicity of IVTK.

Animals↗

PubMed2006

Short-term course of intraocular pressure after intravitreal injection of triamcinolone acetonide.

OBJECTIVE: To describe the natural history of intraocular pressure (IOP) within the first 30 minutes after intravitreal injection of triamcinolone acetonide (TA). DESIGN: Prospective, interventional, consecutive case series. PARTICIPANTS: Thirty-eight consecutive patients who met inclusion and exclusion criteria and underwent intravitreal injection of 0.1 ml (4 mg) of TA were studied. METHODS: Intraocular pressure was measured by Goldmann applanation tonometry at baseline; immediately after injection; and at 2, 5, 10, 20, and 30 minutes after injection. MAIN OUTCOME MEASURES: Intraocular pressure measurements at baseline; immediately after intravitreal injection; and 2, 5, 10, 20, and 30 minutes after injection, and percentage of patients with IOP < or = 24 mmHg at 30 minutes. RESULTS: Patients who did not experience vitreous reflux (30/38 [78.9%]) at the site of injection had a significant initial elevation of IOP that rapidly normalized. Patients who experienced vitreous reflux (8/38 [21.1%]) at the site of injection had either no change in IOP or a small drop in IOP that rapidly normalized. The IOP measured in millimeters of mercury immediately after injection (45.9 [no reflux], 12.6 [reflux]), 2 minutes after injection (39.9 [no reflux], 13.5 [reflux]), 5 minutes after injection (33.3 [no reflux], 13.8 [reflux]), 10 minutes after injection (26.4 [no reflux], 15.1 [reflux]), and 20 minutes after injection (21.8 [no reflux], 15.0 [reflux]) showed a statistically significant difference between the 2 groups. The difference in IOP between the 2 groups was not significant at baseline or 30 minutes after injection. At 30 minutes, 90% (95% confidence interval, 85.8%-95.2%) of patients without vitreous reflux had an IOP < 24 mmHg. CONCLUSIONS: Patients undergoing intravitreal injection of TA with no vitreous reflux have a risk of short-term elevation of IOP that rapidly normalizes over 30 minutes. In patients with vitreous reflux after the injection, the IOP declines immediately after injection and rapidly normalizes over 10 minutes.

Aged↗

PubMed2006

An eye model for practicing vitreoretinal membrane peeling.

A cost-effective, reusable practice eye model for epiretinal membrane peeling that uses easily obtained, commercially available materials was developed. A commercially available globe that is anatomically and optically similar to the human eye was modified by creating 2 ports that simulate superior sclerotomies. The model has a removable plastic anterior segment, which allows access to the posterior segment for practice membrane placement. Membranes were created on the macula by applying a coat of liquid skin bandage. Membrane peeling was performed under an ophthalmic operating microscope using a disposable flat vitrectomy lens. The basic skills required for membrane peeling can be demonstrated and acquired by practicing with this eye model. The practice eye model is expected to enhance the acquisition of skills required for epiretinal membrane peeling.

Epiretinal Membrane↗

PubMed2006

Intravitreal moxifloxacin: retinal safety study with electroretinography and histopathology in animal models.

PURPOSE: To determine whether moxifloxacin can be used safely as an intraocular antibiotic, retinal safety of intravitreal moxifloxacin was studied with electroretinography (ERG) and histopathology in animal models. METHODS: Moxifloxacin was injected into mouse eyes at intravitreal concentrations of 5 to 500 microg/mL and into rabbit eyes at 150 microg/mL. As the control, the vehicle was injected into the fellow eyes of each animal. Four weeks after injection, ERG recordings were performed, and animal eyes were processed for histologic examination. RESULTS: ERG studies showed no significant difference between control and moxifloxacin-injected eyes at any dose in either the mouse or rabbit model. Histologic examination revealed no retinal abnormality in mice at 5 to 100 microg/mL or in rabbits at 150 microg/mL intravitreal moxifloxacin. In mice at 500 microg/mL, occasional focal retinal necroses were observed, suggesting isolated retinal toxicity at this concentration of moxifloxacin. CONCLUSIONS: Intravitreal moxifloxacin, up to 100 microg/mL in mice or 150 microg/mL in rabbits, caused no ERG or retinal histologic abnormality. These results indicate that moxifloxacin is a safe intravitreal antibiotic in mouse and rabbit animal models. If proven safe and efficacious by further study in humans, intravitreal injection of moxifloxacin could be considered as an alternative to currently used antibiotics in selected patients with resistance or allergy to the more traditional antibiotics.

Animals↗

PubMed2006

Clearance of intravitreal moxifloxacin.

PURPOSE: To study the clearance of moxifloxacin after intravitreal injection in rabbits. METHODS: Intravitreal injections of 200 microg/0.1 mL of moxifloxacin were administered to rabbits. Four eyes per time point after injection (1 hour and 6, 12, 24, and 36 hours) and three eyes at 48 hours, respectively, were enucleated and immediately frozen and stored at -80 degrees C. Ocular dissection and isolation of frozen vitreous was performed. Vitreous samples were acquired at the various time intervals after injection. Antibiotic assays were performed with high performance liquid chromatography. RESULTS: The concentration of intravitreal moxifloxacin showed an exponential decay with a half-life of 1.72 hours. The mean vitreous concentration was 120.49 +/- 49.23 microg/mL 1 hour after injection, and declined to 20.23 +/- 5.85 microg/mL at 6 hours and 1.06 +/- 0.81 microg/mL at 12 hours, respectively. CONCLUSIONS: The vitreous concentrations achieved were several orders of magnitude greater than the MIC90 of organisms commonly involved in bacterial endophthalmitis, and therapeutic levels were maintained at 12 hours in uninflamed, phakic rabbit eyes. The pharmacokinetic data suggest that intravitreal moxifloxacin may have a role in the treatment of bacterial endophthalmitis.

Animals↗

PubMed2005

Staphylococcus hominis endophthalmitis associated with a capsular hypopyon.

PURPOSE: To report a case of Staphylococcus hominis endophthalmitis associated with a capsular hypopyon. DESIGN: Interventional case report. METHODS: A 51-year-old man presented with chronic postcataract extraction inflammation and underwent vitrectomy, partial capsulectomy, and intravitreal antibiotic injections, followed by explantation of the intraocular lens and capsule. RESULTS: A capsular hypopyon in the absence of an anterior chamber hypopyon was noted. Cultures of the vitreous and capsule revealed Staphylococcus hominis, a coagulase-negative gram-positive organism. CONCLUSIONS: We are unaware of previous reports of endophthalmitis caused by Staphylococcus hominis, and could find none in a computerized search using MEDLINE. This case adds Staphylococcus hominis to the list of causative organisms in chronic endophthalmitis and illustrates the rare finding of a capsular hypopyon.

Amikacin↗

PubMed2005

Intravitreal clearance of moxifloxacin.

PURPOSE: To study the clearance of a single dose of intravitreally injected moxifloxacin in rabbits. METHODS: Intravitreal injections of 200 microg/0.1 mL of moxifloxacin were performed in rabbits. Four eyes per time interval after injection (1, 6, 12, 24, 36 hours) and three eyes at 48 hours were enucleated, immediately frozen, and placed at -80 degrees C. Ocular dissection and isolation of frozen vitreous were performed. Antibiotic assays were performed with use of high-performance liquid chromatography. RESULTS: The concentration of intravitreal moxifloxacin showed an exponential decay with a half-life of 1.72 hours. The mean vitreous concentration was 120.49 +/- 49.23 microg/mL 1 hour after injection, which declined to 20.23 +/- 5.85 microg/mL at 6 hours and 1.06 +/- 0.81 microg/mL at 12 hours. The aqueous levels of moxifloxacin showed an exponential decay from 10 microg/mL at 1 hour after intravitreal injection to undetectable levels by 12 hours after injection. CONCLUSIONS: Moxifloxacin clearance from the vitreous is rapid and consistent with previous clearance studies of ciprofloxacin. Given that the injected dose corresponds to several times the minimum inhibitory concentration at which 90% of isolates are inhibited (MIC90) of organisms commonly involved in endophthalmitis, and that therapeutic levels are present up to 12 hours after injection, intravitreal moxifloxacin may have a role in the treatment of endophthalmitis.

Animals↗

PubMed2004

Subconjunctival antibiotics for acute postcataract extraction endophthalmitis--is it necessary?

PURPOSE: To evaluate the efficacy of adjunctive subconjunctival antibiotic injection in the treatment of acute postcataract extraction endophthalmitis. DESIGN: Retrospective cohort study. METHODS: Patients who presented with hand motions or better vision and received subconjunctival antibiotics (SC+ group) were compared with those who did not (SC- group) in the treatment of acute postoperative endophthalmitis. RESULTS: The rate of obtaining a final vision of 20/40 or better was 60% in the SC+ group (n = 25) compared with 72% in the SC- group (n = 18) (P =.69), and the mean change in logMAR was -1.36 (improvement) versus -1.34 (P =.93). Based on a linear regression model controlling for presenting vision, there was no statistical difference in the mean logMAR change between the two groups (P =.73). CONCLUSION: Subconjunctival antibiotic injection as an adjunct to intravitreal antibiotics was unassociated with treatment benefit in patients with acute postoperative endophthalmitis presenting with vision of hand motions or better.

Acute Disease↗