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Biomedical subjects

T A Meredith

Publications and source records attributed to T A Meredith.

At least 37 records · Page 2Linked to original sources
PubMed1995

Persistent endophthalmitis after intravitreal antimicrobial therapy.

PURPOSE: To assess the frequency of persistent infection after injection of intravitreal antimicrobials as therapy for endophthalmitis and to determine if persistent infection influences the final visual outcome after treatment. METHODS: In a series of 42 eyes with culture-positive endophthalmitis of various types, the authors performed a second vitreous culture and injection of antimicrobial agents in 22 eyes. Repeat cultures were obtained 3 to 8 days after initial therapy in 20 of the 22 eyes. RESULTS: Twelve of the 22 eyes were persistently culture-positive. Organisms identified in the persistently culture-positive eyes included staphylococcal species (n = 4), Streptococcus (n = 4), Serratia (n = 1), Propionibacterium acnes (n = 1), and fungi (n = 2). Eyes in which the initial antimicrobial therapy failed to eradicate a bacterial infection had a worse outcome than those that were culture-negative on repeat sampling. Final visual acuity of 20/200 or better after repeat injection was attained in 4 of the 12 culture-positive eyes. CONCLUSION: A single injection of intravitreal antimicrobial agents may be insufficient to cure some cases of endophthalmitis, and a second injection should be considered in some circumstances.

Adolescent↗
PubMed1995

Vitreous cavity penetration of ceftazidime after intravenous administration.

PURPOSE: Penetration of ceftazidime, a third generation cephalosporin, into the vitreous cavity after intravenous administration was investigated. METHODS: Because antimicrobial penetration varies with surgical status of the eye and with inflammation, studies were conducted in phakic, aphakic, and aphakic, vitrectomized eyes in both normal and inflamed conditions. Ceftazidime 50 mg/kg was administered every 8 hours and vitreous cavity concentrations were tested at intervals from 2 to 72 hours after the initial dose. RESULTS: No penetration was found into control phakic and aphakic eyes, but drug concentrations were detected in inflamed eyes at 24 hours. Vitreous concentrations of ceftazidime in aphakic, vitrectomized eyes reached levels well above the minimal inhibitory concentration (MIC) for Pseudomonas organisms within 2 hours of intravenous administration in control eyes (8.5 micrograms/ml) and inflamed eyes (35.4 micrograms/ml). Inflammation and removal of the lens and vitreous significantly enhanced ceftazidime penetration at all time periods tested. CONCLUSION: Ceftazidime penetrates into the vitreous cavity of inflamed eyes after intravenous administration and achieves concentrations above the MIC for Pseudomonas organisms. Penetration is greatest in aphakic, vitrectomized eyes.

Animals↗
PubMed1995

Vitrectomy for vitreomacular traction syndrome with macular detachment.

PURPOSE: To describe the clinical characteristics of the vitreomacular traction syndrome with macular detachment and to report our surgical experience with this condition. METHODS: A retrospective chart and photographic review was performed on nine patients (nine eyes) who had a symptomatic decrease in visual acuity from a macular traction retinal detachment caused by vitreomacular traction syndrome. Vitrectomy was performed in each eye to reattach the retina. RESULTS: Intraoperative observation confirmed partial posterior vitreous separation with adherence of the posterior hyaloid to the detached retina and separation of the posterior hyaloid from the attached retina. After surgery the macula was reattached in seven eyes (78%). Visual acuity was improved in four eyes, stable in four eyes, and worse in one eye. CONCLUSION: Macular detachment may occur secondary to vitreomacular traction syndrome. Although the retina may be reattached surgically in these cases, visual improvement may be limited by chronic detachment, premacular fibrosis, cystoid macular edema, or macular schisis.

Aged↗
PubMed1995

Vancomycin levels after intravitreal injection. Effects of inflammation and surgery.

OBJECTIVE: Vancomycin hydrochloride for intraocular injection is the drug of choice for the treatment of suspected gram-positive endophthalmitis. To study its intraocular pharmacokinetics, we injected vancomycin into the vitreous cavity of phakic, aphakic, and aphakic-vitrectomized rabbit eyes and determined its rate of clearance. Inflamed eyes were compared to control eyes in each group. METHODS: Three groups of eyes were prepared. The eyes in Group 1 were phakic, the eyes in Group 2 had the lens removed, and the eyes in Group 3 had both the lens and central vitreous removed. Each group was subdivided into a control group and a group made inflamed by injection of heat-killed Staphylococcus epidermidis. Vancomycin hydrochloride 1 mg in 0.1 cc of diluent was injected into the midvitreous cavity and samples obtained at 2 or 3, 8, 24, and 48 hours after injection. Vancomycin concentrations were measured and clearance rates were calculated for each of the groups. RESULTS: Vancomycin was cleared substantially faster from aphakic-vitrectomized eyes (half-life 9.0 hours) and aphakic eyes (half-life 8.9 hours) than phakic eyes (half-life 25.1 hours). Inflammation increased the rate of elimination of vancomycin only in the aphakic group. CONCLUSIONS: Clearance of vancomycin from the phakic eye is prolonged compared to that of beta-lactam antibiotics, an important pharmacokinetic advantage in treating endophthalmitis. Its clearance from aphakic-vitrectomized eyes is dramatically faster than from phakic eyes and is similar to that of other antimicrobial agents.

Animals↗
PubMed1995

Intraocular injection of ceftazidime. Effects of inflammation and surgery.

OBJECTIVE: The clearance of ceftazidime from the rabbit vitreous cavity after injection into phakic, aphakic, and aphakic vitrectomized rabbit eyes was assessed and the duration of concentrations above the minimal inhibitory concentrations for target gram-negative bacteria was determined. To determine the effect of inflammation on the intraocular pharmacokinetics of ceftazidime, each anatomic group was subdivided into inflamed and control eyes. METHODS: Ceftazidime (2.25 mg) was into the vitreous cavity of inflamed and control rabbit eyes and its concentration was assayed 2, 8, 24, and 48 hours later. The half-life for each of the anatomic groups was calculated. RESULTS: The half-life of ceftazidime in control phakic eyes was 13.8 hours. In aphakic eyes the half-life was 11.8 hours and in the aphakic vitrectomized eyes the half-life was 4.7 hours. Inflammation slightly shortened the half-life in phakic (10.1 hours) and aphakic (8.7 hours) eyes. The half-life in aphakic vitrectomized inflamed eyes was 5.1 hours. CONCLUSION: Vitrectomy and lensectomy significantly shorten the half-life of ceftazidime after intravitreal injection. Inflammation increases clearance to a small degree in phakic and aphakic eyes.

Animals↗
PubMed1994

Pars plana vitrectomy for treatment of stage 2 macular holes.

OBJECTIVE: To assess the anatomic outcome and visual acuities at follow-up after pars plana vitrectomy in the management of stage 2 macular holes. DESIGN: Retrospective. SETTING: Retina Consultants, Ltd, St Louis, Mo. PATIENTS: Thirty-three patients, aged 43 to 75 years, with stage 2 macular holes. INTERVENTION: Total pars plana vitrectomy with separation of the posterior hyaloid membrane and injection of intraocular gas followed by postoperative face-down positioning. MAIN OUTCOME MEASURES: Visual acuity and anatomic appearance of the macular hole. RESULTS: Postoperatively, 20 (61%) of 33 eyes attained a visual acuity of 20/50 or greater. Twenty (61%) of 33 eyes showed an improvement in visual acuity, while nine (27%) of 33 were stable. Four (12%) of 33 eyes showed a decline in postoperative visual acuity with progression to a stage 3 macular hole. Twenty-five (76%) of 33 eyes showed stabilization or improvement in the appearance of the macular hole. CONCLUSIONS: Pars plana vitrectomy in conjunction with postoperative intraocular gas tamponade may result in visual and anatomic stabilization or improvement in eyes with stage 2 macular holes. However, because of limited natural history data, it is unknown whether these results are any better than those that might occur without surgery.

Adult↗
PubMed1994

Symptomatic choroidal neovascularization in blacks.

OBJECTIVE: To acquire descriptive clinical information regarding choroidal neovascularization (CNV) in black Americans. DESIGN: Retrospective review of 1308 fluorescein angiograms obtained during a 4-year interval. Color photographs and clinical records of all black patients with angiographically apparent CNV were subsequently reviewed. SETTING: Retina service of an inner-city county hospital in Atlanta, Ga, serving a predominantly black population. RESULTS: Thirty blacks with CNV (36 of 59 eyes) were identified, 26 (87%) of whom were female. Active, exudative neovascularization was present in at least one eye of 21 patients (70%). Patients were assigned to one of four diagnostic groups for analysis. Group 1 was made up of 13 patients (43%) with age-related macular degeneration with CNV. Women outnumbered men 5.5:1. Choroidal neovascularization was peripapillary in seven (54%) of these 13 patients. Group 2 was made up of six patients (20%) with idiopathic CNV, which was peripapillary in all eyes. Group 3 consisted of three women (10%) with idiopathic polypoidal choroidal vasculopathy. Group 4 was composed of eight patients (27%) with secondary CNV. The CNV was peripapillary in three (33%) of nine eyes, and women outnumbered men 7:1. CONCLUSIONS: The spectrum of neovascular maculopathy in blacks in the current study differed from that typically seen in whites, both clinically and demographically. Clinically, CNV was most commonly juxtapapillary (13 [68%] of 19 patients) and unilateral (12 [92%] of 13 patients) among the age-related macular degeneration and idiopathic groups, while six (20%) of 30 patients (all older than 50 years) had CNV in the absence of drusen or other known predisposing conditions. Disciform-stage CNV in both groups was associated with a greater degree of pigment proliferation than that typically noted in whites. Demographically, female predominance (87% overall) was dramatic compared with prior studies.

Adult↗
PubMed1994

Improved visual results after surgical repair of cytomegalovirus-related retinal detachments.

PURPOSE: This study was conducted to determine whether visual outcomes have improved after repair of retinal detachments (RDs) associated with cytomegalovirus (CMV) retinitis, and, if so, whether factors such as earlier intervention and changes in surgical technique have led to these results. METHODS: The authors performed a retrospective review of 35 eyes in 30 immunocompromised patients with CMV retinitis and RD who underwent pars plana vitrectomy with the use of silicone oil injection. Visual and anatomic results in eyes treated between January 1991 and April 1992 (group 1) were compared with eyes treated before January 1991 (group 2). Follow-up was limited due to patient mortality; median follow-up was 4.1 months in group 1 and 2.5 months in group 2. RESULTS: Best-attained postoperative visual acuities were better for group 1 than group 2 eyes, with 71% of group 1 eyes attaining visual acuity of 20/200 or better compared with 17% of group 2 eyes (chi-square1 trend = 12.3; P < 0.001). A similar result was found among eyes with macula-off detachments. Ambulatory visual acuity of 5/200 or better was achieved in 86% of group 1 versus 33% of group 2 eyes. There was a longer interval between diagnosis and surgery in group 2 compared with group 1 (7 versus 3 days); scleral buckling in conjunction with pars plana vitrectomy and silicone oil injection was used in more group 1 eyes. CONCLUSION: Earlier intervention, absence of preoperative optic atrophy, and macular CMV correlate with better postoperative visual acuity results. Pars plana vitrectomy combined with silicone oil for eyes with macula-off RDs can result in improved visual acuity.

Adult↗
PubMed1994

Magnetic resonance imaging findings in Vogt-Koyanagi-Harada syndrome.

BACKGROUND: Vogt-Koyanagi-Harada Syndrome (VKHS) is a systemic disorder consisting of bilateral panuveitis with associated cutaneous and neurologic findings. In the absence of extraocular manifestations, diagnosis of VKHS may be difficult. METHODS: The results of magnetic resonance imaging (MRI) in two patients with VKHS and of computed tomography (CT) in a third patient with VKHS are described. RESULTS: Bilateral, diffuse choroidal thickening with scleral sparing was the norm. Choroidal thickening was demonstrable, despite the normal fundus appearance and fluorescein angiogram, in one eye. Intense enhancement after administration of gadopentetate was seen in the acute stages, but not after corticosteroid treatment. High-intensity periventricular lesions were seen in one patient. CONCLUSION: MRI superbly discriminates the fibrous sclera from the choroid and allows for the detection of subclinical ocular and central nervous system disease. It is therefore a useful adjunct in the diagnosis and follow-up of VKHS.

Adult↗
PubMed1993

Effects of inflammation and surgery on amikacin levels in the vitreous cavity.

Intraocular injection of amikacin is increasingly used in the treatment of endophthalmitis. We injected 400 micrograms of amikacin into the vitreous cavity of rabbit eyes to study its pharmacokinetics. Phakic, aphakic, and aphakic vitrectomized eyes were injected, and inflamed eyes were compared to control eyes. Vitreous concentrations were determined at two, eight, 24, and 48 hours, and clearance rates were calculated. Amikacin is cleared considerably more quickly from aphakic (half-life, 14.3 hours) than phakic control eyes (half-life, 25.5 hours) and even more quickly from aphakic vitrectomized eyes (half-life, 7.0 hours). Inflammation substantially increased the rate of clearance in aphakic eyes. In inflamed aphakic and aphakic vitrectomized eyes, vitreous drug levels were equal to or below the minimal inhibitory concentration for most organisms considered sensitive to amikacin at 24 hours. Supplementation of intraocular antibiotics may therefore be required in clinical settings.

Amikacin↗
PubMed1993

Antimicrobial pharmacokinetics in endophthalmitis treatment: studies of ceftazidime.

Ceftazidime has pharmacokinetic advantages for treatment of endophthalmitis caused by gram negative-organisms by intravenous administration. Additionally, its spectrum of coverage for these organisms and its relatively low toxicity after intraocular injection are favorable attributes. These studies demonstrate that inflammation leads to a significant reduction of the blood-ocular barriers to ceftazidime. This increased permeability shortens the half-life of the drug after intraocular injection but allows a significant penetration into the eye after a single intravenous dose so that therapeutic levels are achieved. Ceftazidime appears to be removed by both the anterior and the posterior route without active transport. The experiments demonstrate the importance of the vitreous as a barrier to achieving significant concentration of antibiotic within the eye after intravenous administration and confirm the importance of the vitreous in prolonging the half-life of drugs injected intravitreally. Finally the results emphasize that the pharmacokinetic behavior of drugs for treatment of endophthalmitis must be assessed in inflamed eyes both with and without intact vitreous, since these factors play a large role in drug availability and concentration in the vitreous cavity and are the major variables in the clinical setting.

Animals↗
PubMed1992

Antitumour synergism between non-toxic dietary combinations of isotretinoin and glucarate.

Dietary calcium glucarate (CGT) increased the activity of non-toxic levels of dietary isotretinoin against pre-established tumors in the chemically-induced rat mammary tumour model. In the range of 1.0-1.5 mmol/kg diet, isotretinoin enhanced tumour growth by 20% over a 4 week course of treatment. Tumour growth inhibition not exceeding 15% was observed only at dosages as high as 2.0 mmol/kg, i.e. in the cumulative toxicity range. Growth inhibition by 64 mmol/kg diet of CGT alone was marginal, varying from zero to 8%. In contrast, the combination of 1.0 mmol/kg of isotretinoin and 64 mmol/kg of CGT caused a reversible inhibition of tumour growth, culminating in a net decrease in tumour volume of 20%. This study documents the marginal enhancement of tumour growth by high sub-optimal concentrations of isotretinoin alone, and describes conditions for inhibition of tumour growth by sub-optimal concentrations of the natural retinoid. Related in vitro studies on retinoid sensitive and insensitive cell lines suggest that the anticancer activity of the combination is dependent on sensitivity of the cells to retinoids.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Perforating (through-and-through) injuries of the globe. Surgical results with vitrectomy.

Fifty-one eyes of 48 patients with perforating (through-and-through) injuries of the globe were treated with vitrectomy during a 12-year period. Functional success was obtained in 32 eyes (63%), anatomic success was obtained in nine eyes (17%), and treatment failed in 10 eyes (20%). In 16 eyes (32%), 20/20 to 20/100 visual acuity was obtained; in 17 eyes (33%), 20/200 to 5/200 visual acuity was obtained; and in 18 eyes (35%), less than 5/200 visual acuity was obtained. The mechanism of injury was an important prognostic indicator of final visual outcome. Eight (62%) of 13 eyes that sustained knife or nail injuries achieved a final visual acuity of 20/50 or better, while only six (16%) of 38 eyes [corrected] with missile injuries achieved a similar level of acuity. Final visual outcome correlated well with the state of the macula and was not predicted by preoperative visual acuity. Despite improvement in surgical techniques and instrumentation, no trend toward improved visual outcomes was identified during the 12-year period.

Adolescent↗
PubMed1990

Complications of tissue plasminogen activator therapy after vitrectomy for diabetes.

Human recombinant tissue plasminogen activator (25 micrograms) was injected into seven eyes of six patients who had developed massive fibrin deposition after vitrectomy surgery for diabetes. Six eyes had developed pupillary membranes and recurrence of tractional retinal detachment from fibrin membranes, and one eye had developed only a pupillary membrane. All pupillary membranes resolved within one hour of administration of tissue plasminogen activator, and five tractional retinal detachments resolved within 24 hours. All eyes developed evidence of intraocular bleeding after tissue plasminogen activator injection. Subsequently, six of seven eyes developed recurrence of fibrin accumulation and tractional retinal detachment.

Adult↗
PubMed1990

Cefazolin levels after intravitreal injection. Effects of inflammation and surgery.

Cefazolin (2.25 mg) was injected into the vitreous cavity of phakic, aphakic, and aphakic/vitrectomized rabbits; inflamed eyes were compared to controls. Vitreous levels of cefazolin were determined at selected times from 2 to 48 hr, and the half-life was calculated. The effect of inflammation was to increase the half-life or to reduce the rate of elimination of cefazolin from the vitreous cavity. The drug was cleared substantially faster from aphakic/vitrectomized eyes than from phakic or aphakic eyes. Vitreous levels of cefazolin were above the MIC for most common gram-positive organisms causing endophthalmitis in all study groups at 24 hr, but in only the phakic inflamed eyes and in the aphakic eyes with intact vitreous at 48 hr.

Animals↗
PubMed1990

Retinal detachment in penetrating keratoplasty patients.

We reviewed the records of 23 patients who had retinal detachment after penetrating keratoplasty. Seventeen retinas (74%) were reattached successfully. Of the six failures, four patients had hemorrhagic choroidal detachment at the time of keratoplasty. When these complex retinal detachments are subtracted, 17 of 19 patients (89%) had successful retinal reattachments. Of the 17 successes, only seven patients had visual acuity of 20/200 or better. Retinal detachments after penetrating keratoplasty can be repaired with a high rate of success, but visual results remain disappointing.

Cataract Extraction↗