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Biomedical subjects

T A Meredith

Publications and source records attributed to T A Meredith.

At least 55 records · Page 3Linked to original sources
PubMed1990

Vitreous cefazolin levels after intravenous injection. Effects of inflammation, repeated antibiotic doses, and surgery.

We devised a standardized rabbit model of intraocular inflammation using heat-killed Staphylococcus epidermidis as the inducing organism. We applied this model to study the effects of (1) inflammation, (2) repeated antibiotic doses, and (3) surgical status of the eye on cefazolin levels in the vitreous cavity after intravenous administration. Intravenous cefazolin sodium, 50 mg/kg, was administered every 8 hours for 48 hours. Eyes were harvested for assay of vitreous cavity antibiotic levels at various intervals from 1 to 49 hours. Drug levels were compared in inflamed and noninflamed eyes under both phakic and aphakic/vitrectomized conditions. At 1 hour, levels in phakic specimens were 3.0 mg/L in inflamed eyes vs undetectable in noninflamed eyes (P less than .01), but progressively increased to 10.6 mg/L at 49 hours (P less than .02) in inflamed eyes only. Levels in aphakic/vitrectomized eyes at 1 hour were 6.7 mg/L in inflamed eyes vs 4.2 mg/L in noninflamed eyes (P less than .1), but progressively increased to 24.9 mg/L at 49 hours (P less than .001) in inflamed eyes only. Levels at 49 hours in inflamed phakic and inflamed aphakic/vitrectomized eyes were well above the minimum inhibitory concentrations for organisms termed sensitive to cefazolin. We would conclude, therefore, that repeated doses of intravenous cefazolin may play an important adjunctive role in the treatment of endophthalmitis.

Analysis of Variance↗
PubMed1990

Comparative treatment of experimental Staphylococcus epidermidis endophthalmitis.

We created experimental Staphylococcus epidermidis endophthalmitis of moderate severity in the aphakic rabbit eye by injecting 100,000 organisms of a standardized laboratory strain (ATCC 155) into the mid-vitreous cavity. This model of endophthalmitis self-sterilizes in about 4 days, but inflammatory signs continue to increase 5 to 7 days after the initial bacterial inoculum. Control eyes were compared with eyes treated with five different strategies 24 hours after bacterial inoculation: intravitreal cefazolin sodium, intravitreal cefazolin plus intramuscular corticosteroid, vitrectomy plus intravitreal antibiotics, vitrectomy plus intravitreal antibiotics and intramuscular corticosteroids, and vitrectomy plus intravitreal antibiotics and corticosteroids. Quantitative grading of inflammation and media clarity were compared at the end of weeks 1, 2, and 3 after treatment. At week 1, eyes treated with vitrectomy had significantly lower inflammatory scores; those treated with corticosteroids had significantly lower scores than those without. The two effects were independent. The best results were observed with treatment consisting of vitrectomy, intraocular antibiotics, and corticosteroids. This strategy also produced significantly more eyes with clear media at the end of week 3 than treatment with intravitreal antibiotics alone.

Adrenal Cortex Hormones↗
PubMed1990

Profound central visual loss and ocular neovascularization in idiopathic recurrent branch retinal arterial occlusion.

The authors report a 65-year-old healthy, white man who experienced a dramatic loss of central vision. Iris neovascularization, rubeotic glaucoma, disc neovascularization and subhyaloid hemorrhage developed after multiple, recurrent, idiopathic branch retinal arterial occlusions. Vitreous and perivascular inflammation were prominent associated clinical features. Systemic steroids were useful in suppressing intraocular and perivascular inflammation, yet neither steroid nor anticoagulant therapy effectively prevented recurrent occlusive episodes. Retinal neovascularization and rubeotic glaucoma were successfully managed with scatter panretinal photocoagulation. Episodic intraocular inflammation and ocular neovascularization have been noted in one-third of patients sustaining recurrent idiopathic branch retinal arterial occlusions.

Aged↗
PubMed1990

Antibacterial effects of previously infected or inflamed vitreous.

The authors investigated the ability of vitreous harvested from eyes previously infected with Staphylococcus epidermidis or inflamed with heat-killed cells of the same organism to support subsequent in vitro bacterial growth. Growth of S. epidermidis and S. aureus was not supported by previously inflamed or previously infected vitreous, but Pseudomonas aerugnosa grew in all samples. These findings suggest induction of an antistaphylococcal substance by infection or inflammation of rabbit vitreous by S. epidermidis.

Animals↗
PubMed1990

Spontaneous sterilization in experimental Staphylococcus epidermidis endophthalmitis.

We created a standardized model of endophthalmitis in the aphakic rabbit eye using a laboratory strain of Staphylococcus epidermidis of known characteristics (ATCC 155). Eyes were injected with the following number of organisms: 170, 3760, 8750, 170,000 and 460,000. Serial quantitative cultures, clinical grading of infection and histopathologic studies were performed on days 1, 2, 3, 7 and 14. Bacteria appeared to multiply rapidly during the first 24 hr with peak recovery at 8 to 24 hr. Fewer bacteria were cultured on the third day after injection, and positive cultures were rare after the third day. Inflammatory scores were initially higher with each increased number of injected bacteria and tended to increase for the first 3 to 5 days.

Animals↗
PubMed1989

Vitrectomy when asteroid hyalosis prevents laser photocoagulation.

Asteroid hyalosis is a relatively common disorder of the vitreous that rarely causes visual impairment. However, funduscopic examination and laser photocoagulation can be difficult because of reflections off the asteroid bodies. Although vitrectomy is rarely indicated for impaired visual acuity, we report three cases in which pars plana vitrectomy was necessary to permit required retinal laser photocoagulation. In two patients with proliferative diabetic retinopathy and a third patient with subretinal neovascularization marked asteroid hyalosis precluded photocoagulation by standard techniques.

Aged↗
PubMed1988

Suppression of experimental tractional retinal detachment by low-dose radiation therapy.

We used a standardized model of traction retinal detachment (TRD) created by cellular membranes in the rabbit to test the effects of low-dose radiation therapy in suppressing TRD. The vitreous and lens were removed from pigmented rabbits, and homologous conjunctival fibroblasts were grown in cell culture. After resolution of postoperative inflammation, 50,000 fibroblasts in 0.1 mL of culture fluid were injected into the vitreous cavity. Ten eyes were maintained as controls. Nineteen eyes received 6 Gy (600 rad) of x-ray irradiation one to three hours after cellular injection. Eyes were monitored weekly for three weeks with indirect ophthalmoscopy. Seven (70%) of ten control eyes developed TRD at one week; no additional TRDs were noted at weeks 2 and 3. Significantly smaller numbers of irradiated eyes developed TRD: at week 1, two (11%) of 19; at week 2, five (28%) of 18; and at week 3, five (29%) of 17.

Animals↗
PubMed1988

Role of vitrectomy in Staphylococcus epidermidis endophthalmitis.

Seventeen patients with endophthalmitis due to coagulase-negative staphylococcus were treated over a nine-year period with vitrectomy, intraocular antibiotics, and systemic steroids and antibiotics. Fifteen patients presented with moderate to severe disease and visual acuities from counting fingers to light perception, while two had acuities of 20/60 and 20/200. A final visual outcome of 20/70 or better was achieved in 13 of 17 eyes (76%). Only one eye lost perception of light secondary to retinal detachment. Therapy including vitrectomy is an effective means of controlling moderate to severe coagulase-negative staphylococcal endophthalmitis and restoring vision.

Anti-Bacterial Agents↗
PubMed1987

Chronic bacterial endophthalmitis.

We studied a specific syndrome of uveitis secondary to intraocular bacterial pathogens of low virulence after extracapsular cataract extraction and intraocular lens implantation in three eyes. The onset of photophobia, visual impairment, conjunctival redness, and uveitis was delayed for four days to 12 weeks after surgery. Chronic inflammation persisted for five weeks to 16 months before a definitive diagnosis was made. Signs and symptoms were suppressed by administration of topical and systemic corticosteroids. Intraocular biopsy and antibiotic injection both established the cause as bacterial endophthalmitis and resulted in resolution of signs and symptoms. Staphylococcus epidermidis was cultured in two eyes and Achromobacter was cultured in one.

Adrenal Cortex Hormones↗
PubMed1987

Pars plana vitrectomy for severe penetrating injury with posterior segment involvement.

We studied 50 consecutive cases of severe penetrating ocular trauma with posterior segment involvement for which vitreous surgery and scleral buckling were performed as secondary reparative procedures. Eyes with a better prognosis, such as those with anterior segment injuries alone and intraocular foreign bodies, were excluded. Of 50 eyes, 31 (62%) had a successful outcome. There was a significant difference in visual outcome between those eyes that had received blunt and sharp penetrating trauma. Visual acuity of 20/50 or better was more frequently attained in eyes with sharp penetrating trauma (P = .002). Thirty-three eyes had initial retinal detachment; 17 (52%) were successfully repaired. Blunt penetrating trauma produced retinal detachment more frequently than sharp penetrating trauma (22 of 29 vs 11 of 21). Retinal detachment was more often successfully repaired after sharp penetrating trauma (8 of 11 vs 9 of 22). Contusive damage to the choroid and retina limited final visual and anatomic results after blunt rupture of the globe.

Ciliary Body↗
PubMed1987

Inherited retinal venous beading.

Four generations of a family with an unusual pattern of ocular vascular abnormalities were studied. Two male and three female members in two affected generations demonstrated prominent retinal venous segmental beading. Various individuals demonstrated areas of focal retinal infarction, surface retinal neovascularization, vitreous hemorrhage, microaneurysm formation, altered vascular permeability with lipid exudation, and focal edema. Several members demonstrated abnormalities of distribution of arterioles and venules. Saccular aneurysmal changes were present in conjunctival vessels. Renal disease was present in two affected individuals in the fourth and fifth decades, respectively.

Adolescent↗
PubMed1987

Secondary surgical management of expulsive choroidal hemorrhage.

Eight cases of expulsive hemorrhage with herniation of intraocular contents were managed with secondary procedures after initial operative closure of the eye. Two eyes with giant retinal tears and clear vitreous were treated with photocoagulation alone; each regained 20/200 visual acuity. Vitreous hemorrhage, traction retinal detachment, or rhegmatogenous retinal detachment was an indication for surgery in six eyes. Vitrectomy, choroidal drainage with simultaneous intraocular infusion, and scleral buckling restored useful vision in two eyes. In cases without vitreous hemorrhage or retinal detachment, conservative management may yield good results, while intraocular surgery may salvage useful vision in more complicated cases.

Adult↗
PubMed1985

Electroretinographic studies following vitrectomy and intraocular silicone oil injection.

Vitrectomy was performed bilaterally in pigmented rabbits and followed by silicone oil injection in one eye only. Electroretinographic studies were performed preoperatively and at selected postoperative intervals. In the early postoperative period both eyes showed an initial reduction in a and b wave amplitudes, followed by a return to baseline values. The amplitudes were symmetrically and equally affected. Sequential studies over a 20-month period showed no deterioration in electroretinographic response in eyes with and without silicone oil injection.

Animals↗
PubMed1984

Ocular involvement in primary hyperoxaluria.

Ocular involvement from primary hyperoxaluria developed in one infant and one teenaged patient. Autopsy procedures in the first case used special histopathologic staining techniques to demonstrate a wider deposition of calcium oxalate crystals within the eye than was previously suspected. Clinical photographs and fluorescein angiograms in the older patient demonstrated a widespread retinal distribution of crystals with a periarterial predilection. This patient also demonstrated a unique acquired black macular lesion.

Adolescent↗
PubMed1984

Ophthalmomyiasis interna causing visual loss.

Ophthalmomyiasis interna caused severe intraocular inflammation and loss of vision in two eyes. In the first eye, the organism was found in the vitreous and created a severe uveitis; a second-stage larva of Hypoderma lineatum was later removed from the anterior chamber. Phthisis bulbi ensued with loss of all vision. In a second eye, a subretinal maggot was observed to produce tracks in the pigment epithelium, with subretinal and vitreous hemorrhage. Severe uveitis and traction retinal detachment later developed. Despite successful reattachment of the retina, visual acuity remained only light perception. These cases demonstrate that ophthalmomyiasis interna is not always a benign condition.

Blindness↗
PubMed1983

Serous choroidal detachment after retinal detachment surgery.

In a prospective evaluation of 154 consecutive retinal detachment procedures, the incidence of choroidal detachment was 39.6%. The age of the patient, drainage of subretinal fluid, and vortex compression by the explant seem to be the most important correlative factors. Scleral explants up to one quadrant in circumferential length produced a minimal incidence (7.7%) of choroidal detachment. Posterior positioning of the explant also affected the incidence of choroidal detachment. After follow-up, ranging from six to 48 months, postoperative visual acuity was recorded for "macula-on" as well as "macula-off" retinal detachments. In the macula-on group, 78.6% of the patients with choroidal detachment retained a visual acuity of 20/50 or better compared with 82.8% of the patients without choroidal detachment. In the macula-off group, 43.2% of the patients with choroidal detachment achieved a visual acuity of 20/50 or better compared with 55.1% of the patients without choroidal detachment. The final anatomic success rate was 86.5% for eyes with choroidal detachment and 92.3% for eyes without choroidal detachment.

Age Factors↗