Biomedical subjects
Publications and source records attributed to T A Meredith.
Two cases of large, posteriorly located epiretinal neovascular membranes are presented that were associated with a nasal wedge of retinal ischemia of unknown cause in young Caucasian men without associated systemic disease. A technique of staged, argon laser scatter photocoagulation to the ischemic retina resulted in dramatic regression of the neovascular fronds in both cases.
Retinal pigment epithelial detachment and optic disk neovascularization developed in two men, 51 and 49 years old, who had serpiginous choroiditis. Fluorescein angiograms demonstrated loss of pigment epithelium and choriocapillaris in the late stages in both cases. Both men sustained permanent visual loss. In one case the final visual acuity of the affected eye was 20/200. In the second case the final visual acuity was R.E.: counting fingers at 4 feet and L.E.: 20/70.
In 14 eyes undergoing a pars plana filtration procedure combined with pars plana lensectomy and vitrectomy, the most common complication was a severe sterile fibrinous vitritis. However, after a mean follow-up period of 6.3 months, intraocular pressure was controlled in five eyes (36%) after the procedure alone, in two (14%) after subsequent medical therapy, and in three (21%) after subsequent cyclocryotherapy. Preoperative visual acuity was maintained or improved in nine of the eyes (64%), whereas four eyes (28%) had no light perception.
Systemic and orbital reticulum cell sarcomas (RCSs) have been shown to be derived from lymphocytes, not reticulum cells or histiocytes, by immunologic and cytochemical characterization. Unfortunately, until now it has not been technically possible to study intraocular RCS. We have been able to immunologically characterize a primary intraocular RCS in a patient with chronic lymphocytic leukemia (ie, Richter's syndrome), establishing its origin from B lymphocytes. A review of the clinical course of such tumors indicates that primary intraocular non-Hodgkin's lymphoma is usually a manifestation of a systemic neoplasm of the immune system.
We used a technique for surgical management of fibrovascular membranes to relieve epiretinal tangential traction when present in proliferative diabetic retinopathy. Sharp dissection with intraocular scissors was used to segment fibrovascular and cortical vitreous membranes together with cauterization of large vessels with intraocular bipolar diathermy. The objective of membrane segmentation was to relieve all epiretinal traction, thereby reducing retinal surface distortion and allowing the retina to flatten and reattach. Complete relief of traction prevented further late contraction of membranes and subsequent distortion and redetachment.
Patients with presumed ocular histoplasmosis syndrome were typed for HLA-A, B, C, and DR antigens. It was found that 21 (81%) of 26 of the presumed ocular histoplasmosis syndrome patients with disciform macular scarring and 8 (62%) of 13 of the presumed ocular histoplasmosis syndrome patients with peripheral atrophic spots typed for DRw2. The frequency of DRw2 in normal blood donors was 28%. The 77% (20 patients) frequency of B7 in 26 of the presumed ocular histoplasmosis syndrome patients with disciform scarring was also significantly higher than the 25.6% frequency of B7 in normal blood donors. In contrast, no significant differences were observed in any HLA antigen frequency for patients with disciform scarring of degenerative choroidopathy. These observations suggest that an association with DRw2 may play a role in the pathogenesis of the eye lesions after Histoplasma capsulatum infection.
One hundred eyes in 98 patients were studied by fluorescein angiography and stereo color photography six weeks after successful scleral buckling surgery. Twenty-five percent of 67 phakic eyes and 40% of 33 aphakic eyes demonstrated cystoid macular edema. Older phakic patients were at significantly greater risk to develop cystoid macular edema than younger phakic patients. Seventeen percent of successfully repaired eyes demonstrated distortion of the macula by preretinal membranes; 16 of these 17 eyes showed leakage of fluorescein dye into the surrounding retina sometimes also causing cystoid edema. Either cystoid macular edema or macular distortion was present in 38% of the phakic eyes and 64% of the phakic eyes after successful retinal detachment surgery.
Six eyes in four patients with cytomegalovirus retinitis developed retinal holes and retinal detachment. Holes appeared in areas of necrosis and were typically large and round with shaggy edges. Differentiation from exudative detachment was sometimes difficult because of obscuration of the fundus by vitreous haze. Cryotherapy was successful in closing open breaks without detachment; cryotherapy and exoplant surgery were used effectively to treat the initial detachments. The occurrence of massive periretinal proliferation and late development of new areas of hole formation or retinitis complicated therapy for these detachments.
Fifty eyes of 40 patients with serous (avascular) detachments of the retinal pigment epithelium were followed up for an average of 22 months. Of the 50 eyes, 14 (28%) developed bleeding beneath the retinal pigment epithelium and retina or subretinal neovascularization detected on fluorescein angiography. These changes did not occur in eyes of patients younger than age 56 years at diagnosis or in detachments less than 1 disk diameter in size, whereas 35.9% (14) of eyes in patients older than age 56 years developed vascular complications. Vascular complications were uncommon when the initial detachment did not involve the fovea. Visual acuity declined in only one (9.1%) of eyes in patients younger than age 56 years but in 20 (51.3%) of eyes in patients age 56 years or greater.
A comprehensive review of 1,000 cases of intracapsular cataract extraction in the hands of a single surgeon was undertaken. Eyes with identifiable pathology in addition to cataract noted prior to surgery have an increased incidence of complications. Eyes operated at a younger age have an increased incidence of inadvertent extracapsular extraction, vitreous loss, flat anterior chamber, conjunctival bleb formation, and retinal detachment. Adoption of cryosurgery for lens removal reduced the incidence of inadvertent extracapsular extraction in eyes predisposed to complication. The use of monofilament nylon suture in a continuous closure reduced the incidence of bleb formation and eliminated the necessity for re-operation for complications of wound closure.
A review of 1,000 cases of intracapsular cataract extraction revealed that in eyes in which no factor predisposed to complication, the early visual results were equal to or better than 20/40 in 97% of the cases. Complications of surgery in this group accounted for decreased visual acuity in only 1.7% of the eyes. In the group of patients with high myopia, previous surgery, known corneal disease, or some other factor thought to predispose to a complication, the visual acuity was equal to or better than 20/40 in only 74% of the cases, most of the decrease being due to preexisting factors within the eye rather than complications themselves. In the first group, the total amount of astigmatism produced by all the suturing techniques reviewed was similar. With interrupted suturing techniques, the axis of the correcting cylinder was more often against the rule while continuous closures with monofilament nylon more frequently produced with the rule astigmatism.
A distinctive appearance of the ocular fundus as a late complication of high doses of orally administered thioridazine hydrochloride (Mellaril) is described. Discrete nummular areas of loss of retinal pigment epithelium (RPE) extended from the posterior pole to the midperiphery. Fluorescein angiography demonstrated loss of choriocapillaris in these zones. Atrophy of the remaining RPE was progressive, with advancement of the edges of the atrophic zones and breakdown of bridges of RPE separating them. Atrophy occurred after discontinuation of the drug and advanced without further exposure to it. Dark adaptation, the electroretinogram, and the electro-oculogram were abnormal in the late stages. Central visual acuity remained relatively good.
Patients identified in the Walkersville, Maryland, epidemiologic study of presumed ocular histoplasmosis as having only peripheral atrophic scars showed no increase in frequency of HLA-B7 over a control population. Because this antigen is increased in patients with a history of active macular or peripapillary lesions, these findings indicate an inherent predisposition in some patients to develop posterior pole lesions after an ocular infection with Histoplasma capsulatum. The precise mechanisms by which the histocompatibility complex participates in the pathogenesis of these lesions is unknown, but our data are compatible with previous suggestions that alterations in the immune response of these individuals are in some way important in the development of disciform scarring in the posterior pole.
Eighteen patients with the presumed ocular histoplasmosis syndrome were typed for HLA histocompatability antigens and 78% were found to have the B7 antigen. This data implies an underlying immunogenic predisposition to the development of the clinical eye findings and active posterior pole lesions in the presumed ocular histoplasmosis syndrome. It is likely that some feature of the immune system of these patients renders them more susceptible either to the initial infection or to a later activation of posterior pole lesions mediated through immunologic mechanisms.
Eight eyes of five patients with hemorrhagic peripapillary histoplasmosis demonstrated prolonged symptomatic periods and recurrent bleeding episodes, although final visual acuity was equal to or better than 6/12 (20/40) in five eyes (63%). Fluorescein angiography demonstrated new subretinal neovascular growth at the margins of atrophic scars. In the late stages additional retinal pigment epithelium was lost and a white subretinal mass developed adjacent to the atrophic zone. Argon laser photocoagulation was used in two cases to destroy this neovascular tissue, but caused a permanent arcuate defect in one.
Four patients with toxoplasmosis are reported with unusual presenting ocular lesions. One patient had an active lesion that appeared to involve the optic nerve as well as focal toxoplasmosis chorioretinitis at the macula. A second patient had a pale optic nerve in association with the classical chorioretinal scars of toxoplasmosis. The third patient had toxoplasmosis chorioretinitis of the macula with subretinal neovascularisation. The fourth patient had a branch artery occlusion complicating acute retinitis.
Perifoveal capillary leakage of fluorescein was demonstrated in 60 per cent of 50 eyes when angiography was performed two weeks after cataract extraction. Repeat angiography six weeks postoperatively in 17 eyes demonstrated persistence of already established leakage in 11 of 12 eyes and no new leakage in five eyes previously negative. Cystoid macular oedema with visual acuity of less than 20/40 six weeks postoperatively occurred in five eyes (10 per cent). Eyes of patients with vascular disease and those patients of 60 years or older were found to have altered vascular permeability significantly more frequently. Inflammation was no more severe or prevalent in those patients who demonstrated leakage and no inflammation was clinically apparent in 10 of 11 eyes demonstrating dye leakage six weeks postoperatively. We conclude that the constitutional factors of age and vascular disease are of prime importance in causing altered vascular permeability in the early postoperative period after cataract extraction; factors causing sustained leakage with reduction of visual acuity were not demonstrated.
The eyes of three patients followed clinically for many years with a diagnosis of macular disciform scarring, secondary to ocular histoplasmosis, were studied histopathologically. A fibrovascular scar interposed between the choroid and retina was observed in all cases. Vessels passing from the choroid through defects in Bruch's membrane into the nodule were demonstrated. Theories of the pathogenesis of the lesion are discussed.