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Biomedical subjects

T R Friberg

Publications and source records attributed to T R Friberg.

At least 19 recordsLinked to original sources
PubMed1992

Prediction of visual recovery after scleral buckling of macula-off retinal detachments.

Patients with rhegmatogenous retinal detachments involving the fovea have visual loss that may not be recoverable despite anatomically successful surgery. Few guidelines exist to predict ultimate visual outcome with any certainty. We found that despite macular detachment, a device commonly used to predict visual acuity in cataractous eyes, the Potential Acuity Meter (Mentor O & O, Inc., Norwell, Massachusetts), provided acuity measurements even when Snellen visual acuity levels were poor or unmeasurable. In a study of 50 consecutive patients with clear media, we investigated a possible correlation between postoperative Snellen visual acuity with the preoperative Potential Acuity Meter results. We found that actual visual improvement correlated well with potential visual improvement as determined by Potential Acuity Meter measurements (R = .92). Preoperative assessment of patients with this device was a better predictor of final visual outcome than preoperative Snellen visual acuity, the extent of retinal detachment, or the duration of the retinal detachment by history.

Adult↗
PubMed1991

En bloc removal of inflammatory fibrocellular membranes from the iris surface in endophthalmitis.

Dense inflammatory fibrocellular membranes may develop over the iris in an eye with endophalmitis, completely obliterating any view of the posterior segment and hindering vitrectomy. To remove this debris, the edge of the membrane is first lifted from the surface of the iris with a small microvitreoretinal blade inserted through a limbal wound. The membrane is then engaged with an iris hook that is rotated until the debris is tightly wound on the shaft of the instrument. The iris hook is then removed from the anterior segment, delivering the inflammatory debris en bloc. This technique limits possible surgical trauma to the anterior segment and provides an excellent specimen for culture.

Endophthalmitis↗
PubMed1991

Tuberculin skin-test-induced uveitis in the absence of tuberculosis.

A 16-year-old Caucasian girl who showed no evidence of tuberculosis or other systemic disease developed acute panuveitis progressing to bilateral serous retinal detachments following purified protein derivative (PPD) skin testing on two separate occasions separated by an interval of 8 years. Both episodes responded rapidly to steroid therapy. Uveal hypersensitivity to PPD skin testing has been described in the presence of ocular or systemic tuberculosis, Eales' disease, and the Vogt-Koyanagi-Harada syndrome (VKH). Our case, however, suggests that profound uveitis may be precipitated by routine PPD skin testing alone.

Adolescent↗
PubMed1991

Reduction of severe macular edema in eyes with poor vision after panretinal photocoagulation for proliferative diabetic retinopathy.

Currently available data from multicenter randomized trials on laser treatment of diabetic macular edema refer only to eyes with pretreatment visual acuities of 20/160 or better. After observing reduction of more severe macular edema and visual improvement following panretinal photocoagulation (PRP) alone in some patients, we reviewed our experience with this problem. In 18 eyes of 14 patients with proliferative diabetic retinopathy and visual acuity of 20/200 or worse, secondary to severe macular edema were identified. At 6 months after PRP without focal macular laser treatment, macular edema was reduced in 13 eyes, 8 of which improved by greater than or equal to 2 lines of vision. Among the latter 8 eyes, the visual acuity of 4 recovered to 20/80 or better; the remaining 10 eyes, which had chronic retinal pigment epithelial atrophy or extensive macular ischemia, did not improve. Based on these observations, we suggest that peripheral PRP performed in multiple sessions over several months may have a beneficial effect on severe macular edema in some eyes with adequate macular perfusion.

Adult↗
PubMed1991

Effects of emulsification, purity, and fluorination of silicone oil on human retinal pigment epithelial cells.

When silicone oil is used as a vitreous substitute, reproliferation of vitreoretinal membranes beneath the oil occurs frequently. Nevertheless, the effects of various properties of silicone oils such as purity, viscosity, fluorination, or emulsification on cellular proliferation have not been established. Human retinal pigment epithelial (RPE) cells were grown to confluence on filters, and then covered with silicone oil. The cellular monolayers were fed from below. At 72 hr and 14 days a proliferation index was determined by measuring 3H-thymidine incorporation into the cells. An assay for the enzyme gamma-glutamyl-transpeptidase (gamma GTP) was also done to assess cell polarization under some oils. A total of 14 different oils were studied. At 72 hr, emulsified oil was associated with significantly less proliferation than unemulsified oil, a difference that disappeared at 2 weeks. Neither fluorination nor viscosity had a significant effect on RPE proliferation. In addition, RPE proliferation indices were not significantly different from one another when purified oils were compared with most commercial-grade oils. However, a very contaminated oil was associated with a significantly higher proliferation index compared with severe purified or medical-grade oils.

Cell Division↗
PubMed1990

Scleral buckling and ocular rigidity. Clinical ramifications.

Ocular rigidity is the change in intraocular pressure produced by an incremental change in intraocular volume. Ocular rigidity was determined in 14 donor eyes by injecting small increments of a balanced salt solution through the limbus, while continually monitoring the intraocular pressure with a transducer. A buckling procedure was then performed in these eyes with the use of various solid silicone or stainless steel encircling elements, and the experiments were repeated. Buckled eyes were significantly less rigid than unbuckled eyes, and eyes with higher buckles were significantly less rigid than those with shallower buckles. The observed changes in rigidity are likely secondary to changes in the shape and stress distribution of the scleral shell and are only to a small degree related to the elasticity of the encircling element. Greater volumes of vitreous substitutes, gases, or antibiotics may be injected into buckled eyes compared with unbuckled eyes before excessive intraocular pressures are reached.

Acetates↗
PubMed1990

Serous retinal detachment resembling central serous chorioretinopathy following organ transplantation.

Two patients developed unilateral serous retinal detachments of the macula resembling idiopathic center serous chorioretinopathy within 9 months of cardiac transplantation, while one renal transplant recipient developed bilateral serous detachments within 6 months of surgery. In two cases (three eyes), dense, yellow, fibrlin-like exudates were present in the subretinal fluid. At the time of presentation, each of the three patients had a modest elevation of blood urea nitrogen. Laser photocoagulation was performed in three eyes with limited success, although ultimately the detachments resolved leaving only mild visual impairment (6/9 vision). The differential diagnosis of visual loss in the transplant population includes serous detachment of the sensory retina as well as more serious chorioretinal infections related to immunosuppression.

Choroid Diseases↗
PubMed1990

Effects of silicone oil and hyaluronic acid on cultured human retinal pigment epithelium.

An experimental model was developed to evaluate the effects of several vitreous substitutes on human retinal pigment epithelial (RPE) cells. Cultured RPE cells were grown into confluent monolayers on semipermeable membranes and nourished from the basal side only, while the apical surface was directly and continuously exposed to preparations of hyaluronic acid and silicone oil for up to 4 weeks. In the silicone oil-treated group, multilayer sheets formed within 2 weeks of exposure and incorporation of 3H-thymidine was twice that of controls. Exposure of RPE cells to silicone oil and certain preparations of hyaluronic acid resulted in a three- to fourfold decrease in cellular polarity, as measured by assaying the cell-surface enzyme, gamma-glutamyl transpeptidase. These results suggest that a model using cultured RPE-cell monolayers is useful in identifying and understanding alterations in ocular tissues triggered by exposure to vitreous replacement materials.

Cell Division↗
PubMed1989

Contrast sensitivity versus static visual field testing during experimental elevation of intraocular pressure.

Contrast sensitivity testing has been recommended as a more sensitive indicator of early visual loss than visual field testing. Using gravity inversion to induce an intraocular pressure rise, we performed contrast sensitivity testing on each eye of 10 normal subjects in the upright and inverted positions. Contrast sensitivity results were not altered in the head-down position, even though in 5 of the 10 subjects (7 of 20 eyes), visual field alterations on static perimetry were elicited during inversion. In both of these evaluations, the subject's results in the upright position served as the control, freeing us from reliance upon age-matched populations. We conclude that precise measurement of static thresholds with automated perimetry is more sensitive than routine contrast sensitivity testing in detecting visual dysfunction related to transient acute elevations of intraocular pressure.

Adult↗
PubMed1989

Central serous chorioretinopathy: an analysis of the clinical morphology using image-processing techniques.

We used a digital image processor to make multiple measurements from the fluorescein angiograms of 53 cases of central serous chorioretinopathy (CSC) associated with single leaks. We determined the area of the base of each serous detachment, the location of its geometric center (CM), the area of the RPE leak, the distance from the fovea to the leak, and the distance from the leak to the CM. The distribution of leaks across the base of the detachments was nonrandom (P less than 0.005) with leaks clustering near the centers of the detachments. When the leak was found within 1 disc diameter from the fovea, the center of the detachment was located virtually at the foveola, suggesting that the central macula is predisposed to the development of CSC. Detachments associated with "smokestack" leaks were significantly larger than those associated with round pinpoint leaks (P less than 0.02).

Adult↗
PubMed1989

The etiology of choroidal folds. A biomechanical explanation.

Folding of the choroid, Bruch's membrane, and the overlying retina occurs in a variety of ocular and orbital diseases and after certain surgical procedures. The etiology of the folding is explained, using the principles of deformation of materials and by considering the biomechanical properties of the choroid and sclera. Choroidal folds are likely to develop in association with any intra- or extraocular process that induces sufficient compressive stress within the choroid, Bruch's membrane, and retina to force these tissues to buckle. A detailed explanation of the pathogenesis of folding is presented in various clinical settings.

Biomechanical Phenomena↗