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Biomedical subjects

T R Friberg

Publications and source records attributed to T R Friberg.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1989

Bilateral optic disc colobomas with orbital cysts and hypoplastic optic nerves and chiasm.

A 3-month-old boy with bilateral optic disc colobomas and orbital cysts is presented. Both eyes appeared relatively normal in size. Ultrasonography on one side demonstrated a communication between the globe and cyst by way of the optic disc coloboma. On computed tomography and magnetic resonance imaging, the cysts' contents were similar to vitreous. The optic nerves and chiasm appeared markedly hypoplastic on neuroimaging tests. Fluorescein angiography, electroretinography, and visual evoked responses suggested that the visual deficit primarily was ascribable to optic nerve or anterior visual pathway dysfunction.

Coloboma↗
PubMed1988

A comparison of the elastic properties of human choroid and sclera.

Multiple strips of choroid (56) and sclera (64) from eight pairs of human eye-bank eyes were subjected to simple tension in a test apparatus to determine the rigidity (modulus of elasticity) of these tissues. The modulus of elasticity of the chorodial complex (choroid-Bruch's membrane-pigment epithelium) was significantly greater in posteriorly located samples than in anteriorly located ones (7.5 +/- 7.0 vs. 2.2 +/- 1.5 x 10(5) N m-2, mean +/- S.D.). The modulus of elasticity for the complex averaged across all locations was 6.0 +/- 2.8 x 10(5) N m-2 and the average stress at failure was 3.3 +/- 1.3 x 10(5) N m-2. The modulus of elasticity for scleral strips also varied with location and averaged 2.9 +/- 1.4 x 10(6) N m-2 for anterior sclera and 1.8 +/- 1.1 x 10(6) N m-2 for posterior sclera at stress levels ranging from 20- to 260 x 10(4) N m-2. There was a significant correlation of scleral stiffness with age (P less than 0.05, r = 0.80). The elastic properties of the choroidal complex may be relevant to the pathogenesis of a variety of ocular diseases, including macular degeneration, angioid streaks, choroidal folds, and choroidal ruptures.

Adolescent↗
PubMed1988

Aspergillus flavus endophthalmitis and retinitis in an intravenous drug abuser. A therapeutic success.

Endogenous Aspergillus flavus endophthalmitis with layering of inflammatory cells in the subretinal space and vitreous infiltration developed in a 35-year-old female intravenous drug abuser. The patient underwent a diagnostic and therapeutic vitrectomy within 48 hours of presentation, receiving intravitreal amphotericin B. Intravenous amphotericin also was administered several days later. Despite extensive retinal and vitreous involvement, the patient recovered useful vision because of the aggressive diagnostic and therapeutic approach.

Adult↗
PubMed1988

Pneumatic repair of primary and secondary retinal detachments using a binocular indirect ophthalmoscope laser delivery system.

Using intravitreal gas injection of sulfur hexafluoride after retinopexy utilizing a binocular indirect ophthalmoscope argon laser delivery system, the authors treated 12 primary rhegmatogenous retinal detachments and 10 detachments which recurred after previous scleral buckle surgery. Topical anesthesia only was used in most of the cases (18 of 22). Detachments in all quadrants of the fundus were repaired. Twenty cases remained successfully attached after a minimum follow-up of 6 months. Two failures occurred early in eyes with primary retinal detachments and both were successfully repaired by conventional scleral buckling techniques. The authors found pneumatic retinal reattachment in conjunction with laser retinopexy to be particularly valuable in repairing secondary detachments, thereby avoiding conventional surgical reoperations.

Cryosurgery↗
PubMed1987

Intraocular and episcleral venous pressure increase during inverted posture.

We measured intraocular and episcleral venous pressure in 11 subjects in both the supine and the head-down vertical position. Gonioscopy was performed in eight subjects. The intraocular pressure changes were correlated with the alterations in episcleral venous pressure using linear regression analysis. We found that for each 0.83 +/- 0.21 mm Hg increase in episcleral venous pressure there was a rise of 1 mm Hg in intraocular pressure (r = .80, P = .003). Upon inversion, blood appeared in Schlemm's canal in half of the eyes studied with gonioscopy, suggesting that it refluxed into the canal from increased episcleral venous pressure. The mechanism of a sustained intraocular pressure rise during gravity inversion appears to be closely related to increased venous pressure in the orbit.

Adult↗
PubMed1987

Optic nerve dysfunction during gravity inversion. Visual field abnormalities.

Inversion in a head-down position (gravity inversion) results in an intraocular pressure of 35 to 40 mm Hg in normal subjects. We used computerized static perimetry to measure the visual fields of normal subjects during gravity inversion. There were no visual field changes in the central 6 degrees of the visual field compared with the baseline (preinversion) values. However, when the central 30 degrees of the visual field was tested, reversible visual field defects were found in 11 of 19 eyes. We believe that the substantial elevation of intraocular pressure during gravity inversion may pose potential risks to the eyes, and we recommend that inversion for extended periods of time be avoided.

Adult↗
PubMed1987

Use of directly acquired digital fundus and fluorescein angiographic images in the diagnosis of retinal disease.

Direct on-line acquisition of digital fundus and fluorescein images is a useful alternative to conventional fundus photography. Immediately after acquisition, digital images may be electronically reassembled, manipulated, and displayed, avoiding the delays inherent in film development. Digital fundus images, conventional photographs, and fluorescein angiograms were obtained at the same sitting in 50 consecutive patients with retinal disease. Digital studies were displayed on a video monitor and diagnoses were made directly from the screen. The interpretations based on digital images alone were virtually identical to those made from photographs, although the resolution of digital images was not equal to that of the photographic images. Despite this disadvantage, the system proved extremely versatile, and for this reason, digital image acquisition was used to routinely document the retinal findings in the majority of the clinical patients.

Fluorescein Angiography↗
PubMed1987

Clinical experience with a binocular indirect ophthalmoscope laser delivery system.

A binocular indirect ophthalmoscope argon laser delivery system was used to treat 100 selected patients with a variety of retinal disorders. The laser was found to be particularly valuable in photocoagulating the retinal periphery, because scleral depression could easily be performed simultaneously. Furthermore, laser treatment was facilitated in eyes that dilated poorly, such as those with rubeosis iridis, and eyes with focal lens opacities requiring panretinal photocoagulation. Infirm or anesthetized patients who could not sit at a slit lamp could also be treated. Disadvantages included difficulty in accurately aiming the laser beam and instabilities inherent in the system that make it unsuitable for the treatment of macular diseases.

Equipment Design↗
PubMed1987

Retinal microaneurysm counts in diabetic retinopathy: colour photography versus fluorescein angiography.

Microaneurysms were counted separately in a masked manner on stereo colour fundus photographs and on stereo fluorescein angiograms of 100 patients with unselected forms of diabetic retinopathy. Serial studies obtained 6 months apart were available for most patients, and a total of 315 separate photographic studies were evaluated. In addition, 118 photographic studies of 38 young patients with type I diabetes mellitus were evaluated. About twice as many microaneurysms were detected on the fluorescein angiograms as on the colour photographs for both groups of patients (p less than 0.05). Fluorescein angiography showed microaneurysms in 57% of the eyes in the second group photographed for the first time that had no detectable microaneurysms on colour photography. The use of fluorescein angiography is recommended in diabetic patients when detection of subtle microvascular abnormalities is deemed essential.

Aneurysm↗
PubMed1987

Idiopathic central serous retinopathy in China: a report of 600 cases (624 eyes) treated by acupuncture.

Six hundred Chinese patients (624 eyes) with clinically diagnosed central serous retinopathy were treated by consecutive courses of acupuncture. Eighty-six percent of patients had resolution of their subretinal fluid within 3 months of treatment, a result similar to the natural history of the disease as reported by others in non-Chinese patients. Central serous retinopathy was most common in the 30 to 50 year age group, occurred in males seven times more frequently than in females, and was bilateral in 4% of patients.

Acupuncture Therapy↗
PubMed1986

Incidence of ocular abnormalities in patients with sickle hemoglobinopathies.

We examined 110 consecutive unselected patients with SS, SC, or Sthal sickle hemoglobinopathies to determine the prevalence of various retinal lesions within each group. The most prevalent retinal abnormality was the black sunburst, occurring in 46% of SS patients, 63% of SC patients, and 37% of Sthal patients. Our data also suggest that retinal lesions become more prevalent up to the fifth decade of life. Included in our series was an eight-year-old SS hemoglobin patient who presented with a dense vitreous hemorrhage secondary to a large salmon patch that had bled into the vitreous, reducing her vision to 20/200.

Adolescent↗