Biomedical subjects
R K Guerry
Publications and source records attributed to R K Guerry.
Toxoplasmic scleritis.
Although toxoplasmosis is the most common infectious cause of posterior intraocular inflammation, it is rarely described in association with scleritis. The authors present five cases of toxoplasmosis with scleritis. Two of the five cases were diagnosed clinically and serologically as having toxoplasmosis. Their retinochoroiditis and scleritis responded well to medical therapy. Retinochroiditis and scleritis that was refractory to treatment developed in the other three patients, two of whom had been receiving immunosuppressive therapy for systemic diseases. Their therapeutic regimens did not include treatment for toxoplasmosis. All three eyes became blind and were enucleated. Results of pathologic examination of all three enucleated eyes showed Toxoplasma gondii in the retina. There was severe inflammation of the retina, choroid, and sclera. Toxoplasmosis should be considered in the clinical differential diagnosis of scleritis associated with retinochoroiditis, particularly in immunosuppressed patients.
Basic mechanisms underlying the production of photochemical lesions in the mammalian retina.
Extended exposure (100s) of the macaque retina to blue light (400-500nm) produces a photochemical type or types of lesion. The basic mechanisms responsible for such photic damage are unknown but the toxic combination of light and oxygen leading to the free radicals O-.2, H2O2, OH., and O2(1 delta) have been suggested as a possible source of the phototoxicity. To test this hypothesis, the radiant exposure (J. cm-2) to short wavelength light (435-445nm) required for minimal damage in the macaque retina is under investigation as a function of oxygenation and after administration of substances known to either inhibit/scavenge radicals or act as anti-inflammatory/anti-oxidant agents. Substances under study include beta-carotene, steroids, catalase and SOD. Here we report radiant exposure in J.cm-2 needed to produce a minimal lesion vs oxygenation as measured by partial pressure of O2 in arterial blood (Po2). There is a sharp drop in the radiant exposure threshold with increase in the partial pressure of O2 in arterial blood, e.g. 30 J.cm-2 at 75 torr to 10 J.cm-2 at 271 torr, a factor of 3. Methylprednisolone injected intravenously one hour before exposure (125 mg) has been shown to raise the threshold for retinal damage in two macaques by a factor of approximately 2. Another animal fed beta-carotene (7.5 mg daily) over a period of 3 months has been exposed to blue light at several levels of oxygenation. The results suggest a protective effect.
Normal intraocular pressure during enucleation for choroidal melanoma.
A simple surgical technique for maintaining normal intraocular pressure during enucleation of eyes with a malignant melanoma of the choroid consists of making an incision into the anterior chamber through clear cornea with a microvitreo-retinal blade, followed by the introduction of a No. 21-gauge scalp vein needle or a No. 23-gauge sidewall-holed needle attached to a closed system filled with balanced salt solution. Measurements of pressure fluctuations during five enucleations are given. Such a system maintains the anterior chamber and keeps fluctuations in IOP to a minimum. This may be important in preventing hematogenous dissemination of tumor cells, resulting in metastatic disease.
Action spectrum for retinal injury from near-ultraviolet radiation in the aphakic monkey.
We found that the action spectrum for retinal damage (determined by the fundus photographic appearance of a minimal lesion immediately after exposure) extends into the near-ultraviolet by exposing three aphakic eyes from rhesus monkeys to 405-, 380-, 350-, and 320-nm wavelengths produced by a 2,500-W xenon lamp equipped with quartz optics and 10-nm interference filters. Exposure times were 100 and 1,000 seconds and the spot diameter on the retina was 500 micrometers. The retina was six times more sensitive to 350- and 325-nm wavelengths than to blue light (441 nm). Both ophthalmoscopic and histologic data showed that near-ultraviolet lesions differed in important respects from blue-light lesions. Near-ultraviolet produced irreparable damage to rod and cone photoreceptors.
Choroidal Osteoma.
Choroidal osteomas caused visual symptoms in four healthy young women. A positive 32P test led to enucleation and histopathologic confirmation of the diagnosis in one patient. The characteristic ophthalmoscopic findings in these patients included the following: (1) slightly and irregularly elevated, yellow-white, juxtapapillary, choroidal tumor and well-defined geographic borders; (2) diffuse and mottled depigmentation of the overlying pigment epithelium; and (3) multiple small vascular networks on the tumor surface. A diffuse mottled pattern of hyperfluorescence in the area of the tumor occurred during the early and later stages of angiography. The tumors were ultrasonically dense, and the orbital tissue behind them was rendered silent. The tumors were visible on routine orbital x-ray films and computerized tomograms. The latter study demonstrated the tumors as having the consistency of normal bone.
Diffuse unilateral subacute neuroretinitis.
Thirty-six young healthy patients developed a peculiar clinical syndrome affecting only one eye. The early stage of the disease was characterized by visual loss, vitritis, mild papilledema, and successive crops of multiple, evanescent, gray-white, deep, retinal lesions. Over a period of many months there developed widespread, diffuse and focal depigmentation of the pigment epithelium, retinal arterial narrowing, optic atrophy, severe visual loss, and electroretinographic changes. A motile, subretinal round worm, probably a Toxocara, was observed in two patients.
Paranasal sinus carcinoma causing orbital mucocele.
Three patients presented with typical orbital mucoceles. However, subsequent histopathologic study revealed paranasal sinus concomitant squamous cell carcinoma in all three cases. Careful histologic investigation is necessary before considering orbital mucocele a benign process.