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Biomedical subjects

R D Richards

Publications and source records attributed to R D Richards.

At least 37 records · Page 2Linked to original sources
PubMed1984

Polyol pathway metabolites in human cataracts. Correlation of circulating glycosylated hemoglobin content and fasting blood glucose levels.

Circulating glycosylated hemoglobin (Hb A1) and/or fasting blood glucose (FBG) levels, measures of the extent to which diabetes is clinically controlled, were correlated with the contents of fructose, sorbitol, glucose, and inositol in 27 cataracts removed by intracapsular extraction. In the series of patients studied, Hb A1 levels ranged from 6.0% to 15.5% of the total hemoglobin value. The levels of fructose and sorbitol (micromoles per gram of lens) in their cataracts ranged from 0 to 8.4 and 0 to 10.2 mumole/g, respectively, with correlation coefficients greater than .8. Similar correlations were noted with FBG. The Hb A1 correlated with lens glucose (r = .58) and not with inositol. However, FBG had no correlation with either lens glucose or inositol. The observed correlation of the polyol pathway metabolites with both Hb A1 and FBG suggests that the lens can synthesize substantial quantities of sorbitol and fructose in response to the excess glucose available to lenses of human diabetics. A synergistic role of the polyol pathway in the cause of senile cataracts is thus possible.

Blood Glucose↗
PubMed1984

Histoplasma capsulatum in the eye.

The ocular pathologic findings in an immunosuppressed patient who died of disseminated histoplasmosis are described. Histoplasma capsulatum was found in large numbers within the endothelial cells of the choroid, in one area each of the ciliary body and trabecular meshwork. There was a minimal inflammatory response. No granulomas were noted. Previously reported cases of ocular histoplasmosis in immunosuppressed patients are similar in that, with one exception, granulomatous inflammation was not demonstrated. Thirteen eyes in which histoplasma organisms have been found in the eye are reviewed.

Adult↗
PubMed1984

Oxidative stress on lens and cataract formation: role of light and oxygen.

The mechanism of oxidative damage to the lens through intraocular photochemical generation of superoxide and its derivatization to other oxidants such as singlet oxygen, hydroxyl radical and hydrogen peroxide has been studied. Rat lenses when organ cultured aerobically in TC 199 containing additional amounts of riboflavin were damaged as demonstrated by an inhibition of the uptake of Rb 86 against a concentration gradient. The pump was not affected by light if the culture was conducted in the basal TC 199. However, light was observed to induce significant peroxidative degradation of the tissue lipids even in the basal medium, the degradation being indicated by the formation of malonaldehyde. Both the inhibition of the pump as well as the peroxidative degradation of the tissue lipids, were attenuated considerably by scavengers of superoxide and hydrogen peroxide. In addition, the lipid degradation was prevented by vitamins C and E. The results suggest that the photodynamic injury to the lens cation pump as well as to membrane lipids is incumbent upon an initial generation of superoxide and its derivatization to other oxidants. Thus, the ocular lens is susceptible to oxidative insult and physiological damage through photocatalytic generation of various oxygen radicals. Large concentrations of ascorbic acid in the aqueous humor seems to be able to provide significant protection against such an insult. Thus, this may be one of the functions of high concentration of ascorbic acid in the aqueous humor. The implication of oxidative stress has also been examined in the genesis of cataracts in vivo. Treatment with vitamin E of the Emory mouse led to a decrease in the rate of cataract progression suggesting that at least in some instances an oxidative stress could participate in the formation of cataracts. Oxygen radicals may inflict damage at multifarious biochemical sites. Human lens lipids were also shown to have an absorption maxima at 239 nm indicating their susceptibility to oxidative degradation. In addition the lipid extract has fluorescence similar to that of lipofuscins. The levels of MDA were higher in the brunescent cataracts as compared to that in the nonbrunescent cataracts. The implications of oxidative stress towards the genesis of cataracts in humans is being explored further.

Animals↗
PubMed1983

Complications of exposed monofilament sutures.

Exposed monofilament suture ends caused a variety of symptoms and signs in 18 patients. These included foreign-body sensation, pain, contact lens intolerance, giant papillary conjunctivitis, tarsal ulceration, conjunctival granuloma, corneal infiltrate, and corneal vascularization. These changes followed cataract surgery, corneal transplantation, and pars plana vitrectomy. Diagnoses in these cases were made by careful slit-lamp examination and by eversion of the upper eyelid. In every case, removal of the sutures or trimming the suture ends resulted in the immediate relief of all symptoms with complete resolution of all signs within two months.

Adult↗
PubMed1983

Sugar cataracts in Mongolian gerbil (Meriones unguiculatus).

Mongolian gerbils (Meriones unguiculatus) given a 50% galactose diet developed cataracts similar to those produced in rats maintained on the same diet. This report describes the various stages through which the cataracts progressed. The first sign of a cataract appeared 24 hr after feeding gerbils on the high galactose diet. The pace of cataract maturation was observed to be about twice of that in rats, although the blood galactose levels were similar in the two species. Aldose reductase activity in the gerbil lens was also about twice of that in the rat lens. In conformity with this, dulcitol accumulated to a higher level in gerbil lens during the early phase of cataractogenesis. The data are, therefore, in accordance with the concept that excessive accumulation of polyol in the lens initiates cataract development. The gerbil thus appears to be another suitable model for the study of sugar cataracts.

Aldehyde Reductase↗
PubMed1983

Ongoing prospective clinical study of radial keratotomy.

The ongoing prospective clinical study of radial keratotomy at the University of Maryland now includes 58 eyes of 33 patients. Fifty-two eyes underwent a single operation, whereas six eyes underwent two operations. Follow-up was a minimum of six months and a mean of 19 months. Preoperative vision was 20/400 or less in 74% of eyes. Postoperative vision was 20/40 or better in 48% of eyes. There was an average myopia decrease of 2.70 diopters and an average corneal flattening of 1.51 diopters. Patients with preoperative refractive errors of 5 diopters or less achieved 20/40 or better vision in 65% of eyes, as compared to only 19% in eyes with preoperative refractive errors greater than 5 diopters. This is highly significant (P less than 0.005). There was no difference in the results achieved by our first 33 eyes when compared to our second 25 eyes. The decrease in myopia did not correlate with corneal curvature, or whether 8 or 16 incisions had been used. No microperforations were seen and only one case of endothelial cell loss was observed. Glare and fluctuating vision was not a significant problem in our series.

Adolescent↗
PubMed1983

X-ray effects on lens DNA-implications of superoxide (O(2)).

The photochemical generation of superoxide (O(2)) during in vitro exposure of bovine lenses induced damage in the structure of lens DNA as indicated by hyperchromicity and Tm measurements. The damage in lens DNA was significantly protected by the inclusion of superoxide dismutase (SOD), glutathione (GSH) and ascorbate in the incubation medium before X-ray exposure. The protection by SOD, GSH and ascorbate occurred due to their interaction with O(2) radicals. These results thus indicate the deleterious effect of O(2) in lens physiology and the protective role of such compounds against radiation damage.

Animals↗
PubMed1983

Central cornea involvement in Terrien's degeneration.

A 15-year-old female showed classical signs of Terrien's corneal degeneration including peripheral corneal thinning, vascularization, lipid deposition, and ectasia. She also showed episodes of conjunctival inflammation and perforation following minor trauma, all in the presence of an intact epithelium. She also showed progressive central corneal thinning and opacification, features not reported in the literature in the last 30 years.

Adolescent↗
PubMed1982

Photocoagulation-induced lens opacity.

Lens opacities secondary to argon laser photocoagulation were seen in six eyes of four patients undergoing treatment for subretinal neovascular membrane and diabetic retinopathy. Laser-induced lens opacities were multiple, grayish-white, and localized at the junction of the nucleus and anterior cortex of the lens. These lens opacities were stable and nonprogressive. Laser-induced lens opacities are a potential complication of photocoagulation treatment in patients with nuclear sclerosis.

Aged↗
PubMed1982

Anterior chamber tube shunt to an encircling band in the treatment of neovascular glaucoma.

A new procedure for neovascular glaucoma that has reduced intraocular pressure (IOP) significantly and has caused relatively few postoperative complications is introduced. Aqueous is shunted to the reservoir of an encircling no. 20 silicone band from which fluid is postulated to diffuse into the orbit. The anterior chamber tube shunt to an encircling band (ACTSEB) procedure was conducted in 19 eyes with neovascular glaucoma. After surgery 18 of the 19 eyes (95%) followed for periods ranging between five and 26 months (mean: 59 weeks) had controlled IOP using less than or equal to 20 mm Hg as normal, and one eye had partial control (eye 9) at 26 mm Hg. Despite the preoperative use of atropine sulfate, timolol maleate, acetazolamide, and 20% mannitol, the patients' average preoperative IOP was 54.1 mm Hg. After surgery the average IOP fell, dramatically, to 16.2 mm Hg. The mean change in IOP was 37.9 +/- 9.8 (SD). This change is statistically significant by the paired t-test, P less than 0.01. Minimal postoperative medications were required for pressure control. Postoperative complications included hyphema (21%), prolonged flat chamber (74%), localized peripheral lens opacity (5%), localized corneal opacity (5%), and possible acceleration of progressive cataract formation (25%). Results of current surgical procedures used to manage neovascular glaucoma are compared to the ACTSEB results.

Adult↗
PubMed1982

Prospective clinical study of radial keratotomy.

A prospective clinical study of radial keratotomy was conducted at the University of Maryland. Results of surgery on 33 eyes of 19 patients with a minimum follow-up of seven months and a mean of 13.8 months are reported. There were eight patients (15 eyes) who needed adequate unaided visual acuity for occupational purposes. Preoperative visual acuity was 20/400 in 79% of eyes. Postoperative visual acuity was 20/50 or better in 48% of cases. However, in patients with preoperative refractive errors of 5 diopters or less, postoperative visual acuity was 20/50 or better in 84% of cases. Average decrease in myopia was 2.5 diopters. Decrease in myopia following radial keratotomy did not correlate with corneal curvature or whether 8 or 16 incision technique was used. However, there was a very significant (P = 0.001) difference in postoperative visual acuity of patients with refractive error of 5 diopters or less, as compared to those with greater than 5 diopters of myopia. Complications included corneal scarring, vascularization, and glare. No microperforation or endothelial cell loss was observed.

Adolescent↗
PubMed1982

Photoperoxidation in lens and cataract formation: preventive role of superoxide dismutase, catalase and vitamin C.

Exposure of rat lens to fluorescent daylight (150 ft candles) under tissue culture conditions led to a substantial lipid peroxidation as evidenced by the formation of malonaldehyde (MDA). MDA content of lenses incubated overnight in presence of such light was approximately sixfold of that in the control lenses cultured in the dark. These cultures were maintained in physiological medium resembling aqueous humor which does not contain any additional photoactive component. Thus, the lens in its physiological surroundings is susceptible to photoperoxidation by light of wavelengths which freely penetrate the eye. Photoperoxidation could be thwarted by superoxide dismutase, catalase, and ascorbate, suggesting that the observed peroxidative degradation is initiated by photocatalytic generation of superoxide and its subsequent derivation to other potent oxidants. These studies provide for the first time suggestive evidence that senile cataract development may in part be linked to the in vivo photochemical generation of superoxide and other potent oxidants in the aqueous humor and lens derived from the ambient oxygen and light; and ascorbate which is maintained at high levels in this fluid by virtue of its active transport from plasma, is physiologically important in preventing the deleterious action of these potent oxidants. The studies thus indicate for the first time the possibilities of a hitherto unrecognized role of ascorbate against cataracts and other age-, light- and oxygen-dependent ocular abnormalities, In addition, the study re-emphasizes the role of tissue catalase and superoxide dismutase in the prevention of photoperoxidative damages to the tissue.

Animals↗