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Biomedical subjects

G L Rogers

Publications and source records attributed to G L Rogers.

At least 19 recordsLinked to original sources
PubMed2000

Spectral model of a fluorescent ink halftone.

A model is presented of a fluorescent ink halftone. Unlike a nonfluorescent ink, which only absorbs, a fluorescent ink absorbs higher-energy photons and emits lower-energy photons. The amount of fluorescent light produced depends on the percent absorption of the incident light. For fluorescent ink printed on paper, both photon scattering within the paper substrate and multiple internal reflections between the ink layer and the paper substrate significantly increase the percent absorption, so a realistic model must include these effects. The model presented here utilizes the generalized Clapper-Yule theory, which accounts for photon diffusion that is due to both scatter and internal reflection. It is shown that while multiple internal reflections alone only marginally increase the percent absorption, when there are both scattering and internal reflection, the percent absorption is increased significantly. The current study is a theoretical model and does not present experimental results.

Journal Article↗
PubMed1999

Pseudotumor cerebri in children receiving recombinant human growth hormone.

PURPOSE: This article represents the first report in the ophthalmology literature of an association between pseudotumor cerebri (PTC) and recombinant human growth hormone (rhGH). DESIGN: Noncomparative case series. PARTICIPANTS: Three children receiving rhGH for short stature with Turner syndrome, Jeune syndrome, or Down syndrome. METHODS: Children underwent full ocular examination. After papilledema was identified, patients underwent lumbar puncture and imaging with either magnetic resonance imaging or computerized tomography. Treatment was under the guidance of the primary physician or neurosurgeon. The rhGH was discontinued in all children. MAIN OUTCOME MEASURES: Visual acuity and evaluation of the optic nerve for resolution of papilledema were followed at each examination. RESULTS: In all three cases, papilledema resolved with the cessation of rhGH, and treatment with acetazolamide or prednisone. Visual acuity was unchanged in case 1, decreased by two to three lines in case 2, and was inconsistent in case 3. One child (case 2) required a ventriculoperitoneal shunt for persistent elevation of intracranial pressure. CONCLUSION: There appears to be a causal relationship between the initiation of rhGH with the development of PTC. Children should have a complete ophthalmic evaluation if they report headache or visual disturbances. Baseline examination with routine follow-up should be instituted when children cannot adequately communicate.

Adolescent↗
PubMed1998

Strabismus in premature infants in the first year of life. Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVES: To present the 3- and 12-month strabismus data from 3030 premature infants with birth weights less than 1251 g enrolled in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity. DESIGN: Data from the 3- and 12-month examinations conducted at 23 regional study centers were tabulated for all infants. The main outcome measure, ocular motility, was compared with baseline demographic variables and retinopathy of prematurity severity for the worse eye. Findings at 3 months were compared with the incidence of strabismus at 12 months. RESULTS: At 3 months, 200 (6.6%) of the 3030 infants were strabismic. In the 2449 infants examined at both time points, 289 (11.8%) were found to have strabismus at 12 months. Retinopathy of prematurity was significant for strabismus at both 3 and 12 months (P<.001). The presence of strabismus at 3 months was found to be a highly significant predictor of strabismus at 12 months. Anisometropia, abnormal fixation, and unfavorable retinal structure also were significant predictors of strabismus at 1 year. The total prevalence of strabismus in the first year of life was 14.7%. CONCLUSION: The presence of acute-phase retinopathy of prematurity places the premature infant at increased risk for strabismus.

Cryotherapy↗
PubMed1998

A comparison of cryotherapy versus diode laser retinopexy in 100 consecutive infants treated for threshold retinopathy of prematurity.

PURPOSE: The purpose of this paper is to present a series of patients who were treated for threshold retinopathy of prematurity with either cryotherapy or diode laser. Complications and unfavorable outcomes during the first year after treatment will be compared for the two procedures. METHODS: The clinical courses of a consecutive series of 100 infants (192 eyes) were reviewed. All infants had their threshold status confirmed by a second examiner. Infants were treated with cryotherapy through 1993 and with diode laser thereafter. One hundred two eyes of 54 patients were treated with cryotherapy. Ninety eyes of 46 patients were treated with laser retinopexy. Two of the patients who were treated with laser (4 eyes) did not survive to the 3-month follow-up visit, and their results are not included here. The two groups of infants were comparable in their birth weight, adjusted gestational age at treatment, and severity of disease as determined by zone and sectors of stage 3 retinopathy of prematurity. RESULTS: Unfavorable outcome (total retinal detachment) was seen in 25.4% of eyes treated with cryotherapy (26 of 102), as compared with 15% of eyes treated with laser (13 of 86). Two cataracts were seen in our patients: one patient 22 weeks after cryotherapy, and the other 7 months after diode laser. CONCLUSIONS: No statistically significant difference was found in the rate of retinal detachments in the two groups (X2 = 3.05; P = .08).

Birth Weight↗
PubMed1998

Levodopa-carbidopa and childhood retinal disease.

PURPOSE: Our purpose was to determine the influence of levodopa-carbidopa on visual function in children with retinal disease. METHOD: Two studies were undertaken, a single-dose study and a longitudinal dosing study. A double-masked, placebo controlled single-dose study was undertaken of levodopa-carbidopa (2.08 mg/kg of body weight levodopa with 25% carbidopa) on monocular visual acuity in 14 children with retinal disease. Subjects received two capsules approximately 2.5 hours apart, and monocular visual acuity was measured 2 hours after each capsule ingestion. The second study was a double-masked, placebo-controlled 12-week longitudinal dosing (0.62 mg/kg of body weight) crossover study in which subjects received levodopa-carbidopa for 6 weeks and placebo for 6 weeks. RESULTS: The single-dose study revealed a small but statistically significant improvement in monocular visual acuity after levodopa-carbidopa ingestion. The longitudinal study revealed a small but statistically significant improvement in binocular visual acuity after levodopa ingestion. In both studies placebo had no significant effect on visual acuity. Six subjects participated in both studies and demonstrated a significant correlation (r = 0.76, p < 0.05) between change in visual acuity in the single-dose study and the longitudinal dosing study. CONCLUSION: The results are consistent with the hypothesis that dopamine influences the receptive field characteristics of retinal cells. The results also suggest that there may be low retinal dopamine levels in some types of retinal disease, which may be amenable to treatment.

Adolescent↗
PubMed1998

Occlusion and levodopa-carbidopa treatment for childhood amblyopia.

PURPOSE: The purpose of the current study was to compare the effects of levodopa-carbidopa with and without part-time occlusion on visual function in older amblyopic children. METHODS: Thirteen older amblyopic children were randomly assigned to receive or not receive part-time occlusion (3 h/day) combined with 7 weeks of oral dosing with levodopa-carbidopa (1.02 mg/0.25 mg/kg body weight three times daily). Visual acuity, contrast sensitivity, and fusion were measured at baseline; 1, 3, 5, and 7 weeks during the treatment regimen; and 4 weeks after termination of all treatment. At these same times health status was assessed with standard laboratory blood tests, physical examination, and subjective questionnaire. RESULTS: From baseline to the follow-up test trial, both groups improved in visual acuity in the amblyopic eyes (occlusion group 20/116 to 20/76, P < .001; no occlusion group 20/90 to 20/73, P < .01) and dominant eyes (occlusion group 20/18 to 20/15, P > .05; no occlusion group 20/20 to 20/16, P < .01). The occlusion group exhibited a significant decrease in the difference in acuity between the dominant and amblyopic eyes of 1.3 lines (P < .02), whereas the no occlusion group revealed no significant effect. A comparison between groups revealed a significantly greater improvement in visual acuity in the amblyopic eye in the occlusion group compared with the no occlusion group (P = .01). In contrast, there was no significant difference between groups in terms of the change in visual acuity in the dominant eye (P = .15). Mean log contrast sensitivity in the amblyopic eye significantly improved in the occlusion group and did not significantly change in the no occlusion group. Fusion changed similarly in both groups. The improvements in visual function were maintained 4 weeks after the termination of all treatment. Adverse side effects were minimal in both groups. CONCLUSION: The combination of levodopa-carbidopa and occlusion improves visual function more than levodopa-carbidopa alone in older amblyopic children.

Administration, Oral↗
PubMed1996

Effects of somatic cell count and stage of lactation on raw milk composition and the yield and quality of Cheddar cheese.

The effects of somatic cell count and stage of lactation on the yield and quality of Cheddar cheese were investigated. Cheese was manufactured in a pilot scale factory using milk of low bulk milk cell count (BMCC) from herds in early (LE) and late (LL) lactation, and milk of high BMCC from herds in early (HE) and late (HL) lactation. The deleterious effect of an elevated BMCC on product yield and quality in late lactation was clear. Cheese made from LL milk was significantly superior to that made from HL milk for most yield and quality characteristics measured. Stage of lactation also affected cheese yield and quality, as evidenced by the lower recovery of fat and poorer flavour score for cheese from LL milk compared with that manufactured from LE milk. The observed differences could be explained largely by differences in raw milk composition. We conclude that the effect of stage of lactation was magnified by an elevated BMCC, and that many of the problems encountered when processing late season milk could be overcome by containing mastitis at this time.

Animals↗
PubMed1996

Effect of somatic cell count and stage of lactation on the quality and storage life of ultra high temperature milk.

The effects of bulk milk cell count (BMCC) and stage of lactation on the quality and storage characteristics of UHT milk were investigated. The UHT milk was manufactured in a pilot plant using milk of low BMCC from early and late lactation, and milk of high BMCC from early and late lactation. Upon storage at 20 degrees C, early lactation UHT milk gelled far ahead of late lactation milk. Within each stage of lactation, high BMCC milk tended to gel first. Few differences in the organoleptic properties of the UHT milks were observed. It was apparent that the onset of age gelation may not always be related directly to the level of proteolysis, and that other factors influencing milk composition and the reactions between milk components may play more important roles. At a particular stage of lactation, proteolysis induced by mastitis may hasten the onset of gelation.

Animals↗
PubMed1995

Flash visual evoked response binocular summation in normal subjects and in patients with early-onset esotropia before and after surgery.

Flash visual evoked responses were recorded and visual evoked response binocular summation was assessed in normal children between the ages of 1 and 58 months, in normal adults and in children with early-onset esotropia before and longitudinally for 1 year after surgical binocular alignment. Normal flash visual evoked response binocular summation started in the range of facilitation (> 2.0) at 1 month of age and decreased to adult levels by 3.7 months of age. The shape of the flash visual evoked response binocular summation function obtained from the patients with early-onset esotropia, appeared similar to that of normal subjects; however, the rapid decrease in flash visual evoked response binocular summation from facilitation to normal adult levels occurred after surgical binocular alignment. In normal adults, flash visual evoked response binocular summation was significantly reduced by a 40-diopter base-in prism, suggesting that binocular misalignment was not the reason for the facilitation in flash visual evoked response binocular summation in either childhood population. It is proposed that this facilitation may reflect a process that leads to binocularity and that develops rapidly with binocular alignment.

Adolescent↗
PubMed1993

Levodopa/carbidopa for childhood amblyopia.

PURPOSE: To evaluate the efficacy and tolerance of two low doses of levodopa/carbidopa (25/6.25 mg, 50/12.5 mg) and placebo (Tums) in 20 children with amblyopia between the ages of 4 and 14 years. METHODS: A double-masked placebo-controlled randomized 8-hour study was performed during which subjects received one of two doses of levodopa/carbidopa or placebo, combined with occlusion of the dominant eye. Visual acuity was measured at baseline and at 1 and 5 hours after capsule ingestion. Tolerance was assessed by questionnaire and physical examination. RESULTS: Visual acuity significantly improved by one line, from an overall average of 20/121 to 20/96, in the amblyopic eyes of both groups that received levodopa/carbidopa. Visual acuity did not significantly change in the placebo group. Tolerance was similar among all three groups. CONCLUSION: Average dose levels of 0.95/0.24 mg/kg and 1.94/0.49 mg/kg of levodopa/carbidopa were found to be well tolerated and efficacious at temporarily improving visual acuity in amblyopic eyes of children.

Adolescent↗
PubMed1992

Electro-oculogram in vitamin A deficiency associated with cystic fibrosis. Short communication.

Electro-oculograms (EOGs) were recorded in a patient with cystic fibrosis and vitamin A deficiency before and during vitamin A supplementation (25,000 IU/day). Before vitamin A supplementation the EOG Arden light/dark ratio was 1.27. After seven months of vitamin A supplementation the Arden ratio increased to 3.0. These results reveal that vitamin A deficiency can cause an abnormal EOG.

Adolescent↗
PubMed1992

Retinoblastoma, microphthalmia, coloboma, and neuroepithelioma of the pineal body.

A one-month-old infant boy was examined early in life because his mother had bilateral retinoblastoma and his father had bilateral microphthalmia. The ophthalmologist found his right eye was normal size with a coloboma of the iris, choroid, and retina. The left eye was microphthalmic with a coloboma of the uveal tract and retina. A vascularized fluffy white mass in the posterior pole was diagnosed clinically as a retinoblastoma. The tumor regressed with radiation. When the patient was four years of age, a large tumor was found in the region of the pineal recess, causing hydrocephalus and seizures. A biopsy showed an undifferentiated malignant neuroepithelial neoplasm. The patient died within three months of diffuse central nervous system tumor. The unusual findings of a retinoblastoma in a microphthalmic eye with bilateral colobomas and a neuroepithelial neoplasm of the pineal gland are discussed.

Abnormalities, Multiple↗
PubMed1992

A prospective study of ocular abnormalities in hearing impaired and deaf students.

In a prospective study of 505 hearing impaired and deaf students conducted at Children's Hospital Eye Clinic, 48.7% were found to have significant ocular abnormalities. The prevalence of myopia, astigmatism, and pathological intraocular changes was found to be significantly increased over the general population. In addition, the prevalence of ocular abnormalities generally increased with the severity of the hearing loss. Of importance was the high prevalence of rubella-consistent abnormalities in the hearing impaired and deaf student populations. Rubella syndrome may be responsible for a major portion of high refractive errors and ocular pathological changes. It is recommended that ENT specialists and pediatricians be aware of the nearly 50% chance of ocular abnormality in hearing impaired and deaf students, and that ophthalmologic examination may be valuable for identification or confirmation of the etiology of hearing impairment.

Adolescent↗
PubMed1991

Loss of contrast sensitivity in cystic fibrosis.

We measured the contrast sensitivity function in a 16-year-old boy with cystic fibrosis, before and during vitamin A supplementation. Before vitamin A supplementation, serum levels of vitamin A were abnormally low, the electroretinogram was reduced, and contrast sensitivity was abnormally low at all spatial frequencies. During vitamin A supplementation (25,000 IU/day), serum levels of vitamin A became low normal, the electroretinogram returned to normal, and the overall contrast sensitivity function improved by 94%. We propose that the contrast sensitivity function may be abnormal in patients with cystic fibrosis who have reduced retinal function secondary to vitamin A deficiency.

Adolescent↗
PubMed1991

Contrast sensitivity of optokinetic nystagmus.

To determine the threshold characteristics of optokinetic nystagmus (OKN), contrast thresholds for involuntary OKN were measured for gratings of different spatial frequency to yield an OKN-contrast sensitivity function (OKN-CSF). The OKN-CSF resembled an inverted U-shaped function with temporal-to-nasal and nasal-to-temporal movement yielding similar functions. In addition, when psychophysical CSFs were determined for separate form and movement thresholds, it was discovered that the OKN-CSF approximated the psychophysical-movement CSF rather than the psychophysical-form CSF.

Adult↗
PubMed1991

CSF interocular interactions in childhood ambylopia.

Contrast sensitivity functions (CSF's) were measured in the amblyopic and dominant eyes of 17 strabismic and 28 anisometropic children and in 19 similar age normal controls. A three-alternative forced-choice procedure was used to measure CSF's with the VCTS 6500. The results revealed reduced contrast sensitivity (CS) in both the amblyopic and dominant eyes of strabismic and anisometropic amblyopes compared to normal controls. Statistically significant intereye correlations of CS at each spatial frequency were found in all groups and in the presence of deep amblyopia, suggesting continued interocular interactions and binocularity. A separate longitudinal study of 7 of the amblyopes showed that, during the course of occlusion therapy, both the amblyopic and the dominant eyes improved in CSF. The results suggest that the amblyopic eye may influence CS in the dominant eye through interocular interactions. This process may serve to minimize CSF differences between the eyes and maximize binocular vision.

Amblyopia↗
PubMed1991

Visual-evoked response binocular summation in normal and strabismic infants. Defining the critical period.

Pattern visual-evoked response binocular summation (VERBS) was recorded in normal infants, between the ages of 1-58 months, and in similar-aged esotropic infants before and at various times after corrective surgery. The normal subjects had no significant VERBS at 1.5 months of age, developed a rapid acceleration of VERBS between 1.5-3 months, and then gradually declined in VERBS from 3-58 months. The peak of the VERBS by age function at 3 months was well in the facilitation range (greater than 2.0) and corresponded to the general age range for the onset of binocular eye alignment, fusion, and stereopsis. The results from the early-onset esotropic patients revealed a similar function to that found in normal subjects; however, the function was triggered by surgical eye alignment. The peak of the VERBS function for esotropic subjects was lower than normal, and the initial rise was less rapid. It is proposed that the VERBS function reflects the human critical period for the development of binocular vision. In this framework, data from both infant developmental studies and adult studies were clarified.

Adolescent↗