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Biomedical subjects

W E Sponsel

Publications and source records attributed to W E Sponsel.

14 recordsLinked to original sources
PubMed1992

Prevalence of glaucoma. The Beaver Dam Eye Study.

PURPOSE: The purpose of this study is to determine the prevalence of glaucoma in the population participating in the Beaver Dam Eye Study (n = 4926). METHODS: All subjects were examined according to standard protocols, which included applanation tonometry, examination of the anterior chamber, perimetry, grading of fundus photographs of the optic disc, and a medical history interview. Visual field, cup-to-disc ratio, and intraocular pressure (IOP) criteria were used to define the presence of open-angle glaucoma. Definite open-angle glaucoma was defined by the presence of any two or all three of the following: abnormal visual field, large or asymmetric cup-to-disc ratio, high IOP. RESULTS: The overall prevalence of definite open-angle glaucoma was 2.1%. The prevalence increased with age from 0.9% in people 43 to 54 years of age to 4.7% in people 75 years of age or older. There was no significant effect of sex after adjusting for age. Of the 104 cases of definite open-angle glaucoma, 33 had IOPs less than 22 mmHg in the involved eye. Hemorrhage on the optic disc was found in 46 people; 2 of these had glaucoma. Narrow-angle glaucoma was rare, with two definite cases in the population. CONCLUSION: The prevalence of open-angle glaucoma in Beaver Dam is similar to that in other white populations. Findings from this study re-emphasize the notion that estimates of glaucoma prevalence should be based on assessing multiple risk indicators.

Adult↗
PubMed1992

Retinal capillary hemodynamics, visual-evoked potentials, and pressure tolerance in normal human eyes.

Twenty-three normal adult volunteers underwent single eye visual-evoked potential (VEP) and blue field entoptic studies during suction cup-induced intraocular pressure (IOP) elevation, to determine whether IOP-induced changes in VEP are related to alterations in retinal capillary hemodynamics. VEP pressure tolerance testing through an ascending series of 6-8 IOP levels was carried out using a 7.1 Hz reversing checkerboard grating, with amplitudes averaged by Nicolet Pathfinder. Nineteen of the 23 subjects (83%) showed an increase from baseline in their VEP amplitude at IOP values approximating to central retinal diastolic pressures. All subjects underwent subsequent blue field entoptic hemodynamic studies at each of four IOP values related to their VEP pressure tolerance curve--at baseline IOP, at IOP corresponding to the VEP amplitude peak, and at IOPs corresponding to trough points either side of this peak. Blue field studies were conducted in a masked fashion with pressures generated in semirandom sequence. VEP amplitude pressure tolerance curves were found to vary in strong positive concordance with retinal leukocyte velocity pressure tolerance patterns (P less than 0.001). Leukocyte density initially varied inversely to velocity and VEP amplitude, increasing marginally with initial IOP elevation, but then fell in parallel with velocity at IOP levels exceeding the VEP amplitude peak (P = 0.009). These findings indicate a strong interrelationship between retinal hemodynamics and visual pathway activity as measured by VEP, suggesting that vascular autoregulation may account for the characteristic pattern of the normal VEP pressure tolerance curve.

Adult↗
PubMed1992

Retinal hemodynamic effects of carbon dioxide, hyperoxia, and mild hypoxia.

Retinal leukocyte velocity and density were estimated using blue-field entoptic imaging techniques in a controlled double-masked study to determine the relative effects of oxygen and carbon dioxide on perimacular hemodynamics in single eyes of ten normal human subjects. Mild hypoxia (inspiration of 16% O2) did not significantly alter leukocyte velocity or density from room-air baseline levels. Supplementing 16% oxygen with 5% CO2 produced a tendency toward increased leukocyte velocity (+23%, P = 0.027) with no apparent effect on leukocyte density. Inspiration of pure oxygen was associated with significant reductions in both retinal leukocyte velocity (-20%, P less than 0.007) and density (-23%, P = 0.013) relative to room-air baseline levels. Supplementation of pure oxygen with 5% CO2 appeared to produce a dramatic change in perimacular hemodynamics, tending to increase leukocyte velocity (+26%, P = 0.018) with a limited density change (-11%, P = 0.049). These findings suggest that inspired 5% CO2 can counteract the profound inhibitory effects of excess oxygen on retinal hemodynamics in the functionally important perimacular capillary bed.

Adult↗
PubMed1991

Clinicopathologic correlation of diode laser burns in monkeys.

One hundred twenty-five retinochoroidal photocoagulation burns, produced by a transpupillary diode laser (810 nm) in six eyes of three cynomolgus monkeys, were evaluated by clinicopathologic correlation for up to 9 weeks after laser treatment. Diode burns of clinical grade 2 strength were comparable to those described for argon laser. However, diode burns of clinical grade 3 strength produced choroidal changes more intense than those described for argon laser. Where present underneath photocoagulation sites, ciliary nerves in choroid or sclera consistently showed scarring. Prospective randomized controlled clinical trials to document possible clinical equivalence or superiority of diode treatment have not yet been performed. Potential clinical advantages of the diode laser include its weight, size, durability, price, absence of visible flash, and its ability to produce burns that profoundly affect the choroid.

Animals↗
PubMed1991

Association of Vistech contrast sensitivity and visual field findings in glaucoma.

Single eye visual fields and contrast sensitivity were assessed in 60 subjects, who were being followed up in a glaucoma clinic for manifest glaucoma or a suspicion of glaucoma because of raised intraocular pressure. The Fieldmaster 5000 (static/kinetic perimeter) was used for the visual fields, and a Vistech wall chart sine wave grating test was used for contrast sensitivity measurements. The subjects were divided into three groups--defect (D), suspect (S) and normal (N)--on the basis of their perimetric findings by subjective grading of 16 perimetric scoring categories for each visual field. The mean Vistech sensitivity levels were not found to be significantly different between the D, S, and N field subgroups at any of the five spatial frequencies provided on the test charts (1.5, 3, 6, 12, and 18 cycles per degree). Complex algorithms combining results from two or more spatial frequencies also failed to yield any significant differences between the groups. Diagnostic sensitivity and specificities relating Vistech contrast sensitivity findings to groups N and D never concomitantly exceeded 60%.

Adult↗
PubMed1990

Correlation of visual function and retinal leukocyte velocity in glaucoma.

Twelve subjects with glaucoma or ocular hypertension underwent measurement of visual fields (Humphrey perimeter and the Henson CFS2000 perimeter), contrast sensitivity (Vistech wall charts), and perimacular leukocyte velocity (Oculix BFS-1000 blue field entoptic technique). Significant positive correlations were seen between asymmetry of visual function and asymmetry of retinal leukocyte velocity in the study population. The eye with the higher velocity of retinal leukocyte flow tended to have better visual function as measured by Humphrey mean deviation (P less than .05), Henson Score (P less than .06), and Vistech contrast sensitivity score at 6 cycles/degree (P less than .001). An association of borderline significance was found between the asymmetries of intraocular pressure and retinal leukocyte velocity (P = .06). No significant intraocular pressure:visual field correlations were found on asymmetry analysis, although the inverse relationship between intraocular pressure and contrast sensitivity was significant (P less than .05). Significant correlations were obtained between visual field scores derived from the Henson data and Humphrey parameters mean deviation (P less than .001) and corrected pattern standard deviation (P less than .05) on both asymmetry and single eye analysis.

Adult↗
PubMed1989

Evaluation of the Keeler Pulsair non-contact tonometer.

The recently-introduced Pulsair non-contact tonometer (Keeler Instruments, Inc, Broomall, PA) was evaluated against the Goldmann applanation tonometer in cannulated post mortem human eyes, and in living subjects at three clinical centers. Statistical analysis of the findings revealed strong linear relationships between Goldmann or manometric and Pulsair intraocular pressure readings, with correlation coefficients ranging from 0.79 to 0.97. However, with the Pulsair reading as the dependent variable, the slope of the relationship in each case was significantly less than 1.0 (range 0.65 to 0.83), while the intercept was positive (range 1.31 to 2.33 mmHg). Thus, the Pulsair tended to read low at intraocular pressure above the normal range. Conversion factors and a calibration table allowing intraocular pressure estimates more comparable to Goldmann tonometry using the current (J-series) Pulsair are provided herein. A calibration algorithm could be integrated into the circuitry of future production models of the Pulsair instrument.

Aged↗
PubMed1989

Tonometry in question: can visual screening tests play a more decisive role in glaucoma diagnosis and management?

Chronic open-angle glaucoma is a disease in which characteristic changes occur in optic nerve morphology and in ganglion cell function. The utility of intraocular pressure readings in the diagnosis and ongoing management of glaucoma patients is pragmatically considered in the light of the availability of potentially more sensitive means of glaucoma monitoring. Conservative appraisal of the literature suggests that traditional clinical tonometry has low diagnostic sensitivity and specificity. The majority of new cases of glaucomatous visual field loss are most likely to arise from the normotensive population. Clinical studies to determine the correlation between intraocular pressure reduction and the preservation of visual function have repeatedly yielded a much weaker association between these two variables than is perhaps generally assumed. Newer psychophysical methods may have greater potential for rapidly identifying and subsequently monitoring glaucoma patients, but still require refinement and more widespread clinical evaluation. One prerequisite for the eventual adoption of such methods is that clinicians fully appreciate the limitations inherent in tonometry as a glaucoma screening and monitoring technique.

Glaucoma, Open-Angle↗
PubMed1988

A comparative evaluation of timolol maleate and pilocarpine in the treatment of chronic open angle glaucoma.

Ninety-two eyes with newly-diagnosed chronic open angle glaucoma (COAG) were treated in a randomised prospective trial with either timolol or pilocarpine. Their visual field survival was monitored on a 3-monthly basis over 2 years using both Goldmann and Friedmann perimetry. Concomitant tonometric data was derived by applanation. Fields were assessed and quantified using algorithms designed to give the greatest sensitivity for glaucomatous field loss. Microcomputer programmes specifically designed for this purpose were used in the data collection and subsequent analysis.

Aged↗
PubMed1985

Glaucoma assessment by microcomputer.

An automated system for comprehensively monitoring glaucoma patients is described. This economic and practical microcomputer data system has been designed to be thoroughly 'clinician oriented' through the collaborative efforts of ophthalmological and computer specialists. It incorporates novel and efficient methods for transferring both automated and manually recorded perimetry data into analysable digital form. The system is inexpensive, simple to use, maintains safe records, allows thorough analysis of patient data, and can considerably reduce the administrative load on ophthalmological clinics.

Computers↗