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Biomedical subjects

R L Yolton

Publications and source records attributed to R L Yolton.

At least 19 recordsLinked to original sources

The dizzy patient: a review of etiology, differential diagnosis, and management.

BACKGROUND: Dizziness is a lay term used to describe a variety of sensations. Unfortunately, the term "dizziness" does not have a precise medical definition, and additional information is typically required to further define the patient's problem. METHODS: When dizziness is a presenting complaint, distinctions must be made between vertigo (a sense of false movement), near-syncope (a feeling of impending faint), disequilibrium (loss of balance), and ill-defined lightheadedness (an inability to concentrate or focus the mind). Possible causes of dizziness include conflicts between visual and vestibular information, vascular problems, adverse reactions to medication, psychological difficulties, systemic disease, and the effects of aging. RESULTS: Dizziness is a symptom of a physiological or psychological illness, and therefore management is typically directed toward treatment of the underlying illness. In some cases the cause of the dizziness cannot be found, however, or is untreatable. In these cases, management is directed toward symptom reduction. CONCLUSIONS: Dizziness is a relatively common problem that arises from a variety of causes. In many cases, optometrists can participate in the diagnosis and management of patients with complaints of dizziness.

Diagnosis, Differential

Second opinion: a computer expert system designed to aid in the determination of spectacle lens prescriptions.

BACKGROUND: Expert systems (ESs) are computer programs that simulate the decision-making ability of human experts. In this project, an ES was developed that used optometric data and decision rules to determine spectacle lens prescription powers. METHODS: Decision rules derived from clinical experience and standard references were provided to a commercially available shell program to create an ES called Second Opinion. The ES determined spherical, cylindrical, and add powers designed to provide maximum acuity consistent with a high probability of patient acceptance. CONCLUSIONS: Second Opinion demonstrates how a computer program can be used to analyze optometric data and offer suggestions regarding lens prescriptions.

Adult

The effects of gender and birth control pill use on spontaneous blink rates.

BACKGROUND: Two major reference works suggest that men and women blink spontaneously at different rates, but they disagree with regard to which gender blinks faster. METHODS: Spontaneous blink rates of 59 males and 86 females, 44 of whom were taking birth control (BC) pills, were measured for 5 consecutive minutes. Schirmer test results and tear break-up times (TBUTs) were also obtained. RESULTS: Females taking BC pills blinked at a mean rate of 19.6 times per minute, females not taking birth control pills blinked 14.9 times per minute, and males blinked 14.5 times per minute. There were very large differences between blink rates for individuals in each of the groups. No strong associations were found between spontaneous blink rates and a history of contact lens use, tear break-up time, Schirmer test results, temperature or humidity in the examination room, subject age, or menstrual cycle phase. CONCLUSIONS: The 32 percent increase in mean blink rate for females taking BC pills suggests that the pills affect at least one of the mechanisms that control spontaneous blinking, but it is unclear how they accomplish this.

Adult

Demonstration of a neural network expert system for recognition of glaucomatous visual field changes.

Expert systems (ESs) are computer programs designed to make decisions in a manner similar to the way human experts make them. There are many forms of ESs, ranging from those that are given specific If-Then rules to those that are capable of deriving their own rules. Some ESs use neural network simulations to analyze patterns of data. In this project, a commercially available neural network shell program was used to demonstrate the development of an ES capable of analyzing the visual field loss patterns produced by glaucoma. Potential applications of ESs for the diagnosis of glaucoma are discussed.

Decision Making, Computer-Assisted

Comparison of Irlen scotopic sensitivity syndrome test results to academic and visual performance data.

UNLABELLED: Irlen has defined a condition called Scotopic Sensitivity Syndrome (SSS) that is associated with reading problems. According to Irlen, SSS can be treated by the use of colored filters, but there is disagreement about the existence of SSS and the efficacy of colored filter therapy. METHODS: Thirty-nine children participated in the study: 24 were academically normal, nine had specific reading problems, and six had problems in multiple academic areas. SSS levels and preferred overlay colors were determined. Optometric test data were also available for each subject. RESULTS: No significant relationships were found between academic classification and degree of SSS. There were also no significant relationships between preferred overlay color and any other variables. There was, however, a significant tendency for subjects with higher SSS levels to be candidates for vision therapy and to derive greater benefit from the colored overlays. CONCLUSIONS: Many questions about the use of colored filters for the treatment of reading problems remain unanswered. Among these are questions dealing with whether the M-pathway anomalies found in some dyslexics are also present to a lesser degree in other cases of reading disabilities, and how colored filters could re-balance the M- and P-pathways. Is it the color of the filter itself that is critical, or is it the change in luminance or contrast produced by the filter that seems to make it easier for some subjects to read? More research will be needed to answer these questions.

Child

The optometry game: enhancing test selection and lens prescribing skills by use of computer simulations.

The Optometry Game is a computer simulation developed to aid students in practicing test selection and lens prescription skills. Features of the simulation include a game format, digitally reproduced voices and patient pictures, and the ability of the user to customize the game for a variety of applications. Twenty optometry students evaluated the game by playing a variety of simulated patients and found it to be potentially useful in various classroom learning environments.

Computer Simulation

Evaluation of dietary antioxidant levels and supplementation with ICAPS-Plus and Ocuvite.

BACKGROUND: Oxidative damage caused by free radicals has been implicated in the development of age-related macular degeneration (ARMD). Recent studies suggest that antioxidant vitamins and minerals can be useful for the management and/or prevention of this condition. METHODS: To assess the normal dietary intake of the antioxidants, 28 healthy subjects 55 years of age and over completed a diet survey. Then two over-the-counter (OTC) nutritional supplements that make claims about the antioxidant nutrients they contain (ICAPS-Plus and Ocuvite) were evaluated with respect to their ability to raise blood levels of two important antioxidant nutrients: zinc and beta-carotene. RESULTS: Based on the diet survey, 26 of the 28 subjects were found to have deficient intakes; zinc and selenium were the most commonly deficient nutrients. Following a 2-week administration period, both ICAPS-Plus and Ocuvite significantly raised mean serum zinc levels 24.7 percent and 18 percent respectively; ICAPS-Plus significantly raised mean beta-carotene levels by 21.4 percent, but Ocuvite did not change the mean level significantly. CONCLUSIONS: Based on the probable relationship between antioxidant levels and diseases such as ARMD, these results suggest that OTC supplements might be useful for selected patients.

Aged

Free radicals and antioxidant supplementation: a review of their roles in age-related macular degeneration.

BACKGROUND: Age-related macular degeneration (ARMD) is a major cause of blindness in the elderly. Unfortunately, no proven form of treatment is currently available for the dry, atrophic form of ARMD seen in more than 90 percent of patients with this condition. METHODS: A recent theory suggests that ARMD is associated with damage to the retina caused by free radicals. If this is correct, it is possible that the damage could be prevented or moderated by supplementing the diet with specific antioxidant vitamins and minerals that enhance the body's natural defenses against free radicals. RESULTS AND CONCLUSION: This paper reviews the literature regarding the pathogenesis of ARMD and presents a rationale for its management or prevention by the use of supplemental vitamins and minerals.

Antioxidants

The effect of fluorescent whitening agent on hunter camouflage clothing.

Fluorescent whitening agents (FWAs) are chemicals added to most fabrics and papers during manufacture to increase color temperature, "whiteness," and "brightness." FWAs accomplish this by absorbing energy in the ultraviolet (UV) part of the spectrum and emitting it as visible blue light. Recently, hunters have become concerned that FWA could be reducing the effectiveness of their camouflage clothing. As a result, some manufacturers have begun making their camouflage clothing (camo) without FWA, and a spray-on product has been introduced to block the action of FWA. Radiometric spectra from camo and foliage samples suggest, however, that these concerns might not be fully justified. Under full sun and in the shade, spectra from 300 to 500 nanometers (nm) (i.e., UV and visible blue light) showed that camo samples containing FWA matched the foliage reasonably well. No evidence of a major problem caused by the FWA was detected, and no significant need for the use of UV absorbing dyes to block the action of FWA was found.

Animals

Automated decision making: the role of expert computer systems in the future of optometry.

BACKGROUND: Artificial intelligence (AI) refers to the ability of a machine, or system, or computer program to make intelligent decisions using the same methods that humans would use. By definition, and expert system (ES) is a computer program that uses knowledge and inference procedures to solve problems which would otherwise require the application of human expertise. METHODS: The role of expert systems in current and future applications in a number of fields were reviewed. RESULTS: Expert systems have and will be making an impact in many fields, including optometry in the future. CONCLUSIONS: Expert systems present an opportunity for the profession of optometry to become more efficient or accurate, provided that their development cost could be justified.

Artificial Intelligence

Clinical evaluation of the Keeler PULSAIR 2000 tonometer.

Intraocular pressures (IOPs) were obtained from 380 eyes of 190 normal subjects using hand-held Keeler PULSAIR 2000 and slit lamp-mounted Goldmann tonometers. IOPs obtained with the PULSAIR were in close agreement with Goldmann pressures over the range of IOPs represented in the subject population (9-27 mmHg). This agreement is better than that found in a previous study comparing the original PULSAIR model to the Goldmann, and suggests that the model 2000 represents a significant improvement over the original unit.

Adolescent

Exploring the optometric application of expert computer systems: refractive error correction.

Using the commercially available shell programs NeuroShell and EXSYS, example-based and rule-based expert computer systems were developed to explore how such systems could be applied in an optometric environment. To demonstrate such an application, the example-based NeuroShell system was taught to prescribe sphere and cylinder powers for low refractive error myopes. When the system learned with only the chief complaint, habitual prescription and acuity through the habitual, and best refraction with resulting acuity, it predicted the sphere and cylinder powers prescribed by human optometrists within 0.25 diopter 97 and 98 percent of the time, respectively, for 60 test eyes. With a set of only three rules, the rule-based EXSYS system predicted sphere powers within 0.25 diopter of the prescribed powers for 100 percent of the 60 test eyes. Results with these very simple refractive problems suggest that teaching expert computer systems to prescribe ophthalmic lens corrections is possible, and further suggest that the concept could be extended to more complex and challenging patient populations.

Eyeglasses

Applications of expert computer systems.

An expert system is a computer program which uses artificial intelligence to make logical decisions on the basis of input data. The rules the system uses to make its decisions are called heuristics which can be provided in the form of IF . . . THEN statements, or they can be learned by the system from examples. The term "expert" is used because the rules or examples come from human experts and the program is considered to have captured their expertise. Currently there are many expert systems in business and medical use but few, if any, are used in optometry. The rule-oriented nature of many ophthalmic procedures suggests a future role for these systems, but their cost-effectiveness may not yet be favorable enough to justify development of expert systems for optometric practice.

Diagnosis, Computer-Assisted

Clinical comparison of air-puff and Goldmann tonometers.

Intraocular pressures (IOPs) as measured with the Topcon CT-10, Reichert XPERT and NCT II, and Keeler PULSAIR air-puff tonometers were compared to the Goldmann IOPs for 452 eyes ranging in pressure from 6-40 mmHg. For eyes with pressures in the 10-20 mmHg range, the CT-10 read consistently too high. The XPERT and the NCT II read too high in the lower part of this range and too low in the higher part. The PULSAIR read too low across the entire range. At higher pressures, all of the tonometers read too high except the PULSAIR which again read too low. CT-10, XPERT, and NCT II and PULSAIR pressures were within 4.0 mmHg of Goldmann readings for 81, 85, 89 and 72 percent of the eyes, respectively. Subjects selected the XPERT as the most preferred tonometer and the NCT II was the least preferred mainly because of perceived air-puff intensity.

Adolescent

Effects of monocular occlusion on neural and motor response times for two-dimensional stimuli.

Previous studies have shown that there are advantages associated with the simultaneous use of both eyes to view two-dimensional stimuli. To investigate further this binocular advantage, three experiments were conducted using male and female names presented on a video display as stimuli. In the first experiment, simple reaction times (RT's) were found to increase by about 6% as a result of monocular occlusion. In the second experiment, visual evoked response (VER) and P300 implicit times were also found to increase as a result of occlusion. The third experiment confirmed these results and investigated the sensitivity of evoked potential techniques to changes in stimulus complexity. The three experiments demonstrate that monocular occlusion does have a significant effect on processing speed for two-dimensional visual stimuli. The major portion of this effect (62%) is manifest at the level of the visual cortex, and is not perceived by subjects as significantly increasing the mental workload associated with generating responses to these stimuli.

Adult