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PubMed1991

Physiology of aging and its influence on the contact lens prescription.

The normal progressive physiological and visual effects of aging and its influence on the ability of contact lenses to provide ametropic correction is examined in this article. Of primary significance is the aging eye's perceptual ability especially in the mesopic range of vision. In addition, a recap of current available techniques is included for correction of presbyopia with contact lenses from the perspective of prescribing for an aging patient--not merely a patient who has lost only the ability to accommodate. One of the hallmarks of the profession of optometry has been its traditional support of the premise that patients should be provided with the best possible optical correction. While there are presbyopic patients who can achieve satisfactory vision via the contact lens modalities now in use, the physiological influences discussed here have been generally ignored by the profession. A redefinition of the criteria indicating patient "success" has evolved from achieving satisfaction through excellent vision derived from the optimum optical correction, to satisfaction obtained through patient selection and indoctrination to wear an optically inferior device. Unless the physiological, visual, and psychological effects of aging are adequately compensated by future contact lens designs, most elderly patients will remain likely to return to spectacles as the deficiencies of contact lens correction become progressively more apparent to them.

Accommodation, Ocular↗

PubMed1991

Peripheral corneal degenerations.

Corneal degenerations are among the most commonly encountered disorders in optometry. They are age-related, asymmetrical deteriorations of the cornea with no developmental or hereditary pattern. Although some corneal degenerations may cause pain and profound loss of vision, most are asymptomatic and visually insignificant. This paper will review the histological development, clinical presentation, and management of various peripheral corneal degenerations.

Aging↗

PubMed1991

von Hippel-Lindau disease (angiomatosis of the retina and cerebellum).

von Hippel-Lindau disease is a multi-system disorder characterized by hemangioblastic lesions of the central nervous system and visceral organs. Angiomatosis retinae is often the first observable manifestation of von Hippel-Lindau disease. Optometry may be the initial point of entry into the health care system for the von Hippel-Lindau patient. As such, the eye care practitioner should be aware of the diffuse nature of the disease and initiate the search for silent, possibly lethal, lesions associated with the disease. Management may involve consultation with a neurosurgeon, internist, and retinal specialist. The presentation and clinical course of a young man with von Hippel-Lindau disease is presented.

Adolescent↗

PubMed1991

A clinical study of patient acceptance and satisfaction of Varilux Plus and Varilux Infinity lenses.

An independent study was conducted at the UAB School of Optometry to determine the clinical success with Varilux Plus (Varilux 2) and Varilux Infinity progressive addition lenses (PAL). Two hundred eighty patients (280) were fit between June 1988 and May 1989. The acceptance rate of 97.5 percent was based on the number of lenses ordered versus the number of lenses returned. Patients were contacted by telephone and asked to rate their level of satisfaction with their PALs. A chi-square (non-parametric) test revealed no statistically significant differences in levels of satisfaction with respect to gender, PAL type, or degree of presbyopia. Also, neither refractive error nor previous lens history had a measurable impact on patient satisfaction.

Eyeglasses↗

PubMed1991

The effect of excessive add power on the acceptance of progressive addition lenses.

Twenty-nine subjects wearing Varilux Plus (Varilux 2) or Varilux Infinity lenses were drawn from the UAB School of Optometry primary care clinic population. Using a double-masked, randomized cross-over design, subjects wore one pair of progressive addition lenses (PALs) with a normal add and one pair with the add overplussed by 0.50 D. Subjects wore each pair of lenses for 1 week. Twenty-five of the 29 patients preferred the normal add over the overplussed add. In all subjective response categories the normal add was rated higher than the overplussed add.

Adult↗

PubMed1991

Endometrial cancer, obesity, and body fat distribution.

A case-control study was undertaken to evaluate the roles of obesity and body fat distribution in the etiology of endometrial cancer. The study also included an evaluation of the associations of serum estrone, estradiol, and androstenedione with obesity, body fat distribution, and endometrial cancer risk. The study included 168 cases and 334 control subjects identified at an optometry clinic. A strong, positive relationship between overall obesity and endometrial cancer was found. The relative rate of endometrial cancer for women in the upper 90th percentile of a body mass index compared to those below the median was estimated as 5.5 with 95% confidence limits of 3.2-9.6. There was no association between endometrial cancer and the waist to hip ratio, an index of upper versus lower body fat distribution. A statistical test of trend across the four quartiles of the waist to hip ratio yielded a P value of 0.45 after adjustment for confounding by the body mass index. On the other hand, there was a statistically significant, independent positive effect of a high subscapular to tricep skinfold ratio, a measure of central versus peripheral obesity, on endometrial cancer risk. The relative rates of endometrial cancer for the second, third, or fourth quartile compared to the first quartile of this index were 1.5, 1.9, and 2.7, respectively (P = 0.007), after adjustment for the body mass index. Serum estrone and estradiol, but not androstenedione, were statistically significantly correlated with the body mass index among control subjects (r = 0.37 and 0.40 for estrone and estradiol, respectively). On the other hand, each of the sex hormones was uncorrelated with the waist to hip ratio after adjustment for body mass. The correlations between each of the three hormones and the subscapular to tricep skinfold ratio among controls were weak and were not statistically significant (0.10, 0.10, and 0.14 for estrone, estradiol and androstenedione, respectively). Cases had statistically significantly higher mean serum estrogen and androstenedione levels than did controls and these elevations did not simply reflect a higher prevalence of obesity among them. The findings are equivocal with respect to fat patterns and endometrial cancer. We suggest that future epidemiological studies of cancer and body fat distribution more carefully distinguish among the various types of fat patterns.

Adipose Tissue↗

PubMed1990

The effect of size on paired 'C/D' estimations.

This article describes a comparative study of the accuracy of proportional ratio estimations on stylized optic nerve head targets by experienced optometrists, student clinicians and beginning optometry students. Within limits, these estimations approximate the perceptual and cognitive tasks involved in the clinical estimation of cup-to-disc (C/D) ratios. There was no significant difference (alpha = 0.05) in the accuracy of estimations relative to clinical experience. The overall frequency of exactly correct paired estimations (i.e., both horizontal and vertical correct) for the 16 stylized targets was 18.6%. In a subanalysis of the data, less than half (45.4%) of the estimations were within +/- .05 of the true "C/D" ratios. Statistically, observers were more accurate for the smallest targets and less accurate for the medium and larger targets. Potential clinical implications of these findings, relative to C/D ratio documentation in glaucoma diagnosis and management, are presented and discussed.

Analysis of Variance↗

PubMed1990

The experience of a university-based low vision clinic.

An open low vision clinic has been in operation at University of Wales College of Cardiff, Department of Optometry for 5 years. This paper describes the demography and visual characteristics of 218 consecutively presenting patients. A detailed survey of the aids prescribed is conducted. A significant proportion of low vision patients required only simple aids (56.8%) and low magnification (71.6%). It is suggested that these patients could be assisted in an optometric practice. In addition, visual acuity, distance or near is not a good indicator of eventual visual performance with an LVA. Therefore, it was concluded that all patients having measurable form vision should receive a low vision assessment.

Adolescent↗

PubMed1989

Refractive and structural measures of lid-suture myopia in tree shrew.

In order to study more thoroughly the refractive and structural changes associated with lid-suture myopia, five tree shrews were raised for approximately 16 weeks with monocular visual experience produced by lid closure. Four animals raised with normal laboratory visual experience served as a control group. Compared to the paired open eye, lid-sutured eyes were myopic (-12.1 +/- 6.3 diopters by retinoscopy), corneas were flatter (0.26 +/- 0.18 mm radius increase by photokeratometry) and axial lengths were greater (0.32 +/- 0.17 mm longer by A-scan ultrasonography). The axial length increase was due to elongation of the vitreous chamber (0.38 +/- 0.19 mm longer by A-scan ultrasonography). The open eyes of experimental animals were not significantly different than the normal eyes of control animals. Two of these treatment effects, namely, refractive state changes and axial length increases, were demonstrated with independent techniques: streak retinoscopy was compared to coincidence optometry, and A-scan ultrasound was compared to axial measurements of photographs of frozen, sectioned eyes. The three main ocular effects of eyelid closure were stable over three measurement sessions completed within a 4 week period. Additional refractive and A-scan measurements taken 7.5 months later showed no significant changes. Optical modelling showed that the observed myopia of the lid-sutured eye is consistent with the observed elongation of the vitreous chamber coupled with the flattened cornea although other changes could not be ruled out. We conclude that an axial myopia is produced reliably in tree shrews by raising them with eyelid closure and that the measurement techniques used in this study have sufficient resolution to study the development of myopia in this species.

Animals↗

PubMed1989

Automated perimetry in the management of glaucoma.

As optometry's role and responsibilities increase, so does our need to understand and utilize new technological advances to aid in our understanding and management of ocular conditions. Automated perimetry represents one such technological improvement that enhances our ability to detect and analyze the visual field changes associated with glaucoma. An understanding of the automated perimeter's abilities and limitations is needed to effectively incorporate it into the management of glaucoma.

Automation↗

PubMed1989

Contact lens induced giant papillary conjunctivitis: a retrospective study.

In this retrospective epidemiological study, records from the Contact Lens Department of SUNY College of Optometry were randomly selected and reviewed. An association between contact lens induced giant papillary conjunctivitis (GPC) and a FDA classified sub-category was found. Younger patients were shown to have a higher risk of developing GPC. Gender and tear film break-up time were not found to be associated with the condition. The mean replacement time for hydrogels was 10.8 +/- 9.2 months with no significant differences among contact lens polymer types. The GPC phenomenon was almost exclusively bilateral with a mean onset time of 31.4 months after commencing lens wear. A model for the development of GPC based on tear film interactions with the hydrogel lens surface is presented. A model for the tear film's interaction with the hydrogel contact lens in situ is offered.

Adult↗

PubMed1986

A review of the role of sympathetic innervation of the ciliary muscle in ocular accommodation.

Although it is well established that autonomic control of ocular accommodation is predominantly parasympathetic, many investigators have, over the last 150 years, proposed that a supplementary sympathetic innervation should be considered. Particular attention is directed in this review to previous literature providing anatomical, physiological and pharmacological evidence for dual innervation of the ciliary muscle. Clinical and psychological evidence is shown to be equivocal. A review of recent laser optometry studies of tonic ("dark-focus") resting positions of accommodation indicates that the inhibitory nature of sympathetic innervation suggested by the majority of previous studies can be further defined with respect to specific adrenergic receptors. The implications of dual innervation relating to ocular accommodation during sustained near-vision tasks is discussed.

Accommodation, Ocular↗

PubMed1989

Effects of nearpoint visual stress on psycholinguistic processing in reading.

To date, there have been few studies to evaluate directly the relationship between binocular visual stress and reading performance. This study employed the cloze procedure to demonstrate the effects of nearpoint stress on performance and efficiency in reading comprehension. Using 19 third year optometry students as subjects, binocular stress was simulated by -2.00 D lenses. Performance, as determined by the time to complete the task, was significantly reduced (p less than .03), but no significant differences in accuracy scores were measured.

Adult↗

PubMed1985

The relationship between tonic accommodation and ciliary muscle innervation.

Previous studies have used Badal laser optometry to demonstrate significant variance in the distribution of tonic (or "dark-focus") resting positions of accommodation (TA) for groups of observers. This study investigates whether individual differences in TA are due to individual differences in autonomic tone of the ciliary muscle by comparing separately the effects of a muscarinic receptor antagonist (Tropicamide 0.5%) and a beta receptor agonist (Isoprenaline 3%) on the distribution of TA. Ten subjects were used for each study with mean ages of 23.2 and 23.0 yr, respectively. The distribution of TA within each subject group was equivalent to the large sample distributions published in previous literature. Darkroom measurements of TA and pupil diameter were determined with a Badal laser optometer and infrared photography. Distance correction and amplitude of accommodation were determined by standard optometric techniques. Isoprenaline produced a significant hyperopic shift in TA of 0.47 D over 22 min but this was not accompanied by a significant change in standard deviation of the TA distribution. This finding was in accord with the authors' previously reported investigation using the beta receptor antagonist Timolol Maleate. Tropicamide also produced a significant hyperopic shift in TA of 1.24 D over 24 min, and this was accompanied by a significant change in standard deviation of the distribution from 0.87 to 0.17. The results indicate that the parasympathetic system plays a significant role in determining the TA position and that the variations in TA between individuals is a consequence of parasympathetic rather than sympathetic ciliary muscle tone.

Accommodation, Ocular↗

PubMed1988

Adult visual system plasticity.

The functional area of optometry assumes plasticity of the neurological input to the visual system. This paper reviews the literature which investigates adult visual system plasticity. Literature on development of the visual system, as well as adult central nervous system plasticity, provides additional inferences. A discussion is presented suggesting that there exists a multiplicity of sensitivity periods within the visual system.

Animals↗

PubMed1988

An evaluation of four end-user systems for searching MEDLINE.

This study compared features and determined which of four end-user systems (PaperChase, GRATEFUL MED, Med-Base, or Compact Cambridge: MEDLINE) would best serve the Medical Sciences and Optometry Libraries of Indiana University in providing biomedical information to faculty and graduate students through MEDLINE. Cost, ease of use, retrieval, training needs, equipment requirements, and adequacy of documentation were examined. The study consisted of a comparison of the features of each system based on available documentation; a controlled search performed by the investigators on each system and on regular NLM MEDLINE; and a user study based on observations, questionnaires, and interviews with eleven library patrons who performed the same search of their choice on each of the four systems.

Computer Systems↗

PubMed1988

An evaluation of four end-user systems for searching MEDLINE.

Computer User Training↗

PubMed1988

Dominant inheritance of Stargardt's disease.

Ten members of an extended family have come to the Indiana University (IU) Optometry Clinic in Indianapolis for low vision services. All 10 individuals had lost vision as the result of a juvenile onset hereditary macular degeneration. The funds appearance consisted of an atrophic macular degeneration surrounded by the characteristic yellowish flecks of Stargardt's disease. A study of the family tree revealed a clearly dominant mode of inheritance, whereas Stargardt's disease has traditionally been considered a recessive trait. We are presenting this family study as an unusual instance of dominant inheritance of Stargardt's disease.

Adult↗