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PubMed2004

Enhancing vision care integration: 1. Development of practice algorithms.

BACKGROUND: Appropriate access to the best quality of vision care is enhanced when patients receive eye care services from the right professional, at the right time, and in the right place. This paper, the first in a two-part series, describes the development of an integrated framework for vision care delivery. Specifically, two patient-centred vision care algorithms for the multidisciplinary management of diabetic retinopathy and the red eye are outlined, and the process that resulted in their development is described. METHODS: The method used relies on a description of a multidisciplinary collaboration that occurred among ophthalmologists, optometrists, general practitioners and representatives of the Nova Scotia Department of Health with the aim of developing an integrated patient-focused multidisciplinary framework for vision care delivery. RESULTS: The process of collaborative negotiation among the four groups resulted in the development of multidisciplinary algorithms for the screening of patients with diabetes mellitus and the treatment of those presenting with a red eye. INTERPRETATION: Professional scope of practice has always been a contentious issue among health care professions. However, where parties agree to work within an atmosphere of respect and to accept guidance in areas of disagreement from a third party respected by all, compromise is possible. The result was the development of two vision care algorithms and ongoing efforts on the development of other algorithms.

Algorithms↗
PubMed2004

Enhancing vision care integration: 2. Implementation of practice algorithms.

BACKGROUND: Appropriate access to the best quality of vision care is enhanced when patients receive eye care services from the right professional, at the right time, and in the right place. In the preceding article the authors describe the development of two patient-centred vision care algorithms for the multidisciplinary management of diabetic retinopathy and red eye. Subsequently, a questionnaire survey was done to determine ophthalmologist, optometrist and general practitioner (GP) familiarity with and acceptance of the vision care algorithms. METHODS: The survey was conducted in the summer of 2001 among all ophthalmologists, optometrists and GPs registered with their respective professional body in Nova Scotia to assess their knowledge and acceptance of the diabetes mellitus and red eye algorithms. They were also asked to indicate their preferred method(s) of education and dissemination regarding these and future algorithms. RESULTS: Of the 740 practising GPs in Nova Scotia, 188 completed the questionnaire, for a response rate of 25.4%. The corresponding figures for optometrists and ophthalmologists were 73.6% (53/72) and 43.5% (20/46) respectively. Most of all three types of clinicians practise in Halifax County. More than 80% of the optometrists and ophthalmologists were aware of the algorithms, but less than 50% of the GPs were aware of them. A large majority of respondents in all three groups (77% to 98%) indicated that they were comfortable using the diabetes and red eye algorithms as presented. INTERPRETATION: Ophthalmologists, optometrists and GPs indicated an understanding of and willingness to use the diabetes and red eye algorithms. However, they were not unanimous regarding the choice of implementation method. Therefore, six different strategies for implementing the vision care algorithms are currently being used and are described in the paper.

Algorithms↗
PubMedDate not supplied

The rarity of Charles Bonnet syndrome.

Charles Bonnet syndrome (CBS) is characterized by complex visual hallucinations in otherwise psychologically normal people. Estimates of the prevalence of CBS in different samples vary from a small percentage (around 1%), to a relatively large percentage (about 10%). The purpose of the present study is to determine whether CBS is rare or not. One-thousand ophthalmologic and optometric outpatients at a university hospital were consecutively screened by a questionnaire to identify patients possibly experiencing visual hallucinations. The mean corrected visual acuity in the best eye was 1.1. Those who positively responded to the questionnaire were further investigated to determine whether their symptoms were consistent with CBS. As a result, the prevalence of CBS was 0.5% (5/1000). In subclass analyses, the prevalence was 3 of 372 (0.8%) in the low vision group, 2 of 346 (0.6%) in the elderly, and 1 of 120 (0.8%) in both conditions. These were not significantly different from each other or from the overall prevalence (0.5%). This low prevalence of CBS in our subjects may be due to their relatively good visual acuity because previous studies with high prevalence of CBS investigated patients with a visual acuity of less than 0.3. The prevalence of CBS may be low in patients with these particular characteristics, and this syndrome seems to be rare in even ophthalmologic and optometric patients if they do not have seriously low vision. Further studies are needed to investigate the prevalence of CBS in general population.

Adult↗
PubMed2001

Making sense of refractive surgery in 2001: why, when, for whom, and by whom?

Surgical alteration of the focusing or refractive properties of the eye has been performed on millions of patients. An array of procedures to correct myopia, hyperopia, astigmatism, and presbyopia have been introduced over the past 25 years with varying degrees of success. Improved technology has increased patient and physician satisfaction and enthusiasm. Currently available surgical procedures can be categorized as incisional, surface-altering, lamellar, and intraocular. The choice of procedure depends on individual patient indications and contraindications based on results of ocular examinations, eg, corneal pachymetry to measure corneal thickness, keratometry to measure the corneal curvature, basal tear secretory rate, and dark-adapted pupil size. The postoperative uncorrected visual acuity depends, in large part, on the quality of the preoperative evaluation and refraction. Before scheduling a patient for surgery, the ophthalmologist must ensure that the patient understands the potential risks of the procedure and has realistic expectations for the postoperative level and quality of uncorrected visual acuity. Postoperative complications include corneal flap displacement, undercorrection and overcorrection, and epithelial ingrowth under the corneal flap and inflammatory keratitis. Postoperative dry eye, infection, and inflammation are usually treated medically. Ongoing technological innovations to customize the surgical approach to an individual patient's eye continue to improve outcomes.

Astigmatism↗
PubMed2001

Isolated short-wavelength sensitive cones can mediate a reflex accommodation response.

Both long- and middle-wavelength sensitive cones mediate the reflex accommodation signal but the contribution from the short-wavelength sensitive cones is unknown. A short-wavelength sensitive cone contribution could extend the range of the signed defocus signal from chromatic aberration. The aim was to determine whether isolated short-wavelength sensitive cones mediate reflex accommodation independently of long- and middle-wavelength sensitive cones. Accommodation was monitored continuously (eight subjects) to a sine-wave grating (3 cpd; 0.53 contrast) moving with a sum of sines motion in a Badal optometer. Two illumination conditions were used: a 'blue' condition that isolated short-wavelength sensitive cones, and a 'white' control condition that stimulated all three cone types. Of the eight subjects, two responded equally in the 'white' and 'blue' condition, four gave reduced responses in the 'blue' condition and two failed to respond in both conditions. The mean response in the 'blue' condition was reduced by 50% compared to the 'white' condition. Further analysis indicated that four of the eight subjects gave responses that were considerably greater than noise (S.D.>1.82) when short-wavelength sensitive cones were isolated. Some subjects can accommodate using only S-cones.

Accommodation, Ocular↗
PubMed2003

Wavelength dependence of the optomotor response in zebrafish (Danio rerio).

The action spectrum of motion detection in zebrafish (Danio rerio) was measured using the optomotor response in the light adapted state. The function has a single maximum at 550-600 nm, and is similar to the spectral sensitivity function of the L-cone type in the mid and long wavelength range. At shorter wavelengths the values of three of the five fish tested are lower. As in goldfish [Vis. Res. 36 (1996) 4025], the result indicates a dominance of the L-cone type with an inhibitory influence of M- or S-cones. Experiments with a red/green striped cylinder showed that the optomotor response was at minimum whenever the L-cone type was not modulated by the moving pattern. This demonstrates that motion vision in zebrafish is "color blind", using mainly one of the four cone types probably involved in color vision.

Animals↗
PubMed1997

Salient features of Munsell colour space as a function of monolexemic naming and response latencies.

This study provides a replication of Boynton and Olson's (1990) work (Vision Research, 30, pp. 1311-1317), but using a more extensive model of colour space--Munsell as distinct from OSA-UCS. It involved 20 subjects in a total of 17,840 observations of 446 colours, in which monolexemic naming and response times were recorded. The results clearly differentiate between basic and non,basic colour categories using measures of consistency, consensus and response time. While the results are equivocal in distinguishing between the so-called "landmark" and "other basic colours", they are unequivocal in confirming the salience of the eleven basic colour categories initially proposed by Berlin and Kay [(1969) Basic colour terms: their universality and evolution, Berkeley, CA: University of California Press], and, in so doing, reinforce their perceptual significance and probable physiological basis. The results also reveal differences in non-basic colour naming that further confirm the special status of the basic colour categories and their role in categorical colour perception.

Adolescent↗
PubMed1997

Accommodation without feedback suggests directional signals specify ocular focus.

Accommodation was monitored continuously under open-loop conditions while subjects viewed a sinusoidally oscillating sine-wave grating (0.2 Hz; +/- 1 D; 2.7 c/d; 0.56 contrast) in a Badal optometer. The target was illuminated by monochromatic light (590 nm) or white light (3000 K) with longitudinal chromatic aberration (LCA) normal, doubled, neutralized and reversed. Subjects (12) accommodated well in white light with LCA normal and doubled (mean gains = 0.85 and 0.94), gain was reduced in the neutralized condition (0.54), in monochromatic light (0.43), and especially when LCA was reversed (0.30). The results suggest that accommodation responds to changes in the relative contrast of spectral components of the retinal image and perhaps to the vergence of light.

Accommodation, Ocular↗
PubMed1998

Static aspects of accommodation: age and presbyopia.

Although the progressive reduction in accommodative amplitude with increased age is well documented, little is known about several other aspects of static or steady-state accommodation to provide a comprehensive assessment of changes related to age and presbyopia. Static components of accommodation (tonic accommodation, depth-of-focus, slope of the stimulus/response function, and accommodative controller gain) were assessed objectively using an infrared (IR) optometer in 30 human subjects aged 21-50 years; depth-of-focus was also determined psychophysically as was accommodative amplitude. Tonic accommodation and the amplitude of accommodation decreased with increased age, whereas the subjective depth-of-focus increased; the other parameters remained unchanged. The decrease in tonic accommodation and amplitude of accommodation was attributed to biomechanical factors, whereas the increase in subjective depth-of-focus was believed to result from increased tolerance to defocus related to the gradual onset of presbyopia. Constancy of the objective depth-of-focus suggested absence of age effects on the neurologic control of reflex accommodation, whereas the lack of systematic change in slope and controller gain provided support for the Hess-Gullstrand theory of accommodation and presbyopia.

Accommodation, Ocular↗
PubMed1998

An infrared eccentric photo-optometer.

An objective infrared optometer has been designed, based on the optical principles of eccentric photorefraction. A CCD camera with an eccentric infrared light source images the subject's pupil through a Badal optometer. The slope of the light distribution across the pupil is continuously recorded. Accommodative state is measured by moving the camera behind the Badal lens until the slope is zero. This position corresponds to the case where the camera is conjugate with the retina of the observer. In this Badal optometer, the irradiance of light at the pupil plane, the sensitivity of the photorefractor, and the focal setting of the camera lens remain constant for all positions of the camera from the eye. The repeatability of a single measure of refractive state in a cyclopleged eye was less than 0.05 D. Static accommodative responses taken from 3 subjects in both closed and open loop conditions provided expected stimulus/response measures. The instrument can also be adapted to measure dynamic accommodation.

Accommodation, Ocular↗
PubMed1998

Retinal image quality in the human eye as a function of the accommodation.

The changes in the retinal image quality with accommodation in the human eye were studied by using a near-infrared double-pass apparatus. A slightly better modulation transfer function (MTF) in the unaccommodated eye with respect to the accommodated eye was found when using an artificial pupil with a fixed diameter. The technique allows the estimation of the MTF of the accommodated eye discounting the effect of the accommodative defocus error. Most of the reduction found in the MTF with accommodation could be explained in terms of the accommodative defocusing error. However, the shape of the retinal images clearly changes with accommodation, indicating that other aberrations are also altered with accommodation. In general, the double-pass image for the accommodated eye tends to be more symmetric than that of the unaccommodated eye. This is probably due to either a decrease in the amount of coma-like aberrations with accommodation or to an increase of other symmetric aberrations, such as defocus or spherical aberration, that hide the asymmetries present in the retinal image of the unaccommodated eye.

Accommodation, Ocular↗
PubMed1981

Manpower studies for the United States. Part II. Demand for eye care. A public opinion poll based upon a Gallup poll survey.

This is the second in the series of Ophthalmology Manpower Studies. Part I presented estimates of disease prevalence and incidence, the average amount of time required to care for such conditions, and based on that information, the total hours of ophthalmological services required to care for all the projected need in the population. Using different estimates of the average number of hours worked per year per ophthalmologist (based on a 35, 40 and 48 hours/week in patient care), estimates of the total number of ophthalmologists required were calculated. This method is basically similar to the method later adopted by the Graduate Medical Education National Advisory Committee (GMENAC) to arrive at estimates of hours of ophthalmological services required for 1990. However, instead of using all the need present in the population, the GMENAC panel chose to use an "adjusted-needs based" model as a compromise between total need and actual utilization, the former being an overestimation and the latter being an underestimation since it is in part a function of the barriers to medical care. Since some of these barriers to medical care include informational factors, as well as availability and accessibility, this study was undertaken to assess the utilization of these services and the adequacy of present ophthalmological manpower in the opinion of the consumer. Also, since the consumer's choice or behavior depends on being informed about the differences between optometrists and ophthalmologists, such knowledge was assessed and the responses further evaluated after explanatory statements were made to the responders.

Adolescent↗