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Biomedical subjects

D A Goss

Publications and source records attributed to D A Goss.

At least 37 records · Page 2Linked to original sources
PubMed1996

A comparison of three subjective tests for astigmatism and their interexaminer reliabilities.

BACKGROUND: Astigmatism is a common cause of blurred vision and asthenopia. Several different tests for the measurement of astigmatism have been described in the literature, but there are few studies that have compared the results of various tests. METHODS: The results of three astigmatism tests performed on 40 subjects by two examiners were compared. Two of the tests, the Jackson cross cylinder (JCC) and the Humphriss immediate contrast (HIC), utilized distance targets; one test, the Pratt test, involved a near target. RESULTS: The mean differences between all tests were less than 0.25D. There was a slight tendency for higher cylinder power to be found on the Pratt test. The three tests agreed within +/- 0.25D on cylinder power 80 to 98 percent of the time and within 10 degrees of cylinder axis 85 to 98 percent of the time. Interexaminer reliability showed mean differences less than 0.12D for each of the three tests, agreement within +/- 0.25D on cylinder power 88 to 90 percent of the time and within 10 degrees on cylinder axis 85 to 93 percent of the time. CONCLUSIONS: The results suggested that any of the three techniques could be substituted for another for astigmatism testing. On theoretical grounds, a binocular refraction method for cylinder axis determination, such as the HIC, is advisable for patients with cyclophorias and significant amounts of astigmatism. The results showed good reliability for each of the three methods.

Adolescent↗
PubMed1996

Reliability of refraction--a literature review.

BACKGROUND: The repeatability (reliability) of methods of measuring refractive error is an important consideration in patient management decisions and in research design and interpretation. Several papers on reliability of refraction have appeared in the literature. METHODS: Studies on the reliability of conventional clinical refraction, including repeated refractions by the same examiner (intraexaminer reliability) and comparisons of the results obtained by different examiners (interexaminer reliability), were reviewed. Studies comparing the results obtained by autorefractors and conventional subjective refraction were also reviewed. RESULTS: The intraexaminer reliability and interexaminer reliability of subjective refraction in most studies were close to 80 percent agreement within +/- 0.25D and 95 percent agreement within +/- 0.50D for spherical equivalent, sphere power, and cylinder power. The reliability of most autorefractors is similar to the reliability of conventional subjective refraction. CONCLUSIONS: The results of the reliability studies support Bannon's 1977 conclusion that conventional subjective refraction is reliable within 0.25 to 0.50D. Studies comparing objective autorefractors and conventional subjective refraction indicate that these autorefractors are satisfactory for a preliminary refraction but are not satisfactory as substitutes for conventional subjective refraction.

Humans↗
PubMed1995

Retinal-image mediated ocular growth as a mechanism for juvenile onset myopia and for emmetropization. A literature review.

The very common ocular clinical ocular condition in children juvenile onset myopia results from axial elongation of the eye. In humans, some studies have found an association of myopia with greater levels of nearpoint activity and with differences in accommodation and convergence function. This paper reviews a variety of laboratory and clinical studies which are consistent with the hypothesis that retinal image defocus is biochemically transformed into an axial elongation expressed through increased posterior segment growth, and thus myopia. This paper also reviews theories of emmetropization, and classifies them as correlational, feedback, and combination. Evidence is presented to suggest that a combination theory, which combines both correlation of the ocular dioptric components and some feedback mechanism for growth of the eye, is the most correct. Current laboratory research suggests that quality and/or focus (defocus) of retinal imagery is involved in this feedback mechanism and that experimentally induced myopia might be enhanced, reduced or eliminated by pharmaceutical application. Direction of defocus may affect the rate of posterior segment growth, and thus the rate of ocular axial elongation.

Adolescent↗
PubMed1995

Clinical findings before the onset of myopia in youth. I. Ocular optical components.

PURPOSE: A study was conducted to identify variables that were different in children who were emmetropic and became myopic and in children who remained emmetropic. METHODS: A cohort of initially emmetropic children had eye and vision examinations at 6-month intervals for a period of 3 years. Ocular optical components were measured by keratometry and ultrasonography. Crystalline lens power was calculated using Bennett's formulas. RESULTS: There was a tendency for keratometer power of both principal meridians to be greater in the became-myopic group than in the remained-emmetropic group. Axial length to corneal radius (AL/CR) ratio was significantly greater in the became-myopic group than in the remained-emmetropic group. The variable with the highest sensitivity and specificity was the AL/CR ratio using the horizontal meridian corneal radius. CONCLUSIONS: Greater corneal powers and greater AL/CR ratios are risk factors for youth onset myopia.

Adolescent↗
PubMed1995

Comparison of fixation disparity curve variables measured with the Sheedy Disparometer and the Wesson Fixation Disparity Card.

BACKGROUND: Previous studies suggest differences in the fixation disparity curves obtained with the Sheedy Disparometer and the Wesson Fixation Disparity Card, the two most commonly used methods for measuring fixation disparity. In one study the investigators proposed that the differences do not exist for subgroups divided by phoria. The purpose of this paper is to try to clarify this issue by use of two large sets of data. METHODS: Dissociated phorias were measured by the von Graefe method. Fixation disparity curves were plotted using the Disparometer and the Wesson card. RESULTS: Type I fixation disparity curves were most common with the Wesson card. Type II curves were found more often with the Disparometer than with the Wesson card. The x-intercepts were shifted in the base-in (BI) direction with the Wesson card compared to the Disparometer. The y-intercepts were shifted in the exo direction with the Wesson card compared to the Disparometer. The differences were statistically significant regardless of whether the dissociated phoria was exo or eso. The slope of the fixation disparity curve was steeper with the Wesson card than with the Disparometer. The difference was statistically significant for exophores but not for esophores. The differences between results obtained with the two instruments are not consistent from one subject to another as shown by high standard deviations of the differences. CONCLUSIONS: The fixation disparity curves measured with these two instruments are different. Fixation disparity parameters obtained from one of these instruments cannot be used with normative findings from the other.

Evaluation Studies as Topic↗
PubMed1994

Clinical and laboratory investigations of the relationship of accommodation and convergence function with refractive error. A literature review.

Studies of the relationship of clinical and laboratory measures of accommodation and convergence function with refractive error are reviewed. There are inconsistencies in results from study to study presumably due, in part, to methodological differences. However, some basic trends can be outlined. In studies in young adults, accommodation in darkness (dark focus), optical reflex accommodation, and proximally induced accommodation are less in myopes than in emmetropes and hyperopes. It also appears that nearpoint esophoria is associated with higher rates of myopia progression in children. Implications for myopia etiology are discussed.

Accommodation, Ocular↗
PubMed1994

Effect of spectacle correction on the progression of myopia in children--a literature review.

BACKGROUND: Methods used to attempt to control childhood myopia progression have included various types of spectacle correction. The most commonly studied technique has been the use of bifocal lenses. METHODS: The literature on the effects of bifocals, undercorrection, and part-time wear of spectacles on the rate of myopia progression in children was reviewed. RESULTS: The data available on undercorrection and part-time wear of spectacles is limited. There have been several studies on the effects of bifocals. Some studies reported no effect with bifocals, some studies reported reduced rates with bifocals, and some noted lower rates with bifocals may be associated with particular ocular or visual findings. CONCLUSIONS: Critical analysis of the literature suggests that when the nearpoint phoria is eso, greater rates of progression occur, and that some degree of myopia control may be established by shifting the phoria into the normal range by spectacle corrections such as bifocals.

Child↗
PubMed1993

The effect of caffeine on the accommodative response/accommodative stimulus function and on the response AC/A ratio.

Using a phoro-accommodometer, accommodation and convergence responses were measured for 17 experimental subjects before and after they ingested 200 mg caffeine. For 16 control subjects accommodation and convergence responses were determined at two test sessions separated by 45 min. For the experimental group, the accommodative response/accommodative stimulus (Ar/As) slope increased 0.05 D/D after ingestion of caffeine, and the response AC/A ratio decreased 3.05 delta/D. The y-intercept of the convergence response/accommodative response increased by 3.7 delta in the experimental group. These changes were statistically significant. For the control group, the differences in Ar/As slope, response AC/A ratio, and convergence response/accommodative response y-intercept between first and second test sessions were not statistically significant.

Accommodation, Ocular↗
PubMed1992

Optic nerve crescents and refractive error.

In this paper we discuss whether the presence of an optic nerve crescent might affect the way in which axial length and corneal curvature interact to determine refractive error. Subjective refraction, keratometry, measurement of body height, axial length of the eye, and stereophotography of the optic nerves were performed on 224 subjects, 8- to 25-years-old. Photographs were examined under magnification; optic nerve crescents, if present, were measured in the horizontal dimension. Those measurements were then corrected for magnification due to the eye and the camera. Logistic regression analysis suggested that male gender and myopic refractive error were most directly associated with the presence of a large crescent, whereas axial length, age, and horizontal keratometry reading were less directly associated with the presence of a crescent. The relation between axial length and refractive error differed among those with large crescents compared to those with small or no crescents. Simple regression showed that, for those with a crescent at least 0.2-mm wide, a 1-mm greater axial length was associated with, on the average, 1.26 D of myopia. For those with smaller or no crescents, a 1-mm greater axial length was associated with only 0.66 D of myopia. This difference was statistically significant at the 0.02 level of confidence.

Adolescent↗
PubMed1992

A case of monocular triplopia of lenticular origin.

A 70-year-old male experienced unilateral monocular triplopia of lenticular origin. The images formed a nearly equilateral triangle and were equally clear. It was noted that the images were formed by sections of the crystalline lens whose borders were parallel to the orientation of the anterior Y-sutures.

Aged↗
PubMed1992

Clinical accommodation testing.

Clinical accommodation tests can theoretically be categorized into five different types: 1) tests of accommodative amplitude, 2) tests of relative accommodation, 3) tests of accommodative facility, 4) tests measuring lag of accommodation, and 5) tests finding the dioptric accommodative stimulus at which dioptric stimulus and response levels are equal. Studies of the interrelation of accommodation tests indicate that a complete evaluation of accommodative disorders in nonpresbyopes should include at least one test from four of the five categories. Measurements of accommodative amplitude, lag, and facility, and relative accommodation should be included. Results from the fifth type of test listed above correlate well with lag of accommodation. Recent research is bringing greater acceptance and standardization to accommodative facility testing.

Accommodation, Ocular↗
PubMed1991

Clinical accommodation and heterophoria findings preceding juvenile onset of myopia.

This study was performed to test the hypothesis that accommodation and convergence differences precede the onset of myopia in children. Records of children who were emmetropic and became myopic (became myopic group) and children who remained emmetropic (remained emmetropic group) were collected from seven private optometry practices. The practices were located in Illinois, Iowa, Oklahoma, and Oregon. Near-point phorias and positive relative accommodation (PRA) findings were significantly different in the two groups by t-test. Negative relative accommodation (NRA) did not show a statistically significant difference in the two groups. Binocular cross-cylinder findings were shown by analysis of variance (ANOVA) to be significantly affected by group (became myopic vs. remained emmetropic) and by practice location. These results support the hypothesis that differences in accommodation and convergence function may be precursors of juvenile onset myopia.

Accommodation, Ocular↗
PubMed1991

Variation and correlation of clinical tests of accommodative function in a sample of school-age children.

Accommodative facility, lag of accommodation, accommodative response, and relative accommodation were measured in 244 school-age (7.9 to 15.9 years of age) children. The tests studied included monocular estimate method (MEM) dynamic retinoscopy, Nott dynamic retinoscopy, low neutral dynamic retinoscopy, the binocular cross cylinder test, lens accommodative rock (facility), distance (near-far) accommodative rock, negative relative accommodation (NRA), and positive relative accommodation (PRA). The mean, standard deviation, and range of test findings of each test are presented. Coefficients of correlation among the various tests are presented.

Accommodation, Ocular↗
PubMed1991

Variation and correlation of standard clinical phoropter tests of phorias, vergence ranges, and relative accommodation in a sample of school-age children.

This paper presents a study of standard clinical phoropter tests of dissociated phorias, fusional vergence ranges, and relative accommodation ranges in 244 school-age (7.9 to 15.9 years of age) children. The tests studied included von Graefe phorias and base-in and base-out fusional vergence ranges at both distance and near, as well as negative relative accommodation (NRA) and positive relative accommodation (PRA) tests. Coefficients of correlation among the various tests are presented. Means and correlations were similar to those previously reported for adult populations. Distributions of distance lateral phorias and some distance fusional vergence parameters were leptokurtic.

Accommodation, Ocular↗
PubMed1990

Refractive error, axial length, and height as a function of age in young myopes.

Classical studies suggest that growth of the eye as assessed by axial elongation ceases by 13 years of age. The subjects in these studies were mostly emmetropes. In contrast, the childhood progression of myopia continues to the middle to late teenage years. We collected cross-sectional data on refractive error, axial length, and height. Analysis of these data based on a linear regression model suggests that axial elongation continues later in myopes than the classical studies suggest. The age of cessation of axial elongation in myopes was earlier in females than in males. For both sexes, the ages of axial elongation cessation in myopes were similar to the ages of cessation of increases in height.

Adolescent↗
PubMed1990

Variables related to the rate of childhood myopia progression.

This study was undertaken to examine the relations between the rate of childhood myopia progression and variables available in patient records. Data were obtained from four private optometry practices and two university-based longitudinal studies. Subjects were myopes with a minimum number of refractions between the ages of 6 and 15 years. Spectacle prescription types included single-vision lenses with exact distance correction or slight undercorrection, bifocal lenses, and single-vision lenses with overcorrection. Rates of progression were determined by linear regression. Three analyses were conducted: (1) for all patients, analysis of variance of rate as a function of heterophoria through the habitual nearpoint correction, an index of the amount of myopia at the initial examination age, sex, and clinical location; (2) for patients with esophoria through the distance ametropia correction, analysis of variance of rate as a function of correction type (full correction or slight undercorrection vs. bifocals), amount of myopia at the initial examination age, sex, and location; and (3) for patients with orthophoria or exophoria with ametropia correction, analysis of variance of rate as a function of correction type, amount of myopia at the initial examination age, sex, and location. The index of amount of myopia at the initial examination age was a significant variable, as was location. Patients with nearpoint esophoria through their habitual nearpoint correction had greater rates than patients with nearpoint orthophoria or exophoria with the habitual correction. For patients with nearpoint esophoria through the distance refractive correction, rates were less with bifocals than with full correction or slight undercorrection.

Adolescent↗