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Biomedical subjects

D O Mutti

Publications and source records attributed to D O Mutti.

At least 19 recordsLinked to original sources
PubMed1999

Cycloplegia in African-American children.

PURPOSE: The selection of a cycloplegic agent depends on the desired outcome, the characteristics of the patient receiving the drug, and the associated risks. The Orinda Longitudinal Study of Myopia (OLSM) has used 1% tropicamide to assess the ocular components and cycloplegic refractions in a large cohort of predominantly Caucasian children. Although tropicamide has provided adequate cycloplegia and mydriasis for the OLSM cohort, conventional clinical wisdom and scientific investigations have suggested that tropicamide might not produce adequate cycloplegia and mydriasis for subjects with darker iris pigmentation. In this study one drop of 1% tropicamide followed by one drop of 1% cyclopentolate was used to determine their effectiveness in producing adequate cycloplegia and mydriasis for cycloplegic refraction and ocular component measurements in a group of African-American children. METHODS: Nineteen children [age range 5.5 to 15.6 years, mean 8.4 years +/- (SD) 2.5 years] were tested at Family HealthCare of Alabama, Eutaw, AL. Their accommodative responses were measured using a Canon R-1 autorefractor prior to and at 30, 45, and 60 min after instillation of one drop of 0.5% proparacaine, 1% tropicamide (Mydriacyl), and 1% cyclopentolate (Cyclogyl) in both eyes. A target of 20/155 letters in a 4x4 grid positioned behind a +6.50 diopter (D) Badal lens provided accommodative stimuli of 1.00 D, 2.00 D, and 4.00 D. RESULTS: All results are presented as mean +/-1 SD. Pupils, measured from video frames, dilated rapidly and maximally at 30 min after instillation of eye drops (7.3+/-0.5 mm) Predilation, the mean accommodative responses were 0.17+/-0.29 D for the 1.00 D stimulus, 1.01+/-0.40 D for the 2.00 D stimulus, and 2.77+/-0.74 for the 4.00 D stimulus. At 30 min after drop instillation, the responses were 0.07+/-0.14 D for the 1.00 D stimulus, 0.36+/-0.35 D for the 2.00 D stimulus, and 0.77+/-0.61 for the 4.00 D stimulus. Results were very similar at 45 and 60 min after drop instillation. CONCLUSIONS: Combining 1% tropicamide and 1% cyclopentolate was very effective in providing both cycloplegia and mydriasis adequate for ocular biometry and cycloplegic refractions 30 min after drop instillation in African-American children.

Accommodation, Ocular↗
PubMed1999

Tonic accommodation, age, and refractive error in children.

PURPOSE: An association between tonic accommodation, the resting accommodative position of the eye in the absence of a visually compelling stimulus, and refractive error has been reported in adults and children. In general, myopes have the lowest (or least myopic) levels of tonic accommodation. The purpose in assessing tonic accommodation was to evaluate it as a predictor of onset of myopia. METHODS: Tonic accommodation was measured in children enrolled in the Orinda Longitudinal Study of Myopia using an infrared autorefractor (model R-1; Canon, Lake Success, NY) while children viewed an empty lit field or a dark field with a fixation spot projected in Maxwellian view. Children aged 6 to 15 years were measured from 1991 through 1994 (n = 714, 766, 771, and 790 during the 4 years, successively). Autorefraction provided refractive error and tonic accommodation data, and videophakometry measured crystalline lens curvatures. RESULTS: Comparison of the two methods for measuring tonic accommodation shows a significant effect of age across all years of testing, with the lit empty-field test condition yielding higher levels of tonic accommodation compared with the dark-field test condition in children aged 6 through 11 years. For data collected in 1994, mean (+/-SD) tonic accommodation values for the lit empty-field condition were significantly lower in myopes, intermediate in emmetropes, and highest in hyperopes (1.02 +/- 1.18 D, 1.92 +/- 1.59 D, and 2.25 +/- 1.78 D, respectively; Kruskal-Wallis test, P < 0.001; between-group testing shows each group is different from the other two). Age, refractive error, and Gullstrand lens power were significant terms in a multiple regression model of tonic accommodation (R2 = 0.18 for 1994 data). Lower levels of tonic accommodation for children entering the study in the first or third grades were not associated with an increased risk of the onset of myopia, whether measured in the lit empty-field test condition (relative risk = 0.90; 95% confidence interval = 0.75, 1.08), or the dark-field test condition (relative risk = 0.83; 95% confidence interval = 0.60, 1.14). CONCLUSIONS: This is the first study to document an association between age and tonic accommodation. The known association between tonic accommodation and refractive error was confirmed and it was shown that an ocular component, Gullstrand lens power, also contributed to the tonic accommodation level. There does not seem to be an increased risk of onset of juvenile myopia associated with tonic accommodation.

Accommodation, Ocular↗
PubMed1998

The effect of continuous light on refractive error and the ocular components of the rat.

Phototoxic induced degeneration of the rat retina is a well-documented phenomenon resulting in losses of photoreceptors and their cell bodies, and an overall retinal thinning. This process may serve as a test of the hypothesis that the retinoscopic reflex originates from the inner limiting membrane of the retina. Retinal thinning should produce myopia in the absence of any other ocular component changes in a stable, mature eye if the inner limiting membrane model is correct. Phototoxic retinal degeneration was induced in 10 albino rats by exposure to 19 days of continuous light (1,800 cd m-2). Another 10 albino rats exposed to 12-hr on/12-hr off cycled light served as controls. Before and after the exposure to constant light, measures were made of refractive state by cycloplegic retinoscopy, corneal curvature and lens curvature by Purkinje image photography, and axial length of the globe by A-scan ultrasonography. Comparing pre- to post-exposure values, phototoxic degeneration resulted in a mean (+/- S.D.) myopic shift of -5.10 +/- 2.12 D (P < 0.002). The corneal curvature also steepened significantly (0.17 +/- 0.11 mm, equivalent to -6.0 D; P < 0.004), while the posterior curvature of the crystalline lens flattened by 0.21 +/- 0.22 equivalent mm (P < 0.027), and the axial length shortened by 0.11 +/- 0.11 equivalent mm (all tests Wilcoxon signed-rank; P < 0.025). Phototoxic rats underwent a mean retinal thinning of 49.6 mu compared to controls (Kruskal-Wallis test; P < 0.0008). No refractive or ocular parameters changed significantly in the controls. Phototoxic degeneration in the rat has optical consequences beyond simple retinal thinning. The size of the eye and the curvature of refractive surfaces can be altered in a mature eye well after the completion of development. The multiple changes which occur prevent phototoxic retinal thinning from serving as a test of the inner limiting membrane model for retinoscopic reflections.

Animals↗
PubMed1998

Development of phoria in children.

BACKGROUND: Although the prevalence of phoria in adults is well documented, data are scarce on phoria in children. We present results using modified clinical technique vision screening and data from the Orinda Longitudinal Study of Myopia on a large, population-based sample of nonstrabismic children to document the prevalence of phoria with age. METHODS: We collected cross-sectional (N = 1495) and longitudinal (N = 469) data. Phoria data were collected by cover tests administered by one observer who subjectively classified phoria as orthophoria, esophoria, or exophoria in 2 delta steps. RESULTS: Ninety-seven percent of the children were orthophoric at distance, and there were no significant changes with age. Near phoria showed a more normal distribution, with a 10.8% decrease in the prevalence of exophoria (from 31.8 to 21.0%) and a 5.5% increase in the prevalence of esophoria (from 6.7 to 12.2%) between kindergarten and fifth grade. CONCLUSIONS: Children are typically orthophoric or exophoric at near, but convergent shifts occur with age.

Child↗
PubMed1998

Optical and structural development of the crystalline lens in childhood.

PURPOSE: To document the development of key optical and structural parameters of the crystalline lens throughout childhood and examine possible mechanisms by which lens power remains coordinated with the growth of the eye to maintain emmetropia. METHODS: Using cycloplegic autorefraction, video-based phakometry, and ultrasonography, the authors measured refractive error and crystalline lens parameters in 994 children in the first through eighth grades, who participated in the Orinda Longitudinal Study of Myopia, between one and five times from 1989 through 1993. Polynomial growth curves were fit to the data by maximum likelihood estimation. The average annual rates of change in each parameter from each subject's longitudinal data were also estimated. RESULTS: The lens radii of curvature flattened throughout childhood, yet decreases in lens equivalent power stopped after 10 years of age. This indicates that the refractive index of the lens increased during later childhood. Lens thinning in early childhood also ceased after 10 years of age. The spherical volume of the lens showed no appreciable net increase, but the axial length of the eye continued to grow throughout childhood. The prevalence of myopia in our data increased sharply at age 10 years, reaching 21.3% by the age of 14 years. CONCLUSIONS: Concurrent thinning and flattening of the crystalline lens imply that the lens is mechanically stretched by the equatorial growth of the eye during childhood. Changes in the patterns of lens development near the age of 10 years, concurrent with the onset of myopia, suggest that forces arise which interfere with equatorial growth. Such forces might diminish the decreases in lens power and amplify axial elongation to promote myopia.

Adolescent↗
PubMed1998

Retinoscopy.

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Diagnostic Techniques, Ophthalmological↗
PubMed1997

The artifact of retinoscopy revisited: comparison of refractive error measured by retinoscopy and visual evoked potential in the rat.

PURPOSE: The validity of retinoscopy in small eyes has not been clearly established due to uncertainty regarding the source of the ocular reflections assessed during this procedure. A widely cited model which proposes that their origin is the inner limiting membrane of the retina was evaluated in the rat by comparing refractive errors measured by retinoscopy to those measured by visual evoked potentials (VEPs). METHODS: Ten rats were refracted both by cycloplegic streak retinoscopy and by VEP while viewing 0.05 to 0.15 cpd square-wave gratings-reversed at 1.875 Hz. Spherical aberration of the rat eye was assessed as a potentially confounding variable in VEP refraction by sequential retinoscopic refractions across the rat's natural pupil through a 1.5-mm pinhole. RESULTS: All animals were moderately to highly hyperopic by both methods (range = +4.5 to +18.5 D). Spherical aberration was minimal (median = 3.5 D of overcorrected aberration). The median difference between retinoscopic refractions and those by VEP was not significant (+1.94 D more hyperopia by retinoscopy; p = 0.062, Wilcoxon signed rank) but was significantly less than the +9.64 D difference predicted by an inner limiting membrane model (upper 95% limit = +3.76 D). CONCLUSION: This suggests that the origin of the retinoscopic reflex is located in the outer retina rather than at the inner limiting membrane. Correction factors for retinoscopy in small eyes may be smaller than previously assumed.

Animals↗
PubMed1997

Comparison of corneal versus through-the-lid A-scan ultrasound biometry.

BACKGROUND: Accurate ultrasonography data on axial ocular dimensions in infants and toddlers are essential for understanding ocular development. Conventional methods using corneal contact with topical anesthesia but without sedation are not feasible for most of these patients. We evaluate an alternative method which places the probe on the closed eyelid. METHODS: We compared A-scan ultrasound biometry measurements taken with the probe directly on the cornea with those with the probe on the closed eyelid on the right eye of 35 young adult subjects. RESULTS: There was no significant difference between methods for mean anterior chamber depth (corneal = 3.83 mm, lid = 3.87 mm, p = 0.13, paired t-test). The mean lens thickness (corneal = 3.63 mm, lid = 3.75 mm, p = 0.0001, paired t-test) and mean vitreous chamber depth (corneal = 17.50 mm, lid = 17.68 mm, p = 0.0440, paired t-test) were significantly different. CONCLUSION: Ultrasonography through the closed eyelid appears to be a viable method with acceptable validity compared with corneal ultrasound. Poorer agreement for lens thickness and vitreous chamber depth may be undesirable, but these data should be useful for planning future studies of infants and toddlers.

Adult↗
PubMed1997

Effect of optical defocus on visual acuity in dogs.

OBJECTIVE: To determine the effect of optical defocus (such as what develops in spontaneous myopia and subsequent to cataract extraction) on visual acuity in dogs. ANIMALS: 3 young adult male Beagles. PROCEDURE: The effect of optical defocus on visual acuity was determined by sweep visual evoked potential, using a within-subjects/repeated measures design in which each dog served as its own control. Dogs were positioned so that the eye being tested was 60 cm in front of the video display, and the target was centered on the area centralis. To create ametropia relative to the video screen, a series of concave and convex spherical lenses were placed 1 cm in front of the eye, and sweep visual evoked potential acuities were obtained. RESULTS: Maximal acuity was 7.0 to 9.5 cycles/degree. Defocusing by 2.0 diopters reduces Beagle grating acuity approximately 1 octave. Mimicking aphakia resulted in a marked depression of acuity to 0.7 cycles/degree or less. CONCLUSIONS: Even mild degrees of ametropia have appreciable impact on the resolving power of the canine visual system. CLINICAL RELEVANCE: Spontaneous myopia is encountered in dogs and may be associated with impaired visual performance attributable to a reduction in visual acuity. Previous reports indicate the possibility of myopia in dogs to have a heritable component. On the basis of our results, refractive correction of aphakia is advisable, and refractive screening of dogs with demanding visual tasks (eg, service dogs, field-trial Labrador Retrievers) is recommended.

Animals↗
PubMed1996

Validity of surveys reporting myopia, astigmatism, and presbyopia.

Validation of surveys is an important step in establishing the usefulness of questionnaires for gathering information in clinical studies. Often in large studies of refractive error, it is not possible to examine and refract all subjects and their relatives. Therefore, we used 3 methods to evaluate 112 consecutive clinic patients' abilities to report myopia through a survey: (1) The Lay Terms Method asks: "are you nearsighted?"; (2) The Direct Method asks: "are you myopic?"; and (3) The Indirect Method uses a series of questions about the use of eyeglasses and age at first dispensing. Patient responses to the survey before examination were compared to subjective refraction findings at the completion of the eye examination. The Lay Terms Method had the highest sensitivity (0.98) but poor specificity (0.48), and the Direct Method yielded the highest specificity (0.83) but poor sensitivity (0.54). The rate of nonresponse ("don't know") was high (25.9 and 46.4% for the Lay Term and Direct Methods, respectively). The Indirect Method gave both high sensitivity and specificity (0.76 and 0.74, respectively), and only an 8.9% don't know response rate. The survey method that reports the presence or absence of myopia with the best balance of sensitivity and specificity and fewest don't know responses is the Indirect Method, suggesting it is the most suitable of our three approaches for use in clinical studies.

Adolescent↗
PubMed1996

Corneal changes in schoolchildren.

Videokeratography (TMS-1) data from the right eyes of 788 children between the ages of 6 and 14 years, examined in 1994 as part of the Orinda Longitudinal Study of Myopia, were analyzed using the Fast Fourier Transform (FFT) to quantify corneal power, toricity, and toricity axis. Cross-sectional analysis showed no statistically significant age trend for these parameters. Conversely, longitudinal analysis of data for 387 of these children, first measured in 1991, showed a statistically significant decrease in corneal power. Corneal toricity did not change significantly over this 3-year period, although there was a minute but statistically significant clockwise axis shift. From this we conclude that in the elementary and junior high school years-during which period axial length is known to increase-corneal flattening continues, but corneal toricity is stable.

Adolescent↗
PubMed1996

Crystalline lens parameters in infancy.

Despite the importance of lens power to ocular development, few data are available regarding infant crystalline lens parameters. Lens and corneal radii of curvature were measured in the horizontal meridian using a video-based keratophakometer, and refractive error was measured by cycloplegic retinoscopy in 19 out of 27 infants ranging in age from 3 to 18 months. The median refractive error was +1.50 D, and the median corneal power was 43.5 D. Using previously reported values for axial ocular dimensions, the median anterior and posterior lens radii of curvature were 8.7 and 5.6 mm, respectively, both substantially flatter than infant schematic eye values. The median equivalent refractive index of the lens was 1.49, considerably higher than previous reported schematic values for infants or children. There was a significant reduction in hyperopia with age (r = -0.47, P = 0.043), but no age-related trends in lens or corneal radii of curvature, suggesting that calculated values for lens power and equivalent index may undergo substantial decline with age during early childhood development as axial length increases. Most of the decrease in lens power (75%) may be due to decreases in equivalent index rather than to flattening of the surface radii of curvature. Videophakometry appears to be a feasible and useful technique for documenting the role of the crystalline lens in infant ocular development.

Anthropometry↗
PubMed1996

Is computer use a risk factor for myopia?

BACKGROUND: Many patients who become myopic or who undergo increases in myopia as adults have concerns about whether the use of video display terminals (VDTs) contributes to these changes in refractive error. This paper is an overview of the current literature on topics concerning VDTs and factors related to proposed etiologies for myopia. METHODS: Selected literature is reviewed on the relationship between VDTs and asthenopia, fatigue, accommodation, and vergence. Clinical studies of myopic progression and transient myopia among VDT users are considered, as is television viewing as a risk factor for juvenile myopia. RESULTS/CONCLUSIONS: Reports of asthenopia are common with VDT use by a factor of 1.4 to 1.5, compared to conventional office work. Questions of comparability remain between VDT users and nonusers with respect to confounding variables such as the number of work hours. Proofreading on a VDT appears to be less efficient than using printed copy. Despite screen flicker and reflections, the accommodative response appears to be accurate to a VDT. Transient, fatigue-induced changes in accommodation and vergence may occur after work with VDTs. Despite these near point changes, there is no compelling evidence in the literature that suggests there is a significant increase in the risk of myopia onset or progression from the use of VDTs by adults compared to other forms of near work.

Accommodation, Ocular↗
PubMed1996

Factors influencing graft clarity.

Successful penetrating keratoplasty depends on both host- and donor-related factors. We compared the results of keratoplasty in a group with a wide range of donor ages to gauge the effect of donor age on graft success. We conducted a retrospective review of donor data, recipient age, preoperative diagnosis, and postoperative complications with respect to graft clarity at 24 months after surgery in 99 consecutive patients in an effort to determine the role of donor age in graft clarity. The only factors that we isolated that appeared to influence graft clarity at 24 months postoperatively were a preoperative diagnosis classified as inflammatory/traumatic and the occurrence of postoperative complications. There was no association between graft clarity and recipient age, donor age, death-to-preservation time, or preservation-to-surgery time.

Age Factors↗
PubMed1995

The utility of three predictors of childhood myopia: a Bayesian analysis.

Any treatment to prevent the onset of juvenile myopia will require predictive tests in order to determine which children should receive treatment. Three risk factors for myopia were evaluated for their ability to predict myopia: (a) refraction at school entry; (b) refraction in infancy; and (c) parental history of myopia. Bayes' theorem was used to estimate these conditional probabilities. Refraction at school entry had twice the power to predict myopia (probability of juvenile myopia given the child is near emmetropia at school entry = 0.53) compared to either infant refraction (0.21-0.28) or parental myopia (0.20-0.25). While a history of any parent having myopia had the highest test sensitivity (probability of a positive family history of myopia given juvenile myopia in the child = 0.90) and refraction at school entry the highest test specificity (probability of more hyperopia than +0.50 D at school entry given no juvenile myopia = 0.91), none of these three factors had high values for both sensitivity and specificity. Further work is required to develop a battery of tests which could predict the onset of juvenile myopia with both adequate sensitivity and specificity.

Age Factors↗