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Results for “REFRACTIVE ERRORS”

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At least 19 recordsLinked to original sources

PubMed2000

[The history of correction of refractive errors: refractive surgery].

The evolution of particular methods of refractive surgery is presented including the origins of radial keratotomy, relaxing incisions, keartophakia, epiferatophakia and keratomileusis as well as recent adaptation of lasers for the surgical treatment of refractive error. Such famous persons as Barraquer, Sato, and Fidorov are discussed in particular. The history not only of great achievements but also of some of the false ideas which accompanied efforts to obtain the emmetropia is presented.

History, 20th Century↗

PubMed1989

Age differences in peripheral refractive error.

Refractive error was measured at 0 degrees to 40 degrees temporal to fixation in 10 young adults (M age = 26 years) and 10 older adults (M age = 63 years). Older adults exhibited a greater amount of sphere (i.e., overall) error, but no more so in the periphery than in the fovea. Although age differences were small, younger adults were found to exhibit more peripheral astigmatism than the older adults. Discrepancies between obtained results and those of Millodot (1985) may be attributed to the relationship between peripheral astigmatism and presenting refractive status. Alternatively, a two-mechanism model of age-related change in lens curvature is capable of accounting for across-study outcome differences. Recommendations are made concerning optimal viewing conditions for the study of age differences in visual perceptual processes.

Adult↗

PubMed2001

Aggregation of refractive error and 5-year changes in refractive error among families in the Beaver Dam Eye Study.

OBJECTIVE: To examine aggregation of refraction, myopia, hyperopia, and astigmatism, as well as the 5-year change in each of these measures, among adult family members. DESIGN: Geographically defined, population-based cohort study in Beaver Dam, Wis. Participants were all 43 to 84 years of age in 1988. Family relationships among participants of the study were identified through interviews. The main outcome measures were noncycloplegic refractions. Aggregation was assessed by Pearson correlations and odds ratios (ORs) that both members of a pair were affected. RESULTS: Age-adjusted sibling correlation of refraction was 0.37 and the OR for a sibling to be myopic was 4.18, whereas the OR for being hyperopic was 2.87 (all statistically significant, P<.05). Correlations and ORs for parent-child and cousin relationships were smaller, and those for spousal relationships were not significant. Correlations and ORs for cylinder power and astigmatism were not statistically significant for most relationships considered. There were no statistically significant correlations or ORs for changes in any measure of refractive error. CONCLUSIONS: The strong aggregation of refractive error, including myopia and hyperopia, among siblings along with weaker associations among parent-child and cousin pairs and no associations among spouses suggest a potential genetic influence on refractive error. There is no such suggestion for a genetic influence on the changes in refraction or in cylinder power and astigmatism.

Adult↗

PubMed1985

Intraocular lens powers used in the triple procedure. Effect on visual acuity and refractive error.

The refractive results of 43 consecutive triple procedures (transplant, cataract extraction, and lens implant) performed by one surgeon were analyzed. Twenty-one out of 43 eyes achieved refractive errors within 2 diopters (D) of emmetropia. The mean refractive error was -1.79 D, and the mean corneal astigmatic error was 2.75 D. Seventy percent of the eyes achieved 20/40 or better corrected acuity. Forty-four percent had 20/80 or better uncorrected acuity. Using the average postoperative keratometry readings from other recent transplant cases and an updated A constant in the SRK regression formula would have placed 39 of 43 eyes (91%) within 2 D of emmetropia with a mean refractive error of -0.07 D. The use of recent keratometry readings in a multiple regression formula is recommended to improve refractive results with the triple procedure.

Cataract Extraction↗

PubMed1995

Cost-effective screening of schoolchildren for refractive errors.

Uncorrected refractive errors are the main cause of severely impaired vision in India. This in itself indicates that there is a shortage of basic eye care services and spectacles, and too little public awareness of the need for them. A simple method for screening schoolchildren for refractive errors is described and the results are analysed. Evaluation of the materials used and the accuracy of the screening shows that this method can be used successfully by teachers.

Adolescent↗

PubMed1990

Effects of intraocular lens position errors on postoperative refractive error.

Previous theoretical attempts to predict the refractive effects of intraocular lens (IOL) misalignment have resulted in conflicting information. Discrepancies in both the potential magnitude and direction of the refractive changes exist in the literature. This paper provides a detailed description of the mathematical framework required to achieve a valid predictive model and a quantitative analysis of the effects of IOL positional errors. The effects of misalignment are shown to influence the spherical refractive component primarily. Astigmatism related to oblique incidence is generally small. Movement of the IOL away from the retina produces myopia, while movement toward the retina produces hyperopia. It is likely that longitudinal IOL positional errors are a principal component of postoperative refractive errors. Alignment errors, on the other hand, must have generally minor effects on refraction.

Astigmatism↗

PubMed1995

A population-based survey of the prevalence of refractive error in Malawi.

Refractive errors, particularly myopia, are a common problem in industrialized countries, but the impression exists that myopia may be relatively uncommon in non-industrialized societies. We conducted a population-based survey of refractive error in two groups of Malawians: a group of rural agricultural workers (n = 510) and a group of students at an urban teachers' college (n = 534). The overall prevalence of myopia was low; 2.5% (95% confidence interval 1.3%, 3.7%) of participants had an error of -0.5 D or greater. The mean refractive error (right eye) in the urban student group was +0.52 D compared to +0.62 D among the rural agricultural workers and the excess myopia was accounted for by significant myopia (> or = -0.75 D) in a few individuals, rather than an overall shift towards myopia within the urban student group. Among the rural agricultural workers, literacy predicted refractive error (right eye), with a mean of +0.59 D in the rural literate compared to +0.67 D in the rural illiterate. These findings support the notion that myopia is uncommon in non-industrialized societies and that it is associated with increased literacy but we have not identified specific risk factors within this group to predict the occurrence of significant myopia. In settings such as Malawi, refractive services should be targeted to urban centers, where more educated populations are likely to be found.

Adolescent↗

PubMed2000

The refractive status and vision profile: a questionnaire to measure vision-related quality of life in persons with refractive error.

OBJECTIVE/BACKGROUND: To describe the Refractive Status and Vision Profile (RSVP), a questionnaire that measures self-reported vision-related health status (symptoms, functioning, expectations, concern) in persons with refractive error. DESIGN: Cross-sectional study by survey. PARTICIPANTS: The RSVP was self-administered by 550 participants with refractive error (or history of refractive surgery) recruited from five refractive surgery practices and one optometric practice. Information on refraction, uncorrected and best-corrected visual acuity, and history of refractive surgery was obtained from physicians' records. METHODS: Internal consistency, test-retest reliability, agreement with global measures of vision (criterion validity), discriminant validity, content validity, and construct validity (associations of scale scores with patient status variables) were assessed using Cronbach's alpha, Spearman rank correlations, factor analysis, and multitrait analysis. OUTCOME MEASURES: Scores on the overall RSVP scale (S) and on eight RSVP subscales (functioning, driving, concern, expectations, symptoms, glare, optical problems, problems with corrective lenses) were calculated based on 42 items. RESULTS: Cronbach's alpha was 0.92 for S and ranged from 0.70 to 0.93 for RSVP subscales, indicating good internal consistency. Satisfaction with vision was more strongly associated with S than with refractive error or with visual acuity. Individuals with more refractive error had significantly lower (worse) scores for S and for subscales concern, functioning, driving, optical problems, and glare. Scores for S and for subscales concern, functioning, optical problems, and driving remained significantly associated with satisfaction with vision after adjustment for age, gender, corrective lens type, and refractive error. CONCLUSIONS: The RSVP measures a range of visual, functional, and psychologic impacts of refractive error that are likely to be important to patients. The RSVP would be a useful tool for evaluating interventions for correction of refractive error and may be useful for assessing refractive surgery candidates in clinical practice.

Adolescent↗

PubMed1983

Variation of the green-red ratio with refractive error.

The relationship of refractive error to green-red ratios among color normals was investigated by asking 27 subjects to match a standard yellow with a mixture of red and green primaries using a Nagel anomaloscope. Green-red ratios did not show any regular change with refractive error. Differences in refractive error, natural or induced, among color normal persons did not change the measurements of color vision with the Nagel anomaloscope.

Color Perception↗

PubMed1992

Myopia and refractive error in dogs.

The refractive error of 240 phakic dogs of various breeds was measured using streak retinoscopy and averaged (-0.27 +/- 1.41 D relative to infinity). Analysis by breed showed that the German Shepherd, Rottweiler, and Miniature Schnauzer breeds had an increased prevalence of myopia with an average refractive error of -0.86 +/- 1.31 D, -1.77 +/- 1.84 D, and -0.66 +/- 1.05 D, respectively. Myopia also was found in older dogs with marked nuclear sclerosis of the crystalline lens. Fifty-three percent of all German Shepherd dogs in a veterinary clinic population (n = 58 eyes) had a myopic refraction of greater than or equal to -0.50 D; 64% of all Rottweiler dogs (n = 28 eyes) were myopic. An in-depth investigation of German Shepherd dogs, using A-scan ultrasonography, photokeratoscopy, and streak retinoscopy, was done at Guide Dogs for the Blind (San Rafael, CA). By contrast with the results obtained in the veterinary clinic population, the overall average refractive error of guide dog German Shepherd dogs (n = 106 eyes) was +0.19 +/- 0.81 D, and only 15% of these dogs were myopic. The axial length and corneal curvature of myopic eyes did not differ significantly from nonmyopic eyes.

Animals↗

PubMed1987

Refractive errors in children.

Optical correction of refractive errors in infants and young children is indicated when the refractive errors are sufficiently large to cause unilateral or bilateral amblyopia, if they are impairing the child's ability to function normally, or if the child has accommodative strabismus. Screening for refractive errors is important and should be performed as part of the annual physical examination in all verbal children. Screening for significant refractive errors in preverbal children is more difficult; however, the red reflex test of Bruckner is useful for the detection of anisometropic refractive errors. The photorefraction test, which is an adaptation of Bruckner's red reflex test, may prove to be a useful screening device for detecting bilateral as well as unilateral refractive errors. Objective testing as well as subjective testing enables ophthalmologists to prescribe proper optical correction for refractive errors for infants and children of any age.

Adolescent↗

PubMed2002

Headaches associated with refractive errors: myth or reality?

INTRODUCTION: Headache and refractive errors are very common conditions in the general population, and those with headache often attribute their pain to a visual problem. The International Headache Society (IHS) criteria for the classification of headache includes an entity of headache associated with refractive errors (HARE), but indicates that its importance is widely overestimated. OBJECTIVES: To compare overall headache frequency and HARE frequency in healthy subjects with uncorrected or miscorrected refractive errors and a control group. METHODS: We interviewed 105 individuals with uncorrected refractive errors and a control group of 71 subjects (with properly corrected or without refractive errors) regarding their headache history. We compared the occurrence of headache and its diagnosis in both groups and assessed its relation to their habits of visual effort and type of refractive errors. RESULTS: Headache frequency was similar in both subjects and controls. Headache associated with refractive errors was the only headache type significantly more common in subjects with refractive errors than in controls (6.7% versus 0%). It was associated with hyperopia and was unrelated to visual effort or to the severity of visual error. With adequate correction, 72.5% of the subjects with headache and refractive error reported improvement in their headaches, and 38% had complete remission of headache. Regardless of the type of headache present, headache frequency was significantly reduced in these subjects (t = 2.34, P =.02). CONCLUSIONS: Headache associated with refractive errors was rarely identified in individuals with refractive errors. In those with chronic headache, proper correction of refractive errors significantly improved headache complaints and did so primarily by decreasing the frequency of headache episodes.

Adolescent↗

PubMedDate not supplied

Effectiveness of LASIK to correct refractive error after penetrating keratoplasty.

OBJECTIVE: Refractive errors may invalidate the good results of penetrating keratoplasty (PK). The Authors evaluate the effectiveness of excimer laser in situ keratomileusis (LASIK) in the correction of refractive error after PK. MATERIALS AND METHODS: Four patients, a 26-year-old woman, a 54-year-old man, a 19-year-old man, and a 51-year-old woman, showed refractive errors: -11 = -4.5 x 85 ; -8, -4.5 = -11 x 95 ; and -4.5 = -4 x = 1200, with a clear graft at least 20 months after penetrating keratoplasty secondary to keratoconus. However, they underwent the LASIK procedure with a nasal-hinged flap of 160 um. No sutures were placed. RESULTS: At follow-up, 24, 18, 12, and 12 months, respectively, the graft remained clear and the endothelial cells were unchanged. The uncorrected visual acuities were 20/50, 20/25, 20/50, and 20/25, respectively with an unchanged best corrected visual acuity (20/20) for all patients. No significant complications were observed. CONCLUSIONS: LASIK procedure seems to be an effective technique to correct refractive error after successful penetrating keratoplasty.

Adult↗

PubMed1999

Model of human refractive error development.

PURPOSE: To construct a model of refractive error development that can account for the different interactive mechanisms and time courses of refractive error in the hyperope (HYP), emmetrope (EMM), early-onset myope (EOM), and late-onset myope (LOM) over the first 30 years of life. METHODS: First, a baseline short-term (1 mo.) simulation of a previously developed nearwork-induced transient myopia (NITM) model was performed under both far- and near-viewing paradigms to obtain the critical relationships between AErms and refractive error for the four refractive groups. Then, two control pathways were added to the NITM model. The genetically-controlled pathway was associated with the long-term growth of the cornea, lens, and the eyeball. The environmentally-controlled pathway was associated with retinal-defocus during nearwork, wherein the root mean square (rms) of the accommodative error (AE) above a threshold level resulted in an increase in axial length of the eyeball. The thresholds for defocus-induced axial length change were empirically determined to correspond to the differential susceptibility in the four refractive groups. The combination of effects from the two pathways produced the overall refractive error. The relationship between AErms and refractive error was combined with the two control pathways for the long-term simulations (30 yrs: the initial 15 yrs using a far-viewing paradigm followed by an additional 15 yrs using a near-viewing paradigm) to quantify refractive error development as related to daily nearwork activity in the four refractive groups. RESULTS: All refractive groups began early in life with a genetically-determined hyperopic refractive error. The HYP had the lowest susceptibility or highest threshold to retinal defocus effects, and remained at a hyperopic level. The EMM exhibited a relative myopic shift in the first 2 years to become and remain at emmetropia. In the myopic groups, the EOM exhibited both a genetically-controlled component (starting 2 years of age) and a defocus-induced component (starting at 15 years of age), whereas the LOM manifested only a defocus-induced factor (starting at 15 years of age) in the development of myopia. In addition, simulations indicated that emmetropization occurred only for "induced" refractive error that was less than 0.5 D, which was consistent with the non-monotonic relationship between AErms and refractive error, wherein the minimum AErms occurred at 0.5 D. CONCLUSIONS: The model showed that both genetic and defocus-induced environmental factors play important roles in the development of refractive error in the different refractive groups. The model also provides a framework for further detailed quantitative analysis of the processes of refractive error development and emmetropization.

Accommodation, Ocular↗

PubMed2002

Development of refractive errors into old age.

PURPOSE: To evaluate refractive errors in older adults. METHODS: The distribution of refractive error components was evaluated in a sample of 569 older adults including 171 participants over the age of 80 years. The mean age was 75.2 years with a range from 59 to 106 years. Emphasis was placed on modern methods of analyzing astigmatic refractive errors, which convert cylindrical refractive errors into primary and oblique components. RESULTS: The known increase in hyperopia after maturity continues into old age. The primary negative astigmatic component increases dramatically in prevalence and amount after age 70 years, whereas the oblique component remains unchanged. Significant anisometropia is common in the oldest old, suggesting failure of emmetropization mechanisms with age. Substantial gender differences exist in refractive changes with age. CONCLUSIONS: The continuing changes in all components of refractive error into old age and the surprisingly high prevalence of large amounts of astigmatism and anisometropia emphasize the importance of regular refractive evaluations among the oldest old.

Aged↗

PubMed1997

Effect of contralateral fog during refractive error assessment.

BACKGROUND: When assessing refractive error using static retinoscopy, it is conventional to fog the contralateral eye by approximately 2.00 D to prevent a blur-driven accommodative response stimulating consensual accommodation in the tested eye. However, the effect of higher amounts of contralateral fog (e.g., in a moderate-to-high uncorrected myopic individual) during refractive error assessment is unclear. METHODS: We assessed the refractive state in 16 visually normal myopic subjects while fogging the contralateral eye between zero and 6.00 D, in 1.00 D increments. Retinoscopy was simulated by shining a streak retinoscope light into the right eye, while simultaneously measuring the refractive state of this eye objectively. RESULTS: No significant change in mean refractive state was observed for up to 5.00 D of contralateral fog. But, 6.00 D of contralateral fog produced a significant mean increase in the myopic direction of 0.13 D. Also, in three subjects, a myopic shift of approximately 0.60 D was recorded after the introduction of 6.00 D of contralateral fog. Nevertheless, the magnitude of these largest shifts in refractive error are still smaller than the previously reported degree of repeatability of static retinoscopy. CONCLUSIONS: Since large amounts of contralateral fog produced only small and clinically insignificant changes in the refractive state, the practitioner merely needs to ensure that the nontested eye is indeed fogged. The magnitude of fog present will have only a minimal effect on the final result.

Adult↗

PubMedDate not supplied

Combining refractive error and uncorrected visual acuity to assess the effectiveness of refractive corneal surgery.

Residual refractive error and uncorrected visual acuity are two frequently measures used to assess the effectiveness of refractive corneal surgery. Nordan and colleagues have suggested a Visual Function Index which combines these two measures in one quantitative measure. This article presents a Visual Function Score for radial keratotomy which includes a set of qualitative categories (excellent, good, fair, poor) and specifies the clinical values for refractive error and visual acuity in each category. There was substantial agreement among ophthalmologists who reviewed the category definitions, and we think that the Visual Function Score improves our ability to objectively assess surgical outcome. Application of the score to the Prospective Evaluation of Radial Keratotomy (PERK) Study data yielded closer agreement with refractive error results than with visual acuity values. The Visual Function Score lowered the classification of eyes that were hyperopic but had sufficient accommodation to overcome so that a high visual acuity result could be achieved. The inclusion of astigmatism values would be an important next step in the development of composite measures for the assessment of refractive surgery. In the future, a multifactorial index or score may be used to estimate the outcome of reported surgical procedures.

Adult↗

PubMed1993

Relation between the dark focus of accommodation and refractive error--a cycloplegic study.

We measured distance refractive error (Dist R), dark refractive error (Dark R), and cycloplegic refractive error (Cyclo R) in 196 subjects whose ages ranged from 4 to 17 years, using the Canon Autoref R-1. We defined the values of (Dark R--Dist R) as DFcus (Dist R) and those of (Dark R--Cyclo R) as DFcus (Cyclo R) in this study. Although DFcus (Dist R) was larger in less myopic and more hyperopic eyes similar to DFcus (Cyclo R), it was zero or plus in high hyperopic eyes, unlike DFcus (Cyclo R). We found Dist R was more strongly influenced by Cyclo R than was Dark R. It is not adequate to use Dist R as the far point for precise evaluation of the dark focus. We should use the difference between Dark R vs. Cyclo R as the true value of the dark focus of accommodation.

Accommodation, Ocular↗