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PubMed1979

The effect of cycloplegia on the determination of refractive error by the Ophthalmetron.

The Ophthalmetron was used to measure the refractive error of 10 male optometry students. Although there was a high incidence of invalid readings, more repeatable results were obtained with use of a cycloplegic. Measurements made under cycloplegia revealed 0.41 D more hyperopia but no differences in astigmatism as compared to the noncycloplegic refraction. Instrument myopia was shown not to be a factor.

Accommodation, Ocular↗
PubMed2004

[The analysis of refractive error in children and adolescents from 6-15 years of age based on 1000 examinations in two major Polish regions].

PURPOSE: The aim of this study is to present the results of screening examinations of refractive errors, taken on 1002 of school children ranging from 6 to 15 years of age. MATERIAL AND METHODS: As the result of Internet screening visual acuity and color perception tests named "I can see..." in 10,021 children from randomly chosen schools in Poland in the year 2002, the group of 1002 children was chosen. In this group, the subjective and objective refractive error examination was taken as well as the visual acuity test, color perception with the use of Ishihara tables and full ophthalmologic examination. RESULTS: Average visual acuity was RE: 0.72 (SD +/- 0.31) and LE: 0.72 (SD +/- 0.31). The prevalence of emmetropia was 34%. In the examined group myopia in 17%, hyperopia in 20%, astigmatism in 5.5% of children was found, and in 24.5% of patients complex errors occur such as myopic and hyperopic astigmatism.

Adolescent↗
PubMed1999

Laser in situ keratomileusis to correct refractive errors after keratoplasty.

PURPOSE: To assess the safety and effectiveness of excimer laser in situ keratomileusis (LASIK) to correct refractive myopia, astigmatism, or both after keratoplasty. SETTING: Eye Clinic Day Hospital, São Paulo, Brazil. METHODS: Twenty-two eyes that had previously had corneal transplantation were studied. Laser in situ keratomileusis was performed using the Chiron automated microkeratome and the VISX Twenty-Twenty B excimer laser. RESULTS: Mean follow-up after LASIK was 10.09 months +/- 3.87 (SD). The spherical equivalent refraction dropped from -4.55 +/- 3.66 D before LASIK to -0.67 +/- 1.24 D after surgery. At the last examination, 72.7% of patients had a refractive error within +/- 1.00 D of emmetropia and 54.5% had uncorrected visual acuity of 20/40 or better. Vector analysis of astigmatic correction showed an index of success of 54.0%. Best spectacle-corrected visual acuity was unchanged in 8 cases, improved in 9, and decreased in 5. Significant endothelial cell loss, keratoplasty wound dehiscence, and other serious complications did not develop in any eye. CONCLUSION: The correction of refractive error with LASIK in postkeratoplasty patients proved to be safe, effective, and predictable. Further studies with longer follow-up are needed to determine the method's clinical value.

Adult↗
PubMed2000

Refractive errors and strabismus in premature Asian infants with and without retinopathy of prematurity.

AIM: In Caucasian populations, premature infants with retinopathy of prematurity (ROP) have been reported to have higher risks of developing refractive errors and strabimus. The purpose of this study is to evaluate the rate of these complications in Asian premature infants with and without ROP. METHODS: A retrospective case review of all premature infants referred to the Singapore National Eye Centre for ophthalmology screening. These included all neonates born earlier than 34 weeks gestational age and less than 1500 grams in birth weight. Standardized ophthalmology examinations including cycloplegic refraction and fundus examination at regular intervals were performed to determine the presence of ROP, refractive errors, squints and other ocular abnormalities until the patients were 3 years old. RESULTS: During 1991 to 1993, a total of 113 neonates were reviewed. Of these, 16 (14.2%) developed ROP. The risk of ROP was higher with lower birth weights and earlier gestational ages. At 1-year follow-up, the rate of myopia was 33.3% in babies with ROP compared to 3.7% in babies with no ROP (p < 0.001). The higher rates of myopia in babies with ROP remained with longer follow-up (33.3% and 25% in ROP group versus 3.4% and 3.8% in no ROP group, at 2 and 3 years respectively). There was no difference in rates of astigmatism or hyperopia throughout the 3 years. At 1 year follow-up, the rate of strabismus was 20% in the ROP group compared to 4.9% in the no ROP group (p = 0.07). However, this difference in rates of strabismus was not significant at 2 and 3 years of follow-up. CONCLUSION: Premature babies with ROP had higher rates of myopia and strabismus than those without ROP. Long-term follow-up of these babies is important for early detection and treatment of these ocular problems.

Asian People↗
PubMed2004

Computer-assisted measurement of retinal vessel diameters in the Beaver Dam Eye Study: methodology, correlation between eyes, and effect of refractive errors.

OBJECTIVE: Narrowed retinal arterioles may independently predict cardiovascular disease. We describe a computer-assisted method to measure retinal vessel diameters from digitized fundus photographs in a large population, and examine the correlation of retinal vessel diameters between eyes and whether refractive errors affect these measurements. DESIGN AND POPULATION: Population-based, cross-sectional study in Beaver Dam, Wisconsin (n = 4926; age, 43-84 years). METHODS: Retinal photographs were digitized, and all arterioles and venules located in an area 0.5 to 1 disc diameter from the optic disc were measured with the aid of computer software. MAIN OUTCOME MEASURES: Summary of retinal arteriolar and venular diameters, and the ratio of their diameters (arteriole:venule ratio [AVR]). RESULTS: Correlation between right and left eyes was substantial for retinal arteriolar diameters (Pearson correlation coefficient, rho = 0.71) and venular diameters (rho = 0.74), and moderate for the AVR (rho = 0.49). The inverse association of higher blood pressure and smaller retinal arteriolar diameters was similar using data from either one eye or two eyes; arteriolar diameters decreased by 4.1 microm (right eyes), 4.0 microm (left eyes), and 4.0 microm (mean of both eyes) with each 10-mmHg increase in mean arterial blood pressure. A myopic refraction was associated with smaller retinal vessel diameters; arteriolar diameters decreased by 2.8 microm and venular diameters by 3.3 microm with each -1.0-diopter shift towards myopia. However, the pattern and strength of the association of blood pressure and retinal vessel diameters were not altered by variations in refractive errors. CONCLUSIONS: There is good correlation of retinal vessel diameters between eyes. A myopic refraction is associated with smaller retinal vessel diameters. The association of retinal arteriolar diameters and blood pressure seems similar using data from either one eye or two eyes, and is minimally affected by refraction. These data suggest that measurement of retinal vessel diameters from one eye without regard to its refractive status may provide adequate information indicative of a person's retinal vessel caliber if information from two eyes and refraction is unavailable.

Adult↗
PubMed1990

[Contact lenses for correction of refractive errors. A status determination].

The contact lens is still the most frequently used visual aid applied directly to the eye to correct refractive errors. The most important refractive indications and the advantages and drawbacks of the major lens types are discussed. Toric, bifocal and disposable lenses are also presented. The development of new, highly gas-permeable rigid materials are considered.

Contact Lenses↗
PubMed2000

Prevalence and risk factors for refractive errors in adult Chinese in Singapore.

PURPOSE: To determine the epidemiology of refractive errors in an adult Chinese population in Singapore. METHODS: A disproportionate, stratified, clustered, random-sampling procedure was used to select names of 2000 Chinese people aged 40 to 79 years from the 1996 Singapore electoral register in the Tanjong Pagar district in Singapore. These people were invited to a centralized clinic for a comprehensive eye examination, including refraction. Refraction was also performed on nonrespondents in their homes. Myopia, high myopia, and hyperopia were defined as a spherical equivalent (SE) in the right eye of less than -0.5 D, less than -5.0 D, and more than +0.5 D, respectively. Astigmatism was defined as less than -0.5 D of cylinder. Anisometropia was defined as a difference in SE of more than 1.0 D between the two eyes. Only phakic eyes were analyzed. RESULTS: From 1717 eligible people, 1232 (71.8%) were examined. Adjusted to the 1997 Singapore population, the overall prevalence of myopia, hyperopia, astigmatism, and anisometropia was 38.7% (95% confidence interval [CI]: 35.5, 42.1), 28.4% (95% CI: 25.3, 31.3), 37.8% (95% CI: 34.6, 41.1), and 15.9% (95% CI: 13.5, 18.4), respectively. The prevalence of high myopia was 9.1% (95% CI: 7.2, 11.2), with women having significantly higher rates than men. The age pattern of myopia was bimodal, with higher prevalence in the 40 to 49 and 70 to 81 age groups and lower prevalence between those age ranges. Prevalence was reversed in hyperopia, with a higher prevalence in subjects aged 50 to 69. There was a monotonic increase in prevalence with age for both astigmatism and anisometropia. Increasing educational levels, higher individual income, professional or office-related occupations, better housing, and greater severity of nuclear opacity were all significantly associated with higher rates of myopia, after adjustment for age and sex. CONCLUSIONS: The results indicate that whereas myopia is 1.5 to 2.5 times more prevalent in adult Chinese residing in Singapore than in similarly aged European-derived populations in the United States and Australia, the sociodemographic associations are similar.

Adult↗
PubMedDate not supplied

Epidemiology of refractive errors and presbyopia.

Limitations in existing studies of the epidemiological aspects of refraction are attributed to both technical and statistical procedures. Early influences of ocular parameters on refraction are identified accordingly as prematurity and may or may not be involved. Attention is paid to familial and genetic influences, and infants and toddlers are examined as a group separate from schoolchildren and teenagers, who are likely to have experienced significant periods of near work. The effects of sex and geographical distribution are considered both for younger and older age ranges. Special attention is paid to anisometropia, which is shown-apparently for the first time-to increase appreciably among presbyopes. The connection between refractive errors and ocular pathologies is reviewed, and possible means of preventing early onset myopia are examined. Presbyopia is addressed with reference to its geographical distribution and hypothetical links to accommodation insufficiency.

Age Factors↗
PubMed2006

Visual and refractive results of combined PTK/PRK in patients with corneal surface disease and refractive errors.

PURPOSE: To investigate the changes in symptoms, refraction, and visual acuity (VA) in patients with corneal surface disease and refractive errors who had phototherapeutic keratectomy (PTK) combined with photorefractive keratectomy (PRK). SETTING: University-based referral practice. METHODS: Patients with myopia or astigmatism and map-dot-fingerprint dystrophy or recurrent erosions were treated. The corneal epithelium was removed with a 64 blade, and laser was performed using a Visx Star S3 laser. RESULTS: Nineteen eyes of 14 patients were treated. Preoperatively, mean myopia was -3.76 diopters (D) (range -7.50 to -0.75 D), mean astigmatism was +0.96 D (range 0.00 to +2.25 D), and mean UCVA was 20/400. At 3 months, mean myopia was -0.53 D (range -1.75 to +0.75 D) (P<.001), mean astigmatism was +0.58 D (range 0.00 to +1.25 D) (P = .05), and mean uncorrected VA was 20/23 (P<.001). At 6 months, mean myopia was -0.31 D (range -1.00 to +0.75 D) (P<.001), mean astigmatism was +0.56 D (range 0.00 to +1.25 D) (P = .05), and mean uncorrected VA was 20/23 (P<.001). The change in astigmatism was confirmed by vector analysis. Only 1 patient lost 1 line of acuity, and all patients were asymptomatic. CONCLUSION: Patients with myopia and astigmatism and symptomatic epithelial basement membrane disorders who had PTK/PRK had resolution of their symptoms and nearly achieved emmetropia. Therefore, this procedure is safe and effective for patients with corneal surface disease and myopia.

Adult↗
PubMed1997

[Occurrence of refractive errors in relation to retinopathy of prematurity].

Results of the development of refractive errors in the group of prematurely born children with reversible ROP changes and those where cryoretinopexy due to ROP were done are presented. Ametropia was found higher (statistically significant with P = 0.05) in all the groups with prematurity comparing to the population of in-therm born children. The same result with regard to strabismus was found. Prematurity presumably leads to ophthalmic pathology.

Child↗
PubMed2000

Distribution of refractive errors in Spain.

The aim of this work was to characterise the refractive state of a Spanish population. Special attention to myopia prevalence was carried out. At this stage 7621 subjects, 3692 males and 3929 females, between 3 and 93 years were examined by means of static retinoscopy and subjective refraction. The most prevalent was emmetropia with a mean percentage of 43.2% and ranging from 60.6% (3-8 years) to 29.0% (66-93 years). The prevalence of hyperopia (35.6%) increased with age, from 36.9% (3-8 years) to 55.8% (66-93 years). Myopia appeared to be more prevalent in the 30-35 age group (30.1%), agreeing with the more near-work demanding age range. Mean refractive error obtained was +0.19 +/- 3.42 D, ranging from +0.05 +/- 3.18 D (20-35 years) to +0.96 +/- 2.42 (66-93 years). Reading addition value obtained was similar to respective values of age of other populations. The whole Spanish population evaluated was emmetrop. No differences in prevalence from other populations were found, obtaining greater values of myopia in groups with more near work and a greater percentage of hyperopia versus age.

Adolescent↗
PubMed1986

Refractive error and the reading process: a literature analysis.

The literature analysis of refractive error and reading performance includes only those studies which adhere to the rudaments of scientific investigation. The relative strengths and weaknesses of each study are described and conclusions are drawn where possible. Hyperopia and anisometropia appear to be related to poor reading progress and their correction seems to result in improved performance. Reduced distance visual acuity and myopia are not generally associated with reading difficulties. There is little evidence relating astigmatism and reading, but studies have not been adequately designed to draw conclusions. Implications for school vision screening are discussed.

Astigmatism↗
PubMed2003

Evaluation of the measurement of refractive error by the PowerRefractor: a remote, continuous and binocular measurement system of oculomotor function.

BACKGROUND/AIM: The technique of photoretinoscopy is unique in being able to measure the dynamics of the oculomotor system (ocular accommodation, vergence, and pupil size) remotely (working distance typically 1 metre) and objectively in both eyes simultaneously. The aim of this study was to evaluate clinically the measurement of refractive error by a recent commercial photoretinoscopic device, the PowerRefractor (PlusOptiX, Germany). METHOD: The validity and repeatability of the PowerRefractor was compared to: subjective (non-cycloplegic) refraction on 100 adult subjects (mean age 23.8 (SD 5.7) years) and objective autorefraction (Shin-Nippon SRW-5000, Japan) on 150 subjects (20.1 (4.2) years). Repeatability was assessed by examining the differences between autorefractor readings taken from each eye and by re-measuring the objective prescription of 100 eyes at a subsequent session. RESULTS: On average the PowerRefractor prescription was not significantly different from the subjective refraction, although quite variable (difference +0.05 (0.63) D, p=0.41) and more negative than the SRW-5000 prescription (by -0.20 (0.72) D, p<0.001). There was no significant bias in the accuracy of the instrument with regard to the type or magnitude of refractive error. The PowerRefractor was found to be repeatable over the prescription range of -8.75D to +4.00D (mean spherical equivalent) examined. CONCLUSION: The PowerRefractor is a useful objective screening instrument and because of its remote and rapid measurement of both eyes simultaneously is able to assess the oculomotor response in a variety of unrestricted viewing conditions and patient types.

Adolescent↗
PubMed1988

Monocular diplopia accompanying ordinary refractive errors.

Monocular diplopia is commonly encountered in ophthalmic practice. We discovered that it could be induced in nine (82%) of 11 normal eyes with ordinary spherical or astigmatic defocus of the retinal image. Possible mechanisms responsible for this effect include retinal processing, diffraction effects, and spherical aberration. By employing geometric blur circle theory and using a simple optical model to photograph the effect, we concluded that monocular diplopia in the setting of ordinary refractive error is secondary to relatively minor optical irregularity such as spherical aberration. Contour enhancement properties of the retina probably accentuate this effect. Ordinary refractive error should therefore not be overlooked or discounted in patients with monocular diplopia.

Adult↗
PubMed1985

Simulating refractive errors: source and observer methods.

There are two principal methods of simulating refractive errors. Either the retinal image can be defocused by an optical system, usually a positive lens, placed in front of an observer's eye (observer method), or the source of the retinal image can be defocused as it is projected onto a screen or photograph (source method). There are significant differences between the two methods, differences that make it difficult to compare results. However, the source method, which is the more artificial, seems to be superior for a number of reasons. The results of these two methods can be compared using a common or interchangeable parameter for specifying the level of defocus. A convenient parameter is the size of the defocused image of a point, measured either in image space (linear or angular diameter on the retina) or in object space (angular diameter of the blur disc projected back into object space), with the angular diameter measured from the respective nodal point of the eye. Methods of measuring the angular blur-disc diameter for both methods are discussed and the validity of the formula omega = D delta L, is investigated, where omega is the angular diameter of the blur disc, D is the observer's pupil diameter, and delta L is the dioptric defocus.

Humans↗
PubMed2006

Uncorrected refractive errors and spectacle utilisation rate in Tehran: the unmet need.

AIM: To determine the prevalence of the met and unmet need for spectacles and their associated factors in the population of Tehran. METHODS: 6497 Tehran citizens were enrolled through random cluster sampling and were invited to a clinic for an interview and ophthalmic examination. 4354 (70.3%) participated in the survey, and refraction measurement results of 4353 people aged 5 years and over are presented. The unmet need for spectacles was defined as the proportion of people who did not use spectacles despite a correctable visual acuity of worse than 20/40 in the better eye. RESULTS: The need for spectacles in the studied population, standardised for age and sex, was 14.1% (95% confidence interval (CI), 12.8% to 15.4%). This need was met with appropriate spectacles in 416 people (9.3% of the total sample), while it was unmet in 230 people, representing 4.8% of the total sample population (95% CI, 4.1% to 5.4%). The spectacle coverage rate (met need/(met need + unmet need)) was 66.0%. Multivariate logistic regression showed that variables of age, education, and type of refractive error were associated with lack of spectacle correction. There was an increase in the unmet need with older age, lesser education, and myopia. CONCLUSION: This survey determined the met and unmet need for spectacles in a Tehran population. It also identified high risk groups with uncorrected refractive errors to guide intervention programmes for the society. While the study showed the unmet need for spectacles and its determinants, more extensive studies towards the causes of unmet need are recommended.

Adolescent↗
PubMed1999

Refractive error changes in mixed astigmatism.

The purpose of this note is to examine refractive error changes in children who change from mixed astigmatism to myopic astigmatism. Data were collected for 16 children who changed from mixed astigmatism to simple myopic or compound myopic astigmatism. Children with mixed astigmatism showed minimal refractive changes until they converted to myopic astigmatism, at which time refractive changes increased.

Adolescent↗
PubMed1986

Testing visual acuity in the emergency department: a simple method of correcting refractive error by using the hand-held ophthalmoscope.

The assessment of visual acuity is an important part of the emergency ophthalmologic examination. The ability to distinguish refractive error from other etiologies of decreased visual acuity is necessary to adequately evaluate visual function. A readily available source of corrective lenses can be found in the hand-held ophthalmoscope. These lenses can be used to identify and quantitate refractive errors and assist in identifying serious ocular pathology.

Emergencies↗