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PubMed1999

Prevalence and predictors of undercorrected refractive errors in the Victorian population.

PURPOSE: To investigate the prevalence and predictors of undercorrected refractive errors in the Victorian population. METHODS: In this prospective study, a population-based sample of residents was recruited. The improvement in visual acuity with subjective refraction was assessed. Several individual characteristics were investigated as predictors of undercorrected refractive error. RESULTS: There were 5,615 eligible residents, of which 4,735 (84%) participated in the study (53% were women). In all, 466 participants (10%) had significant undercorrected refractive error leading to an improvement of 1 or more lines of visual acuity with refraction. Age was the most important predisposing factor. The risk of undercorrected refractive error increased by 1.8 times for every decade of life starting at 40 years of age. The next most important factor was the absence of distance refractive correction. These individuals were 6.8 times more at risk compared with those who wore distance spectacles. Other significant predictors of undercorrected refractive error were the presence of cataract and European or Middle Eastern languages spoken at home. People with tertiary education or hypermetropia were less likely to need refractive error improvement. Gender, country of birth, and employment status did not have any statistically significant effect after controlling for confounders. CONCLUSIONS: The results of this study disclose people in the community who are more at risk of compromising their vision because of undercorrected refractive errors. A campaign is warranted to alert people that it may be possible to improve their vision.

Adult↗
PubMed1997

Refractive errors in young children with Down syndrome.

Significant refractive errors are common among older children and adults with Down syndrome. We examined infants and children with Down syndrome to determine the prevalence of these errors at younger ages. Noncycloplegic retinoscopy was used to determine the refractive state of 92 infants and children with Down syndrome, aged 4 months to 12 years. The results for infants show a similar distribution of refractive errors in patients with Down syndrome and an age-matched control group. However, rather than a narrower distribution for the older age groups, as is the case with the controls, the distribution is wider, and the prevalence of refractive errors (including astigmatism) is higher among young children with Down syndrome than among controls. This high prevalence of refractive defects cannot be explained by the presence of strabismus or other pathologies.

Child↗
PubMed1980

Correlation of aphakic retinal detachment and refractive error with gender.

I analyzed the aphakic refractive errors of men and women separately in a statistical study of patients with aphakic retinal detachments. I compared the distribution of aphakic refractive errors in a population of 81 adult patients with nontraumatic aphakic retinal detachment with that of a randomly selected control population of 93 adult patients with aphakia. As a group, women who developed aphakic retinal detachments were significantly more myopic than female controls (11.41 vs 12.37 diopters of spherical equivalent; P = .004). In contrast, the refractive error in men did not differ between the aphakic retinal detachment and control groups (11.31 vs 11.68 diopters; P = .156). A significantly higher percentage of patients with bilateral (87%) aphakic retinal detachments were men (P = .017). In men other risk factors for aphakic retinal detachment, including cardiovascular disease, may overshadow the influence of axial myopia.

Adult↗
PubMed1987

Use of photoretinoscopy as a screening technique in the assessment of anisometropia and significant refractive error in infants/toddlers/children and special populations.

The presence of significant refractive error and/or anisometropia can produce an irreversible decrease in visual function if not detected and treated at an early age. The general consensus is that the earlier a problem is detected, the easier the process of remediation. The authors have examined photoretinoscopy as a means of screening infant/toddlers and/or nonverbal persons for refractive anomalies. Fifty adults and fifty infants/toddlers/children were photographed and the estimated refractive error from review of the pictures was compared to the refractive error obtained from retinoscopy. The results indicate that photoretinoscopy is an effective screening procedure for the detection of significant refractive error and is extremely sensitive to anisometropia.

Adolescent↗
PubMed1989

Changes in refractive error for exotropes treated with overminus lenses.

The refractive changes of pediatric patients who were prescribed overminus lenses for exotropia were evaluated. Overminus lenses means additional minus power over the lenses required to correct the refractive error at distance. Forty exotropic patients, ages 1 to 15 years, were prescribed overminus lenses (-0.50 D to -3.75 D) for a period of 9 to 86 months. A small but significant correlation was found between the initial refractive error and the mean annual change toward myopia. Other factors such as age when treatment was given, duration of therapy, amount of overminus, and the amount of the exodeviation had little effect on the rate of myopic change. The mean annual changes in refractive error for hyperopes (-0.13 +/- 0.44 D, N = 15), emmetropes (-0.26 +/- 0.37 D, N = 17), and myopes (-0.75 +/- 0.77 D, N = 18) were similar to values reported in the literature for nonexotropic children.

Adolescent↗
PubMed1995

Spherocylindrical refractive errors and visual acuity.

BACKGROUND: Understanding the relation between refractive error and visual acuity is complicated if astigmatic blur is present. No models are in widespread use that allow the combination of spherical and astigmatic errors for the purpose of predicting visual performance. METHODS: Models for combining spherical and astigmatic errors are discussed, and predictions of these models using data from the literature are presented. RESULTS: Three models for combining astigmatic with spherical errors are shown to predict visual acuity performance in uncorrected myopic refractive errors. A dioptric vector addition model is shown to have advantages over other candidate models. CONCLUSIONS: It is possible to combine spherocylindrical refractive errors into a single value when the objective is to correlate these values with visual acuity performance.

Eyeglasses↗
PubMed1990

A comparison of cycloplegic refraction to the near retinoscopy technique for refractive error determination.

The near retinoscopy technique of refractive error determination was compared to the standard method of cycloplegic refraction using 10 "infants" (3-12 months of age) and 10 "children" (32-109 months of age). There was a significant difference between the techniques for both sphere and cylinder power. Although there was no interaction of refractive technique and age group, the difference between near retinoscopy and cycloplegic refractive error tended to be larger for infants than for children. No significant difference was found when the average refractive values were compared for monocular or binocular conditions and no significant effect was found for either gender or laterality (right versus left eye). Based on these findings, it is suggested that caution be used in substituting the near retinoscopy technique for cycloplegic refraction even utilizing a "correction" factor for the dioptric difference between techniques.

Analysis of Variance↗
PubMed1983

Visual disability and blindness secondary to refractive errors in Africa.

Optical defects of the light-focusing apparatus of the eye are called errors of refraction. They are responsible for 13% of all significant vision loss in Kenya, ranking third of all causes, after cataract and trachoma. As the overall prevalence of such visual impairment in the Country is 3.7%, roughly 0.5% of the population can be said to need spectacles to obtain normal vision. The comparable figure for secondary school children in Nigeria has been found to be 2.4%. In addition, patients require special spectacles after cataract surgery to obtain adequate vision; without such spectacles these patients are still 'blind' by World Health Organization criteria. These glasses can be obtained through mission societies and various charitable organizations for a little as $5 per pair, and can be manufactured locally with available ophthalmic manpower and technology. Alternatives to spectacles such as contact lenses, intra-ocular lenses and Kerato-refractive surgery are not suitable for use in developing Countries.

Africa↗
PubMed1990

[Refractive errors, strabismus and amblyopia in pre-school screening--experiences using a vision test in kindergarten].

UNLABELLED: Within the framework of mass screenings conducted by the Public Health service section for juveniles, 254 children were examined jointly on a voluntary basis in 5 different kindergartens. The examined children represented in each case 88% of the respective kindergarten groups. The examination programme included, among others, the R5 apparatus (visual acuity in respect of remote objects with and without + 1.5 D), Lang- and DeKa Stereo Test, Cover-and-Uncover Test with remote and near fixation, heterostatic retinoscopy (in 205 children only), ophthalmoscopic fixation test. In addition, the acceptance for U8 and the degree of care in respect of ophthalmological control and treatment were investigated. RESULTS: Strabismus or significant uncorrected errors of refraction were discovered by the on-target tests of covering and uncovering, fixation and retinoscopy in 26 of 205 completely examined children (12.7%). This had not been satisfactorily covered by single tests such as R5-Visus test with the criteria much less than 1.0 (grade 5) or much less than 0.7 (grade 4), respectively stereo tests. The combination of "R5-Test Visus much less than 1.0" and "DeKa Stereo Test not fully identified" attained a sensitivity of 81% with a positive predictive value of only 28%. This combination, therefore, results in too many healthy children being referred to the ophthalmologist. "R5-Test Visus much less than 0.7" and "DeKa Stereo Test not fully identified" attained a sensitivity of 75% with a positive predictive value of 44%. This combination is recommended as long as the R5 or R11 apparatuses are used. The phoria and stereo tests contained in the R5 apparatus are unsuitable for kindergarten screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Amblyopia↗
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↗
PubMedDate not supplied

Refractive errors and automated perimetry: discussion and case studies.

1. The effects of refractive error on automated perimetry were studied. The results of the study showed that an error of as little as 1 diopter can significantly influence the visual field to as much as 30 degrees from fixation. 2. In the case of automated visual field testing when only the central 30 degrees of visual field are tested, refractive error can cause a generalized depression. Because generalized depression can have several different causes, distinguishing between a true depression and one due to refractive error can be important. 3. Because a generalized depression from refractive error can mimic a depression due to true pathology, it is critical that the most recent refraction combined with the correct add for perimetry be used on each patient every time the patient undergoes a visual field examination.

Adult↗
PubMed1988

Algebra of sphero-cylinders and refractive errors, and their means, variance, and standard deviation.

Sphero-cylinders and refractive errors can be represented by matrices. Matrix algebra provides methods whereby sphero-cylinders can be added, subtracted, multiplied, inverted, and raised to powers and can have roots extracted. These operations are defined for sphero-cylinders and examples are given. In terms of these operations a number of means of refractive errors are defined: the arithmetic, harmonic, and quadratic means. Furthermore it is possible to define a variance and standard deviation for refractive errors. These quantities should provide a basis for a formal approach to the statistical analysis of populations of refractive errors.

Humans↗
PubMed1997

Pulsatile ocular blood flow variations with axial length and refractive error.

Ocular pulse amplitude (PA) and pulsatile ocular blood flow (POBF) were studied in 80 eyes from 80 subjects with a refractive error between +3.00 and -28.00 dpt using the Langham Ocular Blood Flow System. PA and POBF were correlated with axial length and refractive error using linear regression analysis. A significant correlation (p < 0.001) was found between PA and axial length (r = -0.787), PA and refractive error (r = 0.775), POBF and axial length (r = -0.655) and POBF and refractive error (r = 0.650). Myopic eyes were further divided into subgroups according to axial length, refractive error and fundus oculi characteristics. Each subgroup exhibited a significant reduction in PA (p < 0.001) compared to the control group. POBF reduction was significant in every subgroup except the subgroup with a refractive error lower than 6 dpt and the subgroup with an axial length shorter than 26 mm.

Adult↗
PubMed1982

Refractive errors in patients with fundus flavimaculatus.

A total of 59 patients (118 eyes) with fundus flavimaculatus who had atrophic macular lesions were examined for refractive error. Myopic refractions of greater than -0.1 dioptre were seen in 12% of a normal population and in 76% of our patient population. The spherical equivalent refractive errors described a single-peaked skewed distribution with a mean of -1.12 dioptres, which is 2.12 dioptres more myopic than that of a normal population. In addition astigmatic refractive errors of greater than +0.5 dioptres were found in 42% of this patient population, which is considerably more than the 18.6% observed in a normal population.

Adolescent↗
PubMed1999

LASIK for the correction of residual refractive errors from previous surgical procedures.

BACKGROUND AND OBJECTIVE: To evaluate laser assisted in situ keratomileusis (LASIK) efficacy in correcting residual refractive errors after corneal or intraocular surgery (penetrating keratoplasty, radial keratotomy, photorefractive keratectomy, phacoemulsification with intraocular lens (IOL) implantation, penetrating ocular trauma and phakic IOL implantation). MATERIAL AND METHODS: We performed LASIK in 87 eyes of 62 patients previously operated by means of other surgical techniques to completely correct the residual refractive error. We report the mean refractive error (in terms of spherical equivalent refraction), uncorrected visual acuity (UCVA) and spectacle corrected visual acuity (SCVA) before and after the surgical procedure. We also analyze safety and stability, in these results with a minimum of 12 months follow-up. RESULTS: Mean preoperative spherical equivalent was -5.25 +/- 2.1 diopters (D). Postoperatively, mean spherical equivalent was -0.70 +/- 0.65 D, 76% of eyes were between plano and -1.00 D and 99% were between plano and -2.25 D. At 12 months follow-up the change in the refractive result was equal or less than 0.5 D in 94% of eyes. Preoperatively SCVA was 1.0 or better in 24.13% of cases, and 0.5 or better in 89.65%. Postoperative SCVA was 1.0 or better in 26.43% and 0.5 or better in 95%. Preoperative UCVA was 0.1 in 2 eyes, 0.05 in 4 eyes and count fingers in the rest of the cases. Postoperative UCVA was 1.0 or better in 1.1% and 0.5 or better in 70.1%. We had an extremely low complication rate in this particular group of patients. CONCLUSIONS: LASIK can be successfully used to correct residual refractive errors after other surgical procedures.

Adult↗
PubMed1987

An evaluation of the NR-1000F Auto Refractometer in high refractive errors.

The manifest refractions of 37 high myopic and 16 high hypermetropic eyes in a total of 28 patients, aged 5 to 42 years, were determined on the Nikon NR-1000F Auto Refractometer. The data obtained were compared with the final clinical prescriptions for these eyes and analysed for degree of agreement for the spherical equivalents, sphere components, and cylinder powers and axes. The Auto Refractometer recordings for all the different refractive components were observed to skew towards more minus in the high myopic eyes but more plus in the high hypermetropes. The possible significance of these skewing patterns is discussed with reference to our earlier studies.

Adolescent↗
PubMed1985

Disease-associated visual image degradation and spherical refractive errors in children.

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between disease states which involve visual image degradation and refractive error. Refractive data from 1023 normal vision children were used as a control. The low vision children were grouped according to their disease classification and the acknowledged age-of-onset of their visual disability. It was found that there was an overall inability to emmetropize and a trend towards myopia. It was also observed that the diseases which led to myopia were associated with a peripheral or peripheral plus central impairment of vision and that those conditions in which foveal vision was primarily impaired showed a mild hypermetropic trend. Eyes in which the visual impairment was not congenital but occurred before the age of 3 years tended to develop hypermetropia. The deviation from emmetropia decreased with increasing age-of-onset of the visual impairment, as did the variation about the mean refraction. The plastic period for emmetropization is estimated to end at 8 to 9 years of age.

Adolescent↗
PubMed1994

Refractive errors among engineering students in Norway.

This study reveals the prevalence of refractive errors in a group of young adults (mean age 20.6 years) exposed to high educational demands, including much reading. In all, 224 (117 females, 107 males) first-year engineering students were subjectively refracted. A prevalence of myopia of 46.9% (right eye), 49.1% (left eye) and 42.9% (both eyes), and a prevalence of hyperopia of 29.5% (right eye), 28.1% (left eye) and 23.2% (both eyes) was detected. The mean refractive error in the whole group was -0.6 +/- 2.2 D (right eye), -0.7 +/- 2.4 D (left eye) and -0.7 +/- 2.3 D (both eyes). As many as 56.4% (n = 57) of the myopic students had either no corrective lenses (11.9%, n = 12) or had their first corrective lenses prescribed at the age of 16 years or later (44.6%, n = 45). There was no significant difference in the prevalence of myopia between female and male students. No significant difference regarding body height was found among men in the different groups of refractive errors, but a significant difference was detected among women. We found no statistically significant relationship between intraocular pressure and any refractive error among men or women.

Adult↗