Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “refractive error”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2003

Laser in situ keratomileusis as treatment for anisometropia after scleral buckling surgery.

Scleral buckling is an excellent procedure for retinal reattachment but can induce disabling refractive errors. Laser in situ keratomileusis (LASIK) has been proven effective for the reduction of refractive errors induced by ophthalmic surgery. We describe the case of a 53-year-old man who developed symptomatic anisometropia after placement of a scleral buckle for repair of a rhegmatogenous retinal detachment (RD). After the scleral buckling procedure, he retained excellent best corrected visual acuity but could not tolerate spectacle or contact lens correction. Thirty-four months after the scleral buckling procedure, LASIK was performed to correct myopic astigmatism with excellent refractive and functional results. This case demonstrates that LASIK may be safe and effective for the correction of refractive errors induced by RD repair.

Anisometropia↗
PubMed1980

Clinical evaluation of intraocular lens calculations.

The DBR-300 A-Scan ultrasonic unit was used to evaluate 100 patients preoperatively. Intraocular lens power was calculated using the formula supplied with the instrument and the accuracy of the instrument was then evaluated. It was determined that 54% of our patients were within +/- 1.00 diopter of the calculated refractive error and that 85% of the patients were within +/- 2.00 diopters and that 97% were within +/- 3.00 diopters. Only 3% of our patients had greater than a 3.00-diopter difference between predicted and actual postoperative refractive error. A standard 3.2-mm anterior chamber depth was utilized for Choyce lenses and 3.4 mm ACD was utilized for Medallion lenses. No single factor could be found to account for the slight tendency toward myopia, although several were found to contribute. No single factor was found to contribute to large errors, though the 3% of patients with greater than three diopters variation from the predicted refractive error demonstrated high degrees of cylinder or corneal astigmatism postoperatively as compared to preoperatively. Though we are presently in the process of reviewing ACD postoperatively, one would not suggest any drastic changes in the values at this time due to the overall accuracy obtained. Certainly though small adjustments may be made in the Binkhorst formula in the future, this is yet to be proven clinically.

Humans↗
PubMed2002

Refractive change in response to acute hyperbaric stress in refractive surgery patients.

PURPOSE: To determine whether acute hyperbaric stress affects visual acuity or refractive power after keratorefractive surgery. SETTING: Clinical multiplace hyperbaric chamber and ophthalmology clinic, University of California, San Diego, California, USA. METHODS: This prospective convenience sample study included 3 groups: 3 patients who had had bilateral myopic radial keratotomy (RK); 2 who had had bilateral myopic laser in situ keratomileusis (LASIK); and 4 control subjects who had no previous corneal refractive surgery or ocular pathology but had a myopic refractive error (-1.25 to -8.38 diopters [D]) similar to that in the treated patients before refractive surgery. One additional patient had had unilateral LASIK only and was included in the LASIK and control groups. Best spectacle-corrected visual acuity (BSCVA), manifest spherocylindrical refractive error, and intraocular pressure were measured at baseline, at 4 atmospheres absolute (atm abs), and on return to ambient pressure. Corneal pachymetry and keratometry were measured at baseline and on return to ambient pressure. RESULTS: The mean BSCVA changed from 0.06 logMAR (20/25 Snellen equivalent) at baseline to 0.10 logMAR (20/25) at 4 atm abs in the RK group and from 0.00 logMAR (20/20) to -0.06 logMAR (20/15) in the LASIK group; it did not change in the control group. The mean refractive error changed from 0.25 D at baseline to 0.50 D at 4 atm abs in the RK group, from -0.90 to -1.02 D in the LASIK group, and from -4.58 to -4.53 D in the control group. CONCLUSIONS: Acute hyperbaric stress did not appear to alter refractive power after corneal surgery.

Adult↗
PubMed2000

Change in central corneal thickness following laser in situ keratomileusis for myopia.

Central corneal thickness alterations may cause residual refractive errors following laser in situ keratomileusis (LASIK). This study reports associations between central corneal thickness alterations and residual refractive error following uncomplicated LASIK. Ninety-one myopic patients with a mean refractive correction of -3.91+/-3.2 DS / -0.66+/-0.3 DC were evaluated. Central corneal thickness was measured prior to, during and following surgery and 2 months later using ultrasound pachometry Results indicate increased tissue removal (94+/-33 microm; mean +/- SD) compared to the nominal Nidek value (52+/-24 microm, P<0.001). Twenty-four hours later the tissue removal was 46+/-27 microm. There was no association between altered central corneal thickness and ablation depth (r = 0.058, P = 0.454). Central corneal thickness change was inversely proportional to residual refractive error (r = -0.364, P<0.01). Increased tissue removal may occur due to rapid stromal dehydration. Central corneal thickness changes between 24 h, and 2 months after surgery were constant over a range of ablation depths, which may partly explain the stability of LASIK procedures over a range of corrections.

Adult↗
PubMed2005

Nine-year refractive changes in the Barbados Eye Studies.

PURPOSE: To describe 9-year changes in refractive errors and estimate incidence of myopia and hyperopia in adults of African-descent, along with associated risk factors. METHODS: The 9-year follow-up of the Barbados Eye Studies (1997-2003) reexamined 2793 surviving cohort members (81% participation). Refractive errors were determined by automated refraction. Myopia/hyperopia were defined as spherical equivalent < -0.5 diopters (D)/> +0.5 D, and the cutoff for moderate-high myopia/hyperopia was 3.0 D. Incidence rates of myopia/hyperopia were estimated by the product-limit approach, based on eyes without such conditions at baseline. Risk factors were evaluated by logistic regression in discrete time hazard models. RESULTS: Nine-year refraction changes varied by age. Persons aged 40 to 49 years experienced hyperopic shifts (median, +0.38 D), whereas persons > or =60 years had myopic shifts (median, -0.75D). Overall 9-year incidence was 12.0% for myopia and 29.5% for hyperopia; rates were 3.6% and 2.0% for moderate-high myopia and hyperopia, respectively. Myopia risk increased with age, baseline nuclear lens opacities (risk ratio [RR] = 1.7; 95% confidence interval [CI]: 1.01-2.9), glaucoma (RR = 6.0, 95% CI: 3.9-9.3), and ocular hypertension (RR = 2.0, 95% CI: 1.3-3.0), while cortical lens opacities decreased risk (RR = 0.6, 95% CI: 0.4-0.9). Incidence of moderate-high myopia was also related to baseline age, nuclear opacities, glaucoma, male gender (RR = 1.7, 95% CI: 1.0-2.8), and diabetes history (RR = 1.9, 95% CI: 1.01-3.5). Hyperopia risk decreased with older age, male gender, and glaucoma diagnosis. CONCLUSIONS: Refractive errors continue to develop frequently in older adults. Nuclear lens opacities, glaucoma, and diabetes increase the risk of older-onset myopia, a result of public health relevance to this and similar African-origin populations.

Adult↗
PubMed2006

Prevalence of visual impairment in the United States.

CONTEXT: The prevalence of visual impairment in the US public has not been surveyed nationally in several decades. OBJECTIVE: To estimate the number of US individuals aged 12 years or older who have impaired distance vision due to uncorrected refractive error. DESIGN, SETTING, AND PARTICIPANTS: The National Health and Nutrition Examination Survey (NHANES), using a multistage probability sampling design, included a vision evaluation in a mobile examination center. Visual acuity data were obtained from 13,265 of 14,203 participants (93.4%) who visited the mobile examination center in 1999-2002. Visual impairment was defined as presenting distance visual acuity of 20/50 or worse in the better-seeing eye. Visual impairment due to uncorrected refractive error was defined as (presenting) visual impairment that improved, aided by automated refraction results, to 20/40 or better in the better-seeing eye. MAIN OUTCOME MEASURES: Presenting distance visual acuity (measured with usual corrective lenses, if any) and distance visual acuity after automated refraction. RESULTS: Overall, 1190 study participants had visual impairment (weighted prevalence, 6.4%; 95% confidence interval [CI], 6.0%-6.8%), and of these, 83.3% could achieve good visual acuity with correction (95% CI, 80.9%-85.8%). Extrapolating these findings to the general US population, approximately 14 million individuals aged 12 years or older have visual impairment (defined as distance visual acuity of 20/50 or worse), and of these, more than 11 million individuals could have their vision improved to 20/40 or better with refractive correction. CONCLUSIONS: Visual impairment due to uncorrected refractive error is a common condition in the United States. Providing appropriate refractive correction to those individuals whose vision can be improved is an important public health endeavor with implications for safety and quality of life.

Adolescent↗
PubMedDate not supplied

Analysis of the National Health and Nutrition Examination Survey. Comment on "Prevalence of visual impairment in the United States", by S Vitale, MF Cotch, and RD Sperduto. JAMA 295:2158-63, 2006.

CONTEXT: The prevalence of visual impairment in the U.S. public has not been surveyed nationally in several decades. OBJECTIVE: To estimate the number of U.S. individuals aged 12 years or older who have impaired distance vision due to uncorrected refractive error. DESIGN, SETTING, AND PARTICIPANTS: The National Health and Nutrition Examination Survey (NHANES), using a multistage probability sampling design, included a vision evaluation in a mobile examination center. Visual acuity data were obtained from 13,265 of 14,203 participants (93.4%) who visited the mobile examination center in 1999-2002. Visual impairment was defined as presenting distance visual acuity of 20/50 or worse in the better-seeing eye. Visual impairment due to uncorrected refractive error was defined as (presenting) visual impairment that improved, aided by automated refraction results, to 20/40 or better in the better-seeing eye. MAIN OUTCOME MEASURES: Presenting distance visual acuity (measured with usual corrective lenses, if any) and distance visual acuity after automated refraction. RESULTS: Overall, 1,190 study participants had visual impairment (weighted prevalence, 6.4%; 95% confidence interval [CI], 6.0-6.8%), and of these, 83.3% could achieve good visual acuity with correction (95% CI, 80.9-85.8%). Extrapolating these findings to the general U.S. population, approximately 14 million individuals aged 12 years or older have visual impairment (defined as distance visual acuity of 20/50 or worse), and of these, more than 11 million individuals could have their vision improved to 20/40 or better with refractive correction. CONCLUSIONS: Visual impairment due to uncorrected refractive error is a common condition in the United States. Providing appropriate refractive correction to those individuals whose vision can be improved is an important public health endeavor with implications for safety and quality of life.

Humans↗
PubMed2003

Causes of low vision and blindness in rural Indonesia.

AIM: To determine the prevalence rates and major contributing causes of low vision and blindness in adults in a rural setting in Indonesia METHODS: A population based prevalence survey of adults 21 years or older (n=989) was conducted in five rural villages and one provincial town in Sumatra, Indonesia. One stage household cluster sampling procedure was employed where 100 households were randomly selected from each village or town. Bilateral low vision was defined as habitual VA (measured using tumbling "E" logMAR charts) in the better eye worse than 6/18 and 3/60 or better, based on the WHO criteria. Bilateral blindness was defined as habitual VA worse than 3/60 in the better eye. The anterior segment and lens of subjects with low vision or blindness (both unilateral and bilateral) (n=66) were examined using a portable slit lamp and fundus examination was performed using indirect ophthalmoscopy. RESULTS: The overall age adjusted (adjusted to the 1990 Indonesia census population) prevalence rate of bilateral low vision was 5.8% (95% confidence interval (CI) 4.2 to 7.4) and bilateral blindness was 2.2% (95% CI 1.1 to 3.2). The rates of low vision and blindness increased with age. The major contributing causes for bilateral low vision were cataract (61.3%), uncorrected refractive error (12.9%), and amblyopia (12.9%), and the major cause of bilateral blindness was cataract (62.5%). The major causes of unilateral low vision were cataract (48.0%) and uncorrected refractive error (12.0%), and major causes of unilateral blindness were amblyopia (50.0%) and trauma (50.0%). CONCLUSIONS: The rates of habitual low vision and blindness in provincial Sumatra, Indonesia, are similar to other developing rural countries in Asia. Blindness is largely preventable, as the major contributing causes (cataract and uncorrected refractive error) are amenable to treatment.

Adult↗
PubMed2004

The development of the refractive state in the newborn Thomson gazelle.

Changes in refractive error during the first 3 months of life were studied retinoscopically in six Thomson gazelles ( Gazella thomsoni). Animals were hand-raised to allow repeat testing over time without chemical restraint. Refraction results were correlated with ultrasound measurements of intraocular dimensions, and with values in adult gazelles. Gazelles are born hyperopic with a mean refractive error of 3.44+/-0.31 D. By day 50, the animals are virtually emmetropic (0.13+/-0.21 D) and remain so in adulthood (0.03+/-0.09 D). The refractive error is highly correlated with the axial length ( r(2)=0.96) and with the vitreous chamber depth ( r(2)=0.83), but not with anterior chamber depth. Significant with-the-rule astigmatism was recorded ( P<0.001).

Aging↗
PubMed2001

Refractive change after dorzolamide use in patients with primary open-angle glaucoma and ocular hypertension.

The purpose of this study was to evaluate refractive and anterior chamber depth changes after short-term dorzolamide use in patients with primary open-angle glaucoma (POAG) and ocular hypertension (OH). This study was prospective and non-comparative and included 34 patients. Baseline refraction and anterior chamber depth were compared to the refraction and anterior chamber depth 14 days after commencing dorzolamide to determine if refraction or anterior chamber depth had been affected. Before dorzolamide use, the mean refractive error was -0.88 +/- 3.53 D (+/-SD). The mean refractive error was -0.94 +/- 3.65 D (+/-SD) two hours post-dose after 14 days of dorzolamide use, which was not significantly different (P = 0.50). The mean pre-treatment anterior chamber depth was 3.088 +/- 0.385 mm (+/-SD), which did not differ significantly from the post-treatment anterior chamber depth mean of 3.092 +/- 0.389 mm (+/-SD) (P = 0.88). The results of the study show that refraction and anterior chamber depth are not significantly altered by short-term dorzolamide use in patients with POAG and OH with no history of previous dorzolamide use.

Adolescent↗
PubMed1996

Repeatability and reproducibility of optic disc measurement with the Zeiss 4-mirror contact lens.

BACKGROUND: A simple clinical quantitative method of optic disc diameter measurement using a 4-mirror gonioscope contact lens has been described recently. METHODS: Intraobserver and interobserver variations are assessed on 77 eyes of 41 patients. Of these eyes, 63 had refractive errors within 3 diopters of emmetropia. The disc was measured by projecting a slit beam of known height onto the disc. RESULTS: Intraobserver variation: the coefficient of variation was 3.04% for observer 1 (experienced) and 4.76% for observer 2 (novice). The mean of the three measurements by the two observers was not significantly different (P=0.2318). For observer 1, the mean variance of the eyes with higher refractive errors did not differ significantly from the eyes with lower refractive errors. Interobserver variation: the coefficient of variation was 4.52%. The measurements for the novice were slightly larger the smallest discs and slightly smaller for the largest discs (regression analysis P=0.0209). CONCLUSION: Repeatability and reproducibility for this method are comparable with other methods of measurement. Until experienced with the technique, the authors recommend that the mean of three readings is used.

Glaucoma↗
PubMed1996

Vitreous chamber elongation is responsible for myopia development in a young adult.

In this case report, we present 3 years of longitudinal, refractive component data for a young adult who became myopic and progressed in myopia (late-onset myopia, LOM) during that period. We found a high correlation between refractive error and axial length (AL). The axial elongation was a consequence of the change in the vitreous chamber depth (VCD). Furthermore, the change in AL and VCD corresponded quantitatively to the change in refractive error. Corneal curvature change was not correlated with refractive error change. These findings support the suggestion that VCD is the refractive component that changes in LOM development.

Adult↗
PubMed1978

The AO SR IIItm Subjective Refraction System: comparison with Phoropter measures.

Subjective measures of refractive error were obtained on 530 eyes using the AO SR III Subjective refraction System (operated by a trained secretary) and using a phoropter (operated by optometrists and optometry students) in a clinical setting. Comparison of these measures from the present study and from a previous study by Bannon leads us to conclude that the SR III instrument is capable of estimating refractive error with good agreement with conventional refractive methods. Comparison with the Acuity Systems 6600 Auto-RefractorTM was also made.

Adolescent↗
PubMed2003

Optic disc morphology in south India: the Vellore Eye Study.

AIM: To evaluate the morphology of the optic nerve head in an unselected population group in south India. METHODS: The study included 70 subjects forming a population based sample, selected in a random manner. Mean age was 47.5 (SD 8.7) years, mean refractive error measured -0.07 (1.11) dioptres (range -4.50 to +2.50 dioptres). Optic disc slides were morphometrically analysed. RESULTS: Mean optic disc area measured 2.58 (0.65) mm(2). It was statistically independent of age and refractive error. Optic disc shape was slightly vertically oval. Mean neuroretinal rim area was 1.60 (0.37) mm(2). It was significantly and positively correlated with optic disc size and optic cup size. It was independent of age, sex, refractive error, and axial length. In all subjects included in the study, the rim was smallest in the temporal horizontal optic disc sector. Mean horizontal cup/disc diameter ratio (0.66 (0.07)) was significantly (p<0.001) higher than the mean vertical cup/disc diameter ratio (0.56 (0.08)). Both ratios were highly significantly (p <0.001) and positively correlated with optic disc size. The alpha zone of parapapillary atrophy (0.84 (0.29) mm(2)), and beta zone (0.13 (0.38) mm(2)), respectively, occurred in 69 (98.6%) subjects and in eight (11.4%) subjects, respectively. They were significantly larger in the temporal horizontal sector. The alpha zone was significantly (p<0.001) larger and occurred significantly more often than beta zone. Retinal arterioles and venules were wider, and in spatial correlation, the visibility of the retinal nerve fibre layer was significantly better, in the temporal inferior disc arcade and the temporal superior arcade than in the nasal superior arcade and the nasal inferior vessel arcade. Except for the absolute size measurements these optic nerve head parameters did not differ markedly (p >0.05) from the values found in white people. CONCLUSIONS: South Indians and white people do not show marked differences in the morphology of the optic nerve head as measured by morphometric optic disc parameters, with the possible exception of the absolute optic disc dimensions.

Adult↗
PubMed1987

Mensuration data in infant eyes with unilateral congenital cataracts.

The purpose of this study was to determine the size and shape of infant eyes having a unilateral congenital cataract. Fourteen infants presenting consecutively with a unilateral congenital cataract were studied. Ages ranged from 1.3 to 6 months (mean 3.7 months). Corneal curvature ranged from 43.00 to 49.50 D (mean 45.6 D). Refractive error at the corneal plane ranged from +23.50 to +34.00 D (mean +28.07 D). The axial length ranged from 16.49 to 20.09 mm (mean 18.41 mm). Microcornea was found in eight infants. There was rapid growth in eye size from normal neonatal dimensions. No significant relation was found among the following: corneal curvature and age; refractive error and age; axial length and age or presence of microcornea; and corneal curvature and refractive error. Corneal vault may be an important factor in fitting contact lenses to aphakic infants. Contact lenses for infants should be designed based on the dimensions of the infant eye.

Age Factors↗
PubMed1991

Optimal astigmatism to enhance depth of focus after cataract surgery.

A small amount of myopic astigmatism can enhance the depth of focus of the pseudophakic eye, optimally providing at least 20/30 visual acuity for both near and distance fixation. For given spherocylindrical refractive errors and fixation distances, the cross-sectional area of Sturm's conoid at the retina was calculated for a schematic eye. These data were used to determine the optimal astigmatic error needed to obtain maximum depth of focus and least theoretical blur for any given spherical equivalent refractive error. Optimal depth of focus was obtained when the plus cylindrical component equaled negative sphere - 0.25 diopters. The near and distance visual acuities of ten pseudophakic patients with induced refractive errors were highly correlated with this model. Low myopic astigmatism after cataract surgery may represent an alternative to multifocal intraocular lenses by providing spectacle independence.

Astigmatism↗
PubMed2000

[Intraocular lens calculation for cataract treated with photorefractive keratectomy using ray tracing method].

PURPOSE: Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation. METHOD: Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured. RESULTS: The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was--1.00 D. CONCLUSION: The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.

Cataract↗
PubMed2005

Visual acuity and the causes of visual loss in a population-based sample of 6-year-old Australian children.

PURPOSE: To describe the distribution of visual acuity and causes of visual loss in a representative sample of Australian schoolchildren. DESIGN: Population-based cross-sectional study. PARTICIPANTS: One thousand seven hundred thirty-eight predominantly 6-year old children examined during 2003 to 2004. METHODS: Logarithm of the minimum angle of resolution (logMAR) visual acuity was measured in both eyes before and after pinhole correction and with spectacles if worn. Cycloplegic autorefraction (cyclopentolate) and detailed dilated fundus examination were performed. MAIN OUTCOME MEASURES: Visual impairment was defined as any (visual acuity <20/40; <40 letters) or severe (visual acuity < or =20/200; 0-5 letters) for both better and worse eyes. Myopia was defined as spherical equivalent (SE) refraction < or =-0.50 diopters (D), and hyperopia as SE refraction > or =+2.0 D, deemed significant when > or =+3.0 D. Astigmatism was defined as cylinder > or =1.0 D and anisometropia as SE refraction difference between eyes at least 1.0 D. Amblyopia was defined as corrected visual acuity <0.3 logMAR units (<20/40; <40 letters) in the affected eye not attributable to any underlying structural abnormality of the eye or visual pathway, together with a 2-logMAR line difference between the eyes and presence of an amblyogenic risk factor. RESULTS: The mean visual acuity of this sample was 20/25 (49.3 letters). Uncorrected visual impairment was found in the better eye of 23 children (1.3%) and in the worse eye of 71 children (4.1%). The prevalence was higher in girls than boys and among children of lower socioeconomic status. Refractive error was the most frequent cause, accounting for 69.0%, followed by amblyopia (22.5%). Astigmatism was the principle refractive error causing visual impairment and was frequently uncorrected. Presenting visual impairment (using current glasses if worn) was found in the better and worse eyes of 15 children (0.9%) and 54 children (2.8%), respectively. This was mainly due to under corrected or uncorrected refractive error. CONCLUSIONS: This study has documented a relatively low prevalence of visual impairment in a population of Australian children. Uncorrected astigmatism and amblyopia were the most frequent causes.

Child↗