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At least 613 records · Page 34Linked to original sources
PubMedDate not supplied

Long-term refractive and phoric changes in visual display unit (VDU) operators.

PURPOSE: This study assessed the phoric and refractive changes possibly caused by visual display unit (VDU) activity. METHODS: In a longitudinal trial nearly 6000 VDU operators received two ophthalmological examinations at intervals ranging from 34 to 43 months. The findings from the two examinations were correlated to VDU work (hours daily and years of VDU work), age and sex. RESULTS: Changes in the refractive state seemed to be mainly age-related. There was a slight tendency toward hyperopia (imbalance of latent hyperopia). CONCLUSIONS: In the analysis of ocular motility, the results show no worsening capable of causing a definitive change from heterophoria to heterotropia. Heterophoric subjects, however, tend to improve both with regular office work and with additional VDU activity.

Adolescent↗
PubMed2005

Little evidence for an epidemic of myopia in Australian primary school children over the last 30 years.

BACKGROUND: Recently reported prevalences of myopia in primary school children vary greatly in different regions of the world. This study aimed to estimate the prevalence of refractive errors in an unselected urban population of young primary school children in eastern Sydney, Australia, between 1998 and 2004, for comparison with our previously published data gathered using the same protocols and other Australian studies over the last 30 years. METHODS: Right eye refractive data from non-cycloplegic retinoscopy was analysed for 1,936 children aged 4 to 12 years who underwent a full eye examination whilst on a vision science excursion to the Vision Education Centre Clinic at the University of New South Wales. Myopia was defined as spherical equivalents equal to or less than -0.50 D, and hyperopia as spherical equivalents greater than +0.50 D. RESULTS: The mean spherical equivalent decreased significantly (p < 0.0001) with age from +0.73 +/- 0.1D (SE) at age 4 to +0.21 +/- 0.11D at age 12 years. The proportion of children across all ages with myopia of -0.50D or more was 8.4%, ranging from 2.3% of 4 year olds to 14.7% of 12 year olds. Hyperopia greater than +0.50D was present in 38.4%. A 3-way ANOVA for cohort, age and gender of both the current and our previous data showed a significant main effect for age (p < 0.0001) but not for cohort (p = 0.134) or gender (p = 0.61). CONCLUSIONS: Comparison of our new data with our early 1990s data and that from studies of over 8,000 Australian non-clinical rural and urban children in the 1970's and 1980's provided no evidence for the rapidly increasing prevalence of myopia described elsewhere in the world. In fact, the prevalence of myopia in Australian children continues to be significantly lower than that reported in Asia and North America despite changing demographics. This raises the issue of whether these results are a reflection of Australia's stable educational system and lifestyle over the last 30 years.

Child↗
PubMed1979

Cavernous hemangioma of the orbit.

The clinical and pathological data of 66 patients with orbital cavernous hemangioma are presented. This tumor occurs in females more frequently than in males, and has its peak incidence in early middle age. Visual disability results from a high degree of relative hyperopia or from optic-nerve compression. Postural or temporal variation is proptosis is not characteristic. Multiple cavernous hemangiomas are rare, but may occur simultaneously or separated by long intervals. In this series, incompletely excised lesions did not cause recurrent proptosis. Relative hyperopia may persist, in spite of complete removal of the tumor. Improved preoperative localization with modern techniques appears to be reducing the morbidity associated with surgical excision of the lesion. A local hemodynamic disturbance may initiate proliferation of vascular channels that undergo progressive ectasia. Growth of the lesion may occur intrinsically by the budding-off of capillary channels from cavernous spaces into the interstitium. Clinical and pathological findings fail to demonstrate any relationship between this lesion and capillary hemangioma of childhood.

Adolescent↗
PubMedDate not supplied

Comparison of on- and off-axis photorefraction with cycloplegic retinoscopy in infants.

We have compared the performance of an off-axis (knife-edge) photorefractor with that of an on-axis (isotropic) system. Normal infants and children between the ages of 8 and 208 weeks were photographed with each camera both with and without cycloplegia. Refractive errors were estimated for each technique based on equations derived from ray-tracing. These refractions were compared to the results of retinoscopy under cycloplegia. Sensitivity and specificity of the two photorefraction systems were evaluated as a function of the magnitude of meridional hyperopia defined by retinoscopy. We also examined the effect of varying the photorefraction screening criterion. Thirteen percent of the infants in the screening sample presented with +3.50 diopters or more of meridional hyperopia. Using this level of ametropia as a referral criterion, the sensitivity and specificity of the off-axis system for infants without cycloplegia were 83% and 72%, respectively. For the on-axis system, sensitivity and specificity values were 85% and 53%. The use of cycloplegics did not significantly improve the performance of either system, but rather their use degraded the specificity of the on-axis system in the presence of moderate refractive errors. The results of the present study indicate that both on- and off-axis systems are effective in identifying highly ametropic infants, but that the off-axis system results in significantly fewer false positives. Moreover, the off-axis system has the advantages of an inherently greater dynamic range for a fixed camera design, and also more easily interpreted photographs.

Child, Preschool↗
PubMedDate not supplied

Early-onset accommodative esotropia.

PURPOSE: To determine the frequency of accommodative esotropia with onset by 6 months of age; to determine if the presence or absence of characteristics usually associated with infantile esotropia can help in the diagnosis; and to determine if antiaccommodative therapy is adequate treatment for the esotropia. METHODS: The charts of 100 patients with infantile esotropia, seen over a 2-year period (September 1995 to September 1997), were reviewed. We identified those with at least 2.25 diopters (D) of hyperopia and determined the presence of large angle esotropia (> 30 to 40 prism diopters [delta]), amblyopia, inferior oblique overaction, dissociated vertical deviation, latent nystagmus, and cross-fixation. The success of antiaccommodative therapy, if attempted, was also evaluated. RESULTS: Of 100 patients with infantile esotropia, 15 (15%) were found to have at least +2.25 D. This represented 8% of all patients with accommodative esotropia seen over the same time period. The average age at initial examination was 21 months, although the reported age of onset in all cases was 6 months or less. Two had surgery before presenting to our institute. Eleven of 13 (84%) had 40 delta or less. Six (40%) of the 15 had amblyopia, 5 (33%) had inferior oblique overaction, 3 (20%) had dissociated vertical deviation, 1 (7%) had latent nystagmus, and 4 (27%) had cross-fixation. Of the 13, 7 were given glasses initially, with 3 being fully corrected. Six were not given glasses, all had surgery, and all were given glasses postoperatively for a residual esotropia. CONCLUSION: Fifteen percent of infantile esotropia patients and 8% of accommodative esotropia patients have infantile accommodative esotropia. Other characteristics of infantile esotropia may be present, but are less frequent, and at least 40% are fully corrected with spectacles indicating that when the hyperopia is 2.25 D or greater, antiaccommodative therapy should be instituted before surgery.

Accommodation, Ocular↗
PubMedDate not supplied

Bilateral comparison of photorefractive keratectomy for myopia using two excimer lasers.

PURPOSE: The aim of this study was to compare the results of excimer laser photorefractive keratectomy (PRK) in patients who underwent PRK using the Summit Apex (Omnimed) excimer laser in one eye and the Nidek EC-5000 excimer laser in the other. METHODS: All consecutive patients who underwent PRK with the Summit Apex laser (Omnimed) in one eye and the Nidek laser (EC-5000) in the second and had at least 12 months of follow-up were included in this retrospective study (n=30). Uncorrected and spectacle-corrected visual acuity, final spherical equivalent refraction, and grade of subepithelial haze were compared. The average preoperative spherical equivalent refraction of eyes treated with the Summit laser was -6.00 D (range, -2.50 to -8.75 D), and for Nidek-treated eyes it was -5.57 D (range, -2.50 to -8.80 D). RESULTS: Forty-seven percent of Summit-treated eyes and 53% of Nidek-treated eyes had uncorrected visual acuity of 6/6 or better; 61% of Summit-treated eyes and 63% of Nidek-treated eyes had uncorrected visual acuity of 6/7.5 or better; 95% of Summit-treated eyes and 95% of Nidek-treated eyes had uncorrected visual acuity of 6/12 or better (difference not statistically significant). Seventy-three percent of eyes treated with the Summit laser and 80% of eyes treated with the Nidek laser had a postoperative refraction within +/-0.50 D of emmetropia; 97% of Summit-treated eyes and 87% of Nidek-treated eyes had a postoperative spherical equivalent refraction within +/-1.00 D of emmetropia; the difference between the two lasers was not statistically significant. However, the percent of eyes with persistent hyperopia was smaller in the Nidek group after 3 months (P=.0062) and after 6 months (P=.07) than in the Summit group. Videokeratography was not done. CONCLUSION: Both lasers were effective with relatively low side effects. No significant difference was found between the two lasers in postoperative uncorrected visual acuity or refractive outcome. Eyes operated with the Nidek laser had less persistent hyperopia and stabilized earlier.

Adult↗
PubMed1992

Recent developments in refractive corneal surgery.

The 4- and 5-year results of the Prospective Evaluation of Radial Keratotomy Study reveal a hyperopic shift of more than 1.0 D within the follow-up time in 22% and 24%, respectively, of the eyes that underwent radial keratotomy. The number of eyes with this complication increased progressively from 6 months to 4 years. Attempts to correct this progressive hyperopia are discussed. Results of clinical studies of myopic photorefractive keratectomy performed with the excimer laser are reviewed. Regarding safety and short-term efficacy, photorefractive keratectomy is a promising technique. In the past, corneal topography has been interpreted qualitatively. Ray-tracing analysis now allows quantitative estimation of the influence of aspheric corneas on the degradation of the retinal image. Three approaches to correct hyperopia, radial thermokeratoplasty, laser thermokeratoplasty, and hexagonal keratotomy are reviewed and discussed. Additional concave intraocular lenses for correction of high myopia are still undergoing clinical evaluation. Endothelial damage is the most dangerous short-term complication of implantation with these lenses.

Cornea↗
PubMed1999

Refractive errors and visual acuity impairment among self-selected Hispanic, white, and black adults examined by the UCLA Mobile Eye Clinic.

BACKGROUND: Occurrence of refractive errors and uncorrected visual acuity impairment among self-selected, indigent, medically underserved Hispanic, white, and black adults examined by the staff of the UCLA Mobile Eye Clinic (MEC) are described in this study and compared to population-based studies. METHODS: The study sample consisted of all 2,970 Hispanic, 1,228 white, and 1,028 black participants, for a total of 5,226 self-selected adults, ages 25 to 74 years, who received vision screenings and eye examinations by the staff of the UCLA MEC from 1987 to 1997. Tests consisted of visual acuity, refractive error, intraocular pressure, retinoscopy, slit-lamp biomicroscopy, direct ophthalmoscopic examination, and indirect ophthalmoloscopy with pupillary dilation. Levels of visual acuity impairment were defined as mild (20/50-20/80), moderate (20/100), or severe (20/200 or worse) in either eye. RESULTS: Self-selected whites in this study had higher rates of astigmatism, anisometropia, and hyperopia, while myopia was higher among self-selected blacks. Myopia and hyperopia occurred more frequently among younger age groups for all ethnic groups. Whites had a higher occurrence of mild, moderate, and severe visual acuity impairment, as compared with Hispanics and blacks. CONCLUSIONS: Both refractive errors and impaired visual acuity of this self-selected sample are similar to those of adults from the National Health and Nutrition Examination Survey, Hispanic Health and Nutrition Examination Survey, and the Baltimore Eye Survey. The data presented in this study provide a crude estimate of the occurrence of refractive errors and impaired visual acuity among self-selected, medically underserved, indigent Hispanic, white, and black adults in the Los Angeles area.

Adolescent↗
PubMed2000

Albinism: its implications for refractive development.

PURPOSE: Albinism involves the mutation of one or more of the genes associated with melanin synthesis and has many ramifications for vision. This study focuses on the refractive implications of albinism in the context of emmetropization. METHODS: Refractive, biometric, and visual acuity data were collected for a group of 25 albino individuals that included the following: 18 oculocutaneous (13 tyrosine positive, 5 tyrosine negative); 7 ocular (2 autosomal recessive, 5 sex-linked recessive). Their age range was 3 to 51 years. All exhibited horizontal pendular nystagmus. RESULTS: There were no statistically significant differences relating to albino subtype for any of the measured parameters. All the subjects had reduced visual acuity (mean: 0.90, logMAR) and overall, there was a bias toward hyperopia in their refractive errors (mean: + 1.07 D). However the refractive errors of the group covered a broad range (SD: 4.67 D) and included both high myopia and high hyperopia. An axial origin to the refractive errors is implied by the high correlation between refractive errors and axial lengths. Refractive astigmatism averaged 2.37 D and was consistently with-the-rule and highly correlated with corneal astigmatism, which was also with-the-rule. Meridional analysis of the refractive data indicated that the vertical meridian for hyperopic subjects was consistently nearer emmetropia compared to their horizontal meridian. Myopic subjects showed the opposite trend. CONCLUSIONS: The overall refractive profile of the subjects is consistent with emmetropization being impaired in albinism. However, the refractive errors of hyperopic subjects also can be explained in terms of "meridional emmetropization." The contrasting refractive profiles of myopic subjects may reflect operational constraints of the emmetropization process.

Adolescent↗
PubMed2000

Estimation of projection errors in human ocular fundus imaging.

Photogrammetric analysis of features in human ocular fundus images is affected by various sources of errors, for example aberrations of the camera and eye optics. Another--usually disregarded--type of distortion arises from projecting the near spherical shape of the fundus onto a planar imaging device. In this paper we quantify such projection errors based on geometrical analysis of the reduced model eye imaged by a pinhole camera. The projection error found near the edge of a 50 degrees fundus image is 24%. In addition, the influence of axial ametropia is investigated for both myopia and hyperopia. The projection errors found in hyperopia are similar to those in emmetropia, but decrease in myopia. Spherical as well as ellipsoidal eye shapes were used in the above calculation and their effect was compared. Our results suggest that the simple spherical eye shape is sufficient for correcting projection distortions within a range of ametropia from -5 to +5 diopters.

Artifacts↗
PubMedDate not supplied

A survey on refractive error and strabismus among children in a school at Aligarh.

An ophthalmic survey of 310 school going children in the age group of 4-12 years was done. 41 children (13.2%) were found to have a vision of less than 6/6 in one or both eyes. Myopia of 0.5 D or more and hyperopia of +2 D or more or astigmatism of 1 D or more in one or both eyes were seen in 74 children (22.9%). There was a tendency for a decrease in hyperopia and an increase in myopia with advancing age. Astigmatic error of 1 D or less was seen in 12 eyes (1.93%) and anisometropia of more than 1 D was present in 11 cases (3.5%). Hypertropia was more in female children whereas myopia had a nearly equal distribution in both sexes. There was heterophoria and manifest strabismus which showed a gradual increase with advancing age. This study was compared to few other studies undertaken in the past.

Child↗
PubMed2001

Overview of refractive surgery.

Patients with myopia, hyperopia and astigmatism can now reduce or eliminate their dependence on contact lenses and eyeglasses through refractive surgery that includes radial keratotomy (RK), photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), laser thermal keratoplasty (LTK) and intrastromal corneal rings (ICR). Since the approval of the excimer laser in 1995, the popularity of RK has declined because of the superior outcomes from PRK and LASIK. In patients with low-to-moderate myopia, PRK produces stable and predictable results with an excellent safety profile. LASIK is also efficacious, predictable and safe, with the additional advantages of rapid vision recovery and minimal pain. LASIK has rapidly become the most widely performed refractive surgery, with high patient and surgeon satisfaction. Noncontact Holium: YAG LTK provides satisfactory correction in patients with low hyperopia. ICR offers patients with low myopia the potential advantage of removal if the vision outcome is unsatisfactory. Despite the current widespread advertising and media attention about laser refractive surgery, not all patients are good candidates for this surgery. Family physicians should be familiar with the different refractive surgeries and their potential complications.

Corneal Transplantation↗
PubMed2001

Monitoring of controlled accommodative esotropia.

PURPOSE: To ascertain an examination interval that will not increase the risk of untimely detection of decompensation of accommodative esotropia whether or not initial nonoperative treatment must be supplemented. METHODS: The records of 63 patients with controlled accommodative esotropia examined at 3- to 6-month intervals were reviewed for age at first control, the occurrence of decompensation, initial refraction and subsequent changes, and the need for increased correction of hyperopia or the addition of bifocals. RESULTS: Decompensation occurred in 11 patients, not associated with substantial refractive changes toward or away from emmetropia. No instance of decompensation occurred in the first 12 months of observation, and only 11.5% occurred within 2 years. Although 7 of these decompensated patients were among the 18 (28.6%) requiring supplemental nonoperative treatment, their mean initial hyperopia and annual refractive change did not differ significantly from the 11 patients who did not decompensate. Eight (18.6%) of 43 patients who were first controlled earlier than age 48 months later decompensated; 3 (15.0%) of 20 patients with later onset reached this outcome. CONCLUSIONS: Monitoring controlled accommodative esotropia at intervals of 9 to 12 months is adequate for most patients, at least over the first 2 years, other than those requiring treatment for associated conditions such as amblyopia. Refractive error changes and the need for supplemental treatment after initial control are not prominently associated with decompensation. Age at onset of accommodative esotropia earlier or later than 48 months did not influence rapidity of decompensation.

Accommodation, Ocular↗
PubMed2002

Refractive error in children in a rural population in India.

PURPOSE: To assess the prevalence of refractive error and related visual impairment in school-aged children in the rural population of the Mahabubnagar district in the southern Indian state of Andhra Pradesh. METHODS: Random selection of village-based clusters was used to identify a sample of children 7 to 15 years of age. From April 2000 through February 2001, children in the 25 selected clusters were enumerated in a door-to-door survey and examined at a rural eye center in the district. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. Myopia was defined as spherical equivalent refractive error of at least -0.50 D and hyperopia as +2.00 D or more. Children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance in seven clusters. RESULTS: A total of 4414 children from 4876 households was enumerated, and 4074 (92.3%) were examined. The prevalence of uncorrected, baseline (presenting), and best corrected visual acuity of 20/40 or worse in the better eye was 2.7%, 2.6%, and 0.78%, respectively. Refractive error was the cause in 61% of eyes with vision impairment, amblyopia in 12%, other causes in 15%, and unexplained causes in the remaining 13%. A gradual shift toward less-positive values of refractive error occurred with increasing age in both boys and girls. Myopia in one or both eyes was present in 4.1% of the children. Myopia risk was associated with female gender and having a father with a higher level of schooling. Higher risk of myopia in children of older age was of borderline statistical significance (P = 0.069). Hyperopia in at least one eye was present in 0.8% of children, with no significant predictors. CONCLUSIONS: Refractive error was the main cause of visual impairment in children aged between 7 and 15 years in rural India. There was a benefit of spectacles in 70% of those who had visual acuity of 20/40 or worse in the better eye at baseline examination. Because visual impairment can have a significant impact on a child's life in terms of education and development, it is important that effective strategies be developed to eliminate this easily treated cause of visual impairment.

Adolescent↗
PubMed2002

20 unusual presentations of accommodative esotropia.

PURPOSE: This paper will discuss several unusual presentations of accommodative esotropia. METHODS: A total of 20 patients with unusual case histories who presented with accommodative esotropia were studied retrospectively. These patients were separated into 3 categories. The first contained children who had their onset of accommodative esotropia after a traumatic event such as head trauma or ocular trauma. The second involved infants between 3 and 5 months of age who presented with accommodative esotropia. The third showed the onset of accommodative esotropia associated with diabetic ketoacidosis. (There were no other metabolic disorders associated with accommodative esotropia.) RESULTS: All patients resolved their esotropia with glasses initially but 2 did require surgery several years after the onset of the esotropia. CONCLUSIONS: Children under 5 months of age with intermittent esotropia and/or significant amounts of hyperopia should have the diagnosis of accommodative esotropia considered as the etiology of their esotropia. Children with the onset of esotropia associated with trauma who have significant amounts of hyperopia should also have accommodative esotropia considered as an etiology of their crossing.

Accommodation, Ocular↗
PubMed2002

[Epidemiologic study of refractive errors in schoolchildren in socioeconomically deprived regions in Tunisia].

PURPOSE: This study's purpose was to estimate the prevalence of common refractive errors in schoolchildren in low socioeconomic regions in Tunisia and to assess their effect on school performance. MATERIAL AND METHODS: This was a cross-sectional study done from November 1999 to January 2000 within the context of health care screening campaigns carried out by volunteer ophthalmologists and opticians in low-end socioeconomic regions in Tunisia. The concerned population was schoolchildren living in the cities of Tunis and Tabarka (North), Kerkena (Center), and Tozeur (South). We examined a total of 708 children with a mean age of 11.9 +/-3.21 years (from 6 to 20 years) and a sex ratio of 0.84. A cycloplegic refraction examination was performed on all the children. Statistical analyses with the chi squared test and the Fisher exact test allowed us to calculate the prevalence of the refractive errors totally and separately as well as the distribution according to age, sex, and region. We also searched for a possible relation between refractive errors and academic failure. RESULTS: Among the 708 children, 57.2% [CI(95)=53.4-60] had refractive errors, of which 31.6% [CI(95)=28.2-35.2] were hyperopic, whereas 9.1% [CI(95)=7.1-11.5] were myopic. Astigmatism was found in 16.4% [CI(95)=13.7-19.3]. The prevalence of myopia was significantly higher after the age of fourteen. It increased significantly with age (P=0.0003). The prevalence of hyperopia was significantly higher between the ages of 8 and 11 (P=0.0004). Hyperopic astigmatism was significantly more frequent between 6 and 9 years of age (P=0.001). There was no significant difference regarding sex. However, the distribution of the refractive errors by region showed a significantly high level of myopia in Tunis, Kerkena, and Tozeur. This difference disappeared with increasing age. The study of the effect of these refractive errors on school performance of these children from poor areas showed a significant association between all types of refractive errors and academic failure, with an odds ratio of 2.13 for all types of refractive errors, 2.69 for hyperopia, 2.87 for myopia, and 2.73 for astigmatism. CONCLUSION: This study showed the prevalence of refractive errors in a poor population of schoolchildren and emphasized the importance of such examinations. The ability of a child to participate in the educational experience is at least partially dependent on good vision.

Adolescent↗
PubMed1992

Analysis of refractive status of Hong Kong Chinese infants.

Recently developed methods of quantifying changing dioptric power are applied to the refractive status of Hong Kong Chinese infants from about 10 to about 40 weeks of age. The analysis confirms that hyperopia decreases during the period and that with-the-rule astigmatism predominates. Change, however, is not constant over the period. The rate of decrease of hyperopia slows down and the refractive status becomes more spherical. The mean refractive status is calculated at 10, 20, 30 and 40 weeks. The spread of refractive status is represented by variance-covariance matrices calculated for each group and 95% confidence ellipsoids on the mean are constructed. The variance-covariance exhibits little change over the period. The right and left eyes show similar behaviour.

Aging↗
PubMedDate not supplied

[Refractive surgery - a review.].

Refractive errors, such as myopia, hyperopia and astigmatism, are very common all over the world. Refractive surgery started in the latter half of the twentieth century and over the last one or two decades refractive surgery with lasers has become popular. Refractive surgery for myopia flattens the cornea of the eye and decreases its refractive power. Surgery for hyperopia on the other hand increases the curvature of the cornea and increases the refractive power. Today this is most frequently done with a lasik procedure where a flap is lifted of the cornea and the laser surgery performed underneath the flap.

English Abstract↗