Results of small incision extracapsular cataract surgery using the anterior chamber maintainer without viscoelastic.
AIMS: To assess the efficacy of extracapsular cataract surgery using the anterior chamber maintainer (ACM) without the use of viscoelastic. To compare the effects of this surgical technique on non-diabetic and diabetic patients. METHODS: A prospective single armed clinical trial of 46 eyes in 46 patients undergoing cataract surgery using the ACM without viscoelastic. Patients were assessed preoperatively and at 3 weeks, 3 months, and 12 months postoperatively. The main outcome variables included visual acuity, surgically induced astigmatic change (SIAC), changes in endothelial cell density (ECD), and morphology affecting the central and superior regions of the cornea. RESULTS: Postoperatively, 56% and 70% of patients had unaided visual acuities of 6/12 or better at 3 weeks and 3 months respectively. Even after excluding those patients with pre-existing maculopathy (including diabetic maculopathy), there remains a significant difference between the non-diabetic and diabetic groups in terms of the proportion of patients attaining an unaided visual acuity of 6/12 or better at both 3 weeks (p = 0.003) and 3 months (p = 0.001). Three months postoperatively, the SIAC based upon the keratometric and refractive data was 1.1 dioptres (D) and 1.3 D respectively. There was no statistically significant difference in the SIAC when the non-diabetic and diabetic groups were compared. The mean central and superior endothelial cell losses at 3 months postoperatively were 16% and 22% respectively and at 12 months postoperatively were 20% and 25% respectively. The diabetic group demonstrated greater endothelial cell losses and a more marked and protracted deviation of endothelial cell morphology from normality when compared with the non-diabetic group; however, the differences did not reach statistical significance. CONCLUSIONS: The efficacy of small incision cataract surgery using the ACM in terms of visual outcome and induced astigmatism is comparable with the results obtained using other techniques that utilise a similar size of incision. However, in view of the magnitude and range of the endothelial cell losses associated with this technique the concurrent use of viscoelastic is suggested. There does not appear to be a statistically or clinically significant difference between non-diabetic and diabetic patients in terms of the magnitude of the endothelial cell losses or in the wound healing response in the 12 months after cataract surgery using the ACM. (+info)
Tonic accommodation, age, and refractive error in children.
PURPOSE: An association between tonic accommodation, the resting accommodative position of the eye in the absence of a visually compelling stimulus, and refractive error has been reported in adults and children. In general, myopes have the lowest (or least myopic) levels of tonic accommodation. The purpose in assessing tonic accommodation was to evaluate it as a predictor of onset of myopia. METHODS: Tonic accommodation was measured in children enrolled in the Orinda Longitudinal Study of Myopia using an infrared autorefractor (model R-1; Canon, Lake Success, NY) while children viewed an empty lit field or a dark field with a fixation spot projected in Maxwellian view. Children aged 6 to 15 years were measured from 1991 through 1994 (n = 714, 766, 771, and 790 during the 4 years, successively). Autorefraction provided refractive error and tonic accommodation data, and videophakometry measured crystalline lens curvatures. RESULTS: Comparison of the two methods for measuring tonic accommodation shows a significant effect of age across all years of testing, with the lit empty-field test condition yielding higher levels of tonic accommodation compared with the dark-field test condition in children aged 6 through 11 years. For data collected in 1994, mean (+/-SD) tonic accommodation values for the lit empty-field condition were significantly lower in myopes, intermediate in emmetropes, and highest in hyperopes (1.02 +/- 1.18 D, 1.92 +/- 1.59 D, and 2.25 +/- 1.78 D, respectively; Kruskal-Wallis test, P < 0.001; between-group testing shows each group is different from the other two). Age, refractive error, and Gullstrand lens power were significant terms in a multiple regression model of tonic accommodation (R2 = 0.18 for 1994 data). Lower levels of tonic accommodation for children entering the study in the first or third grades were not associated with an increased risk of the onset of myopia, whether measured in the lit empty-field test condition (relative risk = 0.90; 95% confidence interval = 0.75, 1.08), or the dark-field test condition (relative risk = 0.83; 95% confidence interval = 0.60, 1.14). CONCLUSIONS: This is the first study to document an association between age and tonic accommodation. The known association between tonic accommodation and refractive error was confirmed and it was shown that an ocular component, Gullstrand lens power, also contributed to the tonic accommodation level. There does not seem to be an increased risk of onset of juvenile myopia associated with tonic accommodation. (+info)
The effects of spectacle wear in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus).
We made a comprehensive study, involving observations on 45 marmosets, of the effects on ocular growth and refraction of wearing spectacles from the ages of 4-8 weeks. This period was within the period early in life when the eye grows rapidly and refraction changes from hyperopia to its adult value of modest myopia. In one series of experiments we studied the effect of lenses of powers -8, -4, +4 and +8D fitted monocularly. In another series of experiments we studied the effect of lenses of equal and opposite powers fitted binocularly, with the two eyes alternately occluded, so as to give an incentive to use both eyes, and in particular to accommodate, for at least part of each day, through the negative lens. The vitreous chamber of eyes that wore negative lenses of -4D or -8D, combined with alternate occlusion, elongated more rapidly than that of the fellow eye (negative lens eye-positive lens eye, 0.21 +/- 0.03 mm (S.E.M.), P < 0.01 and 0.25 +/- 0.06 mm, P < 0.05, respectively) and became relatively more myopic (2.8 +/- 0.26D, P < 0.01 and 2.4 +/- 0.61D, P < 0.05 respectively). Eyes that wore -4D lenses monocularly elongated more rapidly and became myopic than fellow eyes. Eyes that wore +4D or +8D lenses were less strongly affected: animals that wore +8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia (0.99 +/- 0.21D, P < 0.01), with the more hyperopic eyes also slightly shorter (0.09 +/- 0.05 mm) than their fellow eyes, but eyes wearing +4D lenses were not significantly different from their fellow eyes. Animals that wore -8D lenses monocularly (without alternate occlusion) developed a slight relative hyperopia after three weeks of lens-wear (0.85 +/- 0.26D, P < 0.05). These were the only eyes that responded in a non-compensatory direction to the optical challenge of spectacle wear, and we interpret this effect as one due to visual deprivation. After the removal of lenses, the degree of anisometropia slowly diminished in those groups of animals in which it had been induced, but in the three groups in which the largest effects had been produced by lens-wear the overall mean anisometropia (0.68 +/- 0.24D, P < 0.01) and vitreous chamber depth (VCD) discrepancy (0.09 +/- 0.03 mm, P < 0.01) were still significant at the end of the experiments, when the animals were 273 days old. The reduction of anisometropia in these groups was associated with an increase in the rate of elongation of the vitreous chamber in the eyes that had previously grown normally i.e. the less myopic eyes grew more rapidly than their fellow eyes: in the seven weeks following lens-wear these eyes became more myopic and longer than normal eyes (refraction P < 0.001; VCD P < 0.001). Control experiments showed that occlusion of one eye for 50% of the day had no effect on eye growth and refraction, and therefore that alternate occlusion itself had no effect. (+info)
Off-axis monochromatic aberrations estimated from double pass measurements in the human eye.
Off-axis monochromatic aberrations in the human eye impose limits on peripheral vision. However, the magnitude of the aberrations off-axis, and in particular coma, has not been yet completely determined. We have developed a procedure to estimate third order aberrations in the periphery of the human eye. The technique is based on recording series of double pass retinal images with unequal entrance and exit pupil diameters (Artal, Iglesias, Lopez-Gil & Green (1995b). J. Opt. Soc. Am. A, 12, 2358-2366.) which allows the odd asymmetries in the retinal image be assessed. The procedure that is described provides accurate estimates of the main off-axis aberrations: astigmatism, defocus and coma. We have measured these aberrations in four normal subjects. For a given eccentricity, the measured amount of coma and astigmatism are relatively similar among subjects, because the angular distance from the axis is the dominant factor in determining the magnitude of these aberrations. However, we found considerable variability in the values of peripheral defocus, probably due to a complicate combination of off-axis aberrations and fundus shape. The final off-axis optical performance of the eye for a given object location is determined by a particular mixture of defocus, astigmatism, coma and higher order aberrations. (+info)
Abnormal tear dynamics and symptoms of eyestrain in operators of visual display terminals.
OBJECTIVES: To clarify the relation between the prevalence of dry eye syndrome and subjective symptoms of asthenopia in visual display terminal (VDT) operators. METHOD: 722 VDT workers (242 subject workers with symptoms of asthenopia and 480 controls without such symptoms) without obvious organic ocular diseases received an ophthalmological examination consisting of refractometry and a tear function (phenol red thread) test. RESULTS: More than 30% of symptomatic workers were found to meet the criteria of dry eye, and the odds ratio compared with the controls was 4.61 (p < 0.001). This odds ratio was significantly greater than that obtained for refractive errors (2.31). CONCLUSIONS: Although this cross sectional study could not prove that dry eyes are the cause of asthenopia, the profound association of dry eyes with symptoms of asthenopia could be verified. It would be useful to carry out tear function tests in workers with symptoms of asthenopia. (+info)
Changes in refractive error over a 5-year interval in the Beaver Dam Eye Study.
PURPOSE: To examine changes in spherical equivalent over a 5-year period in persons 43 to 84 years of age. METHODS: All people 43 to 84 years of age and living in Beaver Dam, Wisconsin, in 1988 were invited for a baseline examination (1988-1990) and a 5-year follow-up examination (1993-1995). Refractions were determined according to the same protocol at both examinations. Aphakic and pseudophakic eyes were excluded as well as eyes with best corrected Snellen visual acuity of 20/40 and worse. After exclusions, refraction was obtained on 3007 right eyes and 3012 left eyes of the 3684 people participating in both examinations. RESULTS: Right and left eyes behaved similarly. Spherical equivalent became more positive in the youngest subjects and more negative in older subjects. After adjusting for other factors, the 5-year change in spherical equivalent of those 45, 55, 65, and 75 years of age was +0.15, +0.18, +0.10, and -0.07D, respectively. Severity of nuclear sclerosis was related to the amount of change. Those with mild nuclear sclerosis at baseline had a change of +0.2 D, whereas those with severe nuclear sclerosis had a change of -0.5 D. The amount of change was also related to gender, diabetes, and age at onset of myopia. It was unrelated to education and baseline spherical equivalent. CONCLUSIONS: Changes in spherical equivalent over a 5-year period were small. Before the age of 70, people became more hyperopic. After the age of 70, people became more myopic. Much of the myopic change may be related to increasing nuclear sclerosis. (+info)
Amblyopia and visual acuity in children with Down's syndrome.
BACKGROUND/AIMS: Amblyopia in people with Down's syndrome has not been well investigated. This study was designed to determine the prevalence and associated conditions of amblyopia in a group of home reared children with Down's syndrome. METHODS: All children in the study group underwent an evaluation of visual acuity. In addition, previous ophthalmological records were reviewed, and a subgroup of children was examined. For the purposes of this study, amblyopia was defined quantitatively as a difference of two Snellen acuity lines between eyes or if unilateral central steady maintained (CSM) vision and a clear fixation preference was observed. A high refractive error was defined as a spherical equivalent more than 3 dioptres and astigmatism more than 1.75 dioptres. Anisometropia was defined as a difference of at least 1.5 dioptres of sphere and/or 1.0 dioptre of cylinder between eyes. 68 children with Down's syndrome between the ages of 5 and 19 years were enrolled in the final study group. RESULTS: Amblyopia was observed in 15 (22%) of 68 patients. An additional 16 (24%) patients had bilateral vision less than 20/50. Strabismus, high refractive errors, and anisometropia were the conditions most commonly associated with decreased vision and amblyopia CONCLUSION: This study suggests that the prevalence of amblyopia is higher than previously reported. Fully 46% of these children with Down's syndrome had evidence of substantial visual deficits. These patients may be at higher risk for visual impairment and should be carefully examined for ophthalmological problems. (+info)
Refractive errors in an urban population in Southern India: the Andhra Pradesh Eye Disease Study.
PURPOSE: To assess the prevalence, distribution, and demographic associations of refractive error in an urban population in southern India. METHODS: Two thousand five hundred twenty-two subjects of all ages, representative of the Hyderabad population, were examined in the population-based Andhra Pradesh Eye Disease Study. Objective and subjective refraction was attempted on subjects >15 years of age with presenting distance and/or near visual acuity worse than 20/20 in either eye. Refraction under cycloplegia was attempted on all subjects < or =15 years of age. Spherical equivalent >0.50 D in the worse eye was considered as refractive error. Data on objective refraction under cycloplegia were analyzed for subjects < or =15 years and on subjective refraction were analyzed for subjects >15 years of age. RESULTS: Data on refractive error were available for 2,321 (92.0%) subjects. In subjects < or =15 years of age, age-gender-adjusted prevalence of myopia was 4.44% (95% confidence interval [CI], 2.14%-6.75%), which was higher in those 10 to 15 years of age (odds ratio, 2.75; 95% CI, 1.25-6.02), of hyperopia 59.37% (95% CI, 44.65%-74.09%), and of astigmatism 6.93% (95% CI, 4.90%-8.97%). In subjects >15 years of age, age-gender-adjusted prevalence of myopia was 19.39% (95% CI, 16.54%-22.24%), of hyperopia 9.83% (95% CI, 6.21%-13.45%), and of astigmatism 12.94% (95% CI, 10.80%-15.07%). With multivariate analysis, myopia was significantly higher in subjects with Lens Opacity Classification System HI nuclear cataract grade > or =3.5 (odds ratio, 9.10; 95% CI, 5.15-16.09), and in subjects with education of class 11 or higher (odds ratio, 1.80; 95% CI, 1.18-2.74); hyperopia was significantly higher in subjects > or =30 years of age compared with those 16 to 29 years of age (odds ratio, 37.26; 95% CI, 11.84-117.19), in females (odds ratio, 1.86; 95% CI, 1.33-2.61), and in subjects belonging to middle and upper socioeconomic strata (odds ratio, 2.10; 95% CI, 1.09-4.03); and astigmatism was significantly higher in subjects > or =40 years of age (odds ratio, 3.00; 95% CI, 2.23- 4.03) and in those with education of college level or higher (odds ratio, 1.73; 95% CI, 1.07-2.81). CONCLUSIONS: These population-based data on distribution and demographic associations of refractive error could enable planning of eye-care services to reduce visual impairment caused by refractive error. If these data are extrapolated to the 255 million urban population of India, among those >15 years of age an estimated 30 million people would have myopia, 15.2 million hyperopia, and 4.1 million astigmatism not concurrent with myopia or hyperopia; in addition, based on refraction under cycloplegia, 4.4 million children would have myopia and 2.5 million astigmatism not concurrent with myopia or hyperopia. (+info)