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PubMed1987

Refractive errors in children.

Optical correction of refractive errors in infants and young children is indicated when the refractive errors are sufficiently large to cause unilateral or bilateral amblyopia, if they are impairing the child's ability to function normally, or if the child has accommodative strabismus. Screening for refractive errors is important and should be performed as part of the annual physical examination in all verbal children. Screening for significant refractive errors in preverbal children is more difficult; however, the red reflex test of Bruckner is useful for the detection of anisometropic refractive errors. The photorefraction test, which is an adaptation of Bruckner's red reflex test, may prove to be a useful screening device for detecting bilateral as well as unilateral refractive errors. Objective testing as well as subjective testing enables ophthalmologists to prescribe proper optical correction for refractive errors for infants and children of any age.

Adolescent↗
PubMedDate not supplied

Early refractive development in humans.

Over recent years much interest has been directed toward understanding the process by which refractive errors develop, how this is controlled and the effect of refractive errors on subsequent visual status. There are obvious difficulties in studying such mechanisms in human subjects and for this reason many studies have employed animal models. The present paper compiles the evidence available from human subjects, examining the significance of different aspects of refractive status, normal and abnormal patterns of development and their significance in the development of normal binocular function.

Adolescent↗
PubMedDate not supplied

Refractive emergency.

Explore the source record for details and available documents.

Accommodation, Ocular↗
PubMedDate not supplied

Spasm of the near reflex: a spectrum of anomalies.

Spasm of the near reflex has been characterized as the variable appearance of pseudomyopia, convergent strabismus and miosis. These characteristics may appear together or separately. In addition, abnormalities of accommodation may appear not only as pseudomyopia, but may also be manifest in cases with significant hypermetropia in which the patient is unable to relax accommodation even when plus lenses are used. The intent of this review is to identify the various clinical presentations of anomalies of the entire near reflex as well as the component parts. The relationship to functional and organic disorders are discussed as well as the related neuroanatomy. We suggest that one may more readily understand the clinical manifestations as a spectrum of anomalies of the near reflex rather than a multitude of disconnected entities.

Accommodation, Ocular↗
PubMed2003

The influence of the Stiles-Crawford peak location on visual performance.

We investigated the influence of the Stiles-Crawford peak location on visual acuity, contrast sensitivity and phase transfer with 6 mm diameter pupils in two subjects. Apodising filters were used to move the peak. One subject (SM) had her natural peak 0.9 mm below pupil centre, and visual performance was measured for both this peak position and when the peak was moved to the same distance above pupil centre. The other subject (DAA) had a more centred peak and visual performance was measured for this peak position and when the peak was moved both 2.3 mm temporally and 2.6 mm nasally. Measurements of contrast sensitivity and phase transfer were compared with predictions based on aberration measurements. The peak position had definite influence on performance, but this was mainly noticeable when subjects were defocused e.g. SM's visual acuity was reduced by 0.13 log units under the peak-shifted condition at -2D (hypermetropic) defocus.

Adult↗
PubMed2003

Further evidence that chick eyes use the sign of blur in spectacle lens compensation.

Young animals compensate for defocus imposed by positive or negative spectacle lenses by adjusting the elongation rate of their vitreous chambers, thus matching the length of the eye with the focal length of the eye's optics combined with the spectacle lenses. The ability to compensate for either negative or positive lenses could rely on the ability to distinguish between myopic and hyperopic blur, or it could rely on the fact that positive lenses would bring nearby objects into focus, thereby reducing the amount of blur, whereas negative lenses would not. This study asks whether eyes emmetropize using the magnitude of blur or the sign of blur as a directional cue. We fitted chick eyes with positive lenses while imposing a substantial amount of blur, either (a) by having them wear lenses only when restrained in the center of a cylinder, the walls of which were beyond their far-point or (b) by having them wear mild diffusers over positive lenses. We found good refractive compensation in both situations in a large number of birds. Furthermore, we found that mild diffusers worn on top of positive lenses differentially affected the two ocular components of refractive compensation: there was less choroidal thickening, but more inhibition of ocular elongation, compared to wearing positive lenses alone. These findings argue both that the eye can discern the sign of the blur and that choroidal and ocular-elongation components of the refractive compensation do not respond identically to visual inputs.

Accommodation, Ocular↗
PubMed2000

Topography-driven photorefractive keratectomy: results of corneal interactive programmed topographic ablation software.

OBJECTIVE: This study evaluated the efficacy, predictability, stability, and safety of a software program (Corneal Interactive Programmed Topographic Ablation (CIPTA) LIGI, Taranto, Italy) which, by transferring programmed ablation from the corneal topography to a flying-spot excimer laser, provides customized laser ablation. DESIGN: Noncomparative consecutive case series. PARTICIPANTS: Forty-two eyes of 34 subjects with a mean age of 33.9 (range, 20-54) had CIPTA at the Cattedra di Ottica Fisiopatologica of Bari (Italy). Twenty-eight eyes were treated for hyperopic astigmatism and 14 for myopic astigmatism. All the subjects had irregular astigmatism. OPERATION: Topography was acquired by a corneal topography mapping system (Orbscan, Orbtek, Inc., Salt Lake City, UT). These data were processed to obtain a customized altimetric ablation profile, which was transferred to a flying-spot laser (Laserscan 2000, Lasersight, Orlando, FL). MAIN OUTCOME MEASURES: Data on uncorrected (UCVA) and best-corrected visual acuity (BCVA), predictability, and stability of refraction and any complications were analyzed. RESULTS: Mean follow-up was 13.2 months. At the last postoperative examination, 26 eyes (92.8%) in the hyperopic group and 12 eyes (85.7%) in the myopic group had an UCVA superior to 20/40. Twelve hyperopic eyes (42.8%) and five myopic eyes (35.7%) had a UCVA of 20/20. All patients fell between 1 diopter of attempted correction in the spherical equivalent. Only 1 (2.4%) of the 42 eyes, belonging to the hyperopic group, lost 1 Snellen line of BCVA. We did not observe any decentration and/or haze after photorefractive keratectomy treatment or any irregularity in the flap-stroma interface in the three laser in situ keratomileusis operations performed in this study. CONCLUSIONS: The combination of topographic data with computer-controlled flying-spot excimer laser ablation is a suitable solution for correcting irregular astigmatism due to different causes.

Adult↗
PubMed2003

Five-year refractive changes in an older population: the Blue Mountains Eye Study.

PURPOSE: To examine 5-year changes in refractive error and astigmatism in an older population. DESIGN: Population-based cohort study. PARTICIPANTS: The Blue Mountains Eye Study examined 3654 residents aged 49 years or older from 1992 to 1994. After excluding 543 persons who died since baseline, 2335 (75.1%) attended 5-year examinations from 1997 to 1999. METHODS: Both examinations included a detailed eye assessment, with subjective refraction performed according to a modified Early Treatment of Diabetic Retinopathy Study protocol. MAIN OUTCOME MEASURES: Spherical equivalent (sum of sphere + cylinder) was used as the measure of refractive error. Only phakic eyes with best-corrected visual acuity >20/40 were included (n = 3701). RESULTS: Similar changes in refractive error were observed for the two eyes. Symmetric changes were found in 72% of participants when the difference between eyes was within 0.5 diopters (D) and in 91% when the difference was within 1.0 D. The 5-year change in spherical power was in a hyperopic direction for younger age groups and in a myopic direction for older subjects, P < 0.0001. The gender-adjusted mean change in refractive error in right eyes of persons aged 49 to 54, 55 to 64, 65 to 74, and 75 years or older at baseline was +0.41 D, +0.30 D, +0.05 D, and -0.22D, respectively. Refractive change was strongly related to baseline nuclear cataract severity; grades 4 to 5 were associated with a myopic shift (-0.33 D, P < 0.0001). Education level and age of onset of myopia, but not gender or diabetes, also predicted refractive change. The mean age-adjusted change in refraction was +0.14 D for hyperopic eyes, +0.32 D for emmetropic eyes, and +0.15 D for myopic eyes. The mean change in cylinder power over the 5-year period was small, irrespective of baseline refraction. The axis of astigmatism remained stable in most cases (64%), whereas 12% changed to "against the rule" and 11% to "with the rule." CONCLUSIONS: This report has documented refractive error changes in an older population and confirmed reported trends of a hyperopic shift before age 65 years and a myopic shift thereafter associated with the development of nuclear cataract.

Age Distribution↗
PubMed2003

Comparison of flap thickness reproducibility using microkeratomes with a second motor for advancement.

PURPOSE: To compare flap thickness and reproducibility of four different types of microkeratomes during LASIK. DESIGN: Retrospective, nonrandomized, comparative case series. PARTICIPANTS: Four hundred ninety consecutive eyes underwent LASIK and were evaluated by measuring the central flap thickness by subtractive pachymetry. METHODS: All flaps were created using the Bausch & Lomb (Miami, FL) Hansatome 180 head, the Alcon (Fort Worth, TX) Summit Krumeich Barraquer Microkeratome 160 head, the Moria (Antony, France) Carriazo Barraquer (CB) 130 head, or the Moria M2 110 head. RESULTS: The flap thickness measurements differed according to the microkeratome used and were 131+/-28 microm in 41 eyes (8.4%) with the Bausch & Lomb Hansatome 180 head, 162+/-21 microm in 127 eyes (25.9%) with the Alcon Summit Krumeich Barraquer Microkeratome (SKBM) 160 head, 157+/-40 microm in 65 eyes (13.3%) with the Moria CB 130 head, and 134+/-23 microm in 257 eyes (52.4%) with the Moria M2 110 head. The central flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with the Moria CB (P< 0.0005). There is no correlation between flap thickness reproducibility and age, corneal thickness, or corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender (P<0.02). CONCLUSIONS: Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2 microkeratomes, which both use a second motor for advancement. The greatest variability, noted with the Moria CB, was likely due to the manual translation feature and places further importance on the safety of the second motor and automation when performing LASIK.

Adult↗
PubMed1980

Normal endothelial cell count range.

It was the purpose of this study to determine whether age could be used to predict central endothelial cell count in preoperative cataract patients aged 40 to 90. Three separate series of cell counts on a total of almost 3,000 eyes were performed and analyzed regarding age relationship. Although statistically endothelial cell count appears to decrease with age, the decrease is so small that a large range of cell counts was noted for each age. The results of this study indicate that age is not useful in estimating endothelial cell count in this population.

Adult↗
PubMed1981

Clinical results of keratophakia and keratomileusis.

Thirteen keratophakia patients were followed for 13 to 35 months. Eighteen cases of hyperopic keratomileusis or hyperopic keratomileusis using preserved corneal tissue were followed for 2 to 30 months. All 13 patients who underwent keratophakia achieved 20/50 or better acuity. All seven patients having hyperopic keratomileusis achieved 20/60 or better acuity. Eight of the 11 patients who had hyperopic keratomileusis using donor corneal tissue achieved 20/60 or better acuity. The preservation of lenticules after lathing did not adversely affect the correlation between predicted and observed dioptric corrections. There was a statistically significant correlation between predicted and observed dioptric corrections. There was a statistically significant correlation between predicted and observed dioptric correction measured at the corneal surface when the lenticule was lathed from fresh tissue (hyperopic keratomileusis) or from relatively fresh tissue (keratophakia). However, we found that there was poor correlation between the predicted and observed corrections when the lenticule was lathed from donor tissue that had been cryopreserved for long periods of time (hyperopic keratomileusis with preserved corneal tissue).

Aphakia↗
PubMed1983

Accommodative esotropia long range follow-up.

Thirty-nine adult patients treated for typical (refractive) accommodative esotropia in childhood continue to have problems because they have not outgrown their hypermetropia, and the majority have not developed stable binocular vision. Their hypermetropia became maximal (median 5.7 diopters) by age 6, decreased in adolescence, and then stabilized (median 4 diopters). Thirty-eight of the 39 adults wear correcting lenses full-time. Nearly all depend on relaxed accommodation to maintain alignment when they remove their glasses. Ten patients, all of whom received treatment before a constant esotropia developed are essentially orthophoric with glasses and have normal binocular vision. The remainder have small-angle deviations with glasses, 14 with varying degrees of amblyopia and peripheral fusion and 15 with anomalous correspondence and suppression. As adults, only one patient with normal binocular function has required surgery whereas 13 of the patients lacking normal fusion have had surgery for increasing esotropia, postoperative exotropia, or consecutive exotropia.

Accommodation, Ocular↗