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At least 1,045 records · Page 58Linked to original sources
PubMed2005

Retrospective analysis of refractive errors in children with vision impairment.

PURPOSE: Emmetropization is the reduction in neonatal refractive errors that occurs after birth. Ocular disease may affect this process. We aimed to determine the relative frequency of ocular conditions causing vision impairment in the pediatric population and characterize the refractive anomalies present. We also compared the causes of vision impairment in children today to those between 1974 and 1981. METHODS: Causes of vision impairment and refractive data of 872 children attending a pediatric low-vision clinic from 1985 to 2002 were retrospectively collated. As a result of associated impairments, refractive data were not available for 59 children. An analysis was made of the causes of vision impairment, the distribution of refractive errors in children with vision impairment, and the average type of refractive error for the most commonly seen conditions. RESULTS: We found that cortical or cerebral vision impairment (CVI) was the most common condition causing vision impairment, accounting for 27.6% of cases. This was followed by albinism (10.6%), retinopathy of prematurity (ROP; 7.0%), optic atrophy (6.2%), and optic nerve hypoplasia (5.3%). Vision impairment was associated with ametropia; fewer than 25% of the children had refractive errors < or = +/-1 D. The refractive error frequency plots (for 0 to 2-, 6 to 8-, and 12 to 14-year age bands) had a Gaussian distribution indicating that the emmetropization process was abnormal. The mean spherical equivalent refractive error of the children (n = 813) was +0.78 +/- 6.00 D with 0.94 +/- 1.24 D of astigmatism and 0.92 +/- 2.15 D of anisometropia. Most conditions causing vision impairment such as albinism were associated with low amounts of hyperopia. Moderate myopia was observed in children with ROP. CONCLUSIONS: The relative frequency of ocular conditions causing vision impairment in children has changed since the 1970s. Children with vision impairment often have an associated ametropia suggesting that the emmetropization system is also impaired.

Adolescent↗
PubMed1991

Combined microwave heating and surface cooling of the cornea.

We investigated a nonsurgical means of reshaping the cornea to correct hyperopia, keratoconus, or myopia. The object was to heat the central stroma of the cornea to the shrinkage temperature of collagen, 55-58 degrees C. The heating device was an open-ended, coaxial, near-field applicator driven at 2450 MHz; it incorporates cooling of the cornea surface by flow of saline. We investigated the system theoretically by computing the 2-D, axisymmetric temperature distribution with the finite element method. We investigated the system experimentally by heating excised steer corneas. Histology showed the system could shrink the stroma to a depth of 0.6 mm while sparing the epithelium in 75% of cases; the diameter of shrinkage was 1.3 mm. Theory predicted a significantly deeper and narrower region of shrinkage than was observed.

Animals↗
PubMed2004

Refractive status and the 5-year incidence of age-related maculopathy: the Blue Mountains Eye Study.

This study aimed to assess the longitudinal association between refraction and 5-year incident age-related maculopathy (ARM) in the Blue Mountains Eye Study population. The dataset included 3654 participants aged 49+ (82.4% of eligible) examined at baseline (1992-1994), and 2335 (75.1% of survivors) examined after 5 years. Retinal photograph grading followed the International ARM Classification. Incident ARM was assessed using a side-by-side comparison. Refraction was performed using autorefraction with subjective refinement. Spherical equivalent was calculated from spherical plus half the cylindrical power. After adjusting for age, sex and smoking, no association was found between baseline spherical equivalent and 5-year incident late or early ARM. Hyperopic right eyes had slightly higher incident rates for late (0.8%) and early (6.3%) ARM, compared with myopic (0.4% and 4.1%, respectively) or emmetropic (0.5% and 5.0%, respectively) right eyes. After multivariable adjustment, this study found no significant association between hyperopia and the 5-year incidence of late or early ARM. Left eyes or the combined data from both eyes had similar findings.

Female↗
PubMed2005

Refractive surgery and strabismus.

This review discusses the potential for strabismic complications after refractive surgery for hyperopia, myopia, anisomyopia, astigmatism and monovision, and how to avoid these complications. Guidelines are given for assessing patients with strabismus seeking refractive surgery. Screening tests are suggested that lead to stratification of refractive surgery patients into different risk groups each warranting a different intensity of evaluation.

Adult↗
PubMed2005

Clinical manifestations of a unique X-linked retinal disorder in a large New Zealand family with a novel mutation in CACNA1F, the gene responsible for CSNB2.

PURPOSE: To describe the phenotype in a New Zealand family with an unusual severe X-linked retinal disorder with a novel I745T mutation in CACNA1F, the gene responsible for incomplete congenital stationary night blindness (CSNB2). METHODS: Members of the family tree were invited for clinical, psychophysical and electrodiagnostic evaluation. RESULTS: Male family members had severe non-progressive visual impairment, abnormal colour vision, congenital nystagmus, hyperopia and normal fundi. Some were intellectually disabled. Female family members had congenital nystagmus and decreased visual acuity frequently associated with high myopia. Electroretinograms (ERG) identified reduced rod and cone responses with negative waveform in male and female family members, with atypical features for CSNB2. CONCLUSIONS: Although there were similarities to CSNB2, distinctive features in male family members included severity of phenotype, and association of intellectual disability. Moreover, all female heterozygotes had clinical and ERG abnormalities. CACNA1F encodes the Ca(v)1.4 alpha1 subunit of a voltage-gated calcium channel, which may mediate neurotransmitter release from photoreceptors. Molecular analyses, reported separately, identified a novel I745T CACNA1F mutation that was associated in vitro with major alterations in gating and kinetics of the Ca(v)1.4 channel. It is speculated that the unique phenotype described in this family may reflect similarly altered function of Ca(v)1.4 channel activity in vivo.

Adolescent↗
PubMedDate not supplied

Is there a hyperopic shift in myopic eyes during the presbyopic years?

BACKGROUND: Studies of age-related changes in myopia during the presbyopic years have produced contradictory results. Some studies have shown that myopic eyes undergo a hyperopic shift after the age of 40 or 45 years, whereas others have provided evidence for a myopic shift. In this paper, we report the results of both a cross-sectional study and a retrospective longitudinal study of age-related changes in refraction during the presbyopic years. METHODS: In the cross-sectional study, refractive error data were tabulated for the right eyes of 559 patients over the age of 45 years, who had been examined during a 17-month period in an established optometric practice. In the longitudinal study, we tabulated refractive error data on 100 myopes, 100 hyperopes and 100 emmetropes, who had been examined for periods varying from 10 to 26 years after age 40, all of whom had 6/6 visual acuity at all examinations. RESULTS: In the cross-sectional study, the prevalence of myopia during the later presbyopic years was found to be greater when eyes with all visual acuities were included than when only eyes with acuity of 6/6 or better were considered. In the longitudinal study, it was found that almost all hyperopic and emmetropic eyes showed an age-related hyperopic shift; but only a small proportion of myopic eyes shifted toward hyperopia, with others remaining relatively stable and still others increasing in myopia. DISCUSSION AND CONCLUSIONS: We suggest that when healthy myopic, hyperopic, or emmetropic eyes shift in the hyperopic direction, it is because of an age-related decrease in the gradient index of the lens; but when healthy myopic eyes shift in the myopic direction, it is because of axial elongation that more than compensates for the decrease in the gradient index of the lens. Another possible cause of a myopic shift, even for eyes having 6/6 visual acuity, is the presence of early, sub-clinical nuclear sclerosis.

Journal Article↗
PubMed2003

Prevalence of myopia among primary school children in eastern Sydney.

BACKGROUND: Worldwide there is concern that the prevalence of myopia is increasing but the prevalence of myopia in Australian school children has not been analysed in detail. This study examines the prevalence of refractive errors in a large unselected population of primary school children in the eastern suburbs of Sydney. METHODS: Children visiting the Vision Education Centre at the School of Optometry and Vision Science, University of New South Wales, on a school excursion during the first half of the 1990s were refracted by non-cycloplegic retinoscopy. Spherical equivalents were computed and analysis of variance carried out. RESULTS: There were 1,459 boys and 1,076 girls in the study, a total of 2,535 children of whom approximately 40 per cent were born overseas or were first generation Australians. Overall, there was no significant difference in refractive error between girls and boys, although there were age/gender interactions with older girls exhibiting more hyperopia than boys. The refractive error ranged from -0.25 to +1.25 D spherical equivalent in 87.3 per cent of children. Mean spherical equivalent for the group was +0.50 +/- 0.82 D. There was a significant shift (p < 0.001) towards increasing myopia with age. The prevalence of myopia greater than -0.50 D rose from 1.0 per cent of four-year-olds to 8.3 per cent of 12-year-olds. CONCLUSIONS: The prevalence of myopia found in a large multi-ethnic group of non-clinical primary school children in eastern Sydney is lower than expected from other studies in the USA and Asia. Compared with Australian data from the 1970s and 1980s, only a weak increase in the prevalence of myopia is revealed.

Age Distribution↗
PubMed1994

Refraction referral criteria for Hong Kong Chinese preschool children.

The major types of ametropia and visual problems for Hong Kong Chinese and Caucasian children are different. Consequently, the referral criteria developed for Caucasian children may not be applicable to Hong Kong children. Results of our study suggested that the referral criteria for Hong Kong children should be set as hyperopia of > or = +2.0 D, myopia of > or = 1.0 D, astigmatism of > or = 1.0 D and anisometropia of > or = 1.25 D. Sensitivity using only these criteria for abnormal refraction in identifying children with amblyopia, esotropia, exotropia and subnormal vision (< 6/12) was respectively 100%, 84.6%, 45.2% and 95.7%. The overall sensitivity for the identification of visual problems was 86.1% and the overall specificity was 76%. If a cover test or a Hirschberg test was introduced into the screening battery so that all the strabismic cases were identified. the overall sensitivity would increase to 98.6%.

Amblyopia↗
PubMed2004

Stimulating human accommodation without changes in focus.

PURPOSE: Inspired by the finding in chickens that preferential stimulation of the ON retinal system suppresses myopia induced by negative spectacle lens wear and that stimulation of the OFF system suppresses the hyperopia induced by positive lens wear, we sought to determine whether stimulation of the ON-OFF retinal systems could drive directional accommodation responses in humans. If emmetropisation and accommodation use similar image processing algorithms, more accommodation would be expected with OFF stimulation. METHODS: Accommodation responses were measured while viewing a computer-generated pattern designed to stimulate the ON-OFF systems. The stimulus comprised a rectangular field (12 x 9.5 cm) on a black background filled with 196 discs (diameters: 0.4-1.0 cm). These were presented on an LCD monitor in a dark room at a viewing distance of 55 cm (1.8 D). Thirteen subjects aged 21-37 years took part. The individual discs had saw-tooth shaped temporal luminance profiles with the same time period but with random phases with respect to each other, so that the mean brightness of the stimulus was constant. To eliminate accommodation responses based on other cues (i.e. proximity) a 0.5 mm artificial pupil was used to open the accommodation loop. Refraction in the vertical pupil meridian was continuously recorded with an infrared photorefractor (the PowerRefractor). To verify that computer-based stimuli presented within our experimental design were effective in driving accommodation, previously studied stimuli were also tested: changes in size (looming) and incremental low pass filtering. RESULTS: Preferential stimulation of the ON or OFF subsystems produced a convincing depth illusion in all subjects (which was psychophysically confirmed in four subjects). Although the stimulus appeared to move in depth it did not produce accommodation responses that were consistent with that, i.e. the accommodation system did not appear to fluctuate in rhythm with the temporal oscillations of the stimulus. As the target appeared to loom it induced a greater accommodation response then when it appeared to recede. The looming target produced changes in the accommodation response in nine of 13 subjects that were consistent with its perceived change in proximity (although the target did not actually move in depth). Incremental low pass filtering produced non-directional drifts of accommodation in all subjects. Combinations of the stimuli (i.e. looming and low pass filtering, ON/OFF and looming) were not more effective stimuli to accommodation. After removal of the artificial pupil (closed loop conditions), accommodation was no longer induced with any of these stimuli. CONCLUSIONS: Although the preferential ON or OFF stimulation produced a pronounced illusion of motion in depth despite constant average brightness, proximal accommodation was induced in only one subject. Therefore, the ON/OFF stimulation appeared to have only minor input into proximal accommodation. Potential inputs into reflex accommodation need to be defined in further studies.

Accommodation, Ocular↗
PubMed2005

Refractive error and ocular biometry in Jordanian adults.

The aim of this study was to establish the prevalence of refractive errors in Jordanian adults of working age, and to study the ocular biometric correlates of refractive error in this population. Refractive error and ocular biometry were measured in 1093 Jordanian adult subjects aged 17-40 years to determine the prevalence of refractive error, and explore structural correlations of ametropia. Refractive error was measured using a Grand-Seiko GR-3100K closed-view infrared autorefractor. Ocular component measurements were made using A-scan ultrasonography and autokeratometry. The prevalence of myopia [spherical equivalent refraction (SER) less than -0.50 DS] and hyperopia (SER greater than +0.50 DS) was 53.71 and 5.67% respectively; 40.62% of the sample was emmetropic (refraction between +0.50 D and -0.50 D inclusive in both principal meridians). The distribution of SER was found to show marked leptokurtosis, exhibiting a peak between plano and 1 D of myopia. Corneal radius, anterior chamber depth, crystalline lens thickness, vitreous chamber depth and axial length (AL) parameters were normally distributed in the population studied. AL to corneal curvature ratio was not normally distributed, and showed marked leptokurtosis. Linear regression analysis showed that AL correlated most closely with spherical equivalent refractive error. This study has established a database of refractive error prevalence and ocular biometric correlates of ametropia in a Middle Eastern population of working age.

Adolescent↗
PubMed1996

Screening techniques for angle-closure glaucoma in rural Taiwan.

562 residents of Jin Shan aged 40 years and above underwent examinations to compare the sensitivity and specificity of oblique flashlight, peripheral slit beam and ultrasonographic evaluation of the anterior chamber depth to gonioscopy in detecting cases of PACG. Among 5441 eligible individuals aged 40 and above, 562 (10.3%) underwent screening for PACG, of whom 17 (3.02%) were defined as cases, and 10 (1.78%) as suspects. Home visits indicated that respondents for screening were similar to the population as a whole. Only 35% of PACG cases reported symptoms consistent with acute angle closure, and only 18% were previously diagnosed. When compared to gonioscopy, only ultrasonographic measurement of AC depth provided an adequate mix of sensitivity and specificity. Ultrasonography in combination with tonometry provided a sensitivity of 88% with a specificity of 92%. Sensitivity and specificity for ultrasonography in combination with refractive status were 84% and 83% respectively. Shallower AC depth (p = 0.0001), shorter axial globe length (p = 0.001), greater than 2D of hyperopia (p < 0.001), high grades of nuclear sclerotic cataract (p < 0.0001) and an increased cup-to-disc ratio (p = 0.002) were significantly correlated with a diagnosis of PACG.

Adult↗
PubMed2006

Ophthalmological findings in children born after intracytoplasmic sperm injection.

PURPOSE: To investigate visual function and ocular morphology in children born after intracytoplasmic sperm injection (ICSI) and compare them with visual function and ocular morphology in matched children born after spontaneous conception. METHODS: A total of 137 children born after ICSI and 159 control children were examined at the age of 5 years in a blinded study. The two groups were matched for age, gender and maternal age. The children underwent a detailed ophthalmological investigation by an ophthalmologist and an orthoptist. RESULTS: A total of 90.4% of the ICSI children had a visual acuity (VA) in the better eye of >or= 0.8, compared with 93.7% of the controls (NS). No significant differences were found between ICSI children and controls with regard to hyperopia, myopia, astigmatism, heterotropia, stereoscopic vision and convergence. One child with Goldenhar syndrome and one with Marcus Gunn syndrome were observed in the ICSI group. One child in the ICSI group was treated for retinopathy of prematurity. CONCLUSION: In this limited study group, no significant differences in visual function and/or ocular morphology were found between children born after ICSI and matched control children at the age of 5 years.

Case-Control Studies↗
PubMed2006

Ophthalmological findings in a sample of Swedish children aged 4-15 years.

AIMS: To characterize ophthalmological findings in a sample of Swedish children aged 4-15 years. METHODS: A prospective cross-sectional comprehensive ophthalmological investigation was performed on a sample of 143 children (67 girls, 76 boys) aged 4-15 years. RESULTS: Visual acuity (VA) in the better eye >or=1.0 ( 0.3 logMAR). Amblyopia was found in 0.7% of subjects. A total of 68% of the children had no refractive errors. Hyperopia (>or=2.0 dioptres [D] in spherical equivalent [SE]) was found in 9% and myopia (>or=0.5 D SE) in 6% of children. Astigmatism (>or=0.75 D) was recorded in 22% and anisometropia (>or=1.0 D SE) in 3%. A total of 8% were optically corrected. Strabismus was recorded in 3.5%. Signs of visuoperceptual problems were reported in 3% of the children. CONCLUSION: This sample of Swedish children may serve as a comparison group regarding ophthalmological findings in children aged 4-15 years.

Adolescent↗
PubMed1981

Photographic screening for strabismus and high refractive errors of children aged 1-4 years.

UNLABELLED: 182 children (age 1-4 years) were photographed by health sisters at the annual screening at the children's health care center as described by Kaakinen (1979). The photographs were examined by an ophthalmologist to diagnose squint and/or refractive error cases based on the typical changes in the corneal and fundus reflexes. The cases found in this way were controlled clinically. RESULTS: 7 pathological cases were detected: 2 esotropias, 1 microesotropia, 2 hyperopias of both eyes, 2 anisocorias. False positive were 6 cases, from which 4 were false positive microstrabismus suspects and 2 cases with asymmetrical fundus reflexes, which were normal. 14 cases failed (9 (4.9%) looked to the side, and 5 (2.7%) were technical failures). For the reliability of the method, a random sample of 20 children, who had normal corneal and fundus reflexes were examined clinically. No anisometropia of over 0.5 diopters appeared among these 20 control cases, and the highest hyperopic and astigmatic errors that appeared were +1.75 diopters. All the astigmatic cases were combined with a slight myopia of -0.5- -1.0 diopters in each case. No higher myopias occurred in this group, and all these 20 children had straight eyes with the cover test at near fixation.

Child, Preschool↗
PubMed1987

Ophthalmic changes in hydrocephalus. A follow-up examination of 50 patients treated with shunts.

Fifty children shunted for hydrocephalus aged 5-17 years underwent a later ophthalmological examination. Corrected vision of 0.9 or less was found in 45 out of 93 eyes; in 21 patients this was the vision of both eyes. Corrected vision 0.3 or less was found in 7 eyes; in 3 patients this was the vision of both eyes. Hyperopia greater than or equal to +2.0 D was found in 20%, myopia greater than or equal to -0.5 D in 13% and astigmatism greater than or equal to 1.0 D in 25.5% of 98 eyes. Clear nystagmus was present in 18% of patients. Heterophoria was found in 20% and manifest horizontal strabismus in 33%, but no paretic squint. The optic disc was considered normal in 36 out of 100 eyes on ophthalmoscopy and in 35 out of 78 eyes on colour photography. Retinal nerve fibre layer photographs showed normal nerve fibres in 49 out of 71 eyes. The Friedmann field was in the normal range in 33 out of 53 eyes, and the Goldmann field was normal in 37 out of 44 eyes. Right homonymous hemianopia was discovered in 2 patients. The Harrington-Flocks field was normal in 17 out of 24 eyes, and 1 patient had left homonymous hemianopia. The HRR test showed a red-green disturbance in 22 out of 71 eyes. The Farnsworth panel D-15 desaturated test was entirely normal in only 4 out of 65 eyes, but the errors were only slight in 48 cases.

Adolescent↗
PubMed1988

Myopia in Melanesian school children in Vanuatu.

Visual acuity, refraction, and the components of refraction were measured in 788 Melanesian children in the South Pacific island nation of Vanuatu. Of the 788 children, 97.2% were found to have uncorrected visual acuity of 6/6, 96.8% were found to have a spherical equivalent refraction between -0.25 and +1.00 D, 2.9% were found to have myopia of 0.50 or more, 0.25% were found to have hyperopia of 1.25 D or more, and 0.25% were found to have refractive astigmatism of 1.25 D or more. The low prevalence of ametropia may be considered to be due mainly to genetic factors; however, the possibility of environmental factors cannot be ruled out.

Child↗
PubMed1988

Instant photographic refractometry in children.

A simple photographic method for detection and measurement of refractive errors in children, using a specially designed camera and electronic flash unit and 'instant' (Polaroid) film, was tested on 64 children, aged 3 to 8 years, and compared with the results from retinoscopy. The refractive errors ranged from -6.5 to +6.5 D. A light reflex in the pupil was observed on the photos of all children with hyperopia greater than = 0.5 and myopia greater than = 2.0 D. A curvilinear relationship was observed (in the range -2 to -4 and +0.5 to +3 D) between the width of the light reflex in the pupil, easily measured on the photos and the degree of refractive error, determined by retinoscopy. The degree of ametropia could be estimated with reasonable accuracy (+/- 0.5 D) in the interval from -2 to -4 D and +0.5 to +3 D. The method can demonstrate the type and, to a limited extent, also the degree of refraction anomaly and may be of value in screening for refractive errors in children.

Child↗
PubMed1991

Refractive errors and axial length among Alaskan Eskimos.

An epidemiological study of the prevalence of refractive errors was made of the Eskimo population of the Norton Sound and Bering Straits region of Alaska. It was possible to determine the subjective refraction in 83.7% of 1673 persons examined: 44.9% were emmetropic, 44.7% myopic and 10.4% hyperopic. Myopia was found more often in women (48.3%) than in men (41.3%), while emmetropia was found more often in men (49.3%) than in women (40.3%). Nine,four percent of the men were hyperopic and 11.4% of the women. The prevalence of myopia increased with age, with a maximum of 67.2% in the age group between 30 and 40 years. Subsequently, the number of myopes decreased rapidly. Little hyperopia was seen before the age of 50 years, it then increased rapidly, up to 71.5% for persons above the age of 80 years. Emmetropia, on the other hand, decreased with age. Ultrasound examination showed that an increasing axial length was associated with more myopia.

Adolescent↗