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PubMed1996

[Changes in ocular refraction after tamponade with silicone oil].

In order to study refractive changes caused by a intravitreal silicone oil injection we retrospectively analyzed 25 eyes after vitreoretinal surgery combined with silicone oil tamponade. In all cases the postoperative visual acuity was 0.1 or better. Mean difference in refraction after silicone oil tamponade in phakic eyes was +5.07 Dsph (+2.0 to +8.0 Dsph). Mean refractive change in the aphakic silicone oil filled eyes was - 6.63 Dsph (-4.0 to -9.0 Dsph). Silicone oil extraction induced a greater refractive change (myopic shift, mean -5.57 Dsph) than silicone oil injection. After silicone oil extraction from the aphakic eyes refractive changes (shift towards hypermetropia, mean +5.86 Dsph) were less manifest than after silicone oil injection. The disparity could be explained by eye elongation after cerclage performed during primary vitreoretinal surgery.

Humans↗
PubMedDate not supplied

[The AP-94 device for examination of ocular refraction].

The paper provides a brief account and technical data of an AP-94-type device (a refractometer) for examination of ocular refraction, which operates in the infrared spectrum and allows a correct diagnosis to be promptly and qualitatively established and corrective means to be chosen for the patient. The results of clinical tests of the device are given.

Humans↗
PubMed1984

Ocular refraction and visual contrast sensitivity of the rabbit, determined by the VECP.

The ocular refraction of the rabbit was determined by inserting spherical lenses of between -3 and +4D and measuring the relative VECP amplitude in response to checkboard patterns of 21 min arc. The rabbit's eye was found to be almost emmetropic (+0. 5D ). The contrast sensitivity function of the rabbit's visual system was determined by recording the VECP in response to reversed gratings of different spatial frequencies. The contrast sensitivity was found to be highest at 0.35 c/deg with an upper cut-off frequency at 3 c/deg, corresponding to a grating acuity of 10 min arc.

Animals↗
PubMed1985

Segregation analysis of ocular refraction and myopia.

Segregation analysis of ocular spherical refraction data using a unified model resulted in rejection of a Mendelian hypothesis of genetic transmission in nuclear families of both Japanese and European ancestries. Similar analyses of families which included at least 1 myope gave no evidence for the hypothesis that myopia is determined in part by a major gene. Most of the variation associated with ocular refraction, or with myopia, seems to be nongenetic in origin.

Humans↗
PubMed1988

Correlation of optical components with ocular refraction among teen-agers in Taipei.

From 2 senior-high and 2 vocational schools in Taipei, 3251 children with age 16-19 were randomly selected to study the relationship between ocular refraction and its main optical components, corneal curvature and axial length. While the corneal curvature was found to play only a minor role in the determination of ocular refraction, the measurements of axial length parallelled the degree of myopia (r = 0.74). A two-years' longitudinal study of additional 411 children from one junior-high school (age 13 through 15) further pointed to the importance of axial length in the production and progression of myopia.

Adolescent↗
PubMed1989

Ocular refraction with body orientation.

Body inversion is used experimentally to raise the intraocular pressure (IOP). Psychophysical and electrophysiological methods of assessing visual function in artificially raised IOP are generally influenced by the clarity of the retinal image. It is therefore essential to be aware of any changes in ocular refraction induced by changes in body orientation. The present study reports on the refractive changes occurring with body orientation in conditions where accommodation is freely responding, and also immobilized pharmacologically. Ocular refraction varies by less than 0.50D across all body orientations as measured by a laser optometer which provides refractive measurements independent of the perception of blur. These results indicate that pattern-dependent tests of visual function are not likely to be influenced by refractive changes on body inversion.

Adult↗
PubMed2004

Ocular refractive changes in patients receiving hyperbaric oxygen administered by oronasal mask or hood.

PURPOSE: The aim of this study was to quantify ocular refractive changes after a standard hyperbaric oxygen (HBO) treatment protocol and to characterize the time period of recovery. PATIENTS AND METHODS: Hyperbaric oxygen therapy was given for 90 min daily at a pressure of 240 kPa for 21 days. Oxygen was administered to 20 patients using an oronasal mask and to 12 patients using a hood. Follow-up examinations were carried out 2-4 days after treatment, and thereafter regularly for up to 10 weeks in both groups. Refraction was assessed automatically and by the monocular subjective refraction method. A subgroup of nine of the 20 patients to whom oxygen was administered by an oronasal mask underwent a separate eye examination, which included crystalline lens opacity measurements and LOCS III gradings. RESULTS: In the patients given oxygen by mask, there was a significant myopic shift in the mean spherical equivalent, which was largest 2-4 days after treatment. The shift was - 0.55 +/- 0.40 D in the right eye and - 0.53 +/- 0.42 D in the left eye. In the patients given oxygen by hood, the largest shift was observed after 12-16 days, and was - 1.06 +/- 0.52 D in the right eye and - 1.10 +/- 0.57 D in the left eye. The refractive changes returned to baseline 6 weeks and 10 weeks after HBO treatment, respectively. No significant changes in crystalline lens transparency were revealed. CONCLUSIONS: The myopic shift after HBO therapy recovers within 10 weeks and may be more pronounced when patients are given oxygen using a hood compared with using an oronasal mask.

Cystitis↗
PubMedDate not supplied

The change in ocular refractive components after cycloplegia in children.

PURPOSE: To study the change in ocular refractive components after cycloplegia in children. METHODS: Anterior chamber depth, lens thickness, vitreous chamber length, and ocular axial length were measured in 135 Chinese children (270 eyes) before and after cycloplegia. The corneal curvatures of 136 selected eyes were studied before and after cycloplegia with a computerized video keratoscope. RESULTS: Anterior chamber depth increased (P <.001) while both lens thickness and vitreous chamber length decreased (P <.001) significantly after cycloplegia regardless of the refractive state. However, axial length increased in hyperopic eyes (P =.027) but decreased in myopic eyes (P =.008) after cycloplegia. Mean corneal power of zones 3 mm (MD3, P =.009) and keratometer K1 readings increased (P =.025) in hyperopic eyes, while MD3 (P =.033), K1 (P =.039) and K2 (P =.003) readings decreased in myopic eyes significantly after cycloplegia. Similarly, mean corneal power of zones 5 mm and 7 mm in myopic eyes decreased dramatically (P <or=.001). In both hyperopic and myopic eyes, there was significant difference (P <.001) in the mean value of the upper and lower half of the vertical meridian, as well as the medial and lateral half of the horizontal meridian, respectively. CONCLUSIONS: Cycloplegia has a great influence on various refractive components in children. There is asymmetry of the corneal surface within the same horizontal or vertical meridian.

Accommodation, Ocular↗
PubMed1981

Nearwork and familial resemblances in ocular refraction: a population study in Newfoundland.

There is considerable epidemiological evidence that the nearwork associated with formal education can cause myopia. The potential for nearwork and education, as aspects of common familial environment, to inflate resemblances among nuclear family members in ocular refraction, was therefore investigated in a sample of 957 persons aged 5 years and over, comprising approximately 80% of the population above that age in three communities on the west coast of Newfoundland. Refraction was evaluated using standard optometric methods, nearwork measured in hours/day as reported by each subject, education measured as last completed school grade in years. The effects of nearwork and education on refraction resemblances were evaluated by adjusting refraction for age and sex, then comparing correlations or regressions among relatives before and after further linear regression adjustment of refraction for nearwork and education. Reductions in sib-sib correlations and offspring-parent regressions were achieved in this way, suggesting that these environmental factors inflate familial resemblances in refraction. Patterns of resemblances among relatives after adjustment suggest that the effects of nearwork and education on refraction resemblances were not completely removed by the linear regression adjustment used.

Adolescent↗
PubMed2005

Support for polygenic influences on ocular refractive error.

PURPOSE: Refractive errors, myopia, and hyperopia are common conditions requiring corrective lenses. The familial clustering of myopia has been well established. Several chromosomal regions have been linked to high myopia (12q, 17q, and 18q), to quantitative refraction among twins (3q, 4q, 8p, and 11p), and to families with moderate myopia (22q). This study examined the familial aggregation and pattern of inheritance of ocular refraction in an adult population, by using data from the Beaver Dam Eye Study. METHODS: Familial correlations were examined and segregation analysis was performed on the average refractive error measurements in the right and left eyes after adjustment for age, sex, and education. Analyses were based on 2138 individuals in 620 extended pedigrees with complete data on age, sex, education, and spherical equivalent. RESULTS: Substantial positive correlation was found between siblings (0.33), parents and offspring (0.17), and cousins (0.10) and lower correlation among avuncular pairs (0.08) after adjustment for age, sex, and years of education. The results of this segregation analysis do not support the involvement of a single major locus throughout the entire range of refractive error. However, models allowing for familial correlation, attributable in part to polygenic effects, provided a better fit to the observed data than models without a polygenic component, suggesting that several genes of modest effect may influence refractive error, possibly in conjunction with environmental factors. CONCLUSIONS: These results support the involvement of genetic factors in the etiology of refractive error and are consistent with reports of linkage to multiple regions of the genome.

Family Health↗
PubMed2004

Ocular refraction: heritability and genome-wide search for eye morphometry traits in an isolated Sardinian population.

No genes influencing oculometric phenotypes have yet been identified, despite it being well known that eye morphometry is involved in refraction and that genetics may play an important role. We have therefore performed a heritability analysis and genome-wide search (GWS) of biometric ocular traits in an isolated Sardinian population, assessing the genetic contribution and identifying the associated genetic loci. A complete eye examination including refraction and ocular biometry measurements such as axial length (AL), anterior chamber depth (ACD) and corneal curvature (CC), was performed on 789 subjects. Heritability analysis was carried out by means of parent-offspring regression and variance component models. Univariate and bivariate linkage analysis was performed by using 654 microsatellite markers spanning the genome. CC showed a mean heritability of 57%. AL and ACD were found to have significantly different variances (P<0.01) in males and females, so that heritability was calculated separately for each sex. AL had an estimated heritability in females of 31% and in males of 60%, whereas ACD had an estimated heritability of 47% in females and of 44% in males. In the GWS, the most suggestive evidence of linkage was identified on chromosome 2 for AL (LOD 2.64), on chromosome 1 for ACD (LOD 2.32) and on chromosomes 7, 2 and 3 for CC (LOD 2.50, 2.44 and 2.34, respectively). High heritability of eye morphometry traits was thus revealed. The identified loci are the first linkage signals available in ocular biometry. Notably, the observed significant differences in parental transmission deserve further study.

Adolescent↗
PubMed1985

Experimental myopia in chicks: ocular refraction by electroretinography.

Application of devices that degrade the retinal image has been reported to produce enlargement of the ocular globe in young domestic chicks. Two such device types (domes and arches) were applied to 3-day-old chicks. The domes affected the entire visual field whereas the arches affected only the lateral field. A third group wore a thin circumorbital ring to control for possible mechanical impediments to growth. Untreated control chicks comprised a fourth group. At ages ranging from 3 to 7 wk, the chicks were refracted in their lateral visual fields with a Maxwellian view optometer based on Scheiner's principle, which yields an objective assessment of the refractive state of the photoreceptor image plane. One to seven measurements were taken from each of 48 urethane-anesthetized chicks. These indicated that the mean refractive states of the untreated eyes and the ring eyes were -0.20 D and -0.19 D, respectively, which did not differ significantly from emmetropia. In contrast, the mean refractive states of the arch eyes and the dome eyes were -4.11 D and -14.88 D, respectively, which differed significantly from emmetropia and from each other. The results indicate that early retinal image degradation can result in the relatively rapid development of a substantial myopia in these experimental animals.

Animals↗