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PubMed1983

Accommodation as the primary cause of low-luminance myopia. Experimental evidence.

Low-luminance myopia of subjects with one normal eye and one aphakic eye was measured with a laser optometer. Low-luminance myopia was registered in the normal eyes, but no such myopia could be found in the aphakic eyes. The same subjects' aphakic eyes were further tested with miotic and dilated pupils. Miosis or mydriasis did not significantly alter the results as compared with measurements obtained with normal pupil size. These results would appear to be the first direct experimental evidence that accommodation is the primary cause of low-luminance myopia.

Accommodation, Ocular↗
PubMed1987

Diabetic myopia--is it lens-induced? An oculometric study comprising ultrasound measurements.

An oculometric study has been performed to evaluate features possibly being responsible for a (permanent) shift towards myopia in eyes of diabetics, a trend apparent from previous clinical investigations. Having excluded cases of transient refractive change associated with poor metabolic control, we are dealing with adult subjects with stable refractive levels, also including cases of adult-onset myopia. Out of 62 diabetic and 48 non-diabetic eyes (age 17-23, diabetes duration 2-38 years) a careful matching according to age, sex and refraction provided 26 eye-pairs from 52 subjects for analysis. In 23 matched pairs there was low myopia. The lenses of diabetics appeared significantly thicker than in non-diabetics (mean difference 0.2 mm), and a higher lens power came close to significance. Corneal curvature, anterior chamber depth and axial length did not differ. A subsequent analysis of degree of lens thickness increase in diabetics revealed a positive correlation with diabetes duration. A thicker lens does not of necessity imply a higher lens power, but from the present data this is the most likely explanation of diabetic myopia in adults.

Adolescent↗
PubMed1989

Epikeratoplasty for adult and pediatric aphakia, myopia, and keratoconus: the Massachusetts Eye and Ear Infirmary experience.

Between February, 1985 and February, 1987, 49 eyes of 47 patients underwent epikeratoplasty for one of the following indications: adult aphakia (21 eyes; 20 patients), pediatric aphakia (10 eyes; 10 patients), myopia (7 eyes; 6 patients), and keratoconus (11 eyes; 11 patients). Follow-up at least 12 months (average = 18 months) is available for all 49 eyes. Of 49 eyes, 44 (90%) were anatomically successful with an intact, clear lenticule at least 12 months post-operatively, with no significant difference between the four groups (adult aphakia = 90%, pediatric aphakia = 90%, myopia = 86%, and keratoconus = 91%). The functional success rate, however, was 91% for keratoconus, 81% for adult aphakia, 80% for pediatric aphakia, and only 43% for myopia. We conclude that epikeratoplasty can be an effective tool in the treatment of carefully selected patients with adult or pediatric aphakia and keratoconus, but has only limited applicability in the management of myopia.

Adult↗
PubMed1992

Myopia among medical students in Norway.

In this study the prevalence of myopia and age at onset among medical students were determined. Of the 140 senior medical students at The Faculty of Medicine, University of Trondheim, Norway, 133 (75 females, 58 males) were examined. Visual acuity was tested and the refractive error was measured using automated refraction and clinical refractive technique. The prevalence of myopia was found to be 50.3% in the right eye (n = 67) without significant difference between female and male students. The refractive state was unrelated to body height. Among the myopic students, the mean equivalent sphere was -2.34 +/- 2.01 D in the right eye (range -9.25 D to -0.25 D). A clear relationship was detected between the current amount of myopia and the age at which corrective lenses were first prescribed. However, as much as 43.3% of the myopic students wearing corrective lenses first received these at the age of about 20 years, indicating a relatively high prevalence rate of adult-onset myopia.

Adult↗
PubMed1993

Low-grade myopia in children with regressed retinopathy of prematurity.

Myopia is a frequent sequelae of retinopathy of prematurity. The mechanism for myopia development in children born preterm is not well understood. From a group of 33 myopic preterm children we selected those who had regressed retinopathy and myopic values < or = 5 D. Seventeen children met our criteria. Of them, 10 patients could be re-examined. Factors related to myopia development were analyzed and compared to a control group of 12 children born fullterm with emmetropia or low hypermetropia, as well as another group of 10 fullterm children with myopic values < or = 5 D. The age of children ranged from 9 to 14 years in all groups. The mean birth weight in myopic premature children was 1249.3 g. Higher keratometric diopter values were found in myopic premature children than in emmetropic fullterm children (p < 0.05) and myopic fullterm children (p < 0.05). Increased axial length values were observed in myopic fullterm children when compared to myopic premature children (p < 0.05) In children born preterm the corneal refractive power seems to play a major role in myopia development.

Adolescent↗
PubMed1987

Local retinal regions control local eye growth and myopia.

In chicks, visual deprivation leads to myopia and enlargement of the vitreous chamber of the eye. When chicks were raised with white translucent occluders over their eyes so that either the nasal half, the temporal half, or all of the retina was visually deprived, the resulting myopia (median = -15 diopters) was limited to the deprived part of the retina, regardless of which half of the retina was visually deprived; the nondeprived part remained nearly emmetropic. Correspondingly, the vitreous chamber was elongated only in the region of the visual deprivation, resulting in eyes with different asymmetric shapes depending on which retinal region was deprived. These results argue for a local regulation of ocular growth that is dependent on vision and suggest a hypothesis to explain the epidemiological association of myopia in humans with large amounts of reading. Because most nonfoveal retinal neurons have large receptive fields, they cannot resolve the individual letters on the printed page; this may lead to their activity being less during reading than during most other forms of visual stimulation. Thus, the impoverished stimulus situation of reading may lead to myopia, as do other types of visual form deprivation.

Animals↗
PubMed2004

Childhood myopia and parental smoking.

AIM: To examine the relation between exposure to passive parental smoke and myopia in Chinese children in Singapore. METHODS: 1334 Chinese children from three schools in Singapore were recruited, all of whom were participants in the Singapore Cohort study Of the Risk factors for Myopia (SCORM). Information on whether the father or mother smoked, number of years smoked, and the number of cigarettes smoked per day during the child's lifetime were derived. These data were correlated with contemporaneously obtained data available in SCORM. The children's cycloplegic autorefraction, corneal curvature radius, and biometry measures were compared with reported parental smoking history. RESULTS: There were 434 fathers (33.3%) and 23 mothers (1.7%) who smoked during their child's lifetime. There were no significant trends observed between paternal smoking and refractive error or axial length. After controlling for age, sex, school, mother's education, and mother's myopia, children with mothers who had ever smoked during their lifetime had more "positive" refractions (adjusted mean -0.28 D v -1.38 D) compared with children whose mother did not smoke (p = 0.012). CONCLUSIONS: The study found no consistent evidence of association between parental smoking and refractive error. There was a suggestion that children whose mothers smoked cigarettes had more hyperopic refractions, but the absence of a relation with paternal smoking and the small number of mothers who smoked in this sample preclude definite conclusions about a link between passive smoking exposure and myopia.

Child↗
PubMed2006

Optical coherence tomography to monitor photodynamic therapy in pathological myopia.

AIM: To evaluate the role of optical coherence tomography (OCT) in determining choroidal neovascularisation (CNV) activity before and after photodynamic therapy (PDT) in patients with pathological myopia. METHODS: 33 patients (33 eyes) with pathological myopia and being treated with PDT were included. Every 3 months all patients were evaluated and presence or absence of leakage on fluorescein angiography, presence of intraretinal or subretinal fluid on OCT, and macular and choroidal neovascular complex thickness on OCT, were determined at each examination. RESULTS: The macular thickness decreased significantly after PDT at 6 months (p = 0.001) and at 12 months follow up (p = 0.01). However, no significant changes in CNV thickness were measured after PDT at 6 months of follow up (p = 0.418) and at 12 months of follow up (p = 0.521). Once the diagnosis of CNV associated with pathological myopia was established, before treatment, OCT had a sensitivity of 96.96% for detecting CNV activity. After treatment, OCT had a good sensitivity (95.23%) and a moderate specificity (69,69%) in determining CNV activity, which resulted in a diagnostic efficiency (proportion of correct results) of 79.62%. CONCLUSIONS: OCT appears to be useful for indicating CNV activity. Therefore, it may serve as a complementary technique for deciding the need for PDT and re-treatment in patients with pathological myopia.

Adult↗
PubMed1995

Refractive and visual results and patient satisfaction after excimer laser photorefractive keratectomy for myopia.

A study of excimer laser photorefractive keratectomy was performed on 108 patients. Variation in individual refractive outcome was noted, particularly for the higher levels of correction. At 12 months, of those with up to 3 dioptres of myopia, 93% were within 1 dioptre of emmetropia, 100% achieved an acuity of 6/12 unaided, 69% were very pleased with their result, and 10% were very disappointed. Of those with between 3.1 and 6 dioptres of myopia, the respective figures were 75%, 73%, 65%, and 11%. For those with over 6 dioptres of myopia the respective figures were 46%, 58%, 38%, and 23%. Some patients were disappointed despite having achieved good unaided visual acuity. Forty seven per cent of patients lost at least one Snellen line of best corrected acuity. Glare was a problem for some of the time in over 60%. Perceived distortion of vision was a problem for all of the time in 11% to 31% of cases depending on the initial level of myopia. In some cases the refraction continued to change between 12 months and 20 months.

Adult↗
PubMed2000

Radiotherapy for subfoveal neovascularisation associated with pathological myopia: a pilot study.

BACKGROUND/AIM: Limited treatments are available for this disease process. A pilot study was performed to determine the toxicity and efficacy of external beam radiotherapy for subfoveal neovascular membranes and subretinal haemorrhage associated with pathological myopia. METHODS: A randomised, prospective study was carried out on 39 patients with subfoveal neovascularisation associated with high myopia. 20 patients underwent radiotherapy and the remaining 19 were observed as a randomised comparison group. All patients were followed up for at least 24 months. Subfoveal choroidal neovascular membranes (CNVMs) were treated with a single lateral 6 MV photon beam to a dose of 10 Gy in five fractions over 5-7 days. Post-treatment measurements included corrected visual acuity, area of CNVM, and occurrence of radiotherapy related complications, and adverse reactions. To assess changes of area of CNVM, the initial (pretreatment) size of the CNVM was set to 100%, and all post-treatment measurements were normalised relative to the initial size. RESULTS: No significant acute morbidity was noted. There was no significant difference in age, sex, refractive error, visual acuity, and area of CNVM at baseline between the treatment group and control group. The mean change of the size of the CNVM for 2 years was 155% (SD 156%) in the treatment group and 249% (124%) in the control group. The increase in the size of CNVM in the treatment group was significantly smaller than that in the control group (p = 0.0452). In the treated eyes, the visual acuity before and 1 and 2 years after radiotherapy were 0.111 (22.2/200), 0.091 (18.2/200), and 0.086 (19.2/200), respectively. In the control eyes, visual acuity before and 1 and 2 years after the start of the follow up were 0.141 (34.2/200), 0.089 (17.8/200), and 0.063 (12.6/200). The patients in the treatment group showed no significant change for 2 years, and those in the control group showed a significant decrease in the visual acuity (p = 0.0033). The changes of logMAR of visual acuity for 2 years after the start of the follow up were +0.019 (0. 443) in the treatment group and +0.347 (0.374) in the control group. There was a statistically significant difference between them (p = 0. 0173). Multiple regression analysis on the treatment group showed that the most significant predictive variable for the visual acuity 2 years after the treatment was the combination of pretreatment visual acuity and refractive error. CONCLUSIONS: Radiotherapy appeared to have a favourable treatment effect in eyes with subfoveal neovascular membranes and haemorrhage associated with pathological myopia. Further investigation is needed to evaluate the efficacy of radiotherapy for subfoveal neovascularisation associated with pathological myopia.

Aged↗
PubMed2002

Myopia in secondary school students in Mwanza City, Tanzania: the need for a national screening programme.

BACKGROUND/AIMS: The prevalence of significant refractive errors and other eye diseases was measured in 2511 secondary school students aged 11-27 years in Mwanza City, Tanzania. Risk factors for myopia were explored. METHODS: A questionnaire assessed the students' socioeconomic background and exposure to near work followed by visual acuity assessment and a full eye examination. Non-cycloplegic objective and subjective refraction was done on all participants with visual acuity of worse than 6/12 in either eye without an obvious cause. RESULTS: 154 (6.1%) students had significant refractive errors. Myopia was the leading refractive error (5.6%). Amblyopia (0.4%), strabismus (0.2%), and other treatable eye disorders were uncommon. Only 30.3% of students with significant refractive errors wore spectacles before the survey. Age, sex, ethnicity, father's educational status, and a family history of siblings with spectacles were significant independent risk factors for myopia. CONCLUSION: The prevalence of uncorrected significant refractive errors is high enough to justify a regular school eye screening programme in secondary schools in Tanzania. Risk factors for myopia are similar to those reported in European, North-American, and Asian populations.

Adolescent↗
PubMed1977

Acquired myopia in 11-year-old children.

Children who had acquired myopia by the age of 11 years were identified from a nationally representative sample. There were no overall sex differences in its occurrence but myopia was more common in children from non-manual families than in those from manual families. Short-sighted children were more likely to come from small families and to be of higher birth order than children with normal vision, and these associations held within each social class. At 11 years myopic children showed striking advantages in educational performance over their normal-sighted peers, as judged by tests of reading, arithmetic, and general ability. After adjustments had been made for social background, this age gain still amounted to over one year. Findings obtained at 7 years of age showed that superior educational attainments were already apparent before the onset of myopia. Children with myopia read in their leisure time more often than normally sighted children, but despite the visual impairment, they participated in outdoor sports as often as other children.

Child↗
PubMed1991

Impact of heredity in myopia.

A series of 109 like-sexed twin pairs in the age group 30-31 years (54 monozygotic and 55 dizygotic) with one or both members of the twins with myopia was found in the Finnish Twin Cohort. The series was based on a random sample of 1,200 twins in one age stratum of the cohort. The twins received a questionnaire on their health status with special reference to eye diseases and symptoms. The refractive status of the twin pairs was ascertained by asking the twins to send their latest prescription for glasses to the authors or the refraction was obtained from the ophthalmologists or opticians of the twins. The mean difference in refraction between the monozygotic twins was 1.19 dptr in the right eyes and 1.15 dptr in the left eyes. The difference between dizygotic pairs was 2.34 dptr in the right eyes and 2.47 dptr in the left eyes. Analysis of variance showed that the difference in refraction between the two eyes of a twin pair was not significant. The mean difference in refraction between the monozygotic twins was significantly lower than that between dizygotic twins (p less than or equal to 0.001). The intrapair variances were doubled among dizygotic twin pairs compared to monozygotic twin pairs in the male group. The intrapair variance in the female group was 4-fold among dizygotic twin pairs as compared to monozygotic twin pairs. Heritability of myopia was 0.58 (0.74 for males and 0.61 for females) when myopia was considered a dichotomous variable. This result suggests that inheritance has a substantial effect on the etiology of myopia.

Adult↗
PubMed2003

TGFbeta-induced factor: a candidate gene for high myopia.

PURPOSE: To investigate the coding exons of transforming growth factor (TGF)-beta-induced factor (TGIF) for mutations in Chinese patients with high myopia. METHODS: Seventy-one individuals with high myopia of -6.00 D or less and 105 control subjects were screened by DNA sequencing for sequence alterations. Univariate analysis and logistic regression were performed to identify single-nucleotide polymorphisms (SNPs) and their interactions in TGIF that may be associated with myopia. RESULTS: Six SNPs showed a significant difference (P < 0.05) between patient and control subject in univariate analysis. Four of them cause codon changes: G223R, G231S, P241T, and A262G. Among all the SNPs that entered multivariate analysis, only 657(T-->G) showed statistical significance in the logistic regression model (odds ratio 0.133; 95% confidence interval 0.037-0.488; P = 0.002). CONCLUSIONS: TGIF is a probable candidate gene for high myopia. Further studies are needed to identify the underlying mechanism.

Adult↗
PubMed2003

Retinotopic accommodation responses in myopia.

PURPOSE: A reduced sensitivity to retinal image blur has been reported in myopes. Diminished blur detection reduces the error signal to the retinotopic (blur-induced) accommodation system and results in impaired accommodation responses under retinotopic conditions. This study was conducted to investigate retinotopic accommodation responses in emmetropia and myopia under dynamic conditions. METHODS: Static accommodation responses to a blur-only target with vergences of 0 to 4.5 D were measured with an optometer. Microfluctuations of accommodation were recorded with the subject viewing the target at a vergence of 4 D, and dynamic step responses were measured for step stimuli from 2.5 to 3.5 D and 2.0 to 4.0 D, with the optometer in dynamic recording mode. Measurements were obtained from a group of 32 visually normal emmetropes (EMMs) and subjects with progressing myopia. RESULTS: Stimulus-response curves were not significantly different between the refractive groups. Subjects with late-onset myopia (LOMs) demonstrated significantly larger accommodation microfluctuations compared with emmetropes and subjects with early-onset myopia (EOMs). Fourier analysis revealed that the increase in the magnitude of the fluctuations was mediated by the low-frequency components. Accommodation step responses revealed longer reaction times in LOMs. Further analysis showed that LOMs responded to accommodation step stimuli only between 43% and 64% of the time. In contrast, the other groups showed a response rate of almost 100%. CONCLUSIONS: The experiments demonstrate a reduction in retinotopic processing in LOMs, which results in an increased variability in their dynamic accommodation response to stationary near targets and reduced performance for dynamic step tasks. The results demonstrate a reduced blur appreciation under dynamic conditions in these refractive groups that may lead to periods of retinal image blur of varying magnitude during near work.

Accommodation, Ocular↗
PubMed2004

Linkage analysis of the genetic loci for high myopia on 18p, 12q, and 17q in 51 U.K. families.

PURPOSE: To determine the extent to which high myopia in a cohort of 51 U.K. families can be attributed to currently identified genetic loci. METHODS: The families comprised 245 subjects with phenotypic information and DNA available, of whom 170 were classified as affected. Subjects were genotyped for microsatellite markers spanning approximately 40cM regions on 18p (MYP2), 12q (MYP3) and 17q, together with markers flanking COL2A1, COL11A1, and FBN1. Two-point linkage analyses were performed using the same disease gene segregation model as was used in the original publications, followed by nonparametric and multipoint analyses using Genehunter (http://linkage.rockefeller.edu/soft/gh/ provided in the public domain by Rockefeller University, New York, NY), with additional maximization over the parameter alpha, the proportion of linked families. RESULTS: Evidence of linkage was found for the MYP3 locus on 12q (two-point Zmax = 2.54, P = 0.0003 and multipoint hLOD = 1.08 at alpha = 0.24, P = 0.023 for marker D12S332; nonparametric linkage [NPL] = 1.49, P = 0.07 for marker D12S1607). For the 17q locus there was weak evidence of excess allele sharing and linkage under a recessive model (NPL = 1.34, P = 0.09 for marker D17S956; two-point hLOD = 1.24 at alpha = 0.30 for marker D17S1795; multipoint hLOD = 1.24 at alpha = 0.17, P = 0.014 for marker at 77.68 cM, between markers D17S956 and D17S1853). No significant linkage was found to the MYP2 locus on 18p, or to the COL2A1, COL11A1, and FBN1 genes. CONCLUSIONS: These results suggest that the MYP3 locus on 12q could be responsible for high myopia in approximately 25% of the U.K. families showing apparent autosomal dominant transmission, but that the loci on 18p and 17q are less common causes. Thus, additional loci for high myopia are likely to be the cause of the majority of cases of high myopia in the United Kingdom.

Chromosome Mapping↗
PubMed2005

Use of optical coherence tomography to assess variations in macular retinal thickness in myopia.

PURPOSE: To investigate the variation in macular retinal thickness in otherwise normal young Asian myopic subjects by using optical coherence tomography (OCT). METHODS: One hundred thirty ophthalmically normal men 19 to 24 years of age with myopia (spherical equivalent, -0.25 to -14.25 D) underwent examination of one randomly selected eye. Visual acuity, refraction, slit lamp examination, applanation tonometry, gonioscopy, A-scan ultrasound, fundus examination, visual field testing, and optic disc photography were performed. Exclusion criteria were visual acuity worse than 20/30, previous intraocular surgery, intraocular pressure >21 mm Hg, or other ocular diseases. Three horizontal transfixation and three vertical transfixation OCT scans (ver.4.1; Carl Zeiss Meditec, Dublin, CA) of 6 mm each were conducted on each eye by a single operator. Neurosensory retinal thicknesses at 100 points along each scan were measured, and the overall average, maximum, and minimum retinal thicknesses were analyzed by simple linear regression and analysis of variance. RESULTS: The average macular retinal thickness (overall) was 230.9 +/- 10.5 microm and was not significantly related to the degree of myopia. The mean maximum retinal thickness (at the parafovea) was 278.4 +/- 13.0 microm, and correlated negatively with axial length (P = 0.03). The mean minimum retinal thickness (at the foveola) was 141.1 +/- 19.1 microm, and this was positively correlated with axial length (P = 0.015) and spherical equivalent (P = 0.0002). The retina was thicker at the superior and nasal parafovea compared to the inferior or temporal parafovea. CONCLUSIONS: Average retinal thickness of the macula does not vary with myopia. However, the parafovea was thinner and the fovea thicker with myopia.

Adult↗
PubMed2005

Shape of the retinal surface in emmetropia and myopia.

PURPOSE: To determine and compare the shapes of the retinas of emmetropic and myopic eyes. METHODS: Nonrotationally symmetrical ellipsoids were mathematically fitted to the retinal surfaces of 21 emmetropic and 66 myopic eyes (up to -12 D) of participants aged 18 to 36 years (mean, 25.5) using transverse axial and sagittal images derived from magnetic resonance imaging. RESULTS: The shapes of the ellipsoids varied considerably between subjects with similar refractive errors. The shapes were oblate (steepening toward the equator) in most of the emmetropic eyes (i.e., the axial dimensions of the ellipsoids were smaller than both the vertical and horizontal dimensions). As myopia increased, all ellipsoid dimensions increased with the axial dimension increasing more than the vertical dimension, which in turn increased more than the horizontal dimension (increases in approximate ratios 3:2:1). The relative difference in the increase of these dimensions meant that as the degree of myopia increased the retinal shape decreased in oblateness. However, few myopic eyes were prolate (flattening toward the equator). Independent of myopia, the ellipsoids were tilted about the vertical axis by 11 degrees +/- 13 degrees , and ellipsoid centers were decentered horizontally by 0.5 +/- 0.4 mm nasally and 0.2 +/- 0.5 mm inferiorly, relative to the fovea. CONCLUSIONS: In general both emmetropic and myopic retinas are oblate in shape, although myopic eyes less so. This finding may be relevant to theories implicating the peripheral retina in the development of myopia.

Adolescent↗