SEARCH · PubMed Health

Results for “Myopia”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources

PubMed2007

Near work, education, family history, and myopia in Greek conscripts.

AIMS: To investigate potential factors associated with the presence of myopia in a cohort of young adult men carrying out their military service in Greece. METHODS: A nested case-control study of 200 conscripts (99 myopes and 101 non-myopes). The cohort consisted of approximately 1000 conscripts in compulsory national service. All cohort members had been screened for refractive errors by Snellen visual acuity measurement at presentation to military service; individuals not achieving visual activity 6/6 underwent noncycloplaegic refraction. The study sample consisted of the first 99 myopic and 101 nonmyopic conscripts who attended the study. In-person interviews of these 200 conscripts were conducted to obtain information on family history, occupation, level of education, near-work activities, and sleeping behaviour. chi(2) and Mann-Whitney tests were used as univariate analysis methods to identify the potential factors associated with the presence of myopia. Multiple logistic regression was used to estimate the adjusted relative risk of myopia. RESULTS: Univariate analysis showed that parental family history (P<0.001), older age (P<0.001), tertiary education (P<0.001), hours of reading per day (P<0.001), hours of computer use per day (P<0.001), and higher social classes (P<0.001) were associated with myopia. Sleeping in artificial or ambient light was not associated with myopia (P=0.75). Multiple logistic regression analysis showed that older age (OR=1.25, 95% CI 1.05-1.49), tertiary education (OR=12.67, 95% CI 3.57-44.88) and parental family history (OR=3.39, 95% CI 1.56-7.36) were independently associated with myopia. CONCLUSION: In young Greek conscripts, parental family history, older age, and education level are independently associated with myopia.

Adult↗

PubMed1998

[Magnetic resonance imaging of of the right extraocular muscle paths in healthy persons and in patients with high myopia].

PURPOSE: To investigate the paths of the rectus extraocular muscles (EOMs) in patients with high axial myopia, using high-resolution magnetic resonance imaging (MRI). METHODS: Coronal MR images (T1 weighting) of the orbit were obtained with controlled gaze. Positions of recti EOMs were measured digitally in the middle of the orbit, using the NIH-image analysis software. Orbits of three different patient groups were analysed. Group 1 (n = 14 orbits): Patients with high axial myopia and restrictive eye motility. Group 2 (n = 8 orbits) subjects with high axial myopia and normal eye motility. Controls (n = 11 orbits) with normal eye motility and no refractive error. RESULTS: In comparison to the controls, patients with high axial myopia were found to have significant misplacement of the recti EOMs. Thus in group 1 (group 2 within brackets) the lateral rectus muscle (LR) was misplaced 2.9 (1.4) mm into the lower temporal quadrant p < 0.001 (p = 0.07). The course of the superior rectus muscle (SR) was shifted 1.5 (1.5) mm medially p = 0.02 (p = 0.03) and the path of the inferior rectus muscle (IR) 1.3 (1.3) mm medially p = 0.06 (p = 0.06). The medial rectus muscle (MR) showed a 1.3 (1.2) mm downward mislocation p = 0.01 (p = 0.07). CONCLUSIONS: In patients with high axial myopia (group 1 and group 2) misplacement of all rectus EOMs could be demonstrated by high resolution MRI with controlled gaze. All patients showed an approximately equal amount of MR, SR and IR mislocation. However, misplacement of the LR was significantly greater in patients with high myopia and restrictive eye motility (group 1) than in those without restrictive ocular motility (group 2), p = 0.03. We therefore assume that LR downward mislocation is a major determinant for restrictive eye motility in high myopia.

Adult↗

PubMed2003

Collagen gene expression and the altered accumulation of scleral collagen during the development of high myopia.

The development of high myopia is associated with reduced scleral collagen accumulation, scleral thinning, and loss of scleral tissue, in both humans and animal models. Reduced collagen fibril diameter is also observed in the sclera of eyes with high myopia. The present study investigated aspects of scleral collagen synthesis and degradation, in a mammalian model of high myopia, to elucidate the factors underlying scleral changes. General synthesis and degradation of scleral collagen was investigated in monocularly deprived tree shrews, through the in vivo administration of [(3)H]proline and subsequent assay of scleral tissue for [(3)H]collagen. In addition, PCR enriched cDNA, produced from tree shrew scleral mRNA, was used to synthesize probes for hybridization to custom gene arrays consisting of partial sequences for 11 collagen subtypes. Finally, real-time reverse transcriptase-PCR was employed to investigate collagen type I, III, and V mRNA expression in the sclera of myopic, contralateral control, and normal tree shrew eyes. Scleral [(3)H]proline incorporation was reduced at the posterior pole of myopic eyes following 5 days of monocular deprivation (-36 +/- 4%), whereas [(3)H]proline content was similar in treated and control eyes before myopia induction (-1 +/- 8%) but was reduced in myopic eyes following 5 (-8 +/- 2%), 12 (-15 +/- 4%), and 24 (-10 +/- 4%) days of myopia induction. The majority of the collagens investigated were found to be expressed in the sclera, with 11 subtypes being identified. Collagen type I mRNA expression was reduced in the sclera of myopic eyes (-20 +/- 7%), however, collagen type III (+2 +/- 9%) and type V (-1 +/- 6%) expression was unchanged relative to control, resulting in a net increase in the ratio of expression of collagen type III/type I and collagen type V/type I (22 and 25%, respectively). These results show that reduced scleral collagen accumulation in myopic eyes is a result of both decreased collagen synthesis and accelerated collagen degradation. Furthermore, changes in collagen synthesis are driven by reduced type I collagen production. Short term increases in the ratio of newly synthesized collagen type III/type I and type V/type I are likely to be important in the increasing frequency of small diameter scleral collagen fibrils observed in high myopia and may be important in the subsequent development of posterior staphyloma in humans with pathological myopia.

Animals↗

PubMed2004

Isoform-specific changes in scleral transforming growth factor-beta expression and the regulation of collagen synthesis during myopia progression.

The development of high myopia is associated with altered scleral extracellular matrix biochemistry. Previous studies highlight the importance of collagen turnover in this process, yet it is unclear which factors control scleral remodeling. This study used a mammalian model of myopia to investigate the capacity of TGF (transforming growth factor)-beta1, -beta2, and -beta3 to influence scleral remodeling in myopia. RT-PCR confirmed the presence of all mammalian TGF-beta isoforms in scleral tissue and scleral fibroblasts. Myopia was experimentally induced via monocular deprivation of pattern vision, and animals were allocated to two groups depending on the duration of treatment (1 or 5 days). Down-regulation of each isoform was apparent after only 1 day of myopia development (TGF-beta1, -32%; TGF-beta2, -27%; TGF-beta3, -42%). Whereas the decrease in TGF-beta1 and -beta3 expression was relatively constant between the two time points, differential down-regulation of TGF-beta2 was found between days 1 (-27%) and 5 (-50%). In vitro experiments, using primary scleral fibroblasts, demonstrated the capacity of all isoforms to increase collagen production in a dose-dependent manner. Changes in TGF-beta levels, which mimicked those during myopia induction, caused an approximately 15% reduction in collagen synthesis, which is qualitatively similar to those previously reported in vivo. These data represent the first demonstration of TGF-beta3 expression in the sclera and implicate all three TGF-beta isoforms in the control of scleral remodeling during myopia development. In addition, the early alterations in TGF-beta expression levels may reflect a role for these cytokines in mediating the retinoscleral signal that controls myopic eye growth.

Animals↗

PubMed1999

Prevalence of myopia in Sherpa and Tibetan children in Nepal.

BACKGROUND: Tibetan and Sherpa children living in Nepal share a common ancestry in Tibet and areas to the north of Nepal, but it is evident that these people experience widely contrasting educational and environmental conditions. The purpose of this study was to compare the prevalence of myopia in children with similar genetic backgrounds but who are exposed to contrasting environments. METHODS: Unaided vision and refractive error was measured in 555 Tibetan children in Kathmandu and 270 Sherpa children in the Solu Khumbu region of Nepal. RESULTS: There were marked differences in vision and the prevalence of myopia in the two groups. Ninety-two percent of the Sherpa children had Snellen vision of 20/22 (0.89) or better compared with 70% of the Tibetan children. The range of refractive errors was -6.50 to +7.00 D for the Tibetan children and -1.00 to +3.50 D for the Sherpa children. The Sherpa children had a prevalence of myopia of 2.9% compared with 21.7% for the Tibetan children. CONCLUSIONS: The prevalence of myopia in Sherpa children is low and their rural lifestyle appears to be relatively unstressed. Tibetan children have a higher prevalence of myopia and more rigorous schooling. We did not establish a causal relationship between myopia and the type of schooling, or the environment in general, but we did demonstrate that a simple, rural lifestyle is at least compatible with a virtual absence of myopia.

Adolescent↗

PubMed2000

Factors related to the progression of myopia in Singaporean children.

PURPOSE: To examine the possible factors related to the progression of myopia in Singapore children. METHODS: One hundred fifty-three Singapore children aged 6 to 12 years were recruited to participate in a concurrent cohort study of the risk factors for the progression of myopia. Socioeconomic status, outdoor activity, and near-work activity were documented in a face-to-face clinic interview. The changes in cycloplegic subjective refraction and autorefraction were ascertained with the use of a Nidek ARK 900 over a 2-year period. RESULTS: The average rate of progression of myopia as measured by subjective refraction was -0.59 D per year (95% confidence interval -0.52, -0.66). Younger children and children who were more myopic at the beginning (refractive error worse than -2.0 D) of the study had higher myopia progression rates. CONCLUSIONS: Myopia progression was faster for younger children and for children who had more severe myopia at baseline. Socioeconomic status and near-work activity were not related to myopia progression.

Child↗

PubMed2003

Prevalence of myopia among 12- to 13-year-old schoolchildren in northern Mexico.

PURPOSE: The aim of this article was to report the prevalence of refractive errors, mainly myopia, among 12- to 13-year-old children in a metropolitan setting in Mexico. METHODS: A total of 1035 schoolchildren were examined in a field study in Monterrey, Mexico. The examination included best-corrected visual acuity and refraction during cycloplegia. A sample of the children was sent to a pediatric eye clinic and underwent cycloplegic refraction with an autorefractor. RESULTS: We found a prevalence of myopia (>/=-0.5 D SE) of 44%, whereas bilateral myopia was present in 37% of the children. In the total sample, high myopia (>/=-5D) was found in 1.4%. The prevalence of myopia was significantly higher in girls. Only 20% of children with bilateral myopia used prescription glasses; 8% had prescribed glasses, but did not use them. Hyperopia (>/=+1 D) was present in 6.0% of the total population, and astigmatism (>/=-1.5 D) was present in 9.5%. CONCLUSIONS: The prevalence of myopia among 12- to 13-year-old children in Mexico is high. The majority of cases are low grade, and a large number of the myopic children do not have, or do not use, prescription glasses.

Adolescent↗

PubMed2004

Community-based study of the association of high myopia in children with ocular and systemic disease.

PURPOSE: High myopia in childhood is associated with important ocular and systemic conditions. However in the UK, high myopia in early childhood is not specifically identified in current ophthalmology, optometry, or orthoptic protocols for screening, referral, or investigation. An ongoing study in the West Midlands, UK, is investigating high myopia presenting to community health care clinics with the aim of compiling guidelines for assessment and subsequent referral. METHODS: Children with high myopia were identified from community optometric and orthoptic sources and invited for an ophthalmology and optometry examination to ascertain possible ocular or systemic disease. RESULTS: High myopia with no associated ocular or systemic condition was present in 15 (56%) of the children. In seven children (25%), associated ocular problems were found including unrecognized retinal dystrophies and amblyopia. Systemic disorders associated with high myopia were found in five children (19%) and included Sticklers syndrome, Weill-Marchesani syndrome, and homocystinuria. In one child, the diagnosis made before this study was found to be incorrect, and in another child, the results were inconclusive. In two cases, the diagnosis of a systemic condition in the child led to the identification of the disease in at least one relative. CONCLUSIONS: There is a high prevalence of ocular and systemic abnormality in young children seen in the community. Optometric and ophthalmologic assessment of children less than 10 years with myopia > or =5 D is likely to identify significant ocular or systemic disease, a proportion of which will respond to medical intervention. Detection and prompt referral of these cases by community health care services may be expected to prolong vision and possibly life expectancy.

Abnormalities, Multiple↗

PubMed2004

Prevalence of myopia in local and international schools in Hong Kong.

PURPOSE: This study aims to investigate genetic and environmental influences on physiological myopia by studying the difference in myopia prevalence between local schools and international schools in Hong Kong. METHODS: Vision screening was carried out in local and international schools for students 13 to 15 years old. Types of refractive error were identified by visual acuity measurement, the presence of spectacles, a simple refraction, and the use of plus and minus ophthalmic lenses. RESULTS: Three local schools and six international schools participated in the study. Two hundred eighty-nine students were from the local schools, and 789 students were from the international schools. Prevalence of myopia at the local schools ranged from 85 to 88%, whereas it ranged from 60 to 66% in the international schools. Students in the international schools were subdivided into Chinese origin, white, mixed Chinese, and Asian. Prevalence of myopia was highest in the Chinese group (82.8%) and lowest in the white group (40.5%). There was no age or gender difference in the prevalence of myopia. CONCLUSIONS: Hong Kong Chinese students had a higher prevalence of myopia regardless of whether they studied in local or international schools when compared with other ethnic groups, such as whites. This further supports a genetic input into myopia development.

Adolescent↗

PubMed2005

Myopia progression is specified by a double exponential growth function.

PURPOSE: The purpose of this study was to demonstrate how well a modified Gompertz double exponential growth function delineates the diverse courses of myopia progression found in individual eyes. The function is: R = Re + Rc(0.07295)(a(x - t0)) where the spherical equivalent refractive error at a given age R equals the initial refractive error (Re) plus the overall refractive change (Rc) times a double exponential function with the base (0.07295) representing the proportion of Rc that occurs when maximum acceleration is reached, a is a curvature coefficient, t0 is the age of onset and x is age. METHODS: This function was fit to longitudinal refractive data (spherical equivalents) for both eyes of 36 myopic children. The fits were required to meet a stringent set of criteria, including fitting transitions in and out of myopia progression and having no systematic errors or arbitrary constants. RESULTS: Correlation between values on the refractive function and corresponding data of individual eyes is high (mean r = 0.973 +/- 0.020), the sum of squares between the data and function is low, and all other criteria are met. The rates of refractive change and acceleration were derivable from this function. It has been shown that, if peak acceleration rate is used as a criterion for the onset of myopia progression, then myopization onset starts a year earlier (mean = 8.93 years) than when a -0.50-D onset criterion is used (mean = 9.93 years), and it usually starts before the spherical equivalent reaches zero (mean R = +0.09 D). Age of onset is highly correlated with the duration of myopia progression (r = 0.693), which in turn is correlated with the amount of myopia achieved (r = 0.443). CONCLUSIONS: We demonstrate that the double exponential function delineates the dynamics of myopia progression onset, offset, and the derivatives that describe the mechanisms underlying the growth process that causes myopia and have explained the advantages of this function. The function can be used to more accurately portray the course of individual subject's myopic progression.

Adolescent↗

PubMed2006

Prevalence rate of myopia in schoolchildren in rural Mongolia.

PURPOSE: The prevalence of myopia among some young Asian populations has been reported to be increasing to near epidemic proportions. Mongolia is an emerging Asian economy with limited ophthalmic resources. The purpose of this study was to define a level of myopia for school-aged children in rural Mongolia. METHODS: A total of 1057 schoolchildren, aged between 7 and 17 years, were examined in two remote, rural suums (districts) of Mongolia: one situated in the western aimag (province) of Khovd and the other in the central steppe's aimag of Zavkhan. The examination included retinoscopy, subjective refraction, best-corrected visual acuity, and direct ophthalmoscopy. RESULTS: The total prevalence of myopia (more than -0.5 D spherical equivalent) was 5.8% (95% confidence intervals [CIs], 4.4-7.2%). Female students exhibited a significantly higher prevalence of myopia in comparison to male students: 8.3% (95% CIs, 6.0-10.6%) compared with 3.1%, respectively (95% CIs, 1.6-4.6%): p < 0.001). For those with myopia, the median level of myopia for both genders was -0.75 D spherical equivalent (SE) and ranged from -0.50 to -28.00 D SE in girls and from -0.50 to -6.50 D SE in boys. CONCLUSIONS: To the authors' knowledge, this is the first study to report a level of myopia for schoolchildren in Mongolia. The prevalence rate is low in comparison to reported studies for other Far Eastern countries.

Adolescent↗

PubMed2003

A synopsis of the prevalence rates and environmental risk factors for myopia.

The prevalence rates of myopia are higher in urban Asian cities such as Hong Kong and Singapore. One observation over the past few decades is that the prevalence rates of myopia have been rising and there is an epidemic of myopia in Asia. The age-old question of the roles of nature and nurture in this process remains unanswered. The strongest evidence for an environmental link to myopia is near work activity. Childhood exposure to night lighting has also been explored in different studies but the results have been mixed. Twin studies, segregation analysis and association studies have demonstrated that hereditary factors play an important role in myopia development. The exact nature and interplay of genetic and environmental factors is not known and data suggest that environmental factors may interact with genetic factors to increase the risks of developing myopia. Future research is needed to identify specific modifiable lifestyle factors and genetic markers for myopia. This will enable preventive measures such as health education to be instituted.

Animals↗

PubMed1995

Myopia of adult onset. Can analyses be based on patient memory?

One hundred and fifty-one adult subjects (age 26-64 years) with simple myopia ('simple' = absence of significant astigmatism and anisometropia) were asked about their myopia onset, here defined as the age when first having spectacles to correct vision trouble for distance. A precise memory appeared in 148. Usually, they could substantiate their information by detailed accounts regarding how and when. Evidently, the first pair of glasses is a strong emotional experience. Accordingly, information appears to be reliable when properly asking the patient. The sample confirmed established knowledge: the earlier the onset, the higher the final myopia. Adult onset myopia is usually low, but occasionally intermediate or high myopia cases are encountered. Adult onset myopia appears more frequently than evident from textbooks and literature on refractive distribution. A frequency estimate based on Danish material thus suggests that at least 25-30% of all adult age myopia is also of adult onset.

Adult↗

PubMed1995

Myopia of prematurity, clinical patterns. A follow-up of Danish children now aged 3-9 years.

A discussion of myopia of prematurity is based on 16 low-birth weight children now aged 3-9 years. During their first months after delivery, retinopathy of prematurity had been observed in all but one subjects-here possibly missed due to incomplete control. Two subjects had cryotherapy. Two eyes out of 32 got blind; another 4 eyes became weak-sighted. The primary aim of the longitudinal study was to describe the variation in-and the course of-refraction, as apparent from serial examinations, the natural history so to say, to add new facets to our concept of myopia of prematurity and possibly to identify subgroups. Transient and fluctuating myopia being physiological in the first postnatal months, the diagnosis "myopia of prematurity' should not be forwarded too early. Some cases of early myopia which did not regress as usual over the first 6 months, later showed a reduction in degree of myopia over 1-2 years. Others pertained to the classical description of a stationary myopia, often of high degree, diagnosed in early childhood. Even in the favourable tail of the present distribution corrected visual acuity appeared subnormal according to age norms.

Child↗

PubMed1997

Reoperations after photorefractive keratectomy for moderate and high myopia.

PURPOSE: To contribute data regarding results of reoperation with excimer laser for the treatment of residual myopia, and to improve corneal clarity following previous photorefractive keratectomy for 'moderate' (< -9 D) and 'high' (> -9 D) myopia. METHODS: Surface reablations with excimer laser (5 mm treatment diameter) were performed to correct residual myopia and remove subepithelial scars. Refraction, visual acuity, and corneal clarity were recorded with average follow-up of one and two years after reoperation. RESULTS: In 27 eyes with 'moderate' myopia before the first operation, significant improvement was obtained regarding refraction (changed from -2.3 +/- 1.56 D before retreatment to -0.58 +/- 1.31 D after retreatment (p < 10[-3])), and uncorrected visual acuity (improved to > or = 0.8 in 51.8% of the cases). All cases (6 eyes) with corneal scars improved. Six eyes with 'high' myopia showed no improvement of refraction following reoperation. Effects on corneal clarity were mixed in that group. CONCLUSION: We were able to improve the results of photorefractive keratectomy for 'moderate' myopia with a second excimer laser ablation. The risks involved in retreatments of such eyes are small. In 'high' myopia, reablations with a 5 mm treatment zone did not improve the refractive outcome on a long-term basis.

Adult↗

PubMed1983

Genetic aspects of myopia among the Shia Muslim Dawoodi Bohras of Udaipur, Rajsthan.

359 sibs from 92 families, where any one member of the family (basic unit of study) was found to be affected, were screened for myopia. Data on age at onset, parity and severity were studied in relation to consanguinity. Significant consanguinity differentials in the manifestation of myopia were seen. Offspring who were the product of a consanguineous mating manifested myopia more frequently as compared to the offspring from the non-consanguineous matings (control group). Males from consanguineous matings were affected in a higher frequency and manifested myopia at early ages. Myopia was found to be birth order-dependent. Pedigree analysis has shown that myopia is not a monogenic trait. The most plausible mode of inheritance of myopia seems to be polygenic with variable expressivity, and shows gene dosage effect.

Birth Order↗

PubMed2003

New locus for autosomal dominant high myopia maps to the long arm of chromosome 17.

PURPOSE: To map the gene(s) associated with autosomal dominant (AD) high-grade myopia. METHODS: A multigeneration English/Canadian family with AD severe myopia was ascertained. Myopes were healthy, with no clinical evidence of syndromic disease, anterior segment abnormalities, or glaucoma. The family contained 22 participating members (12 affected). The average age of diagnosis of myopia was 8.9 years (range, birth to 11 years). The average refractive error for affected adults was -13.925 D (range, -5.50 to -50.00). Microsatellite markers for genotyping were used to assess linkage to several candidate loci, including three previously identified AD high-myopia loci on 18p11.31, 12q22-q23, and 7q36. Syndromic myopia linkage was excluded by using intragenic or flanking markers for Stickler syndrome types 1, 2, and 2B; Marfan syndrome; Ehlers-Danlos syndrome type 4; and juvenile glaucoma. A full genome screening was performed, with 327 microsatellite markers spaced by 5 to 10 cM. Two-point linkage was analyzed using the FASTLINK program run at 90% penetrance and a myopia gene frequency of 0.0133. RESULTS: Linkage to all candidate loci was excluded. The genome screening yielded a maximum two-point lod score of 3.17 at theta = 0 with microsatellite marker D17S1604. Fine mapping and haplotype analysis defined the critical interval of 7.71 cM at 17q21-22. CONCLUSIONS: A novel putative disease locus for AD high-grade myopia has been identified and provides additional support for genetic heterogeneity for this disorder.

Child↗

PubMed2004

IQ and the association with myopia in children.

PURPOSE: To evaluate the association between intelligence and myopia in children. METHODS: Cycloplegic refraction and ocular biometry parameters, including axial length, vitreous chamber depth, lens thickness, anterior chamber depth, and corneal curvature were obtained in 1204 Chinese school children aged 10 to 12 years from three schools who were participants in the Singapore Cohort Study Of the Risk Factors for Myopia (SCORM). Intelligence quotient (IQ) was assessed using the nonverbal Raven Standard Progressive Matrix test. RESULTS: After controlling for age, gender, school, parental myopia, father's education, and books read per week, myopia (spherical equivalent [SE]) of at least -0.5 D was associated with high nonverbal IQ (highest quartile) versus low IQ (lowest quartile) (odds ratio = 2.4; 95% confidence interval, 1.7-3.4). Controlling for the same factors, children with higher nonverbal IQ scores had significantly more myopic refractions (-1.86 D for children with nonverbal IQ in the highest quartile compared with -1.24 D for children with nonverbal IQ in the lowest quartile; P = 0.002) and longer axial lengths (24.06 mm versus 23.80 mm; P = 0.022). Nonverbal IQ accounted for a greater proportion of the variance in refraction compared with books read per week. CONCLUSIONS: Nonverbal IQ may be an independent risk factor of myopia, and this relationship may not be explained merely by increased reading (books per week) among myopes. An interesting observation is that nonverbal IQ may be a stronger risk factor for myopia compared with books read per week. The complexity of the relationships between nonverbal IQ, reading, and myopia warrant additional studies to clarify any cause-effect relationship.

Books↗