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PubMed2004

[Comparison of clinical results between LASIK method and ICL implantation in high myopia].

In a retrospective study the authors evaluate clinical results of the LASIK (laser in situ keratomileusis) and the implantation of the implantable posterior chamber contact lens phakic IOL (ICL) (STAAR Surgical) to correct high myopia. The purpose of the study was to assess which of those two methods is more reliable in patients to correct myopia in the range -10.0 to -23.0 diopters. The LASIK method was presented of a group of 70 eyes of 48 patients with preoperative spherical equivalent average of -12.9 +/- 3.8 diopters (Dsf) and average astigmatism of -0.99 +/- 1.2 cylindrical diopters (Dcyl). The group was divided into two parts: one part was with the desired postoperative emmetropia--46 eyes (65.7%), and part two was with the desired postoperative residual myopia up to -3.0 Dsf--24 eyes (34.3%). The method of ICL implantation was presented of a group of 36 eyes of 21 patients with preoperative spherical equivalent average of -15.21 +/- 4.0 Dsf and average astigmatism of -0.92 +/- 0.69 Dcyl. Also this group was divided into two parts: One part was with the desired postoperative emmetropia--25 eyes (69.4%), and part two was with the desired postoperative residual myopia up to -3.0 Dsf--11 eyes (30.6%). The developments of postoperative refraction in time (1 week to 3 years after the surgery), the final postoperative refraction and its stability and (6 months to 3 years after the surgery) as well as the occurrence of complications in both studied groups were evaluated. In the assessment of the postoperative refraction development in groups of desired emmetropia, the average uncorrected visual acuity (UCVA), average postoperative spherical equivalent and astigmatism were evaluated. In the groups with desired residual myopia the average best-corrected visual acuity (BCVA), average postoperative spherical equivalent, and astigmatism were followed. Three years after the surgery in groups with desired emmetropia, the average postoperative spherical equivalent was -0.99 Dsf and reduction of myopia by 92.0% in the LASIK method, and -0.52 Dsf and reduction of myopia by 96.1% in ICL implantation respectively. In cases of desired residual myopia those final values were -1.74 Dsf with reduction of myopia by 86% for LASIK, and -1.58 Dsf with reduction myopia by 90.7% for ICL implantation. Final postoperative BCVA (given in lines of Snellen optotypes) was in 1.7% (1 eye) loss of 2 lines, in 17.1% (12 eyes) 1 line loss, in 55.7% (39 eyes) without change, in 22.9% (16 eyes) improvement by one line. In ICL implantation, the BCVA was unchanged in 25% (9 eyes), in 72.3% (26 eyes) improved by 1 line, and in 1 eye improved by 2 lines. In the group with LASIK method, in 17.1% (12 eyes) a reoperation followed, and in the group with ICL implantation, in 2.7% (1 eye) the other operation followed (ICL explantation). From the results emerged that for high myopia over -10 Dsf is the ICL implantation more appropriate because of its faster postoperative visual rehabilitation, more stabile and better final postoperative refraction and lower complications ratio.

Adult↗

PubMed2005

A new locus for autosomal dominant high myopia maps to 4q22-q27 between D4S1578 and D4S1612.

PURPOSE: Myopia is the most common visual problem in the world. High myopia, the extreme form of myopia that can be complicated by retinal detachment and macular degeneration, affects 1%-2% of the general population. The genes responsible for nonsyndromic high myopia have not been identified although several chromosome loci have been suggested. Additional loci for the majority of high myopia, especially in Asian populations, await discovery. A large Chinese family with autosomal dominant high myopia was collected in order to map the genetic locus as an initial step towards identifying the genetic cause of high myopia in this family. METHODS: A Chinese family with 12 individuals affected with high myopia was ascertained from a small village in central China. Phenotypic information and DNA samples were collected from 18 individuals, including 11 affected and 7 unaffected individuals. A genome-wide scan was performed using markers spaced at about 10 cM intervals for genotyping and two-point linkage analysis was carried out. Candidate genes were sequenced. RESULTS: High myopia, ranging from -5.00 D to -20.00 D with typical fundus changes, is transmitted as an autosomal dominant trait in this family. High myopia in this family shows linkage to markers in a 20.4 cM region between D4S1578 and D4S1612, with maximum lod scores of 3.11 and 3.61 at theta=0 by D4S1564 and by the D4S2986-D4S1572-D4S1564-D4S406-D4S1580-D4S402 haplotype, respectively. Sequence analysis of the retinal pigment epithelium-derived rhodopsin homolog (RRH; OMIM 605224) gene inside the linked region did not identify any causative mutations. CONCLUSIONS: A novel locus (MYP11) for autosomal dominant high myopia in a Chinese family maps to 4q22-q27 but is not associated with mutations in RRH.

Adult↗

PubMedDate not supplied

Myopia and plasma cortisol.

Estimation of plasma cortisol by fluorometric technique desorbed by Mallingly's was carried out in 56 cases, including 38 cases of myopia (19 cases of simple myopia and 19 cases of degenerative myopia) and 18 normal individuals. Urinary 17-keto steroids/24 hours was also estimated by Zimmermann technique in 12 out of the 56 cases, which include 8 cases of myopia (4 cases of simple myopia and 4 cases of degenerative myopia) and 4 normal individuals as control. Plasma cortisol level is lower in simple and degenerative myopia than in normal subjects, but on statistical analysis the difference was not of much significance. Patients with simple myopia with positive family history showed lower value of plasma cortisol than patients with simple myopia with negative family history, the difference was also statistically insignificant (P-0.1). In degenerative myopia patients, with and without family history, there was very little difference in plasma cortisol level and statistically highly insignificant (P-0.8). Urinary 17 keto steroid/24 hour values are lower in simple and degenerative myopia than in normal subjects.

17-Ketosteroids↗

PubMed1997

The Glenn A. Fry Award Lecture (1995). Myopia development in childhood.

PURPOSE: The Orinda Longitudinal Study of Myopia is a 12-year project examining predictive factors for the onset of myopia, the underlying etiologies of myopia, and normal eye growth in school children. METHODS: This paper reports on all measurements made of the ocular components (cycloplegic refractive error, corneal curvature, crystalline lens power, and axial ocular dimensions), parental history of myopia, and near work activity in children participating in the Orinda Longitudinal Study of Myopia between 1989 and 1993. An analysis of the interaction between parental history of myopia and children's near work is conducted on the cross-sectional study data from 1993. RESULTS: The cross-sectional and longitudinal data show a gradual decrease in refractive error from low hyperopia toward emmetropia, no shift in corneal curvature, a gradual decrease in crystalline lens power, thinning of the crystalline lens, and elongation of the eye between the ages of 6 and 14 years. Parental history is more contributory to a statistical model predicting myopia than is near work, but near work is a significant factor as well. We can find no evidence of statistical interaction between parental history and near work in explaining the presence or absence of myopia. CONCLUSIONS: The emmetropization process is evident in the gradual decrease in refractive error toward emmetropia, the axial elongation of the eye, and the compensating decrease in crystalline lens power. Both nature and nurture play a role in the etiology of myopia, although the predominant role appears to belong to a positive parental history of myopia. This role does not appear to be through an interaction between parental myopia status and children's near work activity.

Adolescent↗

PubMed2002

Near-work activity, night-lights, and myopia in the Singapore-China study.

OBJECTIVE: To investigate the relationship among near-work activity, night-lights, and myopia in schoolchildren in Singapore and Xiamen, China. METHODS: The refractive error and ocular dimensions of 957 Chinese schoolchildren aged 7 to 9 years in Singapore and Xiamen, China, were determined using cycloplegic autorefraction and A-scan ultrasound biometry. Information on near-work activity (number of books read per week, reading in hours per day) and night-light use before age 2 years was obtained. RESULTS: The prevalence rate of myopia was 36.7% (95% confidence interval [CI], 33.0%-40.3%) in Singapore and 18.5% (95% CI, 14.0%-23.1%) in Xiamen, China. The crude odds ratio (OR) of higher myopia (at least -3.0 diopters) for children who read more than 2 books per week was 3.50 (95% CI, 2.15-5.70). In a multivariate logistic regression model, the OR of higher myopia for children who read more was 2.81 (95% CI, 1.69-4.69), adjusted for age, night-light use, parental myopia, and country, whereas there was no association between night-light use before age 2 years and higher myopia (OR, 1.54; 95% CI, 0.92-2.58), after controlling for age, books read per week, parental myopia, and country. MAIN OUTCOME MEASURES: The ORs of higher myopia for children who read more and children who are exposed to night-lights before age 2 years. CONCLUSIONS: Reading (number of books per week) may be associated with higher myopia in Chinese schoolchildren. However, night-light use does not seem to be related to higher myopia.

Child↗

PubMed1996

Familial aggregation and prevalence of myopia in the Framingham Offspring Eye Study.

OBJECTIVES: To examine familial relationships for myopia among siblings and the distribution of myopia in an adult population aged 23 to 78 years. METHODS AND PARTICIPANTS: Eye examinations were conducted in a cross-sectional study on the offspring of the Framingham Eye Study cohort. Between 1989 and 1991, 1585 persons, the offspring of 1319 parents, underwent refraction and were tested for best corrected visual acuity. A person was considered myopic if at least one eye had a spherical equivalent refractive error of at least -1.00 diopter. RESULTS: For both sexes, prevalence of myopia decreased with increasing age, from about 60% for ages 23 to 34 years to about 20% for ages 65 years and older. Among men, both age and years of education were related to myopia. Among women, age was related to myopia, but years of education were not. Age-, sex-, and education-adjusted analyses, using the second-order generalized estimating equations approach, showed a strong association of myopia between siblings. The association between siblings decreased with increasing between-siblings age difference: the estimated odds ratio was about 5 for an age difference of 2 years and half that for an age difference of 10 years. CONCLUSIONS: The relative importance of genetic and environmental factors in explaining familial relationships for myopia remains unclear. Nevertheless, the large increase in myopia prevalence for more recent birth cohorts and the decrease in the strength of the between-siblings association for myopia with increasing between-siblings age difference suggest an important role for environmental factors in the cause of myopia.

Adult↗

PubMed2006

Effects of intravitreally and intraperitoneally injected atropine on two types of experimental myopia in chicken.

Atropine, a non-selective muscarinic receptor antagonist, is currently the most potent agent used to prevent myopia in animal models and children. However, the ocular target tissues are not well defined. To learn more about the effect of atropine on experimental myopia, atropine was applied both intravitreally and systemically (intraperitoneally) to chickens wearing either negative lenses or light diffusers. Furthermore, the effect of ipsilateral intravitreal atropine on myopia development in the saline-treated fellow eye was studied. Monocular intravitreal injections of atropine were performed daily for a period of 4 successive days, starting at day 8 post-hatching. Fellow eyes received saline injections. Chicks were fitted with -7D lenses, either over the atropine-injected eyes only (unilateral "lens-induced myopia (LIM)"), or over both eyes (bilateral LIM). Other groups of chicks were fitted with translucent diffusers over the atropine-injected eyes (unilateral "form deprivation myopia (FDM)"). Finally, atropine was intraperitoneally injected for 4 days in chicks that wore monocularly -7D lenses. Refractive errors (RE) were measured with infrared photoretinoscopy and axial length (AL) with A-scan ultrasonography. Atropine prevented development of myopia in both unilateral LIM and FDM in a dose-dependent fashion. Fifty percent inhibition of myopia was observed at a dose of 25 microg (unilateral LIM) or 90 microg atropine (bilateral LIM) and complete inhibition at 750 microg; in unilateral FDM, 50% inhibition occurred at 2.5 microg and almost 100% inhibition at 250 microg. Interestingly, at the highest dose of atropine (2500 microg), the treated eyes became even more hyperopic compared to the saline-injected contralateral eyes with normal visual experience. In the bilateral LIM model, atropine suppressed development of myopia in both the treated and the saline-injected control eye. However, about 8.3 times higher doses were necessary to achieve comparable contralateral suppression. Since this ratio is lower than the vitreous volume to blood volume ratio (about 1:23 in young chicks), it seems unlikely that systemic dilution of the intravitreally injected drug can fully account for the contralateral suppression. Intraperitoneal injection inhibited myopia development only at the highest dose (2500 microg) but, strikingly, this inhibition was still less when the same dose was provided through the vitreous of the fellow eye. Both eyes seem to be coupled by a yet unknown, perhaps neuronal pathway. Estimations of the scleral concentrations of atropine after intravitreal injection are compatible with the assumption that the suppression of myopia by atropine occurs by direct inhibition of scleral chondrocytes.

Animals↗

PubMed2005

Prevalence of myopia at 9 months in infants with high-risk prethreshold retinopathy of prematurity.

PURPOSE: To examine the prevalence of myopia and high myopia at 9 months corrected age in premature infants who participated in the multicenter randomized trial of Early Treatment for Retinopathy of Prematurity (ETROP). DESIGN: Randomized, controlled clinical trial. PARTICIPANTS: Four hundred one infants with birth weights of <1251 g in whom prethreshold ROP developed in one or both eyes and who were determined to have a significant risk (> or =15%) of poor structural outcomes without treatment, based on the risk management for ROP program. INTERVENTION: Infants with bilateral high-risk prethreshold ROP (n = 317) had 1 eye randomized to early treatment, and the fellow eye was managed conventionally. In asymmetric cases (n = 84), the eye with high-risk prethreshold ROP was randomized to early treatment or conventional management (control). Eyes randomized to early treatment at high-risk prethreshold ROP and eyes randomized to conventional management in which threshold ROP developed received peripheral retinal photocoagulation or cryotherapy. Conventionally managed eyes in which threshold ROP did not develop were observed. Cycloplegic retinoscopy data were obtained at 9 months corrected age from 321 eyes treated early and 307 eyes managed conventionally. MAIN OUTCOME MEASURES: Prevalence of myopic (spherical equivalent > or = 0.25 diopters [D]) and highly myopic (> or =5.00 D) eyes in each group. RESULTS: The prevalence of myopia (64.5% vs. 69.4%; P = 0.06) and high myopia (25.5% vs. 28.3%; P = 0.20) was similar between eyes treated at high-risk prethreshold and high-risk prethreshold eyes managed conventionally. Among high-risk eyes managed conventionally, the prevalence of myopia (78.2% vs. 53.3%) and high myopia (37.6% vs. 11.2%) was higher when threshold ROP developed than when regression without treatment occurred. Among eyes treated at high-risk prethreshold ROP, the prevalence of myopia (93.3% vs. 91.7% vs. 60.6%) and of high myopia (53.3% vs. 33.3% vs. 20.8%) was higher in eyes with abnormal angle of temporal retinal vessels or macular ectopia than in eyes with no retinal residua. This also held true for conventionally managed eyes. CONCLUSIONS: Early treatment at high-risk prethreshold did not place eyes at greater risk of myopia and high myopia than did conventional management of eyes with high-risk prethreshold ROP.

Cryotherapy↗

PubMed1995

Association of intraocular pressure and myopia in children.

PURPOSE: While elevated intraocular pressure (IOP) is associated with myopia in adults, its potential influence on the growth of eyes in juveniles without glaucoma is controversial. To address this issue, a possible relation between IOP and refraction in children was sought. METHODS: A cross-sectional survey of IOP was conducted in children presenting to the Division of Pediatric Ophthalmology at The Children's Hospital of Philadelphia for a complete eye examination. Measurement of IOP was attempted in all children, including those with amblyopia, prematurity, and strabismus. Exclusion criteria were abnormalities of the posterior pole and/or conditions such as cataract that precluded assessment of refractive error. For analysis, myopia was defined as a spherical equivalent of more than 1 diopter (D) of myopia. Logistic regression was used to assess the association between other patient characteristics and presence of myopia. RESULTS: Intraocular pressure testing was attempted in all age groups, but was more successful in older children. Reliable readings were obtained on 321 subjects. The mean age was 9.8 years, with a mean IOP of 17.3 mmHg in the right eye and 17.2 mmHg in the left and a mean spherical equivalent of +0.2 D in the right eye and +0.1 D in the left. Increasing age, a family history of myopia, and amblyopia were associated myopia. Increasing IOP also was related to myopia. Even when patients with amblyopia, strabismus, and prematurity were exclude, age, family history of myopia, and IOP again were associated with myopia. CONCLUSIONS: These results indicate that IOP in children may be higher in myopic than nonmyopic eyes. Whether IOP could contribute to the mechanisms causing the abnormal eye growth of childhood myopia requires further study.

Adolescent↗

PubMed1999

Patterns of late corneal scarring after photorefractive keratectomy in high and severe myopia.

OBJECTIVE: To study the correlation between scarring 1 year after photorefractive keratectomy (PRK), final refraction, and degree of myopia. DESIGN: A retrospective, noncomparative case series. PARTICIPANTS: One hundred twenty eyes of 78 patients underwent PRK for high and severe myopia. Thirty-nine eyes had a pre-PRK spherical equivalent (SE) between -9.5 and -18.25 diopters (D) (severe myopia). Eighty-one eyes had a pre-PRK SE between -6.25 and -9.25 D (high myopia). Follow-up time ranged between 12 and 37 months with a mean of 18.2 months. INTERVENTION: Multizone PRK with the VISX 20/20 excimer laser. MAIN OUTCOME MEASURES: Corneal scarring, final best-corrected visual acuity (BCVA), and refraction. RESULTS: There were 71.7% of eyes with severe myopia and 60.5% of eyes with high myopia found to have any pattern of stromal scarring, which was classified as focal, semiannular, annular, and discoid. Discoid scars were rare (6.6%) and found in 12.8% of severe myopic eyes compared to 3.7% of high myopic eyes. Only 50% of the eyes with a discoid scar achieved final BCVA between 6/6 and 6/9 compared to 81.6% of the eyes with a clear cornea. The severe myopic eyes with a discoid scar had the highest level of final undercorrection (-5.0 D) compared to a maximum of -1.5 D in the high myopia group. The severe myopic eyes with a discoid scar had a higher number of retreatments (4 of 5) compared to the high myopia group (1 of 3). Other types of scars were less clinically significant. CONCLUSIONS: Photorefractive keratectomy was efficient in the correction of high myopia but less so in severe myopia, in which discoid scarring was more frequent and more clinically significant, being associated with significant regression. Other types of scarring were less clinically significant.

Adolescent↗

PubMed2003

Role of the sclera in the development and pathological complications of myopia.

Myopia is one of the most prevalent ocular conditions and is the result of a mismatch between the power of the eye and axial length of the eye. As a result images of distant objects are brought to a focus in front of the retina resulting in blurred vision. In the vast majority of cases the structural cause of myopia is an excessive axial length of the eye, or more specifically the vitreous chamber depth. In about 2% of the general population, the degree of myopia is above 6 dioptres (D) and is termed high myopia. The prevalence of sight-threatening ocular pathology is markedly increased in eyes with high degrees of myopia ( > -6 D). This results from the excessive axial elongation of the eye which, by necessity, must involve the outer coat of the eye, the sclera. Consequently, high myopia is reported as a leading cause of registered blindness and partial sight. Current theories of refractive development acknowledge the pivotal role of the sclera in the control of eye size and the development of myopia. This review considers the major biochemical mechanisms that underlie the normal development of the mammalian sclera and how the scleral structure influences the rate of eye growth during development. The review will characterise the aberrant mechanisms of scleral remodelling which underlie the development of myopia. In describing these mechanisms we highlight how certain critical events in both the early and later stages of myopia development lead to scleral thinning, the loss of scleral tissue, the weakening of the scleral mechanical properties and, ultimately, to the development of posterior staphyloma. This review aims to build on existing models to illustrate that the prevention of aberrant scleral remodelling must be the goal of any long-term therapy for the amelioration of the permanent vision loss associated with high myopia.

Animals↗

PubMed2000

Myopia profile in Copenhagen medical students 1996-98. Refractive stability over a century is suggested.

PURPOSE: To assess the myopia prevalence and profile in today's Danish medical students and to compare the pattern with previous and contemporary investigations. METHODS: As part of the tutoring in ophthalmology 1996-98 Copenhagen medical students of five successive terms (in their 10th semester, n=294) were interviewed and spot-checked about their refraction. Myopia from -0.5 D was recorded and myopia onset age stated. RESULTS: The age range was 22-41 years, median age 26. Myopia ranging from -0.5 to -8 D was encountered in 147 students (50% of all; females 53.9%, males 45%). In seven the myopia was unilateral. Median values for myopia degree and onset age were -2.5 D and 16 years in female myopes (n=89) which differed significantly from the male values (n=58) of -1.5 D and 18 years. Including the age of 18 as lower cut-off for adult-onset myopia 44.9% of the myopes belonged to this category. CONCLUSIONS: The results are in close agreement with recent Norwegian student investigations, and there is no obvious trend of a worsening of the academic myopia issue in our part of the world. This is in marked contrast to student myopia profiles as reported in Taiwan, Singapore, and Hong Kong where myopia is booming, by number and degree.

Adult↗

PubMed1998

A second locus for familial high myopia maps to chromosome 12q.

Myopia, or nearsightedness, is the most common eye disorder worldwide. "Pathologic" high myopia, or myopia of <=-6.00 diopters, predisposes individuals to retinal detachment, macular degeneration, cataract, or glaucoma. A locus for autosomal dominant pathologic high myopia has been mapped to 18p11.31. We now report significant linkage of high myopia to a second locus at the 12q21-23 region in a large German/Italian family. The family had no clinical evidence of connective-tissue abnormalities or glaucoma. The average age at diagnosis of myopia was 5.9 years. The average spherical-component refractive error for the affected individuals was -9.47 diopters. Markers flanking or intragenic to the genes for the 18p locus, Stickler syndromes type I and II (12q13.1-q13.3 and 6p21.3), Marfan syndrome (15q21.1), and juvenile glaucoma (chromosome 1q21-q31) showed no linkage to the myopia in this family. The maximum LOD score with two-point linkage analysis in this pedigree was 3.85 at a recombination fraction of .0010, for markers D12S1706 and D12S327. Recombination events identified markers D12S1684 and D12S1605 as flanking markers that define a 30.1-cM interval on chromosome 12q21-23, for the second myopia gene. These results confirm genetic heterogeneity of myopia. The identification of this gene may provide insight into the pathophysiology of myopia and eye development.

Adult↗

PubMed2007

Myopia prevalence in Chinese-Canadian children in an optometric practice.

PURPOSE: The high prevalence of myopia in Chinese children living in urban East Asian countries such as Hong Kong, Taiwan, and China has been well documented. However, it is not clear whether the prevalence of myopia would be similarly high for this group of children if they were living in a Western country. This study aims to determine the prevalence and progression of myopia in ethnic Chinese children living in Canada. METHODS: Right eye refraction data of Chinese-Canadian children aged 6 to 12 years were collated from the 2003 clinical records of an optometric practice in Mississauga, Ontario, Canada. Myopia was defined as a spherical equivalent refraction (SER) equal or less than -0.50 D. The prevalence of myopia and refractive error distribution in children of different ages and the magnitude of refractive error shifts over the preceding 8 years were determined. Data were adjusted for potential biases in the clinic sample. A questionnaire was administered to 300 Chinese and 300 Caucasian children randomly selected from the clinic records to study lifestyle issues that may impact on myopia development. RESULTS: Optometric records of 1468 children were analyzed (729 boys and 739 girls). The clinic bias adjusted prevalence of myopia increased from 22.4% at age 6 to 64.1% at age 12 and concurrently the portion of the children that were emmetropic (refraction between -0.25 and +0.75 D) decreased (68.6% at 6 years to 27.2% at 12 years). The highest incidence of myopia for both girls ( approximately 35%) and boys ( approximately 25%) occurred at 9 and 10 years of age. The average annual refractive shift for all children was -0.52+/-0.42 D and -0.90+/-0.40 D for just myopic children. The questionnaire revealed that these Chinese-Canadian children spent a greater amount of time performing near work and less time outdoors than did Caucasian-Canadian children. CONCLUSIONS: Ethnic Chinese children living in Canada develop myopia comparable in prevalence and magnitude to those living in urban East Asian countries. Recent migration of the children and their families to Canada does not appear to lower their myopia risk.

Asian People↗

PubMed2006

Inferring myopia over the lifecourse from uncorrected distance visual acuity in childhood.

AIM: To report the usefulness of uncorrected distance visual acuity (DVA) at 16 years to "screen" for myopia status and to assess the lifetime risk of myopia, based on a national birth cohort. METHODS: 1867 members of the 1958 British birth cohort for whom there were data on acuity at 16 years had autorefraction, as part of a biomedical survey, at 45 years. Reduced uncorrected DVA at age 16 years (6/12 or worse in both eyes) was compared with adult refraction (spherical equivalent). RESULTS: Only a quarter of individuals in the population studied who had developed myopia by 45 years of age had reduced acuity at 16 years of age. Notably, half of all adults with moderate myopia (-2.99 to -5.99) and 31% (11/35) with severe myopia (> or =-6) had good uncorrected DVA in both eyes at 16 years of age. Thus, sensitivities were low, ranging from 16% for all myopia (cut-off point spherical equivalent -0.5) to 69% for severe myopia (cut-off point spherical equivalent -6). However, a high (91%) lifetime probability of primary myopia (spherical equivalent > or =-0.5) given a reduced uncorrected DVA at 16 years was found. CONCLUSION: In this population, reduced uncorrected DVA in childhood is an inaccurate and inappropriate intermediate "phenotype" for capturing adult myopia status. However, our findings support assessment of DVA in secondary school children as an effective method of identifying refractive error (both myopia and hypermetropia).

Adolescent↗

PubMed1984

Myopia induction in animals following alteration of the visual input during development: a review.

In this review the effects of changes in the quality of the visual environment on the development of myopia during eye growth in various mammalian and avian species are described. The effect of changes in the light/dark cycle on myopia development has been studied only in the avian eye, mainly that of the domestic fowl. In the eyes of chicks reared from hatching to maturity under continuous illumination, the following findings were reported: myopia, astigmatism, increases in axial length and equatorial width, shallow anterior chamber, increase in corneal diameter, reduction of corneal curvature, increased intra-ocular pressure (IOP), low outflow facility, reduction in aqueous space, buphthalmos, macrophthalmos and glaucoma. The above mentioned changes were consistent in the majority of the studies. In a few experiments where a change in one of the above mentioned parameters was not found, no tendency for the opposite condition was reported. When the illumination level of the visual environment was changed in the avian eye there was an increase in the total size of the eye as well as exophthalmos. Other parameters were not examined. It is quite possible that myopia and eye enlargement in avians are caused by entirely different processes than myopia and eye enlargement in mammals since they can be induced either by changes in the diurnal rhythm or by low intensity light. The involvement of the pineal gland in the control of eye growth in avians is therefore possible. The effect of continuous dark rearing was studied in the avian and in the mammalian eye. In developing chicks reared in continuous darkness some enlargement of the eye took place, but a condition of hyperopia was found as opposed to the expected myopia. This result is in agreement with the results of experiments performed on monkeys and cats reared from infancy to adulthood in complete darkness. The effect of near vision conditions during growth was studied in monkeys, cats and chicks confined to small chambers, cages or rooms. A slight myopia was usually obtained in all of the above species but the incidence of myopia increased consistently in the experimental animals compared to the normal controls. The effect of optically restricting the visual field during growth was studied in chicks. Using special occluders, the eyes of the chicks were exposed only to the frontal fields of vision. This manipulation induced a considerably high myopia and an increase in the axial length of the eye and in the depth of the anterior chamber. Removal of the occluders resulted in a reversal of the induced myopia.(ABSTRACT TRUNCATED AT 400 WORDS)

Accommodation, Ocular↗

PubMedDate not supplied

Predicting of myopia progression in school children.

Myopia in 214 school children has been followed from one to nine years. The children have been divided in groups according to the age of onset of myopia and the amount of final myopia at the age of 15 or 16 has been recorded. If myopia started before puberty (at the age of 10 or younger) 70% of the children ended up with myopia of -3.0 to -5.75 D, only 12.5% remained under -3.0 D, and 17.5% had myopia -6.0 D or more. If myopia began at the ages of 11-15, 66.7% remained under -3.0 D, 32.2% reached -3.0 to -5.75 D, and only 1.1% of the children had myopia of -6.0 D or more. Of all the 214 children, 95.8% had myopia less than -6.0 D at the age of 15-16 years. However, the individual variation is very wide, and it is difficult to predict the final amount of myopia in school years in an individual case.

Adolescent↗

PubMedDate not supplied

Photorefractive keratectomy for -1.25 to -25.00 diopters of myopia.

BACKGROUND: We evaluated prospectively the efficacy, predictability, stability, and safety of photorefractive keratectomy (PRK) for myopia. METHODS: Three hundred sixty-nine eyes of 257 patients were treated with an Aesculap-Meditec MEL 60 excimer laser. Treated eyes were divided into 3 groups: low myopes (-1.25 to -6.00 D), 226 eyes; medium myopes (-6.10 to -10.00 D), 104 eyes; high myopes (-10.10 to -25.00 D), 39 eyes. Follow-up at 12 months was available for 348 eyes (94%). RESULTS: One year after surgery the number of eyes within +/- 1.00 D of emmetropia was 182 (86.7%) for low myopes, 43 (40.5%) for medium myopes, and 12 (30.8%) for high myopes. Values for +/- 0.50 D were low: 142 (67.6%), medium: 29 (29.3%), and high: 9 (23.1%). Three eyes with low myopia (1.4%) and 5 eyes with medium myopia (5.1%) lost 2 or more lines of spectacle-corrected visual acuity. None of the high myopes lost 2 or more lines. Uncorrected visual acuity of 20/20 or better was achieved in 82 eyes (39%) with low myopia; 20/40 or better was achieved in 183 eyes (87.1%). Five eyes (5.1%) of medium myopes achieved 20/20 or better; 52 eyes (52.5%) with medium myopia achieved 20/40 or better. Zero eyes with high myopia achieved 20/20 or better; 11 eyes (28.8%) achieved 20/40 or better. CONCLUSION: Photorefractive keratectomy proved to be an effective method to correct myopia up to -6.00 D. For myopia greater than -6.00 D, good results were achieved in most eyes when myopia was less than -10.00 D, but efficacy and predictability decrease. To avoid systematic undercorrection, slight overcorrection must be attempted with the Aesculap-Meditec MEL 60 excimer laser for the treatment of myopia.

Adolescent↗