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PubMedDate not supplied

Laser in situ keratomileusis for myopia and hyperopia using the Lasersight 200 laser in 300 consecutive eyes.

PURPOSE: To evaluate effectiveness, safety, predictability, and short-term stability of laser in situ keratomileusis (LASIK) using the LaserSight Compac-200 Mini excimer laser with software version 9.0, for all refractive errors. METHODS: One hundred fifty consecutive patients (300 eyes) that received bilateral LASIK for myopia, hyperopia, and astigmatism were studied prospectively. A new 9.0 software version applying a modified nomogram that takes advantage of bilateral surgery was used. Follow-up at 6 months was available for 267 eyes (89%). RESULTS: Six months postoperatively, 131 eyes (96.32%) in the low to moderate myopia group (-1.00 to -5.99 D; n=136) had a spherical equivalent refraction within +/-1.00 D, and 123 eyes (90.44%) were within +/-0.50 D of emmetropia. In the high to extreme myopia group (-6.00 to -25.00 D; n=114), 97 eyes (87.08%) had a spherical equivalent refraction within +/-1.00 D and 78 eyes (68.42%) were within +/-0.50 D of emmetropia. In the hyperopia group (+1.00 to +6.00 D; n=50), 44 eyes (88%) had a postoperative spherical equivalent refraction within +/-1.00 D, and 31 eyes (62%) were within +/-0.50 D of emmetropia. Mean change in spherical equivalent refraction at 6 months was less than -0.50 D in the low to high myopia groups and -1.16 +/- 0.55 D in the extreme myopia group. At 6 months follow-up, uncorrected visual acuity was 20/20 or better in 73 eyes (54%) in the low to moderate myopia groups and 21 eyes (18%) in the high to extreme myopia groups. In the hyperopia group at 6 months follow-up, uncorrected visual acuity was 20/20 or better in 31 eyes (62%) and 20/40 or better in 41 eyes (82%). Only two eyes had a temporary loss of two or more lines of spectacle-corrected visual acuity due to corneal folds that were surgically treated. Six months after LASIK, no eye had lost any lines of best spectacle-corrected visual acuity in this series. CONCLUSIONS: Our modified LASIK nomogram with the 9.0 software of the LaserSight 200 excimer laser (with a larger and smoother ablation pattern) resulted in safe and effective outcomes for the treatment of low to high myopia, astigmatism, and hyperopia.

Adult↗

PubMedDate not supplied

Photorefractive keratectomy for myopia with the Meditec MEL 70G-Scan flying spot laser.

PURPOSE: To evaluate the efficacy, predictability, stability, and safety of the Meditec MEL 70G-Scan flying spot excimer laser. METHODS: One hundred thirty myopic eyes were treated with the Aesculap Meditec Mel 70G-Scan ArF flying spot excimer laser with photorefractive keratectomy (PRK). Patient groups: low myopia (Group 1) from -1.50 to -6.00 D (90 eyes), medium myopia (Group 2) from -6.10 to -9.00 D (31 eyes), high myopia (Group 3) from -9.10 to -14.00 D (9 eyes). RESULTS: At 12 months in the low myopia group, uncorrected visual acuity (UCVA) of 20/40 or better was achieved in 95.5% (86 eyes), 20/20 or better in 77.7% (70 eyes); 2.2% (two eyes) lost two or more lines of best spectacle-corrected visual acuity (BSCVA); 73.3% (66 eyes) were within +/-0.50 D of the target correction and 98.8% (89 eyes) were within +/-1.00 D. In the medium myopia group, UCVA of 20/40 or better was achieved in 74.2% (23 eyes), 20/20 or better in 25.8% (eight eyes); 3.2% (one eye) lost two lines, 61% (19 eyes) were within +/-0.50 D of desired correction and 83.8% (26 eyes) were within +/-1.00 D. In the high myopia group, UCVA of 20/40 or better was achieved in 22.2% (two eyes); 20/25 or better in 11.1% (one eye); none of the eyes achieved 20/20 UCVA; 22.2% (two eyes) lost two lines of BSCVA; 44.4% (four eyes) were within +/-0.50 D and 66.6% (six eyes) were within +/-1.00 D of the target correction. Refractive stability was achieved between 3 and 6 months. Increased intraocular pressure was detected overall in 7.69%. CONCLUSIONS: The results of predictability, safety, and efficacy in low and medium myopia with the Meditec MEL 70G-Scan flying spot excimer laser were good, but poorer predictability, regression, and a significant loss of BSCVA were observed in the high myopia group.

Adult↗

PubMed2000

Form deprivation myopia in mature common marmosets (Callithrix jacchus).

PURPOSE: Experimental manipulations of visual experience are known to affect the growth of the eye and the development of refractive state in a variety of species including human and nonhuman primates. For example, it is well established that visual form deprivation causes elongation of the eye and myopia. The effects of such manipulations have generally been examined in neonatal or juvenile animals. Whether adolescent common marmosets (a new world primate) are susceptible to form deprivation myopia was studied. METHODS: Five adolescent marmosets were used in this study. Monocular form deprivation was induced by lid closure for 12 to 20 weeks, starting between 299 and 315 days of age. The effects of deprivation were assessed with keratometry, A-scan ultrasonography, and cycloplegic refractions. Both eyes (treated and fellow control) were measured before lid-closure, at the end of the deprivation period, and several times over the following 8 to 12 weeks. RESULTS: Adolescent marmosets are susceptible to visual form deprivation myopia. The experimental eyes showed significant axial elongation and myopia relative to the fellow control eyes. These changes were smaller, however, than those observed in younger eyes deprived for comparable periods. Like juvenile animals, the adolescent marmosets did not show recovery from myopia over the period monitored. CONCLUSIONS: The period for susceptibility to form deprivation myopia in the marmoset monkey extends beyond the early developmental period when ocular growth is rapid and emmetropization normally takes place. Visual form deprivation in adolescent marmosets with adult-sized eyes results in increased ocular growth and myopia. These data suggest that visual factors may influence the growth and refractive development of the human eye after puberty and may be involved in late-onset myopia.

Animals↗

PubMed2000

Myopia: gene-environment interaction.

INTRODUCTION: Myopia has reached epidemic proportions in Japan, Hong Kong, Taiwan and Singapore. This review summarises the evidence for environmental and genetic factors as well as gene-environment interaction for myopia for both epidemiologic studies as well as animal models. METHODS: A literature review was conducted after a Medline search on articles on the genetic or environmental aetiology of myopia in animal or epidemiologic studies. Articles on the methodology of gene-environment studies were also reviewed. All articles reviewed were articles published in peer-reviewed journals. RESULTS: Cross-sectional studies have found a positive association between myopia and near work activity such as reading and writing. Likewise, laboratory research has shown that environmental factors such as visual deprivation may lead to the development of myopia in animals. While linkage studies in humans are currently being conducted to identify possible markers for myopia in the human genome, several neurotransmitters, modulators and growth factors that influence refractive development have already been identified in animal models that may help identify candidate genes. Epidemiologic studies have also evaluated the combined effects of hereditary factors, environmental factors and gene-environment interaction on myopia development. CONCLUSIONS: Both genes and environmental factors may be related to myopia. There are no conclusive studies at present, however, that identify the nature and extent of possible gene-environment interaction. Further linkage analysis, affected sib-pair studies, and family-based association studies may better identify the nature of gene-environment interaction.

Animals↗

PubMed2000

Stimulus deprivation myopia in human congenital ptosis: a preliminary report of 50 unilateral cases.

OBJECTIVE: To investigate the frequency of hyperopia and suspected stimulus deprivation myopia in human congenital ptosis. METHODS: Ametropia was evaluated in both eyes of 50 patients with congenital ptosis. The age at investigation was one year and older, average 6 years and 10 months. The amount of refraction was documented as the spherical equivalent (100% cycloplegia). Differences between the paired eyes of 1.0 dpt or more were defined as anisometropia. Statistical analysis was performed using the chi-square and sign tests. RESULTS: The frequency of myopia was lower (7/50: 14%) than that of hyperopia (43/50: 86%) in the ptotic eye (p<0.001). However, myopia occurred more often in the ptotic eye (7/50: 14%) than in the fellow eye (3/50: 6%, p>0.3). Myopic anisometropia was found only in the ptotic eye (5/50 vs. 0/50, p = 0.06), but was not more frequent than hyperopic anisometropia: (5/50 vs. 9/50, p>0.4). A covered center of the pupil in 27 out of 50 eyes was not associated significantly with myopia (2 of 27 versus 5 of 23, p>0.2). Altogether, we found a significantly higher rate of myopia <-1 dpt and hyperopia > 2 dpt: 10% vs. 1.4% and 40% vs. 10.2% (p<0.001) in comparison with normal school children. CONCLUSION: In summary, the following three findings were noted, of which the first two were expected and the third was not. 1. Compared with the normal population, there was an overall higher frequency of myopia in unilateral congenital ptosis. 2. There was a higher frequency of myopia in the ptotic than in the fellow eye. 3. Compared with the normal population, there was also a higher frequency of hyperopia. The clinical presentation of human congenital ptosis may be influenced by compensating head posture, strabismus, accommodation and biochemical effects, and the condition may therefore differ from the classical well-defined animal model of stimulus deprivation myopia.

Adolescent↗

PubMed2000

[Significance of inflammatory diseases of otorhinolaryngological organs in etiology and pathogenesis of myopia in the Air Forces flying personnel].

Complex ophthalmologic examination (visorefracto- and accommodometry) and study of disease structure were conducted in 1189 persons of flying staff. In the main group (persons with myopia) LOR-diseases were noticed 3.6 times more often than in those without myopia. In pilots with myopic refraction chronic inflammatory diseases of palatine tonsils: chronic compensated (35.5%) and decompensated (27%) tonsillitis occur 7-12 times more often than in control group. Investigation of visual function has revealed that in the group of persons without the history of chronic tonsillitis the least degree of myopia, the greatest visual acuity without correction, the least value of progress gradient and minimal decrease in indices of relative and absolute accommodation were observed. In persons after tonsillectomy the mentioned parameters of visual functions are close to the values obtained in pilots without the history of chronic tonsillitis; only accommodative functions were practically twice decreased. Chronic tonsillitis causes the greater degree of myopia and gradient of its progress and respectively more lower visual acuity and significant decrease in accommodation indices (P < 0.05). Also it has been detected that if myopia was diagnosed in a year or more after tonsillectomy then myopia and degree of visual function disorders respectively were minimal. If the operation was performed in a year or more after myopia detection the disorders in visual functions were more expressed and myopia reached significantly higher values (P < 0.05).

Aerospace Medicine↗

PubMed2000

Reducing the progression of myopia with atropine: a long term cohort study of Olmsted County students.

BACKGROUND: Myopia is an important public health problem because it is common and is associated with increased risk for chorioretinal degeneration, retinal detachment, and other vision- threatening abnormalities. In animals, ocular elongation and myopia progression can be lessened with atropine treatment. This study provides information about progression of myopia and atropine therapy for myopia in humans. METHODS: A total of 214 residents of Olmsted County, Minnesota (118 girls and 96 boys, median age, 11 years; range 6 to 15 years) received atropine for myopia from 1967 through 1974. Control subjects were matched by age, sex, refractive error, and date of baseline examination to 194 of those receiving atropine. Duration of treatment with atropine ranged from 18 weeks to 11.5 years (median 3.5 years). RESULTS: Median followup from initial to last refraction in the atropine group (11.7 years) was similar to that in the control group (12.4 years). Photophobia and blurred vision were frequently reported, but no serious adverse effects were associated with atropine therapy. Mean myopia progression during atropine treatment adjusted for age and refractive error (0.05 diopters per year) was significantly less than that among control subjects (0.36 diopters per year)(P<.001). Final refractions standardized to the age of 20 years showed a greater mean level of myopia in the control group (3.78 diopters) than in the atropine group (2.79 diopters) (P<.001). CONCLUSIONS: The data support the view that atropine therapy is associated with decreased progression of myopia and that beneficial effects remain after treatment has been discontinued.

Adolescent↗

PubMed2002

Baseline refractive and ocular component measures of children enrolled in the correction of myopia evaluation trial (COMET).

PURPOSE: To describe baseline refractive and ocular component measures in children with myopia enrolled in the Correction of Myopia Evaluation Trial (COMET). COMET is a multicenter, randomized clinical trial to evaluate whether progressive-addition lenses slow the progression of juvenile-onset myopia compared with single-vision lenses. METHODS: Four hundred sixty-nine children with myopia between -1.25 and -4.50 D spherical equivalent and without eye or systemic conditions known to affect refractive development were recruited from four geographically and ethnically diverse communities in the United States. Their ages were 6 to 11 years inclusive, and 52% were girls. The main outcome measure for the overall trial is progression of myopia determined by cycloplegic autorefraction after inducement of cycloplegia with 2 drops of 1% tropicamide. Axial length, the secondary outcome measure, was assessed by ultrasonography. The distance correction was determined by subjective methods before cycloplegia, with noncycloplegic autorefraction values as the starting point. RESULTS: Because data were similar in both eyes, they are reported for the right eye only. The mean spherical equivalent measured by cycloplegic autorefraction was -2.38 +/- 0.81 D. Young children had significantly less myopia than older children (P = 0.03), but the amount of myopia did not differ by gender or ethnicity. Mean axial dimensions were 4.0 +/- 0.2 mm (anterior chamber), 3.4 +/- 0.2 mm (lens), 16.8 +/- 0.7 mm (vitreous chamber), and 24.1 +/- 0.7 mm (axial length). Girls' eyes had significantly shorter axial length than boys' (P < 0.0001). Mean corneal radii were 7.73 +/- 0.25 mm (horizontal) and 7.59 +/- 0.24 mm (vertical). Ninety-five percent of the eyes had a ratio of axial length to corneal radius higher than 3.0. CONCLUSIONS: These baseline measures provide cross-sectional data on a large group of ethnically diverse children with myopia. Refractive and axial component dimensions are consistent with data in other studies showing that myopic eyes have longer vitreous chambers than emmetropic eyes. The measures reported herein will serve as a basis for examining changes that occur over a minimum of 3 years of follow-up of children enrolled in COMET.

Accommodation, Ocular↗

PubMed2002

[Morphological findings in progressive esotropia with high myopia].

PURPOSE: Esotropia with high myopia is due to elongation of the eyeball, which becomes too large to fit within the muscle cone. To demonstrate the elongation, we measured the size of the eyeballs. SUBJECTS AND METHODS: Five patients with esotropia with high myopia(myopic esotropia group), 8 patients with high myopia without esotropia(high myopia group), and 10 controls(control group) were examined. Using magnetic resonance imaging, we measured the outer axial length and the maximum transverse size of the eyeballs. RESULTS: The outer axial length(mean +/- standard deviation) was greater in the order of the myopic esotropia group(31.6 +/- 1.59 mm), the high myopia group(27.9 +/- 2.22 mm), and the control group(23.7 +/- 1.59 mm) (p < 0.01). The maximum transverse size was also greater in the order of the myopic esotropia group(25.0 +/- 0.99 mm), the high myopia group (24.9 +/- 1.27 mm), and the control group(23.1 +/- 1.38 mm). The outer axial length of the eyeballs in the myopic esotropia group was significantly longer than in the high myopia group and the control group, and the maximum transverse size was significantly longer than in the control group. CONCLUSIONS: The elongation of the eyeballs of the myopic esotropia group was demonstrated. A high incidence of esotropia may occur when the outer axial length of high myopia is longer than 30 mm.

Aged↗

PubMed2002

Myopia and incident cataract and cataract surgery: the blue mountains eye study.

PURPOSE: To assess whether an association exists between myopia and incident cataract and cataract surgery in an older population-based cohort study. METHODS: The Blue Mountains Eye Study examined 3654 participants aged 49 years or more during 1992 to 1994 and then 2334 (75.1%) of the survivors after 5 years. A history of using eyeglasses for clear distance vision was obtained. Objective refraction was performed with an autorefractor, followed by subjective refraction with a logarithm of minimum angle of resolution (logMAR) chart. Emmetropia was defined as a spherical equivalent refraction between +1 D and -1 D, hyperopia as more than +1 D, and myopia as less than -1 D. Slit lamp and retroillumination lens photographs were graded for presence of cortical, nuclear, or posterior subcapsular cataract, according to the Wisconsin Cataract Grading System. Generalized estimating equation models analyzed data by eye. RESULTS: There was a statistically significant association between high myopia (-6 D or less) and incident nuclear cataract (odds ratio [OR] 3.3, 95% confidence interval [CI] 1.5-7.4). Incident posterior subcapsular cataract was associated with any myopia (OR 2.1, 95% CI 1.0-4.8), moderate to high myopia (-3.5 D or less, OR 4.4, 95% CI 1.7-11.5), and use of distance glasses before age 20 (OR 3.0, 95% CI 1.0-9.3), after adjustment for multiple potential confounders, including severity of nuclear opacity. Incident cataract surgery was significantly associated with any myopia (OR 2.1, 95% CI 1.1-4.2) as well as moderate (-3.5 to more than -6D; OR 2.9, 1.2-7.3) and high myopia (OR 3.4, 95% CI 1.0-11.3). CONCLUSIONS: These epidemiologic data provide some evidence of an association between myopia and incident cataract and cataract surgery, after adjustment for multiple confounders and severity of nuclear opacity. These data support other cross-sectional and longitudinal population-based findings.

Aged↗

PubMed1999

[Study on the posterior vitreous detachment in patients with high myopia].

OBJECTIVE: To access the development of posterior vitreous detachment(PVD) related to age, axial length of the eye, vitreous changes as well as the myopic chorioretinal manifestation in patients with high myopia. METHODS: The vitreous status of 61 consecutive patients with high myopia(> or = -8.0 D and axial length > or = 26.0 mm) 110 eyes and 68 controls (< or = -3.0 D) 119 eyes were examined with biomicroscopic slit lamp and B-scan ultrasound. The myopic chorioretinal changes at the posterior pole were examined by indirect ophthalmoscope. The axial length of the eye was measured by A-scan ultrasound. The incidence of PVD was evaluated by Chi-square test. RESULTS: The incidence of PVD in patients with high myopia increased with age. Its overall incidence was significantly higher than that in the controls (78.2% vs 31.1%, P < 0.001). In addition, the onset of PVD in patients with high myopia occurred much earlier in age than that in the control group. Axial length was an important factor responsible for the development of PVD in patients with high myopia. The incidence of PVD and age were highly correlated (r = 0.9997, P < 0.05). Retinal detachment occurred in 5 eyes in the patients with high myopia. CONCLUSIONS: The results in the present study suggested that the incidence of PVD in patients with high myopia, increased with axial length of the eye and age. Vitreous changes are characteristic findings associated with high myopia, which was also involved in the development of PVD.

Adult↗

PubMedDate not supplied

[Choice of a scleroplasty method in progressive myopia in children].

Dynamic analysis of the results of sclera-fortifying interventions (scleroplasty and sclera-fortifying injection) in children aged 8 to 12 has demonstrated that in many cases myopia stabilized but temporarily after sclera fortification in children with progressive myopia. Repeated sclera-fortifying interventions reduced the rate of postoperative myopia progress approximately twofold, the myopia stabilization period lasting for 1 to 2 years; in some cases myopia progress ceased after a repeated intervention. In 67% of patients myopia on the second eye did not progress for 6 months after sclera-fortifying injection and for a year after scleroplasty on the first eye. Sclera fortification in the paired eye is advisable within these periods. Analysis of the results from the viewpoint of the general mechanisms of scleroplasty effect has lead the authors to a conclusion that sclera-fortifying therapy of children with high progressive myopia should be carried out in several stages. A system of sclera-fortifying treatment of progressive myopia has been developed, and the continuity of methods used for this purpose validated. Effects of this treatment scheme on refraction and status of the fundus oculi are estimated.

Age Factors↗

PubMed2006

[Displacement of the posterior part of the eyeball in myopia].

PURPOSE: The principal aim of this study was to investigate displacement of the posterior part of the eyeball within the muscle cone in myopic eyes, particularly in moderately myopic subjects as well as in high myopes. Secondly, the correlation of the amount of displacement and the outer axial length of the globe was studied. The direction of displacement was also examined to clarify whether the eyeball tends to shift toward a certain direction. METHODS: Seven patients with moderate myopia (moderate myopia group), fifteen patients with high myopia without esotropia (high myopia group), five patients with high myopia and esotropia (myopic esotropia group), and twenty-two controls (control group) were examined. Using magnetic resonance imaging, the outer axial length and the displacement of the posterior portion of the eyeball in the muscle cone were measured. In order to eliminate interindividual differences in the facial configuration, the coronal scanning was done perpendicularly to the orbital axis. The displacement was measured in a plane 4 mm anterior to the globe-optic nerve junction. The displacement was represented by the distance and direction of the globe center from the center of the muscle cone. RESULTS: In the moderate myopia group, there was no displacement of the posterior part of the eyeball in the muscle cone. It was the same as in the control group. But among the three groups, the displacement (mean standard deviation) was significantly greater in the myopic esotropia group (1.53 +/- 0.49 mm) and the high myopia group (0.94 +/- 0.52 mm) than in the control group (0.11 +/- 0.18 mm) (one way ANOVA and multiple comparison). The outer axial length and the distance of the displacement in all cases was significantly correlated (r = 0.87, p = 0.01). Moreover, the posterior part of the eyeball of the myopic esotropia group and the high myopia group was displaced superiorly and temporally. CONCLUSIONS: The posterior part of the eyeball of myopic eyes was displaced superotemporally in the muscle cone regardless of the presence of esotropia, and the amount of displacement was significantly correlated with the outer axial length. The more the eyeball expanded, the farther it was displaced. In the end, it was thought that the most elongated high myopic eyes would dislocate out of the muscle cone.

Adult↗

PubMed1985

Genetic and environmental effects on the development of myopia in Chinese twin children.

In order to assess the relative and interactive importance of genetic and environmental components on the development of myopia in Chinese school children aged from 10 to 15 years, a population-based sample of 361 same-sexed twin pairs recruited through stratified cluster sampling was studied. Zygosity of twin pairs was determined by Mendelian traits, red cell antigen systems, and continuous dermatoglyphic characteristics; while myopia was diagnosed by both objective and subjective techniques. Studying and reading habit was obtained from cotwins and their parents through a life style questionnaire. Age-sex-adjusted concordance rate derived from multiple regression equation was used in the analysis. Conventional comparison of intrapair concordance between monozygotic (MZ) and dizygotic (DZ) twins was used to assess the importance of a genetic component in the determining of myopia, and a significant genetic influence was observed. Environmental influence on myopia was evaluated through MZ cotwin method, and MZ cotwins with concordant studying and reading habits were significantly more concordant in myopia than those MZ cotwins with discordant habits. The possible effect of gene-environment interaction on myopia was explored, and concordance in myopia was found significantly associated with the interaction between zygosity and habit of studying and reading. These observations suggested that the impact of the environmental factor on the development of myopia may be influenced by genotype, and vice versa.

Adolescent↗

PubMed1995

Progression of myopia.

BACKGROUND: Myopia is an important public health problem because it is common and is associated with increased risk for chorioretinal degeneration, retinal detachment, and other vision-threatening abnormalities. In animals, ocular elongation and myopia progression can be lessened with atropine treatment. This study provides information about progression of myopia and atropine therapy for myopia in humans. METHODS: A total of 214 residents of Olmsted County, Minnesota (118 girls and 96 boys; median age, 11 years; range, 6 to 15 years) received atropine for myopia from 1967 through 1974. Control subjects were matched by age, sex, refractive error, and date of baseline examination to 194 of those receiving atropine. Duration of treatment with atropine ranged from 18 weeks to 11.5 years (median 3.5 years). RESULTS: Median follow-up from initial to last refraction in the atropine group (11.7 years) was similar to that in the control group (12.4 years). Photophobia and blurred vision were frequently reported, but no serious adverse effects were associated with atropine therapy. Mean myopia progression during atropine treatment adjusted for age and refractive error (0.05 diopters per year) was significantly less than that among control subjects (0.36 diopters per year) (P < .001). Final refractions standardized to the age of 20 years showed a greater mean level of myopia in the control group (3.78 diopters) than in the atropine group (2.79 diopters) (P < .001). CONCLUSIONS: The data support the view that atropine therapy is associated with decreased progression of myopia and that beneficial effects remain after treatment has been discontinued.

Adolescent↗

PubMed2005

Myopia and associated pathological complications.

Besides the direct economic and social burden of myopia, associated ocular complications may lead to substantial visual loss. In several population and clinic-based cohorts, case-control and cross-sectional studies, higher risks of posterior subcapsular cataract, cortical and nuclear cataract in myopic patients were reported. Patients with high myopia (spherical equivalent at least -6.0 D) are more susceptible to ocular abnormalities. The prevalent risks of glaucoma were higher in myopic adults, and risks of chorioretinal abnormalities such as retinal detachment, chorioretinal atrophy and lacquer cracks increased with severity of myopia and greater axial length. Myopic adults were more likely to have tilted, rotated, and larger discs as well as other optic disc abnormalities. Often, these studies support possible associations between myopia and specific ocular complications, but we cannot infer causality because of limitations in study methodology. The detection and treatment of possible pathological ocular complications is essential in the management of high myopia. The ocular risks associated with myopia should not be underestimated and there is a public health need to prevent the onset or progression of myopia.

Adolescent↗

PubMed1999

Prevalence and risk factors of myopia in Victoria, Australia.

OBJECTIVE: To determine the prevalence and risk factors of myopia in urban and rural Victoria, Australia. PARTICIPANTS AND METHODS: The Visual Impairment Project is a population-based prevalence study of eye disease in which both urban and rural adult populations were examined. Refractive data on the participants were collected using logMAR visual acuity, corrective lens measurement, and subjective refraction. All refractive error data were converted into spherical equivalent and myopia was defined at 2 levels: worse than -0.5 diopters (D) and worse than -1.00 D. RESULTS: A total of 3271 (83%) urban and 1473 (91%) rural residents were examined. The overall prevalence of myopia worse than -0.50 D in the population was 17% (95% confidence limit = 15.8%, 18.0%). Prevalence of myopia decreased from 24% in those aged 40 to 49 years to 12% in those aged 70 to 79 years, and then increased to 17% in people older than 80 years. The younger age groups also had higher usage of myopic corrective lenses throughout their lives than the older age groups, indicating an increased use of myopic corrective lenses in recent times. Myopia was found to be significantly higher in people with higher education levels (chi2 = 119.20, P < .001), in clerks and professionals (chi2 = 132.53, P < .001), in people born in southeast Asia (chi2 = 77.62, P < .001), and in people with higher degrees of nuclear opacity (chi2 = 55.26, P < .001). CONCLUSION: Myopia rates in the Visual Impairment Project generally decrease with age and use of myopic correction has increased in recent times. Myopia was significantly related to education level, occupation, country of birth, and nuclear opacity.

Adult↗

PubMed2002

Pirenzepine affects scleral metabolic changes in myopia through a non-toxic mechanism.

Whilst the precise mechanism regulating ocular growth is unknown, it has been shown that various pharmacological agents, including the muscarinic receptor antagonists, atropine and pirenzepine, are effective at preventing the development of myopia. A recent study, which demonstrated that muscarinic antagonists reduce the synthesis of glycosaminoglycans and DNA in chick sclera in vitro, led to the suggestion that such drugs may act directly on the sclera, possibly through a toxic mechanism. Accepted markers of scleral metabolism and cell viability were used in conjunction with a non-invasive, physiological method of ocular growth regulation to determine whether the selective muscarinic antagonist pirenzepine inhibits the development of myopia via toxicity to the sclera. Chicks were monocularly deprived (MD) of pattern vision and given daily intravitreal injections of either pirenzepine (700 microg) or saline vehicle into the deprived eye over 5 days. Unoccluded animals also received intravitreal injections of either pirenzepine or saline into one eye (n=6, all groups). The contralateral eye of all animals was left untreated for comparison. Optical and ocular biometric measures were collected on the final experimental day. Following in vivo delivery of [(35)S] labelled sulphate, levels of sulphate incorporation into scleral glycosaminoglycans were measured in proteinase K digests following selective precipitation with alcian blue dye. The DNA content was also assessed through luminescence spectrometry after binding to Hoechst 33258 dye. To allow comparison with an accepted non-invasive, physiological method of ocular growth regulation, myopia was prevented in additional groups of MD animals by allowing 3hr of unoccluded vision each day, over 5 days, before levels of sulphate incorporation were measured. Scleral DNA content, a marker of cell viability, was not significantly altered between treated and control eyes in any injected group. Relative levels of sulphate incorporation (% difference between treated and contralateral control eyes) were significantly lower in the cartilaginous sclera of pirenzepine-MD animals, compared to saline-MD controls (+35.9 +/- 10.1% vs +121.2 +/- 28.6%, P<0.05), after 2hr of incorporation. However, after 6hr incorporation, there was no significant difference in sulphate incorporation in the cartilaginous sclera between the two groups (+87.2 +/- 33.1% vs +111.0 +/- 14.4%, P=0.53). No significant change was found in the levels of glycosaminoglycan synthesis in the fibrous sclera of any pirenzepine treated group, when compared to the appropriate saline control. Relative patterns of sulphate incorporation, between treatment and control groups, were essentially identical at both time points examined, regardless of whether myopia was prevented through pirenzepine injection or periods of unoccluded vision. The present study shows that, at a dose of pirenzepine sufficient to prevent experimentally-induced axial myopia, glycosaminoglycan synthesis in the cartilaginous sclera was significantly reduced for a transient period following the injection. These pirenzepine-induced reductions in glycosaminoglycan synthesis were not caused by direct drug toxicity to scleral cells as these changes were reversible and no significant reduction in DNA content was observed in pirenzepine treated eyes. Similar patterns of scleral glycosaminoglycan synthesis changes were found following the provision of brief periods of unoccluded vision further demonstrating that pirenzepine is effective in myopia prevention via a non-toxic mechanism. Consequently, the prevention of myopia development in chicks, with either pirenzepine or brief periods of unoccluded vision, is associated with the transient modulation of scleral glycosaminoglycan synthesis in the cartilaginous sclera.

Animals↗