The epidemiology of myopia

Morphological characteristics of the optic nerve head and impacts on longitudinal change in macular choroidal thickness during myopia progression

PURPOSE

The aim of this study was to investigate the association between morphological characteristics of Bruch's membrane opening distance (BMOD), border length (BL), border tissue angle (BTA), peripapillary atrophy (PPA) as well as axial length (AL) and incident decreased macular choroidal thickness (mChT) in young healthy myopic eyes.

METHODS

A total of 323 participants aged 17-30 years were included in the current 2-year longitudinal study. Each participant underwent detailed ocular examinations at baseline and follow-up. Data of AL, refraction error, PPA area, BMOD, BL, BTA and mChT were measured individually. Incident decreased mChT was defined as follow-up mChT of participants decreased into the lowest quartile of baseline mChT.

RESULTS

Subjects with longer AL, longer BMOD were more likely to have incident decreased mChT (odds ratio [OR], 1.56; 2.09, respectively, per 1 Z-score increment), whereas larger BTA was less likely to develop decreased mChT (odds ratio [OR], 0.51, per 1 Z-score increment). The area under the receiver operating curve (AUROC) of basic risk model for incident decreased mChT was 0.6284. After adding BMOD, BTA and AL separately to the basic risk model, the AUROC of the combination could reach 0.6967, 0.6944 and 0.7383, respectively. After combining BMOD, BTA and AL to the basic model, the AUROC of the combination showed the highest AUROC of 0.7608.

CONCLUSIONS

Bruch's membrane opening distance and AL are significant risk factors for incident decreased mChT, whereas BTA played protective role in the deterioration of mChT. In addition, a combination of BMOD, BTA and AL could serve as earlier predictors of the attenuation of mChT in myopia progression.

The Association between Myopia and Primary Open-Angle Glaucoma: A Systematic Review and Meta-Analysis

BACKGROUND

Previous studies identified myopia as a risk factor for primary open-angle glaucoma (POAG). However, recent studies have shown different results, the definitive relationship between myopia and POAG remains controversial.

OBJECTIVES

To investigate the relationship between myopia and POAG.

METHODS

Published articles were searched from PubMed, Embase, and Scopus databases between 1970 and 2020. A pooled analysis of the ORs was performed using a random-effects model.

RESULTS

Data on the association between myopia and POAG, were obtained from 16 cross sectional studies, and the pooled OR was 2.26 (95% confidence interval [CI], 1.77 - 2.89, P < 0.001) in random effects model (I2 = 86%; P < 0.01). For the relationship of myopia and POAG progression, data from seven longitudinal cohort studies were included and the pooled OR was 0.85 (95% CI, 0.73 - 0.99, P = 0.042) in the random-effects model (I2 = 88%; P < 0.01).

CONCLUSION

Our findings demonstrated that myopia may be a risk factor associated with POAG and a possible protective factor for POAG progression. It may due to myopia with the presence of a lamina cribrosa defect slow down the visual field loss also POAG progression, further research for underlying mechanisms is still needed.

Myopia-correcting lenses decrease eye fatigue in a visual search task for both adolescents and adults

The steady, world-wide increase in myopia prevalence in children over the past decades has raised concerns. As an early intervention for axial-length-related myopia, correcting lenses have been developed (such as Defocus Incorporated Multiple Segment (DIMS) lenses), which have been shown to be effective in slowing myopia progression. Beyond this direct effect, however, it is not known whether such lenses also affect other aspects important to the wearer, such as eye fatigue, and how such effects may differ across age, as these lenses so far are typically only tested with adolescents. In the present work, we therefore investigated perceived fatigue levels according to lens type (normal vs DIMS) and age (adolescents vs adults) in a demanding visual search task ("Finding Wally") at two difficulty levels (easy vs difficult). Whereas age and difficulty did not result in significant differences in eye fatigue, we found a clear reduction of fatigue levels in both age groups when wearing the correcting lenses. Hence, the additional accommodation of these lens types may result in less strain in a task requiring sustained eye movements at near viewing distances.

Do rectus muscle parameters vary between emmetropes and myopes?

PURPOSE

This study investigated the thickness, area, and insertion site of the medial (MR) and lateral (LR) rectus muscles in individuals with emmetropia and different degrees of myopia.

METHODS

Swept-source optical coherence tomography images of the MR and LR muscles in 80 participants including emmetropes (spherical equivalent refractive error [SER] ±0.50 D, N = 14) and myopes (≤ -0.75 D, N = 66), were analysed. Custom-designed, semi-automated software was used to measure parameters such as insertion distance from limbus, muscle thickness at every 1 mm interval to 3 mm periphery and muscle area from insertion site to 3 mm.

RESULTS

The median (Q1, Q3) SER error and axial length were -6.00 D (-13.25, -2.12) and 25.78 mm (23.78, 28.61), respectively. The MR was significantly thinner (mean ± SE: 137.7 ± 8.9 vs. 159.7 ± 8.9 µm, p < 0.01) and occupied less area than the LR (0.35 ± 0.01 vs. 0.42 ± 0.01 mm² , respectively, p < 0.01). The thickness of the MR gradually increased from the insertion site to a 3 mm peripheral eccentric location (106.5 3.8 µm at 1 mm, 135.5 ± 4.5 µm at 2 mm and 156.1 ± 5.9 µm at 3 mm, p < 0.01). The overall median thickness of the MR was significantly less in myopes (129 µm [111.5, 152.2]) than emmetropes (158.1 [134.3, 167.7] µm, p = 0.03). However, no such trend was seen in the LR muscle. Muscle area and insertion distance were not different between emmetropes and myopes in both horizontal rectus muscles.

CONCLUSION

Unlike the LR, the parameters of the MR (thin and occupying less area) show significant association with myopia. While the key finding of this study indicates the possible association of MR parameters with myopia, the clinical relevance of this finding and its role in myopiogenesis/progression needs to be investigated further.

Genetic Association Study Revealed Three Loci Were Associated Risk of Myopia Among Minors

Background

Myopia has raised a predominant public concern among minors. A recent genome-wide association study (GWAS) identified six novel loci in Asian adults. Whether these genetic loci works for myopia in minors remains unknown and worthy of exploration.

Methods

In order to validate the findings, here we performed a case-control study (600 myopia minors, 110 high myopia (HM) minors, and 800 non-myopia minors as controls) utilizing the TaqMan single nucleotide polymorphism (SNP) genotyping assays. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) was adopted.

Results

The median ages in controls, myopia, and HM were 15.1, 15.0, and 15.1, respectively, while the means ± standard deviations for them were 0.32±0.41, - 3.2 ±1.6, and −9.8±2.2, respectively. We found rs2246661 (allelic OR: 1.29; 95% CI: 1.09–1.52; P =0.003), rs74633073 (allelic OR: 1.41; 95% CI: 1.12–1.78; P =0.004), and rs76903431 (allelic OR: 1.42; 95% CI: 1.11–1.81; P =0.005) were significantly associated with increased risk of myopia. Rs2246661 was also significantly associated with increased risk of HM in minors (OR: 1.37; 95% CI: 1.02–1.84; P =0.035).

Conclusion

We identified three loci contributed to myopia in minors and these findings gave new insight into the genetic susceptibility mechanisms of myopia at the molecular level.

Myopic progression and dark focus variation in optometric students during the first academic year

BACKGROUND

The aim of this research was to investigate the change in refractive error (RE) of optometric students during their first academic year and whether these changes relate to changes in their dark focus (DF).

METHOD

The RE and DF of 64 students were measured objectively every three months during the first academic year, a total of four times, using a Canon R-1 infrared optometer. Thirty-five of the 64 students had an additional RE and DF measurement three weeks immediately after their Summer vacation. Students completed a survey regarding the near work demands they experienced during the Winter break and the teaching semesters.

RESULTS

Over nine months, the average RE of the students changed significantly from -2.22 +/- 1.93 (SD) D to -2.50 +/- 2.05 D (p = 0.0002). The rate of myopic progression averaged -0.37 dioptres per year. Inclusion of measurements taken on 35 students immediately after the Summer vacation showed that their change in RE during the Summer vacation was not significant (p = 0.79). For these subjects, the DF measured immediately after the vacation was significantly lower than the DF measured before the vacation (p = 0.007). The reduction in the DF after the vacations corresponded to a period of relative myopic stability in these subjects.

CONCLUSIONS

The results of this study suggest that optometric students performing extensive near work are at risk of developing myopia. The variation of their DF values indicates the changing demand for near work during different periods of the year. After Winter and Summer vacations, the DF was lower and the myopic progression was suspended. These findings further support the notion that myopic progression is related to high near work demands and suggest that this progression can be slowed by a period of reduced near work, for example, vacation periods.

Prevalence of myopia among secondary school students in Welkite town: South-Western Ethiopia

BACKGROUND

Refractive error, especially myopia, is the most common eye disorder in the world and a significant cause of correctable visual impairment. The aim of this study was to assess the prevalence of myopia among secondary school students in Welkite town, South-Western Ethiopia.

METHODS

A school based cross sectional study was carried out among secondary school students of 13 to 26 years of age. The students were selected using a multi stage-stratified cluster sampling technique from four secondary schools. The students' socioeconomic background, usage of eyeglasses and parental myopia was assessed by a questionnaire before visual acuity assessment. Students with visual acuity of less than or equal to 6/12 in the worse eye, who showed vision improvement with pinhole, underwent non-cycloplegic retinoscopy and subjective refraction. Myopia was defined as a spherical equivalent of less than or equal to - 0.50 diopters. Logistic regression was used to see the association of myopia with age, sex, grade level, ethnicity, parental history of myopia and severity.

RESULTS

A total of 1271 students with a response rate of 89.4% were evaluated. The mean age was 16.56+ 1.51 years. Eighty three students were identified to have myopic refractive error making the prevalence of 6.5% (95% CI: 5.30, 8.02). Of 648 females, 50 (7.7%) had myopia while 33 (5.3%) of 623 males had myopia making females relative risk to be 1.5 times that of males. From the total students diagnosed to have refractive error (n = 92), myopia constituted 83/92 (90.2%) of the students indicating that it is the commonest type of refractive error found amongst secondary school students. Only 36.1% of students with myopia wore eyeglasses when they attended the survey. Myopia was more common among older age group 17-21 years (OR: 1.54 95% CI 0.986-2.415) and higher grade level 11-12 (OR: 1.14 95% CI 0.706-1.847).

CONCLUSIONS

The prevalence of myopia is high in our study. Attention to the correction of myopia in secondary schools students of Welkite town using eyeglasses can prevent a major proportion of visual impairment.

Optical mechanisms regulating emmetropisation and refractive errors: evidence from animal models

Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non-human primates, tree shrews, guinea pigs, and mice. Extensive research on optical, biochemical, and environmental mechanisms contributing to refractive error development in animal models has provided insights into eye growth in humans. Importantly, animal models have taught us that eye growth is locally controlled within the eye, and can be influenced by the visual environment. This review will focus on information gained from animal studies regarding the role of optical mechanisms in guiding eye growth, and how these investigations have inspired studies in humans. We will first discuss how researchers came to understand that emmetropisation is guided by visual feedback, and how this can be manipulated by form-deprivation and lens-induced defocus to induce refractive errors in animal models. We will then discuss various aspects of accommodation that have been implicated in refractive error development, including accommodative microfluctuations and accommodative lag. Next, the impact of higher order aberrations and peripheral defocus will be discussed. Lastly, recent evidence suggesting that the spectral and temporal properties of light influence eye growth, and how this might be leveraged to treat myopia in children, will be presented. Taken together, these findings from animal models have significantly advanced our knowledge about the optical mechanisms contributing to eye growth in humans, and will continue to contribute to the development of novel and effective treatment options for slowing myopia progression in children.

Defocused Image Changes Signaling of Ganglion Cells in the Mouse Retina

Myopia is a substantial public health problem worldwide. Although it is known that defocused images alter eye growth and refraction, their effects on retinal ganglion cell (RGC) signaling that lead to either emmetropization or refractive errors have remained elusive. This study aimed to determine if defocused images had an effect on signaling of RGCs in the mouse retina. ON and OFF alpha RGCs and ON-OFF RGCs were recorded from adult C57BL/6J wild-type mice. A mono green organic light-emitting display presented images generated by PsychoPy. The defocused images were projected on the retina under a microscope. Dark-adapted mouse RGCs were recorded under different powers of projected defocused images on the retina. Compared with focused images, defocused images showed a significantly decreased probability of spikes. More than half of OFF transient RGCs and ON sustained RGCs showed disparity in responses to the magnitude of plus and minus optical defocus (although remained RGCs we tested exhibited similar response to both types of defocus). ON and OFF units of ON-OFF RGCs also responded differently in the probability of spikes to defocused images and spatial frequency images. After application of a gap junction blocker, the probability of spikes of RGCs decreased with the presence of optical defocused image. At the same time, the RGCs also showed increased background noise. Therefore, defocused images changed the signaling of some ON and OFF alpha RGCs and ON-OFF RGCs in the mouse retina. The process may be the first step in the induction of myopia development. It appears that gap junctions also play a key role in this process.

Eyesight: a study of the staff of a dental school

Objectives/Aims:

The aim was to investigate the vision of all 90 dentally qualified staff at a dental school.

Materials and Methods:

Ethical approval was obtained and a questionnaire-based survey conducted. Data were screened and analysed using Stata 13.1. The χ² and Fisher’s Exact tests were used to test for significance with an alpha level of 0.05.

Results:

The participation rate was 95.6%. Most of the teachers (92%) considered their eyesight was satisfactory to practice dentistry. Of the 97% who had been tested at some stage, 15% had their eye examination due to sight deterioration with 22% needing correction. Almost two-thirds were myopic and a third were hyperopic. Forty-nine per cent wore spectacles only, with about a quarter of this group alternating between spectacles and contact lenses. Of those with corrected vision, 80% followed their optometrist’s recall advice. Four participants reported that they were colour blind. While 4% had had laser-eye surgery, a further 27% were interested in this. Magnification was used by 72% with no significant differences between genders, age of staff member, place of qualification or registration status. Most of the staff (81%) thought that screening of dental student’s eyesight should be mandatory, and regular eye examinations as a condition of dental practice was supported by 67%.

Discussion:

The number of teachers reporting recent vision tests was encouraging; nevertheless, a worrying 8% surveyed were unsure if their eyesight was satisfactory for work. The commonest vision problem was myopia, with almost half of the teachers wearing spectacles. It is clear that visual standards for dentistry would be helpful. Magnification use was high, with many non-users indicating their intention to buy loupes.

Conclusions:

Within the limits of this study the teachers were conscientious regarding their eye care, irrespective of their training and age. There was strong support for the mandatory testing of vision for all dentists and especially dental students.

Prevalence and Characteristics of Myopic Degeneration in an Adult Chinese American Population: The Chinese American Eye Study

PURPOSE

To characterize and provide population-based prevalence estimates of myopic degeneration (MD) among Chinese Americans, the fastest-growing minority population in the United States in the last decade.

DESIGN

Population-based, cross-sectional study.

METHODS

A total of 1523 Chinese-American adults with myopia, aged 50 years and older, residing in the city of Monterey Park, California, underwent an interview and comprehensive eye examination, including subjective and objective refraction and stereoscopic fundus photography. For each participant, the eye with the worse myopic refractive error was included in this analysis. MD was assessed in a masked manner by an expert grader.

RESULTS

The prevalence of any MD was 44.9% among myopic subjects, based on the presence of any degenerative lesion secondary to myopia. The prevalence was 32.2% when MD was defined by a modified version of the Meta-Analysis for Pathologic Myopia. The prevalence of specific lesions included tessellation (31.7%), tilted disc (28.1%), peripapillary atrophy (7.0%), staphyloma (5.7%), diffuse atrophy (6.4%), lacquer cracks (2.6%), intrachoroidal cavitation (2.2%), patchy atrophy (0.9%), and end-stage MD (0.2%). The prevalence of MD was higher among older myopic subjects and among participants with more severe myopia and longer axial length (P < .001).

CONCLUSIONS

These data provide the first population-based estimates of MD in Chinese Americans and indicate that a high proportion of Chinese Americans might be at risk for MD and associated visual complications. Prevalence of MD in this cohort of Chinese Americans was higher than that observed in other East Asian populations and in people of other ethnicities.

Effect of Orthokeratology on myopia progression: twelve-year results of a retrospective cohort study

BACKGROUND

Several studies reported the efficacy of orthokeratology for myopia control. Somehow, there is limited publication with follow-up longer than 3 years. This study aims to research whether overnight orthokeratology influences the progression rate of the manifest refractive error of myopic children in a longer follow-up period (up to 12 years). And if changes in progression rate are found, to investigate the relationship between refractive changes and different baseline factors, including refraction error, wearing age and lens replacement frequency. In addition, this study collects long-term safety profile of overnight orthokeratology.

METHODS

This is a retrospective study of sixty-six school-age children who received overnight orthokeratology correction between January 1998 and December 2013. Thirty-six subjects whose baseline age and refractive error matched with those in the orthokeratology group were selected to form control group. These subjects were followed up at least for 12 months. Manifest refractions, cycloplegic refractions, uncorrected and best-corrected visual acuities, power vector of astigmatism, corneal curvature, and lens replacement frequency were obtained for analysis.

RESULTS

Data of 203 eyes were derived from 66 orthokeratology subjects (31 males and 35 females) and 36 control subjects (22 males and 14 females) enrolled in this study. Their wearing ages ranged from 7 years to 16 years (mean ± SE, 11.72 ± 0.18 years). The follow-up time ranged from 1 year to 13 years (mean ± SE, 6.32 ± 0.15 years). At baseline, their myopia ranged from -0.5 D to -8.0 D (mean ± SE, -3.70 ± 0.12 D), and astigmatism ranged from 0 D to -3.0 D (mean ± SE, -0.55 ± 0.05 D). Comparing with control group, orthokeratology group had a significantly (p < 0.001) lower trend of refractive error change during the follow-up periods. According to the analysis results of GEE model, greater power of astigmatism was found to be associated with increased change of refractive error during follow-up years.

CONCLUSIONS

Overnight orthokeratology was effective in slowing myopia progression over a twelve-year follow-up period and demonstrated a clinically acceptable safety profile. Initial higher astigmatism power was found to be associated with increased change of refractive error during follow-up years.

Evidence for the need for vision screening of school children in Turkey

BACKGROUND

In many countries, access to general health and eye care is related to an individual's socioeconomic status (SES). We aimed to examine the prevalence of oculo-visual disorders in children in Istanbul Turkey, drawn from schools at SES extremes but geographically nearby.

METHODS

Three school-based vision screenings (presenting distance visual acuity, cover test, eye assessment history, colour vision, gross stereopsis and non-cycloplegic autorefraction) were conducted on 81% of a potential 1014 primary-school children aged 4-10 years from two private (high SES) schools and a nearby government (low SES) school in central Istanbul. Prevalence of refractive errors and school-based differences were analysed using parametric statistics (ANOVA). The remaining oculo-visual aspects were compared using non-parametric tests.

RESULTS

Of the 823 children with mean age 6.7 ± 2.2 years, approximately 10% were referred for a full eye examination (8.2% and 16.3% of private/government schools respectively). Vision had not been previously examined in nearly 22% of private school children and 65% of government school children. Of all children, 94.5% were able to accurately identify the 6/9.5 [LogMAR 0.2] line of letters/shapes with each eye and 86.6% the 6/6 line [LogMAR 0], while 7.9% presented wearing spectacles, 3.8% had impaired colour vision, 1.5% had grossly impaired stereo-vision, 1.5% exhibited strabismus, 1.8% were suspected to have amblyopia and 0.5% had reduced acuity of likely organic origin. Of the 804 without strabismus, amblyopia or organic conditions, 6.0% were myopic ≤ - 0.50DS, 0.6% hyperopic ≥ + 2.00DS, 7.7% astigmatic ≥1.00 DC and 6.2% anisometropic ≥1.00DS.

CONCLUSIONS

The results highlight the need for general vision screenings for all children prior to school entry given the varied and different pattern of visual problems associated with lifestyle differences in two populations raised in the same urban locale but drawn from different socioeconomic backgrounds.

Heritability of defects of far vision in young adults — a twin study

Heritability of defects of far vision in young adults — a twin study. J. Teikari, J. Kaprio, M. Koskenvuo and J. O'Donnel (University of Helsinki, Department of Public Health, Hartmaninkatu 3, SF-00290 Helsinki, Finland).

A questionnaire to study defects in far vision in the Finnish Twin Cohort Study was sent to 600 twin pairs of 30 and 31 years of age divided equally by gender and zygosity. An excess in female prevalence of defects in far vision was observed (p < 0.001). Validation of the questionnaire method to assess negative spherical equivalent of refraction was performed by asking the twins to send their last prescription for glasses. Accuracy of the questionnaire method to detect a defect in far vision was tested using a subsample of cases where actual refraction obtained from the prescription for glasses was available. This actual refraction value was compared with the individuals answers to the questions of far vision. Of the subjects 5.5% were false negatives and 1.8% of the individuals were false positives. In 152 pairs one or both twins had a defect in far vision. Under a threshold liability model, the proportion of total (phenotypic) variance in liability attributable to additive genetic effects was 0.91 in this twin data, while no evidence for effects due to dominance was found.

Controlling myopia progression in children and adolescents

Myopia is a common disorder, affecting approximately one-third of the US population and over 90% of the population in some East Asian countries. High amounts of myopia are associated with an increased risk of sight-threatening problems, such as retinal detachment, choroidal degeneration, cataracts, and glaucoma. Slowing the progression of myopia could potentially benefit millions of children in the USA. To date, few strategies used for myopia control have proven to be effective. Treatment options such as undercorrection of myopia, gas permeable contact lenses, and bifocal or multifocal spectacles have all been proven to be ineffective for myopia control, although one recent randomized clinical trial using executive top bifocal spectacles on children with progressive myopia has shown to decrease the progression to nearly half of the control subjects. The most effective methods are the use of orthokeratology contact lenses, soft bifocal contact lenses, and topical pharmaceutical agents such as atropine or pirenzepine. Although none of these modalities are US Food and Drug Administration-approved to slow myopia progression, they have been shown to slow the progression by approximately 50% with few risks. Both orthokeratology and soft bifocal contact lenses have shown to slow myopia progression by slightly less than 50% in most studies. Parents and eye care practitioners should work together to determine which modality may be best suited for a particular child. Topical pharmaceutical agents such as anti-muscarinic eye drops typically lead to light sensitivity and poor near vision. The most effective myopia control is provided by atropine, but is rarely prescribed due to the side effects. Pirenzepine provides myopia control with little light sensitivity and few near-vision problems, but it is not yet commercially available as an eye drop or ointment. Several studies have shown that lower concentrations of atropine slow the progression of myopia control with fewer side effects than 1% atropine. While the progression of myopic refractive error is slowed with lower concentration of atropine, the growth of the eye is not, indicating a potentially reversible form of myopia control that may diminish after discontinuation of the eye drops. This review provides an overview of the myopia control information available in the literature and raises questions that remain unanswered, so that eye care practitioners and parents can potentially learn the methods that may ultimately improve a child’s quality of life or lower the risk of sight-threatening complications.

Analysis of the volumetric relationship among human ocular, orbital and fronto-occipital cortical morphology

Recent research on the visual system has focused on investigating the relationship among eye (ocular), orbital, and visual cortical anatomy in humans. This issue is relevant in evolutionary and medical fields. In terms of evolution, only in modern humans and Neandertals are the orbits positioned beneath the frontal lobes, with consequent structural constraints. In terms of medicine, such constraints can be associated with minor deformation of the eye, vision defects, and patterns of integration among these features, and in association with the frontal lobes, are important to consider in reconstructive surgery. Further study is therefore necessary to establish how these variables are related, and to what extent ocular size is associated with orbital and cerebral cortical volumes. Relationships among these anatomical components were investigated using magnetic resonance images from a large sample of 83 individuals, which also included each subject's body height, age, sex, and uncorrected visual acuity score. Occipital and frontal gyri volumes were calculated using two different cortical parcellation tools in order to provide a better understanding of how the eye and orbit vary in relation to visual cortical gyri, and frontal cortical gyri which are not directly related to visual processing. Results indicated that ocular and orbital volumes were weakly correlated, and that eye volume explains only a small proportion of the variance in orbital volume. Ocular and orbital volumes were also found to be equally and, in most cases, more highly correlated with five frontal lobe gyri than with occipital lobe gyri associated with V1, V2, and V3 of the visual cortex. Additionally, after accounting for age and sex variation, the relationship between ocular and total visual cortical volume was no longer statistically significant, but remained significantly related to total frontal lobe volume. The relationship between orbital and visual cortical volumes remained significant for a number of occipital lobe gyri even after accounting for these cofactors, but was again found to be more highly correlated with the frontal cortex than with the occipital cortex. These results indicate that eye volume explains only a small amount of variation in orbital and visual cortical volume, and that the eye and orbit are generally more structurally associated with the frontal lobes than they are functionally associated with the visual cortex of the occipital lobes. Results also demonstrate that these components of the visual system are highly complex and influenced by a multitude of factors in humans.

Fluorescein angiography and optical coherence tomography in myopic choroidal neovascularization

PURPOSE

To assess intra/inter-observer agreement, and diagnostic capabilities of a color fundus photograph, fundus fluorescein angiography (FFA), and spectral domain optical coherence tomography (SD-OCT) in making a diagnosis of myopic choroidal neovascularization (CNV).

PATIENTS AND METHODS

Two masked observers evaluated FFA and SD-OCT images to identify the presence of myopic CNV in 80 high-myopic eyes of 57 patients. A third masked observer identified CNV on a color fundus photo. Presence of myopic CNV on a fundus photo was defined as presence of subretinal hemorrhage, thickening of the retina and/or visible membrane at the macula. Presence of myopic CNV on FFA was defined as hyperfluorescence in the early phase with increase in intensity and size in the late phase; presence of a large irregular lesion; and hypofluorsescence due to subretinal hemorrhage. Myopic CNV on SD-OCT was defined as the hyper-reflective lesion with or without intraretinal fluid or subretinal fluid with retinal thickening.

RESULTS

Intraobserver repeatability on FFA and SD-OCT was 0.54 and 0.44, respectively. Agreement (kappa) between FFA and SD-OCT was 0.38 and 0.3, respectively. Among 34 eyes, which had the presence of CNV on a color fundus photo, CNV was diagnosed in 18 (53%) eyes on FFA and in 20 (58.8%) eyes on SD-OCT. Sensitivity and specificity of FFA was 47 and 80.4%, respectively, and that of SD-OCT was 58.8 and 86.9%, respectively.

CONCLUSION

Repeatability and reproducibility for diagnosis of myopic CNV was better with FFA compared with SD-OCT; however, agreement is very poor between FFA and SD-OCT. SD-OCT is comparatively a better tool to rule out presence of myopic CNV.

Choroidal thickness in relation to sex, age, refractive error, and axial length in healthy Turkish subjects

The aim of this study was to investigate the association between choroidal thickness (CT) and sex, age, refractive error (RE), and axial length in healthy subjects. This is a study of 154 eyes in 154 healthy subjects. CT measurements were performed by the same experienced technician using a spectral domain optical coherence tomography device. CT was measured perpendicularly from the outer edge of the retinal pigment epithelium to the choroid-sclera boundary at the fovea and at six more points which are located at, respectively, 500 µm nasal to the fovea, 1,000 µm nasal to the fovea, and 1,500 μm nasal to the fovea, 500 μm temporal to the fovea, 1,000 μm temporal to the fovea, and 1,500 μm temporal to the fovea. The RE was measured by autorefractometry, and the axial length was measured by interferometry. Statistical analysis was performed to evaluate CT at each location, and to the correlations of CT with sex, age, RE, and axial length. The mean subfoveal CT was 265.86 ± 60.32 µm, the mean age was 49.01 ± 19.19 years, the mean RE was -0.17 ± 1.20 diopters (D), and the mean axial length was 23.39 ± 0.76 mm. CT profile indicated that the choroid was thicker at the fovea than at temporal and nasal locations. Univariable linear regression analysis showed that subfoveal CT decreased 3.14 µm for each year of age and decreased 79.33 µm for each mm of axial length (P = 0.000, R(2) = 0.249; P = 0.000, R(2) = 0.487, respectively). In a similar analysis, subfoveal CT was found to decrease by 50.24 µm/D myopia-shifted change in refraction (P = 0.000, R (2) = 0.201). The subfoveal choroid was 99.16 µm (39.22 %) thicker in men than women when adjusting for age and axial length (P = 0.000, R(2) = 0.249). CT decreases with increasing myopia, age, and axial length. Men had thicker choroid than women, and CT varies depending on location.

Relation between near work and myopia progression in student population

AIM

To determine relation between near work and myopia progression in student population. Causes of myopia occurrence are not sufficiently explained.

METHODS

This retrospective-prospective, descriptive research included 100 students with verified myopia up to -3 Dsph. Ophthalmological examination and measurement diopter-hours variable (Dh) were done twice, in the period from January 2011 until January 2012.

RESULTS

A multivariate regression analysis of impact on the difference of distance visual acuity without correction to the right and left eye and difference of automatic computer refractometry in cycloplegia of both eyes indicates that, diopter-hours variable (Dh) had statistically significant impact on increase of distance visual acuity difference (right eye OR: I measurement-Dh 1.489, II measurement-Dh 1.544, p<0.05; left eye OR: I measurement-Dh 1.602, II measurement-Dh 1.538, p<0.05) and automatic computer refractometry in cycloplegia (right eye OR: I measurement 1.361, II measurement 1.493, p<0.05; left eye OR: I measurement 0.931, II measurement 1.019, p<0.05) during both measurements.

CONCLUSION

Near work cause the increase of myopia. This research opened a perspective for other researches on the impact of near work on myopia.

The Cambridge Anti-myopia Study: variables associated with myopia progression

PURPOSE

To identify variables associated with myopia progression and to identify any interaction between accommodative function, myopia progression, age, and treatment effect in the Cambridge Anti-Myopia Study.

METHODS

Contact lenses were used to improve static accommodation by altering ocular spherical aberration, and vision training was performed to improve dynamic accommodation. One hundred forty-two subjects, aged 14-21 years, were recruited who had a minimum of -0.75D of myopia. Subjects were assigned to contact lens treatment only, vision training only, contact lens treatment and vision training, or control group. Spherical aberration, lag of accommodation, accommodative convergence/accommodation (AC/A) ratio, accommodative facility, ocular biometry, and refractive error were measured at regular intervals throughout the 2-year trial.

RESULTS

Ninety-five subjects completed the 24-month trial period. There was no significant difference in myopia progression between the four treatment groups at 24 months. Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. There was a significant treatment effect at 12 months in the contact lens treatment group in younger subjects, based on a median split, aged under 16.9 years (p = 0.005). This treatment effect was not maintained over the second year of the trial. Younger subjects experienced a greater reduction in lag of accommodation with the treatment contact lens at 3 months (p = 0.03), compared to older contact lens treatment and control groups. There was no interaction between AC/A ratio and contact lens treatment effect.

CONCLUSIONS

Age, lag of accommodation, and AC/A ratio were significantly associated with myopia progression. Although there was no significant treatment effect at 24 months, an interaction between age and contact lens treatment suggests younger subjects may be more amenable, at least in the short term, to alteration of the visual system using optical treatments.

Epidemiology of myopia

Myopia is one of the most prevalent disorders of the eye. Higher myopia is associated with comorbidities that increase risks of severe and irreversible loss of vision, such as retinal detachment, subretinal neovascularization, dense cataract, and glaucoma. In recent years, reports from population-based prevalence studies carried out in various geographical areas now give a clear picture of the current distribution of refractive error. The scarcity of data from well-designed longitudinal cohort studies is still yet to be addressed. These studies have confirmed the previous data indicating that prevalence of refractive error varies according to ethnicity and geographic regions, and also point to an increase in myopia prevalence over the past half-century. The problem is particularly pronounced in affluent, industrialised areas of East Asia. Environmental risk factors for myopia related to socioeconomic status and lifestyle have been identified. The past decade has seen a greater understanding of the molecular biological mechanisms that determine refractive error, giving further support to the belief that myopia is the result of a complex interaction between genetic predisposition and environmental exposures. This review summarizes data on the prevalence, incidence, progression, associations, risk factors, and impact from recent epidemiological studies on myopia.

The Awareness of Doctoral-Level Professions Among Entering College Students

Purpose

The purpose of this study was to survey entering college students' awareness of the profession of audiology, as well as to compare the students' awareness of audiology to their awareness of roles in 2 other doctoral-level professions.

Method

A survey examining students' awareness and perception of the profession of audiology was administered in 2009 at the California University of Pennsylvania (Emanuel, Donai, & Araj, 2012). A modified survey, which included questions about awareness of the profession of audiology as well as podiatry and optometry, was distributed in 2012.

Results

Survey data suggest that, overall, students were more accurate in describing the profession of optometry compared to audiology, but no difference existed between their awareness of podiatry and audiology. However, students with self-reported awareness of the three professions were more accurate in describing the professions of podiatry and optometry as compared to audiology.

Conclusions

Results of this distribution suggest an upward trend in audiology awareness among students. However, the awareness of audiology as a potential career path is low relative to that of the professions of optometry and podiatry for those with self-reported knowledge. Future surveys should be distributed to entering college students at other universities, varying in size, location, and demographics.

A randomised clinical trial to assess the effect of a dual treatment on myopia progression: the Cambridge Anti-Myopia Study

PURPOSE

To evaluate the effect of a dual treatment modality for myopia, by improving accommodative functions, on myopia progression.

METHODS

A double blind randomised control trial was conducted on 96 subjects. The treatment modality for the trial employed custom designed contact lenses which control spherical aberration in an attempt to optimise static accommodation responses during near-work, and a vision-training programme to improve accommodation dynamics. Myopia progression was assessed over a 2 year period using cycloplegic autorefraction and biometry.

RESULTS

The mean progression was found to be -0.33 Dioptres (D) over the 2 years of the study. There was no interaction between contact lens treatment and vision training treatment at 24 months (p = 0.72). There was no significant treatment effect of either Vision Training or Contact Lens Spherical Aberration control on myopia progression.

CONCLUSIONS

This study is unable to demonstrate that the progression of myopia can be reduced over a 2 year period by either of the two treatments aimed at improving accommodative function. Neither treatment group (contact lens or vision training) progressed at a slower rate over the 2 years of the study than did the appropriate control group.

Population-based survey of refractive error among school-aged children in rural northern China: the Heilongjiang eye study

BACKGROUND

The prevalence of refractive error in the north of China is unknown. The study aimed to estimate the prevalence and associated factors of refractive error in school-aged children in a rural area of northern China.

DESIGN

Cross-sectional study.

PARTICIPANTS OR SAMPLES

The cluster random sampling method was used to select the sample.

METHODS

A total of 1700 subjects of 5 to 18 years of age were examined. All participants underwent ophthalmic evaluation. Refraction was performed under cycloplegia. Association of refractive errors with age, sex, and education was analysed.

MAIN OUTCOME MEASURES

The main outcome measure was prevalence rates of refractive error among school-aged children.

RESULTS

Of the 1700 responders, 1675 were eligible. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 6.3%, 3.0% and 1.2%, respectively. The prevalence of myopia was 5.0% (84/1675, 95% CI, 4.8%-5.4%) and of hyperopia was 1.6% (27/1675, 95% CI, 1.0%-2.2%). Astigmatism was evident in 2.0% of the subjects. Myopia increased with increasing age, whereas hyperopia and astigmatism were associated with younger age. Myopia, hyperopia and astigmatism were more common in females. We also found that prevalence of refractive error were associated with education. Myopia and astigmatism were more common in those with higher degrees of education.

CONCLUSION

This report has provided details of the refractive status in a rural school-aged population. Although the prevalence of refractive errors is lower in the population, the unmet need for spectacle correction remains a significant challenge for refractive eye-care services.

Gene profiling in experimental models of eye growth: clues to myopia pathogenesis

To understand the complex regulatory pathways that underlie the development of refractive errors, expression profiling has evaluated gene expression in ocular tissues of well-characterized experimental models that alter postnatal eye growth and induce refractive errors. Derived from a variety of platforms (e.g. differential display, spotted microarrays or Affymetrix GeneChips), gene expression patterns are now being identified in species that include chicken, mouse and primate. Reconciling available results is hindered by varied experimental designs and analytical/statistical features. Continued application of these methods offers promise to provide the much-needed mechanistic framework to develop therapies to normalize refractive development in children.

The development of myopia among children with intermittent exotropia

PURPOSE

To describe the long-term refractive error changes in children diagnosed with intermittent exotropia (IXT) in a defined population.

DESIGN

Retrospective, population-based observational study.

METHODS

Using the resources of the Rochester Epidemiology Project, the medical records of all children (<19 years) diagnosed with IXT as residents of Olmsted County, Minnesota, from January 1, 1975 through December 31, 1994 were retrospectively reviewed for any change in refractive error over time.

RESULTS

One hundred eighty-four children were diagnosed with IXT during the 20-year study period; 135 (73.4%) had 2 or more refractions separated by a mean of 10 years (range, 1-27 years). The Kaplan-Meier rate of developing myopia in this population was 7.4% by 5 years of age, 46.5% by 10 years, and 91.1% by 20 years. There were 106 patients with 2 or more refractions separated by at least 1 year through 21 years of age, of which 43 underwent surgery and 63 were observed. The annual overall progression was -0.26 diopters (SD +/- 0.24) without a statistically significant difference between the observed and surgical groups (P = .59).

CONCLUSION

In this population-based study of children with intermittent exotropia, myopia was calculated to occur in more than 90% of patients by 20 years of age. Observation versus surgical correction did not alter the refractive outcome.

Molecular genetics of human myopia: an update

Myopia, or nearsightedness, is the most common human eye disorder in the world, and is a significant global public health concern. Along with cataract, macular degeneration, infectious disease, and vitamin A deficiency, myopia is one of the most important causes of visual impairment worldwide. Severe or high-grade myopia is a leading cause of blindness because of its associated ocular morbidities of retinal detachment, macular choroidal degeneration, premature cataract, and glaucoma. Ample evidence documents the heritability of the non-syndromic forms of this condition, especially for high-grade myopia, commonly referred to as myopic spherical refractive power of 5 to 6 diopters or higher. Multiple high-grade myopia genetic loci have been identified, and confirmatory studies identifying high-grade and moderate myopia loci have also occurred. In general, myopia susceptibility genes are unknown with few association studies performed, and without confirmation in other research laboratories or testing of separate patient cohorts.

Imposed anisometropia, accommodation, and regulation of refractive state

PURPOSE

To determine the effects of imposed anisometropic retinal defocus on accommodation, ocular growth, and refractive state changes in marmosets.

METHODS

Marmosets were raised with extended-wear soft contact lenses for an average duration of 10 weeks beginning at an average age of 76 d. Experimental animals wore either a positive or negative power contact lens over one eye and a plano lens or no lens over the other. Another group wore binocular lenses of equal magnitude but opposite sign. Untreated marmosets served as controls and three wore plano lenses monocularly. Cycloplegic refractive state, corneal curvature, and vitreous chamber depth were measured before, during, and after the period of lens wear. To investigate the accommodative response, the effective refractive state was measured through each anisometropic condition at varying accommodative stimuli positions using an infrared refractometer.

RESULTS

Eye growth and refractive state are significantly correlated with the sign and power of the contact lens worn. The eyes of marmosets reared with monocular negative power lenses had longer vitreous chambers and were myopic relative to contralateral control eyes (p < 0.01). Monocular positive power lenses produced a significant reduction in vitreous chamber depth and hyperopia relative to the contralateral control eyes (p < 0.05). In marmosets reared binocularly with lenses of opposite sign, we found larger interocular differences in vitreous chamber depths and refractive state (p < 0.001). Accommodation influences the defocus experienced through the lenses, however, the mean effective refractive state was still hyperopia in the negative-lens-treated eyes and myopia in the positive-lens-treated eyes.

CONCLUSIONS

Imposed anisometropia effectively alters marmoset eye growth and refractive state to compensate for the imposed defocus. The response to imposed hyperopia is larger and faster than the response to imposed myopia. The pattern of accommodation under imposed anisometropia produces effective refractive states that are consistent with the changes in eye growth and refractive state observed.

Body stature and myopia-The Genes in Myopia (GEM) twin study

OBJECTIVE

A consensus regarding whether a "myopia body stature" exists is still unclear with previous literature being inconsistent and conflicting. We wished to explore the relationship of body stature and myopia using a large Australian twin cohort [The Genes in Myopia (GEM) twin study].

METHODS

All twins examined in the GEM twin study were recruited from the Australian Twin Registry (ATR). Each twin underwent a standard questionnaire, comprehensive eye examination and anthropometric (height and weight) measures were obtained. Myopia was defined as spherical equivalent, equal to or worse than -0.50 Diopters (D) RESULTS: A total of 1224 twins (690 monozygotic twins and 534 dizygotic twins) aged between 18 to 86 years (mean age = 52.36 years) were recruited into the GEM study. The mean height [meters (m)] and weight [kilograms (kg)] of all twins in the GEM study was 1.67 m (1.44 m to 1.95 m) and 71.66 kg (40 kg to 167 kg), respectively. In the heaviest individuals (greater than or equal to 80kg), there was a significant risk (OR 1.48, p = 0.01) of having myopia compared to those in the lightest quartile of weight (less than 61 kg). However, when gender was analyzed separately, this significant risk remained only for females (OR:1.79, p = 0.01).

CONCLUSION

Females in the heaviest quartile of weight have a significantly increased risk of myopia compared to those in the lightest weight quartile in our twin study population. Our study adds to the growing consensus that anthropometric measures should be considered as potential risk factors in myopia.

Prevalence of refractive error in rural Myanmar: the Meiktila Eye Study

OBJECTIVE

To determine the prevalence of refractive error and associated risk factors in the Meiktila District of central rural Myanmar.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Randomized stratified cluster sampling of the inhabitants 40 years or older from villages in Meiktila was performed; 2481 eligible participants were identified, 2076 participated in the study, and adequate refractive data were obtained on 1863 individuals (75.1%).

METHODS

Demographic data including age, gender, and education level were obtained from all participants. The ophthalmic examination included autorefraction, nuclear opalescence (NO) grading at the slit lamp, and applanation tonometry.

MAIN OUTCOME MEASURES

Refractive errors were classified by type of ametropia and their prevalence was determined. Univariate and multivariate analyses were performed and odds ratios were calculated for the predictors of refractive error within the statistical models.

RESULTS

Mean refractive error measured -1.3 diopters (D) (standard deviation [SD], 2.9) and mean cylindrical error measured 1.1 D (SD, 1.5). Myopia of >-1.0 and >-6.0 D occurred in 42.7% (95% confidence interval [CI], 40.4%-44.9%) and 6.5% (95% CI, 5.4%-7.6%) of subjects, respectively. Myopic refractive error was associated significantly with a higher degree of NO (P<0.001) and age. Hypermetropia of >+1.0 D occurred in 15% (95% CI, 5.4%-7.6%) of the population and was associated with higher education levels (P<0.001). Astigmatism worse than 1.0 D occurred in 30.6% (95% CI, 28.5%-32.7%) of the population and was associated with age (P<0.001) and NO (P<0.001).

CONCLUSION

Myopia was more prevalent in older subjects and in those with increased NO. The prevalence rates of myopia in the > or =40 age group are higher than those found in other Asian regions and are likely to contribute to visual impairment.

Parental history of myopia, sports and outdoor activities, and future myopia

PURPOSE

To identify whether parental history of myopia and/or parent-reported children's visual activity levels can predict juvenile-onset myopia.

METHODS

Survey-based data from Orinda Longitudinal Study of Myopia subjects from 1989 to 2001 were used to predict future myopia. Univariate and multiple logistic regression analyses were performed, and receiver operator characteristic (ROC) curves were generated. Differences among the areas under the ROC curves were compared using the method of multiple comparison with the best.

RESULTS

Of the 514 children eligible for this analysis, 111 (21.6%) became myopic. Differences in the third grade between eventual myopes and nonmyopes were seen for the number of myopic parents (P < 0.001) and for the number of sports and outdoor activity hours per week (11.65 +/- 6.97 hours for nonmyopes vs. 7.98 +/- 6.54 hours for future myopes, P < 0.001). Analysis of the areas under the ROC curves showed three variables with a predictive value better than chance: the number of myopic parents, the number of sports and outdoor activity hours per week, and the number of reading hours per week. After controlling for sports and outdoor hours per week and parental myopia history, reading hours per week was no longer a statistically significant factor. The area under the curve for the parental myopia history and sports and outdoor activities model was 0.73. A significant interaction in the logistic model showed a differential effect of sport and outdoor activity hours per week based on a child's number of myopic parents.

CONCLUSIONS

Parental history of myopia was an important predictor in univariate and multivariate models, with a differential effect of sports and outdoor activity hours per week based on the number of myopic parents. Lower amounts of sports and outdoor activity increased the odds of becoming myopic in those children with two myopic parents more than in those children with either zero or one myopic parent. The chance of becoming myopic for children with no myopic parents appears lowest in the children with the highest amount of sports and outdoor activity, compared with those with two myopic parents.

An unusual case of a Forster‐Fuchs’ spot

Myopia has many pathological features in the eye. In this report, we review the unusual case of a young gentleman who developed a Forster-Fuchs' spot at his macula, with his fundus and fluorescein angiographic findings, and current prognosis and management.

Accommodation and induced myopia in marmosets

Accommodation may indirectly influence visually guided eye growth by affecting the retinal defocus signal used to guide growth. Specifically, increased lags of accommodation associated with low stimulus-response (S-R) function slopes will impose increased hyperopic blur on the retina and may induce axial elongation and myopia. The purpose of this study was (1) to measure accommodation in awake, free viewing marmosets and (2) compare accommodation behavior in marmosets before and after inducing different amounts of myopia with binocular spectacle lenses. In untreated marmosets, the average accommodation S-R slope approached one, but showed considerable inter-individual variability (mean+/-SD: 0.964+/-0.249 for monocular viewing; 0.895+/-0.235 for binocular viewing; monocular and binocular measures not significantly different). The monocular S-R slopes were significantly reduced following a period of lens rearing that produced axial myopia (change in slope=-0.30+/-0.30, p<.01) and the reduction in slope was proportional to the amount of myopia induced (p<.01). The S-R slopes measured either under monocular or binocular conditions before induction of myopia were not well correlated with the degree of myopia induced (monocular: r=-.240, p=.453; binocular: r=-.060, p=.824). These results support the hypothesis that the reduction in S-R slope in myopes is a consequence of the myopia induced. The alternative hypothesis-that low S-R slope increases susceptibility to the development of myopia--is not supported by the weak correlation between the pre-manipulation S-R slopes and the magnitude of the myopic shift.

Ocular findings in the chromosome 22q11.2 deletion syndrome

PURPOSE

To identify the ocular features of the chromosome 22q11.2 deletion syndrome and to provide ophthalmologic examination recommendations for affected patients.

METHODS

Ocular abnormalities were evaluated prospectively in patients with 22q11.2 deletion at the Children's Hospital of Philadelphia between 1997 and 1999.

RESULTS

Ninety patients with confirmed 22q11.2 deletion were examined. Posterior embryotoxon was found in 49%, tortuous retinal vessels in 34%, eyelid hooding in 20%, strabismus in 18%, ptosis in 4%, amblyopia in 4%, and tilted optic nerves in 1%.

CONCLUSIONS

The high incidence of ocular conditions that can potentially affect visual development suggest that children with 22q11.2 deletion should undergo a comprehensive eye examination upon diagnosis of the condition with follow-up as indicated by the findings in each case. In addition, knowledge of the ocular findings, in conjunction with certain cardiac, otolaryngologic, immunologic, and other systemic findings, may alert physicians to the possibility of a chromosome 22q11.2 deletion.

Temporal constraints on experimental emmetropization in infant monkeys

PURPOSE

To characterize the temporal integration properties of the emmetropization process, the authors investigated the effects of brief daily interruptions of lens wear on the ocular compensation for negative lenses in infant rhesus monkeys.

METHODS

Eighteen monkeys wore -3 D lenses binocularly starting from approximately 3 weeks of age. Six of these monkeys wore the lenses continuously. For the other animals, the -3 D lenses were removed for four 15-minute periods each day. During these periods, the monkeys viewed through either zero-power lenses (n = 6) or +4.5 D lenses (n = 6). Three monkeys reared with binocular plano lenses and 16 monkeys reared normally served as controls. Refractive development was assessed by cycloplegic retinoscopy and A-scan ultrasonography.

RESULTS

As expected, the group of animals that wore the -3 D lenses continuously exhibited clear evidence of compensating axial myopia. These predictable myopic changes were mostly eliminated by the brief, daily periods of viewing through plano lenses. Interestingly, brief periods of viewing through +4.5 D lenses produced weaker protective effects.

CONCLUSIONS

Brief periods of unrestricted vision can prevent the axial myopia normally produced by long daily periods of imposed hyperopic defocus. Thus, the temporal integration properties of the emmetropization process normally reduce the likelihood that transient periods of hyperopic defocus will cause myopia.

Prevalence of myopia and hyperopia in a population of Polish schoolchildren

PURPOSE

The aim of this study was to determine the prevalence of myopia and hyperopia in a population of Polish schoolchildren.

METHODS

A total of 4422 students were examined (2107 boys and 2315 girls, aged 6-18 years, mean age 11.1, S.D. 3.5). The examination included retinoscopy under cycloplegia induced with 1% tropicamide. Myopia was defined as a spherical equivalent (SE) of at least -0.5 dioptres (D), and hyperopia as a SE of at least +1.0 D. Data analysis was performed using Spearman's rank correlation coefficients and chi-squared test; p-values of <0.05 were considered statistically significant.

RESULTS

It was observed that 13.3% of Polish students in the age group ranging from 6 to 18 years were myopic while 13.1% of students were hyperopic. Furthermore, a positive correlation was found between the prevalence of myopia and age (p < 0.001) and a negative correlation between prevalence of hyperopia and age (p < 0.001). It was observed that the prevalence of myopia increases substantially between 7 and 8 years of age (p < 0.01). Moreover, it was determined that with age the average refractive error among schoolchildren becomes more myopic (p < 0.001).

CONCLUSIONS

The occurrence, degree and progress of myopia and hyperopia in Poland is similar to that in other European countries with a predominantly Caucasian population.

Prevalence of myopia in Danish conscripts

PURPOSE

This study aimed to determine the prevalence of myopia among Danish conscripts and compare the results with those from similar Danish studies carried out in 1882 and 1964. Furthermore, the relationships between myopia and educational level, ethnicity, intelligence (IQ), body mass index (BMI) and height were analysed.

METHODS

We carried out a cross-sectional study based on medical reports for 4681 male conscripts. The following data were collected from September to December 2004: age; place of birth; weight; height; power of spectacles or contact lenses; visual acuity; number of years at school (8-13 years); occupation; intelligence test (IQ test) score, and ethnicity.

RESULTS

The prevalence of myopia (<or= - 0.5 D, spherical equivalent) was 12.8% (95% confidence interval [CI]+/- 0.96); the prevalence of high myopia (< - 6.5 D) was 0.3% (95% CI +/- 0.15). Myopes scored higher (45.3 [SD 9.4]) on IQ tests than emmetropes (41.4 [SD 10.4]) (p < 0.001) and had a higher educational level. No relationship was found between myopia and BMI, height or ethnicity.

CONCLUSIONS

The study reports a significantly decreasing prevalence of low myopia among Danish conscripts in 2004 compared with 1964. Compared with the results from the 1882 study, the prevalence of low myopia seems stable. The prevalence of high myopia has decreased significantly since 1882 and has also tended to decrease from 1964. Number of years in education and IQ test score were related to myopia.