Myopia

Many more children suffer from myopia than was the case 50 years ago: in parts of Asia, over 70% of children are now myopic and require some form of refractive correction to see clearly. A vast literature on possible causes of myopia and methods for controlling myopia progression has built up over the years and, until recently, distinguishing between hypothesis and real evidence has posed a significant challenge. Recent clinical trials of a variety of methods for controlling myopia progression have shown encouraging results and several methods are becoming commercially available. This article addresses the question: should we now be attempting to control myopia progression in a clinical setting? If so, what are the options?

El objetivo del presente trabajo es presentar, a manera de propuesta, un programa preventivo de la miopía para ser aplicado a niños de educación primaria, cuya objetivo principal es el entrenamiento de prácticas conductuales de higiene visual, que prevengan el desarrollo o aparición de dicho problema visual. Como preámbulo a la presentación de tal propuesta, a) se dedicará un espacio para hablar sobre la miopía dando su definición y mencionando algunas de sus generalidades; b) se expondrá brevemente una perspectiva psicológica sobre la génesis y mantenimiento de la miopía, aplicando el modelo interconductual de la salud desarrollado por Ribes (1989); y c) apoyado en el modelo de génesis de la miopía propuesto por Santacreu (1995), se hará un breve análisis de este trastorno visual, identificado como un problema de salud pública.

Introduction: Myopia is a significant public health problem in Singapore with estimates that more than 50% of the population is affected by it by the time of adulthood. Childhood obesity is also increasing and has been linked to long-term health problems. Recent studies have found that Singaporean children in Primary 1 spend less than 3 hours a day outdoors which is less than children in other countries. Physical activity has been shown to be protective against obesity and recently, there has been some evidence to suggest that time spent outdoors may reduce the prevalence and severity of myopia. This study aims to explore the barriers and enablers to children in Singapore participating in outdoor activities. Materials and Methods: Qualitative data, gathered from focus group discussions was thematically analysed against the PRECEDE component of the PRECEDE-PROCEED model which provided a conceptual framework for examining factors relevant to children participating in an outdoor activi...

Refractive procedures enjoy very high success rates and are among the most commonly performed elective surgeries in medicine. With better insights into preoperative screening, the overwhelming majority of cases have successful outcomes. Unfortunately, however, all refractive surgeons must appropriately manage unsuccessful cases. Unsuccessful refractive surgery procedures may relate to each step of the refractive surgery process: preoperative screening, surgical planning, intraoperative events, and postoperative biomechanical or healing anomalies. This paper reviews the management of unsuccessful laser-assisted in situ keratomileusis (LASIK) procedures, focusing on significant advances related to wavefront-guided therapeutic ablations.

Background Theoretically, the accommodative and vergence demands are different between single-vision contact lenses and spectacle lenses. The aim of the present study was to determine whether these differences exist when these two correction methods are used in clinical practice. For this, different visual parameters that characterize the accommodative (accommodation amplitude, accommodative facility, and accommodative response) and binocular function (near and distance horizontal and vertical dissociated phorias, near and vertical associated phorias, near and distance negative and positive fusional vergence, vergence facility, near point of convergence, negative and positive relative accommodation, stimulus AC:A ratio and stereoacuity) were evaluated in a student population when their myopia was corrected with either spectacles or soft contact lenses (SCL). Methods All parameters were measured on two separate occasions in 30 myopic habitual contact lens and spectacle wearers of mean age 19 ± 2.4 years. Some parameters such as accommodation amplitude, accommodative response, and stimulus AC:A ratio were measured using two measurement methods which are commonly used in clinical practice. Three measurements were taken for each parameter and averaged. For the comparative statistical analysis, we used the Student’s t-test (p value < 0.05). Results The following statistically significant differences were found with the use of SCL in comparison to spectacles: higher accommodative lags, higher negative relative accommodation, more esophoric near horizontal dissociated phoria, and lower negative fusional vergence in near vision. Conclusions The results found in this study show a definite trend towards poorer accommodative and vergence function with the use of contact lenses in comparison to glasses. This downward trend, though not statistically significant in accommodative function (lower PRA values and less lens amplitude of accommodation) might suggest that temporal insufficiency in the accommodation process could be occurring while contact lenses are used, thereby possibly creating a lag in accommodation to reduce associated overconvergence. This would be manifested in more esophoric values being found in the vergence function. The higher accommodative lags found in this study with SCL could indicate that prolonged use of SCL in near tasks may provoke a continuous hyperopic retinal defocus, a risk factor for the onset and progression of myopia, as indicated in numerous studies.

Mircea Eliade, Romanul adolescentului miop
prefaţă de Liviu Bordaş
Format: 120x200 mm
Număr pagini: 464
Data apariţie: august 2009
ISBN: 978-973-675-644-3
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Nonconformistul chilug de la liceul "Spiru Haret" nu credea că cel mai interesant lucru din adolescenţă e dragostea. De aceea, romanul său va fi unul cerebral, dar nu psihologic, nu "falsificat de analize". Lipsa succeselor şcolare şi mondene devine o treaptă către o altfel de împlinire. Ţelul pe care şi-l stabileşte adolescentul miop nu este să ajungă ca alţii, ci să ajungă la sine însuşi. În loc să fie imitarea modelelor străine, atingerea unor idealuri stabilite de cei din jur, adolescenţa este perioada esenţială a descoperirii de sine. Dar nu numai descoperire, ci şi o veritabilă construire a personalităţii. Un efort susţinut prin voinţă, asceză, singurătate, renunţări. Prin disciplină fermă şi austeritate, prin lecturi aspre, nesfârşite, prin luptă cu duşmanii din afară şi dinlăuntru. Luptă cu mediocritatea, cu buchiseala şi cultura de manual, dar şi cu sentimentalismul, nostalgia, tristeţea. Învingându-şi slăbiciunile şi crescându-şi bogăţiile interioare, Eliade se construieşte ca personalitate.

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.

Purpose: This study investigated correlation between the duration of lens wear and epithelial and stromal thickness in low to moderate and high myope orthokeratology lens wearers.
Materials and methods: Twenty-six high myope (mean refractive error -7.64±1.54D) orthokeratology lens wearers and 30 low to moderate myopes (mean refractive error -3.08±1.06D) orthokeratology lens wearers were recruited cross-sectionally from the participating practices. These subjects were Chinese schoolchildren aged 9-18 years. The recruited orthokeratology lens wearers had worn lenses for 6-65 months. Epithelial and stromal thickness of the central and midperipheral cornea was measured with the Sonogage Cornea-gage Plus Ultrasound Pachometer (Sonogage, Cleveland, OH). In each group, epithelial and stromal thickness was analyzed with Spearman correlation test to assess correlation with the duration of orthokeratology lens wear.
Results: Minimal and almost absent correlation was found in epithelial measurements at all points in both low to moderate and high myopic groups. Correlation was also almost absent in the midperipheral stromal thickness when tested against the duration of lens wear. However, a weak correlation was found between stromal thickness and duration of wear in the central stroma measurements of the low to moderate myopes (r=0.207) and high myopes (r=-0.254).
Conclusions: The central stroma of the low to moderate myope orthokeratology wearer was found to become thicker with time and the central stroma of the high myope orthokeratology wearer was found to become thinner with time when tested for correlation with the duration of wear. These results suggest a possible longitudinal change in the corneal stromal thickness with orthokeratology lens wear.

The importance of optimal visual function in demanding interceptive tasks is far from established. The aim of the study was to determine whether induced myopic blur and hence sub-optimal visual function would give rise to a detrimental effect on performance in the execution of an interceptive task. The batting performance of grade level cricket players was assessed facing a bowling machine whilst wearing contact lenses of four different refractive conditions (plano (nil), +1.00, +2.00 and +3.00 D over-refraction), inducing increasing amounts of myopic blur. Performance for each condition was assessed based both on the shot quality against each delivery judged by a qualified cricket coach blind to each condition, along with an evaluation of the quality of ball–bat contact for each delivery. No significant change was found in batting performance with the introduction of +1.00 and +2.00 D of induced myopic blur. A +3.00 D over-correction was required before any significant decrease in batting performance was detected, demonstrating that batters needed to be essentially legally blind (as simulated through the use of the +3.00 D over-refraction) before there was any significant measurable decrement in batting performance. We concluded that optimal visual correction is not necessarily required for optimal performance in a demanding interceptive task, and that the human perceptual-motor system is capable of compensating for marked alterations in input.

Background Theoretically, the accommodative and vergence demands are different between single-vision contact lenses and spectacle lenses. The aim of the present study was to determine whether these differences exist when these two correction methods are used in clinical practice. For this, different visual parameters that characterize the accommodative (accommodation amplitude, accommodative facility, and accommodative response) and binocular function (near and distance horizontal and vertical dissociated phorias, near and vertical associated phorias, near and distance negative and positive fusional vergence, vergence facility, near point of convergence, negative and positive relative accommodation, stimulus AC:A ratio and stereoacuity) were evaluated in a student population when their myopia was corrected with either spectacles or soft contact lenses (SCL). Methods All parameters were measured on two separate occasions in 30 myopic habitual contact lens and spectacle wearers of mean age 19 ± 2.4 years. Some parameters such as accommodation amplitude, accommodative response, and stimulus AC:A ratio were measured using two measurement methods which are commonly used in clinical practice. Three measurements were taken for each parameter and averaged. For the comparative statistical analysis, we used the Student’s t-test (p value < 0.05). Results The following statistically significant differences were found with the use of SCL in comparison to spectacles: higher accommodative lags, higher negative relative accommodation, more esophoric near horizontal dissociated phoria, and lower negative fusional vergence in near vision. Conclusions The results found in this study show a definite trend towards poorer accommodative and vergence function with the use of contact lenses in comparison to glasses. This downward trend, though not statistically significant in accommodative function (lower PRA values and less lens amplitude of accommodation) might suggest that temporal insufficiency in the accommodation process could be occurring while contact lenses are used, thereby possibly creating a lag in accommodation to reduce associated overconvergence. This would be manifested in more esophoric values being found in the vergence function. The higher accommodative lags found in this study with SCL could indicate that prolonged use of SCL in near tasks may provoke a continuous hyperopic retinal defocus, a risk factor for the onset and progression of myopia, as indicated in numerous studies.

We investigated the relationship between myopia and peripheral refraction for distance and near vision by measuring peripheral refractive errors in 10 myopic and 10 emmetropic participants at viewing distances of 2.5 and 0.4 m. Measurements were made at the fovea, and at eccentricities of 10°, 20° and 30° in the temporal and nasal hemispheres of the horizontal visual field. Our results showed that peripheral astigmatism increased with increasing eccentricity, but there was no significant difference between refractive error groups except at 30° eccentricity in the temporal retina. Considering the Mean Spherical Equivalent errors, emmetropes became relatively myopic at peripheral eccentricities, but there was little change in myopes. The effect of viewing distance on astigmatism or Mean Spherical Equivalent error was not significant. Our results do not support the view that myopia is associated with changes in peripheral refraction during distance or near vision.