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PubMed2002

Darkness and near work: myopia and its progression in third-year law students.

PURPOSE: To evaluate myopia prevalence, myopia progression, and various potential myopia risk factors in third-year law students. DESIGN: Cross-sectional study and survey. PARTICIPANTS: One hundred seventy-nine third-year law students at the University of Pennsylvania. METHODS: We administered a questionnaire to assess the prevalence of myopia, myopia progression, and risk factors, including near work, family history, and daily light/dark exposure. We conducted a screening eye examination to ascertain myopia status. Myopia was defined as the mean spherical equivalent of the two eyes of </=-0.5 diopters; myopia progression was defined by the self-reported need for a stronger eyeglass prescription during law school. MAIN OUTCOME MEASURES: (1) prevalence of myopia, (2) progression of myopia. RESULTS: Seventy-nine percent of the class participated (n = 179, two were excluded for amblyopia leaving 177 students). Fifty-eight percent were male, 75% were Caucasian, and the mean age was 27 years. Seventy-nine percent reported parental myopia. The mean amount of near work was 7.4 hours/day; mean sleep was 7.9 hours/day; mean darkness was 5.3 hours/day. Sixty-six percent of the students were myopic. Of 96 participants myopic before law school, myopia increased in 83 (86%) during law school. Among 75 students not myopic at the beginning of law school, 14 (19%) became myopic. The onset of myopia could not be determined for 6 patients. There were trends for higher myopia prevalence among those with a parental myopia history (P = 0.14) and for increased myopia progression among those reporting more daily near work (P = 0.18). Students with </=5.6 hours of daily darkness were more likely to report myopia progression than those with >5.6 hours of darkness per day (95% vs. 80%, P = 0.07). To account for possible confounding effects of risk factors with myopia progression, logistic regression with categorization of the continuous exposure variables (hours of near work, sleep, and darkness) above or below median values weakened the near work association (odds ratio 1.8, 95% confidence interval 0.5-6.7, P = 0.35) but continued to identify darkness association with daily hours of darkness (odds ratio 4.8, 95% confidence interval 1.0 >/= 23.3, P < 0.05). Among the 77 students with myopia onset before college, those with </=5.6 hours of daily darkness were more likely to progress than those with more hours of daily darkness (97% vs. 76%, P = 0.01). CONCLUSIONS: This study confirms high rates of myopia prevalence and myopia progression among law students. The strongest association, especially in those with myopia onset before college, was a relation of myopia progression during law school with less daily exposure to darkness, a potential risk factor previously identified in childhood myopia. The role of exposure to darkness in refractive development warrants additional study.

Adult↗
PubMed2005

The association between myopia and various subtypes of lens opacity: SEE (Salisbury Eye Evaluation) project.

PURPOSE: To establish the relationship between myopia and lens opacity. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Two thousand five hundred twenty participants from the Salisbury Eye Evaluation aged 65 to 84 years. METHODS: Participants filled out questionnaires regarding medical history, social habits, and a detailed history of distance spectacle wear. They underwent a full ocular examination. Lens photographs were taken for assessment of lens opacity using the Wilmer grading system. Multivariate logistic regression models using generalized estimating equations were used to analyze the relationship between lens opacity type and degree of myopia, while accounting for potential confounders. MAIN OUTCOME MEASURES: Presence of posterior subcapsular opacity, cortical opacity, or nuclear opacity. RESULTS: Significant associations were found between myopia and both nuclear and posterior subcapsular opacities. For nuclear opacity, the odds ratios (ORs) were 2.25 for myopia between -0.50 diopters (D) and -1.99 D (P<0.001), 3.65 for myopia between -2.00 D and -3.99 D (P<0.001), 4.54 for myopia between -4.00 D and -5.99 D (P<0.001), and 3.61 for myopia -6.00 D or more (P = 0.002). For posterior subcapsular cataracts, ORs were 1.59 for myopia between -0.50 D and -1.99 D (P = 0.11), 3.22 for myopia between -2.00 D and -3.99 D (P = 0.002), 5.36 for myopia between -4.00 D and -5.99 D (P<0.001), and 12.34 for myopia -6.00 D or more (P<0.001). No association was found between myopia and cortical opacity. The association between posterior subcapsular opacity and myopia was equally strong for those wearing glasses by age 21 years and for those without glasses; for nuclear opacity, significantly higher ORs were found for myopes who started wearing glasses after age 21. CONCLUSIONS: These results confirm the previously reported association between myopia, posterior subcapsular opacity, and nuclear opacity. Furthermore, the strong association between early spectacle wear and posterior subcapsular opacity among myopes, absent for nuclear opacity, suggests that myopia may precede opacity in the case of posterior subcapsular opacity, but not nuclear opacity. Measures of association between posterior subcapsular opacity and myopia were stronger in the current study than have previously been found. Longitudinal studies to confirm the association are warranted.

Aged↗
PubMedDate not supplied

Prevalence of myopia in adults: implications for refractive surgeons.

BACKGROUND: We reviewed the research on the prevalence of myopia in the adult population to compare the refractive distribution of patients being treated with excimer laser photorefractive keratectomy to correct myopia, and assess the potential market for excimer laser surgery. METHODS: All published reports of myopia prevalence in adults were reviewed, as well as the prevalence in the Melbourne Visual Impairment Project and the distribution of refractive errors treated by the Melbourne Excimer Laser Group in 1994. RESULTS: A large population-based study of people aged 4 to 74 years in the U.S. showed that 43% had low myopia (less than -5.00 diopters (D)), 3.2% had high myopia (-5.01 to -10.00 D), and 0.2% had extreme myopia (more than -10.00 D). In Asian populations these proportions may be much higher and in African and Pacific island groups, much lower. In the Melbourne Visual Impairment Project, we found the prevalence of low myopia was 21%, high myopia 2%, and extreme myopia 0.3%. A single excimer laser has operated for 3 years in Melbourne. Of those treated, 45% had low myopia, 42% high myopia, and 13% extreme myopia. Compared to low myopes, high myopes were ten times (OR: 9.8; Confidence interval: 6.69 to 12.91) more likely to have excimer laser treatment and extreme myopes were 16 times (OR: 16.40; Confidence interval: 12.53 to 20.27) more likely. CONCLUSIONS: Although there are many more people with lower amounts of myopia in the population and the clinical results have been more predictable after one procedure in this group, the perceived benefits of excimer laser treatment may be greater for those with higher amounts of myopia, thus influencing their decision to undergo excimer laser surgery to correct their myopia. There is clearly a large market potential for excimer laser surgery in people with low myopia.

Adolescent↗
PubMedDate not supplied

Results of photorefractive keratectomy for low, moderate, and high myopia.

PURPOSE: To compare the predictability, safety, and stability of photorefractive keratectomy (PRK) in patient groups with low, moderate, and high myopia. The astigmatic component of these corrections was also evaluated. METHODS: In 110 patients, 110 consecutive eyes were operated with a VISX 20/20 excimer laser using standard settings and a 6 mm ablation zone for PRK. The eyes were divided into three groups. In low myopia group (N = 52) the intended correction ranged from -1.50 to -6.00 D (mean -4.28 +/- 1.29 D), in the moderate myopia group (N = 34) from -6.10 to -8.00 D (mean -7.05 +/- 0.70 D), and in the high myopia group (N = 24) from -8.10 to -11.50 D (mean -9.40 +/- 1.13 D). Twenty-seven eyes had 0.75 D of preoperative myopic astigmatism. All patients were followed for 12 months and 36% (N = 40) were available for the 24-month follow-up examination. RESULTS: At 12 months the spherical equivalent manifest refraction was within 0.50 D of intended refraction in 58% (N = 30) of eyes in the low myopia group, 50% (N = 17) in the moderate myopia group, and 29% (N = 7) in the high myopia group. Eighty-seven percent (N = 45) in low, 79% (N = 27) in moderate, and 67% (N = 16) in the high myopia group were within 1.00 D of intended refraction. At 12 months, 88% (N = 46) of the eyes with low myopia, 68% (N = 23) with moderate myopia, and 68% (N = 16) with high myopia achieved uncorrected visual acuity of 20/40 or better, while 6% (N = 16) of the eyes lost and 4% (N = 4) gained two or more lines of Snellen visual acuity. Uncorrected visual acuity of 20/20 or better at 12 months was achieved by 58% (N = 30) of low myopes, 26% (N = 9) of moderate myopes, and 33% (N = 8) of high myopes; 20/25 or better by 71% (N = 37) of low myopes, 39% (N = 13) of moderate myopes, and 42% (N = 10) of high myopes. Overcorrection (> 0.25 D) was detected at 12 months in 31% (N = 16) with low, 38% (N = 13) with moderate, and 67% (N = 16) with high baseline myopia, with statistically significant differences between the low and high myopia groups. CONCLUSION: In all groups, the safety of PRK was satisfactory, without major complications; in the high myopia group where corrections exceeded 8.0 D (mean -9.40 +/- 1.13 D) the procedure was only slightly more unpredictable than in low and moderate myopia at 1 year.

Adolescent↗
PubMed2006

High myopia and glaucoma susceptibility the Beijing Eye Study.

OBJECTIVE: To evaluate whether marked myopia, compared with moderate myopia and low myopia, is associated with a higher prevalence of glaucomatous optic nerve damage. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Four thousand four hundred thirty-nine of 5324 subjects 40 years or older were invited to participate (response rate, 83.4%). The group was stratified according to refractive error into high myopia (myopia > -8 diopters [D]), marked myopia (<-6 to -8 D), moderate myopia (<-3 to -6 D), low myopia (<-0.5 to -3 D), emmetropia (-0.5 to + <2 D), and hyperopia (>+ 2 D) subgroups. METHODS: Morphologic assessment of optic disc monoscopic photographs. MAIN OUTCOME MEASURES: Morphologic optic disc parameters and intraocular pressure (IOP). RESULTS: For 4319 (97.3%) subjects (8484 eyes), optic disc photographs were evaluated. Prevalence of glaucomatous optic nerve atrophy as defined by the glaucomatous optic nerve head appearance did not vary significantly (P = 0.77; odds ratio [OR], 1.2; 95% confidence interval [CI], 0.38-3.81) between the highly myopic group and the group with marked myopia. In both refractive groups combined, glaucoma frequency seemed to be higher (P = 0.075; OR, 2.28; 95% CI, 0.99-5.25) higher than in the group with moderate myopia; it was significantly (P = 0.001; OR, 3.5; 95% CI, 1.71-7.25) higher than in the group with low myopia; significantly (P<0.001; OR, 7.56; 95% CI, 3.98-14.35) higher than in the group with emmetropia; and significantly (P = 0.005; OR, 4.23; 95% CI, 1.57-11.45) higher than in the group with hyperopia. Glaucoma frequency did not vary significantly between the hyperopic group and the emmetropic group (P = 0.17), the group with low myopia (P = 0.83), and the group with moderate myopia (P = 0.32). Intraocular pressure did not vary significantly (P>0.10) between any of the subgroups. Similar results were obtained for the frequency of glaucoma defined as glaucomatous optic disc appearance and visual field defects. In binary logistic regression analysis, presence of glaucoma was significantly associated with the myopic refractive error (P<0.001), age (P<0.001), and IOP (P<0.001). CONCLUSIONS: Marked to high myopia with a myopic refractive error exceeding -6 D may be a risk factor associated with glaucomatous optic neuropathy.

Adult↗
PubMed1999

The relationship between glaucoma and myopia: the Blue Mountains Eye Study.

OBJECTIVE: To quantify the relationship between myopia and open-angle glaucoma, ocular hypertension (OH), and intraocular pressure (IOP) in a representative older population. DESIGN: Cross-sectional population-based study of 3654 Australians 49 to 97 years of age. METHODS: Subjects with any myopia (> or =-1.0 diopter [D]) were identified by a standardized subjective refraction and categorized into low myopia (> or =-1.0 D to <-3.0 D) or moderate-to-high myopia (> or =-3.0 D). Glaucoma was diagnosed from characteristic visual field loss, combined with optic disc cupping and rim thinning, without reference to IOP. Ocular hypertension was diagnosed when applanation IOP was greater than 21 mmHg in either eye in the absence of glaucomatous visual field and optic disc changes. MAIN OUTCOME MEASURE: General estimating equation models were used to assess associations between eyes with myopia and either glaucoma or OH. RESULTS: Glaucoma was present in 4.2% of eyes with low myopia and 4.4% of eyes with moderate-to-high myopia compared to 1.5% of eyes without myopia. The relationship between glaucoma and myopia was maintained after adjusting for known glaucoma risk factors, odds ratio (OR) of 2.3, and 95% confidence intervals (CI) of 1.3 to 4.1 for low myopia. It was stronger for eyes with moderate-to-high myopia (OR, 3.3; CI, 1.7-6.4). Only a borderline relationship was found with OH, OR of 1.8 (CI, 1.2-2.9) for low myopia, and OR of 0.9 (CI, 0.4-2.0) for moderate-to-high myopia. Mean IOP was approximately 0.5 mmHg higher in myopic eyes compared to nonmyopic eyes. CONCLUSIONS: This study has confirmed a strong relationship between myopia and glaucoma. Myopic subjects had a twofold to threefold increased risk of glaucoma compared with that of nonmyopic subjects. The risk was independent of other glaucoma risk factors and IOP.

Aged↗
PubMed2004

[Changes in the static visual field of patients with low and medium myopia].

UNLABELLED: Myopia is associated with many diverse changes in the structure and function of the eye. Determination of the visual field belongs to the diagnostic arsenal used for detection and monitoring of such alterations. It is well established that myopia is accompanied by changes in the kinetic visual field. Recently, static visual field examinations are gaining wider acceptance as they represent the most sensitive and reliable approach to early changes in myopia. However, only a few papers on static perimetry in myopia have been published and the results are conflicting. No publications have appeared in Polish medical press. Therefore, we decided to investigate which alterations occur in the static visual field of patients with myopia. We enrolled 32 men and 58 women (180 eyes) aged 19 to 34 (mean 23 years) and formed three groups (I-III) of 30 subjects each: (I) control (without any refractive anomaly); (II) low myopia (average refractive error -2.0 D sph. +/- SD of 1.0); and (III) medium myopia (average refractive error -5.6 Dsph +/- SD of 1.2). Myopia was defined as a refractive error of value < or = -0.5 D, with low myopia not exceeding 4.0 D, and medium myopia between -4 and -8 D. Inclusion criteria were: full visual acuity with/without correction, astigmatism < 0.75 D cyl., intraocular pressure < 21 mm Hg, and no eye pathology other than myopia. A full panel of ophthalmologic tests was carried out, including repeat static perimetry (central 30 degrees) with Medmont M600 perimeter. Appropriate lenses were used during the tests. Average Defect (AD), Pattern Defect (PD), Mean Sensitivity (MS), and Fluctuation (F) values were recorded. Static visual field was assessed with the repeat examination only. Spearman's rank correlation coefficient, Kendall's tau, Gamma and linear correlations were analyzed. P values of less than 0.05 were considered statistically significant. A reduction in AD among subjects with low (P < 0.03) and medium (P < 0.03) myopia was found. There were no significant alterations in PD (Tab. 1). Elevation of myopia leads to reduction in AD (P < 0.0003) (Fig. 1), reduction in MS (P < 0.004) (Fig. 2), as well as increase in F (P < 0.04) (Fig. 3). CONCLUSION: Low and medium myopia may produce significant alterations in the visual field.

Adult↗
PubMedDate not supplied

[Occurrence of changes in the eye in diabetic retinopathy with significant myopia].

The optic disc and retinal neovascularization are less prominent and less frequent in myopic eyes in patients suffering from diabetes mellitus. The exact mechanisms of this phenomenon are not well known, but there is some evidence that there is a reduced blood flow in myopic eyes which is associated with less damaged microcirculation in eyes of patients with diabetes mellitus. The aim of our study was to evaluate the correlation between myopic refractive error and degree of diabetic retinopathy. We conducted a retrospective study in a group of randomized patients, divided into the following groups according to their refractive error: emmetropia (30 eyes), myopia simplex (30 eyes) and high myopia, over -6.5 dsph (21 eyes). Among patients with high myopia, seven had monocular myopia. All patients suffered from non insulin dependent diabetes mellitus for more than ten years, and their average age was 52.37-3.48 years. We did not observe patients with rubeosis iridis and neovascular glaucoma or patients with myopia less than -2.0 dsph. Our results indicated that there was no significant difference in the appearance of fundus between the studied groups. In all patients the incidence rate of non proliferative and proliferative diabetic retinopathy was the same as well as the absence of retinopathy (Fisher's test). The only exception were the patients with monocular myopia over -13.o dsph who had no signs of diabetic retinopathy in myopic eye, while the other, emmetropic eye, showed various stages of retinopathy, from severe non proliferative to proliferative. Some of the risk factors which influence the incidence rate of ocular complications in diabetic patients are well known, as are duration of diabetes mellitus, blood sugar level, blood pressure, ocular pressure and eye perfusion. On the other hand, it is also known that amblyopia, optic atrophy, low blood pressure in central retinal artery and retinitis pigmentosa are ocular conditions which are not associated with proliferative diabetic retinopathy. It was also noticed that complications of diabetes in high myopic eyes are less prominent than in emmetropic eyes. This finding is in harmony with our results. Sultanov et al. observed diabetic changes in the retina in 40.9% of myopic refraction patients, 65.2% of emmetropia cases and 70.4% of hypermetropia cases. The severity of involvement was less in myopia than in other types of refraction. In medium severe myopia, no proliferative diabetic retinopathy was observed, and in high myopia (10 eyes) no diabetic involvement of the fundus oculi was found. In anisometropia diabetic symptoms on the myopic side were either absent or poorly manifest. The possible cause of such findings could be the changes in retinal perfusion in myopic eyes and eyes in patients with diabetes mellitus. In 1973 a lower blood flow was detected in the retina and the choroid, proportionally to the degree of myopia. In 1982, Perkins indicated that the circulation time and pulsation rate in the central retinal artery in myopic eyes were reduced proportionally to the degree of myopia. In cases with early diabetic retinopathy Coscas detected a lesser blood flow in retinal veins. On the other hand, it has been found that high blood pressure increases the risk of diabetic retinopathy. These data suggest that the reduced blood flow in high myopia is a protective factor regarding the occurrence of complications in diabetes. Anisometropia and amblyopia in cases with monocular myopia, which presents a particular group in our study, could be factors which also prevent the occurrence of proliferative diabetic retinopathy. Instead of conclusion, we would like to point out that pathophysiologic mechanisms of these phenomena are not discussed enough. It is, nevertheless, important to appropriately examine the fundus in patients with high myopia and diabetes mellitus, because if the complications appear, they may be disastrous and must be treated immediately.

Diabetic Retinopathy↗
PubMed2000

Treatment of myopia and myopic astigmatism by customized laser in situ keratomileusis based on corneal topography.

OBJECTIVE: To evaluate the predictability, efficacy, and safety of customized laser in situ keratomileusis (LASIK) based on corneal topography in myopia and myopic astigmatism. DESIGN: Prospective, noncomparative interventional case series. PARTICIPANTS: One hundred fourteen patients (eyes) with myopia of -1 to -6 diopters (D) and astigmatism of 0 to -4 D (low myopia group), and 89 patients (eyes) with myopia of -6.10 to -12.00 D and astigmatism of 0 to -4.00 D (high myopia group). INTERVENTION: LASIK was performed with the Hansatome Microkeratome and the Keracor 217 spot-scanning excimer laser (Bausch & Lomb Surgical Technolas, Munich, Germany). Individual ablation patterns were calculated on the basis of elevation data obtained with the Orbscan II corneal topography system (Bausch & Lomb Surgical, Irvine, CA). MAIN OUTCOME MEASURES: Manifest spectacle refraction, visual acuity, and change in visual acuity at 3 months after surgery. RESULTS: At 3 months, 51 patients in the low myopia group and 40 patients in the high myopia group were available. In the low (high) myopia group, 96.1% (75.0%) were within +/-0.50 D of emmetropia, and uncorrected visual acuity was 20/20 or better in 82.4% (62.5%), 20/25 or better in 98.0% (70.0%), and 20/40 or better in 100% (95.0%). A loss of two or more lines of spectacle-corrected visual acuity occurred in 3.9% of the low and 5. 0% of the high myopia group. In low myopia, spectacle-corrected visual acuity was 20/12.5 or better in 5.9% preoperatively and in 13.7% at 3 months and 20/15 or better in 37.3% and 47.1%, respectively. Differences were statistically significant. CONCLUSIONS: The customized LASIK based on corneal topography used in this study showed high predictability and efficacy in myopia and myopic astigmatism of -1.00 to -6.00 D, and could possibly improve spectacle-corrected visual acuity in myopia of -1.00 to -6.00 D. Predictability and efficacy were somewhat lower in myopia and myopic astigmatism of -6.10 to -12.00 D. In both groups, a small number of patients lost two or more lines of spectacle-corrected visual acuity.

Astigmatism↗
PubMed2004

Inhibitory effects of apomorphine and atropine and their combination on myopia in chicks.

PURPOSE: The inhibitory effect of apomorphine on form-deprivation myopia implies a role for dopaminergic pathways in eye growth; however, the effect of apomorphine on lens-induced changes has not been studied. Our study filled this deficiency. After establishing that apomorphine inhibited lens-induced myopia, we investigated whether apomorphine and atropine acted sequentially via the same control pathway or via different parallel pathways. METHODS: This study, conducted in 8-day-old chicks, was comprised of two parts: (1) a comparative study of apomorphine's effect on lens-induced myopia (-15 D), form-deprivation myopia (diffusers), and lens-induced hyperopia (+15 D) and (2) a study of the interacting effects of apomorphine and atropine on lens-induced myopia and form-deprivation myopia. In the first part, dH2O and six apomorphine doses (8 pmole to 800 nmole in log10 steps) were given as 10-microL intravitreal injections in combination with the above visual treatments. Apomorphine was used alone or given with atropine in the second part, which included four drug treatment groups: (1) control (dH2O); (2) 80 pmole of apomorphine; (3) 18 nmole of atropine; and (4) apomorphine + atropine. Additional dH2O injections were used to equalize the number of injections across groups. After 4.5 days of treatment, refractive errors and axial ocular dimensions were measured. RESULTS: The myopic shifts and axial elongation typical of lens-induced myopia (-15 D lens wear) were inhibited to maxima of 43% (4.5 D) and 52% (0.17 mm) by apomorphine, which, in contrast, enhanced lens-induced hyperopia (refractive error: 114%, 1.55 D; axial length: 134%, 0.16 mm). Inhibitory effects of apomorphine on lens-induced myopia were observed at doses > or = 80 pmole, whereas the doses required to enhance lens-induced hyperopia were 2 log10 units higher. Only a weak inhibitory effect of apomorphine on form-deprivation myopia was observed. Although both apomorphine and atropine inhibited lens-induced myopia, atropine was slightly more effective for the doses compared (refractive error, 53% cf. 32%), and the effect of the combination was not significantly greater than that of atropine alone (refractive error, 59% cf. 53%). CONCLUSIONS: Apomorphine inhibits both types of experimental myopia, which implies the involvement of dopaminergic mechanisms in both phenomena; likewise, cholinergic mechanisms are indicated by the inhibitory effects of atropine on both lens-induced myopia and form-deprivation myopia. We speculate that apomorphine and atropine act at different sites on a common control pathway because the combined effect of apomorphine and atropine was no more than atropine alone.

Animals↗
PubMed2001

[Biometric variation of the ocular globe in myopia].

GOAL: The study of correlation between myopia's pathogen and the biometrics variations of the different eye ball segments. MATERIAL AND METHOD: 64 patients were included in this study: 54 patients with myopia higher than--5 diopter and 10 patients with cataracta. All patients underwent a complete ocular examination including: visual acuity determination, ocular fundus examination, automatic refractometry, keratometry. Biometry was performed with an ultra-scan system. RESULTS: From 64 patients, 53 were with axial myopia, 1 with myopia induced by low corneal curvature radius and 10 patients with myopia induced by a high refractive index of the lens caused by cataract. In cases with axial myopia the axial length was high (26.1 mm) with a high vitreous length (20.78 mm). In cases with index myopia, only the lens thickness and the anterior chamber depth undergo biometrics variations. Curvature myopia is the result of the decrease of the corneal curvature radius. CONCLUSIONS: Axial myopia is that by far the most frequently form of myopia. In this case the increases in axial length is proportionally with the degree of myopia. Index myopia is produced by the increase of the refractive index of the lens in cataract. A low corneal curvature radius less frequently than the others produces curvature myopia.

Adolescent↗
PubMed2004

[A study on difference of ocular motor parameters in myopia].

OBJECTIVE: This study sought to assess the difference of these ocular motor parameters in myopia onset and development were explored. METHODS: 31 emmetropia and 46 myopia adult subjects were included in this study. The myopia subjects were divided into three groups as mild myopia, moderate myopia and high myopia. Phoria at distance and near, positive and negative relative accommodation (NRA/PRA) were measured. Accommodative convergence and accommodation stimulus ratio (AC/A) was determined through phoria values' calculation. RESULTS: Calculated AC/A of myopia was higher than that of emmetropia, and there were trends of elevated AC/A with myopia power increasing. There was significant difference in phoria in near between the myopia group and emmetropia group, but none in that of distance. There was no significant difference in NRA. However, PRA of myopia was lower than that of the emmetropia (P <0.05). CONCLUSIONS: Ocular motor parameters are different in myopia eyes. AC/A is one of key parameters among them, and AC/A is increased in myopia, which indicates out of focus of retinal image in the developing myopia.

Accommodation, Ocular↗
PubMed1995

The utility of three predictors of childhood myopia: a Bayesian analysis.

Any treatment to prevent the onset of juvenile myopia will require predictive tests in order to determine which children should receive treatment. Three risk factors for myopia were evaluated for their ability to predict myopia: (a) refraction at school entry; (b) refraction in infancy; and (c) parental history of myopia. Bayes' theorem was used to estimate these conditional probabilities. Refraction at school entry had twice the power to predict myopia (probability of juvenile myopia given the child is near emmetropia at school entry = 0.53) compared to either infant refraction (0.21-0.28) or parental myopia (0.20-0.25). While a history of any parent having myopia had the highest test sensitivity (probability of a positive family history of myopia given juvenile myopia in the child = 0.90) and refraction at school entry the highest test specificity (probability of more hyperopia than +0.50 D at school entry given no juvenile myopia = 0.91), none of these three factors had high values for both sensitivity and specificity. Further work is required to develop a battery of tests which could predict the onset of juvenile myopia with both adequate sensitivity and specificity.

Age Factors↗