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Study of the relationship between myopia and personality
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ARCHIVOS DE LA SOCIEDAD ESPAÑOLA DE OFTALMOLOGÍA www.elsevier.es/oftalmologia
Original article
Study of the relationship between myopia and personality夽,夽夽 ˜ a,∗ , F. Pérez Bartolomé a , M. Urriés Ortiz b , P. Arriola Villalobos a,e , I. Rodríguez Una M. Bermúdez Vallecilla a , L. Fernández-Vega Cueto c , C. Martín Villaescusa d , P. Marticorena Álvarez d a
Servicio de Oftalmología, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain b Servicio de Psicología Clínica, Hospital Clínico San Carlos, Madrid, Spain c Centro de Oftalmología Barraquer, Barcelona, Spain d Servicio de Oftalmología, Hospital Universitario de La Princesa, Madrid, Spain e Red Temática de Investigación Cooperativa en Oftalmología (RETICS), Instituto de Salud Carlos III, Madrid, Spain
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objective: To study the correlation between the myopic refractive error and certain person-
Received 2 July 2014
ality traits, and to determine whether there is a correlation between the degree of myopia
Accepted 23 January 2015
and an increased frequency in personality disorders.
Available online xxx
Methods: Cross-sectional observational multicenter study conducted on 82 subjects (26 men, 56 women) age over 18 years with myopia (spherical defect ≤ −0.5 D), with 30 subjects having
Keywords:
high myopia (<−6 D). Data collected: age and gender, academic level, result in the Neo PI-R
Extroversion
personality test, autorefractometry, myopic pathology, and ophthalmological treatment.
Intelligence
Results: Correlation (Spearman’s) between the magnitude of the spherical defect and the 5
High myopia
personality traits studied in the total sample was not statistically significant: neuroticism
Neuroticism
(−0.057; p = .610), extroversion (−0.020; p = .857), openness (−0.032; p = .774), kindness (−0.060;
Personality traits
p = .592), and responsibility (−0.034; p = .765). By dividing them into subgroups of low and high significance (t-test), a significant (p = .002) upward trend of the myopic defect with increasing scores on extraversion was found. When comparing high myopic subjects to the non-high myopic ones, there were significant differences between the 2 groups in terms of the associated pathology (p = .001), received treatment (p = .001) and the level of studies (p = .013). There were no differences in the variables of personality: neuroticism (p = .852), extroversion (p = .199), openness (p = .560), kindness (p = .584), and responsibility (p = .722).
夽 ˜ I, Pérez Bartolomé F, Urriés Ortiz M, Arriola Villalobos P, Bermúdez Vallecilla M, Fernández-Vega Please cite this article as: Rodríguez Una Cueto L, et al. Estudio de la relación entre miopía y personalidad. Arch Soc Esp Oftalmol. 2015. http://dx.doi.org/10.1016/j.oftal.2015.01.005 夽夽 This paper was accepted as a free communication in the 90th Congress of the Ophthalmology Society of Spain, Bilbao, Spain, October 2014. ∗ Corresponding author. ˜ E-mail address: [email protected] (I. Rodríguez Una). ˜ 2173-5794/© 2014 Sociedad Espanola de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.
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Conclusions: A low correlation was found between myopia and personality. There was no difference in the degree of myopia between the groups with different education levels. Subjects with more severe ocular pathology associated with myopia had higher scores in neuroticism, without finding any significant association. ˜ © 2014 Sociedad Espanola de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.
Estudio de la relación entre miopía y personalidad r e s u m e n Palabras clave:
Objetivo: Estudiar la correlación entre el error refractivo miópico y determinados rasgos de
Extraversión
personalidad. Igualmente, se pretende determinar si existe correlación entre el grado
Inteligencia
de miopía y una mayor frecuencia de trastornos de la personalidad.
Miopía magna
Métodos: Estudio transversal observacional multicéntrico. La muestra la formaron 82 sujetos
Neuroticismo
˜ (26 hombres, 56 mujeres) mayores de 18 anos con miopía (defecto esférico ≤ −0.5 D); 30 eran
Rasgos de personalidad
miopes magnos (<−6 D). Datos recogidos: edad y sexo, nivel de formación, resultado en el inventario de personalidad Neo PI-R, autorrefractometría, enfermedad miópica, tratamiento oftalmológico. Resultados: No se encontró correlación (rho de Spearman) estadísticamente significativa entre el defecto esférico y los rasgos de personalidad estudiados en el total de la muestra: neuroticismo (−0.057; p = 0.610), extraversión (−0.020; p = 0.857), apertura (−0.032; p = 0.774), amabilidad (−0.060; p = 0.592), responsabilidad (−0.034; p = 0.765). Al agruparlos por subgrupos de alta y baja significación (t-test), se halló una tendencia al aumento del defecto miópico con la extraversión, que resultó significativa (p = 0.002). Al comparar miopes magnos y el resto, se vio que existían diferencias significativas entre ambos grupos en cuanto a la enfermedad asociada (p < 0.001), el tratamiento recibido (p < 0.001) y el nivel de estudios (p = 0.013), no así en las variables de personalidad: neuroticismo (p = 0.852), extraversión (p = 0.199), apertura (p = 0.560), amabilidad (p = 0.584), responsabilidad (p = 0.722). Conclusiones: Se encontró baja correlación entre miopía y personalidad. El grado de miopía no resultó diferente entre los grupos con diversos niveles de estudios. Los sujetos con enfermedad oftalmológica más grave asociada a la miopía presentaban puntuaciones más altas en neuroticismo, sin asociación significativa. ˜ de Oftalmología. Publicado por Elsevier España, S.L.U. Todos © 2014 Sociedad Espanola los derechos reservados.
Introduction Myopia affects approximately 20–25% of people in the Western world, with higher prevalence in some areas of southeast Asia.1 High myopia is defined as an eye with an axial ocular globe length over 26 mm or a spherical refractive error above 6 diopters (D).2 It affects approximately 2–6% of the general population and 30% of myopic eyes. High myopia expresses as a complex disease with an etiology involving environmental and genetic factors (multifactorial inheritance). This degenerative or pathological myopia is characterized by a progressive and excessive anteroposterior lengthening of the ocular globe, associated to secondary changes involving the sclera, the retina, the choroids and the optic nerve head. Prevalence is higher in adolescence (in the area of 25%) and incidence increases between 5 and 20 years of age. As regards racial
distribution, it has been determined as having the highest prevalence in the Asian population (50–90% in Chinese) and the lowest in the Eskimo population together with American Indians and ethnic Africans. It is twice as frequent in Caucasians (26%) compared to Africans (12%).3 At present, personality is regarded as a complex pattern of deeply rooted psychological characteristics, which are mainly unconscious and difficult to change and express automatically in nearly all areas of people’s lives. For decades, some authors have defended that myopics exhibit distinctive personality traits such as introversion and mistrust.4 However, the psychological implication in myopic subjects is controversial and not well established. Some psychological traits have been considered as typical of myopic Magnus individuals: they tend to be introversive, mistrustful, excessively worried about the condition of the eyesight and eyes, fearful of any alteration, etc. Some authors have even proposed that myopics
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could be actually more intelligent than emmetrope or farsighted individuals and indicated that schooling years and intelligence demonstrated similar specific weight in relation to myopia.5,6 In contrast with the above studies, other papers have indicated that there is no difference in personality traits between myopic and non-myopic subjects, to the point that some studies concluded that there is no such thing as a “myopic personality“.7–10 However, a possible causal relationship between personality and development of myopia could not be discarded entirely, or alternatively the influence of myopia on individual personality and behavior. The objective of the present study is to assess the relationship between myopic refractive defect and specific aspects or traits of personality in myopic subjects. It also endeavors to determine whether there is any correlation between the degree of myopia (growing refractive defect magnitude) and higher frequency or severity of personality disorders.
Material and methods A non-randomized, multicenter, observational and transversal study was designed with the participation of subjects recruited in the Ophthalmology Dept. of the San Carlos Clinical Hospital of Madrid, the Barraquer Ophthalmology Center of Barcelona and the Ophthalmology Dept. of the La Princesa University Hospital of Madrid. The study recruited subjects over 18 years of age with myopia diagnostic (spherical refractive error ≤ −0.5 D). All the subjects signed an informed consent expressing their agreement to participate in the study. In addition, the study was approved by the Ethics Committee of the San Carlos Clinic Hospital of Madrid. The study excluded subjects exhibiting other documented ophthalmological diseases (particularly retinal diseases), large anisoametropia, very high cylinder defect as well as known psychiatric disease. The sample was distributed in 2 study groups: - Non-magnus myopics: between −0.50 D and −6.00 D. - Magnus myopics: <−6.00 D. in this group, information was obtained about subjects exhibiting disorders associated to Magnus myopia (retinal tears, retinal detachment (RD), myopic subretinal neovascular membrane (MNVSR), etc.).
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Examination protocol All the tests were carried out in a single visit. No invasive examinations were performed. - Auto-refractometry: the spherical refractive defect (in D) was measured together with power (in D) and axis (in degrees) of the cylinder refractive defect in both eyes. - Data survey: personal and family data were obtained (age and sex), intellectual factors (education level) and clinical data (ophthalmological disorders associated to myopia: none, retinal tear or rupture, subfoveal/non-foveal SRNVM, RD, peripheral retinal degeneration, ophthalmological treatment: none, argon laser photocoagulation, antiangiogenics intravitreal injection, surgery). All the data were managed confidentially in accordance with Data Protection law. - Personality survey: personality surveys enable an individual assessment of usual behavior, feelings in specific circumstances, core attitudes, interests, etc. The present study utilized the Neo PI-R personality inventory. This standardized questionnaire is one of the best reputed instruments for evaluating personality under normal conditions. The structure of the 5 main personality traits comprised in Neo PI-R has become one of the most endorsed and utilized structures. It comprises 240 elements which are responded in a 5-option Likert scale and enables the assessment of 5 main factors: neuroticism, extroversion, openness, kindness and responsibility (Table 1). The main scales supported by scientific literature are neuroticism and extroversion. Each factor is divided in 6 features which enable a more sophisticated personality analysis with 30 different scores. Survey scores were grouped in accordance with the basis of the survey design. A significance value was attributed to the scores, which were listed as an ordinal scale: very low (1), low (2), normal (3), high (4), very high (5). The data were analyzed for statistical purposes by the SPSS for Windows (version 15.0) application. Mean and standard deviation were applied. The behavior of quantitative variables was analyzed for each categorized diagnostic groups by means of the T for student test (in comparisons of one variable with 2 categories) and the Kruskall–Wallis test (for ordinal variables in comparisons of one variable with more than 2 categories). In all hypothesis crosschecks, null hypotheses was rejected with
Table 1 – Definition of the 5 main personality traits analyzed in the Neo PI-R personality inventory. Factor and scales Neuroticism
Extroversion Opennes to experiences
Affability or kindness Perseverance or responsibility
Description Equivalent to emotional instability and experiencing negative emotional moods. A neurotic is an anxious, worrisome, bad tempered and frequently depressed individual, with possibly poor sleep and psychosomatic disorders This trait involves characteristics such as assertiveness and dynamism Reflects unconventional values and ideas as well as a broad range of interests; this trait refers to people who are open, interested in the inner as well as the outer worlds and whose lives are enriched by experience The ability to be altruistic, compassionate, trusting, sincere and sensitive A tendency to the sense of duty, organization, order, pursuing goals, self-discipline and efficiency. Individuals with these traits are strong-willed, scrupulous, punctual and reliable, and are able to control their impulses
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Table 2 – Demographic and clinical characteristics of the overall sample and the studied groups. Overall sample (n = 82) Males, n (%) Females, n (%) Mean age in years Males Females Overall
Myopics magnus (n = 30)
Myopics non-magnus (n = 52)
26 (31.7%) 56 (68.3%)
5 (17.86%) 25 (83.33%)
20 (38.46%) 32 (61.54%)
42.15 ± 14.48 [23, 67] 38.00 ± 15.85 [21, 77] 39.32 ± 15.59 [21, 77]
46.40 ± 12.40 [39, 67] 43.15 ± 18.37 [23, 77] 43.67 ± 17.39 [23, 77]
41.14 ± 15.57 [23, 72] 33.74 ± 12.26 [21, 60] 36.73 ± 14.04 [21, 72]
Mean spherical defect (D) Males Females Overall
−5.18 ± 4.91 [−20.50; −0.75] −6.05 ± 6.20 [−28; −0.50] −6.12 ± 5.92 [−28; −0.50]
−15.30 ± 4.60 [−20.50; −10.50] −11.60 ± 6.69 [−28; −6] −12.20 ± 6.52 [−28; −6]
−2.90 ± 1.32 [−4.75; −0.75] −2.91 ± 1.45 [−5.50; −0.50] −2.90 ± 1.44 [−5.50; −0.50]
Mean cylinder defect (D) Males Females Overall
−0.39 ± 0.77 [−2.50; 0] −0.39 ± 0.79 [−3.50; 0] −0.39 ± 0.79 [−2.50; 0]
−0.81 ± 1.07 [−2.25; 0] −0.53 ± 2.28 [−3.50; 0] −0.57 ± 1.00 [−3.50; 0]
−0.30 ± 0.70 [−2.5; 0] −0.29 ± 0.60 [−2.5; 0] −0.52 ± 0.63 [−2.5; 0]
D: dioptre. Ranges indicated between brackets [minimum value; maximum value].
a type I or ␣ error below 0.05. In the correlation analysis, the Spearman rho correlation coefficient was calculated for study variables.
Results The overall sample comprised 82 subjects. Descriptive analysis is shown in Table 2. After verifying that the absence of statistically significant differences in sphere and cylinder values between both eyes, the refractive values of the right eyes were utilized for the statistical study by consensus (anisometropia constituted one of the study exclusion criteria).
Correlations Table 3 shows the rho Spearman correlations between the spherical refractive error magnitude and the 5 personality traits of the study in the overall sample. None of the values was statistically significant. In a more detailed individual analysis and looking for specific situations, it was observed that the only psychological variable demonstrating very high significance values (5) was neuroticism in 2 subjects: one exhibited a sphere of −18.5 D the other −5 D. In the remaining psychological variables, the
Table 3 – Correlation (Spearman) between sphere magnitude and personality traits studied in the entire sample. Variable Neuroticism Extroversion Opennes Kindness Responsibility
r
p
−0.057 −0.020 −0.032 −0.060 −0.034
0.610 0.857 0.774 0.592 0.765
highest significant score was 4 (high), obtaining in all subjects normal significance values (3), low (2) and very low (1). Table 4 shows the comparison of overall sample mean values, considering all the values that the different psychological variables could assume (Kruskal–Wallis test). An analysis (t-test) was carried out comparing the results of 2 grouped sets: a first subgroup formed by subjects obtaining high (4) or very high (5) significance values in the psychological test against a subgroup comprising those with normal (3), low (2) and very low (1) significance. The results are shown below: - Neuroticism (4 + 5 vs 1 + 2 + 3): statistically not significant differences (p = 0.402). The graph shows a certain tendency to increased myopic spherical defect together with increased scale of neuroticism, which was not significant (Fig. 1). - Extroversion (4 vs 1 + 2 + 3): statistically significant differences (p = 0.002). The graph shows a clear tendency toward increased myopic spherical defect together with increase in the extroversion scale, which was significant (Fig. 1). - Openness (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.448). - Kindness (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.291). - Responsibility (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.376). In what concerns the study of diseases associated to myopia, one of the 2 subjects that scored highest in neuroticism did not have associated diseases and the other exhibited a retinal tear. The diseases considered to be more severe (SRNVM and RD) occurred in 14 subjects, 35.71% of which obtained high significance in neuroticism, 14.29% obtained high significance in extroversion, 21.43% obtained high significance in openness, 7.14% obtained high significance in kindness and 7.14% obtained high significance in responsibility. Accordingly, the psychological variable which exhibited
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Table 4 – mean overall sample comparison study, distributed per each psychological variable of the study. Signification
Mean ± SD
No.
Neuroticism: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the neuroticism scale (p = 0.479) 41 −6.74 ± 7.14 Normal 39 −5.32 ± 4.01 High 2 −11.75 ± 9.55 Very high 82 −6.19 ± 5.92 Total Extroversion: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the extroversion scale (p = 0.151). The subjects with the most negative sphere values exhibited higher scores for extroversion Very low 1 −7.50 ± 0.00 −6.36 ± 6.63 Low 30 45 −5.08 ± 4.35 Normal 6 −13.38 ± 9.87 High Total 82 −6.19 ± 5.92 Openness: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the openness scale (p = 0.415) 1 −20.50 ± 0.00 Very low 25 −4.99 ± 4.12 Low 47 −6.24 ± 6.09 Normal 9 −7.61 ± 7.65 High 82 −6.19 ± 5.92 Total Kindness: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the kindness scale (p = 0.824) 2 −10.13 ± 11.84 Very low 30 −4.97 ± 3.45 Low 47 −6.57 ± 6.74 Normal 3 −9.75 ± 8.60 High 82 −6.19 ± 5.92 Total Responsibility: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the responsibility scale (p = 0.300) 1 −1.00 ± 00.00 Very low 33 −5.35 ± 4.22 Low 43 −7.22 ± 7.07 Normal 5 −3.90 ± 3.56 High 82 −6.19 ± 5.92 Total
Table 5 – Mean sphere and cylinder refractive defects in the overall sample subjects with higher education levels. n Education level of 6 or higher
57 (18 males, 39 females)
Mean age (years) 34.5 ± 13.36
the highest percentage of subjects with severe disease and high significance in the scores was neuroticism (35.71%), albeit without finding statistical significance. The results of the study concerning the relationship between academic training/level of education and myopia are shown in Fig. 2 and Table 5. The analysis based on degree of myopia (Table 6), revealed the existence of differences between both groups in what concerns associated disease, treatments received an education levels. No statistically significant differences were found in the studied personality variables.
Discussion In 2008, van de Berg et al. carried out a study with twins recruited in Australia who filled in an International Personality
Mean sphere value (D)
Mean cylinder value (D)
(−4.59) ± 3.90
(−0.47) ± (−1.31)
Table 6 – Comparison (t-test) of the difference variables of the study between the myopics Magnus and myopics non-Magnus. p Demographic variable Disease Treatment Education level Personality variable Neuroticism Extroversion Opennes Kindness Responsibility ∗ ∗∗
p < 0.05. p < 0.01.
<0.001** <0.001** 0.013* 0.852 0.199 0.560 0.584 0.722
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Fig. 1 – Graphic representation of the Bland–Altman diagrams comparing spherical Al refract defect with each one of the personality traits studied in the overall sample.
Item Pool (IPIP) questionnaire which studied the 5 main personality groups in the same way as in the present study. The correlation and regression results for personality in both study groups after multivariate analysis did not sustain myopic
individuals being introversive. However, a small but significant association was found between myopia and kindness (r = 0.08; p < 0.05). In the multivariate analysis including age, sex, education and said 5 personality traits, openness was
Education level
D
Compulsory High school Vocational Technical Superior Ph.D diploma training Certification Graduate Master Secondary Basic (3) module (4) studies (5) studies (6) engineer (7) engineer (8) studies (9) studies (10) education (1) Ed. (1) 0
-2
-4
-6
-8
-10
-12
Fig. 2 – Bar diagram illustrating the mean spherical refractive error in each one of the sample groups, classified by education levels.
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the only significant myopia trait in the studied groups.1 As in the above-mentioned studies, it could be concluded that the belief maintained for many years that myopic individuals are introversive could be a reflection of stereotypes related to intelligence instead of actually correlations. In a literature review, Lanyon and Giddings concluded that myopics tend to be more introversive and exhibit higher tolerance to anxiety than non-myopics.4 Beedle and Young reaffirmed these findings after studying 782 psychology students. However, their ocular classification was based on a self-assessment instead of objective observation.11 In a more detailed study, Baldwin also concluded that there seems to be a relationship between myopia and introversion, reflexiveness and self-confidence, in opposition to farsighted individuals: extroversion and preference for more openness.12 Lauriola studied the same 5 personality traits in 88 subjects (3.5% ametrope; 46.9% myopic; 24.5% farsighted; 24.5% with astigmatism) and obtained low but significant correlations between refractive error and extroversion (r = 0.15), openness (r = 0.12) and responsibility (r = −0.24), with data higher than those of the present study.13 In contrast with the above reviews and studies, other publications have demonstrated the absence of differences in personality traits between myopics and non-myopics.1 The findings of the present study are along this same line due to the fact that no statistically significant differences were found between the scores of the various personality traits when analyzing the groups separately. However, when the subjects were divided in high and low significance subgroups, significance was found in extroversion. In a more detailed individual analysis looking for specific situations, it was observed that the only psychological variable showing very high significance values was neuroticism, portrayed by 2 subjects: one exhibited sphere of −18.5 D and the other −5 D, which evidenced a higher frequency of Magnus myopia in this case. These results match those of Bullimore10 in a study carried out on optometric students in California University, which did not find significant personality differences between groups with different refractive defects.10 Even in studies with more powerful designs such as a prospective study of an Italian group, in 57 university students (39 myopic and 18 ametropic/farsighted) it was seen that the personality profile and psychophysical stress did not play a primary pathogenic role in myopia.7 It has been proposed that in general myopics are more intelligent than non-myopics. This association was attributed to a biological relationship between the growth of the eye and the development of the brain. However, the authors of these studies concluded that the myopic components are a latent phenotype: myopia would not express if some predisposing external factor did not exist. In 1987, Rosner and Belkin observed a strong association between myopia and schooling years.14 The prevalence of myopia was significantly higher in subjects with longer education periods. In the sample of the present study said association was not observed. As can be seen in Table 5, the subjects who exhibited a higher academic training level (university graduates or higher) and therefore spent more years in education, exhibited sphere values below those considered to be Magnus myopia (−4.59 ± 3.90 D). Even
7
so, it must be taken into account that the level of intelligence could become a factor of confusion. Myopic subjects score relatively high in intellectual quotient measures and educational development,5 although intelligent people are usually considered to be more introversive, reserved and disciplined. Myopic individuals could exhibit these traits because they are usually regarded as intelligent. One of the limitations of the present study is the absence of visual acuity data, which were not collected in the examination and could have an influence in the emotional condition of subjects. However, the majority of previous similar studies did not obtain said data either. It could be interesting to carry out a case and control study, selecting the cases between a group of subjects with known psychological alterations or diagnosed personality disorders, and examining them ophthalmologically in order to identify myopia. Increasing the sample size or adding multivariate analysis could improve the statistical power. By way of conclusion, the present study has found low correlations in our environment between myopia and described personality traits. A greater tendency to extroversion was observed in myopic individuals of the analyzed sample, which increased together with the degree of myopia. Even so, the results do not establish a significant association between both variables. The subjects with more severe ophthalmological disease associated to myopia exhibited higher scores in neuroticism but without obtaining a significant association. Similarly, myopia degrees were not different between groups with different levels of education.
Conflict of interests No conflict of interests has been declared by the authors.
references
1. Van de Berg R, Dirani M, Chen CY, Haslam N, Baird PN. Myopia and personality: the genes in myopia (GEM) personality study. Invest Ophthalmol Vis Sci. 2008;49:882–6. 2. Kanski J. Oftalmología clínica. Elsevier; 2009. p. 644–6. 3. Gold D, Lewis R. Oftalmología. Marbán: American Medical Association; 2002. 4. Lanyon R, Giddings J. Psychological approaches to myopia: a review. Am J Optom Physiol Opt. 1974;4:271–81. 5. Saw SM, Tan SB, Fung D, Chia KS, Koh D, Tan DT, et al. IQ and the association with myopia in children. Invest Ophthalmol Vis Sci. 2004;45:2943–8. 6. Miller EM. On the correlation of myopia and intelligence. Genet Soc Gen Psychol Monogr. 1992;118:361–83. 7. Angi M, Rupolo G, de Bertolini C, Bisantis C. Personality, psychological stress, and myopia progression. Graefes Arch Clin Exp Ophthalmol. 1993;231:136–40. 8. Gawron V. Ocular accommodation, personality, and autonomic balance. Am J Optom Physiol Opt. 1983;60:630–9. 9. Gawron V. Differences among myopes, emmetropes and hyperopes. Am J Optom Physiol Opt. 1981;58:753–60. 10. Bullimore M, Conway R, Nakash A. Myopia in optometry students: family history, age of onset and personality. Ophthalmic Physiol Opt. 1989;9:284–8.
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11. Beedle S, Young F. Values, personality, physical characteristics, and refractive error. Am J Optom Physiol Opt. 1976;53:735–9. 12. Baldwin WR. A review of statistical studies of relations between myopia and ethnic, behavioral, and physiological characteristics. Am J Optom Physiol Opt. 1981;58:516–27.
13. Lauriola M. Psychological correlates of eye refractive errors. Personal Indiv Diff. 1997;23:917–20. 14. Rosner M, Belkin M. Intelligence education, and myopia in males. Arch Ophthalmol. 1987;105:1508–11.
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Original article
Study of the relationship between myopia and personality夽,夽夽 ˜ a,∗ , F. Pérez Bartolomé a , M. Urriés Ortiz b , P. Arriola Villalobos a,e , I. Rodríguez Una M. Bermúdez Vallecilla a , L. Fernández-Vega Cueto c , C. Martín Villaescusa d , P. Marticorena Álvarez d a
Servicio de Oftalmología, Hospital Clínico San Carlos, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Madrid, Spain b Servicio de Psicología Clínica, Hospital Clínico San Carlos, Madrid, Spain c Centro de Oftalmología Barraquer, Barcelona, Spain d Servicio de Oftalmología, Hospital Universitario de La Princesa, Madrid, Spain e Red Temática de Investigación Cooperativa en Oftalmología (RETICS), Instituto de Salud Carlos III, Madrid, Spain
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objective: To study the correlation between the myopic refractive error and certain person-
Received 2 July 2014
ality traits, and to determine whether there is a correlation between the degree of myopia
Accepted 23 January 2015
and an increased frequency in personality disorders.
Available online xxx
Methods: Cross-sectional observational multicenter study conducted on 82 subjects (26 men, 56 women) age over 18 years with myopia (spherical defect ≤ −0.5 D), with 30 subjects having
Keywords:
high myopia (<−6 D). Data collected: age and gender, academic level, result in the Neo PI-R
Extroversion
personality test, autorefractometry, myopic pathology, and ophthalmological treatment.
Intelligence
Results: Correlation (Spearman’s) between the magnitude of the spherical defect and the 5
High myopia
personality traits studied in the total sample was not statistically significant: neuroticism
Neuroticism
(−0.057; p = .610), extroversion (−0.020; p = .857), openness (−0.032; p = .774), kindness (−0.060;
Personality traits
p = .592), and responsibility (−0.034; p = .765). By dividing them into subgroups of low and high significance (t-test), a significant (p = .002) upward trend of the myopic defect with increasing scores on extraversion was found. When comparing high myopic subjects to the non-high myopic ones, there were significant differences between the 2 groups in terms of the associated pathology (p = .001), received treatment (p = .001) and the level of studies (p = .013). There were no differences in the variables of personality: neuroticism (p = .852), extroversion (p = .199), openness (p = .560), kindness (p = .584), and responsibility (p = .722).
夽 ˜ I, Pérez Bartolomé F, Urriés Ortiz M, Arriola Villalobos P, Bermúdez Vallecilla M, Fernández-Vega Please cite this article as: Rodríguez Una Cueto L, et al. Estudio de la relación entre miopía y personalidad. Arch Soc Esp Oftalmol. 2015. http://dx.doi.org/10.1016/j.oftal.2015.01.005 夽夽 This paper was accepted as a free communication in the 90th Congress of the Ophthalmology Society of Spain, Bilbao, Spain, October 2014. ∗ Corresponding author. ˜ E-mail address: [email protected] (I. Rodríguez Una). ˜ 2173-5794/© 2014 Sociedad Espanola de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.
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Conclusions: A low correlation was found between myopia and personality. There was no difference in the degree of myopia between the groups with different education levels. Subjects with more severe ocular pathology associated with myopia had higher scores in neuroticism, without finding any significant association. ˜ © 2014 Sociedad Espanola de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.
Estudio de la relación entre miopía y personalidad r e s u m e n Palabras clave:
Objetivo: Estudiar la correlación entre el error refractivo miópico y determinados rasgos de
Extraversión
personalidad. Igualmente, se pretende determinar si existe correlación entre el grado
Inteligencia
de miopía y una mayor frecuencia de trastornos de la personalidad.
Miopía magna
Métodos: Estudio transversal observacional multicéntrico. La muestra la formaron 82 sujetos
Neuroticismo
˜ (26 hombres, 56 mujeres) mayores de 18 anos con miopía (defecto esférico ≤ −0.5 D); 30 eran
Rasgos de personalidad
miopes magnos (<−6 D). Datos recogidos: edad y sexo, nivel de formación, resultado en el inventario de personalidad Neo PI-R, autorrefractometría, enfermedad miópica, tratamiento oftalmológico. Resultados: No se encontró correlación (rho de Spearman) estadísticamente significativa entre el defecto esférico y los rasgos de personalidad estudiados en el total de la muestra: neuroticismo (−0.057; p = 0.610), extraversión (−0.020; p = 0.857), apertura (−0.032; p = 0.774), amabilidad (−0.060; p = 0.592), responsabilidad (−0.034; p = 0.765). Al agruparlos por subgrupos de alta y baja significación (t-test), se halló una tendencia al aumento del defecto miópico con la extraversión, que resultó significativa (p = 0.002). Al comparar miopes magnos y el resto, se vio que existían diferencias significativas entre ambos grupos en cuanto a la enfermedad asociada (p < 0.001), el tratamiento recibido (p < 0.001) y el nivel de estudios (p = 0.013), no así en las variables de personalidad: neuroticismo (p = 0.852), extraversión (p = 0.199), apertura (p = 0.560), amabilidad (p = 0.584), responsabilidad (p = 0.722). Conclusiones: Se encontró baja correlación entre miopía y personalidad. El grado de miopía no resultó diferente entre los grupos con diversos niveles de estudios. Los sujetos con enfermedad oftalmológica más grave asociada a la miopía presentaban puntuaciones más altas en neuroticismo, sin asociación significativa. ˜ de Oftalmología. Publicado por Elsevier España, S.L.U. Todos © 2014 Sociedad Espanola los derechos reservados.
Introduction Myopia affects approximately 20–25% of people in the Western world, with higher prevalence in some areas of southeast Asia.1 High myopia is defined as an eye with an axial ocular globe length over 26 mm or a spherical refractive error above 6 diopters (D).2 It affects approximately 2–6% of the general population and 30% of myopic eyes. High myopia expresses as a complex disease with an etiology involving environmental and genetic factors (multifactorial inheritance). This degenerative or pathological myopia is characterized by a progressive and excessive anteroposterior lengthening of the ocular globe, associated to secondary changes involving the sclera, the retina, the choroids and the optic nerve head. Prevalence is higher in adolescence (in the area of 25%) and incidence increases between 5 and 20 years of age. As regards racial
distribution, it has been determined as having the highest prevalence in the Asian population (50–90% in Chinese) and the lowest in the Eskimo population together with American Indians and ethnic Africans. It is twice as frequent in Caucasians (26%) compared to Africans (12%).3 At present, personality is regarded as a complex pattern of deeply rooted psychological characteristics, which are mainly unconscious and difficult to change and express automatically in nearly all areas of people’s lives. For decades, some authors have defended that myopics exhibit distinctive personality traits such as introversion and mistrust.4 However, the psychological implication in myopic subjects is controversial and not well established. Some psychological traits have been considered as typical of myopic Magnus individuals: they tend to be introversive, mistrustful, excessively worried about the condition of the eyesight and eyes, fearful of any alteration, etc. Some authors have even proposed that myopics
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could be actually more intelligent than emmetrope or farsighted individuals and indicated that schooling years and intelligence demonstrated similar specific weight in relation to myopia.5,6 In contrast with the above studies, other papers have indicated that there is no difference in personality traits between myopic and non-myopic subjects, to the point that some studies concluded that there is no such thing as a “myopic personality“.7–10 However, a possible causal relationship between personality and development of myopia could not be discarded entirely, or alternatively the influence of myopia on individual personality and behavior. The objective of the present study is to assess the relationship between myopic refractive defect and specific aspects or traits of personality in myopic subjects. It also endeavors to determine whether there is any correlation between the degree of myopia (growing refractive defect magnitude) and higher frequency or severity of personality disorders.
Material and methods A non-randomized, multicenter, observational and transversal study was designed with the participation of subjects recruited in the Ophthalmology Dept. of the San Carlos Clinical Hospital of Madrid, the Barraquer Ophthalmology Center of Barcelona and the Ophthalmology Dept. of the La Princesa University Hospital of Madrid. The study recruited subjects over 18 years of age with myopia diagnostic (spherical refractive error ≤ −0.5 D). All the subjects signed an informed consent expressing their agreement to participate in the study. In addition, the study was approved by the Ethics Committee of the San Carlos Clinic Hospital of Madrid. The study excluded subjects exhibiting other documented ophthalmological diseases (particularly retinal diseases), large anisoametropia, very high cylinder defect as well as known psychiatric disease. The sample was distributed in 2 study groups: - Non-magnus myopics: between −0.50 D and −6.00 D. - Magnus myopics: <−6.00 D. in this group, information was obtained about subjects exhibiting disorders associated to Magnus myopia (retinal tears, retinal detachment (RD), myopic subretinal neovascular membrane (MNVSR), etc.).
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Examination protocol All the tests were carried out in a single visit. No invasive examinations were performed. - Auto-refractometry: the spherical refractive defect (in D) was measured together with power (in D) and axis (in degrees) of the cylinder refractive defect in both eyes. - Data survey: personal and family data were obtained (age and sex), intellectual factors (education level) and clinical data (ophthalmological disorders associated to myopia: none, retinal tear or rupture, subfoveal/non-foveal SRNVM, RD, peripheral retinal degeneration, ophthalmological treatment: none, argon laser photocoagulation, antiangiogenics intravitreal injection, surgery). All the data were managed confidentially in accordance with Data Protection law. - Personality survey: personality surveys enable an individual assessment of usual behavior, feelings in specific circumstances, core attitudes, interests, etc. The present study utilized the Neo PI-R personality inventory. This standardized questionnaire is one of the best reputed instruments for evaluating personality under normal conditions. The structure of the 5 main personality traits comprised in Neo PI-R has become one of the most endorsed and utilized structures. It comprises 240 elements which are responded in a 5-option Likert scale and enables the assessment of 5 main factors: neuroticism, extroversion, openness, kindness and responsibility (Table 1). The main scales supported by scientific literature are neuroticism and extroversion. Each factor is divided in 6 features which enable a more sophisticated personality analysis with 30 different scores. Survey scores were grouped in accordance with the basis of the survey design. A significance value was attributed to the scores, which were listed as an ordinal scale: very low (1), low (2), normal (3), high (4), very high (5). The data were analyzed for statistical purposes by the SPSS for Windows (version 15.0) application. Mean and standard deviation were applied. The behavior of quantitative variables was analyzed for each categorized diagnostic groups by means of the T for student test (in comparisons of one variable with 2 categories) and the Kruskall–Wallis test (for ordinal variables in comparisons of one variable with more than 2 categories). In all hypothesis crosschecks, null hypotheses was rejected with
Table 1 – Definition of the 5 main personality traits analyzed in the Neo PI-R personality inventory. Factor and scales Neuroticism
Extroversion Opennes to experiences
Affability or kindness Perseverance or responsibility
Description Equivalent to emotional instability and experiencing negative emotional moods. A neurotic is an anxious, worrisome, bad tempered and frequently depressed individual, with possibly poor sleep and psychosomatic disorders This trait involves characteristics such as assertiveness and dynamism Reflects unconventional values and ideas as well as a broad range of interests; this trait refers to people who are open, interested in the inner as well as the outer worlds and whose lives are enriched by experience The ability to be altruistic, compassionate, trusting, sincere and sensitive A tendency to the sense of duty, organization, order, pursuing goals, self-discipline and efficiency. Individuals with these traits are strong-willed, scrupulous, punctual and reliable, and are able to control their impulses
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Table 2 – Demographic and clinical characteristics of the overall sample and the studied groups. Overall sample (n = 82) Males, n (%) Females, n (%) Mean age in years Males Females Overall
Myopics magnus (n = 30)
Myopics non-magnus (n = 52)
26 (31.7%) 56 (68.3%)
5 (17.86%) 25 (83.33%)
20 (38.46%) 32 (61.54%)
42.15 ± 14.48 [23, 67] 38.00 ± 15.85 [21, 77] 39.32 ± 15.59 [21, 77]
46.40 ± 12.40 [39, 67] 43.15 ± 18.37 [23, 77] 43.67 ± 17.39 [23, 77]
41.14 ± 15.57 [23, 72] 33.74 ± 12.26 [21, 60] 36.73 ± 14.04 [21, 72]
Mean spherical defect (D) Males Females Overall
−5.18 ± 4.91 [−20.50; −0.75] −6.05 ± 6.20 [−28; −0.50] −6.12 ± 5.92 [−28; −0.50]
−15.30 ± 4.60 [−20.50; −10.50] −11.60 ± 6.69 [−28; −6] −12.20 ± 6.52 [−28; −6]
−2.90 ± 1.32 [−4.75; −0.75] −2.91 ± 1.45 [−5.50; −0.50] −2.90 ± 1.44 [−5.50; −0.50]
Mean cylinder defect (D) Males Females Overall
−0.39 ± 0.77 [−2.50; 0] −0.39 ± 0.79 [−3.50; 0] −0.39 ± 0.79 [−2.50; 0]
−0.81 ± 1.07 [−2.25; 0] −0.53 ± 2.28 [−3.50; 0] −0.57 ± 1.00 [−3.50; 0]
−0.30 ± 0.70 [−2.5; 0] −0.29 ± 0.60 [−2.5; 0] −0.52 ± 0.63 [−2.5; 0]
D: dioptre. Ranges indicated between brackets [minimum value; maximum value].
a type I or ␣ error below 0.05. In the correlation analysis, the Spearman rho correlation coefficient was calculated for study variables.
Results The overall sample comprised 82 subjects. Descriptive analysis is shown in Table 2. After verifying that the absence of statistically significant differences in sphere and cylinder values between both eyes, the refractive values of the right eyes were utilized for the statistical study by consensus (anisometropia constituted one of the study exclusion criteria).
Correlations Table 3 shows the rho Spearman correlations between the spherical refractive error magnitude and the 5 personality traits of the study in the overall sample. None of the values was statistically significant. In a more detailed individual analysis and looking for specific situations, it was observed that the only psychological variable demonstrating very high significance values (5) was neuroticism in 2 subjects: one exhibited a sphere of −18.5 D the other −5 D. In the remaining psychological variables, the
Table 3 – Correlation (Spearman) between sphere magnitude and personality traits studied in the entire sample. Variable Neuroticism Extroversion Opennes Kindness Responsibility
r
p
−0.057 −0.020 −0.032 −0.060 −0.034
0.610 0.857 0.774 0.592 0.765
highest significant score was 4 (high), obtaining in all subjects normal significance values (3), low (2) and very low (1). Table 4 shows the comparison of overall sample mean values, considering all the values that the different psychological variables could assume (Kruskal–Wallis test). An analysis (t-test) was carried out comparing the results of 2 grouped sets: a first subgroup formed by subjects obtaining high (4) or very high (5) significance values in the psychological test against a subgroup comprising those with normal (3), low (2) and very low (1) significance. The results are shown below: - Neuroticism (4 + 5 vs 1 + 2 + 3): statistically not significant differences (p = 0.402). The graph shows a certain tendency to increased myopic spherical defect together with increased scale of neuroticism, which was not significant (Fig. 1). - Extroversion (4 vs 1 + 2 + 3): statistically significant differences (p = 0.002). The graph shows a clear tendency toward increased myopic spherical defect together with increase in the extroversion scale, which was significant (Fig. 1). - Openness (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.448). - Kindness (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.291). - Responsibility (4 vs 1 + 2 + 3): statistically not significant differences (p = 0.376). In what concerns the study of diseases associated to myopia, one of the 2 subjects that scored highest in neuroticism did not have associated diseases and the other exhibited a retinal tear. The diseases considered to be more severe (SRNVM and RD) occurred in 14 subjects, 35.71% of which obtained high significance in neuroticism, 14.29% obtained high significance in extroversion, 21.43% obtained high significance in openness, 7.14% obtained high significance in kindness and 7.14% obtained high significance in responsibility. Accordingly, the psychological variable which exhibited
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Table 4 – mean overall sample comparison study, distributed per each psychological variable of the study. Signification
Mean ± SD
No.
Neuroticism: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the neuroticism scale (p = 0.479) 41 −6.74 ± 7.14 Normal 39 −5.32 ± 4.01 High 2 −11.75 ± 9.55 Very high 82 −6.19 ± 5.92 Total Extroversion: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the extroversion scale (p = 0.151). The subjects with the most negative sphere values exhibited higher scores for extroversion Very low 1 −7.50 ± 0.00 −6.36 ± 6.63 Low 30 45 −5.08 ± 4.35 Normal 6 −13.38 ± 9.87 High Total 82 −6.19 ± 5.92 Openness: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the openness scale (p = 0.415) 1 −20.50 ± 0.00 Very low 25 −4.99 ± 4.12 Low 47 −6.24 ± 6.09 Normal 9 −7.61 ± 7.65 High 82 −6.19 ± 5.92 Total Kindness: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the kindness scale (p = 0.824) 2 −10.13 ± 11.84 Very low 30 −4.97 ± 3.45 Low 47 −6.57 ± 6.74 Normal 3 −9.75 ± 8.60 High 82 −6.19 ± 5.92 Total Responsibility: no statistically significant differences were found in the sphere magnitude between the different groups based on scores for the responsibility scale (p = 0.300) 1 −1.00 ± 00.00 Very low 33 −5.35 ± 4.22 Low 43 −7.22 ± 7.07 Normal 5 −3.90 ± 3.56 High 82 −6.19 ± 5.92 Total
Table 5 – Mean sphere and cylinder refractive defects in the overall sample subjects with higher education levels. n Education level of 6 or higher
57 (18 males, 39 females)
Mean age (years) 34.5 ± 13.36
the highest percentage of subjects with severe disease and high significance in the scores was neuroticism (35.71%), albeit without finding statistical significance. The results of the study concerning the relationship between academic training/level of education and myopia are shown in Fig. 2 and Table 5. The analysis based on degree of myopia (Table 6), revealed the existence of differences between both groups in what concerns associated disease, treatments received an education levels. No statistically significant differences were found in the studied personality variables.
Discussion In 2008, van de Berg et al. carried out a study with twins recruited in Australia who filled in an International Personality
Mean sphere value (D)
Mean cylinder value (D)
(−4.59) ± 3.90
(−0.47) ± (−1.31)
Table 6 – Comparison (t-test) of the difference variables of the study between the myopics Magnus and myopics non-Magnus. p Demographic variable Disease Treatment Education level Personality variable Neuroticism Extroversion Opennes Kindness Responsibility ∗ ∗∗
p < 0.05. p < 0.01.
<0.001** <0.001** 0.013* 0.852 0.199 0.560 0.584 0.722
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0
0
-5
-5
-5
-10
-10
-15 34 8
-20
-25
7516 -15
67 15
-20
26 22 54
8
26
-10 16 -15 15 -20
54
19
-30
19 -30
-30 3
4
5
1
2
Neuroticism 0
-5
-5
RE sphere
40
-10
75 15
-15
67 8 26 22 54
-20
-25
3
4
1
Extroversion
0
34 26
-25
-25
19
RE sphere
RE sphere
0
RE sphere
RE sphere
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2
3
4
Openness 81
37
-10
-15 15 8
-20
34 26 22 54
-25
19
19
-30
-30 2
1
3
Kindness
4
1
2
3
Responsibility
4
Fig. 1 – Graphic representation of the Bland–Altman diagrams comparing spherical Al refract defect with each one of the personality traits studied in the overall sample.
Item Pool (IPIP) questionnaire which studied the 5 main personality groups in the same way as in the present study. The correlation and regression results for personality in both study groups after multivariate analysis did not sustain myopic
individuals being introversive. However, a small but significant association was found between myopia and kindness (r = 0.08; p < 0.05). In the multivariate analysis including age, sex, education and said 5 personality traits, openness was
Education level
D
Compulsory High school Vocational Technical Superior Ph.D diploma training Certification Graduate Master Secondary Basic (3) module (4) studies (5) studies (6) engineer (7) engineer (8) studies (9) studies (10) education (1) Ed. (1) 0
-2
-4
-6
-8
-10
-12
Fig. 2 – Bar diagram illustrating the mean spherical refractive error in each one of the sample groups, classified by education levels.
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the only significant myopia trait in the studied groups.1 As in the above-mentioned studies, it could be concluded that the belief maintained for many years that myopic individuals are introversive could be a reflection of stereotypes related to intelligence instead of actually correlations. In a literature review, Lanyon and Giddings concluded that myopics tend to be more introversive and exhibit higher tolerance to anxiety than non-myopics.4 Beedle and Young reaffirmed these findings after studying 782 psychology students. However, their ocular classification was based on a self-assessment instead of objective observation.11 In a more detailed study, Baldwin also concluded that there seems to be a relationship between myopia and introversion, reflexiveness and self-confidence, in opposition to farsighted individuals: extroversion and preference for more openness.12 Lauriola studied the same 5 personality traits in 88 subjects (3.5% ametrope; 46.9% myopic; 24.5% farsighted; 24.5% with astigmatism) and obtained low but significant correlations between refractive error and extroversion (r = 0.15), openness (r = 0.12) and responsibility (r = −0.24), with data higher than those of the present study.13 In contrast with the above reviews and studies, other publications have demonstrated the absence of differences in personality traits between myopics and non-myopics.1 The findings of the present study are along this same line due to the fact that no statistically significant differences were found between the scores of the various personality traits when analyzing the groups separately. However, when the subjects were divided in high and low significance subgroups, significance was found in extroversion. In a more detailed individual analysis looking for specific situations, it was observed that the only psychological variable showing very high significance values was neuroticism, portrayed by 2 subjects: one exhibited sphere of −18.5 D and the other −5 D, which evidenced a higher frequency of Magnus myopia in this case. These results match those of Bullimore10 in a study carried out on optometric students in California University, which did not find significant personality differences between groups with different refractive defects.10 Even in studies with more powerful designs such as a prospective study of an Italian group, in 57 university students (39 myopic and 18 ametropic/farsighted) it was seen that the personality profile and psychophysical stress did not play a primary pathogenic role in myopia.7 It has been proposed that in general myopics are more intelligent than non-myopics. This association was attributed to a biological relationship between the growth of the eye and the development of the brain. However, the authors of these studies concluded that the myopic components are a latent phenotype: myopia would not express if some predisposing external factor did not exist. In 1987, Rosner and Belkin observed a strong association between myopia and schooling years.14 The prevalence of myopia was significantly higher in subjects with longer education periods. In the sample of the present study said association was not observed. As can be seen in Table 5, the subjects who exhibited a higher academic training level (university graduates or higher) and therefore spent more years in education, exhibited sphere values below those considered to be Magnus myopia (−4.59 ± 3.90 D). Even
7
so, it must be taken into account that the level of intelligence could become a factor of confusion. Myopic subjects score relatively high in intellectual quotient measures and educational development,5 although intelligent people are usually considered to be more introversive, reserved and disciplined. Myopic individuals could exhibit these traits because they are usually regarded as intelligent. One of the limitations of the present study is the absence of visual acuity data, which were not collected in the examination and could have an influence in the emotional condition of subjects. However, the majority of previous similar studies did not obtain said data either. It could be interesting to carry out a case and control study, selecting the cases between a group of subjects with known psychological alterations or diagnosed personality disorders, and examining them ophthalmologically in order to identify myopia. Increasing the sample size or adding multivariate analysis could improve the statistical power. By way of conclusion, the present study has found low correlations in our environment between myopia and described personality traits. A greater tendency to extroversion was observed in myopic individuals of the analyzed sample, which increased together with the degree of myopia. Even so, the results do not establish a significant association between both variables. The subjects with more severe ophthalmological disease associated to myopia exhibited higher scores in neuroticism but without obtaining a significant association. Similarly, myopia degrees were not different between groups with different levels of education.
Conflict of interests No conflict of interests has been declared by the authors.
references
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