Gender differences in horizontal strabismus: Systematic review and meta-analysis shows no difference in prevalence, but gender bias towards females in the clinic

Abstract

Background Strabismus is a misalignment of the visual axis that affects 2-3% of the population and can lead to loss of binocular vision. It is currently controversial whether there is a gender difference in the most common form of visual misalignment: horizontal strabismus. Some studies claimed that more females than males have an outward deviation (exotropia), while others concluded that there is no significant gender difference. No previous work has systematically explored gender differences in horizontal strabismus or has compared the results of population-based studies with those of clinic-based studies. Methods We conducted a systematic review and meta-analysis of studies reporting the prevalence of horizontal strabismus. We included 73 population-based studies and compared their disclosed gender population with that in 141 comparable clinical-based studies. We analysed the data according to gender, strabismus type (esotropia, exotropia), and geographic region/ethnicity. Results Summary statistics showed a nearly identical prevalence of horizontal strabismus (2.558% for males, 2.582% for females), esotropia (1.386% males vs. 1.377% females), and of exotropia (1.035% males vs. 1.043% females). Meta-analysis results showed that these differences between males and females were not statistically significant (odds ratio (OR) = 1.01; 95% confidence interval (CI) = 0.97-1.10), but that females were significantly more frequent (by 7.50%) in clinic-based studies than males, with 5.00% more females for esotropia, and 12.20% more females for exotropia when adjusted for the population’s sex ratio. The extent of the female gender bias differed between geographic regions/societies, with Asians having the lowest bias towards females and Latin American countries having the strongest bias. Conclusions Males and females have the same prevalence of horizontal strabismus, including exotropia. Females with strabismus seek health care or are brought to clinics significantly more often than males. This is an example of gender bias in health care in favour of females rather than males, apparently because parents – erroneously fearing only cosmetic consequences – are more concerned about strabismus in their daughters than their sons. Societal attitudes towards females, as well as economic factors (insurance status), appear to be relevant factors that determine the magnitude of the gender bias in horizontal strabismus.

Prevalence and etiology of strabismus in Down syndrome: A systematic review and meta-analysis with a focus on ethnic differences in the esotropia/exotropia ratio

“…55–56,166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are overall slightly more males than females with Down syndrome.…”

“…[55][56]166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome.…”

Prevalence and etiology of strabismus in Down syndrome: A systematic review and meta-analysis with a focus on ethnic differences in the esotropia/exotropia ratio

“…55–56,166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are overall slightly more males than females with Down syndrome.…”

“…[55][56]166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome.…”

Prevalence and Etiology of Strabismus in Down Syndrome: A Systematic Review and Meta-Analysis with a Focus on Ethnic Differences in the Esotropia/Exotropia Ratio

“…55 – 56 , 166 The bias towards males presumably is due to genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are slightly more males than females with Down syndrome.…”

The global prevalence of horizontal strabismus: a systematic review and meta-analysis with a focus on ethnic variation

“…While there are some reports of a gender difference in horizontal strabismus, mostly of a female bias towards XT, 128,157,170,173,286,291,340,382,404,422,578,579,815 nearly all of these studies were clinicbased and had relatively small cohorts. Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”

“…Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”

Prevalence and etiology of strabismus in Down syndrome: A systematic review and meta-analysis with a focus on ethnic differences in the esotropia/exotropia ratio

“…55–56,166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are overall slightly more males than females with Down syndrome.…”

“…[55][56]166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome.…”

Prevalence and Etiology of Strabismus in Down Syndrome: A Systematic Review and Meta-Analysis with a Focus on Ethnic Differences in the Esotropia/Exotropia Ratio

“…55 – 56 , 166 The bias towards males presumably is due to genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are slightly more males than females with Down syndrome.…”

The global prevalence of horizontal strabismus: a systematic review and meta-analysis with a focus on ethnic variation

“…While there are some reports of a gender difference in horizontal strabismus, mostly of a female bias towards XT, 128,157,170,173,286,291,340,382,404,422,578,579,815 nearly all of these studies were clinicbased and had relatively small cohorts. Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”

“…Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”

Prevalence and etiology of strabismus in Down syndrome: A systematic review and meta-analysis with a focus on ethnic differences in the esotropia/exotropia ratio

“…55–56,166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are overall slightly more males than females with Down syndrome.…”

“…[55][56]166 The bias towards males presumably is because of genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome.…”

Prevalence and Etiology of Strabismus in Down Syndrome: A Systematic Review and Meta-Analysis with a Focus on Ethnic Differences in the Esotropia/Exotropia Ratio

“…55 – 56 , 166 The bias towards males presumably is due to genetic mechanisms (joint segregation of chromosomes 21 and Y). 166 Similar to a previous analysis of gender in strabismus within the normal population, 185 we found no gender difference in the prevalence of strabismus in Down syndrome. There are slightly more males than females with strabismus in Down syndrome, but only because there are slightly more males than females with Down syndrome.…”

The global prevalence of horizontal strabismus: a systematic review and meta-analysis with a focus on ethnic variation

“…While there are some reports of a gender difference in horizontal strabismus, mostly of a female bias towards XT, 128,157,170,173,286,291,340,382,404,422,578,579,815 nearly all of these studies were clinicbased and had relatively small cohorts. Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”

“…Our recent systematic review and meta-analysis of gender in horizontal strabismus 441 found no difference in the prevalence -confirming the conclusions from large-cohort population-based studies 147,343,443 that there is no gender difference in prevalence of strabismus, although there is a significant female bias in the clinic. 441…”