Women have slightly poorer eyesight than men
Researchers evaluated VF in 491 adults (mean age 52.9±5.90 years) participating in the population-based Singapore Chinese Eye Study. A total of 800 VF assessments were performed in 655 eligible eyes. Mean deviation (MD) and pattern standard deviation (PSD), indices of vision loss, were analysed according to sex.
There was a slight male predominance (n=262; mean age 53.27±6.24 years; female: mean age 52.48±5.48 years), though the duration of the VF test tended to be longer in women (p=0.01). Both sexes were comparable in terms of age, educational attainment, best-corrected visual acuity and VF reliability indices. [Ophthalmic Epidemiol 2019;doi:10.1080/09286586.2019.1568505]
In terms of ophthalmic examination measurements, women showed significantly higher intraocular pressure (14.8±2.8 vs 14.0±2.8 mm Hg; p=0.01), shorter axial length (23.58±1.01 vs 24.23±1.08 mm; p<0.001) and denser nuclear sclerotic lens opacity (1.94±0.51 vs 1.84±0.50; p=0.01).
Importantly, MD was significantly lower in women than in men (–0.84±1.20 vs –0.45±1.01; p<0.001), while PSD was statistically similar between groups (1.63±0.44 vs 1.58±0.37; p=0.14).
Multivariable linear regression analysis further confirmed that in the overall study population, the female sex was associated with significantly lower MD values (β, –0.28; –0.44 to –0.12; p=0.001). This persisted even in analyses stratified according to age (≤50 years: β, –0.26; p=0.025; >50 years: β, –0.30; p=0.009) and nuclear cataract grade (≤2: β, –0.26; p=0.012; >2: β, –0.30; p=0.021).
“Importantly, there was no significant difference in the PSD between the two genders,” said researchers. “This indicates that the lower MD in women is related to a general reduction in height of the tested island of vision, and not due to any focal VF defects, which might otherwise be suggestive of underlying pathology.”
Factors relating to female reproductive health also seemed to play no important role in the observed gender difference in MD. In a subgroup analysis of only women (n=386), more than half were postmenopausal, of whom only 15.9 percent had ever undergone hormone replacement therapy (HRT). Univariate analysis showed that menopause (β, –0.08; p=0.61), age at menopause (β, –0.01; p=0.79) and use of HRT (β, 0.09; p=0.74) were all unrelated to MD.
This conflicts with previous studies, which have reported connections between hormonal variations and poorer ophthalmic findings in women. In the present study, “data for age of menarche, and menstrual cycle-related parameters in menstruating women, however, were not collected,” which may account for these discrepancies, researchers explained. [Ophthalmic Epidemiol 2014;21:1-7; Can J Ophthalmol 2005;40:51-57]
They also note that while the absolute between-gender MD difference of 0.3 dB may seem small, it should not be ignored. This may have “clinical significance as systematically underestimating the degree of glaucomatous VF loss in men on the population scale may lead on average to a higher threshold for the labelling, diagnosis and treatment of glaucoma in men.”
“[F]or instance, this may explain why in real world settings, over several thousands of patients with glaucoma, men have a slightly lower MD compared to women by the time they are first referred to the glaucoma clinic,” researchers said.