To analyze the distribution characteristics of the anterior corneal astigmatism in 140 000 cataract patients from 18 hospitals in China.

Retrospective study. A total of 143 889 patients (143 889 right eyes) over the age of 40 years with age-related catarac were admitted to 18 Aier eye hospitals in China from July 2015 to October 2018. The average values of the three measurements of the magnitude of anterior corneal astigmatism, the meridian of corneal astigmatism, anterior chamber depth, corneal refractive power, and axial length measured by IOLMaster 500 were obtained. The data acquisition method of each sub-center was to collect and analyze the electronic case data in accordance with the inclusion and exclusion criteria, and to provide them for the sponsor Wuhan Aier Eye Hospital. Non-normal distribution data are presented as M(P₂₅, P₇₅). Mann-Whitney test, Kruskal-Wallis test, Chi-square test were used to analyze the distribution differences of the magnitude of corneal astigmatism and the meridian of corneal astigmatism in gender, age, anterior chamber depth, corneal refractive power and axial length.

Among the 143 889 patients, 84 319 were females and 59 570 were males, the median age was 72 (65, 78) years old, the median corneal astigmatism was 0.84 (0.51, 1.33) D; the corneal astigmatism was ≥0.75 D in 80 895 patients (56.22%) and was ≥1.00 D in 57 304 patients (39.83%). The median corneal astigmatism was 0.87 (0.53, 1.37) D in women and 0.82 (0.50, 1.29) D in men; with statistical difference (U=-14.891; P<0.05). The proportion of with-the-rule (WTR) astigmatism was 33.26% (28 046/84 319) for women and 34.26% (20 408/59 570) for men; The proportion of against-the-rule (ATR) astigmatism was 49.08% (41 385/84 319) for women and 46.91% (27 945/59 570) for men, with statistical difference (χ²=70.913;P<0.05). With the increase of age, the magnitude of corneal astigmatism first decreased from 0.94 (0.57, 1.48) D to 0.75 (0.46, 1.18) D, and then increased to 1.19 (0.74, 1.79) D, with statistical difference (H=1 263.438; P<0.05), and the change was at 61 to 70 years old. With the increase of age, the proportion of WTR astigmatism decreased from 77.50% (396/511) to 12.50% (3/24), the proportion of ATR astigmatism increased from 11.15% (57/511) to 79.07% (34/43), and the proportion of oblique astigmatism changed little from 17.02% (16/94) to 19.92% (245/1 230), the distribution difference was significant (χ²=10 174.496;P<0.05). As the anterior chamber became shallow, the magnitude of corneal astigmatism significantly increased from 0.82 (0.51, 1.31) D to 1.05 (0.61, 1.56) D, and the proportion of ATR astigmatism increased from 47.32% (60 207/127 227) to 51.69% (184/356) (H=409.961, χ²=120.995, both P<0.05). With the corneal refractive power rising, the magnitude of corneal astigmatism increased from 0.80 (0.49, 1.33) D to 0.95 (0.58, 1.53) D, the proportion of ATR astigmatism decreased from 52.84% (4 963/9 392) to 39.97% (9 023/22 577); the difference was significant (H=808.562, χ²=752.147, bothP<0.05). When the axial length was>25.00 mm, the magnitude of corneal astigmatism was highest [1.04 (0.62, 1.65) D], and the proportion of ATR astigmatism was also highest [49.00% (10 964/22 376)]; the difference was significant (H=2 071.198, χ²=131.130, all P<0.05).

The meridian of corneal astigmatism in middle-aged and elderly cataract patients is mainly ATR astigmatism. With the increasing of age, the magnitude of corneal astigmatism decreases first and then increases. The turning point from the proportion of WTR astigmatism to the proportion of ATR astigmatism is 65 years old. The shallower the anterior chamber is, the more the magnitude of corneal astigmatism and the proportion of ATR astigmatism increase. When the axial length is>25.00 mm, both the magnitude of corneal astigmatism and the proportion of ATR astigmatism reach the peak.(Chin J Ophthalmol, 2021, 57: 56-62)

Cataract; Astigmatism; Axial length, eye; Anterior chamber; Age distribution; Sex distribution