AIM:To evaluate the characteristics of ocular biometric parameters and the distribution of corneal astigmatism(CA)in patients with high myopia before cataract surgery.METHODS:A prospective cross-sectional study was conducted, and 695 cataract patients(695 eyes)with high myopia [defined as an axial length(AL)≥26.00 mm] scheduled to undergo cataract surgery at our hospital from January 2022 to December 2024 were consecutively enrolled, another 695 cataract patients(695 eyes)with normal ALs(22.00 mm ≤AL≤25.00 mm)who underwent cataract surgery at our hospital during the same period were included in the control group. For patients with both eyes eligible, the right eye was used for analysis. Before cataract surgery, IOL Master 700 was used to measure the ocular biometric parameters of both eyes for each patient in the two groups. The medical records and ocular biometric data in the two groups were recorded and collected.RESULTS:There were no statistically significant differences between the two groups in genger, age, corneal diameter, and central corneal thickness(all P>0.05). In the high myopia group, the mean AL was 29.20±2.61 mm, and 252 eyes(34.1%)had AL ≥30.00 mm(extremely high myopia). The mean anterior chamber depth(ACD), lens thickness, vitreous chamber depth(VCD), CA, AL/corneal radius of curvature and VCD/AL in the high myopia group were 3.45±0.40, 4.41±0.47, 21.34±2.60 mm, 1.18±0.78 D, 3.79±0.38, and 0.73±0.03, respectively, which were all greater than those in the control group(all P<0.01). In the high myopia group, 350 eyes(50.4%)had CA ≥1.00 D, 192 eyes(27.6%)had CA ≥1.50 D, and 94 eyes(13.5%)had CA ≥2.00 D, which were all higher than those in the control group(32.8%, 15.1%, and 6.6%, respectively; all P<0.001). In the high myopia group, 87 eyes(12.5%)had flat corneas, 424 eyes(61.0%)had moderate CA, and 40 eyes(5.8%)had high CA. These proportions were all higher than those in the control group(6.0%, 46.9%, and 2.9%, respectively; all P<0.001). In the high myopia group, ACD and ACD/AL were negatively correlated with AL(r=-0.162 and -0.661, respectively; all P<0.001), while both ACD and ACD/AL in the control group were positively correlated with AL(r=0.338 and 0.105, respectively; both P<0.01). In the high myopia group, CA increased with age when the patient's age was ≥50 years(r=0.197, P<0.001), which was consistent with the control group.CONCLUSION: The standardized ocular biometric data of cataract patients with high myopia before cataract surgery are helpful for ophthalmologists to accurately calculate the intraocular lens(IOLs)power and select the appropriate IOL type. The majority of high myopia patients need simultaneous correction of CA during cataract surgery.