Đánh giá vai trò của độ sâu tiền phòng và chiều dày thể thủy tinh trong tính công suất thể thủy tinh nhân tạo

Abstract

Objective: To evaluate the role of chamber depth (ACD) and lens thickness (LT) on the choice of intraocular lens (IOL) calculation and propose the formulas in accordance with per patient. Subject and method: A prospective descriptive study of the patients with normal axial length (22.0 - 24.5mm) and astigmatism ≤ 1.5D undergoing uncomplicated Phaco with IOL implantation at Out-demand Department, Vietnam National Institute of Ophthalmology from October in 2016 to September in 2017. The ocular biometry was measured with LENSTAR LS900. The 3^rd generation IOL formula (SRKT) was the Olsen formula. For analysis, preoperative anterior chamber depth was divided into three subgroups: ≤ 3.0, 3.0 - 3.5, and ≥ 3.5mm. Lens thickness was divided into two subgroups: < 4.5 và ≥ 4.5mm. The mean error (ME) and mean absolute error (MAE) of each formula was compared for each subgroup at 3-month flow-up. The difference between the MAE of the formulas were compared for each ACD subgroup. Evaluate the correlation between ACD and LT. Result: 137 eyes of 114 patients were followed. The mean age of the study group was 65.68 ± 11.58, the mean ACD was 3.16 ± 0.51mm, the mean LT was 4.35 ± 0.49mm. The MAE were 0.42 ± 0.29D and 0.28 ± 0.26D with SRKT and Olsen formulas, respectively. The difference was statistically significant with p<0.001. With ACD from 3.0 to 3.5mm, there was no difference between the SRKT formula and the Olsen formula. However, with ACD ≤ 3.0mm, ≥ 3.5mm and LT < 4.5, ≥ 4.5mm, the Olsen formula was a significantly better predictor than the SRKT (p<0.01). There was a strong correlation between ACD and LT with r = -0.67 and p<0.001. Conclusion: Anterior chamber depth and lens thickness were important factors in IOL power calculation. The Olsen formula was the best choice for all ACD and LT subgroups in patients with normal axial length.