Jarade Elias F, Tabbara Khalid F
Eye Center and Eye Foundation for Research, Riyadh, Saudi Arabia.
J Cataract Refract Surg. 2004 Aug;30(8):1711-5. doi: 10.1016/j.jcrs.2003.12.056.
To assess the validity and accuracy of a proposed formula for keratometry (K) readings after laser in situ keratomileusis (LASIK).
The Eye Center and the Eye Foundation for Research, Riyadh, Saudi Arabia.
This studied comprised 34 eyes that had LASIK surgery. Refraction and an automated K-reading (auto-K) were performed preoperatively. Refraction, auto-K, and K-reading assessment by the clinical history method and the proposed formula were performed 4 to 12 weeks postoperatively. The proposed formula is K(postop) = K(preop) - [(N(c) - 1) x (R(a-postop) - R(a-preop))/(R(a-postop) x R(a-preop))], where K(postop) is the K-reading after LASIK, K(preop) is the K-reading before LASIK, N(c) is the index of refraction of the cornea (1.376), R(a-postop) is the radius of curvature of the anterior corneal surface after LASIK, and R(a-preop) is the radius of curvature of the anterior corneal surface before LASIK.
Twenty patients (10 men, 10 women) were included in the study. The mean age of the patients was 30.58 years +/- 17.68 (SD) (range 18 to 44 years). Preoperatively, the mean spherical equivalent (SE) was -4.99 +/- 2.82 diopters (D) (range -1.12 to -15.00 D), the mean R(a) was 7.76 +/- 0.32 mm (range 7.33 to 8.50 mm), and the mean auto-K reading was 43.45 +/- 1.73 D (range 39.62 to 46.00 D). Postoperatively, the mean SE was +0.02 +/- 0.63 D (range -2.75 to +1.00 D), the mean R(a) was 8.63 +/- 0.53 mm (range 7.80 to 9.92 mm), and the mean K-reading assessed by auto-K, clinical history method, and the proposed formula was 39.17 +/- 2.35 D (range 34.00 to 43.25 D), 38.79 +/- 2.52 D (range 33.1 to 42.78 D), and 38.69 +/- 2.51 D (range 33.1 to 43.0 D), respectively. The results obtained by the proposed formula were similar to those obtained by the clinical history method (P =.098). Auto-K readings significantly overestimated the K-values (P<.0001) when compared to the proposed formula and clinical history method.
The proposed formula was simple, objective, not dependent on refraction, and as accurate as the clinical history method in determining K-readings after LASIK.
评估一种用于准分子原位角膜磨镶术（LASIK）后角膜曲率计（K）读数的公式的有效性和准确性。
沙特阿拉伯利雅得的眼科中心和眼科研究基金会。
本研究纳入34只接受LASIK手术的眼睛。术前进行验光和自动角膜曲率计读数（自动K）测量。术后4至12周进行验光、自动K测量，以及通过临床病史法和所提出的公式进行角膜曲率计读数评估。所提出的公式为K（术后）=K（术前）-[(N(c)-1)×(R(a-术后)-R(a-术前))/(R(a-术后)×R(a-术前))]，其中K（术后）是LASIK术后的角膜曲率计读数，K（术前）是LASIK术前的角膜曲率计读数，N(c)是角膜的折射率（1.376），R(a-术后)是LASIK术后角膜前表面的曲率半径，R(a-术前)是LASIK术前角膜前表面的曲率半径。
20名患者（10名男性，10名女性）纳入研究。患者的平均年龄为30.58岁±17.68（标准差）（范围18至44岁）。术前，平均等效球镜度（SE）为-4.99±2.82屈光度（D）（范围-1.12至-15.00 D），平均R(a)为7.76±0.32毫米（范围7.33至8.50毫米），平均自动K读数为43.45±1.73 D（范围39.62至46.00 D）。术后，平均SE为+0.02±0.63 D（范围-2.75至+1.00 D），平均R(a)为8.63±0.53毫米（范围7.80至9.92毫米），通过自动K、临床病史法和所提出的公式评估的平均角膜曲率计读数分别为39.17±2.35 D（范围34.00至43.25 D）、38.79±2.52 D（范围33.1至42.78 D）和38.69±2.51 D（范围33.1至43.0 D）。所提出的公式得到的结果与临床病史法得到的结果相似（P = 0.098）。与所提出的公式和临床病史法相比，自动K读数显著高估了K值（P<0.0001）。
所提出的公式简单、客观，不依赖于验光，并且在确定LASIK术后角膜曲率计读数方面与临床病史法一样准确。
