方法：选择能够用IOL Master准确测量眼轴的、眼轴>26mm的高度近视白内障患者72例97眼，行超声乳化白内障摘除联合IOL植入术。术后1mo进行电脑验光。术前利用LSW1经验公式、SRK-T公式、SRK-Ⅱ公式以及Haigis公式算出每例患者达到正视状态所需IOL屈光度(IOL formula)，综合参考合适的IOL度数。LSW1公式如下：P=P₁+修正值，P₁=(2xP_SRK-T+P_SRK-Ⅱ)÷3。修正值的确定方法为：P₁计算结果为10～15D时，修正值=0.5D； P₁值为5～10D时，修正值=1.0D； P₁值为0～5D，修正值=1.5D； P₁值≤0D时，修正值=3D。根据术后验光结果计算得出达到正视状态所需的IOL理论度数(IOL theory)，四种公式的IOL formula与IOL theory的差异为IOL度数预测误差，再将该IOL预测误差换算成各公式的屈光预测误差(predicitive error，PE)和绝对误差。用SPSS 11.0软件对四种公式所得PE的差异进行比较分析。

结果：(1)研究所纳入的72例患者，年龄41～82(平均63.25±9.65)岁，平均K₁=43.97±1.75，平均K₂=45.14±1.98，中央前房深度(ACD)平均为3.59±0.38mm，平均眼轴长度(AL)：28.67±2.00(26.07～33.98)mm。所置入眼内IOL度数为8.06±4.33(-3～-14.5)D。选择植入的IOL度数基本介于SRK-T和SRK-Ⅱ测算结果之间。(2)屈光预测误差值可以反应屈光预测的趋势。LSW1经验公式，SRK-T公式，SRK-Ⅱ公式以及Haigis公式所产生的预测误差平均值PE值分别为-0.60±0.66D，0.82±0.92D，-0.52±0.84D，0.55±0.74D。四种公式的绝对误差分别为0.74±0.5D，0.94±0.79D，0.81±0.55D，0.73±0.55D。四种公式偏远视的比例分别是：LSW1 14.4%(14/97)、SRK-T82.5%(80/97)、SRK-Ⅱ 20.6%(20/97)，Haigis 79.4%(77/97)。

结论：对于长眼轴高度近视的白内障患者，Haigis公式误差最小，其次为LSW1经验公式、SRK-Ⅱ公式，而SRK- T公式误差最大。四种公式测得患者屈光状态LSW1，SRK-Ⅱ为轻度近视漂移； Haigis公式、SRK-T为远视漂移，SRK-T公式远视漂移更明显，不适合用于高度近视白内障的计算。LSW1公式变异最小，更适合于高度近视眼的IOL测算。

METHODS: A retrospective comparative study was carried out on 97 eyes of 72 patients with axial length(AL)>26mm, who were underwent phacoemulsification with IOL implantation. Preoperative AL was measured by the IOL master, postoperative refractive errors 1mo after surgery were measured by automatic refracto-keratometry(Nidek). IOL power was calculated by SKR-II, SRK-T, Haigis and a new formula developed by the author: LSW1 formula, Power(P)= P₁+P₀, P₁=(2xP_SRK-T+P_SRK-II)÷ 3; when 101≤ 15D, P₀=0.5D; when 51≤10D, P₀=1.0D; when 01≤5D, P₀=1.5D; when P₁≤0D, P₀=3D. According to the results of postoperative refraction calculated the theoretical IOL degree(IOL theory)that could achieve emmetropia. The difference between the IOL formula from four formulas and IOL theory was IOL predictive error(PE). Then IOL PE was converted into refractive PE and absolute prediction error(AE)of each formula. The AE and PE were also analyzed by SPSS 11.0 software.

RESULTS:(1)Among all the patients selected in this study, the average age was 63.25±9.65 years(41～82 years). Average K₁=43.97±1.75, average K₂=45.14±1.98, the average central anterior chamber depth(ACD)3.59±0.38mm, average AL measured by IOL master was 28.67±2.00(26.07～33.98)mm. The average IOL diopter was 8.06±4.33(-3～-14.5)D, the chosen IOL diopter was between the results measured by SRK-T and SRK-Ⅱ formulas.(2)Refractive PE values may be reacted refractive predictable trends. The average PE of LSW1 formula, SRK-T, SRK-Ⅱ, and Haigis were -0.60±0.66D, 0.82±0.92D, -0.52±0.84D, 0.55±0.74D, and the AE of these four formulas were 0.74±0.5D, 0.94±0.79D, 0.81±0.55D, 0.73±0.55D, respectively. The proportion of hyperopia in these four formulas were LSW1 14.4%(14/97), SRK-T 82.5%(80/97), SRK-Ⅱ 20.6%(20/97), Haigis 79.4%(77/97).

CONCLUSION: The PE of Haigis formula is the smallest among all the four formulas, followed by LSW1 formula, and SRK-Ⅱ formula, and SRK-T formula. LSW1 formula and SRK-Ⅱ formula indicate a slight tendency for myopia shift; while Haigis formula and SRK-T formula indicate a tendency for hyperopic shift. SRK-T formula has a larger tendency for hyperopic shift, and cannot provide accurate IOL power calculations in cataract patients with high AL. LSW1 formula has the smallest variability and is the most suitable formula for cataract patients with high AL.