AIM: To compare the accuracy of Barrett Universal Ⅱ, Haigis and modified Wang-Koch SRK/T formulas in calculating intraocular lens(IOL)power in eyes with long axial length(AL).

METHODS: Eyes were divided into three AL groups as follows: 26.0 to 28.0mm(group A), 28.0 to 30.0mm(group B), and 30.0mm or more(group C). All eyes underwent phacoemulsification cataract surgery. In the 3mo after operation, IOL powers that would have resulted in emmetropia were calculated according to results of subjective refraction. The predictive error(PE)and absolute error(AE)of each formulas were calculated and compared and the factors(AL, keratometry value, the anterior chamber depth)associated with PEs were analyzed.

RESULTS: The average PE of Barrett Universal Ⅱ, Haigis and modified Wang-Koch SRK/T formulas were 0.37±0.78D, 0.77±0.88D and 0.36±0.82D respectively. In groups A and B, the PEs and AEs of three formulas were not statistically significant(P>0.05). However, in group C, the PEs and AEs of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula were significantly less than Haigis formula(P<0.05). The PEs of Haigis formula in cataract eyes with long AL was affected by AL and keratometry value, whereas the PEs of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula was not affected by AL.

CONCLUSION: In eyes with an AL of 26.0 to 30.0mm, all three formulas are acceptable. In eyes with AL of 30.0mm or more, the accuracy of Barrett Universal Ⅱ and modified Wang-Koch SRK/T formula are better than Haigis formula.