AIM: To evaluate the effect of pupil dilation on ocular biometry and IOL power in cataract patients with high myopia, and the difference between cataract patients with high myopia and cataract patients with normal axial length(AL).

METHODS:Measurements of AL, corneal curvature(K including K1 and K2), anterior chamber depth(ACD)were performed using IOLmaster in 22 cataract patients with high myopia(34 eyes)(group A)and 23 cataract patients with normal AL(39 eyes)(group B)before and after pupil dilation. SRK-T and Haigis were used to caculate pre- and post-cycloplegic IOL power.

RESULTS:ACD after dilation(3.84±0.58mm)significantly increased comparing with ACD before dilation(3.61±0.35mm)in group A(P<0.01). ACD after dilation(3.30±0.70mm)also significantly increased comparing with ACD before dilation(3.13±0.63mm)in group B(P<0.01). But the difference of pre- and post-cycloplegic ACD between the two groups was not statistically significant(P>0.05). Pre- and post-cycloplegic AL and K(including K1 and K2)were not significantly different in two groups(P>0.05). The differences between pre- and post-cycloplegic IOL power were not statistically significant using the SRK-T and Haigis formula(P>0.05), but the IOL power changed by over 1D after pupil dilation using the SRK-T and Haigis formula respectively in 15% and 27% of eyes in group A,in 3% and 5% in group B.

CONCLUSION:ACD increases after pupil dilation in cataract patients with high myopia, which is not different from cataract patients with normal AL. Pupil dilation does not affect AL, K and the IOL power(using SRK-T and Haigis)in cataract patients with high myopia. But the IOL power may change greater than in cataract patients with normal AL, so we suggest IOL power should be measured and calculated without mydriasis.