Accuracy of the SRK II, SRK/T, Holladay and Hoffer Q IOL power calculation formulas in hyperopic patients after phacoemulsification

Introduction
Comparison of the SRK II, SRK/T, Holladay and Hoffer Q formulas accuracy, in calculating IOL power in hyperopic patients.

Material and methods
34 eyes of 22 hyperopic patients, 15 women and 7 men, at the age from 19 to 85 years old, after phacoemulsification with PCIOL implantation, operated between 1998 and 2004 were analysed retrospectively. The power of IOL was calculated using the SRK/T formula and ranged from 28.5 to 35.0 D. The axial length ranged from 19.6 mm to 21.99 mm. The obtained refraction was measured with autorefractometer from 9 days to 37 month after operation, mean 6 month. In addition, the theoretical target refraction for the implanted IOL was calculated using the SRK II, Holladay and Hoffer Q formulas and the differences between the target and obtained refraction for all the formulas were compared.

Results
The best accuracy of IOL power calculation was obtained with the Hoffer Q formula. The Holladay, SRK/T and SRK II formulas gave worse results respectively.

Conclusions
For the purpose of IOL power calculation in hyperopic patients the Hoffer Q or Holladay formula should be chosen from those mentioned above. Nevertheless, miscalculation exceeding 3D also happens in case of using them. The use of SRK II and SRK/T is not recommended. To improve the results other formulas utilising precise measurements of the anterior segment should be applied. If it is impossible then attention should be paid to improving traditional biometry measurements.