Posters

Accuracy of intraocular lens power calculation formulas in eyes with shallow anterior chamber

Poster Details

First Author: J.Coelho PORTUGAL

Co Author(s):    A. Abreu   V. Lages   A. Figueiredo   R. Reis   P. Meneres   M. Meneres     

Abstract Details

Purpose:

To compare the accuracy of Intraocular Lens (IOL) power calculation formulas in eyes with Shallow Anterior Chamber (SAC).

Setting:

Department of Ophthalmology of a tertiary referral center in Oporto, Portugal - Centro Hospitalar Universit�Ã�¡rio do Porto.

Methods:

Retrospective comparative study of refractive outcomes of 50 eyes with SAC with 50 normal eyes undergoing uneventful cataract surgery. All eyes were previously analysed by Pentacam being included in SAC group if anterior chamber depth (ACD) <2,1mm and anterior chamber volume (ACV) <100mm3. ACD, axial length (AL) and ACD to AL ratio were evaluated by the IOL Master. Third generation formulas (SRK/T, HofferQ and Holladay) and fourth generation formula (Haigis and Barrett II) were used to predict IOL powers. The predictive accuracy of the formulas was analysed by comparison of the Mean Error (ME) and the Mean Absolute Error (MAE).

Results:

SAC patients�â�€�™ were mostly females and younger (p<0,05). Mean postoperative spherical equivalent (SE) was higher in SAC group (p=0,016) with a higher percentage of eyes outside �Â�±0.5D of postoperative SE (p=0,014). In SAC group ME and MAE from the Haigis formula were the smallest and the HofferQ formula were the largest. MEs of SRK/T, HofferQ and Holladay formulas (p<0,001) were higher in eyes with SAC. In the SAC group all formulas showed a negative ME. The percentage of eyes outside �Â�±0.5D of the target refraction was higher in the SAC group only with the HofferQ formula�â�€�“p<0,05.

Conclusions:

IOL power prediction may be inaccurate in eyes with shallow anterior chamber and this may be related to their unique anterior segment anatomy. In our study, the third generation formula Hoffer Q produced more inaccurate results in eyes with shallow anterior chamber being in these group more appropriate to use the Haigis formula, a fourth generation formula, to predict IOL power. The slight post-operative myopic shift seen in our study may be caused by IOLs instability due to larger capsular volume and loosened capsular zonules often seen in eyes with shallow anterior chamber.

Financial Disclosure:

NONE