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    How to improve IOL power calculations in keratoconus

    Inaccuracy can be minimised by using an adjusted keratometric approach

     

    Conclusions

    The use of the classical keratometric approach with a single value of nk in keratoconus for the calculation of IOL power is inaccurate and may be the reason for some refractive surprises in this type of eyes after cataract surgery.

    This inaccuracy can be minimised by using an adjusted keratometric approach based on the estimation of the keratometric corneal power, using a variable nk depending on the radius of curvature of the anterior corneal surface, with a maximum error in most of cases of approximately 0.6 D and over 1 D in very few cases.

    We have conducted a successful preliminary clinical validation of this approach for IOL power calculation, and a clinical validation with a larger sample size including severe keratoconus cases is now necessary so that more consistent conclusions can be obtained.

    References

    1. Camps VJ, Pinero DP, de Fez D, Mateo V. Minimizing the IOL power error induced by keratometric power. Optom Vis Sci. 2013;90:639-649.

    2. Camps VJ, Piñero Llorens DP, de Fez D, et al. Algorithm for correcting the keratometric estimation error in normal eyes. Optom Vis Sci. 2012;89:221-228.

    3. Piñero DP, Camps VJ, Mateo V, Ruiz-Fortes P. Clinical validation of an algorithm to correct the error in the keratometric estimation of corneal power in normal eyes. J Cataract Refract Surg. 2012;38:1333-1338.

    4. Camps VJ, Pinero DP, Mateo V, et al. Algorithm for correcting the keratometric error in the estimation of the corneal power in eyes with previous myopic laser refractive surgery. Cornea. 2013;32:1454-1459.

    5. Camps VJ, Pinero DP, Caravaca-Arens E, et al. New approach for correction of error associated with keratometric estimation of corneal power in keratoconus. Cornea. 2014;33:960-967.

    6. Piñero DP, Camps VJ, Ramón ML, et al. Positional accommodative intraocular lens power error induced by the estimation of the corneal power and the effective lens position. Indian J Ophthalmo. 2015;63:438-444.

    7. Piñero DP, Camps VJ, Ramón ML, et al. Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens. Int J Ophthalmol. 2015;8:501-507.

    8. Park do Y, Lim DH, Chung TY, Chung ES. Intraocular lens power calculations in a patient with posterior keratoconus. Cornea. 2013;32:708-711.

    9. Thebpatiphat N, Hammersmith KM, Rapuano CJ, Ayres BD, Cohen EJ. Cataract surgery in keratoconus. Eye Contact Lens 2007;33:244-246.

    10. Pinero DP, Alio JL, Aleson A, et al. Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus. J Cataract Refract Surg. 2008;36:814-825.

    11. Camps VJ, Piñero DP, Caravaca E, de Fez D. Preliminary validation of an optimized algorithm for intraocular lens power calculation in keratoconus. Indian J Ophthalmol. 2017 (in press).

     

     

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