COMMENTARY

Keratoconus: Effect on Cataract Surgery Outcomes

Christopher J. Rapuano, MD

Disclosures

April 24, 2014

Cataract Surgery Outcome in Eyes With Keratoconus

Watson MP, Anand S, Bhogal M, et al
Br J Ophthalmol. 2014;98:361-364

Study Summary

In this study, Watson and colleagues reviewed their results after cataract surgery in eyes with keratoconus. They excluded eyes that had previously undergone or had concurrent corneal transplantation and eyes that underwent toric intraocular lens (IOL) implantation. They also excluded patients who could not provide a subjective endpoint for refraction (eg, certain patients with Down syndrome).

Keratoconus was classified as mild (mean keratometry [K] reading < 48 diopters [D]), moderate (48-55 D), or severe (> 55 D). K readings were performed with interferometry or a handheld keratometer. The investigators used actual measured K values for the IOL power calculation of eyes with mild and moderate keratoconus. In about one half of the eyes with severe keratoconus, they used actual measured K values, whereas in the other half, they used a standard K value of 43.25 D.

The investigators used the SRK-T formula with a targeted postoperative refraction of -1.0 to 1.5 D for the eyes with mild and moderate keratoconus. In eyes with severe keratoconus, they targeted -5.4 D for the actual measured K value or -1.8 D for the standard K value.

For the eyes with mild keratoconus, the mean postoperative spherical equivalent refractive error was 0 D, but there was a large range (+5.2 to -3.0 D). For those with moderate keratoconus, the mean spherical equivalent error was -0.3 D, again with a large range (+3.2 to -3.8 D).

For the eyes with severe keratoconus, when the actual K values were used, there was a large mean spherical equivalent error of +6.8 D, with a huge range: +17 to -0.2 D. For the eyes with severe keratoconus in which a standard K value of 43.25 D was used, the mean spherical equivalent error was +0.6 D (range +6.2 to -5.8 D). The mean postoperative spherical equivalent error of the eyes with severe keratoconus was much higher than that of the eyes with mild or moderate keratoconus, which were similar to each other.

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