Joining the refractive evolution

Emma Firmager outlines some of the highlights from the 12th Annual Congress of the British Society of Refractive Surgery, starting with aberrometry and taking in developments in technology

Zernike polynomials have also become the standard method to describe aberrations, and can tell the examiner a great deal about the nature of these distortions. However, they have limitations and are by no means the only method.

The most significant alternative is the Hamilton power series expansion, which comprise of spherical aberration, coma, astigmatism, field curvature and distortion. Readers will be aware that there are many different manufacturers developing wavefront guided technology.

Professor Jan Venter (Optimax Laser Eyes Clinics) highlighted his experience with the Nidek system. In his study, 93 myopic eyes were included, where mean pre-operative spherical equivalent was -4.00D. Best corrected and uncorrected visual acuities (BCVA and UCVA respectively), refraction, higher-order aberration, spherical aberration and coma were recorded for a minimum of three months post-op.

After this time, 100 per cent of eyes were reported to be within 1.00D of emmetropia, with 89 per cent achieving UCVA of 6/6 or better. Interestingly, there was no loss of BCVA of two or more lines, and 25 per cent gained one line or more.

The study also suggested that wavefront benefits patients with higher pre-op values of higher-order aberration, as well as for coma and spherical aberration values.