Corneal First Surface Wavefront Aberrations Before and After Pterygium Surgery

PURPOSE

To determine the higher order aberrations at the corneal first surface before and after surgery for pterygium.

METHODS

Data were drawn from a longitudinal study of patients undergoing pterygium excision at Royal Victoria Infirmary, Newcastle upon Tyne, England between September 1998 and May 2004. Corneal topography was taken with the TMS-2 Topographic Modeling System (Computed Anatomy Corp) prior to and 6 months after surgery, exported to VOLPro software v7.08 (Sarver & Associates), and wavefront aberrations were derived for a 5.0-mm pupil using a 10th order Zernike polynomial expansion. Pre- to postoperative changes were assessed for significance using analyses of variance, and the relative risk of significant postoperative aberrations by pterygium size was determined.

RESULTS

Satisfactory corneal topography was available on 67 eyes (mean age 53.8±16.7 years [range: 25-86 years]). The root-mean-square (RMS) fit error in preoperative eyes was 0.15±0.10 µm. Preoperatively, the total higher order RMS wavefront aberration was 0.94±0.83 µm. All Zernike modes were elevated, with trefoil being the major contributor 0.52±0.50 µm. Pterygium excision significantly reduced wavefront aberrations across all modes and orders (F_1,129=6.7 to 22.6, P<.01): total higher order RMS_postop 0.45±0.35 µm. Cases with visually significant postoperative aberrations occurred and were more likely with larger pterygia: relative risk compared to pterygia 1.0 to 1.9 mm was 1.3 for 2.0 to 2.9 mm, 8.5 for 3.0 to 3.9 mm, 13.3 for 4.0 to 4.9 mm, and 10.2 for 5.0 to 5.9 mm.

CONCLUSIONS

Zernike polynomial fitting well describes wavefront aberrations in eyes with pterygia. Pterygia are associated with wavefront aberrations, especially trefoil, but these were largely eliminated by surgery. Earlier excision of pterygia reduces the likelihood of significant residual aberrations. [J Refract Surg. 2006;22:921-925.]

AUTHORS

From NH&MRC Centre for Clinical Eye Research, Department of Ophthalmology, Flinders Medical Centre and Flinders University, Bedford Park, South Australia, Australia (Pesudovs); and the Cornea Service, Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom (Figueiredo).

Dr Pesudovs is supported by NH&MRC Sir Neil Hamilton Fairley Fellowship 0061 Canberra, Australia, and this work was supported in part by NH&MRC CCRE grant 264620.

The authors have no commercial or proprietary interest in the materials presented herein.

The authors thank Kevin Gales and colleagues for optometric support.

Correspondence: Konrad Pesudovs, PhD, NH&MRC Centre for Clinical Eye Research, Dept of Ophthalmology, Flinders Medical Centre, Bedford Park, South Australia, 5042, Australia. Tel: 618 8204 4899; Fax: 618 8277 0899; E-mail: Konrad.Pesudovs@flinders.edu.au