Higher-Order Aberrations Contribute Little to Ocular Residual Astigmatism

Among healthy candidates for refractive surgery, ocular residual astigmatism (ORA) is positively correlated with general corneal irregularities, but whole-eye higher-order aberrations (HOA) were not significant contributors, according to research published in Cornea.

Patients (N=294; 61.90% women; mean age, 28.81±5.40 years) who were candidates for refractive surgery without other eye conditions were recruited at a high-volume surgical center in Colombia. The researchers evaluated the role of corneal and whole-eye lower order aberrations (LOAs) and HOAs have on ORA. To that end, 1 eye from each patient was randomly selected and evaluated.

At baseline, the average ORA was 0.77±0.40 D and the distribution of ORA was non-normal (P <.001).

Significant correlations were observed between ORA and corneal HOA root mean square (RMS; r, 0.162; P =.005), whole-eye vertical quadrafoil (r, 0.149; P =.010), total corneal RMS (r, 0.142; P =.015), corneal LOA RMS (r, 0.123; P =.035), corneal defocus (r, 0.121; P =.039), and corneal vertical astigmatism (r, -0.120; P =.040).

In the final multiple regression analysis (F_[3,282], 78.977; P <.001), significant variables contributing to ORA included total corneal RMS (t, 3.868; P<.001), corneal orthogonal cylinder power (J₀; t, 11.899; P <.001), and manifest J₀ (t, -14.976; P <.001).

This study was limited by its retrospective design, in which only data about total corneal aberrations were available and the investigators were not able to assess anterior corneal astigmatism data.

“ORA is an important concept in subjects being considered for possible corneal-based laser refractive surgery,” the researchers explain. “After adjusting for other variables, ORA seems to be somewhat correlated with the total corneal aberrations (RMS total), but there is no evidence to suggest that any given HOA or LOA is related to the level of ORA. These results point to corneal astigmatism and manifest astigmatism as being the most strongly related variables to ORA in otherwise healthy refractive surgery candidates and suggest that the effect of HOAs is negligible.”