Abstract
Purpose: :
To compare the corneal aberrations (CA) in subjects affected by keratoconus (KC), in patients after automated-lamellar-therapeutic-keratoplasty (ALTK) or penetrating keratoplasty (PK) for KC, and in age-matched controls with normal corneas.
Methods: :
This retrospective, observational, cross-sectional study included 4 groups of subjects: 34 subjects with normal corneas (control group); 33 patients with KC (KC group); 21 patients after penetrating keratoplasty (PK group); and, 16 patients after automated-lamellar-therapeutic-keratoplasty (ALTK group). PK and ALTK were performed in patients with KC having apex opacity or contact lens intolerance. One eye per patient was considered. All subjects underwent imaging with the rotating Scheimpflug camera (Sirius, CSO, Firenze, Italy) to assess the CA from the anterior (ACS) and posterior corneal surface (PCS) within the central 4- and 6-mm zones. The conversion of the corneal elevation profile into corneal wave-front data was done using the Zernike polynomials. Optical path difference (OPD); high-order aberrations (HOA); tilt; sphere; coma; trifoil; and tetrafoil were considered. Differences amongst groups were assessed using the Kruskal-Wallis and least significant difference tests. Statistical significance was defined as p<0.05.
Results: :
All corneal aberrations were significantly lower in controls than in the other groups (p<0.01). The KC and ALTK groups showed: significantly higher OPD from the PCS within the 4-mm zone (p<0.05); higher HOA from both corneal surfaces within the 4-mm zone (p<0.05); and higher coma from both surfaces within both central zones (p<0.05). Tilt from the ACS was higher in the KC group (p<0.01); tilt from the PCS was higher in the ALTK group (p<0.01). No differences were found amongst KC, PK and ALTK groups for sphere, trifoil and tetrafoil.
Conclusions: :
In comparison with eyes that underwent PK for keratoconus, eyes with keratoconus and those after ALTK for keratoconus showed higher OPD, HOA, tilt and coma, which is indicative of a lower corneal surface quality in these eyes.
Keywords: cornea: clinical science