A comparison between subjective refraction and aberrometry-derived refraction in keratoconus patients and control subjects.
OBJECTIVE
This study compares the differences in the magnitude of the subjective refraction and three aberrometry-derived refractions along with visual acuity achieved with these refractions in a group of keratoconic patients and age-matched normal subjects.


METHODS
Subjective refraction and Hartmann-Shack aberrometry was performed on six keratoconus patients and 12 normal subjects. In addition, the logMAR visual acuity achieved using the subjective and aberrometry auto-refraction data were measured in the six keratoconic subjects.


RESULTS
The subjective and aberrometry-derived spherical equivalent refraction data were significantly different in the keratoconus group (p = 0.015) but not in the normal group (p = 0.10). In the keratoconic patients, subjective refraction data gave better logMAR acuity than the aberrometry-derived auto-refraction data. The magnitudes of vertical coma and higher-order RMS (root mean square) error showed significant correlations with the subjective refraction logMAR visual acuities. Significant correlations were found between the magnitudes of manifest vertical coma and higher-order RMS error and the difference in the M (the mean equivalent sphere) power vector terms between the subjective and aberrometry-derived auto-refraction data in the keratoconic group.


CONCLUSIONS
The subjective and aberrometry-derived spherical equivalent refraction data were significantly different in the keratoconus group. The larger the magnitude of the higher-order aberrations in keratoconic eyes, the poorer the subjective refraction logMAR acuity and the larger the difference between the subjective and aberrometry-derived M power vector terms. Further investigation into deriving objective refraction data from aberrometry measurements is warranted in keratoconus.
Jinabhai
Amit
A
Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.
O'Donnell
Clare
C
Radhakrishnan
Hema
H
D057128:Aberrometry; D000328:Adult; D057108:Corneal Wavefront Aberration / Q000503:physiopathology*; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology*; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology