Direction of gaze-dependent visual acuity determination for correctly and incorrectly centred single vision aspheric lenses

Purpose:

To investigate the effect on visual acuity of disregarding the centre of rotation requirement when using single vision aspheric lenses for correction of moderate to high hyperopes.

Material and Methods:

Two aspheric single vision lenses are fitted in each eye of 15 hyperopic subjects. One lens is exactly centred, the other lens is horizontally decentrated five millimetres temporally. The interpolated LogMAR is then determined in five different directions of gaze. The extent to which the LogMAR achieved differs between the lens with the observed centre of rotation requirement and the disregarded centre of rotation requirement in the individual directions of gaze is then examined. In addition, the influence of age is investigated. The results of the sub-samples “Age < 50 years” and “Age ≥ 50 years” are analysed descriptively. A clinically significant difference is defined as half a visual acuity level (corresponds to 0.05 LogMAR).

Result:

Significant differences in LogMAR between exact and incorrect centring could be determined for 30° nasal gaze (-0.09 LogMAR) and for 0° gaze through the lens (-0.07 LogMAR). Visual acuity was better with the precisely centred lens in each case. When testing for differences in LogMAR between the defined age-dependent subsamples, no significant differences could be determined.

Conclusion:

The results show that the aberrations astigmatism of oblique bundles and the image field curvature with the resulting deviation from refractive accuracy have less influence on visual acuity than previously assumed.