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Impressum
Halo size and halo intensity through the distance and near focus in diffractive and refractive multifocal lenses
Schmidinger G., Pieh S., Italon C., Lackner B., Kaminski M., Skorpik C.
Refraktive Ambulanz, Universitätsklinik für Augenheilkunde und Optometrie, Wien, Österreich
Purpose: To evaluate the halo size and intensity simulating a
light source at infinity and at reading distance in two different multifocal
concepts.
Methods: In 11 eyes of 10 patients with a diffractive multifocal
IOL (811E , Pharmacia) and 12 eyes of 9 patients with a refractive multifocal
IOL (SA 40N, Allergan) the best corrected visual acuity was determined.
The halo size and intensity was determined by means of a computer program
(halostimulator 1.0). For evaluating the halo through the distance focus
the patient is sitting 2 m in front of a video monitor with the best distance
refraction plus 0.5 D. On the video monitor a white light source with
an extend of 10´ against a black background is simulated. Using
the computer mouse the extent of the subjective observed halo can be objectified.
Further the background was brighten as long the patient can not detect
a halo. This result as contrast between the light source and the background
was correlated with the halo intensity. The same set-up was used with
the best distance refraction minus the additional near lens power of the
multifocal lens, to force the patient to use the near focus.
Results: In the diffractive group the halo size through the distance
focus was 0.16 square degrees ± 0.04 and the evaluated contrast
83 % ± 4.82, through the near focus the halo size was 0.17 square
degrees ± 0.07 and the contrast 57.22 % ± 15.32. In the
refractive group the halo extent through the distance focus was 0.11 square
degrees ± 0.02 and the contrast 71.08 % ± 13.53, while through
the near focus the halo size was 0.14 square degrees ± 0.13 and
the contrast 63.75% ± 22.66.
Conclusion: Using this computer program the halo size in the diffractive
lens was larger, the halo intensity was in both lenses through both foci
comparable.