Abstract
Purpose: :
Many ageing subjects with myopic shifts related to cataract are happy when looking clearly at near objects without their lenses. They should be adviced of the advantages of postoperative monovision or multifocal intraocular lenses. The present study shows the prevalence of these myopic shifts in a clinical sample.
Methods: :
A unselected sample of consecutive patients who underwent elective cataract surgery in a private practice setting was studied retrospectively. The myopic shift in refraction was assessed by comparing the old prescription with the present spectacle correction at the time of interviewing. The refraction previous to the myopic shift was used for defining refractive groups. Lens opacity was classified according to the LOCS III system. Subjects were grouped according to the presence or absence of myopic shifts and they were then analysed further with respect of their refraction and degree of nuclear opacity.
Results: :
The mean age of the 229 studied subjects was 71.5 ± 10.4 years (109 males, 120 females). A myopic shift in refraction, defined as at least -0.5 diopters (D) change, was present in 37.1% of them (95% CI: 30.8% - 43.4%). The mean change in refraction of the ones who had a myopic shift was -2.52 ± 1.52 diopters. The percentage of subjects who had developed a myopic shift was significantly greater in those who presented greater nuclear opalescence. With nuclear opalescence up to grade 4 of LOCS III, there were 24.3% without myopic shifts and with nuclear opalescence grades 5 or more there were 50% of subjects with myopic shifts (Chi Square 16.14, p < 0.001). There were also differences in the mean myopic shift by refractive groups, having the emmetropes the greatest myopic shift.
Conclusions: :
In this study of patients seeking cataract surgery in a clinical setting, more than one third had myopic shifts in refraction at the time of surgery. These shifts are more frequent and of greater magnitude in emmetropes and hyperopes than in myopes. Nuclear opacities of greater amounts are related to these myopic shifts. This findings may have importance for ophthalmic surgeons when planning cataract surgery
Keywords: cataract • refraction • myopia