Résumé
Some studies have shown that eyes undergo a hyperopic shift after the presbyopia, whereas others have reported a myopic shift. The purpose of this study was to determine types and the degree of refractive errors before and after presbyopia. This was a cross sectional study carried out at the department of optometry[Mashhad University of Medical Sciences] in2001.Followingroutineoptometricexamination, the type and degree of refractive errors of 500 patients before and after presbyopia were statically analyzed using X[2] and student t-tests. The prevalence of hyperopia was 19.4% before presbyopia which later increased to40.1% [p<0.001]. Following the occurrence of presbyopia, against-the-rule astigmatism increased to 12.3% whereas the with-the-rule astigmatism decreased to 12.9% [p<0.001]. The distribution of oblique astigmatism was3.7%and3.4%beforeandafter presbyopia, respectively. The gender had no effect on refractive errors before and after presbyopia. The presbyopia caused a reduction in optical power of eyes and also increase dhyperopia. Reduced rigidity of the upper tarsal plate associated with presbyopia, caused an increase in the against-the-rule astigmatism