Myopic astigmatism as a substitute for accommodation in pseudophakia.

Pseudophacic eyes can be made nearly spectacle-independent by increasing the depth of focus of the uncorrected implanted eye. When the postoperative ametropia is a simple myopic astigmatism the uncorrected visual acuity can be above 0.4 from far to near. The quasi-constant visual acuity in different distances is due to the slow change in the dimension of the blurred retinal image when a point source comes nearer to a myopic astigmatic eye. The intersection of Sturm's conoid and the retina (i.e. the blur spot) changes mainly in form but its size changes much less than in a sperical ametropia. To obtain such a refraction the dioptric change in corneal power induced by surgery must be included in the calculation of the intraocular lens. The induced corneal ametropia is a mixed astigmatism with no equivalent power. The optical principles and the clinical results obtained with iridocapsular Binkhorst lenses are discussed.