Determination of the power of a convex-plano intraocular lens in situ from the dioptric keratometer reading of its front surface: extension table for the Javal-Schiøtz ophthalmometer.

The size of the reflex image of keratometer mires can be used to determine the power of an intraocular lens (IOL) inside the eye (in situ). The dioptric scale reading from the front surface of a convex-plano intraocular lens in cases of unknown power is compared with computed values. The accuracy of the method is demonstrated in a series of patients with known IOL power. Though in our study we have assumed convex-plano lenses are in use, the same procedure can sometimes be applied to lenses of different forms. To interpret scale readings below 30 dioptres and over 60 dioptres we compiled an extension table, suited to the ophthalmometer of Javal-Schiøtz (Haag-Streit), making use of low-powered minus and plus auxiliary lenses in front of the tube of the instrument.