OBJECTIVE Revision of methods for estimating corneal power (Kpost) and effective lens position (ELP) for cataract surgery after corneal refractive surgery. METHODS Review of medical literature. RESULTS To calculate the intraocular lens that achieves emetropia after corneal refractive surgery it is necessary to correct the Kpost and to estimate the effective lens position again correcting it...

In modern cataract surgery, spectacle freedom is becoming more and more important. Emmetropia can be achieved for patients with myopic or hyperopic refractive errors by selecting the appropriate spherical lens power. However, approximately 20% of patients who undergo cataract surgery have 1.25 diopters (D) of corneal astigmatism or more. (FerrerBlasco, Montes-Mico et al. 2009; Hoffmann and Hutz...

PURPOSE To group eyes in our refractive surgery unit on the basis of the origin of their ametropia and to assess the percentage of eyes in the different groups. METHODS Refractive parameters and the axial eye length (AL) of 131 eyes of 131 persons with different refraction were measured. The eyes were initially classified into five groups on the basis of the grade of their ametropia: hypermet...

PURPOSE To establish whether average refractive overcorrection or undercorrection of corneal astigmatism based on the orientation (rule) of the astigmatism occurs if toric intraocular lenses (IOLs) are calculated on the basis of anterior corneal measurements in eyes requiring toric IOL cylinder power of 2.50 diopters (D) or greater. METHODS One hundred thirteen consecutive eyes with anterior ...

Continuous exposure of chicks to light was shown to result in severe hyperopia, accompanied by anterior segment changes, such as severe corneal flattening. Since rearing chicks in complete darkness results only in mild hyperopia and minor changes in corneal curvature, we hypothesized that light intensity may play a role in the development of refractive changes under continuous light illuminatio...

PURPOSE We classified the Orbscan anterior elevation maps in normal eyes (under myopic, emmetropic and hyperopic conditions) and in those after myopic refractive surgery. We did this classification to demonstrate how Orbscan anterior elevation maps are useful in screening for the existence and extent of previous myopic refractive surgery. Such a classification can help clinicians interpret preo...

PURPOSE To evaluate the accuracy of central corneal power measurements by Scheimpflug imaging (Pentacam) for eyes that had corneal refractive surgery. METHODS This study comprised two groups: a pilot group of 100 eyes with prior hyperopic or myopic LASIK that did not have cataract surgery, and a test group of 41 eyes with prior radial keratotomy (RK) and cataract surgery. In the pilot group, ...

This paper documents a rare nonprogressive developmental disorder-bilateral circumscribed posterior keratoconus-in a 60-year-old man referred for a cataract surgery. For the first time ultrasound biomicroscopy was used to visualise the local anterior bulging of the posterior corneal surface with concomitant thinning of the stroma. The amount of localized posterior depression, corneal thickness ...

PURPOSE To evaluate with the use of corneal topographic data the differences between total corneal power calculated using ray tracing (TCP) and the Gaussian formula (GEP) in normal eyes, eyes that previously underwent laser in situ keratomileusis/photorefractive keratectomy (LASIK/PRK), and theoretical models. METHODS TCP and GEP using mean instantaneous curvature were calculated over the cen...

Results. For the spherical surface, both curvature-based paraxial power approximations were uniform over the entire surface because curvature is constant. However, the corneal refractive power increased from center to periphery, demonstrating the known phenomenon of spherical aberration. For the ellipsoids, which have been shown to model the human cornea, curvature-based power approximations de...