The theoretical basis for the calculation of corneal refractive power from anterior curvature is considered. It is shown that the power can be calculated with sufficient accuracy from one simple formula provided the refractive index of the 'cornea' is 1.3315. It is suggested that keratometer readings should be calibrated with this value in order to increase the accuracy in intraocular lens calc...

AIMS To investigate the ability of a telecentric keratometer to describe the asphericity and curvature of convex ellipsoidal surfaces and human corneas. METHODS 22 conicoidal convex surfaces and 30 human corneas were examined by conventional keratometry. Additional keratometric measurements were made when the surface was tilted in the horizontal plane relative to the instrument optical axis. ...

BACKGROUND As new methods for corneal curvature measurement have evolved, users of videokeratscopes need to know the practical limitations of these instruments. We assessed agreement between keratometry and videokeratography in measuring highly astigmatic corneas. METHODS Two independent examiners made three keratometric and videokeratographic measurements on each of 33 corneas after penetrat...

PURPOSE To compare the corneal power measurements obtained using different topographic instruments after myopic photorefractive keratectomy (PRK). METHODS Patients with myopia who were candidates for corneal refractive surgery were sequentially included. Pre-PRK and six months post-PRK corneal powers were measured using Javal manual keratometer, Orbscan II, Galilei, Tomey TMS4, and EyeSys 200...

Purpose: To compare Orbscan II and Pentacam keratometry readings in terms of their agreement with a manual Javal type keratometer Methods: In this retrospective study, records of patients who had refractive surgery were reviewed. We extracted data of 765 eyes which had keratometry with the Javal keratometer; of these, 577 had Orbscan II and 200 eyes had Pentacam acquisitions. Minimum (min-K) an...

purpose: to compare orbscan ii and pentacam keratometry readings in terms of their agreement with a manual javal type keratometer methods: in this retrospective study, records of patients who had refractive surgery were reviewed. we extracted data of 765 eyes which had keratometry with the javal keratometer of these, 577 had orbscan ii and 200 eyes had pentacam acquisitions. minimum (min-k) and...

PURPOSE To evaluate postoperative astigmatism with regard to incision-induced astigmatism and deviation in axial alignment with the use of preoperative limbal marking with the Javal keratometer (Haag Streit, Bern, Switzerland) in eyes implanted with the Artisan toric phakic intraocular lens (IOL) (Ophtec, Groningen, The Netherlands). DESIGN Prospective nonrandomized trial. PARTICIPANTS Fift...

Automated refraction with the Canon RK-1 Autoref keratometer was evaluated in 85 eyes of 85 patients with an anterior chamber intraocular lens implant and a best corrected visual acuity of at least 6/12. Autorefraction readings were obtained in 80 (94%) of these eyes. The agreement between autorefraction and clinical refraction data was 89% for spherical equivalence less than 0.51 dioptres (D),...

PURPOSE To evaluate the performance of the hand-held and table-top autorefractokeratometer in measuring refractive errors by comparing them with cycloplegic retinoscopy. METHODS Included in the study were 112 eyes of 112 pediatric patients whose mean age was 6.78 ± 2.61 years (range, 2 to 12 years). The refractive errors of all the eyes were measured with and without cycloplegia using a hand ...