Sutured posterior chamber intraocular lenses: indications and procedure.

Intraocular lens (IOL) implantation is the standard of care for treating aphakia when spectacle or contact lens correction is not viable. There is considerable controversy about the relative efficacy and safety of the different IOL implantation approaches, as well as their indications. Since the development of the modern, open-loop anterior chamber IOL (ACIOL) and the re-emergence of the iris-fixated claw IOL, ACIOL implantation for aphakia has regained popularity. However, the posterior chamber IOL (PCIOL)--namely, the capsular-supported PCIOL and, in the absence of capsular support, the iris-sutured or transsclerally sutured PCIOL--offers numerous advantages for certain patients. By virtue of their anatomic location in the eye, capsular-supported or sutured PCIOLs are appropriate for patients with glaucoma, diabetes, cornea guttata or low endothelial cell count, peripheral anterior synechiae, or known or suspected cystoid macular edema. They may also be appropriate when the patient with aphakia is young and has a relatively long life expectancy. The sutured PCIOL procedure--specifically, the transsclerally sutured PCIOL procedure--is far from benign, however, and surgical expertise is an important consideration. Recent surgical and technological advances, including the technique of burying the suture knot in sclera, use of an ab externo suturing approach in the normotonic eye, and the use of intraoperative endoscopy, have improved the accuracy of the transsclerally sutured PCIOL technique. Additional advances, including diagnostic ultrasound biomicroscopy and small-incision surgery with foldable, transsclerally sutured IOLs, may further improve patient management and clinical outcomes.

Unilateral keratoconus. Incidence and quantitative topographic analysis.

OBJECTIVE: This study was designed to determine the incidence of unilaterality in a population of patients with clinical keratoconus and to compare quantitative descriptors of topography between affected corneas from patients with unilateral keratoconus and corneas of patients with bilateral disease. DESIGN: Retrospective clinical study with new evaluation of some patients. PARTICIPANTS: One hundred sixty-four patients from the University of Texas South-western Medical Center and Wills Eye Hospital who were diagnosed to have moderate-to-advanced keratoconus on the basis of characteristic topographic patterns associated with corneal thinning. INTERVENTION: Corneal topography was evaluated in both eyes of each patient. MAIN OUTCOME MEASURES: Quantitative descriptors of corneal topography were compared between 5 affected corneas of patients with unilateral keratoconus (combined cases from University of Texas Southwestern, LSU Eye Center, and Wills Eye Hospital) and 15 corneas of patients with moderate-to-advanced bilateral keratoconus (1 cornea from each patient). Indices selected for statistical analysis were the Keratoconus Predication Index (KPI), Surface Asymmetry Index (SAI), and Surface Regularity Index (SRI). RESULTS: Three (1.83%) of 164 patients with moderate-to-advanced keratoconus had no topographic evidence of keratoconus in the opposite eye. There were no statistically significant differences in KPI, SRI, or SAI values between the affected corneas of patients with unilateral and bilateral keratoconus. Over a period of 4 years of observation, signs of keratoconus in the previously normal eye developed in a patient with unilateral keratoconus. CONCLUSIONS: The authors found no differences in the quantitative descriptors of corneal topography between corneas with keratoconus from unilateral and bilateral cases. The authors' results suggest that the incidence of "unilateral" keratoconus is very low. Patients initially diagnosed with unilateral keratoconus, if observed for a sufficient period, commonly had signs of keratoconus develop in the opposite eye. The possibility that all cases of unilateral keratoconus may eventually become bilateral cannot be excluded. Therefore, refractive surgical procedures should not be performed on apparently normal corneas when keratoconus is detected in the opposite eye.

A new technique for transscleral fixation of a posterior chamber intraocular lens in the absence of capsular support during penetrating keratoplasty.

In the setting of penetrating keratoplasty for the rehabilitation of aphakic or pseudophakic bullous keratopathy, a posterior chamber intraocular lens is frequently implanted in the absence of capsular support. Some surgeons have advocated transscleral fixation over iris fixation of the intraocular lens. Problems faced during such a procedure, however, include the obstructed approach of the suture needle behind the iris, and the exposed or eroded knot of the polypropylene suture. To circumvent both problems, we propose an ab externo technique that takes advantage of the work of Duffey et al and avoids the use of partial thickness scleral flaps.

Reproducibility of normal corneal power measurements with a keratometer, photokeratoscope, and video imaging system.

To determine the reproducibility of currently available instruments for measuring corneal power, two investigators measured comparable locations on 18 normal human corneas using a keratometer (Bausch & Lomb, Rochester, NY), the Corneascope (Kera Corp, Santa Clara, Calif), and the Corneal Modeling System (Computed Anatomy Inc, New York, NY). (For the two keratoscopes, average powers around rings at comparable locations were used.) Comparisons made between instruments at the significance level of .05 indicated that the keratometer was more reproducible than the Corneal Modeling System and the Corneascope, and the Corneal Modeling System was more reproducible than the Corneascope. Of the 31 rings projected on the surface of each cornea by the Corneal Modeling System, rings 2 through 13 were read reasonably reproducibly in that 76% of the measurements on these rings differed by no more than 0.5 diopter. The Corneal Modeling System (software version 1.16) is 83% as reproducible as a keratometer reading at approximately the edge of the 3-mm central zone on normal human corneas and provides information about corneal topography in a more reproducible and visually useful manner than the other two instruments.

Accuracy and precision of keratometry, photokeratoscopy, and corneal modeling on calibrated steel balls.

Surgical manipulation of corneal shape requires an accurate and precise method of measuring anterior corneal curvature from apex to limbus. We evaluated the accuracy and precision of the Bausch & Lomb Keratometer, Kera Corneascope, and Computed Anatomy Corneal Modeling System by measuring comparable locations on four calibrated steel test balls. The Keratometer and Corneal Modeling System were more accurate and precise than the Corneascope. No statistically significant difference was found between the Keratometer and Corneal Modeling System with respect to accuracy or precision. In addition, the accuracy and precision of all 31 rings of the Corneal Modeling System were studied. Rings 2 through 26 were read accurately and precisely within +/- 0.25 diopter on three of the four balls. Values on the steepest ball were within +/- 0.37 diopter.