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.

Results of anterior segment reconstruction for aphakic and pseudophakic corneal edema.

The authors studied prospectively 59 eyes with corneal edema after cataract surgery that required reconstructive surgery; penetrating keratoplasty in 59 (100%), anterior vitrectomy in 42 (71%), intraocular lens removal or exchange in 33 (56%), gonioplasty in 32 (54%), and iridoplasty in 30 (51%). With an average follow-up of 9.9 months, the corneal transplant was clear in 56 eyes (95%). The corrected visual acuity was improved in 49 eyes (83%) and was the same in seven eyes (12%). Intraocular pressure was less than or equal to 21 mmHg in 47 eyes (80%) and 22 to 29 mmHg in nine eyes (15%). The peripheral anterior synechiae score was the same or improved in 56 eyes (95%). Cystoid macular edema was absent to mild in 52 eyes (88%). Anterior segment reconstruction improved both anatomic integrity and visual acuity of most eyes without increasing complications.

Ptosis associated with botulinum toxin treatment of strabismus and blepharospasm.

The incidence, severity, and duration of ptosis after botulinum neurotoxin type A (BAT) injections into extraocular or orbicularis muscles were reviewed retrospectively. Even though lid droop frequently complicated botulinum toxin treatment in this series, no loss of vision or permanent ptosis was encountered. Sixty-seven injections were completed in 44 patients between September 1982 and December 1983. The records were reviewed to determine the incidence of ptosis after these 67 injections. Information was not adequate to ascertain the presence or absence of ptosis after 10 injections. Some degree of ptosis developed after 30 (53%) of the 57 injections with adequate follow-up history. Marked ptosis occurred after 12 (21%) of the 57 injections. The posttreatment lid droop in these 12 cases was potentially visually significant. All cases of ptosis, which impinged on the visual axis, resolved to a level permitting undisturbed vision by eight weeks after toxin injection. The incidence of ptosis was similar in patients who received injections into their medial rectus muscles and in patients who received injections into their lateral rectus muscles. However, an increased incidence of marked ptosis may be associated with the injection of previously operated muscles. Toxin dosage, patient age, and quality of the electromyogram used to monitor the injection showed no statistically significant relationship to the ptosis.