Evaluation of intraocular lens power calculation formulas in the triple procedure.

PURPOSE: To determine whether the choice of intraocular lens (IOL) power formula improves IOL power predictions and whether personalized constants within the IOL power formula are critical factors in improving refractive predictions after combined penetrating keratoplasty, cataract extraction, and IOL implantation. METHODS: Records of 46 patients who had the triple procedure between January 1988 and December 1992 were evaluated using the SRK II, SRK/T, Holladay, and Hoffer Q formulas to predict the postoperative spherical equivalent refractions for implanted lens power. Calculations were carried out with and without the use of personalized constants. The predictive accuracy of each formula was assessed by comparing the actual postoperative spherical equivalent refractive error with that predicted by the formulas. The predictive error and the distribution of predictive errors were used to assess predictive accuracy. RESULTS: There was no difference in the mean absolute predictive errors and the distribution of predictive errors for the four formulas evaluated (P > .05). The use of personalized formula constants significantly reduced the mean absolute predictive error for the SRK II, SRK/T, and Holladay formulas (P < .05) and approached significance for the Hoffer Q formula. CONCLUSION: The findings suggest that the choice of IOL power formula does not affect IOL power predictions in the corneal triple procedure; however, personalized constants within a formula appears to be a critical factor in improving postoperative refractive predictions.

Changing indications for penetrating keratoplasty, 1989-1993.

The purpose of this study was to identify new trends in the changing indications for penetrating keratoplasty. We retrospectively reviewed the clinical and pathologic diagnoses of 1,104 corneal buttons that had been submitted to the Estelle Doheny Eye Pathology Laboratory, Los Angeles, during the 5-year period 1989-1993. The leading indications, in order of decreasing frequency, were pseudophakic corneal edema (24.8%), regrafts (21.3%), scarring with or without chronic inflammation (11.1%), keratoconus (7.1%), aphakic corneal edema (6.4%), and ulcerative conditions (5.8%). The incidence of pseudophakic corneal edema remained stable over the study period and was actually surpassed by regraft in the last year of the study. Although pseudophakic corneal edema remains the predominant indication for penetrating keratoplasty, our findings suggest that its occurrence rate has begun to level off.

Penetrating keratoplasty in infants with congenital glaucoma.

The efficacy of corneal transplantation in infants with corneal opacity secondary to congenital glaucoma has not been established. We retrospectively reviewed our results of nine penetrating keratoplasties performed on eight eyes of six infants who had multiple risk factors for poor prognosis: age < 2 years at the time of grafting; uncontrolled glaucoma in four eyes; concurrent lensectomy, retinal, or glaucoma surgery in five eyes; aphakia in five eyes; and an acute perforation in one eye. Six of the nine grafts (67%) remained clear during a mean follow-up of 24 months (30 months in eyes with clear grafts). Development of ambulatory vision or better occurred in six of eight (75%) eyes after corneal transplantation and treatment of refractive errors and amblyopia. Graft failure occurred in three eyes--two from corneal decompensation, and one from homograft rejection. Complications included one total retinal detachment, one case of Streptococcus pneumoniae keratitis, and three cases that lost intraocular pressure control, requiring further glaucoma surgery. We conclude that useful vision can be achieved after penetrating keratoplasty even in some high-risk infants with congenital glaucoma.

Limitations in tandem scanning confocal microscopy as a diagnostic tool for microbial keratitis.

One potential application of tandem scanning confocal microscopy is the detection of in vivo pathogens. Our study of an experimental model of Acanthamoeba keratitis demonstrates that while this technology can successfully detect certain organisms, there are currently limitations. These limitations relate to instrument configuration, movement of either the tissue or the microscope, difficulty in reproducibly returning to the area of interest for serial examination, the lack of a distinctive morphology of some pathogens, and limited resolution of the microscope.

Keratitis as a complication of bilateral, simultaneous radial keratotomy.

During a one-month period, we examined four patients referred for evaluation of probable microbial keratitis after bilateral, simultaneous radial keratotomy. Each patient had midstromal infiltrates compatible with microbial keratitis that involved one or more of the radial incisions. In two patients the keratitis was bilateral. All patients had been treated empirically with antibiotic agents; superficial cultures with cotton-tipped applicators and corneal scraping by inserting a platinum spatula into the radial incisions were negative. Corneal biopsy of one patient disclosed gram-positive rods and culture of the biopsy specimen grew diphtheroids. The infiltrates gradually resolved over a period of several months with intensive antibiotic therapy. Sight-threatening infectious keratitis can occur after radial keratotomy, and we believe that simultaneous bilateral ocular surgery of any kind should be discouraged.