Daniel S. Durrie

Corneal Topography of Phase III Excimer Laser Photorefractive Keratectomy: Characterization and Clinical Effects

PURPOSE To define qualitative patterns of corneal topography after excimer laser photorefractive keratectomy (PRK), assess changes in patterns, associations with clinical outcomes, and the accuracy of videokeratography in predicting results, and define quantitatively the optical zone contour. METHODS Computer-assisted videokeratography data obtained from 181 patients after PRK was analyzed. Topography patterns at two time points were characterized, and associations with clinical outcomes were tested. Power change predicted by topography was compared with refractive change, and cross-sectional power contours were analyzed. RESULTS Seven topography patterns were defined. At 1 year, 58.6% of corneas showed a homogeneous topography, 17.7% showed a toric-with-axis configuration, 2.8% showed a toric-against-axis configuration, 13.8% showed an irregularly irregular topography, 2.8% showed a keyhole/semicircular pattern, and 4.4% showed focal topographic variants. No central island patterns were found. Of the maps, 41% changed over time. Uncorrected vision, predictability, and patient satisfaction were best in the homogeneous group. Astigmatism increased in the irregular and toric-against-axis groups and decreased in the toric-with-axis group. There was no relation of topography pattern to best-corrected vision or subjective glare/halo. Cross-sectional power profiles showed a homogeneous power change for the central 3 mm with a diminution in correction toward the periphery. The topography unit tended to overestimate refractive change for corrections of 5 diopters or less and underestimate the change for corrections greater than 5 diopters. CONCLUSIONS Topography patterns after PRK are identifiable, time dependent, and may affect clinical outcomes. Understanding the actual corneal optical contour resulting from PRK may aid in improving both laser techniques and optical results in the future.

The Nationwide Study of Epikeratophakia for Aphakia in Children

In the nationwide study of epikeratophakia, 97 surgeons performed a total of 335 procedures in 314 eyes for the correction of aphakia in children under the age of 8 years 1 month. Fifteen children underwent bilateral surgery. Thirty-six tissue lenses were removed and 21 of these eyes underwent a second epikeratophakia procedure. Overall, the success rate for procedures was 89%, and with repeated surgery it was 95% for eyes. Seventy-three percent of the patients were within 3 diopters of emmetropia after surgery. Visual acuity results in patients able to provide verbal responses to the illiterate E, Allen card, or Snellen line chart testing showed improvement in most cases. The safety of epikeratophakia makes it a desirable option for the correction of aphakia in children who are spectacle or contact-lens intolerant, and the permanence of the correction eliminates the problem of optical noncompliance.

The Nationwide Study of Epikeratophakia for Aphakia in Adults

In the nationwide study of epikeratophakia, 154 ophthalmic surgeons who had attended a training course performed 519 procedures for the correction of aphakia in adults: 310 of the eyes had 30 or more days of follow-up after suture removal. Of 229 eyes, 172 (75%) were within 3 diopters of emmetropia after surgery. Of 259 eyes, 245 (95%) demonstrated improved uncorrected visual acuity; 138 (53%) improved by four or more Snellen lines. Of 265 eyes, 209 (78%) achieved within two lines or improved their best corrected visual acuity. Of the 119 patients who achieved or improved their preoperative best corrected visual acuity, 110 (92%) were within two Snellen lines or better by 30 to 60 days after suture removal. Of the 127 patients with more than three months of follow-up after suture removal, 124 (98%) of those between 18 and 70 years of age but only 13 of 23 (54%) of those between 81 and 87 years of age achieved within two lines or better of their best corrected visual acuity. Corneal astigmatism measured by keratometry changed from a preoperative mean (+/- S.D.) of 2.1 +/- 1.8 diopters to a postoperative mean of 2.7 +/- 2.6 diopters. Of the 519 tissue lenses, 22 (4%) were removed, and one third of these patients underwent a second, successful epikeratophakia procedure.

The nationwide study of epikeratophakia for myopia

In the nationwide study of epikeratophakia, 116 ophthalmic surgeons performed 352 procedures for the correction of myopia; 256 of the eyes had 30 or more days of follow-up after suture removal. Of 204 eyes, 153 (75%) were within 30% of emmetropia after surgery. Of 208 eyes, 202 (97%) had postoperative best corrected visual acuity within two Snellen lines or better of their preoperative visual acuity. All but one patient improved uncorrected visual acuity. Of the 120 patients who equaled or improved their preoperative best corrected visual acuity, 116 (97%) were within two Snellen lines of their preoperative measurement between 30 and 60 days after suture removal. Corneal astigmatism changed from a preoperative mean (+/- S.D.) of 1.4 +/- 0.8 diopters to a postoperative mean of 2.6 +/- 2.1 diopters. Of 352 tissue lenses, 36 (10%) were removed, largely as a result of inaccurate power, decay, or failure to reepithelialize, and 17 of these eyes underwent a second successful epikeratophakia procedure.

Indications and Treatment of Keratoconus Using Epikeratophakia

Nineteen patients with keratoconus underwent epikeratophakia by one of the authors (DSD) and were followed from 3 to 29 months. Patient selection criteria included contact lens failure, and minimal or no central corneal scarring. Uncorrected visual acuity improved by three or more Snellen lines in 13 of 19 patients (68%). Postoperatively, after more than 6 months follow-up, 81% of the patients had best-corrected visual acuity of 20/40 or better. A mean flattening of 4.73 diopters (D) occurred on keratometry readings. There was a mean decrease in refractive cylinder of 2.84 D. Spherical equivalent refraction showed a mean decrease in myopia of 4.64 D. Five patients had postoperative refractive cylinder greater than 4 D requiring relaxing incision(s). With some patients having been followed for more than 2 years, no recurrences of keratoconus have been noted. In properly selected patients, epikeratophakia can effectively be used to treat keratoconus and thus avoid potential intraocular surgical complications and immunogenic phenomena.

The Nationwide Study of Epikeratophakia for Aphakia in Older Children

A nationwide study of epikeratophakia for aphakia in older children was conducted from March 1984 to March 1986. Sixty-three patients, 8 to 18 years of age, underwent this procedure in 65 eyes. Twenty-eight patients had congenital cataracts and 35 had traumatic cataracts. Fifty-one of the 65 eyes were aphakic at the time of surgery (secondary procedures). All surgeries were successful; no tissue lenses were lost or removed. Postoperatively, 73% of the patients were within 3 diopters (D) of emmetropia. The patients with congenital cataracts gained an average of one Snellen line of best-corrected visual acuity; patients with traumatic cataracts lost an average of one Snellen line of best-corrected visual acuity. In older pediatric patients, epikeratophakia appears to be a safe and effective procedure for the correction of aphakia.

United States Multicenter Clinical Trial of Corneal Collagen Crosslinking for Keratoconus Treatment

PURPOSE To evaluate the safety and efficacy of corneal collagen crosslinking (CXL) for the treatment of progressive keratoconus. DESIGN Prospective, randomized, multicenter, controlled clinical trial. PARTICIPANTS Patients with progressive keratoconus (n = 205). METHODS The treatment group underwent standard CXL and the sham control group received riboflavin alone without removal of the epithelium. MAIN OUTCOME MEASURES The primary efficacy criterion was the change over 1 year of topography-derived maximum keratometry value, comparing treatment with control group. Secondary outcomes evaluated were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent, endothelial cell count, and adverse events. RESULTS In the CXL treatment group, the maximum keratometry value decreased by 1.6 diopters (D) from baseline to 1 year, whereas keratoconus continued to progress in the control group. In the treatment group, the maximum keratometry value decreased by 2.0 D or more in 28 eyes (31.5%) and increased by 2.0 D or more in 5 eyes (5.6%). The CDVA improved by an average of 5.7 logarithm of the minimum angle of resolution (logMAR) units. Twenty-three eyes (27.7%) gained and 5 eyes lost (6.0%) 10 logMAR or more. The UDVA improved 4.4 logMAR. Corneal haze was the most frequently reported CXL-related adverse finding. There were no significant changes in endothelial cell count 1 year after treatment. CONCLUSIONS Corneal collagen crosslinking was effective in improving the maximum keratometry value, CDVA, and UCVA in eyes with progressive keratoconus 1 year after treatment, with an excellent safety profile. Corneal collagen crosslinking affords the keratoconic patient an important new option to decrease progression of this ectatic corneal process.

Secondary Intraocular Lens Implantation vs Epikeratophakia for the Treatment of Aphakia

We analyzed retrospectively the results of 30 consecutive secondary intraocular lens implantations and 30 epikeratophakia procedures performed by one surgeon for adult aphakia. Specific indications for epikeratophakia were criteria that excluded patients as candidates for intraocular implants. Follow-up of all patients was at least six months. Preoperative and postoperative uncorrected and best corrected visual acuity and endothelial cell counts, as well as power predictability and complications rates, were compared. Preliminary results indicated that postoperative visual acuity, power predictability, and endothelial cell counts were comparable for the two groups. There were, however, fewer sight threatening complications associated with epikeratophakia, and complications in these patients were successfully reversed by removal and replacement of the lenticule.

U.S. Multicenter Clinical Trial of Corneal Collagen Crosslinking for Treatment of Corneal Ectasia after Refractive Surgery

PURPOSE To evaluate the safety and efficacy of corneal collagen crosslinking (CXL) for the treatment of corneal ectasia after laser refractive surgery. DESIGN Prospective, randomized, multicenter, controlled clinical trial. PARTICIPANTS One hundred seventy-nine subjects with corneal ectasia after previous refractive surgery. METHODS The treatment group underwent standard CXL, and the sham control group received riboflavin alone without removal of the epithelium. MAIN OUTCOME MEASURES The primary efficacy criterion was the change over 1 year of topography-derived maximum keratometry (K), comparing treatment with control groups. Secondary outcomes evaluated were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent, endothelial cell count, and adverse events. RESULTS In the crosslinking treatment group, the maximum K value decreased by 0.7 diopters (D) from baseline to 1 year, whereas there was continued progression in the control group (1.3 D difference between treatment and control, P < 0.0001). In the treatment group, the maximum K value decreased by 2.0 D or more in 14 eyes (18%) and increased by 2.0 D or more in 3 eyes (4%). The CDVA improved by an average of 5.0 logarithm of the minimum angle of resolution (logMAR) letters. Twenty-three eyes (32%) gained and 3 eyes (4%) lost 10 or more logMAR letters. The UDVA improved 4.5 logMAR letters. Corneal haze was the most frequently reported crosslinking-related adverse finding. CONCLUSIONS Corneal collagen crosslinking was effective in improving the maximum K value, CDVA, and UDVA in eyes with corneal ectasia 1 year after treatment, with an excellent safety profile. CXL is the first approved procedure to diminish progression of this ectatic corneal process.

Secondary Intraocular Lens Implantation vs Epikeratophakia for the Treatment of Aphakia: Reply

We analyzed retrospectively the results of 30 consecutive secondary intraocular lens implantations and 30 epikeratophakia procedures performed by one surgeon for adult aphakia. Specific indications for epikeratophakia were criteria that excluded patients as candidates for intraocular implants. Follow-up of all patients was at least six months. Preoperative and postoperative uncorrected and best corrected visual acuity and endothelial cell counts, as well as power predictability and complications rates, were compared. Preliminary results indicated that postoperative visual acuity, power predictability, and endothelial cell counts were comparable for the two groups. There were, however, fewer sight threatening complications associated with epikeratophakia, and complications in these patients were successfully reversed by removal and replacement of the lenticule.