Caracas, Venezuela-Implantation of intrastromal corneal ring segments (Intacs, Addition Technology) and penetrating keratoplasty (PKP) result in similar vision improvement when used to treat eyes with a mild grade of keratoconus, but the implantation procedure offers the advantage of faster visual rehabilitation, said Luis A. Rodriguez, MD.
Dr. Rodriguez, of the department of cornea and refractive surgery, Centro Medico Docente la Trinidad, Caracas, Venezuela, compared the two techniques in a nonrandomized, bilateral study including five patients who had grade 2 keratoconus in both eyes. Follow-up visits were at 1, 2, and 6 months for the patients who received the intrastromal corneal ring segments (ICRS) and at 2, 6, and 20 months after suture removal for the PKP group.
"Intrastromal corneal ring segment implantation is an effective method for improving corneal regularity and vision in eyes with keratoconus and affords rapid recovery of vision. Now, continued follow-up is needed to determine the long-term effects of this surgery in ectatic corneas," said Dr. Rodriguez.
In a cohort of eyes with keratoconus operated on between January 1990 and March 2005, Dr. Rodriguez has performed PKP in one eye and ICRS implantation contralaterally in 15 patients. However, only five eyes that had matching grades of keratoconus at the time of surgery were included in his analysis. To be included in the analysis, the PKP eyes were required to have had clear grafts, all sutures removed, regular astigmatism, and a stable refractive error for at least 6 months.
Data were analyzed from follow-up visits conducted at 2, 6, and 20 months after PKP and at 1, 3, and 6 months after ICRS implantation.
Mean preoperative uncorrected visual acuity (UCVA) values were 20/400 in the PKP eyes and 20/200 in the ICRS eyes. At last follow-up, mean UCVA was 20/50 in the PKP eyes and 20/40 in the ICRS eyes. The PKP group achieved a greater mean improvement in UCVA compared with the ICRS eyes, 8.6 versus 6.2 lines, but the difference between groups was not statistically significant.
All eyes in both groups achieved at least a 4-line improvement in UCVA and maximum improvement was 12 lines in the PKP eyes and 10 lines in the ICRS group.
Mean SE was reduced by about 3 D in both groups with an approximately 1- to 1.3-D reduction in astigmatism. The Kflat and Ksteep data showed the PKP corneas were steeper preoperatively and achieved a greater flattening effect from the surgery. However, postoperatively, there were no significant differences between the PKP and ICRS eyes in comparisons of postoperative mean Kflat (42.51 versus 42.54 D) or Ksteep (46.33 versus 42.75 D) values.