Abstract
Purpose: :
To analyze changes in elevation and axial topography map after implantation of intrastromal ring segments (ICS).
Methods: :
A prospective and observational study was made. Patients with keratoconus with contact lens intolerance, cornea without opacities, best corrected visual acuity (BCVA) 20/100 or better, pachometry ≥ 450µ were into the inclusion criteria and patients with another corneal alterations, opacities or previous ocular surgery were excluded. Preoperative and postoperative at 24 hrs, 1° week, 1°, 3° and 6° month, axial and elevation topography maps (Humphrey Atlas and Orbscan II) were studied. Implantation of 0.450 mm ICS ( Intacs TM, KeraVision), with 80% of stromal thickness were made. Anterior and posterior elevation, keratometry, central pachometry and anterior chamber depht, and surface irregularity were measured. Topographics patterns changes were divided into 5 categories. ANOVA was used to analyze these variables and Pearson's coefficient was use to correlate both topographers.
Results: :
Keratometry in the steepest axis was in average 50.93 D in the preoperative and 46.62 D in the 6 month postoperative (p≤0.005), in the flattest axis was in average 46.34 D in the preoperative and 42.5 D in the 6 month postoperative (p ≤ 0.005). Anterior elevation decreased a mean of 0.021 µ at 6 month postoperative (p≤0.05). Posterior elevation decreased in average 0.01µ during the first 6 months without statistical significance. Anterior elevation patterns changed in 15 cases and in the posterior elevation in 14 cases. Surface irregularity at 5 mm zone increased 1.5 D and at 3 mm zone no important changes were seen. Anterior chamber depth and central pachometry showed clinical but not statistical significance changes. Pearson's coefficient was positive for both topographers.
Conclusions: :
Topography demonstrates that ICS produces important changes in the cornea, decreasing keratometry, anterior and posterior elevation. The ICS reduces the corneal irregularity associated with keratoconus and the topography is an useful instrument in the complete evaluation of these patients.
Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • keratoconus • refractive surgery: corneal topography