[Posterior corneal curvature after penetrating keratoplasty before and after suture removal].

PURPOSE: After penetrating keratoplasty (PK), peripheral swelling effects, malapposition of the graft in the recipient bed and suture tension may result in a changed ratio of curvature between anterior and posterior corneal surface. The purpose of this pilot study was to assess the posterior corneal curvature after PK with and without sutures and to compare this data to the posterior curvature of normal individuals.

PATIENTS AND METHODS: In this cross-sectional study, 44 eyes after PK with a double running 16-bite diagonal antitorque suture in place (mean age 37 +/- 14 years, spherical equivalent (SEQ) -0.1 +/- 3.2 diopters (D)), 36 eyes with "all-sutures-out" (mean age 40 +/- 18 years, SEQ -0.8 +/- 3.5 D), and 464 normal control eyes (mean age 34 +/- 16 years, SEQ -0.3 +/- 2.2 D) were included. Based on Orbscan slit scanning topography analysis the following parameters were assessed: posterior power, posterior astigmatism, and posterior asphericity in various segments.

RESULTS: With sutures in place the posterior central power ranged from -7.36 to -4.53 (mean -5.90 +/- 0.62) D, astigmatism ranged from 0.13 to 1.15 (mean 0.42 +/- 0.20) D, and asphericity ranged from 0.20 to 2.97 (mean 1.13 +/- 0.76, 56% oblate). With "all-sutures-out" the central power ranged from -7.56 to -4.93 (mean -6.41 +/- 0.53) D, astigmatism ranged from 0.13 to 1.15 (mean 0.39 +/- 0.19) D, and asphericity ranged from 0.26 to 3.04 (mean 1.25 +/- 0.76, 44% oblate). In the control group the central power ranged from -7.20 to -4.90 (mean -6.01 +/- 0.29) D, astigmatism ranged from 0.01 to 1.04 (mean 0.12 +/- 0.10) D, and asphericity ranged from 0.33 to 3.13 (mean 1.06 +/- 0.37, 47% oblate). Mean negative posterior power in grafts with "all-sutures-out" was significantly greater than in grafts with "all-sutures-in" and normal controls (p < 0.001), but showed no difference between the two latter groups (p = 0.56). Posterior astigmatism did not differ significantly comparing grafts with and without sutures (p = 0.44). However, astigmatism was significantly higher in grafts than in the control group (p < 0.0001). Asphericity did not differ significantly comparing grafts with and without sutures (p = 0.49) or comparing grafts to controls (p > 0.38).

CONCLUSIONS: Except for the amount of astigmatism, the posterior corneal curvature of grafts with a double running suture in place does not seem to differ significantly from that of normal corneas. The removal of a double running suture tends to steepen the central posterior curvature. Knowledge about the individual posterior corneal curvature may have a favorable impact on the precision of intraocular lens power calculation for cataract surgery in eyes after PK.