Posterior corneal curvature after penetrating keratoplasty with and without sutures

Purpose: After penetrating keratoplasty (PK), peripheral swelling effects, malapposition of the graft in the recipient bed and suture tension may resu lt in a changed ratio of curvature between anterior and posterior corneal s urface. 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 th e 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 wit h "all-sutures-out" (mean age 40+/-18 years, SEQ -0.8+/-3.5 D), and 464 nor mal control eyes (mean age 34+/-16 years, SEQ -0.3+/-2.2 D) were included. Based on Orbscan(R) slit scanning topography analysis the following paramet ers were assessed: posterior power, posterior astigmatism, and posterior as phericity in various segments. Results: With sutures in place the posterior central power ranged from -7.3 6 to -4.53 (mean -5.90+/-0.62) D, astigmatism ranged from 0.13 to 1.15 (mea n 0.42+/-0.20) D, and asphericity ranged from 0.20 to 2.97 (mean 1.13+/-0.7 6, 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" wa s significantly greater than in grafts with "all-sutures-in" and normal con trols (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 h igher in grafts than in the control group (p<0.0001). Asphericity did not d iffer significantly comparing grafts with and without sutures (p=0.49) or c omparing grafts to controls (p>0.38). Conclusions: Except for the amount of astigmatism, the posterior corneal cu rvature of grafts with a double running suture in place does not seem to di ffer significantly from that of normal corneas. The removal of a double run ning suture tends to steepen the central posterior curvature. Knowledge abo ut the individual posterior corneal curvature may have a favorable impact o n the precision of intraocular lens power calculation for cataract surgery in eyes after PK.