Impact of graft diameter on corneal power and the regularity of postkeratoplasty astigmatism before and after suture removal.
OBJECTIVE
To assess the impact of graft diameter on corneal curvature before and after removal of a double-running suture after nonmechanical penetrating keratoplasty (PK).


METHODS
Prospective, nonrandomized, comparative (self-controlled) single-center clinical trial.


METHODS
Four hundred eighty-nine eyes with "two sutures in" and 308 eyes with "all sutures out" (mean age, 52+/-19 years) were included. The diagnoses were keratoconus (48%), Fuchs' and stromal dystrophies (31%), aphakic or pseudophakic bullous keratopathy (11%), and scars (10%).


METHODS
In all eyes, a central trephination was performed (donor trephination from the epithelial side) using the 193-nm Meditec excimer laser (Carl Zeiss Meditec, Jena, Germany) along metal masks with eight "orientation teeth/notches." Diameters were 8.0 mm, 7.5 mm, and 7.0 mm with a graft oversize of 0.1 mm. In 29% of eyes, additional cataract, intraocular lens surgery, or both were performed simultaneously. In all eyes, a double-running 10-0 nylon suture was applied. Zeiss keratometry and TMS-1 topography analysis were performed before removal of the first suture (14+/-4 months) and at least 6 weeks after removal of the second suture (20+/-4 months), but before any additional surgery, such as cataract extraction or refractive keratotomies.


METHODS
Topographic central corneal power (CP; keratometric diopters), keratometric astigmatism (KA), surface regularity index (SRI), and surface asymmetry index (SAI). The regularity of keratometry mires was recorded semiquantitatively from 0 = regular to 3 = not measurable (as published earlier).


RESULTS
With both sutures in, median CP in 7.0-mm (42.0 diopters [D]; P = 0.04) and in 7.5-mm grafts (42.3 D; P = 0.007) was significantly lower than in 8.0-mm grafts (43.0 D). Keratometric astigmatism did not differ between groups (3.0 D vs. 3.0 D vs. 2.7 D). The SRI (1.66 vs. 1.43 vs. 1.11) and SAI (1.55 vs. 1.24 vs. 0.85) decreased significantly with increasing diameter. The proportion of regular keratometry mires (13% vs. 17% vs. 29%) increased, and the proportion of not measurable keratometries (45% vs. 18% vs. 9%) decreased with increasing diameter. With all sutures out, CP in 7.0-mm grafts (40.4 D) was significantly smaller than in 7.5-mm (43.6 D; P = 0.04) and 8.0-mm grafts (43.3 D; P = 0.04). Again, KA did not differ between groups (3.0 D vs. 3.2 D vs. 3.0 D). The SRI (1.40 vs. 1.09 vs. 0.84) and SAI (1.24 vs. 0.83 vs. 0.62) decreased significantly with increasing diameter. The proportion of regular keratometry mires (5% vs. 31% vs. 52%) increased, and the proportion of not measurable keratometries (42% vs. 11% vs. 4%) decreased with increasing diameter.


CONCLUSIONS
After PK, a smaller graft diameter results in a flatter curvature and a higher degree of topographic irregularity, but not in higher net astigmatism. After suture removal, graft topography tends to regularize, whereas the principal differences between diameters do persist.
Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. berthold.seitz@augen.imed.uni-erlangen.de
Berthold
B
Seitz
Achim
A
Langenbucher
Michael
M
Küchle
Gottfried O H
GO
Naumann
D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000503:physiopathology*; D003315:Cornea / Q000502:physiology*; D003316:Corneal Diseases / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D013536:Suture Techniques