- Email: [email protected]
Impact of graft diameter on corneal power and the regularity of postkeratoplasty astigmatism before and after suture removal
Impact of Graft Diameter on Corneal Power and the Regularity of Postkeratoplasty Astigmatism before and after Suture Removal Berthold Seitz, MD, FEBO, Achim Langenbucher, PhD, Michael Ku¨chle, MD, Gottfried O. H. Naumann, MD 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). Design: Prospective, nonrandomized, comparative (self-controlled) single-center clinical trial. Patients: 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%). Interventions: 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. Main Outcome Measures: 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. Ophthalmology 2003;110: 2162–2167 © 2003 by the American Academy of Ophthalmology. From June 1989 through January 2003, more than 1300 cases of nonmechanical penetrating keratoplasty (PK) were Originally received: August 16, 2002. Accepted: January 29, 2003. Manuscript no. 220566. From the Department of Ophthalmology, University of Erlangen-Nu¨rnberg, Erlangen, Germany. Supported in part by the BMBF (IZKF Erlangen, Project B13) and Neurocenter Erlangen, Erlangen, Germany. The authors have no proprietary interest in the development or marketing of instruments or pieces of equipment mentioned in this article, or any competing instruments or pieces of equipment. Reprint requests to Berthold Seitz, MD, FEBO, Oberarzt, Augenklinik mit Poliklinik der Universita¨t Erlangen-Nu¨rnberg, Schwabachanlage 6, D-91054 Erlangen, Germany. E-mail: [email protected]. Website: www.kornea.org.
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© 2003 by the American Academy of Ophthalmology Published by Elsevier Inc.
performed by six microsurgeons using the 193-nm excimer laser in our Department of Ophthalmology in Erlangen, Germany.1,2 By far, the most frequent indications were keratoconus (n ⫽ 436), followed by Fuchs’ dystrophy (n ⫽ 254), bullous keratopathy (n ⫽ 210), and scars (n ⫽ 124). Especially for young patients with keratoconus, nonmechanical trephination offers clear advantages, such as reduction of keratometric astigmatism, higher regularity of corneal topography, and a significantly better visual acuity, which is the only truly relevant aspect for the patient.3 For immunologic purposes, the size of the graft should be chosen with respect to the individual size of the recipient cornea. It should be “as small as necessary, but as large as possible,”4,5 because smaller grafts are supposed to allow only for an inferior optical performance.6 – 8 At this time, it ISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(03)00659-6
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature Table 1. Distribution of Diagnoses for Three Different Graft Diameters in Percent (n ⫽ 489)
7.0 mm (n ⫽ 46) 7.5 mm (n ⫽ 214) 8.0 mm (n ⫽ 229) Overall
Keratoconus
Dystrophies
Bullous Keratopathy
Scars
7 10 93 48
26 60 3 31
47 16 2 11
20 14 2 10
is not clear what the reason is for this lower optical quality of smaller grafts. The purpose of this study was to assess the impact of graft diameter on corneal curvature (i.e., corneal power, amount and regularity of keratometric astigmatism) before and after removal of a double-running suture after nonmechanical PK.
Patients and Methods Patients and Donor Details In this prospective, nonrandomized, comparative (self-controlled) single-center clinical trial, 489 eyes with “two sutures in” (mean age, 52⫾19 years; 49% right eyes; 46% females) and 308 eyes with “all sutures out” were included. The diagnoses were keratoconus (48%), Fuchs’ and stromal dystrophies (31%), aphakic or pseudophakic bullous keratopathy (11%), and scars of various origin (10%; Table 1). Inclusion criteria were: primary central PK; recipient trephination, including 7.0 mm (age, 65⫾19 years), 7.5 mm (age, 62⫾17 years), and 8.0 mm (age, 38⫾12 years); graft oversize 0.1 mm; and double-running diagonal suture. Exclusion criteria were: elliptical keratoplasty, additional single sutures, and infectious keratitis (nonelective surgery). Institutional review board and ethics committee approval was not required for this study. Donor age varied from 8 to 93 years (median, 62 years), postmortem time varied from 1 to 72 hours (median, 10 hours), and, depending on the proportion of organ-cultured corneas (47%), preservation time varied from 3 to 720 hours (median, 148 hours).
Trephination and Suturing Techniques In all eyes, a central trephination was performed (donor trephination from the epithelial side) using the 193-nm excimer laser MEL60 (Aesculap-Meditec, Jena, Germany) along metal masks with eight “orientation teeth/notches.” Recipient diameters included 8.0 mm (45%), 7.5 mm (44%), and 7.0 mm (11%), with a graft oversize of 0.1 mm in all cases. A reproducible position of the eye relative to the excimer laser beam was assured by centering the limbus on the perpendicular HeNe aiming beam for both donor and recipient. The horizontal position of the limbal plane was achieved by using the focusing device of the laser at 3, 6, 9, and 12 o’clock at the limbus before focusing the laser at the trephination edge. For donor trephination from the epithelial side, a circular round metal aperture mask (central opening, 3.0 mm for centration; thickness, 0.5 mm; weight, 0.2 g; eight orientation teeth, 0.15⫻0.3 mm) was positioned on a corneoscleral button (16 mm diameter) fixed in an artificial anterior chamber (Polytech, Rossdorf, Germany) under microscopic control. The pressure within the artificial anterior chamber was adjusted to 20 mmHg. Using an automated rotation device for the artificial anterior chamber (4 rotations per
Table 2. Distribution of Simultaneous Lens Surgery for Three Different Graft Diameters in Percent (n ⫽ 489)
7.0 mm (n ⫽ 46) 7.5 mm (n ⫽ 214) 8.0 mm (n ⫽ 229) Overall
No (Penetrating Keratoplasty Only)
Triple Procedure
Intraocular Lens Exchange or Secondary Implantation
53 49 96 71
26 45 4 24
21 6 0 5
minute), 9786⫾2850 laser pulses (repetition rate, 25/second) were necessary for perforation. For recipient trephination exclusively performed with the manually guided excimer laser, a corresponding circular round metal mask was used (outer diameter, 12.9 mm; thickness, 0.5 mm; weight, 0.4 g; eight orientation notches, 0.15⫻0.3 mm). Before starting the trephination, centration relative to the limbus was achieved by repeatedly marking the patient’s cornea with the inner edge of the mask under microscopic control. For corneal perforation, 6398⫾1612 laser pulses (repetition rate, 25/second) were necessary. In 24% of eyes, an “open-sky” extracapsular cataract extraction and posterior chamber lens implantation were performed simultaneously (triple procedure), and 5% of eyes needed an additional intraocular lens exchange or additional secondary sclera-fixated intraocular lens (Table 2). In all patients, a peripheral iridotomy was performed at the 12-o’clock position.9 After temporary fixation of the donor button in the recipient bed with 8 interrupted sutures, a permanent wound closure was achieved by a double-running diagonal cross-stitch suture (10-0 nylon, 8 bites each) as described by Hoffmann (Fig 1).10 Finally, knots were buried in the stroma and all cardinal sutures were removed.
Assessment Methods and Main Outcome Measures Keratometry (Ophthalmometer, type H, 190071; Zeiss, Jena, Germany) and topography analysis (TMS-1; Tomey, Erlangen, Germany) 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. Main outcome measures included central corneal power (keratometric diopters), keratometric astigmatism, and regularity of keratometry or topography. Central corneal power was defined as a mean of powers in the steep and flat meridian of topography in diopters (D). Keratometric astigmatism was defined as the difference between powers in the steep and flat meridian of keratometry in diopters. The regularity of keratometry mires was graded semiquantitatively according to published criteria (0 ⫽ regular, 1 ⫽ mild irregular, 2 ⫽ moderate irregular, 3 ⫽ not measurable; Fig 2).11 In addition, the surface regularity index (SRI) and surface asymmetry index (SAI) of topography were recorded. The SRI is a measure of local fluctuations in central corneal power (4.5 mm diameter around the center of the entrance pupil) and correlates positively to the potential visual acuity that may be achieved with a respective cornea. When SRI is elevated, the corneal surface ahead of the entrance pupil will be irregular, leading to reduction in best spectacle-corrected visual acuity. Values of up to 1.01 are considered to be normal; values of up to 1.97 are considered to be suspect, and
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Figure 1. Typical double-running 10-0 nylon cross-stitch suture with 8 bites each (according to Hoffmann10 ) in macular corneal dystrophy (7.0/7.1 mm). 4
higher values are considered to be abnormal.12 The SAI measures the difference in corneal powers at every ring (180° apart) over the entire corneal surface. Adequate spectacle correction often is not achieved when SAI is high. Values of up to 0.42 are considered to be normal; values of up to 0.50 are considered to be suspect; and higher values are considered to be abnormal.12 Overall, mean follow-up was 24⫾18 months.
Statistical Analysis For statistical analysis, SPSS/PC 9.0 (Windows; SPSS Inc., Chicago, IL) was used. Comparisons between groups or variables were performed using nonparametric tests (Mann–Whitney U test for unpaired samples, Wilcoxon test for paired samples). A P value less than 0.05 was considered statistically significant.
Results With both sutures in, central corneal power in 7.0-mm (median, 42.0 D; P ⫽ 0.04) and in 7.5-mm grafts (median, 42.3 D; P ⫽ 0.007) was significantly lower than in 8.0-mm grafts (median, 43.0 D; Table 3). Keratometric astigmatism did not differ between groups (3.0 D vs. 3.0 D vs. 2.7 D; Table 4). 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 (P⬍0.01; Tables 5, 6). 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 (Table 7). With all sutures out, central corneal power in 7.0-mm grafts (median, 40.4 D) was significantly smaller than in 7.5-mm (median, 43.6 D; P ⫽ 0.04) and 8.0-mm grafts (median, 43.3 D; P ⫽ 0.04; Table 3). After suture removal, keratometric astigmatism did not increase and, again, keratometric astigmatism did not differ between groups (3.0 D vs. 3.2 D vs. 3.0 D; Table 4). After suture removal, SRI and SAI were significantly smaller than before in all groups (P⬍0.01). The SRI (1.40 vs. 1.09 vs. 0.84) and SAI (1.24
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Figure 2. Semiquantitative classification of regularity of keratometry mires (Ophthalmometer, type H, 190071; Zeiss, Jena, Germany; 0 ⫽ regular, 1 ⫽ mildly irregular, 2 ⫽ moderately irregular, 3 ⫽ not measurable).11
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature Table 3. Central Topographic Power in Diopters with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
42.8 41.9 ⫾ 4.2 43.4 43.1 ⫾ 3.7
42.8 42.6 ⫾ 3.4 44.3 44.0 ⫾ 3.1
43.9 43.6 ⫾ 2.9 44.3 44.3 ⫾ 2.7
vs. 0.83 vs. 0.62) decreased significantly with increasing diameter (P⬍0.01; Tables 5, 6). 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 (Table 7). Before and after suture removal, topographic astigmatism was significantly higher than keratometric astigmatism for all diameters (P⬍0.001; Table 4).
Discussion In high-risk corneal transplantations, preserving a clear graft is still the major concern of the microsurgeon and the immunologist. However, in non– high-risk PKs, which are exclusively demonstrated in the present study, a good optical performance of the clear graft appears to be mandatory, today. Hypothesizing that the properties of the wound bed are much more important for the final all-suture-out corneal curvature than various types of suture techniques or methods of suture adjustment, our goal was to optimize the trephination technique. Therefore, since 1986, we have been developing and optimizing the technique of nonmechanical laser trephination. The main advantage of this new cutting technique performed from the epithelial side in donor and recipient is the avoidance of mechanical distortion induced by radial and tangential forces during trephination, resulting in smooth, almost perpendicular cut edges that are congruent in donor and patient, thus avoiding vertical tilt.2,13 Additional creation of 8 orientation teeth at the graft margin and corresponding notches at the recipient margin for symmetric positioning of the cardinal sutures minimizes horiTable 4. Keratometric and Topographic Corneal Astigmatism in Diopters with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in Keratometric Topographic All sutures out Keratometric Topographic
7.0 mm
7.5 mm
8.0 mm
3.0 4.3 ⫾ 3.2 4.8 5.2 ⫾ 2.9
3.0 3.3 ⫾ 2.1 4.0 4.2 ⫾ 2.2
2.7 3.3 ⫾ 2.4 3.7 4.2 ⫾ 2.4
3.0 3.8 ⫾ 2.7 4.0 4.8 ⫾ 2.9
3.2 3.8 ⫾ 2.5 4.0 4.6 ⫾ 2.6
3.0 3.6 ⫾ 2.5 3.7 4.1 ⫾ 2.6
Table 5. Surface Regularity Index with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
1.66 1.69 ⫾ 0.58 1.40 1.50 ⫾ 0.54
1.43 1.43 ⫾ 0.52 1.09 1.15 ⫾ 0.48
1.11 1.21 ⫾ 0.55 0.84 0.93 ⫾ 0.54
zontal torsion.2,14 Furthermore, recipient and donor decentration may be reduced.15–17 These favorable impacts on major intraoperative determinants of postkeratoplasty astigmatism11 result in lower keratometric astigmatism, higher topographic regularity, and better visual acuity after suture removal.3,18 Besides less blood–aqueous barrier breakdown during the early postoperative time course after PK,19 laser trephination does not induce either cataract formation20 or higher endothelial cell loss of the graft.21 Likewise, the rates of immunologic graft rejection and secondary ocular hypertension are comparable using either technique.22,23 With conventional trephination, the donor typically is oversized by 0.25 to 0.5 mm to reduce crowding of the chamber angle and therefore postoperative “glaucoma.” This becomes necessary because the recipient hole generally is larger than intended with divergent cut angles, and the donor button (cut from the endothelial side) is generally smaller than intended with convergent cut angles (undercutting). In contrast, with laser trephination (donor from the epithelial side), attempted diameters are indeed achieved with congruent cut angels. Thus, donor oversize is not necessary to avoid chamber angle crowding. This theory has been corroborated clinically in a group of eyes with keratoconus and Fuchs’ dystrophy where glaucomatous disc cupping did not appear in any eye during a mean follow-up of 3.4 years after laser trephination.23 It has been supposed that smaller grafts may be associated with a higher postkeratoplasty astigmatism. However, the major findings of the present study were (1) a flatter curvature with smaller grafts; (2) a higher topographic irregularity with smaller grafts; (3) a higher proportion of not measurable keratometry mires with smaller grafts; (4) a tendency toward regularization of topography after suture removal; and (5) no difference concerning the amount of net astigmatism between different graft sizes either with or without sutures. The major reason for the flatter and more irregular graft with smaller diameters seems to be the closer position of the proximal suture ends in relation to the optical center of the Table 6. Surface Asymmetry Index with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
1.55 1.59 ⫾ 0.66 1.24 1.59 ⫾ 1.20
1.24 1.46 ⫾ 0.93 0.83 1.13 ⫾ 0.83
0.85 1.12 ⫾ 0.84 0.62 0.84 ⫾ 0.71
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Ophthalmology Volume 110, Number 11, November 2003 Table 7. Keratometric Irregularity* with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters
Both sutures in 0 1 2 3 All sutures out 0 1 2 3
7.0 mm
7.5 mm
8.0 mm
13 13 29 45
17 27 39 18
29 48 14 9
5 29 24 42
31 38 20 11
52 34 6 4
*0⫽regular, 1⫽mildly irregular, 2⫽moderately irregular, 3⫽not measurable (Seitz B, Langenbucher A, Naumann GOH. Astigmatismus bei Keratoplastik [Astigmatism after keratoplasty]. In: Seiler T, ed. Refraktive Chirurgie. Stuttgart: Enke-Verlag; 2000:197–252).
graft. This will be pronounced in particular with wider suture bites. After suture removal, the potentially topography-disturbing circular scar at the graft– host junction is located closer to the line of sight with smaller grafts. This may explain why overall the regularity of graft topography increases with suture removal but the principal differences between various graft sizes do persist. It is well known that the amount of graft oversize may have a particular impact on the central corneal steepness after PK.24 –26 In mechanical trephination, the diameter of the recipient bed tends to be larger and the diameter of the donor button tends to be smaller than the trephine diameter.27–29 Because this is not the case in laser trephination along corresponding metal masks (donor and host from the epithelial side), graft oversizing may not be necessary at all with this new technique. For the future, we are considering using an individualized approach toward oversizing the grafts in nonmechanical trephination to influence the postoperative spherical equivalent according to the special needs of our patients. Over the last decade, evidence in the literature has been increasing that there is no point at which postkeratoplasty corneal shape would be “stable” and preserved after suture removal.30 –33 The present study, however, demonstrates that nonmechanical trephination creating congruent wound margins in host and donor may prevent a major rise of astigmatism after suture removal. Furthermore, in a prospective randomized study comparing conventional and laser trephination, we found that after sequential removal of a double-running suture, keratometric astigmatism increased in 80% of eyes with conventional trephination, but further decreased in 52% of eyes with laser trephination. In addition, we found that fewer changes of the corneal curvature (central power and keratometric astigmatism) occurred after removal of the first in contrast to the second suture (Invest Ophthalmol Vis Sci 41[suppl]:S530, 2000). Meanwhile, it is well known that central power and astigmatism are overestimated by TMS-1 topography analysis in comparison with Zeiss keratometry.3,34 In addition, the amount of astigmatic correction that can be tolerated by the patients in their spectacles (refractive cylinder) typically
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is much less than the amount of keratometric or even topographic astigmatism.3,11,35 The reason for this is that only the spherical and astigmatic refractive errors can be corrected with spectacles, whereas other optical aberrations cannot be corrected.36 Accordingly, with a higher regularity of topography, the relative proportion of refractive cylinder will increase, allowing for better vision. In accordance with the present results, Lin et al37 reported a significant decrease of the SAI value from 1.17 before to 0.93 after suture removal, indicating that surface asymmetries may decrease after the removal of a singlerunning 10-0 nylon suture. Recent studies indicate that the rate of chronic endothelial cell loss after PK, which has been investigated intensively by Bourne et al38 for more than a decade, depends on the initial diagnosis.39 For this reason, eyes with bullous keratopathy—in contrast to what we did up to now—may require a larger graft not just to improve the optical performance but even more to transplant as many endothelial cells as possible. Nevertheless, graft size has to be judged by the surgeon individually in every single case before surgery to achieve the best compromise between immunologic purposes and optical quality.4,5 In conclusion, a smaller graft diameter results in a flatter curvature and a higher degree of topographic irregularity, but not in a higher amount of net astigmatism after PK. After suture removal, graft topography tends to regularize, whereas the principal differences between diameters do persist.
References 1. Naumann GO, Seitz B, Lang GK, et al. Excimer-Laser-193nm Trepanation bei der perforierenden Keratoplastik—Bericht u¨ ber die ersten 70 Patienten [193 excimer laser trepanation in perforating keratoplasty—report of 70 patients]. Klin Monatsbl Augenheilkd 1993;203:252– 61. 2. Naumann GO. Corneal transplantation in anterior segment diseases. The Bowman Lecture. Eye 1995;9:395– 421. 3. Seitz B, Langenbucher A, Kus MM, et al. Nonmechanical corneal trephination with the excimer laser improves outcome after penetrating keratoplasty. Ophthalmology 1999;106: 1156 – 65. 4. Seitz B, Langenbucher A, Zagrada D, et al. Hornhautdimensionen bei verschiedenen Hornhautdystrophien und ihre Bedeutung fu¨ r die perforierende Keratoplastik [Corneal dimensions in various types of corneal dystrophies and their effect on penetrating keratoplasty]. Klin Monatsbl Augenheilkd 2000;217:152– 8. 5. Price FW Jr, Whitson WE, Johns S, Gonzales JS. Risk factors of corneal graft failure. J Refract Surg 1996;12:134 – 43. 6. Troutman RC. Astigmatic considerations in corneal graft. Ophthalmic Surg 1979;10:21– 6. 7. Hoppenreijs VP, van Rij G, Beekhuis WH, et al. Causes of high astigmatism after penetrating keratoplasty. Doc Ophthalmol 1993;85:21–34. 8. Olson RJ. Modulation of postkeratoplasty astigmatism by surgical and suturing techniques. Int Ophthalmol Clin 1983; 23:137–51. 9. Naumann GOH, Sautter H. Surgical procedures on the cornea. In: Blodi FC, Mackensen G, Neubauer H, eds. Surgical Ophthalmology 1. Berlin: Springer, 1991:433–97.
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature 10. Hoffmann F. Nahttechnik bei perforierender Keratoplastik [Suture technique for perforating keratoplasty]. Klin Monatsbl Augenheilkd 1976;169:584 –90. 11. Seitz B, Langenbucher A, Naumann GOH. Astigmatismus bei Keratoplastik [Astigmatism after keratoplasty]. In: Seiler T, ed. Refraktive Chirurgie. Stuttgart: Enke-Verlag; 2000:197– 252. 12. Wilson SE, Klyce SD. Quantitative descriptors of corneal topography. A clinical study. Arch Ophthalmol 1991;109: 349 –53. 13. Langenbucher A, Seitz B, Kus MM, Naumann GO. Transplantatverkippung nach perforierender Keratoplastik—Vergleich zwischen nichtmechanischer Trepanation mittels Excimerlaser und Motortrepanation [Transplant vertical tilt after perforating keratoplasty— comparison between nonmechanical trepanation with excimer laser and motor trepanation]. Klin Monatsbl Augenheilkd 1998;212:129 – 40. 14. Behrens A, Seitz B, Ku¨ chle M, et al. “Orientation teeth” in non-mechanical laser corneal trephination for penetrating keratoplasty: 2.94 micron Er:YAG v 193 nm ArF excimer laser. Br J Ophthalmol 1999;83:1008 –12. 15. Langenbucher A, Seitz B, Kus MM, et al. Graft decentration in penetrating keratoplasty: nonmechanical trephination with the excimer laser (193 nm) versus the motor trephine. Ophthalmic Surg Lasers 1998;29:106 –13. 16. Seitz B, Langenbucher A, Meiller R, Kus MM. Dezentrierung der Spenderhornhaut bei mechanischer und Excimerlaser Trepanation fu¨ r die perforierende Keratoplastik [Decentration of donor cornea in mechanical and excimer laser trephination for penetrating keratoplasty]. Klin Monatsbl Augenheilkd 2000;217:144 –51. 17. Van Rij G, Cornell FM, Waring GO 3rd, et al. Postoperative astigmatism after central vs. eccentric penetrating keratoplasty. Am J Ophthalmol 1985;99:317–20. 18. Langenbucher A, Seitz B, Kus MM, et al. Regularita¨ t der Hornhauttopographie nach perforierender Keratoplastik— Vergleich zwischen nichtmechanischer (193nm Excimerlaser) und mechanischer Trepanation [Regularity of corneal topography after penetrating keratoplasty— comparison between nonmechanical (excimer laser 193 nm) and mechanical trepanation]. Klin Monatsbl Augenheilkd 1996;208:450 – 8. 19. Ku¨ chle M, Nguyen NX, Seitz B, et al. Blood-aqueous barrier following mechanical or nonmechanical excimer laser trephination in penetrating keratoplasty. Am J Ophthalmol 1998; 125:177– 81. 20. Behrens A, Seitz B, Langenbucher A, et al. Lens opacities after nonmechanical versus mechanical corneal trephination for penetrating keratoplasty in keratoconus. J Cataract Refract Surg 2000;26:1605–11. 21. Seitz B, Langenbucher A, Nguyen NX, et al. Graft endothelium and thickness after penetrating keratoplasty, comparing mechanical and excimer laser trephination: a prospective randomized study. Graefes Arch Clin Exp Ophthalmol 2001;239: 12–7. 22. Seitz B, Langenbucher A, Diamantis A, et al. Immunreaktionen nach perforierender Keratoplastik—Eine prospektive randomisierte Vergleichstudie zwischen Excimerlaser- und Motortrepanation [Immunological graft reactions after penetrating keratoplasty—a prospective randomized trial compar-
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32. 33. 34. 35. 36.
37. 38. 39.
ing corneal excimer laser and motor trephination]. Klin Monatsbl Augenheilkd 2001;218:710 –9. Seitz B, Langenbucher A, Nguyen NX, et al. Long-term follow-up of intraocular pressure after penetrating keratoplasty for keratoconus and Fuchs’ dystrophy: comparison of mechanical and excimer laser trephination. Cornea 2002;21: 368 –73. Wilson SE, Bourne WM. Effect of recipient-donor trephine size disparity on refractive error in keratoconus. Ophthalmology 1989;96:299 –305. Javadi MA, Mohammadi MJ, Mirdehghan SA, Sajjadi SH. A comparison between donor-recipient corneal size and its effect on the ultimate refractive error induced in keratoconus. Cornea 1993;12:401–5. Perl T, Charlton KH, Binder PS. Disparate diameter grafting. Astigmatism, intraocular pressure and visual acuity. Ophthalmology 1981;88:774 – 81. Pflugfelder SC, Roussel TJ, Denham D, et al. Photogrammetric analysis of corneal trephination. Arch Ophthalmol 1992; 110:1160 – 6. Van Rij G, Waring GO III. Configuration of corneal trephine opening using five different trephines in human donor eyes. Arch Ophthalmol 1988;106:1228 –33. Cohen KL, Tripoli NK, Pellom AC, et al. Effect of tissue fit on corneal shape after transplantation. Invest Ophthalmol Vis Sci 1984;25:1226 –31. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol 1988;105:637– 45. Filatov V, Alexandrakis G, Talamo JH, Steinert RF. Comparison of suture-in and suture-out postkeratoplasty astigmatism with single running suture or combined running and interrupted sutures. Am J Ophthalmol 1996;122:696 –700. Mader TH, Yuan R, Lynn MJ, et al. Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty. Ophthalmology 1993;100:119 –27. Musch DC, Meyer RF, Sugar A. The effect of removing running sutures on astigmatism after penetrating keratoplasty. Arch Ophthalmol 1988;106:488 –92. Karabatsas CH, Cook SD, Powell K, Sparrow JM. Comparison of keratometry and videokeratography after penetrating keratoplasty. J Refract Surg 1998;14:420 – 6. Judge D, Gordon L, Vander-Zwaag R, Wood TO. Refractive versus keratometric astigmatism post keratoplasty. Refract Corneal Surg 1990;6:174 – 8. Langenbucher A, Seitz B, Kus MM, Naumann GO. Zernike representation of corneal topography height data after nonmechanical penetrating keratoplasty. Invest Ophthalmol Vis Sci 1999;40:582–91. Lin DT, Wilson SE, Reidy JJ, et al. Topographic changes that occur with 10-0 running suture removal following penetrating keratoplasty. Refract Corneal Surg 1990;6:21–5. Bourne WM, Hodge DO, Nelson LR. Corneal endothelium five years after transplantation. Am J Ophthalmol 1994;118: 185–96. Langenbucher A, Seitz B, Nguyen NX, Naumann GO. Graft endothelial cell loss after nonmechanical penetrating keratoplasty depends on diagnosis: a regression analysis. Graefes Arch Clin Exp Ophthalmol 2002;240:387–92.
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performed by six microsurgeons using the 193-nm excimer laser in our Department of Ophthalmology in Erlangen, Germany.1,2 By far, the most frequent indications were keratoconus (n ⫽ 436), followed by Fuchs’ dystrophy (n ⫽ 254), bullous keratopathy (n ⫽ 210), and scars (n ⫽ 124). Especially for young patients with keratoconus, nonmechanical trephination offers clear advantages, such as reduction of keratometric astigmatism, higher regularity of corneal topography, and a significantly better visual acuity, which is the only truly relevant aspect for the patient.3 For immunologic purposes, the size of the graft should be chosen with respect to the individual size of the recipient cornea. It should be “as small as necessary, but as large as possible,”4,5 because smaller grafts are supposed to allow only for an inferior optical performance.6 – 8 At this time, it ISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(03)00659-6
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature Table 1. Distribution of Diagnoses for Three Different Graft Diameters in Percent (n ⫽ 489)
7.0 mm (n ⫽ 46) 7.5 mm (n ⫽ 214) 8.0 mm (n ⫽ 229) Overall
Keratoconus
Dystrophies
Bullous Keratopathy
Scars
7 10 93 48
26 60 3 31
47 16 2 11
20 14 2 10
is not clear what the reason is for this lower optical quality of smaller grafts. The purpose of this study was to assess the impact of graft diameter on corneal curvature (i.e., corneal power, amount and regularity of keratometric astigmatism) before and after removal of a double-running suture after nonmechanical PK.
Patients and Methods Patients and Donor Details In this prospective, nonrandomized, comparative (self-controlled) single-center clinical trial, 489 eyes with “two sutures in” (mean age, 52⫾19 years; 49% right eyes; 46% females) and 308 eyes with “all sutures out” were included. The diagnoses were keratoconus (48%), Fuchs’ and stromal dystrophies (31%), aphakic or pseudophakic bullous keratopathy (11%), and scars of various origin (10%; Table 1). Inclusion criteria were: primary central PK; recipient trephination, including 7.0 mm (age, 65⫾19 years), 7.5 mm (age, 62⫾17 years), and 8.0 mm (age, 38⫾12 years); graft oversize 0.1 mm; and double-running diagonal suture. Exclusion criteria were: elliptical keratoplasty, additional single sutures, and infectious keratitis (nonelective surgery). Institutional review board and ethics committee approval was not required for this study. Donor age varied from 8 to 93 years (median, 62 years), postmortem time varied from 1 to 72 hours (median, 10 hours), and, depending on the proportion of organ-cultured corneas (47%), preservation time varied from 3 to 720 hours (median, 148 hours).
Trephination and Suturing Techniques In all eyes, a central trephination was performed (donor trephination from the epithelial side) using the 193-nm excimer laser MEL60 (Aesculap-Meditec, Jena, Germany) along metal masks with eight “orientation teeth/notches.” Recipient diameters included 8.0 mm (45%), 7.5 mm (44%), and 7.0 mm (11%), with a graft oversize of 0.1 mm in all cases. A reproducible position of the eye relative to the excimer laser beam was assured by centering the limbus on the perpendicular HeNe aiming beam for both donor and recipient. The horizontal position of the limbal plane was achieved by using the focusing device of the laser at 3, 6, 9, and 12 o’clock at the limbus before focusing the laser at the trephination edge. For donor trephination from the epithelial side, a circular round metal aperture mask (central opening, 3.0 mm for centration; thickness, 0.5 mm; weight, 0.2 g; eight orientation teeth, 0.15⫻0.3 mm) was positioned on a corneoscleral button (16 mm diameter) fixed in an artificial anterior chamber (Polytech, Rossdorf, Germany) under microscopic control. The pressure within the artificial anterior chamber was adjusted to 20 mmHg. Using an automated rotation device for the artificial anterior chamber (4 rotations per
Table 2. Distribution of Simultaneous Lens Surgery for Three Different Graft Diameters in Percent (n ⫽ 489)
7.0 mm (n ⫽ 46) 7.5 mm (n ⫽ 214) 8.0 mm (n ⫽ 229) Overall
No (Penetrating Keratoplasty Only)
Triple Procedure
Intraocular Lens Exchange or Secondary Implantation
53 49 96 71
26 45 4 24
21 6 0 5
minute), 9786⫾2850 laser pulses (repetition rate, 25/second) were necessary for perforation. For recipient trephination exclusively performed with the manually guided excimer laser, a corresponding circular round metal mask was used (outer diameter, 12.9 mm; thickness, 0.5 mm; weight, 0.4 g; eight orientation notches, 0.15⫻0.3 mm). Before starting the trephination, centration relative to the limbus was achieved by repeatedly marking the patient’s cornea with the inner edge of the mask under microscopic control. For corneal perforation, 6398⫾1612 laser pulses (repetition rate, 25/second) were necessary. In 24% of eyes, an “open-sky” extracapsular cataract extraction and posterior chamber lens implantation were performed simultaneously (triple procedure), and 5% of eyes needed an additional intraocular lens exchange or additional secondary sclera-fixated intraocular lens (Table 2). In all patients, a peripheral iridotomy was performed at the 12-o’clock position.9 After temporary fixation of the donor button in the recipient bed with 8 interrupted sutures, a permanent wound closure was achieved by a double-running diagonal cross-stitch suture (10-0 nylon, 8 bites each) as described by Hoffmann (Fig 1).10 Finally, knots were buried in the stroma and all cardinal sutures were removed.
Assessment Methods and Main Outcome Measures Keratometry (Ophthalmometer, type H, 190071; Zeiss, Jena, Germany) and topography analysis (TMS-1; Tomey, Erlangen, Germany) 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. Main outcome measures included central corneal power (keratometric diopters), keratometric astigmatism, and regularity of keratometry or topography. Central corneal power was defined as a mean of powers in the steep and flat meridian of topography in diopters (D). Keratometric astigmatism was defined as the difference between powers in the steep and flat meridian of keratometry in diopters. The regularity of keratometry mires was graded semiquantitatively according to published criteria (0 ⫽ regular, 1 ⫽ mild irregular, 2 ⫽ moderate irregular, 3 ⫽ not measurable; Fig 2).11 In addition, the surface regularity index (SRI) and surface asymmetry index (SAI) of topography were recorded. The SRI is a measure of local fluctuations in central corneal power (4.5 mm diameter around the center of the entrance pupil) and correlates positively to the potential visual acuity that may be achieved with a respective cornea. When SRI is elevated, the corneal surface ahead of the entrance pupil will be irregular, leading to reduction in best spectacle-corrected visual acuity. Values of up to 1.01 are considered to be normal; values of up to 1.97 are considered to be suspect, and
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Figure 1. Typical double-running 10-0 nylon cross-stitch suture with 8 bites each (according to Hoffmann10 ) in macular corneal dystrophy (7.0/7.1 mm). 4
higher values are considered to be abnormal.12 The SAI measures the difference in corneal powers at every ring (180° apart) over the entire corneal surface. Adequate spectacle correction often is not achieved when SAI is high. Values of up to 0.42 are considered to be normal; values of up to 0.50 are considered to be suspect; and higher values are considered to be abnormal.12 Overall, mean follow-up was 24⫾18 months.
Statistical Analysis For statistical analysis, SPSS/PC 9.0 (Windows; SPSS Inc., Chicago, IL) was used. Comparisons between groups or variables were performed using nonparametric tests (Mann–Whitney U test for unpaired samples, Wilcoxon test for paired samples). A P value less than 0.05 was considered statistically significant.
Results With both sutures in, central corneal power in 7.0-mm (median, 42.0 D; P ⫽ 0.04) and in 7.5-mm grafts (median, 42.3 D; P ⫽ 0.007) was significantly lower than in 8.0-mm grafts (median, 43.0 D; Table 3). Keratometric astigmatism did not differ between groups (3.0 D vs. 3.0 D vs. 2.7 D; Table 4). 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 (P⬍0.01; Tables 5, 6). 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 (Table 7). With all sutures out, central corneal power in 7.0-mm grafts (median, 40.4 D) was significantly smaller than in 7.5-mm (median, 43.6 D; P ⫽ 0.04) and 8.0-mm grafts (median, 43.3 D; P ⫽ 0.04; Table 3). After suture removal, keratometric astigmatism did not increase and, again, keratometric astigmatism did not differ between groups (3.0 D vs. 3.2 D vs. 3.0 D; Table 4). After suture removal, SRI and SAI were significantly smaller than before in all groups (P⬍0.01). The SRI (1.40 vs. 1.09 vs. 0.84) and SAI (1.24
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Figure 2. Semiquantitative classification of regularity of keratometry mires (Ophthalmometer, type H, 190071; Zeiss, Jena, Germany; 0 ⫽ regular, 1 ⫽ mildly irregular, 2 ⫽ moderately irregular, 3 ⫽ not measurable).11
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature Table 3. Central Topographic Power in Diopters with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
42.8 41.9 ⫾ 4.2 43.4 43.1 ⫾ 3.7
42.8 42.6 ⫾ 3.4 44.3 44.0 ⫾ 3.1
43.9 43.6 ⫾ 2.9 44.3 44.3 ⫾ 2.7
vs. 0.83 vs. 0.62) decreased significantly with increasing diameter (P⬍0.01; Tables 5, 6). 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 (Table 7). Before and after suture removal, topographic astigmatism was significantly higher than keratometric astigmatism for all diameters (P⬍0.001; Table 4).
Discussion In high-risk corneal transplantations, preserving a clear graft is still the major concern of the microsurgeon and the immunologist. However, in non– high-risk PKs, which are exclusively demonstrated in the present study, a good optical performance of the clear graft appears to be mandatory, today. Hypothesizing that the properties of the wound bed are much more important for the final all-suture-out corneal curvature than various types of suture techniques or methods of suture adjustment, our goal was to optimize the trephination technique. Therefore, since 1986, we have been developing and optimizing the technique of nonmechanical laser trephination. The main advantage of this new cutting technique performed from the epithelial side in donor and recipient is the avoidance of mechanical distortion induced by radial and tangential forces during trephination, resulting in smooth, almost perpendicular cut edges that are congruent in donor and patient, thus avoiding vertical tilt.2,13 Additional creation of 8 orientation teeth at the graft margin and corresponding notches at the recipient margin for symmetric positioning of the cardinal sutures minimizes horiTable 4. Keratometric and Topographic Corneal Astigmatism in Diopters with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in Keratometric Topographic All sutures out Keratometric Topographic
7.0 mm
7.5 mm
8.0 mm
3.0 4.3 ⫾ 3.2 4.8 5.2 ⫾ 2.9
3.0 3.3 ⫾ 2.1 4.0 4.2 ⫾ 2.2
2.7 3.3 ⫾ 2.4 3.7 4.2 ⫾ 2.4
3.0 3.8 ⫾ 2.7 4.0 4.8 ⫾ 2.9
3.2 3.8 ⫾ 2.5 4.0 4.6 ⫾ 2.6
3.0 3.6 ⫾ 2.5 3.7 4.1 ⫾ 2.6
Table 5. Surface Regularity Index with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
1.66 1.69 ⫾ 0.58 1.40 1.50 ⫾ 0.54
1.43 1.43 ⫾ 0.52 1.09 1.15 ⫾ 0.48
1.11 1.21 ⫾ 0.55 0.84 0.93 ⫾ 0.54
zontal torsion.2,14 Furthermore, recipient and donor decentration may be reduced.15–17 These favorable impacts on major intraoperative determinants of postkeratoplasty astigmatism11 result in lower keratometric astigmatism, higher topographic regularity, and better visual acuity after suture removal.3,18 Besides less blood–aqueous barrier breakdown during the early postoperative time course after PK,19 laser trephination does not induce either cataract formation20 or higher endothelial cell loss of the graft.21 Likewise, the rates of immunologic graft rejection and secondary ocular hypertension are comparable using either technique.22,23 With conventional trephination, the donor typically is oversized by 0.25 to 0.5 mm to reduce crowding of the chamber angle and therefore postoperative “glaucoma.” This becomes necessary because the recipient hole generally is larger than intended with divergent cut angles, and the donor button (cut from the endothelial side) is generally smaller than intended with convergent cut angles (undercutting). In contrast, with laser trephination (donor from the epithelial side), attempted diameters are indeed achieved with congruent cut angels. Thus, donor oversize is not necessary to avoid chamber angle crowding. This theory has been corroborated clinically in a group of eyes with keratoconus and Fuchs’ dystrophy where glaucomatous disc cupping did not appear in any eye during a mean follow-up of 3.4 years after laser trephination.23 It has been supposed that smaller grafts may be associated with a higher postkeratoplasty astigmatism. However, the major findings of the present study were (1) a flatter curvature with smaller grafts; (2) a higher topographic irregularity with smaller grafts; (3) a higher proportion of not measurable keratometry mires with smaller grafts; (4) a tendency toward regularization of topography after suture removal; and (5) no difference concerning the amount of net astigmatism between different graft sizes either with or without sutures. The major reason for the flatter and more irregular graft with smaller diameters seems to be the closer position of the proximal suture ends in relation to the optical center of the Table 6. Surface Asymmetry Index with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters (Median, Mean ⫾ Standard Deviation)
Both sutures in All sutures out
7.0 mm
7.5 mm
8.0 mm
1.55 1.59 ⫾ 0.66 1.24 1.59 ⫾ 1.20
1.24 1.46 ⫾ 0.93 0.83 1.13 ⫾ 0.83
0.85 1.12 ⫾ 0.84 0.62 0.84 ⫾ 0.71
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Ophthalmology Volume 110, Number 11, November 2003 Table 7. Keratometric Irregularity* with Both Sutures In and All Sutures Out, Comparing Three Different Graft Diameters
Both sutures in 0 1 2 3 All sutures out 0 1 2 3
7.0 mm
7.5 mm
8.0 mm
13 13 29 45
17 27 39 18
29 48 14 9
5 29 24 42
31 38 20 11
52 34 6 4
*0⫽regular, 1⫽mildly irregular, 2⫽moderately irregular, 3⫽not measurable (Seitz B, Langenbucher A, Naumann GOH. Astigmatismus bei Keratoplastik [Astigmatism after keratoplasty]. In: Seiler T, ed. Refraktive Chirurgie. Stuttgart: Enke-Verlag; 2000:197–252).
graft. This will be pronounced in particular with wider suture bites. After suture removal, the potentially topography-disturbing circular scar at the graft– host junction is located closer to the line of sight with smaller grafts. This may explain why overall the regularity of graft topography increases with suture removal but the principal differences between various graft sizes do persist. It is well known that the amount of graft oversize may have a particular impact on the central corneal steepness after PK.24 –26 In mechanical trephination, the diameter of the recipient bed tends to be larger and the diameter of the donor button tends to be smaller than the trephine diameter.27–29 Because this is not the case in laser trephination along corresponding metal masks (donor and host from the epithelial side), graft oversizing may not be necessary at all with this new technique. For the future, we are considering using an individualized approach toward oversizing the grafts in nonmechanical trephination to influence the postoperative spherical equivalent according to the special needs of our patients. Over the last decade, evidence in the literature has been increasing that there is no point at which postkeratoplasty corneal shape would be “stable” and preserved after suture removal.30 –33 The present study, however, demonstrates that nonmechanical trephination creating congruent wound margins in host and donor may prevent a major rise of astigmatism after suture removal. Furthermore, in a prospective randomized study comparing conventional and laser trephination, we found that after sequential removal of a double-running suture, keratometric astigmatism increased in 80% of eyes with conventional trephination, but further decreased in 52% of eyes with laser trephination. In addition, we found that fewer changes of the corneal curvature (central power and keratometric astigmatism) occurred after removal of the first in contrast to the second suture (Invest Ophthalmol Vis Sci 41[suppl]:S530, 2000). Meanwhile, it is well known that central power and astigmatism are overestimated by TMS-1 topography analysis in comparison with Zeiss keratometry.3,34 In addition, the amount of astigmatic correction that can be tolerated by the patients in their spectacles (refractive cylinder) typically
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is much less than the amount of keratometric or even topographic astigmatism.3,11,35 The reason for this is that only the spherical and astigmatic refractive errors can be corrected with spectacles, whereas other optical aberrations cannot be corrected.36 Accordingly, with a higher regularity of topography, the relative proportion of refractive cylinder will increase, allowing for better vision. In accordance with the present results, Lin et al37 reported a significant decrease of the SAI value from 1.17 before to 0.93 after suture removal, indicating that surface asymmetries may decrease after the removal of a singlerunning 10-0 nylon suture. Recent studies indicate that the rate of chronic endothelial cell loss after PK, which has been investigated intensively by Bourne et al38 for more than a decade, depends on the initial diagnosis.39 For this reason, eyes with bullous keratopathy—in contrast to what we did up to now—may require a larger graft not just to improve the optical performance but even more to transplant as many endothelial cells as possible. Nevertheless, graft size has to be judged by the surgeon individually in every single case before surgery to achieve the best compromise between immunologic purposes and optical quality.4,5 In conclusion, a smaller graft diameter results in a flatter curvature and a higher degree of topographic irregularity, but not in a higher amount of net astigmatism after PK. After suture removal, graft topography tends to regularize, whereas the principal differences between diameters do persist.
References 1. Naumann GO, Seitz B, Lang GK, et al. Excimer-Laser-193nm Trepanation bei der perforierenden Keratoplastik—Bericht u¨ ber die ersten 70 Patienten [193 excimer laser trepanation in perforating keratoplasty—report of 70 patients]. Klin Monatsbl Augenheilkd 1993;203:252– 61. 2. Naumann GO. Corneal transplantation in anterior segment diseases. The Bowman Lecture. Eye 1995;9:395– 421. 3. Seitz B, Langenbucher A, Kus MM, et al. Nonmechanical corneal trephination with the excimer laser improves outcome after penetrating keratoplasty. Ophthalmology 1999;106: 1156 – 65. 4. Seitz B, Langenbucher A, Zagrada D, et al. Hornhautdimensionen bei verschiedenen Hornhautdystrophien und ihre Bedeutung fu¨ r die perforierende Keratoplastik [Corneal dimensions in various types of corneal dystrophies and their effect on penetrating keratoplasty]. Klin Monatsbl Augenheilkd 2000;217:152– 8. 5. Price FW Jr, Whitson WE, Johns S, Gonzales JS. Risk factors of corneal graft failure. J Refract Surg 1996;12:134 – 43. 6. Troutman RC. Astigmatic considerations in corneal graft. Ophthalmic Surg 1979;10:21– 6. 7. Hoppenreijs VP, van Rij G, Beekhuis WH, et al. Causes of high astigmatism after penetrating keratoplasty. Doc Ophthalmol 1993;85:21–34. 8. Olson RJ. Modulation of postkeratoplasty astigmatism by surgical and suturing techniques. Int Ophthalmol Clin 1983; 23:137–51. 9. Naumann GOH, Sautter H. Surgical procedures on the cornea. In: Blodi FC, Mackensen G, Neubauer H, eds. Surgical Ophthalmology 1. Berlin: Springer, 1991:433–97.
Seitz et al 䡠 Impact of Graft Diameter on Postkeratoplasty Corneal Curvature 10. Hoffmann F. Nahttechnik bei perforierender Keratoplastik [Suture technique for perforating keratoplasty]. Klin Monatsbl Augenheilkd 1976;169:584 –90. 11. Seitz B, Langenbucher A, Naumann GOH. Astigmatismus bei Keratoplastik [Astigmatism after keratoplasty]. In: Seiler T, ed. Refraktive Chirurgie. Stuttgart: Enke-Verlag; 2000:197– 252. 12. Wilson SE, Klyce SD. Quantitative descriptors of corneal topography. A clinical study. Arch Ophthalmol 1991;109: 349 –53. 13. Langenbucher A, Seitz B, Kus MM, Naumann GO. Transplantatverkippung nach perforierender Keratoplastik—Vergleich zwischen nichtmechanischer Trepanation mittels Excimerlaser und Motortrepanation [Transplant vertical tilt after perforating keratoplasty— comparison between nonmechanical trepanation with excimer laser and motor trepanation]. Klin Monatsbl Augenheilkd 1998;212:129 – 40. 14. Behrens A, Seitz B, Ku¨ chle M, et al. “Orientation teeth” in non-mechanical laser corneal trephination for penetrating keratoplasty: 2.94 micron Er:YAG v 193 nm ArF excimer laser. Br J Ophthalmol 1999;83:1008 –12. 15. Langenbucher A, Seitz B, Kus MM, et al. Graft decentration in penetrating keratoplasty: nonmechanical trephination with the excimer laser (193 nm) versus the motor trephine. Ophthalmic Surg Lasers 1998;29:106 –13. 16. Seitz B, Langenbucher A, Meiller R, Kus MM. Dezentrierung der Spenderhornhaut bei mechanischer und Excimerlaser Trepanation fu¨ r die perforierende Keratoplastik [Decentration of donor cornea in mechanical and excimer laser trephination for penetrating keratoplasty]. Klin Monatsbl Augenheilkd 2000;217:144 –51. 17. Van Rij G, Cornell FM, Waring GO 3rd, et al. Postoperative astigmatism after central vs. eccentric penetrating keratoplasty. Am J Ophthalmol 1985;99:317–20. 18. Langenbucher A, Seitz B, Kus MM, et al. Regularita¨ t der Hornhauttopographie nach perforierender Keratoplastik— Vergleich zwischen nichtmechanischer (193nm Excimerlaser) und mechanischer Trepanation [Regularity of corneal topography after penetrating keratoplasty— comparison between nonmechanical (excimer laser 193 nm) and mechanical trepanation]. Klin Monatsbl Augenheilkd 1996;208:450 – 8. 19. Ku¨ chle M, Nguyen NX, Seitz B, et al. Blood-aqueous barrier following mechanical or nonmechanical excimer laser trephination in penetrating keratoplasty. Am J Ophthalmol 1998; 125:177– 81. 20. Behrens A, Seitz B, Langenbucher A, et al. Lens opacities after nonmechanical versus mechanical corneal trephination for penetrating keratoplasty in keratoconus. J Cataract Refract Surg 2000;26:1605–11. 21. Seitz B, Langenbucher A, Nguyen NX, et al. Graft endothelium and thickness after penetrating keratoplasty, comparing mechanical and excimer laser trephination: a prospective randomized study. Graefes Arch Clin Exp Ophthalmol 2001;239: 12–7. 22. Seitz B, Langenbucher A, Diamantis A, et al. Immunreaktionen nach perforierender Keratoplastik—Eine prospektive randomisierte Vergleichstudie zwischen Excimerlaser- und Motortrepanation [Immunological graft reactions after penetrating keratoplasty—a prospective randomized trial compar-
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37. 38. 39.
ing corneal excimer laser and motor trephination]. Klin Monatsbl Augenheilkd 2001;218:710 –9. Seitz B, Langenbucher A, Nguyen NX, et al. Long-term follow-up of intraocular pressure after penetrating keratoplasty for keratoconus and Fuchs’ dystrophy: comparison of mechanical and excimer laser trephination. Cornea 2002;21: 368 –73. Wilson SE, Bourne WM. Effect of recipient-donor trephine size disparity on refractive error in keratoconus. Ophthalmology 1989;96:299 –305. Javadi MA, Mohammadi MJ, Mirdehghan SA, Sajjadi SH. A comparison between donor-recipient corneal size and its effect on the ultimate refractive error induced in keratoconus. Cornea 1993;12:401–5. Perl T, Charlton KH, Binder PS. Disparate diameter grafting. Astigmatism, intraocular pressure and visual acuity. Ophthalmology 1981;88:774 – 81. Pflugfelder SC, Roussel TJ, Denham D, et al. Photogrammetric analysis of corneal trephination. Arch Ophthalmol 1992; 110:1160 – 6. Van Rij G, Waring GO III. Configuration of corneal trephine opening using five different trephines in human donor eyes. Arch Ophthalmol 1988;106:1228 –33. Cohen KL, Tripoli NK, Pellom AC, et al. Effect of tissue fit on corneal shape after transplantation. Invest Ophthalmol Vis Sci 1984;25:1226 –31. Binder PS. The effect of suture removal on postkeratoplasty astigmatism. Am J Ophthalmol 1988;105:637– 45. Filatov V, Alexandrakis G, Talamo JH, Steinert RF. Comparison of suture-in and suture-out postkeratoplasty astigmatism with single running suture or combined running and interrupted sutures. Am J Ophthalmol 1996;122:696 –700. Mader TH, Yuan R, Lynn MJ, et al. Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty. Ophthalmology 1993;100:119 –27. Musch DC, Meyer RF, Sugar A. The effect of removing running sutures on astigmatism after penetrating keratoplasty. Arch Ophthalmol 1988;106:488 –92. Karabatsas CH, Cook SD, Powell K, Sparrow JM. Comparison of keratometry and videokeratography after penetrating keratoplasty. J Refract Surg 1998;14:420 – 6. Judge D, Gordon L, Vander-Zwaag R, Wood TO. Refractive versus keratometric astigmatism post keratoplasty. Refract Corneal Surg 1990;6:174 – 8. Langenbucher A, Seitz B, Kus MM, Naumann GO. Zernike representation of corneal topography height data after nonmechanical penetrating keratoplasty. Invest Ophthalmol Vis Sci 1999;40:582–91. Lin DT, Wilson SE, Reidy JJ, et al. Topographic changes that occur with 10-0 running suture removal following penetrating keratoplasty. Refract Corneal Surg 1990;6:21–5. Bourne WM, Hodge DO, Nelson LR. Corneal endothelium five years after transplantation. Am J Ophthalmol 1994;118: 185–96. Langenbucher A, Seitz B, Nguyen NX, Naumann GO. Graft endothelial cell loss after nonmechanical penetrating keratoplasty depends on diagnosis: a regression analysis. Graefes Arch Clin Exp Ophthalmol 2002;240:387–92.
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