An adjustable single running suture technique to reduce postkeratoplasty astigmatism. A preliminary report

Managing Post Keratoplasty Astigmatism

Corneal transplantation, when used in the correct setting, can significantly improve visual acuity and therefore quality of life. One of the barriers to good vision following keratoplasty is residual post operative surgical astigmatism. Following a thorough literature search, we present the different options available to readers, with regards to how post-operative astigmatism can be approached and managed in order to improve vision. We present available data from the literature, which in some areas are scarce, with a view to collating all of this information in one place, allowing comparison between different modalities of treatment.

Update on Suture Techniques in Corneal Transplantation: A Systematic Review

Effective suturing remains key to achieving successful outcomes in corneal surgery, especially anterior lamellar keratoplasty and full thickness transplantation. Limitations in the technique may result in complications such as wound leak, infection, or high astigmatism post corneal graft. By using a systematic approach, this study reviews articles and conducts content analysis based on update 2020 PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria). The aim of this paper is to summarize the state of the art of corneal suturing techniques for every type of corneal transplant and patient age and also their outcomes regarding astigmatism and complications. Future developments for corneal transplantation will be also discussed. This is important because especially the young surgeon must have knowledge of the implications of every suture performed in order to achieve consistent and predictable post-operative outcomes and also be aware of all the possible complications.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Management of post-keratoplasty astigmatism

Post-keratoplasty astigmatism remains a challenge for corneorefractive surgeons. While maintaining a healthy graft is the most crucial issue in keratoplasty procedures, astigmatism is a limiting factor in the visual rehabilitation of otherwise successful corneal grafts. The management of post-keratoplasty astigmatism takes place at 2 stages: when sutures are still present at the graft-host junction and when all sutures have been removed. Excessive suture-in post-keratoplasty astigmatism is usually managed by selective suture manipulation, ie, suture adjustment and/or suture removal along the steep meridian of astigmatism. A small amount of suture-out post-keratoplasty astigmatism can be managed by spectacles. Higher magnitudes of astigmatism can be addressed by contact lenses or surgical intervention, such as relaxing and compressing procedures. Laser lamellar refractive surgery can also be used to manage post-keratoplasty astigmatism, and toric phakic intraocular lenses have recently been recommended. In this review, we discuss the etiology and management of post-keratoplasty astigmatism and provide recommendations and tips to minimize it.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Does the type of suturing technique used affect astigmatism after deep anterior lamellar keratoplasty in keratoconus patients?

PURPOSE

To compare the effect of three different suturing techniques on astigmatism after deep anterior lamellar keratoplasty (DALK) in patients with keratoconus.

METHODS

In this retrospective study, 54 eyes of 54 patients with advanced keratoconus underwent DALK with three suturing techniques: single running, interrupted running, and combined interrupted and running. Postkeratoplasty astigmatism was evaluated during examinations 1, 3, and 6 months postoperatively and 2 months after completing suture removal.

RESULTS

Twenty-four eyes had single running sutures, 16 eyes had interrupted sutures, and in 14 eyes the suturing technique used was combined interrupted and running sutures. Mean age was 25.6 ± 5.9 years, 27.3 ± 6.8 years, and 26.5 ± 5.7 years (P = 0.422), and postoperative astigmatism 1 month after surgery was 3.79 ± 1.19 D, 5.56 ± 1.78 D, and 4.21 ± 1.55 D in the three groups, respectively (P = 0.012). However, 2 months after completing the suture removal, final postoperative astigmatism was 3.43 ± 1.44 D, 3.87 ± 1.38 D, and 3.71 ± 1.46 D (P = 0.846). Final astigmatism less than 4 D was seen in 18 cases (75%) in the single running group, nine cases (56.2%) in the interrupted running group, and nine cases (64.2%) in the combined interrupted and running group (P = 0.08).

CONCLUSION

Postkeratoplasty astigmatism is comparable with three different suturing techniques used in patients with keratoconus after completing suture removal in DALK. Due to earlier suture removal in DALK, the type of suturing technique used is not considerably important.

Surgical approaches to corneal wound healing

New approaches to improving corneal epithelial wound healing include stromal puncture and removal of abnormal basement membrane material by excimer laser ablation (phototherapeutic keratectomy). Non-healing corneal erosions and chemical burns may also benefit from laser excision of the damaged surface to permit more normal epithelial attachments. Reduction of postsurgical astigmatism may be facilitated by adjustable sutures after penetrating keratoplasty or by molding the cornea with the use of a rigid contact lens in the immediate postoperative period.

Comparison of the effect of three suturing techniques on postkeratoplasty astigmatism in keratoconus

PURPOSE

To compare the effect of 3 common suturing techniques on postkeratoplasty astigmatism and final best corrected visual acuity (BCVA) in patients with keratoconus.

METHODS

In this randomized clinical trial, 103 eyes of 103 patients with advanced keratoconus, who were contact lens intolerant, or with contact lens-corrected visual acuity less than 20/80, underwent penetrating keratoplasty with 3 suturing techniques: interrupted (IR), single running (SR), and combined interrupted and running (CIR). Postkeratoplasty astigmatism and BCVA were evaluated during regular examinations 1.5, 3, 6, and 12 months postoperatively and 2 months after complete suture removal. Suture adjustment and selective suture removal were performed 2 to 6 weeks and after 3 months in eyes with more than 4 D of corneal astigmatism in the SR and IR/CIR groups, respectively.

RESULTS

Of 87 patients who completed follow-up, 26 eyes underwent PK with interrupted suturing technique (IR), 26 eyes had single running sutures (SR), and in 35 eyes, the suturing technique was combined (interrupted + running sutures; CIR). Mean age was 27.2 +/- 8.4, 28.9 +/- 8.7, and 30.3 +/- 8.7 years, and postoperative astigmatism 1.5 months after surgery was 3.77 +/- 1.68, 5.48 +/- 2.09, and 4.10 +/- 1.79 D in the 3 groups, respectively (P = 0.015). However, 2 months after complete suture removal, final postoperative astigmatism was 3.83 +/- 1.65, 3.37 +/- 1.9, and 3.88 +/- 2.79 D (P = 0.851) and BCVA (log MAR) was 0.08 +/- 0.14, 0.13 +/- 0.23, and 0.09 +/- 0.16, respectively (P = 0.53). Immunologic endothelial rejection reactions were seen in 5 eyes (19.2%) in the IR group, 3 eyes (11.72%) in the SR group, and 6 eyes (17.64%) in the CIR group (P = 0.44). There was no case of graft failure during the follow-up period.

CONCLUSION

Postkeratoplasty astigmatism and BCVA are comparable with the 3 common suturing techniques (IR, SR, and CIR) in patients with keratoconus, provided that regular postoperative examinations and topography-guided suture adjustment and/or removal are performed.

Fourier Analysis of Single Running Suture Adjustment in Penetrating and Deep Lamellar Keratoplasty

PURPOSE

To prospectively evaluate clinical and visual results of running suture adjustment after keratoplasty.

METHODS

Thirty-seven eyes of 33 patients received running suture adjustment after keratoplasty. Changes in uncorrected visual acuity, distance best spectacle-corrected visual acuity (BSCVA), refraction, and Fourier analysis constituents were assessed before and after suture adjustment.

RESULTS

Thirty eyes, which had improvement of distance BSCVA soon after suture adjustment, maintained improvement at 1 year, whereas 7 eyes with decreased distance BSCVA soon after suture adjustment experienced no improvement at 1 year. Patients with poor distance BSCVA at 1 year had significantly higher high order irregularity than patients with better distance BSCVA despite similar cylindrical power outcomes.

A Review of Randomized Controlled Trials of Penetrating Keratoplasty Techniques

PURPOSE

To assess the effects of variations in operative technique on the outcomes of penetrating keratoplasty (PK).

METHOD

Systematic literature review of published randomized controlled trials of operative techniques in PK.

MAIN OUTCOME MEASURES

Visual acuity, refractive error, endothelial cell density, graft rejection, intraocular pressure (IOP), and other surgical complications.

RESULTS

Twenty-seven trials were identified. Many involved small numbers, some of which were probably compromised by inadequate statistical power. There was some limited evidence from a small number of studies (usually 1 or 2) for preoperative cauterization of the cone in keratoconus, excimer laser trephination, taking into account the effect of trephine sizing on postoperative IOP, taking into account the effect of trephine sizing on postoperative spherical equivalent, using sodium hyaluronate, avoiding vitrectomy if possible, using an iris-fixated posterior chamber lens implant in the absence of capsular support, and adjusting a single continuous suture intraoperatively if used. However, there was little convincing evidence for choosing interrupted suturing versus continuous suturing or for an effect of suturing on final sutures-out astigmatism. Likewise, there was no convincing evidence for the superiority of any lamellar alternative to PK for deep stromal disease. Overall, most of the effects of changing technique were small, and there was no evidence for the superiority of any specific technique in terms of improved quality of life or cost-effectiveness.

CONCLUSIONS

There is a need for further studies with which to refine decision-making as regards the choice of operative techniques in PK.

Refractive outcome of single running suture adjustment in penetrating keratoplasty

PURPOSE

To evaluate the effectiveness of single running suture adjustment in reducing postoperative astigmatism and improving visual acuity in patients who have undergone penetrating keratoplasty.

METHODS

Eighteen eyes of 18 patients who underwent penetrating keratoplasty at the Department of Ophthalmology, Başkent University between May 1997 and December 2000 and who had an astigmatism over 2 diopters (D) at the fourth postoperative week were included. All eyes underwent suture adjustment at the fourth week and eight eyes with residual astigmatism above 3 D underwent a second adjustment at the eighth week. Final astigmatism and visual acuity findings were evaluated 28 weeks postoperatively.

RESULTS

The mean postoperative keratometric and refractive astigmatism were 5.76 +/- 0.88 D (range=4.50-7.76) and 5.22 +/- 0.78 D (range=4.0-7.0) at the fourth week, which were decreased to 2.82 +/- 0.99 D (range=1.25-4.62, p=0.0001) and 2.61 +/- 1.01 D (range= 1.0-4.5, p=0.0001) after suture adjustment, respectively. In eight eyes at the eighth week, a second suture adjustment reduced the average keratometric and refractive astigmatism from 3.86 +/- 0.65 D (range=2.75-4.62) and 3.81 +/- 0.44 D (range=3.25-4.50) to 2.33 +/- 0.91 D (range=0.87-3.50, p=0.012) and 2.06 +/- 0.68 D (range=1.0-2.75, p=0.011), respectively. At the 28th week, the average keratometric and refractive astigmatism levels for the entire cohort, which were 2.39 +/- 1.06 D (range=1.0-3.50) and 2.25 +/- 0.96 D (range=1.0-3.25), respectively, showed a statistically significant decrease when compared with the levels before the first suture adjustment (p=0.0001 for both data). The mean best-corrected visual acuity was 20/25 on the Snellen chart at the 28th week.

CONCLUSIONS

Postoperative adjustment of single running suture is a safe and effective way of reducing postkeratoplasty astigmatism.

Keratometric astigmatism after suture removal in penetrating keratoplasty: double running versus single running suture techniques

BACKGROUND AND OBJECTIVE

To compare astigmatism after suture removal in a retrospective sequential series of patients who had penetrating keratoplasty with either a double running suture technique or an adjustable single running suture technique. During the first year postkeratoplasty, when sutures were in place, the latter technique had produced less astigmatism.

MATERIALS AND METHODS

Keratometry and keratometric astigmatism were measured before and after suture removal. We compared these variables in 30 grafts with the double running suture technique to the same variables in 24 grafts with the single running suture technique.

RESULTS

The final portion of the double running suture was removed 408 +/- 177 (mean +/- SD) days after keratoplasty, whereas the single running suture was removed 611 +/- 224 days after keratoplasty (P<0.001). After suture removal, there was no difference between the double running and single running groups in either mean keratometry [46.5 +/- 1.8 diopters (D) versus 45.6 +/- 2.0 D, P=0.09, minimum detectable difference (MDD)=1.5D] or mean astigmatism (4.6 +/- 2.7 D versus 5.2 +/- 3.2D, P=0.72, MDD=2.3).

CONCLUSION

In this consecutive series of corneal transplants performed by one surgeon, the results suggest no difference in astigmatism between the two suturing techniques after all sutures have been removed.

Shortterm and longterm visual and astigmatic results of an opposing 10-0 nylon double running suture technique for penetrating keratoplasty

BACKGROUND

In ophthalmic surgery, corneal transplantation (penetrating keratoplasty) may be employed when the clarity of the cornea has been significantly compromised by conditions such as scarring, edema, and variable corneal thickness. Irregularities in corneal curvature can occur postoperatively. This astigmatism is of concern, because it can impair visual acuity despite an otherwise good surgical result. Different suturing techniques have been developed to minimize astigmatism. The purpose of this study was to evaluate an opposing 10-0 nylon double running suture technique for penetrating keratoplasty.

STUDY DESIGN

A retrospective study was undertaken of 91 records of patients who underwent penetrating keratoplasty performed by one surgeon (RNG). This represents 54.8% of 166 consecutive cases. Every eye with an opposing double running suture and a 1- to 3-month postsuture removal followup was selected and evaluated for best corrected visual acuity and astigmatism, excluding eyes that developed graft failure or corneal ulcer or that had lack of adequate followup. The cases were divided into five groups by preoperative diagnosis: pseudophakic bullous keratopathy (n = 43), aphakic bullous keratopathy (n = 5), keratoconus (n = 17), Fuchs dystrophy (n = 12), and miscellaneous (n = 14). The mean standard followup period was 13.7 months after penetrating keratoplasty. Thirty percent of the eyes had an extensive followup, with a mean of 33 months after penetrating keratoplasty.

RESULTS

Eighty-two percent of the patients had a significant improvement of their visual acuity postoperatively, defined by a five-line improvement of best corrected visual acuity or a best corrected visual acuity of 20/40 or better. The mean astigmatic keratometric reading was 3.98 diopters, with a manifest refraction cylinder of 3.42 diopters at the 1- to 3-month postsuture removal visit. This study also shows that there is no statistically significant change in keratometric astigmatism or manifest refraction cylinder from the 1- to 3-month postsuture removal measurements to the more extensive followup of 18 to 66 months after penetrating keratoplasty (p > 0.10).

CONCLUSIONS

This suture technique allows for excellent longterm stability of the wound with visual and astigmatic results that are comparable to those of previous studies. The use of the opposing double running suture is a viable alternative to some of the other widely used techniques and may be considered more stable and secure.

Topographic analysis of corneal regularity after penetrating keratoplasty

PURPOSE

To evaluate the accuracy of the Holladay Diagnostic Summary of the EyeSys Corneal Analysis System in predicting the corneal visual acuity potential in patients who have undergone penetrating keratoplasty (PKP).

METHODS

Astigmatism patterns, refractive and topographic astigmatism, best spectacle-corrected visual acuity (BSCVA), and hard contact lens (HCL) visual acuity of 54 patients were analyzed 3 months after PKP and compared with the Potential Corneal Acuity (PCA) value predicted by the Holladay Diagnostic Summary.

RESULTS

Qualitative patterns of astigmatism (p = 0.01) and refractive (p = 0.002) and topographic (p = 0.0002) astigmatism were significantly correlated with PCA values. Using HCL visual acuities to correct the BSCVA (HCL-corrected BSCVA) for noncorneal causes of reduced vision, we found that the PCA values of 48.1% of the patients were within one line of the HCL-corrected BSCVA; 81.5% were within two lines; and 93.0% were within three lines.

CONCLUSION

The Holladay PCA measurement may be useful in the postoperative evaluation of the optical quality of the central corneal surface in patients who have undergone PKP.

11-0 Mersilene alone as a single running suture in corneal grafts

PURPOSE

To study the safety and long-term stability of 11-0 Mersilene when used alone as a single running suture in corneal grafts.

METHODS

Seventeen eyes on which corneal transplants were performed with 11-0 Mersilene alone as a single running suture between October 1992 and April 1998 were entered into this study. Post-operative data were collected retrospectively on a standardised form. Mean age of patients at the time of surgery was 49.7 years. Pre-operative diagnoses were keratoconus (8 eyes), Fuchs' corneal dystrophy (6 eyes), megalocornea (1 eye), bullous keratopathy (1 eye) and irregular astigmatism following penetrating corneal injury (1 eye). Mean follow-up was 54.1 months, and ranged between 24 and 91 months.

RESULTS

Fourteen eyes (82%) achieved visual acuities of 6/18 or better. Post-keratoplasty astigmatism was < or = 5D in 14 eyes (82%). Sutures were left intact in 9 eyes for a mean period of 51.1 months (24-91 months). Complications included wound leak (3 cases), elevated edge (1 case), high intraocular pressure (1 case), sterile infiltrates (1 case) and early rejection (1 case).

CONCLUSION

11-0 Mersilene alone can be effectively used as a single running suture in corneal grafts. These sutures can safely be left intact for a long period due to Mersilene's non-biodegradable nature.

Evaluation of techniques of single continuous suturing in penetrating keratoplasty

AIM

To evaluate the three techniques of single continuous suturing-namely, torque, antitorque, and no torque in penetrating keratoplasty.

METHODS

53 eyes of 53 patients underwent penetrating keratoplasty using torque (17 patients), antitorque (18 patients), and no torque (18 patients) suturing techniques in this prospective study. Patients were followed up at 4 weeks, 3 months, and 6 months. Keratometric, videokeratographic, refractive astigmatism, and best corrected visual acuity were determined in all the three groups at each follow up visit. Post-keratoplasty suture adjustment was done at 4 weeks, if the astigmatism was >3 dioptres.

RESULTS

The initial astigmatism in the torque group was higher than in the other two groups, although it was not statistically significant. Following suture adjustment, there was a significant decrease in astigmatism in all the three groups (p<0.0001). However, no significant difference in the postoperative astigmatism at 3 months and at 6 months was seen among the three groups.

CONCLUSIONS

The three techniques of single continuous suturing-that is, torque, antitorque, and no torque produce a similar final astigmatic results. Suture adjustment is an effective method of reducing post-penetrating keratoplasty astigmatism.

Combined interrupted and continuous versus single continuous adjustable suturing in penetrating keratoplasty: a prospective, randomized study of induced astigmatism during the first postoperative year

OBJECTIVE

To compare postoperative astigmatism induced by two different suturing techniques in penetrating keratoplasty (PKP).

DESIGN

A monocenter, prospective, randomized clinical trial with a longitudinal 1-year follow-up.

PARTICIPANTS

A total of 95 eyes undergoing PKP were randomized into 2 groups. Of these, 51 eyes were allocated to the combined interrupted and continuous suturing group (ICS) and 44 eyes to the single continuous adjustable suturing (SCAS) group.

INTERVENTION

In the ICS group, suturing was with a combination of 12 interrupted 10-0 nylon and 1 continuous 11-0 nylon sutures. Eyes in the SCAS group had been sutured with a single running 24-bite 10-0 nylon. Selective suture removal started no earlier than 10 weeks after surgery; suture adjustment could start as soon as possible after surgery.

MAIN OUTCOME MEASURES

Astigmatism was measured by topography, keratometry, and refraction at 3-, 6-, 9-, and 12-month postoperative intervals.

RESULTS

The difference in mean time of suture manipulation between groups was significant (P = 0.0001), with the SCAS starting earlier. A significant decrease in astigmatism occurred by either interrupted suture removal (6.69 +/- 3.11 diopter [D] before to 4.76 +/- 2.99 D after, P = 0.0002) or suture adjustment (7.18 +/- 3.12 D before to 4.46 +/- 3.24 D after, P = 0.0001). However, the net astigmatic reduction in the SCAS group was not significantly greater (P = 0.250) than in the ICS group. Vector change was 7.40 +/- 4.17 D and 6.28 +/- 4.14 D for SCAS and ICS, respectively (P = 0.13). At no interval (3, 6, 9, or 12 months) was there significant difference in astigmatism between the two groups. Refractive astigmatism (cyl, D) at 1 year was 2.66 +/- 1.70 for the ICS and 3.12 +/- 2.62 for the SCAS, but there was no significant treatment effect (P = 0.945). Furthermore, 66% of the ICS eyes and 58% of the SCAS eyes (P = 0.295) were within the astigmatic target of the study (<3.5 D).

CONCLUSIONS

Postkeratoplasty astigmatism can be decreased similarly with either adjustment of a single running suture or selective removal of interrupted sutures. No advantage of the SCAS over ICS in terms of fewer manipulations or less astigmatism was seen as suggested previously.

Postoperative suture manipulation for control of corneal graft astigmatism

PURPOSE

To assess the effect on post-keratoplasty astigmatism of postoperative manipulation of a single running suture.

METHODS

All corneal transplant patients in whom a single 10/0 nylon running suture was placed between November 1990 and April 1996 were included in a prospective study of the effect of manipulation of the suture at the earliest possible time after surgery when the keratometry became possible by virtue of the epithelial surface integrity and where this revealed astigmatism of greater than 2 D.

RESULTS

One hundred and ninety eyes underwent suture manipulation and were followed up. Follow up on 30 eyes was discontinued. Repeat manipulation of the running suture was the most common reason for discontinuation of follow up. The remaining patients were followed for a mean (+/- SD) 415.5+/-326.4 days. Mean astigmatism of 7.8+/-3.1 D was reduced to 1.7+/-2.0 D immediately after manipulation, but regressed to 3.0+/-1.9 D (n = 76) by 1 year. The suture was removed in 32 patients. Twenty-five eyes had post-removal astigmatism measurements. In these 25 eyes, astigmatic error appeared not to revert to premanipulation levels. The only significant complication was one broken suture at manipulation.

CONCLUSIONS

Early suture manipulation is effective in reducing suture in post-keratoplasty astigmatism, but some regression is seen.

Different suturing techniques variously affect the regularity of postkeratoplasty astigmatism

OBJECTIVE

This study aimed to determine the effect of various suturing techniques on the regularity of postkeratoplasty astigmatism.

DESIGN

A prospective clinical trial.

PARTICIPANTS

Sixty-two consecutive patients undergoing penetrating keratoplasty by the same surgeon (MB) participated.

INTERVENTION

Each patient was assigned to one of four groups according to the suturing technique used (a = 16 interrupted 10-0 nylon sutures; b = 2 running 10-0 nylon sutures, each with 8 bites; c = 2 running 10-0 nylon sutures, each with 12 bites; d = 2 running 10-0 nylon sutures, each with 16 bites). This was the only parameter permitted to be changed in the standard keratoplasty procedure used for all cases. Corneal topography was performed 1, 3, and 6 months after surgery. The astigmatic patterns seen on the corneal maps then were classified into regular (symmetric or asymmetric bowtie patterns) or irregular (distorted bowtie, multiaxial, or other patterns).

MAIN OUTCOME MEASURES

Regularity of postkeratoplasty corneal astigmatism was measured.

RESULTS

At all postoperative examination times, the percentage of irregular astigmatic patterns was highest in group a and lowest in group d (chi-square test: P < 0.005). Groups b and c showed intermediate values. The entity of the astigmatic error as measured by the simulated K-readings of the topographic maps did not differ significantly in the four groups.

CONCLUSIONS

A suturing technique using 2 running sutures with 16 bites each can minimize irregular postkeratoplasty astigmatism as long as sutures are in place, when compared with interrupted sutures or double-running sutures of less than 16 bites.

Analysis of videokeratography after penetrating keratoplasty: topographic characteristics and effects of removing running sutures

OBJECTIVE

Previous studies have shown that removal of running sutures after penetrating keratoplasty causes unpredictable changes in astigmatism. The current study was conducted to investigate whether computer-assisted videokeratography is beneficial for predicting visual outcomes after running sutures are removed.

DESIGN

The design was that of a prospective clinical study.

PARTICIPANTS

The authors prospectively studied 29 consecutive eyes undergoing a 10-0 nylon running suture removal after penetrating keratoplasty.

INTERVENTIONS

Videokeratography was performed before, 1 week, 1 month, and 3 months after removal of sutures.

MAIN OUTCOME MEASURES

Changes in refractive and topographic astigmatism after suture removal were measured. Topographic patterns and their quantitative descriptors also were analyzed.

RESULTS

An asymmetric bowtie was the most common videokeratography pattern both before and after suture removal. After suture removal, the incidence of peripheral corneal steepening increased significantly (2 vs. 21 eyes, P < 0.0001), and that of focal flattening of the midperipheral cornea decreased (13 vs. 5 eyes, P = 0.046). The mean topographic astigmatism, surface regularity index, and corrected visual acuity were improved significantly by suture removal in eyes that had localized flattening but not in eyes without this finding. Eyes having either skewed axis in astigmatism or topographic astigmatism of more than 9 diopters also showed significant decreases in astigmatism.

CONCLUSIONS

Suture removal after keratoplasty is advantageous for both reducing astigmatism and normalizing topography, especially in eyes that have localized flattening of the midperipheral cornea. Predictability of visual outcomes of a running suture removal in postkeratoplasty eyes may be improved by the use of videokeratography.

Characteristics of normal corneal topography using the EyeSys corneal analysis system

PURPOSE

To study the parameters of corneal topography of normal eyes using the Corneal Analysis System (CAS, EyeSys Technologies) to determine the types and frequency of patterns and parameters.

SETTING

University of Illinois Eye Center, Chicago, Illinois, USA.

METHODS

Three independent, masked judges, using a forced-choice paradigm, classified corneal topography patterns into six categories on one randomly selected, normal eye of 100 persons who did not wear contact lenses. The patterns were defined by using the midpoint dioptric bin and a 0.50 diopter (D) steeper bin.

RESULTS

The pattern frequency using the mid-dioptric bin was teardrop (6%), amorphous (11%), round (11%), symmetric bow tie (17%), asymmetric bow tie (1 %), kidney (22%), and oval (32%). Mean refractive and keratometric cylinders, respectively, were teardrop (0.13 and 0.15 D), amorphous (0.15 and 0.49 D), round (0.18 and 0.56 D), oval (0.21 and 0.56 D), kidney (0.51 and 0.72 D), and bow tie (1.18 and 1.82 D). Pattern frequency using the 0.50 D steeper bin was round (2%), oval (5%), teardrop (6%), kidney (15%), amorphous (17%), asymmetric bow tie (17%), and symmetric bow tie (37%). Mean refractive and keratometric cylinders, respectively, were round (0.13 and 0.32 D), amorphous (0.25 and 0.38 D), kidney (0.11 and 0.42 D), oval (0.40 and 0.59 D), teardrop (0.08 and 0.75 D), and bow tie (0.65 and 1.09 D). Mean flat and steep contours were 41.76 D (95% confidence interval [CI], 38.68 to 44.84 D) and 44.15 D (95% CI, 41.00 to 47.31 D), respectively. Mean contour range was 2.40 D (95% CI, 0.61 to 4.17 D).

CONCLUSION

The data suggest that for 95% of normal corneas, corneal contours will be steeper than 38.50 D, flatter than 47.50 D, and have a contour range less than 4.25 D when using the EyeSys CAS.

Randomized clinical trial of penetrating keratoplasty. Before and after suture removal comparison of intraoperative and postoperative suture adjustment

PURPOSE

The authors performed a prospective, randomized clinical trial of penetrating keratoplasty and compared visual acuity, refraction, and topography up to 15 months postoperatively (3 months after suture removal) after intraoperative and postoperative suture adjustment.

METHODS

Twenty-five patients undergoing penetrating keratoplasty for avascular corneal pathology were randomly assigned to two groups. All surgery was done by one surgeon using the same technique (except for intraoperative suture adjustment) with suction trephination (8 mm) and a running 10-0 nylon suture. Intraoperative suture adjustment was performed in the test group and was not performed in the control group. Postoperative suture adjustment was done during the first postoperative month and up to 4 months postoperatively in all patients who had more than 3.5 diopters (D) of astigmatism. The running suture was removed at approximately 12 months postoperatively. Refraction and computed topographic analysis to compare patients with intraoperative and postoperative suture adjustment were performed at 1, 3, 6, 9, 12 (before suture removal), and 15 (after suture removal) months.

RESULTS

There was less (P = 0.004) topographic astigmatism up to 12 months postoperatively (pre-suture removal) in patients adjusted intraoperatively (mean +/- standard deviation, 1.53 +/- 0.72 D) than in patients adjusted postoperatively (2.83 +/- 1.19 D). After suture removal, at 15 months postoperatively, astigmatism was still less in the intraoperative adjustment group (1.75 +/- 1.04 D) than in the postoperative adjustment group (2.23 +/- 17.2 D), but the authors could not demonstrate statistical significance. After intraoperative adjustment, no significant change in mean astigmatism occurred, and no patient had more than a 1.18-D change in the amount of astigmatism or more than a 22 degrees change in axis (75% < 10 degrees change) after suture removal. Corneas were more regular until suture removal in the group with intraoperative adjustment, but differences decreased after suture removal. Best spectacle-corrected visual acuity was better in the intraoperatively adjusted group until suture removal with no significant changes in best spectacle-corrected visual acuity between 1 and 15 months. Best spectacle-corrected visual acuity improved more slowly after postoperative adjustment and was different at 1 and 15 months (P = 0.0005).

CONCLUSION

The authors demonstrated low astigmatism and good visual results at 15 months postoperatively after either intraoperative or postoperative running suture adjustment, but intraoperative suture adjustment permitted more rapid visual rehabilitation, increased safety, and increased refractive stability.

The effect of artificial tears on computer-assisted corneal topography in normal eyes and after penetrating keratoplasty

PURPOSE

To examine the effect of adding artificial tears for one minute to normal eyes and eyes that have undergone keratoplasty by using computer-assisted videokeratography.

METHODS

We prospectively analyzed 24 normal corneas (24 patients) chosen by random number table (reproducibility section [10 eyes], tear section [14 eyes]) as well as 14 postkeratoplasty corneas. The parametric descriptors analyzed statistically included the simulated keratometry value, surface asymmetry index, surface regularity index, power at the vertex normal, and the pupil offsets from the visual axis. Vectoral analysis was used to calculate the difference in power and axis between the simulated keratometry values before and after tear instillation.

RESULTS

In normal eyes, tear instillation increased the surface asymmetry index (0.28 +/- 0.34, P = .01), changed the simulated keratometry value (0.23 diopter by 27.8 degrees), and power (0.79 +/- 0.82 diopters, P = .004) and location (0.91 +/- 0.76 mm) of the steepest point of the cornea changed. In postkeratoplasty eyes, the surface regularity index decreased (0.49 +/- 0.80, P = .04), surface asymmetry index decreased (0.37 +/- 1.03, P = .21), mean simulated keratometry value changed (1.04 diopters by 1.01 degrees), and power (0.70 +/- 2.34 diopters, P = .28) and location (1.04 +/- 1.17 mm) of the steepest point of the cornea changed. Changes were greater than the variability of the surface regularity index (0.07 +/- 0.05), surface asymmetry index (0.04 +/- 0.03), simulated keratometry value power (0.08 +/- 0.06 diopter), and axis (4.6 +/- 5 degrees).

CONCLUSIONS

The addition of artificial tears to normal or regular and symmetric eyes that have undergone keratoplasty worsened symmetry and changed the power and location of the steepest point. However, the addition of artificial tears to irregular eyes that have undergone penetrating keratoplasty created a more regular and symmetric surface and significantly altered the simulated keratometry values. We recommend that corneal topography be performed before the application of artificial tears.

Randomized clinical trial comparing astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment

PURPOSE

The authors performed a prospective, randomized clinical trial to compare postoperative astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment.

METHODS

Twenty-five patients undergoing penetrating keratoplasty for avascular corneal pathology randomly were assigned to two groups. All surgery was performed by one surgeon (ONS) using the same technique (except for intraoperative suture adjustment) with Hanna trephination (8 mm) and a running 10-0 nylon suture. Postoperative suture adjustment was done during the first postoperative month in all patients who had more than 3.5 diopters of astigmatism. Refraction and computerized topographic analysis were performed at 1 and 6 months postoperatively.

RESULTS

Intraoperative suture adjustment significantly decreased postkeratoplasty topographic (P = 0.0001) and refractive (P = 0.0001) astigmatism and improved best spectacle-corrected visual acuity (P = 0.0019) during the first postoperative month. Seventy-seven percent of control patients (mean topographic astigmatism, 4.89 +/- 1.99 D at 1 month), but no patients who underwent intraoperative suture adjustment (mean topographic astigmatism, 1.50 +/- 0.74 D at 1 month), required at least one postoperative suture adjustment that delayed optical stability and increased postoperative complications. At 6 months postoperatively, mean topographic (P = 0.06) and refractive (P = 0.0001) astigmatism were smaller in the intraoperatively adjusted group than in the control group with postoperative suture adjustments. After intraoperative adjustment, best spectacle-corrected visual acuity was better (P = 0.0168, P = 0.0434) and corneal topography was more regular (P = 0.02, P = 0.07, NS) at 1 and 6 months, respectively, than after postoperative adjustment.

CONCLUSION

Visual rehabilitation with decreased postkeratoplasty astigmatism and more regular corneal topography was attained more rapidly and safely with intraoperative suture adjustment.

Suture adjustment in penetrating keratoplasty

Postoperative adjustment of a single running penetrating corneal graft suture was done in 19 patients (22 adjustments). The short-term effect of this procedure was a mean reduction of corneal astigmatism of 4.39D (p < 0.0001). Thereafter, the corneal contour was fairly stable, provided that the running suture remained intact and tight. Localized loosening of the graft suture significantly increased the corneal astigmatism. Following removal of the graft suture no statistically significant mean change of corneal astigmatism was found. However, patients with a previously intact running suture tended to show increased astigmatism, while those with a previous localized suture loosening usually showed a decreased astigmatism after suture removal. The main benefit of suture adjustment is apparently the rapid and fairly stable reduction of postkeratoplasty astigmatism usually obtained, but unfortunately this effect seems chiefly to exist only as long as the graft suture remains intact and tight.

The management of post-keratoplasty astigmatism by post-operative adjustment of a single continuous suture

Penetrating keratoplasty was performed in 39 consecutive patients. A 16 bite 10-0 nylon continuous suture was used. Post-operatively, the suture was adjusted to reduce astigmatism, as determined by refraction, keratoscopy and keratometry. Suture adjustment was performed if astigmatism was over 4 dioptres (D). The suture was tightened in the flatter meridian and loosened in the steeper meridian. Twenty-one patients had suture adjustment performed. Prior to adjustment, mean (+/- standard deviation) astigmatism measured 6.33 +/- 1.38 D. Following adjustment, mean astigmatism was significantly reduced to 2.69 +/- 1.14 D (p < 0.0001). The average final astigmatism for the entire group was 2.66 +/- 1.12 D. The use of a continuous adjustable suture in penetrating keratoplasty significantly reduced the post-operative astigmatism in a group of patients undergoing penetrating keratoplasty.

An adjustable double running suture technique for keratoplasty

In a retrospective analysis, we examined 30 consecutive cases of penetrating keratoplasty in which a double running 10-0/11-0 nylon suture technique was used and the 10-0 suture was adjusted early in the postoperative period to reduce astigmatism. When the response to suture adjustment was inadequate, the presence of the 11-0 suture allowed for early (ten to 18 weeks) removal of the 10-0 suture. Rapid visual recovery (12.3 +/- 0.95 weeks; mean +/- standard error) and low levels of final astigmatism (2.66 +/- 0.24 diopters) were achieved. Visual acuity was 20/20 to 20/40 in 25 of the 28 patients (89%) who were visually rehabilitated. In these 28 patients, visual acuity remained stable for the remainder of the study. All patients had a minimum of six months' follow-up from the time of surgery; mean follow-up was 10.6 +/- 1.70 months.

Multivariate assessment of computer-analyzed corneal topographers

Methodological aspects of multivariate statistical models to describe and to assess data from computer-analyzed corneal topographers (CACT) are considered. The data generated by repeated curvature mappings of calibrated steel balls are discussed in detail with the objective of formulating the basic questions and suggesting directions to assess data from clinical applications of CACT. The interpretation of seemingly straightforward concepts such as accuracy and precision is revisited with the objective of understanding its meaning in future clinical and experimental applications of CACT. Some of the statistical problems related to the analysis of corneal astigmatism based on CACT data are also discussed.

Postkeratoplasty astigmatism with single running suture or interrupted sutures

In a prospective randomized clinical trial we compared astigmatism after penetrating keratoplasty with two different suture techniques between two groups of patients (38 patients). The first group (18 patients) had a 24-bite single running 10-0 nylon suture (single running suture) with postoperative suture adjustment to decrease astigmatism. The second group (20 patients) had a combination of a 16-bite running 10-0 nylon suture and eight interrupted 10-0 nylon sutures (combined running and interrupted sutures) with selective postoperative removal of interrupted sutures to decrease astigmatism. The single running suture resulted in a lower postoperative astigmatism than a combined running and interrupted suture technique (single running suture, 2.7 +/- 2.2 diopters; combined running and interrupted sutures, 3.9 +/- 2.5 diopters; P < .02). Average length of follow-up was similar in both groups (single running suture, 9.0 +/- 2.2 months and combined running and interrupted sutures, 8.4 +/- 2.2 months). Minimal length of follow-up was six months in both groups. No running sutures were broken. The adjustable single running suture technique provided greater control of astigmatism after penetrating keratoplasty than a technique using a combination of a 16-bite running suture and eight interrupted sutures.

Causes of high astigmatism after penetrating keratoplasty

We retrospectively evaluated the factors which might have caused excessive corneal astigmatism after penetrating keratoplasty (PKP) in 29 eyes, in which surgical correction of astigmatism was indicated. In 18 eyes high astigmatism (5 diopters or more) existed before suture removal probably due to graft elevation (3x), wound dehiscence (3x), wound configuration abnormalities such as ovality/overcut (8x), and a thin recipient cornea (2x). The cause was unknown in 2 eyes. In 19 eyes the astigmatism considerably increased after all sutures were removed; astigmatism increased an average of 8.8 diopters (range, 5 to 16.5 D). Ten of these 19 patients showed graft elevation, despite the fact that the sutures were only removed after an average 22.9 months. In 3 other patients the astigmatism gradually increased over the years, long after suture removal; two of these showed graft elevation. The study demonstrates the possible instability of keratoplasty wounds, the change in astigmatism after suture removal, and the late apparently spontaneous changes in astigmatism after PKP in some eyes.

11-0 mersilene as running suture for penetrating keratoplasty

We evaluated astigmatic results and complications of the combined suturing technique in penetrating keratoplasty by using 11-0 Mersilene as a running suture. Twenty-seven grafts were studied for a follow-up that ranged between ten and 46 months (mean, 27.2 months). During the study, complications included three graft failures, one instance of inadvertent breakage of the running suture, one instance of one suture bite cutting through the recipient cornea, and suture microabscesses in two eyes. Keratometric astigmatism was 2.5 +/- 2.1 diopters at six months, was 2.4 +/- 2.3 diopters at 12 months, and was 2.5 +/- 2.0 diopters at 24 months. Our data indicate that 11-0 Mersilene is suitable for the running suture in corneal transplants in the combined technique. Spontaneous suture dissolution did not occur throughout the follow-up period. The use of a less biodegradable suture enables the maintenance of low levels of astigmatism for longer periods when compared with a previous study that used 11-0 nylon suture.

Running nylon suture dissolution after penetrating keratoplasty

We attempted to evaluate whether the low degrees of astigmatism achieved early in the postkeratoplasty period with the combined interrupted/running suturing technique were maintained for long periods of time. For 13 to 70 months (mean, 30.2 months), we monitored a group of patients (25 eyes) who had previously undergone the combined interrupted/running suturing technique (12 interrupted 10-0 nylon sutures and one running 11-0 nylon suture). Nine running sutures broke spontaneously, causing a significant increase of the keratometric astigmatism of the entire population from 1.7 +/- 1.6 to 3.4 +/- 2.6 diopters (mean +/- standard deviation). The mean vector-corrected change in astigmatism after suture breakage was 4.9 +/- 2.6 diopters. Surgical procedures to reduce astigmatism were required in many of the eyes in which the 11-0 running nylon suture broke. Our results suggested that 11-0 nylon is not an ideal material for the running suture because its high rate of spontaneous disruption leads to undesired, statistically significant increases in postkeratoplasty astigmatism. Further, our results indicated that the selective suture technique can maintain low degrees of astigmatism only if the sutures remain intact. Studies of the effect of keratoplasty suturing techniques on astigmatism should probably include a follow-up that is sufficiently long to indicate its long-term value to the patient.

Mersilene (polyester), a new suture for penetrating keratoplasty

Mersilene (polyester monofilament) seems to be suitable for penetrating keratoplasty because it is strong, shows no degradation by ultraviolet light, is insoluble, so that it can be left in situ, and offers the possibility of regulating postoperative astigmatism by suture adjustment. In 12 patients penetrating keratoplasty was performed with the combined interrupted/running suturing technique, using eight interrupted nylon 10-0 sutures and one running Mersilene 11-0 suture. The results were compared with those of 25 patients in whom eight interrupted nylon 10-0 sutures and one running nylon 11-0 suture were used. Six months after penetrating keratoplasty, no differences could be found between the two groups in keratometric astigmatism, visual acuity or slitlamp findings. In three patients postoperative adjustment of the running Mersilene suture reduced astigmatism by 50, 90 and 100% respectively. In an animal study the behaviour of Mersilene in the cornea was evaluated by slitlamp examination, histology and electron-microscopy. The tissue response to Mersilene was minimal. Considering the resemblance to nylon in clinical findings, minimal tissue response, lack of biodegradation and possibility of regulating postoperative astigmatism by suture adjustment, Mersilene seems to be a suitable material for penetrating keratoplasty.

Corneal topography for selective suture removal after penetrating keratoplasty

Twenty-nine suture removals from 20 eyes (21 patients) on which penetrating keratoplasty had been performed were analyzed in a nonrandomized consecutive study to evaluate the role of computer-assisted corneal topography in selective suture removal to reduce astigmatism. Topographic guidance for suture removal resulted in a net decrease in refractive and keratometric astigmatism in 21 of the 29 cases. The net reduction in astigmatism averaged 1.4, 0.9, and 1.0 diopters when measured by refraction, keratometry, and topography, respectively. The preliminary choice of sutures to be removed on the basis of refraction, keratometry, and inspection was changed in 20 of the 29 cases when information added by the topographic map was considered. Although many variables of suture removal remain unpredictable, computer-assisted corneal topography is a powerful means of describing corneal power after penetrating keratoplasty and is useful as a guide in selective suture removal for reduction of astigmatism.

Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus

Of a series of 201 corneal transplants for keratoconus over a 20-year period, 42 grafts (39 eyes of 38 patients) required further surgery because of intolerable astigmatism (range, -3 diopters [D] to -18 D; mean, 8.9 D). Relaxing incisions, compressive resuturing, and augmented relaxing incisions were the techniques used. All procedures resulted in a similar mean reduction in cylinder -3.6 to 5 D, but the outcome with augmented relaxing incisions was less predictable. Six grafts required two or more procedures for a satisfactory outcome. All patients had corrected visual acuity of 20/30 or better after surgery, and 75% had visual acuity of 20/20 or better. The cumulative time until 90% of the grafts had useful vision was 32 months after refractive surgery. Relaxing incisions offer the prospect of more rapid visual rehabilitation than compressive resuturing.

Advances in the analysis of corneal topography

Recent advances in topographic analysis have provided powerful tools for detecting subtle, but clinically significant, alterations of corneal contour. This article compares keratometry, keratoscopy, and computer-assisted topographic analysis and provides specific examples of the sensitivity of computer-assisted systems in revealing topographic alterations that were not previously discernable. Quantitative descriptors of corneal topography such as the surface asymmetry index, the surface regularity index, and simulated keratometry value augment the information provided by color-coded topographic maps.