EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: Here, our aim was to report our treatment strategies and their results performed for visual rehabilitation after penetrating keratoplasty.

Materials and Methods: The medical records of 98 patients (54 male/44 female), with results from 104 eyes, who underwent penetrating keratoplasty between January 2013 and January 2015 at the Baskent University Faculty of Medicine, Department of Ophthalmology were reviewed. Patient age, indication for penetrating keratoplasty, interventions performed for visual rehabilitation, follow-up duration, topographic and refractive astigmatism at the end of follow-up, and final best corrected visual acuity results were recorded.

Results: Mean age of patients was 54 ± 23 years. Indications for penetrating keratoplasty included keratoconus, Fuchs endothelial dystrophy, pseudophakic bullous keratopathy, and corneal scarring. The mean duration of follow-up was 23 ± 11.5 months. Topography-guided suture adjustment and selective suture removal were performed 2 to 6 weeks and after 3 months in eyes with more than 3 diopters of corneal astigmatism in patients who had continuous and interrupted sutures. Spectacle correction was administered for 86 eyes (83%), and contact lenses including rigid gas-permeable and scleral lenses were fitted in 18 eyes (17%) in patients who were unsatisfied with spectacle correction. Relaxing corneal incisions were performed in 23 eyes (22%), and toric intraocular lens implantations were performed in 34 eyes (33%) with cataracts. The mean topographic and absolute refractive astigmatism at the end of follow-up was 3.4 ± 2.6 and 3.6 ± 1.9 diopters.

Conclusions: Topography-guided suture adjustment and selective suture removal are effective for minimizing early postoperative astigmatism. If significant astigmatism remains after suture removal, which cannot be corrected by optical means, then further surgical procedures including relaxing incisions and toric intraocular lens implantation can be performed.

Key words : Astigmatism, Penetrating keratoplasty, Visual rehabilitation

Keratoplasty is a surgical procedure in which a damaged or diseased cornea is replaced entirely (penetrating keratoplasty) or partially (lamellar keratoplasty) by a donated corneal graft. Keratoplasty comprises 3 basic types: (1) penetrating keratoplasty (PK), in which the entire cornea from epithelium to endothelium is replaced; (2) deep anterior lamellar keratoplasty, in which the recipient’s endothelium and Descemet membrane, at times with deep stroma, are preserved and the remainder of the cornea is replaced; and (3) endothelial transplant, in which the recipient’s Descemet membrane and endothelium, at times with deep stroma, are replaced with corresponding tissue from a donor, such as Descemet-stripping endothelial keratoplasty and Descemet membrane endothelial keratoplasty.¹

Although the maintenance of a clear cornea is important, success is measured by the functional vision attained by the grafted eye. Astigmatism is the most common cause of suboptimal vision after corneal transplant, despite a clear corneal graft.² High-grade refractive errors and anisometropia are other common causes. On the basis of several studies, 15% to 31% of patients undergoing penetrating keratoplasty may develop postoperative astigmatism greater than 5 diopters (D).^3,4 The astigmatism can be irregular with associated higher-order aberrations that can ultimately limit the vision obtained and may not be corrected satisfactorily by spectacles or contact lenses.⁵

Commonly practiced techniques for visual rehabilitation after penetrating keratoplasty consist of postoperative suture manipulation, including running suture tension adjustment and selective interrupted suture removal, optical correction consisting of spectacles and contact lenses, corneal relaxing incisions, compression sutures, laser refractive surgery, insertion of intrastromal corneal ring segments, wedge resection, toric phakic intraocular lens implantation, and finally regrafting.⁶

In this study, our aim was to report our treatment strategies and their results for visual rehabilitation and management of astigmatism after PK.

Materials and Methods

We reviewed the records of 104 eyes of 98 patients (54 male and 44 female) who underwent PK between January 2013 and January 2015 at the Baskent University Faculty of Medicine, Department of Ophthalmology. The study protocol was approved by the ethics committee of the institution and adhered to the ethical guidelines of the 1975 Helsinki Declaration. Written informed consent was obtained from all patients.

All surgeries were performed by a single experienced surgeon (DDA). The donor tissue was prepared with the endothelial side up and used a Barron corneal punch (7.75-8.25 mm). The recipient cornea was trephined to a depth of approximately 0.4 mm with a Barron vacuum trephine with disposable blade (7.5-8 mm), and recipient corneal removal was completed with scissors. All donor corneal tissue was 0.25 mm larger than the recipient trephination, except for patients with primary keratoconus, in which case same-size donor-host trephination was performed. The donor cornea was sutured to the host cornea with 12 interrupted 10-0 nylon sutures. The first 4 interrupted sutures were placed such that an equal-sided “square” was barely visible on the donor tissue, each suture bite was about the same tightness, and interrupted sutures were placed, at about three-quarters depth, two-fifths within the donor and three-fifths within the recipient. A 12-bite 10-0 nylon continuous suture was then placed in 36 eyes (35%) somewhat more tightly than the interrupted sutures after adjustment of the intraocular pressure to approximately normal tension.

The age, indication for PK, postoperative interventions performed for visual rehabilitation, follow-up duration, the topographic and refractive astigmatism at the end of follow-up, and the final best corrected visual acuity were recorded.

The mean age of the patients was 54 ± 23 years. Indications for PK included keratoconus, Fuchs endothelial dystrophy, pseudophakic bullous keratopathy, and corneal scarring (Figure 1).

The mean follow-up duration was 23 ± 11.5 months. Patients were examined on postoperative day 1, week 1, and monthly thereafter. Complete ophthalmologic examination and corneal tomography by Scheimpflug imaging (WaveLight Allegro Oculyzer; WaveLight AG, Erlangen, Germany) were performed at each visit. Corneal topography-guided suture adjustment and selective suture removal were performed 2 to 6 weeks and after 3 months in eyes with more than 3 D of corneal astigmatism in patients who had continuous and interrupted sutures. After initial suture removal, nonadjacent sutures were removed at an interval of 4 to 6 weeks, as deemed necessary. Only a single suture was removed at a time. The loose and tight sutures were identified by refraction, biomicroscopic examination, and evaluation of corneal topography.

Spectacle correction was performed in 86 eyes (83%), and contact lenses, including rigid gas-permeable and scleral lenses, were fitted in 18 eyes (17%) of patients who were unsatisfied with spectacle correction, mostly due to higher order aberrations or high anisometropia.

Relaxing corneal incisions were performed in 23 eyes (22%). Patients with keratometric astigmatism > 4.0 D after complete suture removal were considered for this procedure. Under topical anesthesia and direct visual inspection, relaxing incisions were made down to Descemet membrane usually on both sides of the steepest meridian with an arc length of 45 degrees to 90 degrees. The site and extension of relaxing incisions were determined on the basis of corneal topography. The site of relaxing incision was the donor cornea.

Toric intraocular lens implantation was performed in 34 eyes (33%) with cataracts. Mean absolute refractive astigmatism decreased from 4.24 ± 2.12 to 2.35 ± 1.56 D on the postoperative first month in these patients. Figure 2 shows images of a keratoconus patient with PK before and after cataract extraction and implantation of a toric intraocular lens with removal of all sutures.

At the end of follow-up, mean topographic astigmatism was 3.4 ± 2.6 D and absolute refractive astigmatism was 3.6 ± 1.9 D. Fifty percent of the patients had a final best corrected visual acuity higher than 7/10.

Postkeratoplasty astigmatism remains a challenge for corneorefractive surgeons. Although maintenance of a healthy graft is the most crucial issue in keratoplasty procedures, astigmatism is a limiting factor in visual rehabilitation of otherwise successful corneal grafts. The treatment of astigmatism after keratoplasty includes 2 stages: when sutures are still present at the graft-host junction and when all sutures have been removed.⁶ Presence of excessive sutures in postkeratoplasty astigmatism is usually approached by selective suture manipulation, ie, suture adjustment and/or suture removal along the steep meridian of astigmatism.⁷ A small amount of postkeratoplasty 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.⁸

Laser lamellar refractive surgery can also be used to treat postkeratoplasty astigmatism, and toric phakic intraocular lenses have recently been recommended.⁹

Intraoperative and postoperative suture manipulations have been described for minimizing early postoperative astigmatism.^10,11 After PK, sutures should be kept for at least 1 year unless complications such as cheese-wiring, loosening, and vascularization develop. During this period, astigmatism > 4 D can be reduced by suture manipulation consisting of selective interrupted suture removal and tension adjustment of running sutures.⁷ Use of interrupted or combined running and interrupted sutures allows for the selective removal of interrupted ones, with the goal of reducing astigmatism.¹⁰ Successful visual rehabilitation therefore depends partially on accurate identification of the tight-interrupted sutures. Computerized corneal topography has the advantage of mapping subtle corneal power changes accurately over the entire optical zone and beyond, allowing identification of steep meridians that can be attributed to specific sutures.¹¹ In the interrupted suturing technique, selective suture removal can start as early as 2 months after PK, provided that the neighboring sutures are not to be removed at least 6 months postoperatively. That is because removal of adjacent sutures within this period is more likely to make the wound unstable than removal of alternate or nonadjacent sutures. After initial suture removal, nonadjacent sutures can be removed at an interval of 4 to 6 weeks, as deemed necessary.^12,13 We performed corneal topography-guided suture adjustment and selective suture removal 2 to 6 weeks and after 3 months in eyes with more than 3 D of corneal astigmatism in patients who had continuous and interrupted sutures.

Spectacle lenses and contact lenses can play an important role in the correction of astigmatism at all time points after corneal graft procedures. They are equally applicable to the care of suture-in and suture-out postkeratoplasty astigmatism. Although 3 D or less of astigmatism after corneal surgery can be addressed by spectacle lenses, irregular astigmatism or significant anisometropia limits their use after keratoplasty. The use of glasses may not be possible when a significant amount of astigmatic anisometropia is present. Rigid gas-permeable contact lenses, which may be effective in 80% of cases, often provide superior visual acuity and are frequently required in eyes with moderate to severe astigmatism.¹⁴ Rigid contact lenses can provide better quality of vision, especially in patients with irregular astigmatism. Often patient choice determines the use of spectacles or contact lenses. Contact lenses are safe to use in the presence of sutures, which should not be a contraindication for prescribing them. The diameter of the graft, the topographical relationship between the host cornea and donor cornea, the graft toricity, and the location of the graft are essential parameters in contact lens fitting.¹⁵ Various types of contact lenses have been used to manage postkeratoplasty astigmatism including hybrid, scleral, rigid gas-permeable, and piggyback contact lenses.¹⁶ Spectacle correction was performed in 86 eyes (83%), and contact lenses including rigid gas-permeable and scleral lenses were fitted in 18 eyes (17%) of patients who were unsatisfied with spectacle correction, mostly because of higher order aberrations or high anisometropia in our study population.

If significant astigmatism remains after suture removal, which cannot be corrected by optical means such as spectacle correction or contact lenses, surgical procedures containing relaxing incisions, compression sutures, laser refractive surgery, insertion of intrastromal corneal ring segments, wedge resection, and toric intraocular lens implantation can be performed.⁶

Astigmatic keratotomy is an established method for management of postkeratoplasty astigmatism that cannot be corrected by spectacle lenses or hard contact lenses.¹⁷ Various astigmatic keratotomy techniques have been reported, but transverse incisions and arcuate incisions are the most popular.¹⁸ Incisions can be placed in the donor graft button, in the host cornea, or in the graft-host junction.¹⁹ The number of incisions, incision length and depth, and patient factors contribute to the outcome of astigmatic keratotomy.¹⁴ Astigmatic keratotomy spares the visual axis and provides rapid visual rehabilitation. However, poor predictability, corneal perforation, and wound dehiscence are major concerns.8 In our patients, arcuate incisions were placed central to the graft-host junction at the 7.0-mm optical zone for maximal effect.

Toric intraocular lens (IOL) implantation can also be performed to correct postkeratoplasty astigmatism. These provide a wide range for correction of spherocylindrical errors and require less manipulation of the grafted tissue. This modality may be a good choice when keratorefractive procedures are contraindicated in postkeratoplasty patients with cataracts. Frohn and associates were the first to describe toric IOL implantation in a patient with cataracts for correction of high postkeratoplasty astigmatism.²⁰ Later, Alfonso and associates²¹ reported that toric posterior chamber phakic IOLs are a viable treatment option for myopia and astigmatism after keratoplasty. Furthermore, Tahzib and associates²² noted that the implantation of toric iris-clip IOL after keratoplasty effectively reduces astigmatism and ametropia in phakic and pseu-dophakic eyes. Viestenz and associates23 reported that the refractive cylinder could be reduced from 7.0 ± 2.6 D to 1.63 ± 1.5 D after surgery. They recommended, however, that regular and symmetric corneal topography is essential for successful implantation of toric IOLs. In our study, toric IOL implantation was performed in 34 eyes (33%) with cataracts. Mean absolute refractive astigmatism decreased from 4.24 ± 2.12 to 2.35 ± 1.56 D on the postoperative first month in these patients.

As a result, it is important to individualize and modify the treatment of astigmatism after PK based on corneal topography and patient expectations for the initial and subsequent visual rehabilitation.

Volume: 14 Issue: 3 November 2016 - Supplement - 3

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