Contact Lenses After Keratoplasty
CONTACT LENSES AFTER KERATOPLASTY
Contact Lenses After Keratoplasty
What to expect and what to look for with contact lens management in post-keratoplasty corneas.
By Korine van Dijk, BSc; Lamis Baydoun, MD; Ricarda M. Konder; & Gerrit R.J. Melles, MD, PhD
For more than 100 years, full-thickness corneal transplantation has been the only treatment option available to restore vision in various (end-stage) corneal diseases. Within the last decade, however, corneal transplantation has developed rapidly from full-thickness penetrating keratoplasty (PK) to the more selective forms of anterior and posterior lamellar keratoplasties, such as deep anterior lamellar keratoplasty (DALK), Descemet’s stripping automated endothelial keratoplasty (DSAEK), and Descemet’s membrane endothelial keratoplasty (DMEK).
In these procedures, only the diseased layers of the cornea are replaced, while the healthy layers are retained (Figure 1). Following the transition to the different lamellar keratoplasty procedures and their continuous refinements, visual outcomes have improved considerably, and the incidence of complications has dropped significantly (Table 1) (Melles et al, 1999; Reinhart et al, 2011; Melles, 2006; Tan et al, 2012; and others. Full list available at www.clspectrum.com/references.).
Figure 1. Schematic overview displaying (A) a virgin cornea and (B–E) different keratoplasty procedures: (B) PK, (C) DALK, (D) DSAEK, and (E) DMEK.
TABLE 1 Advantages and disadvantages of the different keratoplasty techniques
|Open sky procedure
|Wound- / suture-related problems
|Risk of allograft rejection
|PK = Penetrating Keratoplasty
DALK = Deep anterior lamellar keratoplasty
DSAEK = Descemet’s stripping automated endothelial keratoplasty
DMEK = Descemet’s membrane endothelial keratoplasty
ECD = Endothelial cell density
However, the treatment of such corneas often does not end with corneal transplantation. A crucial issue with corneal transplantation is the aftercare, which aims at improving vision through additives (i.e., spectacles or contact lenses) as well as maintaining a healthy, clear, and long-surviving graft (Tan et al, 2012; Williams et al, 1995; Jonas et al, 2002; Claesson et al, 2002). Both visual rehabilitation and graft survival are potentially influenced by several factors (Williams et al, 1995; Jonas et al, 2002; Claesson et al, 2002).
Conversely, contact lens wear may induce factors that directly influence graft survival. It is essential for eyecare practitioners to know these factors to be able to improve postoperative care and to avoid and anticipate complications. Although contact lens fitting and management can be challenging, it has proven to be effective and safe after PK (Szczotka et al, 2003; Wietharn et al, 2004). With the different lamellar keratoplasty techniques, contact lens fitting must be reviewed according to necessity, timing, and characteristics, because each technique calls for a different approach.
Visual Rehabilitation After Keratoplasty
Penetrating Keratoplasty In cases in which corneal disease affects corneal clarity, PK has been an acceptable keratoplasty technique for visual restoration for more than a century. PK, however, is a rather indiscriminate form of surgery because it replaces all corneal layers with no regard for the healthy ones (Tan et al, 2012). Furthermore, PK is often accompanied by complications derived from corneal sutures, ocular surface problems, and/or wound dehiscence owing to incomplete wound healing.
As a result, PK is frequently characterized by slow, insufficient, and unsatisfactory visual rehabilitation, which is even further complicated by refractive problems such as anisometropia and high (irregular) astigmatism (Tan et al, 2012; Williams et al, 1995; Claesson et al, 2002). Thus, contact lens fitting after PK has become an indispensable part of postoperative visual rehabilitation, which can be challenging due to the complex corneal topography and physiology of a PK-eye.
Deep Anterior Lamellar Keratoplasty For treating corneal diseases not involving the corneal endothelium, such as keratoconus and stromal scars or dystrophies, DALK allows replacement of diseased recipient stroma with donor corneal stroma, while the recipient corneal endothelium and Descemet’s membrane (DM) are retained (Figure 1). This better preserves the ocular integrity, permitting earlier suture removal and faster visual rehabilitation due to faster wound recovery and, consequently, fewer wound healing-related problems (Melles et al, 1999; Reinhart et al, 2011; Tan et al, 2012). Similar to PK, however, the anterior transplant in DALK also requires fixation by sutures. In addition, despite good graft clarity after successful DALK, visual rehabilitation may be equally compromised due to unpredictable refractive outcomes with irregular astigmatism and anisometropia (Reinhart et al, 2011). Hence, also after DALK, contact lens fitting plays an important role in improving postoperative visual performance.
Endothelial Keratoplasty: DSAEK and DMEK Endothelial keratoplasty (EK) has practically replaced PK as the preferred method for treating endothelial disorders such as Fuchs’ endothelial dystrophy and bullous keratopathy (Melles, 2006; Tan et al, 2012; Dapena et al, 2009; Bahar et al, 2008). In modern EK techniques, the diseased DM—with its endothelium—is stripped from the recipient posterior stroma. After that, the donor tissue is transferred into the anterior chamber where it is unfolded and then attached to the recipient stroma through the use of an air bubble, without suturing. Consequently, the anterior corneal surface is no longer compromised by corneal surface incisions and/or sutures; this preserves structural integrity, reduces wound healing problems, and eliminates suture-derived complications (Melles, 2006; Tan et al, 2012; Dapena et al, 2009; Bahar et al, 2008). Major refractive changes are also avoided, allowing for a faster and more complete visual rehabilitation that can usually be obtained with spectacle correction only (Dapena et al, 2009; Price and Price, 2010; van Dijk, Ham et al, 2013).
Currently, the most widely used technique is DSAEK, in which the donor tissue consists not only of DM and endothelium, but also of an additional (thin) layer of posterior stroma (Figure 1) (Melles, 2006; Price and Price, 2010; Price et al, 2011; Guerra et al, 2011). Even though visual recovery after DSAEK is superior to that after PK, the DSAEK-graft’s layer of attached stroma can undermine the optical performance, so fewer cases than expected achieve a visual acuity (VA) ≥20/25 after DSAEK (Dapena et al, 2009; Price and Price, 2010; Guerra et al, 2011).
In contrast, with DMEK (the latest refinement of endothelial keratoplasty), only an isolated DM with its endothelium is transplanted, resulting in near normal anatomical corneal restoration with approximately 80% of eyes reaching ≥20/25 VA within six months after surgery (Figures 1 and 2) (Dapena et al, 2009; Price and Price, 2010; van Dijk, Ham et al, 2013; Guerra et al, 2011). Although the anterior cornea does not appear to be compromised in either DSAEK or DMEK, the final visual outcome may sometimes be limited by anterior corneal irregularities often revealed with corneal topography examinations only (Figure 3) (Dapena et al, 2013; van Dijk, Ham et al, 2013).
Figure 2. Slit lamp photograph of an eye at three months after DMEK for Fuchs’ endothelial dystrophy. Note the near anatomical restoration of the transplanted cornea (A) as well as its clarity after DMEK (B).
Figure 3. Slit lamp images (A and C) and Scheimpflug topography images (B and D) of two cases, six months after DMEK. Slit lamp image A shows a clear cornea; however, associated topography (B) reveals irregular astigmatism. Note the presence of anterior stromal scarring in slit lamp image C (arrows), visible as a “whitish” stromal opacity in the center of the cornea. Consequently, corneal topography (D) shows an area of corneal flattening and the presence of anterior corneal surface irregularities. In both cases, best spectacle corrected visual acuity could be improved up to 20/23 with GP contact lenses.
The source of these surface irregularities after EK may be changes in the anterior stroma, such as collagen disorganization and subepithelial fibrosis, occurring in more advanced stages of endothelial disease (van Dijk, Parker et al, 2013). Especially in cases of prolonged preoperative corneal edema, these abnormalities manifest after EK and may then affect visual outcomes (van Dijk, Parker et al, 2013). A typical reduction of best spectacle-corrected VA to around 20/30 (0.6) and complaints of monocular diplopia and/or ghost images, which can be improved with contact lenses, are often encountered in such cases (Dapena et al, 2013). Furthermore, in even more advanced stages of endothelial disease, (mild) subepithelial stromal scarring—already visible with slit lamp examination—may cause similar symptoms and hinder sufficient refractive correction by spectacles only (Figure 3) (van Dijk, Parker et al, 2013).
Therefore, although good visual rehabilitation can mostly be obtained with spectacles after EK, patients who have long-standing corneal edema and visible anterior corneal scarring should be counseled about possible postoperative contact lens requirements before scheduling for EK. Moreover, the presence, extent, and duration of corneal edema due to endothelial dysfunction should be considered as a parameter in the surgical planning (van Dijk, Parker et al, 2013).
Factors Affecting Graft Survival
For the long-term success of corneal transplantation, longevity and survival of the transplanted graft is mandatory to sustain vision. Long-term graft survival after PK ranges from around 50% to 80% at 10 years, with significant variation depending on indication and complications (Felipe et al, 2013; Niziol et al, 2013; Ing et al, 1998). The likelihood of having a healthy and functional graft in the long term for uncomplicated keratoconus and corneal dystrophy is quite good (Felipe et al, 2013; Niziol et al, 2013). In contrast, eyes transplanted for pseudophakic or aphakic bullous keratopathy, eyes after glaucoma surgery, or infectious corneal ulcers might have a lower graft survival rate (Williams et al, 1995). Complications such as continuous and increased endothelial cell decline, and allograft rejection, which can both be provoked by additional complications (e.g., sutures, corneal vascularization, glaucoma), can cause graft failure (Williams et al, 1995; Felipe et al, 2013; Niziol et al, 2013; Ing et al, 1998).
In a healthy cornea, the endothelial cell density (ECD) normally decreases by 0.6% per year in adulthood; whereas eyes may lose endothelial cells at a yearly rate of 2.5% for up to 10 years after cataract surgery (Bourne, Nelson et al, 1994). ECD decrease in the first year after PK reaches approximately 45% and continues at a higher rate than normal for many years (Ing et al, 1998; Bourne, Hodge et al, 1994; Cornea Donor Study Investigator Group, 2008). Corneal clarity can usually be preserved as long as the ECD remains above a certain threshold (approximately 400 cells/mm2). When the ECD falls below this threshold, the remaining cellular pump capacity may not be sufficient to keep the cornea clear (Edelhauser, 2006), resulting in graft failure. The exact cause is unknown, but suspected triggers include surgical trauma, long-term postoperative ocular stress, and the above-mentioned complications.
With DALK, the maintained recipient endothelium results in much lower rates of ECD, suggesting an “unlimited” lifetime for a DALK graft (Borderie et al, 2012). After EK, the initial ECD drop of around 35% in the first six months after surgery appears higher than after PK. However, the ongoing decrease with a lower stable rate of 7% yearly after the first year seems lower compared to PK (Price et al, 2011; Price et al, 2013; Baydoun et al, 2012). Therefore, higher long-term survival rates may be assumed after EK. This probably also results from the fewer complications occurring in EK, among which allograft rejection plays a key role.
Allograft rejection is the other leading risk factor for graft failure, which stems from a host immunologic response against foreign antigens from donor tissue (Panda et al, 2007). The most serious form affects the endothelial layer and may present with photophobia, ocular pain, redness, a significant anterior chamber reaction with keratic precipitates, and/or a Khodadoust line. If endothelial function is also disrupted, corneal edema may occur, and vision often declines significantly (Panda et al, 2007). Events such as corneal neovascularization, prior graft failure in a previous graft, history of herpetic keratitis, (pre-existing) glaucoma or postoperative increase of intraocular pressure (IOP), inflammation, and infection all contribute to an increased risk of allograft rejection episodes (Panda et al, 2007), which can lead to an increased ECD decline and, thus, eventually to graft failure.
With PK, when transplanting a full-thickness corneal graft, rejection of every layer (epithelium, stroma, and endothelium) may occur (Panda et al, 2007). The preservation of the healthy recipient endothelium in DALK is a major advantage because endothelial allograft rejection is practically eliminated (Borderie et al, 2011). This contributes to higher graft survival rates compared to PK, although suture-related neovascularization and inflammation remain risk factors. With posterior endothelial grafts, lack of sutures eliminates suture-induced inflammation and neovascularization as well as an associated immune response. This also is reflected in the lower incidence and risk of allograft rejection reported after DSAEK and, in particular, after DMEK, which could result from the reduced antigen load that is lowest in DMEK (Figure 1) (Dapena et al, 2011; Anshu et al, 2012).
Topical corticosteroids, routinely prescribed for both prevention and treatment of allograft rejection, may significantly reduce the risk (Panda et al, 2007). Concerns about IOP elevation and wound healing problems after PK, however, may tend to shift the balance in favor of earlier steroid tapering and cessation, rather than long-term topical corticosteroid use. Steroids may be tapered more quickly after DALK and the different EK techniques given the lower risk for allograft rejection, which will reduce the risk for secondary glaucoma development. Furthermore, wound healing problems may be of much less concern after lamellar keratoplasty.
Contact Lenses After Keratoplasty
Several contact lens types and designs, including GP, scleral, and soft (silicone hydrogel) contact lenses, have been proposed for correcting astigmatism and anisometropia after corneal transplantation (Szczotka et al, 2003; Wietharn et al, 2004; Visser et al, 2013). The choice of lens type may be based on the refractive and lubrication status of the eye, the complexity of the corneal topography, and specific visual needs.
Another factor to consider with post-keratoplasty contact lens management would be the altered physiology of a transplanted eye, especially with respect to graft survival. Although contact lenses have proven to be safe, they may be associated with adverse reactions in the presence of a corneal transplant.
Part of the decision-making process for fitting contact lenses after keratoplasty is not just deciding whether fitting is needed, but also when to fit. After PK, complete healing of the corneal donor button into the recipient “bed” can take as long as 24 months after surgery, and such corneas may never regain their preoperative strength. Therefore, because of possible spontaneous wound rupture, suture removal may often be postponed as long as there is no corneal neovascularization or suture loosening (Elder et al, 2004).
To facilitate visual recovery in the case of necessary early visual rehabilitation, contact lenses may be placed over corneal sutures provided that the postoperative course has been uncomplicated and the cornea shows good clearing. The sutures must be well epithelialized and the wound margin stable, which normally takes at least six to 12 months following PK. (Partial) suture removal will likely induce a change in corneal refractive power, and a new contact lens fitting must be considered. Given the increased risk of infection involved with wearing contact lenses, topical steroids should be tapered and/or a topical antibiotic added before fitting.
After fitting, regular follow-up visits are necessary to watch for complications such as corneal chafing, suture loosening or breakage, neovascularization, and keratitis—because all of these may contribute to an immunologic stimulus leading to allograft rejection. In the longer term, the success rate of contact lens wear may also depend on the viability of the endothelium. In transplanted corneas with lower ECD counts, trauma and/or hypoxia induced by wearing a contact lens may induce corneal edema and contact lens intolerance (Setälä et al, 1998).
Due to the preservation of the host endothelium and the subsequent minimal endothelial cell decrease after DALK, the long-term viability of the endothelium—in combination with wearing contact lenses—may be less of a concern. Another advantage of preserving the host endothelial cells is better maintenance of the ocular integrity, resulting in faster and better wound recovery with consequently earlier suture removal. Additionally, preserving the host endothelium makes the risk of allograft rejection extremely low, enabling earlier topical steroid tapering (Reinhart et al, 2011). Both advantages will contribute to earlier contact lens fitting and a faster visual rehabilitation.
Because EK (except for minor corneal entries) requires no large corneal surface incisions and/or sutures, all structural integrity, wound healing, and suture-derived complications are eliminated. Consequently, refractive stability and good spectacle-corrected visual rehabilitation can mostly be obtained within three to six months following the surgery (van Dijk, Ham et al, 2013). In cases of anterior corneal irregularities originating from prolonged preoperative edema, contact lenses may aid in improving vision (Figure 3) (van Dijk, Parker et al, 2013). Because these irregularities are relatively mild, the initial contact lens choice and fit may be comparable to a virgin corneal contact lens fit. Nevertheless, although especially after DMEK, the cornea may resemble a virgin cornea (Figure 2), there may still be physiological differences compared to a normal cornea, especially in term of long-term endothelial viability.
In conclusion, minimizing mechanical and hypoxic stress to the cornea that can result in a cascade of secondary complications and possible graft failure may be very important in post-keratoplasty contact lens management. Given the lower incidence of complications and faster visual rehabilitation after the different forms of lamellar keratoplasty, contact lens management may also become less demanding for patients who undergo these procedures. CLS
For references, please visit www.clspectrum.com/references and click on document #225.
Korine van Dijk is an optometrist and researcher at the Netherlands Institute for Innovative Ocular Surgery (NIIOS) and Melles Cornea Clinic. Her research focus is on visual rehabilitation after lamellar keratoplasty.
Dr. Baydoun is a Consultant Ophthalmologist, cornea surgeon, and researcher at the NIIOS and Melles Cornea Clinic. Her research focus is on Descemet’s membrane endothelial keratoplasty (DMEK).
Ricarda Konder is pursuing a bachelor of science in Medicinal Chemistry at the University of New Brunswick and is currently completing a fellowship at the NIIOS.
Dr. Melles is an ophthalmologist and the director of the NIIOS and Melles Cornea Clinic. He specializes in corneal transplantation and has developed various advanced lamellar keratoplasty techniques. He is a consultant for D.O.R.C. International/Dutch Ophthalmic USA.
Contact Lens Spectrum, Volume: 29 , Issue: August 2014, page(s): 36-38, 40, 42