Causes of PUK
1. Inflammatory disorders
– Systemic vasculitides
• Rheumatoid arthritis
• Wegener’s granulomatosis
• Polyarteritis nodosa
• Relapsing polychondritis
– Ocular conditions
• Mooren’s Ulcer
• Marginal keratitis
2. Infections
– Viruses
– Bacteria
– Protozoa
– Fungi
3. Ocular surface instability
– Limbal stem cell deficiency
– Previous ocular surface surgery
– Severe chemical injury
– Inflammatory conditions
• Stevens Johnson syndrome
• Ocular cicatricial pemphigoid
4. Ectasia
– Pellucid marginal degeneration
Treatment is individualized and frequently involves co-management with internal physicians. In most instances, medical treatment may suffice to halt disease progression and prevent future ulceration. However, in some patients, surgical intervention is undertaken either as an adjunct to medical therapy, when medical therapy proves inadequate to halt disease progression, or when complications arise with the primary aim of restoring tectonic integrity (Table 6.2). This chapter aims to explore why and when surgery should be considered, and what surgery to perform.
Table 6.2
Complications of PUK
Complications of PUK |
|---|
1. Disease progression—the area of corneal melt can extend circumferentially, centripetally and centrifugally to involve the central cornea, limbus and sclera |
2. Perforation—this serious complication requires urgent therapy to restore integrity of the globe |
3. Secondary infection—during the active phase of PUK, epithelial defects overlying the area of melt predisposes to secondary microbial infections in both infective and non-infective causes of PUK |
4. Ectasia and astigmatism—irregular astigmatism results in a decrease in visual acuity and needs to be addressed together with treatment of the underlying disease |
Previous studies have shown many different surgical approaches to management of PUK, depending on the cause and extent of disease. Penetrating keratoplasty (PK) was preferred to restore tectonic integrity prior to advancements in surgical techniques [1, 2]. However, graft survival was poor, and compared to optical grafts with survival rates of 72.0%, that of tectonic and therapeutic grafts were 41.7 and 58.3%, respectively, at 3 years [3]. Sequential cryopreserved PK followed by optical PK was found to have a 72.9% one-year graft survival [4], compared to 68.3% for tectonic grafts during the same period [3]. In PUK with peripheral melts, larger, decentred, circular grafts were used. As these were peripheral and possibly eccentrically shaped, it increased the chances of vascularisation, peripheral anterior synechiae, and anterior chamber angle and graft failure. In addition, areas of healthy, unaffected cornea were replaced, and these grafts frequently involved the visual axis. In view of these poor rates of graft survival, standard full thickness large keratoplasties should be avoided if other less aggressive or more successful procedures are possible.
Lamellar keratoplasty (LK) is frequently performed for corneal disorders, including surgical treatment of PUK. This can be performed even in infective conditions and was found to have reduced the rates of endothelial failure, graft rejection, graft failure, and secondary endophthalmitis. The 5-year survival rate was shown to be higher at 66.8% versus 56.2% in PK [5–8].
Vanathi et al. described the use of PK, LK and mushroom grafts for a variety of corneal perforations with various aetiologies. Mushroom grafts were performed for perforations with or without iris incarceration with a circumferential flange of corneal thinning at the edges of the perforation [9] with good tectonic outcomes. However, only 70.7% of all patients achieved visual acuity of 6/24 or better for all graft types, for reasons such as cataract formation, graft-host interface issues and astigmatism.
In addition to tectonic support, surgical intervention has a role in optical rehabilitation in PUK. This is sometimes necessary as corneal ectasia may develop post-keratoplasty. Vajpayee et al. described using “Tuck in” LK with successful improvement in visual acuities and significant reduction in astigmatism [10].
Although there exists a variety of surgical grafts, which can be used in PUKs, many involve larger than needed grafts, with “wastage” of healthy adjacent cornea and limbal tissues. We will now discuss our management principles in dealing with PUK, our indications for surgery therapy, and describe our latest surgical technique.
Management, Timing and Indications for Surgery
In patients with PUK, management can be broadly divided into medical, adjunctive therapy and/or surgical interventions. This may occur in the form of keratoplasty with a minimalist approach.
It is prudent to adopt a stepwise approach to escalation of therapy depending on the stage and severity of PUK (Fig. 6.1). Medical therapy is the mainstay of treatment for PUKs to treat the underlying primary condition and in so doing to prevent worsening and even halt the disease process at its early stages. In addition to systemic therapy, topical therapy reduces inflammation, thereby curbing cornea melting, promotes healing of epithelial defects, and prevents or treats any infections. Long-term medical therapy, usually in the form of systemic immunosuppression, is also indicated to maintain a disease-free state, or in cases of recurrent or relapsing disease and in patients who have undergone keratoplasty.
Fig. 6.1
Treatment algorithm for PUK
If disease progression occurs despite full medical therapy, adjunctive procedures can be undertaken. This may help to curb the progression of disease while avoiding the complexities of keratoplasty and its subsequent management.
Examples of adjunctive procedures include corneal gluing [11] (with or without grafts), Amniotic Membrane Transplantation [12, 13] and Conjunctival Resection [14] (in Mooren’s Ulcer). However, although these techniques serve to restore and protect tectonic integrity of the cornea, it is insufficient for improvement of optical function.
Finally, more invasive surgical interventions should be undertaken in disease progression with severe melting which could lead to descemetocele formation or perforation, or if the patient already presents with advanced disease. The indications and surgical principles are listed in Table 6.3.
Table 6.3
Surgical Indications and Principles
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