Laterality

Bilateral causes of LSCD include congenital diseases, such as aniridia, and autoimmune or inflammatory diseases, such as Stevens–Johnson syndrome (SJS), ocular cicatricial pemphigoid (OCP), and atopic keratoconjunctivitis. Most acquired causes of LSCD may be unilateral or bilateral, including chemical or thermal injuries, contact lens-induced keratitis (CLIK), and iatrogenic causes, such as ocular surgery and toxic medications.

Performing either ocular stem cell transplantation (OSST) or keratoprosthesis (KPro) surgery commits the patient to long-term regular follow-up visits, and potential complications. Patients with unilateral disease who are functioning well with good vision in the fellow eye may choose not to undergo surgery. Other patients with unilateral disease may undergo surgery to restore binocular vision or to treat a chronically painful or cosmetically unacceptable diseased eye. In true unilateral disease the treatment of choice is a conjunctival limbal autograft (CLAU) from the fellow healthy eye. The fellow eye should be examined carefully for any signs of ocular surface disease, and in cases of asymmetric bilateral disease, such as CLIK or chemical injury, the fellow eye should not be used as donor tissue for CLAU.

If the diseased eye is the patient’s only eye, the surgeon should consider a stem cell transplant rather than a KPro. In OSST, complications result in loss of the surface only, and there is less potential for sight-threatening complications, compared with KPro surgery.

Extent of Limbal Stem Cell Deficiency

Limbal stem cell deficiency (LSCD) may be partial or total. In congenital aniridia or in diseases with ongoing chronic inflammation, partial LSCD can progress over time to total LSCD. As seen in Figure 38.1, a patient with a severe alkaline chemical injury progresses over time from active conjunctival inflammation to partial LSCD and then total LSCD. If the visual axis remains unaffected in partial LSCD, the patient may not require transplantation and may be treated medically and monitored for progression. In quiet eyes, with small areas of conjunctival invasion, patients may benefit from sequential conjunctival epitheliectomy in the hope that the residual normal stem cells may repopulate the ocular surface. If several clock hours or more of LSCD exists, then a sectoral OSST may be used to treat that area of LSCD. In total LSCD, the only treatment options are complete OSST for restoration of the ocular surface with or without optical keratoplasty, or a KPro for visual rehabilitation.

Extent of Conjunctival Involvement

The ocular surface diseases most difficult to treat are those that have both limbal stem cell and conjunctival involvement, such as in SJS and OCP. The conjunctiva itself is necessary for a healthy ocular surface, since it provides the mucin for a stable tear film and contains the lymphoid tissue to fight infection. Moreover, its structure of redundant folds allows for free movement of the eye within the orbit. Conjunctival disease may cause mucin–tear deficiency, subepithelial fibrosis, foreshortening of conjunctival fornices, symblepharon, ankyloblepharon, and in the most severe cases, keratinization of the ocular surface.

Activity of Inflammation

In patients with conjunctival involvement, a distinction must be made between previously inflamed conjunctiva and current active inflammation. The conjunctival inflammation from chemical/thermal injuries tends to subside slowly over a period of several months from the initial insult. In comparison, in autoimmune diseases, such as SJS or OCP, there tends to be a chronic background level of inflammation and associated exacerbations of conjunctival inflammation when the disease in active. When the conjunctiva is actively inflamed, there is an increase in immune mediators at the ocular surface. If surgery is performed during active inflammation, there is an increased risk of delayed epithelial healing, corneal melt, and immune rejection postoperatively.

It is important to manage the inflammation preoperatively and wait until the eye is quiet before performing the OSST or KPro. For chemical/thermal injuries, the authors recommend waiting at least 1 year after the initial insult. For autoimmune diseases, the underlying systemic disease should be optimally controlled and the ocular inflammation minimized with topical and often systemic anti-inflammatory agents before proceeding with surgery.

Schwartz et al.¹ proposed a classification system of ocular surface disease based on the extent of stem cell deficiency (stage I or II) and the presence or absence of conjunctival inflammation (stage a, b, or c) (Table 38.1

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