Introduction:
Toxic epidermal necrolysis (TEN) and Steven-Johnson syndrome (SJS) are rare and potentially fatal hypersensitivity mucocutaneous diseases. Infections and medications primarily cause it. The mucous membranes of the oral, respiratory, gastrointestinal, gynecological, and integument tissues are mostly affected regions. The ocular presentation of SJS or TEN can vary based on the acute, subacute, or chronic clinical stage. The acute stage usually occurs within two weeks after the emergence of symptoms. Bilateral conjunctivitis is the most prevalent ocular disease seen at this stage, affecting 15 to 75% of individuals, and 25% of hospitalized patients experience corneal or conjunctival ulcers.
The bulbar conjunctiva and tarsal examinations require cautious lid eversion and fluorescein staining. Local and systemic therapy may not be enough to prevent major ocular consequences leading to blindness. There is no proven effective systemic or local therapy for SJS or TEN. Early identification and proper therapy are essential for the eye's long-term health. The differences between SJS and TEN are determined by the degree of epidermal detachment- 10 % or less of the total body surface area is involved in SJS, 30 % or more in TEN, and 10% to 30 % is involved in SJS or TEN overlap. SJS and TEN have respective incidences of 9.2 and 1.9 per million person-years.
How Is Ocular Surface Reconstruction Done in Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis?
The aim of SJS or TEN treatment is to heal systemic illness and prevent cicatrical ocular consequences. The three categories for the degree of ocular involvement are mild, moderate, and severe. Chronic ocular illness following the acute episodes were categorized as,
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Mild-to-moderate SJS.
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Severe SJS.
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Ocular surface failure.
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Recurring episodic inflammation,
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Progressive conjunctival cicatrisation resembling mucous membrane pemphigoid.
Treatment benefits from systemic immunomodulatory therapy for long-term ocular problems and visual prognosis in SJS or TEN have not yet been established. Ophthalmic treatment is determined by the severity of the condition, and topical eye drops cannot replace surgical treatment. Topical corticosteroids, topical broad-spectrum antibiotics, and a preservative-free lubricant are recommended for severe conjunctivitis with meibominitis (Chronic inflammation of small oil glands in the upper and lower eyelids) in acute SJS or TEN patients. Treatment with topical steroids at an early stage is essential for improving the visual prognosis.
Acute Stage:
The entire ocular surface should be covered by amniotic membrane transplantation (AMT) using a conformer, ProKera, or, symblepharon ring during the acute stage of SJS or TEN. The ocular surface, palpebral conjunctiva, and lid margins were covered with cryopreserved amniotic membrane, which was secured in place with conformer, perilimbal sutures, and reinforced fornix sutures. The purpose of AMT is to promote epithelial healing and decrease inflammation and scarring on the ocular surface. It usually takes place in the acute stage within the first two weeks after ocular involvement.
Subacute or Chronic Stage:
The surface of the eyes may become compromised in a subacute or chronic stage. An anomaly in the tear film components and significant ocular surface scarring lead to severe dry eye. This further leads to the combination of limbal stem cell shortage, recurring or permanent corneal epithelial abnormalities, and symblepharon development. The posterior lid margin keratinization causes the cornea to be microtraumatized with each blink. This results in corneal injury, vascularization, and inflammation. Chronic conjunctival cicatrization deforms the lid margins, causing trichiasis (misdirected eyelashes on the ocular surface), distichiasis (eyelashes grow from the orifices of the meibomian gland), and entropion (the eyelid margin turns inward). This makes the corneal injury worse. A study states that corneal problems were significantly influenced by the degree of tarsal and eyelid disease.
The primary objectives of treatment for SJS or TEN in its chronic stage include visual rehabilitation, management of SJS or TEN sequelae, and prevention of ongoing ocular surface damage. Individuals with ocular manifestations of SJS or TEN can benefit greatly from large-diameter scleral contact lenses. However, lens fitting might provide challenges in eyes with symblepharon. Its high cost prevents its utilization, and following SJS, patient compliance might not be as good. Chronic dry eyes are particularly susceptible to consequences from long-term usage of bandage contact lenses and scleral lenses. Mucous membrane grafting (MMG) is a successful method for decreasing the keratinization of the eyelid margin and palpebral conjunctiva.
End Stage:
Patients with end-stage illness have corneal blindness and severe dry eye. Penetrating keratoplasty is generally not recommended in cases of severe dry eye with SJS or TEN. This is because PK does not supply corneal epithelial stem cells to the limbal region of the eye. The best options for stimulating epithelial regeneration are cultivated oral mucosal epithelial transplantation (COMET) and limb stem cell transplantation (LSCT). Patients with SJS or TEN typically present with severe preoperative conditions (for example, persistent ocular surface inflammation, abnormal ocular surface epithelial differentiation, severe dry eye, and abnormalities related to the lids) and have lower graft survival rates when compared to other thermal corneal damage and LSCD (limb stem cell deficiency) of chemical burn.
How Does Immunosuppressive Therapy Help in SJS or TEN?
Immunosuppressive therapy is necessary for patients with allogeneic limb stem cell transplantation. This is due to the alteration of immunological defenses and the disruption of beneficial bacteria on the ocular surface. This can further lead to immunological rejection, persistent ocular surface inflammation, or postoperative bacterial infections. These patients have a poor prognosis for the long term. Severe ocular surface abnormalities, such as SJS, have been treated with autologous COMET at eye clinics all over the world. According to a recent report, 68% of the eyes with bilateral limb stem cell transplantation showed visual improvement, and 72% of the eyes were classed as having received successful therapy. Patients who have COMET do not require immunosuppression.
Conclusion:
Loss of the ocular surface epithelium and bilateral conjunctivitis are possible symptoms of the acute stage. The chronic stage is characterized by persistent ocular surface inflammation, a chronically dry surface, and cicatrical consequences. Although the use of immunosuppressive and immunomodulatory medications is under discussion, the effectiveness of amniotic membrane transplantation in the acute stage is well documented and should be executed as soon as possible. Prevention is preferable to treatment in terms of symblepharon, malposition of the eyelids, corneal disease, and dry eye.
