Leprosy: Ocular Involvement in Hansen’s Disease

Leprosy (Hansen’s disease), caused by Mycobacterium leprae, remains an underappreciated cause of ocular morbidity in endemic regions. This is despite the sharp global decline in overall case numbers since multidrug therapy became widely available.

Ocular involvement is common in longstanding, poorly treated disease.

It is a major contributor to disability in leprosy survivors, independent of the more visible skin and nerve findings. The organism has a predilection for cooler body surfaces.

This is why the anterior segment of the eye — cornea, iris, and periocular skin — bears the brunt of ocular disease.

The warmer posterior segment is relatively spared. Nerve involvement compounds the problem. This is because facial and trigeminal nerve damage strips the eye of its protective blink reflex. It also removes corneal sensation, at the same time.

Mechanisms of Ocular Damage

Direct bacillary invasion of ocular tissue produces lepromatous keratitis and iridocyclitis in multibacillary disease.

Meanwhile, nerve damage from the immune response to the organism causes a separate, indirect set of problems.

Facial nerve (cranial nerve VII) involvement produces lagophthalmos, and trigeminal (cranial nerve V) involvement produces corneal anesthesia.

The combination is what makes leprosy-related corneal disease so severe. This is because neither protective mechanism (blink or pain) is available to warn the patient or protect the ocular surface.

Chronic low-grade inflammation from bacillary antigens can also produce a slowly progressive keratitis, independent of any acute reactional episode. This contributes to corneal opacification over years, even in patients adherent to treatment.

Ocular and Periocular Findings

• Madarosis — loss of eyebrows and eyelashes, often an early and visible sign
• Lagophthalmos from facial nerve involvement
• Corneal hypoesthesia or anesthesia from trigeminal nerve involvement
• Punctate and diffuse superficial keratitis, sometimes progressing to corneal opacification
• Iris pearls — small, glistening nodules on the iris surface, relatively specific to lepromatous disease
• Chronic iridocyclitis, which can be low-grade and easily overlooked without a slit-lamp exam
• Cataract, often secondary to chronic uveitis

Because corneal sensation is frequently reduced, patients often do not report the pain that would normally prompt an eye exam.

This is a major reason ocular disease in leprosy tends to be diagnosed late.

Lepra Reactions and the Eye

Type 1 (reversal) and type 2 (erythema nodosum leprosum) reactions are immune-mediated episodes.

They can flare during or after treatment and often worsen ocular inflammation acutely. A patient with known leprosy who develops a sudden red, painful eye during a systemic reaction needs prompt ophthalmic assessment.

This is because acute iridocyclitis during a reactional episode can progress quickly if undertreated. Systemic corticosteroids used to manage severe reactions also have a role in controlling the associated ocular inflammation.

However, the underlying antimicrobial treatment needs to continue in parallel.

Differential Diagnosis

• Herpes zoster ophthalmicus — vesicular rash, dermatomal distribution, acute onset
• Sarcoidosis — granulomatous uveitis, but without the peripheral neuropathy or skin lesions of leprosy
• Neurotrophic keratopathy from other causes (herpetic disease, diabetic neuropathy, prior surgery)
• Facial nerve palsy from other causes (Bell’s palsy, tumor, trauma) when madarosis and skin lesions are absent

A careful skin and peripheral nerve exam usually separates leprosy from these alternatives.

Thickened peripheral nerves and hypopigmented, anesthetic skin patches are clues that point specifically toward Hansen’s disease.

Management

Multidrug antimicrobial therapy is the WHO-recommended combination of rifampicin, dapsone, and clofazimine for multibacillary disease.

It treats the underlying infection but does not reverse established nerve damage or corneal scarring. Ocular protection needs to run in parallel with systemic treatment.

This includes aggressive lubrication for exposure and corneal anesthesia, plus taping or a moisture chamber at night for lagophthalmos. Prompt treatment of any secondary microbial keratitis is essential.

An anesthetic, exposed cornea can easily become infected without the patient noticing. Surgical options include lid-loading procedures for lagophthalmos, tarsorrhaphy for severe exposure, and cataract extraction once inflammation is controlled.

These are used selectively once the systemic disease is under control. Regular ophthalmic screening is recommended for all patients with multibacillary leprosy.

This is because ocular disease can progress silently given the sensory loss that so often accompanies it.

Public Health Significance

Leprosy-related blindness is largely preventable with early systemic treatment and routine ocular screening.

However, access to eye care in many endemic areas remains limited. This is relative to the dermatologic and neurologic aspects of the disease, which receive more attention. Integrating eye exams into standard leprosy care pathways is a cost-effective way to reduce disability.

References

• World Health Organization. Guidelines for the Diagnosis, Treatment and Prevention of Leprosy.
• Courtright P, Lewallen S. Ocular manifestations of leprosy. Community Eye Health Journal.
• Daniel E, Ffytche TJ, Kempen JH, et al. Incidence of ocular complications in patients with multibacillary leprosy. British Journal of Ophthalmology.
• Malik AN, Morris RJ, Ffytche TJ. The prevalence of ocular complications in leprosy patients. Eye.
• American Academy of Ophthalmology. Basic and Clinical Science Course, Section 8: External Disease and Cornea.