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Role of Iris Changes As a Cause of Blindness in Lepromatous Leprosy

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Role of Iris Changes As a Cause of Blindness in Lepromatous Leprosy British Journal of Ophthalmology, 1981, 65, 231-'39 Role of iris changes as a cause of blindness in lepromatous leprosy T. J. FFYTCHE From St Thomas's Hospital, Lambeth Palace Road, London SE] 7EH SUMMARY Clinical and pathological investigations in a group of 113 patients with leprosy of long duration demonstrated the importance of iris changes as a cause of blindness. In lepromatous leprosy the so called 'chronic iritis' produces iris atrophy with small nonreacting pupils which exaggerate the visual impairment created by developing lens changes and corneal opacities. The cause of this 'chronic iritis' is believed to be neuroparalytic from early involvement of the small nerves of the iris, particularly the autonomic supply. Clinical and pharmacological evidence for this theory is supported by the histological changes observed in 18 specimens of iris removed during the course of cataract surgery, with progressive atrophy of the iris preferentially affecting the dilator muscle and leading to a nonreacting miosed pupil. Further pharmacological and histo- logical studies are to be undertaken on lepromatous patients with iris involvement with a view to establishing possible methods of prevention. It has for long been realised that the main causes of HYPERSENSITIVITY REACTIONS blindness in leprosy lie in disease of the anterior In all forms of leprosy, but particularly when a segment and that the condition rarely affects the change in polarity occurs, a hypersensitivity reaction tissues at the posterior pole of the eye. Ocular can take place. This 'lepra' reaction usually arises damage in leprosy occurs in 4 ways: (1) facial and when therapy is being commenced or withdrawn, trigeminal nerve involvement; (2) hypersensitivity but can also develop spontaneously.4-6 The reaction reactions; (3) direct bacterial invasion; (4) secon- is generalised, with acute swelling of skin lesions, dary infection. tender nerves, and at times severe fever, and these signs have given rise to the alternative name of FACIAL AND TRIGEMINAL INVOLVEMENT erythema nodosa leprosum. There is often an Leprosy is essentially a neural disease with infection associated acute iritis and at times a nephritis.7 The and eventual destruction of superficial nerves by clinical manifestations are believed now to be Mycobacteria leprae. The anatomical position of the caused by circulating immune complexes becoming facial nerve, especially the zygomatic branch, and deposited in the affected tissues6 8 rather than a the superficial branches of the trigeminal nerve make response to bacteria, for although M. keprae have these structures vulnerable to infection in all forms been found in the anterior chamber by paracen- of leprosy, giving rise to abnormalities of lid position tesis9-12 it is not known what role they play in the and abolition of the normal blink and corneal pathogenesis of the acute uveitis, and the lepra reflexes. A combination of these 2 nerve palsies may reaction can occur in the absence of organisms.8 occur early in the course of the disease and lead to The eye develops an acute iritis which is usually exposure keratitis, with its consequent corneal bilateral and does not differ in its clinical manifesta- damage and opacification. The incidence of these tions from other forms of acute nonleprous iritis. major corneal problems is, however, less than might The disease has a sudden painful onset, and, if be expected, since preservation of the normal Bell's untreated, the eye can be permanently damaged phenomenon prolongs the protection of the cor- within 24-72 hours.13 Aqueous flare and cells, nea.12 Even so, facial palsy has been considered to be keratic precipitates, hypopyon, and synechiae with the second commonest cause of blindness in leprosy.3 seclusio pupillae and secondary glaucoma can occur Correspondence to T. J. ffytche. with secondary cataract and eventual phthisis. 231 232 T. J. ffytche DIRECT BACTERIAL INVASION thelium.31 Eventually iris atrophy develops, with Direct bacterial invasion occurs only in lepro- loss of iris stroma and epithelium, miosis, and the matous leprosy. It is now considered by most formation of holes in the stroma resembling at authors to take place as a result of a bacteraemia times the appearance in essential iris atrophy. following infection,7 812 1416 although some spread Synechiae may be present and were originally noted may occur from infected lacrimal and nasal pass- by Hansen and Bull32 when they described 'iritis ages,6 7 17 but this method of spread may be rare.13 without violent symptoms with exudation around The invasion of the cornea by leprosy bacilli the borders of the pupils and adhesions of the lens gives rise to a true leprous keratitis affecting corneal in patients who have not complained of pain or nerves and later the superficial stroma. This con- derangement of sight.' This tendency to form dition of superficial stromal keratitis is regarded as synechiae is not, however, common to all cases pathognomonic for lepromatous leprosy.18 It has with chronic iritis.3334 Pupil reactions have been been alternatively called 'superficial avascular noted to be sluggish and resistant to conventional keratitis',19 'avascular subepithelial punctate mydriatics early in the disease,24 202333 3 and a keratitis',20 'diffuse punctate lepromatous keratitis', premature presbyopia, even in apparently normal and 'diffuse superficial punctate keratitis'.4 The patients with lepromatous leprosy, was noted by condition is, however, rarely serious for vision Wood.24 Equally asymptomatic is the development unless corneal deposits are substantial and is often of 'iris pearls' in the early stages of the disease. asymptomatic.1921 It may progress to form a cir- These small glistening white lesions are pathogno- cumferential pannus or an interstitial keratitis monic for lepromatous leprosy and have been which does not produce the same degree of vas- shown histologically to be composed of collections cularisation as syphilis2 19 and which rarely causes of tightly packed living and dead bacilli lying severe visual loss.22 A sclerosing form of keratitis may within mononuclear cells (also called 'foam' or follow as a late change.13 'lepra' cells), with little accompanying inflammation Occasionally a leproma may occur in the centre or foreign body reaction.33 36 Iris pearls usually of the cornea with substantial visual loss. This rare develop within a year or two of the commencement lesion is known in some parts of the world as of the iritis and occur mainly at the pupil margin Ruato's corneal leproma. It seems to be regional, around the collarette, described as resembling a occurring in South America23 and Japan,18 and it necklace33 or the beads of a rosary.37 may be provoked by local climatic conditions. The Pearls may develop deep in the iris stroma and corneal leproma is responsible for only a very small occasionally at the periphery. Their natural history proportion of blindness in leprosy. is one of slow increase in size and aggregation. They Other forms of corneal disease and opacification may become pedunculated and eventually drop off occur as a result of exposure and neuroparalytic into the anterior chamber, where they are well keratopathy and include band-shaped degeneration tolerated and produce no inflammatory reaction. and various chronic degenerative conditions. Direct They are a transient phenomenon and are rarely invasion of the episclera occurs as an early event in responsible for any visual impairment. lepromatous leprosy and gives rise to small nodules Bacterial invasion of the iris may also give rise to at the limbus.4 They are often a prelude to leprous the formation of a nodular leproma-sometimes keratitis, and occasionally they may grow across the called 'voluminous leproma of the iris'.25 These are corneal margin as large lepromatous nodules, which rare single polymorphic masses which may occasion- interfere with vision. ally sufficiently disrupt the iris architecture to interfere with vision. Iris Direct bacterial invasion of the iris and ciliary body Lens produces the so-called 'chronic iritis,' which is Direct invasion of the lens by bacilli has never been considered by many to be the commonest cause of demonstrated and many authors consider that there visual impairment in leprosy4152024-28 and termed is no true leprosy cataract and that the lens changes by Weekeroon as the 'cause par excellence of are those seen in a normal aging population.4 7253839 blindness.' The condition which is also known as A secondary cataract may certainly develop after 'insidious anterior uveitis'29 and 'chronic plastic the acute iritis associated with hypersensitivity, but iritis'20 30 commences quietly several years after some authors acknowledge a higher incidence of infection. It is characterised by a lack of symptoms secondary cataract following chronic iritis.214 20 A and overt signs, though slit-lamp examination may possible cause for cataract in lepromatous leprosy show aqueous flare and cells with fine keratic was suggested by Prabhakaran,40 who noted that the precipitates scattered all over the corneal endo- leprosy bacilli reacted with dopa, which is normally Role of iris changes as a cause ofblindness in lepromatous leprosy 233 found in the iris and ciliary body, and that this and 1 was classed as borderline. In all patients the reaction is produced with high local concentrations leprosy had been inactive for at least 3 years and in of quinones, which are known to be cataractogenic. most cases for 10 years or more. SECONDARY INFECTION Case reports Loss of corneal sensitivity, poor nutritional control, and exposure and diminished tear production all CASE 9 combine to make the cornea susceptible to secondary A 60-year-old female with lepromatous leprosy for bacterial, viral, and fungal infections. The additional 22 years. Negative for at least 12 years. destruction of the nose and nasolacrimal passages in Right eye. Hand movements. Corneal scarring, advanced cases increases the local reservoir of posterior synechiae, cataract.
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