Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

Out of these Kala-azar is most commonly seen in endemic areas, can be life threatening. This is caused by L. donovani. Incubation period is long that may range between two to six months following residence in endemic area. The symptoms are long-lasting-fever with enormous enlargement of spleen with moderate enlargement of liver.

It is more common in HIV infected persons. It is common in first decade of life. The organism can be transmitted by way of blood transfusion.

Ocular manifestations are rare in Kala-azar. The children may have retinal haemorrhage, sub conjunctival haemorrhages. The adults can develop retinal vein thrombosis.

Dermal leishmaniasis is associated with ulcers on the lid, episcleral nodules near the limbus causing vascularisation of cornea. There may be iritis.

Trypansomiasis (Sleeping sickness)51

This disease is confined to certain parts of Africa and South America. In Africa, it is caused by trypansoma gambiense transmitted by bite of tsetse fly, and in South American, it is caused by trypansoma cruzi transmitted by bite of a bug of genera triatoma.

Systemic manifestation of African trypansomiasis - Following bite by the fly the organism spreads via blood and lymphatics to lymphatic glands, CSF and brain.

After few weeks the patient develops a skin nodule called trypansome chancre. This is followed by fever that may last for weeks. The organism reaches lymph glands and spleen resulting into their enlargement. The episode of fever has an intermitted pattern. After years the patient reaches a stage of sleeping sickness. The patient develops shuffling gate and finds difficulty to walk. The face becomes mask like with drooping swollen lids. The patient goes to sleep even during working hours. In late stages, there are convulsions, paralysis and coma that terminates in death.

Ocular manifestations

Unilateral allergic edema of the lids, enlargement of pre auricular and sub mandibular glands, bilateral interstitial keratitis and iridocylitis. In terminal months there may be paralysis of extra ocular muscles and papilledema. The condition is often associated with onchocerciasis.

South American trypansomiasis is spread by bite of a bug and not fly, is called Chaga’s disease. It does not cause somnolence. The cutaneous lesion is called Chagoma, which is a localised area of edema with enlargement of draining lymph node. It is associated with fever that lasts for months. There is hepatospleenomegaly. There may be involvement of heart. Death occurs due to meningo encephalitis.

Ocular manifestation is unilateral Chagoma of the lid, which is known as Romana’s

sign.

Taenia echinococcous (Hydatidcyst)52, 53

Taenia echinococcus is smallest of all tape-worms that infest humans. It has world wide distribution. There are three types of echinococi that are pathogenic. Each type has specific geographical distribution. Their life cycle is almost identical with slight dissimilar clinical presentation. The various types are echinococcous granulosus, E multi locularis, E oligoarthus

and E vogeli. Out of this granulosus causes ocular disease. The cyst of E granulosus is unilocular while that of rest are multi locular. Occasionally multi locular cysts can be seen in the orbit.

The dog is the definitive host while many mammals including humans are intermediate hosts. Humans can be primary or intermediate host when they directly ingest food contaminated by dog faeces or secondary intermediate host when they eat contaminated meat which is either uncooked or under cooked of primary intermediate host like sheep, goat, cow etc.

Children are infected by swallowing the eggs. Embryos escape from the eggs, penetrate the intestinal mucosa and reach the portal circulation from there they may travel to any distant part and develop the cyst. Common sites where the cysts are deposited are liver, lung, and orbit. Other organs are spleen, kidney and brain.

The cyst is generally single, grow very slowly without any discomfort. It becomes symptomatic only when it is large enough to press over the adjacent structures or when it rupture and cause anaphylaxis.

A typical echinococcous cyst has two layers—An outer pseudo membrane and an inner germinal layer. The outer layer is surrounded by granulomatous reaction. From the germinal layer develop daughter and grand daughter cysts. The cyst of echinococcus is called hydatid cyst. The cyst is filled with clear fluid. Accidental ruptures of cyst gives rise to severe allergic reaction that may be anaphylactic.

Ocular manifestation

Only 1% of cases of echinococcosis may involve the eyes and its adnexa. Commonest site being the orbit. Next in frequency is sub retinal space from where it may come to vitreous. Rarely it can come into the anterior chamber. Orbital involvement is common in older children and young adults. It is unilateral, generally the cyst is intraconal causing slow, painless, progressive axial proptosis.

The diagnosis is by exclusion and with high index of suspicion. Commonly used investigations are X Ray orbit that may show enlargement of the orbit. A small cyst may not produce any change on X ray. Ultrasonography shows cystic growth without internal reflectivity. CT and MRI give more definite picture.

Sub retinal and intra vitrial cysts are best seen by indirect ophthalmoscope and confirmed by CT.

Cysticercosis54, 55

Cysticercosis is a common parasitic infection all over the world in all ages. The infection is caused by a cestode, taenia solium which is a pork tape worm. Humans are definitive host while pork is an intermediate host and harbouring larval form. Sometimes humans can become intermediate host by ingesting ova of the cestode.

The definitive hosts pass the gravid proglotidis of the adults worm in stool, which is ingested by intermediate host the hog or sometimes dogs and other mammals. In the intestine of the intermediate host the embryos are released which pass the intestinal mucosa and reach the systemic circulation and can be deposited in any organ of the body. Commonest tissues to be infected are the striate muscles. The embryos get entangled in small vessels and are converted into larval stage called cysticircus.

Humans get infected by two ways:

1.By eating under cooked pork that is infested by live cysticircus.

2.By eating food contaminated with ova thus becoming an intermediate host. The ovum ultimately is converted to cysticircus.

Systemic involvement consists of cysticircosis of brain called neuro cysticercosis, muscles, skin and eyes. Less commonly involved are kidney, liver and spleen.

Intestinal cysticercosis is most of the time asymptomatic but may cause vague pain in abdomen, diarrhoea, weight loss. Patient may notice segments of tapeworm in stool.

Neuro cysticercosis is most important and dangerous part of the disease. The clinical manifestation depends on size, location and inflammatory reaction caused by the cyst, which includes - Focal seizures and neurological deficits, generalised convulsion, meningitis, headache, vomiting, and raised intracranial tension. Extra ocular muscle palsy and papilledema are some other features. The presence of intracranial lesion is confirmed by CT and MRI.

Ocular manifestation

Ocular involvements are common. Almost half of the patients with systemic cysticercosis have ocular involvement. All most all parts of the eye, its adnexa and orbit except the lens may be involved.

Involvement of left eye in more frequent than right eye54,55. The cyst may develop in the orbit and migrate anteriorly along the recti muscles and present as sub conjunctival cyst. There may be more than one cyst in the conjunctiva, occasionally the cyst may extrude automatically, may cause proptosis, sub retinal cysts may pass into vitreous, small uveal cysts may pass in AC, involvement of optic nerve is possible. Other ocular involvement is severe intra ocular inflamation following death of the organism inside the eye during anti helmenthic chemotherapy or rupture of the cyst during surgical treatment.

Toxocariasis47, 56, 57

Infection by nematode toxocara is called toxocariasis. It is a zoonotic disease that spreads from dog to the children. Now it is established that toxocariasis, of cats do not infect children. Puppies are more infective than adult dogs.58 Children are more prone to develop toxocariasis than adults. The age ranges between two years to fifteen years mean being seven years. Due some ill understood cause the disease is more common in boys. Ocular lesions are more common on the left side. It is more common in children who eat dirt habitually.

The puppies get infected via transplacental route, during suckling or direct ingesting food infected by eggs. Children get infected by swallowing soil contaminated by eggs. In children the ingested eggs hatch to form larva that penetrate the gut wall to reach systemic circulation, that carries them to distant organs like liver lung, brain and eyes. The passage of the organism from gut to other organs is called visceral larval migrans, in contrast to cutaneous larval migrans that is caused by hookworm of dogs. Besides visceral larval migrans the parasite can cause abdominal pain, anaemia and eosinophilia that may be as high as 90%.

The ocular toxocariasis is less common manifestation than systemic.

Ocular manifestation consist of—Posterior pole granuloma, that when large gives a white reflex in pupillary area and mistaken as retinoblastoma, peripheral granuloma, parsplanitis, diffuse chorioretinitis, exudative retinal detachment and chronic endophthalmitis.

Onchocerciasis59, 60

The disease onchocerciasis is a major cause of preventable and treatable infectious cause of blindness in Africa and South America. The disease is caused by nematode onchocerca volvulus and onchocerea caecutiens. The former is found in central Africa while the latter is found in South America. As the maximum number of cases are found near the rivers, the condition is called river blindness. One of the main complications of the disease is blindness hence the worm is also called blinding worm. Man is the definitive host in whom the micro filaria develops while female black fly-simulium is the intermediate host. It is only the female fly that is responsible for spread of the disease.

The adult larva develops in the mouth part of the fly. The disease spreads to infected host to non infected host, multiple infections are known.

The systemic involvement is mostly cutaneous, less common is involvement of the lymph nodes. Other systems are not known to be involved.

The cutaneous involvement begins with intensive itching along with papular rash. Long term infection leads to hypo-pigmentation of the skin, wrinkled and loose skin. Sometimes there may be hyper pigmentation. Onchocercomata is a subcutaneous nodule, which may be palpable, and visible. In African countries they are seen over the scalp. Mild to moderate lympadenopathy is common generally in the inguinal and femoral area. Hydocele is common. The enlarged nodes may be large enough to hang down.

Ocular involvement

Almost all parts of the eyes except the lens is known to be infected by onchocerciasis. It includes:

1.Edema of lids that is transient. Some times mild proptosis is seen.

2.Conjunctiva becomes thickened and pigmented though free micro filarae are not seen on the conjunctiva, they are demonstrable in fresh biopsy even without staining.

Involvement of the cornea is most important aspect of onchocerciasis and the main cause of blindness. It is present in all most all cases and both the cornae are symmetrically involved.

The corneal involvements are:

Nummular opacity, presence of dead micro filaria, frosted glass appearance of cornea, superficial vascularisation, deposition of calcium, folds in the Descemet’s membrane. There may be punctate keratitis or sclerosing keratitis, KPs. Anterior chamber may show number of free floating micro filaria, which do not elicit any reaction. The dead organisms are accumulated at the bottom of AC.

Uvea may show iritis, distorted pupil, inverted pear pupil, spongy iris called pumic stone iris. Iridocylitis and chorioretinitis is common.

Optic neuritis and atrophy are also seen though the lens is not invaded by microfilaria. Complicated cataract is secondary to uveitis.

Microfilaria may be seen floating in the vitreous.

Thelaziasis60, 61

Thelazia is a small nematode, life cycle of which is not well understood as most of the cases have been reported from South East Asia and far east, it is also called oriental worm. It commonly lives in the lacrimal glands and lacrimal passages of many mammals, common being dogs, and horses. There are two species of thelazia i.e. thelazia calipaeda and thelazia californiensis. Cockroaches are suspected to be intermediate host. It is presumed that the disease is spread by common house fly.

Systemic infection has not been reported.

It is presumed that the flies deposit the eggs of the nematode in the conjunctiva. The source of these eggs is not well understood. The larvae hatch from the eggs and migrate to the lids and lacrimal sac. The larvae may produce conjunctival nodule. The larvae may penetrate the cornea or the sclera to become intra ocular, causing uveitis. The dead worm like most of the nematodes can cause allergic reaction. The worm may be seen as free floating organism in the AC.

Loasis47

The disease loasis is caused by nematode Loa-Loa or African eye worm, Central and western African countries form the endemic area. The microfilaria may live for many years in the subcutaneous tissue of an asymptomatic person who have lived in the endemic area. The life cycle is not well understood. The disease is spread from host to host by bite of the mangrove fly of species chrysops. It is the female fly that bites and spreads the disease. The microfilaria are diurnal, they are seen in the peripheral blood between 12.00 noon and 2.00 noon. The exact incubation period in not known. The disease may be seen concurrently with onchocersiasis. The disease is caused by adult worm that creeps under the skin and produce localised nodule called Calabar swelling.

Systemic involvement is rare but may cause nephropathy, encephalopathy and cardiomyopathy. Eosinophilia is constant and the count may go as high as 50-60%.

The ocular lesions consist of Calabar swelling of the lids. The adultworm may be seen under the conjunctiva.

Trichinosis

Trichinosis is a disease caused by larva of nematode trichinella spriralis and trichnatis pseudo spiralis. Besides these two, there are many more types of trichinal nematode that are found in many mammals. The parasite is found all over the world but the disease is mostly confined to Western Hemisphere.

The disease is spread by eating under cooked food, infected pork or beef. The larva has predilection for striated muscles. The systemic involvement consists of diarrhoea, abdominal pain, nausea, vomiting. The cutaneous involvement includes migration of larva, allergic reaction, maculo papular rash.

Myocarditis and tachyarrthymias, and encephalopathy are rare. Muscle involvement is common.

Ocular involvements are edema of peri orbital tissue, orbicularis and extra ocular muscles palsy, sub conjunctival haemorrhages, retinal haemorrhages.

Dracanculosis

Dracanculosis is caused by dracanculus medinensis which is the largest thread worm. The worm is found mostly in tropical countries. A crustacean - cyclope is the intermediate host. The cyclope is found in water. Humans acquire the disease by drinking water contaminated by cyclope. The cyclope contains the larvae of the parasite. The larvae penetrate the wall of the stomach and intestine and mature. The male dies, the female lives for years and migrate under the skin mostly the lower extremities or any part that is frequently soaked in water like back and head of water carriers. The gravid larva migrates under the skin, which is habitually wet and form a blister. The blister ruptures, releasing large number of larvae in stagnant water and ingested by cyclope and the cycle goes on.

There are no systemic involvement.

The ocular involvement consists of local edema, pain and blister in the lid that may rupture and release larvae. An orbital larva may cause mild proptosis. The worm may form a blister on the skin surface to release the larvae. Sometimes the organism may die in the orbit and get calcified even without any symptom.

Ocular myiasis61

Ocular myiasis is caused due to deposition of eggs of some flies that generally breed in the nasal cavity and sinuses of sheep. In persons with poor hygiene and debility of any age may attract the offending flies that lay eggs in the conjunctiva, nose or any open and non-healing wound.

There are no systemic involvement.

Ocular myasis can either be myiasis externa, which is more common and caused by first stage larvae or myiasis interna, which is rarer and caused by second stage larvae.

The ocular myiasis externa consists of conjunctival irritation, itching, edema, photophobia. A sticky white membrane is formed in the fornix and many larvae can be seen under this. Sometimes they may be seen in lacrimal sac or canaliculi. The myiasis externa does not erode the tissue. In myiasis interna, the maggots may burrow in the anterior chamber or the vitreous through sclera leading to sever inflammatory reaction.

Management consist of picking up the maggots by forceps after they have been immobilised by xylocaine.

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