Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

Fundus in optic neuritis :

1.Early changes consist of blurring of disc margin and hyperemia. In some cases disc may look normal in spite of diminished vision and central scotoma when lesion is away from the disc.

2.It may be difficult to differentiate between fully developed optic neuritis and early papilledema.

3.Late changes are pallor of disc.

4.Fully developed neuritis is always associated with cells in the vitreous in front of the disc.

Neurological symptoms. Sometimes patient have numbness of limbs which the patient may ignore because loss of vision is more alarming than numbness. In neuromyelitis optica the disc involvement may precede myelitis or vice versa.

Optic Neuritis in Children52

Optic neuritis in pediatric age group differs from adult optic neuritis in many ways though pathology in both age groups is the same.

1.Optic neuritis in children is less frequent than adults.

2.Both boys and girls are affected equally.

3.Optic neuritis in children is bilateral more often than in adults.

4.Involvement of anterior part of nerve is more common in children.

5.Commonest cause of optic neuritis is viral infection. Optic neuritis starts two to three weeks after onset of systemic viral infection.

6.Optic neuritis is a frequent complication of many vaccines. Optic neuritis sets in after 2-3 weeks of vaccination. Antiviral vaccine cause neuritis, more commonly than antibacterial vaccines.

7.Multiple sclerosis that is a major cause of optic neuritis in adult inflicts children less frequently.

8.Severity is more in children. Initial loss of vision is profound and disc swelling relatively more than in adults.

9.Chances of visual recovery in children is very good.

10.Optic neuritis in children responds well to steroids.

Management of optic neuritis. Management of optic neuritis is unsatisfactory. There is no specific treatment that will be equally effective in all cases. All efforts should be made to find out the cause as far as possible by neuro imaging, CSF examination, X-ray, chest X-Ray, PNS X-ray orbit.

Thirty percent cases are idiopathic and recover without treatment. In idiopathic optic neuritis recovery of vision following initial abrupt loss of vision take few weeks and complete recovery may take as much as 6-8 months. If there is no improvement in recovery phase, the child should be investigated for some other cause.

Cortico steroids are given only to reduce inflammatory process and hasten recovery. They do not cure neuritis, nor do they influence ultimate recovery. They do not reduce chance of relapse.

Some Specific Type of Optic Neuritis

1.Post vaccination optic neuritis. One of the untoward side effects of prophylactic vaccination against host of diseases, both viral and bacterial diseases, are delayed optic neuritis which is more frequent in antiviral vaccination than bacterial immunisation. It develops two to three weeks after vaccination, is generally bilateral and self limiting. Common prophylaxises that are known to cause optic neuritis are - Hepatitis B, rabies, measles, mums, rubella, and tetanus toxoid.

2.Neuro neuritis. Commonest cause of neuro retinitis in children is toxoplasmosis. Other systemic causes like syphilis, tuberculosis which are common in adults are generally do not cause neuro retinitis in children.

3.Retro bulbar neuritis. Acute retrobulbar neuritis is common in older children due to acute sinusitis. Chronic retrobulbar optic neuritis which is also known as toxic amblyopia is unknown in children. Retrobulbar neuritis may not show signs of inflammation on optic nerve head.

4.Drug induced optic neuritis. Drug induced optic neuritis is common following administration of anti tubercular drugs i.e. streptomycin, isoniazide and ethambutol, another drug used commonly in children is chloroquine. Fortunately chloramphenicol is no more used as routine drug for typhoid hence incidence of chloremphenicol induced optic neuritis is rare. Drugs may involve any part of the optic nerve. Retro bulbar involvement is more common. Management consists of withdrawal of the drug whenever possible. In some instances vision may not return to normal even after withdrawal of offending drug due to irreversible neuronal damage. In such cases other possibilities should be excluded by complete physical examination, CT and MRI.

Demyelinating diseases. Demyelinating diseases are common systemic causes of visuocortical tract involvement that may spread from disc to lateral geniculate body and even the optic radiation56. The common demyelinating diseases that involve optic nerves are53—

1.Multiple sclerosis

2.Devic’s neuromyelitis

3.Schilder’s disease

4.Acute disseminated encephalomyelitis

5.Krabbe’s disease.

Multiple sclerosis54, 55 is a very prominent cause of optic neuritis in adults. It is not a frequent cause of optic neuritis in children. One third of all patients with multiple sclerosis develop optic neuritis, sometimes or other in the course of disease that may last for 20 to 30 years. About thirty percent of acute idiopathic optic neuritis develop multiple sclerosis. In

fifteen percent of cases optic neuritis is presenting sign of multiple sclerosis. Spinal cord is the commonest site of involvement. Visual loss is unilateral with deep central scotoma and marked colour defect. Diminished nerve conduction is the cause of visual impairment. There may be an afferent pupillary defect. There is pain on movement of the eyeball. There may be involvement of any of the cranial nerve that supply the extra ocular muscles in various combination. Muscles may be involved in inter nuclear ophthalmoplegia Uhthoff sign is common, so is Pulfrich phenomenon in which the patient has better vision in dim light.

Devic’s neuromyelitis optica. This is seen in children and young adults but progresses well into pre senile age. It involves boys and girls equally. It is an acute disease that starts as acute, bilateral loss of vision, which need not be equal in two eyes. Myelitis, which is a constant feature may follow neuritis or precede it. It involves the spinal cord, and the optic nerve. Other cranial nerves are spared. It may involve sympathetic chain as well.

Visual field defects depend upon presence of demyelination in the optic nerve.

Myelitis results in paraplegia. It is generally acute in nature and profound. Most patients show considerable improvement in motor function, some residual effect is universal.

Some visual recovery is the rule.

Recurrence of neuritis and myelitis is common. It should be differentiated from other causes of bilateral optic neuritis.

Fundus changes depend upon part of the optic nerve involvement and its severity. It may range between normal disc when the lesion is far back in the nerve, to frank swelling when the lesion extends in the pre lamilar part.

Schilder’s disease56. This is a genetically determined in born error of metabolism where there is primary degeneration of adrenal gland. The disorder belongs to a group of disorders known as leukodystrophies. The condition has profound neurological deficiencies besides loss of vision. Loss of vision is due to neuritis that is followed by atrophy of optic nerve. There may be cortical blindness. It is associated with hearing loss, slurred speech, mental retardation, ataxia, ophthalmoplegia and nystagmus. There is no known treatment.

Krabbe’s disease56. This is also a leukodystrophy. There is relentless demyelination of not only the optic nerve but also that of cerebrum. There is mental retardation, diffuse sensory loss and motor loss. Blindness is very common not only due to involvement of optic nerve but also optic radiation. There is no specific treatment.

Comparison between optic neuritis, papilledema and pseudo neuritis. Many a times it is difficult to differentiate between fully developed optic neuritis and early papilledema. Same is true between pseudo neuritis (pseudo papilledema) and early papilledema ophthalmoscopically. Other clinical features and investigations have to be gone through when in doubt.

Causes of unilateral disc swelling in children :

1.Ocular57 :

—Papillitis

—Drusen of optic nerve head

—Ocular hypotony

—Severe intraocular inflammation

—Neuro retinitis

—Pseudo neuritis

—Optic nerve glioma

—Orbital cellulitis

2.Intracranial :

—Foster Kennedy syndrome

—Unilateral high myopia with raised intra cranial tension. The normal eye develops disc swelling.

—Cavernous sinus thrombosis

3.Pseudo tumour ceribri (initial stage) Sub arachnoid haemorrhage.

Optic Atrophy

Optic atrophy. Optic atrophy is not a disease. It is the end result of many diseases, where the optic nerve is virtually a scar with loss of its function. It has been defined in various ways, the sum total of which says that optic atrophy occurs due to degeneration of axons in the anterior visual pathway.

Anatomically it has been divided into :

1.Ascending optic atrophy where the pathology spreads from the retinal ganglion cells towards lateral geniculate body.

2.Descending optic atrophy—Here the degeneration spreads from lateral geniculate body to optic nerve.

Other classifications are :

On the basis of ophthalmoscopic appearance :

1.Primary (simple) optic atrophy

2.Secondary optic atrophy— Post neuritic

Post papilledematous

3.Consecutive optic atrophy

4.Cavernous optic atrophy

5.Glaucomatous optic atrophy

6.Temporal pallor.

7.Bow tie pallor

Etiological classification

The causes of optic atrophy in children can be :

1.Heredo familial

2.Post papilledematous

3.Post neuritic

4.Trauma

5.Consecutive

6.Toxic

7.Nutritional

8.Metabolic (Juvenile diabetes mellitus, mucopolysaccharidosis)

Primary optic atrophy. In this type of optic atrophy no visible cause that may involve the optic disc i.e. disease of choroid, retina, or optic nerve (optic neuritis) is detectable. There is no evidence of raised intra cranial tension. The lesion is in the second visual neuron proximal to disc.30

This is due to degeneration of optic nerve fibres with minimal glial proliferation without any mesenchymal reaction.31 The myeline sheath and axis cylinders disappears, there is shrinkage of optic nerve. At the disc there is reduction in nerve tissue, this results in increase in width and depth of optic cup and exposes the holes in lamina cribrosa. The optic cup becomes pale. The cause of whitening was thought to be paucity of capillaries on the disc head.30 Now it is thought to be due to impaired transmission of light into the substance of the disc. This is brought about due to absence of axonal fibres, which are responsible for transmission of light32.

Commonest cause of primary optic atrophy in adults is tabes dorsalis which is not seen in children. In children the cause of primary optic atrophy are - hydrocephaly, toxic, retrobulbar neuritis, traumatic opticneuropathy, heredo familial optic neuropathy.

The clinical presentation consists of visual, pupillary change and pallor of disc.

Visual symptoms consist of diminished distant vision, central scotoma, colour deficiency, reduced contrast sensitivity and stereopsis.

Pupillary changes consist of large pupil and afferent pupillary change. In bilateral primary optic atrophy both pupil are large and sluggish. Bilateral immobile pupil is sign of gross loss of vision.

Fundus change. The media is clear. The margin of the disc is clear cut. The colour of disc has been called by various adjectives i.e. chalk white, marble white or paper white. The number of vessels on the disc is less than ten.33 However on fluorescein angiography, the number of capillaries are more than visible on ophthalmoscope but atrophic, no leak or pooling is seen. The cup is deeper than normal physiological cup and may be mistaken as glaucomatous. The width of the cup is also more than normal. The lamina cribrosa is visible as bluish dots. The vessels have normal calibre and do not show any sheathing. The peripapillary retina and choroid are normal. The primary optic atrophy is an example of descending optic atrophy where the lesion may be anywhere from retrobulbar part of optic nerve to the optic radiation.33

Secondary optic nerve. This is more common than primary optic atrophy in children. This is always preceded by swelling of the disc either due to inflammation, which is associated with active congestion or with passive congestion as in papilledema or uniocular disc edema.

The atrophy is also a degenerative process of the optic nerve, have more reactive elements than primary atrophy.

The degenerative process is obscured by proliferation of astrocytes, glial tissue and to some extent blood vessels.

It is more common than primary optic atrophy in all ages.

The condition is equally common following either papillitis or papilledema. In children secondary optic atrophy is usually bilateral.

The symptoms of secondary optic atrophy are similar to that of primary optic atrophy, only difference is that the former is preceded by symptoms of either papillitis or papilledema.

The signs are also same as far as field changes and pupillary reaction is concerned. The main difference lies in fundus picture.

The fundus picture. The media is not affected. The margin of the disc is blurred. The disc may be raised in spite of onset of atrophy. In fully developed secondary optic atrophy, the swelling subsides but never regresses in the disc, thus the physiological cup is always obliterated and lamina is not visible. The vessels always show some degree of sheathing. The retina and choroid are not affected. The disc has dirty yellow colour.

It is not possible to differentiate between post papilledematous and post papillitis optic atrophy.

The field when possible to chart shows enlargement of blind spot. Onset of atrophy is heralded by gradual constriction of peripheral field, ultimately only a central island of vision may be left.

Consecutive optic atrophy. This is an ascending type of optic atrophy, which is essentially secondary to disease of retina, choroid or both. It may be unilateral or bilateral.

The fundus picture comprises of : The disc is pale but colour is waxy white. The disc margin is almost normal but not as clear cut as in primary optic atrophy. The cup is maintained unless there was a concurrent involvement of optic nerve as seen in neuroretinitis. The calibre of the blood vessels depend upon their involvement in primary chorioretinal lesion. They are attenuated in retinal abiotrophy i.e. retinitis pigmentosa. The surrounding fundus shows evidence of chorioretinal scar.

In case of a macular lesion, the atrophy is generally confined to temporal side. In case of patch of choroiditis adjacent to the disc, the part of the disc near the lesion is atrophied so is in case of choroidal rupture near the disc.

Commonest cause of consecutive optic atrophy is retinitis pigmentosa. Other causes are diffuse chorioretinitis, toxic retinopathy, extensive photocoagulation.33

The symptoms of consecutive optic atrophy is overshadowed by symptoms of primary chorioretinal pathology.

Cavernous optic atrophy. This type of optic atrophy is rare in children. There is mucoid degeneration of the optic nerve head. There is no proliferation of glial tissue. On histology empty spaces are formed in between the nerve fibres which are filled with mucoid material.32 The fundus picture is in between primary optic atrophy and glaucomatous optic atrophy, there is prominent pale cup in pale nerve with nasal shift of blood vessels.

Temporal pallor. This is partial optic atrophy due to involvement of papillo macular bundle. Commonest cause is a lesion either in the macula or in between the macula and the disc. It could be a congenital anomaly of macula i.e. macular coloboma, toxoplasmal chorioretinitis or rupture of choroid between the macula and disc. Laser burns too near the disc on temporal side. Other causes are toxic neuritis, old retro bulbar neuritis, heredofamilial optic atrophies, Leber’s optic atrophy, Behr’s optic atrophy, Kjers optic atrophy.

Some specific types of optic atrophy :

Traumatic optic neuropathy. Trauma to optic nerve direct or indirect is the cause of traumatic optic atrophy. The injury can be a closed head trauma, an injury to the frontal bone, or a trivial injury on the eyebrow. The optic nerve can be injured anywhere from chiasma to entry of nerve in the sclera. It can be avulsed if the eyeball is caught in a curved object and pulled anteriorly besides avulsion such injuries can stretch the optic nerve, can cause haemorrhage in the sheath. The optic nerve may be severed by a bullet injury, fragment of granade, or by a stab injury in the orbit. The intraorbital part may be injured during retrobulbar injection, or during facio orbital surgery.

In avulsion of optic nerve, there is sudden loss of vision with severe pain, may be associated with mild proptosis and restricted movement. On ophthalmoscopy there are large blotches of haemorrhages round the disc. Gradually as the haemorrhages clear, a pale disc almost devoid of any vessels becomes visible. The resultant atrophy is primary optic atrophy in nature.

Injury behind the entry of central retinal vessels and optic canal does not produce any change on fundus examination initially. It takes four to five weeks for the change to appear in the form of primary optic atrophy. The intracanalicular part of the nerve is most likely to be injured in closed head injury.

The mechanism of damage to intra canalicular part of optic nerve is :

Rotational and shearing force that push the frontal lobe, pull the nerve back. The shearing force is transmitted to immobile optic nerve in the canal.

Accumulation of blood or edema may throttle the blood flow of the optic nerve. Bone fragments from the fractured canal may get lodged in the substance of the nerve or may press the nerve from outside.

Traumatic optic neuropathy is a common accident in children, more frequent in boys. It is commonly seen following a cricket ball injury to the lateral side of the eyebrow, in fact any hard object hitting the frontal bone is likely to cause traumatic optic neuropathy.

It is generally unilateral. Bilateral traumatic optic neuropathy is seen in closed head injury that damages the chiasma. The symptoms may be acute loss of vision if the injury is with in 10 mm of the posterior scleral canal and is generally profound. Vision may be reduced

to perception of light, which may be lost altogether. Loss of vision following injury to posterior part of the optic nerve is variable between moderate loss to loss of perception.

In uniocular profound loss of vision there may be afferent pupillary defect.

Diagnosis of traumatic optic neuropathy is generally delayed due to overwhelming signs and symptoms of head injury. Diminished unilateral loss of vision following frontal head injury with afferent pupil on the same side is a strong point in favour of traumatic optic neuropathy that is confirmed by - fundus examination, field charting, CT and MRI. CT is superior to MRI in outlining fracture of bones. MRI gives better image of soft tissue damage. MRI is contra indicated if there is suspicion of intra orbital or intra cranial metallic foreign body that should be excluded by plain X-ray first.

Treatment consists of :

1.Management of head and cranio facial injury. This should get priority over ocular treatment because these can be life threatening to the child.

2.Ocular therapy should be started as soon as the child is stable.

Ocular treatment is :

1.Medical. This consists of heavy dose of I.V. steroid. The drug of choice is methyl prednisolone as 30 mg/kg35 as loading dose followed by 5.4 mg/kg/hr for 48 hours to 72 hours or dexamethasone 3-5 mg/kg/day is given if vision improves. Methyl prednisolone is continued for 2-3 days and then replaced by oral prednisolone in tapering dose. If there is deterioration of vision while on oral steroid, I.V. methyl prednisolone is restarted. If there is no improvement in first 72 hours following initial start of I.V. methyl prednisolone, surgery should be considered which consists of fenestration of optic nerve sheath or removal of roof of optic canal via trans nasal or trans ethmoidal route by endoscope.

Heredo Familial Optic Neuropathy36, 37, 38

Heredo familial optic neuropathies comprise of a group of hereditary degeneration of optic nerve that manifest under 15 years of age. The causative factor may be present at birth but the condition manifests late. They are generally bilateral, most of the clinical presentation in two eyes is similar. They progress gradually, may terminate in complete blindness, may have only ocular manifestation or may be multi-systemic in nature.

Heredo familial optic degeneration can belong to following groups :

1.Optic abiotrophies

2.Associated with retinal dystrophies

3.Storage diseases.

The common conditions are39

1.Leber’s optic neuropathy

2.Kjer’s dominant juvenile neuropathy

3.Behr’s recessive neuropathy

4.Optic neuropathy in juvenile diabetics.

Leber’s optic atrophy40. This is a heredo familial optic neuropathy also known as Leber’s disease. This is not to be confused with Leber’s congenital amaurosis which is a congenital retinal pigment degeneration and not a neuropathy.

This disease is seen between 5 years to 30 years of age, commonest manifestation is at onset of puberty. Ninety percent affected are boys.

The disease is passed on to children of carrier women who may or may not have the disease. The affected males do not pass the disease to their children including daughters. The affected child may have fully developed disease in his sibling or younger siblings may develop the disease later. Besides brothers there may be positive evidence of disease in maternal uncles. Most of the sisters of the affected child may be carriers. Female carrier do not have affected father. The social aspect of the inheritance is that it is not the affected man who spreads the pathological gene but the unaffected sister.

The biogenetic defect of the disease lies in the mitochondrial DNA of the mother due to mutation. Several different mutations have been identified.41

There is defect in :

—Oxydative phosphorylation

—Cyanide metabolism

—Reduced zinc in plasma

The disease starts as rapid fall of vision in both eyes. Occasionally one eye may be involved earlier than the other. Initial fall may be up to 6/60 or less. The initial fall may continue in slower rate and stops at lowest level then may start improving. Improvement is never beyond 6/24. There is partial or total loss of colour sense, stereopsis and contrast. There is a large dense absolute central or centrocecal scotoma which is surrounded by relative scotoma or a relative scotoma may become denser and absolute. On fundus examination, the disc may look normal or may be swollen. The disc develops secondary optic atrophy. The basic pathology is retrobulbar. The commonest fibres to be affected are papillo macular hence commonest type of optic atrophy is temporal pallor to begin with which can spread all over the disc. Peripapillary telangiectasia and micro vasculo angiopathy is common that disappears in late stages. Rest of the fundus is normal. There are no exudates or haemorrhages as seen in optic neuritis.

The disease can be divided into following stages :

1.Asymptomatic—These are generally the siblings and carriers. They may show peripapillary telangiectasia and tortuosity of large vessels.

2.Stage of rapid fall of vision.

3.Stage of slow fall of vision and slight improvement of vision.

4.Stage of optic atrophy with some vision.

5.Blindness.

Treatment. There is no specific treatment. In stage of neuritis, systemic steroids have been used without much success. Commonly used drugs are :

1.High doses of hydroxycobalamin given intra muscular.

2.Oral cystine.

3.Oral zinc.