Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

fifty enzymes in vitreous, the functions of which are not clear. The collagen is capable of binding with water, which could be as much as 200 times the weight of the collagen, to form a hydro gel of highest viscosity.

Development of vitreous16,17,18

Developmentally vitreous has three phases:

1.Primary vitreous

2.Secondary vitreous

3.Tertiary vitreous

Developmentally vitreous has dual origin it is partly ectodermal and partly mesodermal.

The primary vitreous starts developing very early and its development is completed by 13 mm stage. It develops in the space between the lens and the retina. During first month of development cells from the lens and retina form the primary vitreous. The retinal cells dominate over the lenticular cells. The cells from the lens loose their contact from the primary vitreous due to formation of lens capsule. The cells from the retina continue to contribute towards development of primary vitreous. The lens is further isolated from the vitreous by developing tunica vesculosa lentis.

The tunica vasculosa lentis is mesodermal part of primary vitreous. The hyaloid artery, which is a branch of developing internal carotid, (actually primitive dorsal ophthalmic artery) enters the optic cup through the embrayonic fissure. The hyaloid artery communicates with the capillaries on the ventral aspect of the developing lens to form the tunica vesculosa lentis. The hyaloid system starts disappearing by 65 mm and at birth there is no evidence of the hyaloid artery only the proximal part of the hyaloid artery remains patent and forms the central artery of the retina.

The secondary vitreous

The secondary vitreous is the part of the developing vitreous, which lasts for rest of the life. It is avascular and is secreted by the cells from the inner surface of the optic cup and pushes the primary vitreous centrally. The primary vitreous gradually disappears leaving no trace except the Coloquet canal.

The tertiary vitreous

The tertiary vitreous is secreted by the ciliary epithelium. This occupies a triangular area between the developing ciliary body and the lens. With the development of the eye, the ciliary body that was very near to the lens, withdraws away from the lens and the fibres become more clearly defined. The fibres divide into two groups - The anterior part in just behind the iris and gets attached to the anterior lens capsule, the posterior part runs parallel to the anterior vitreous membrane and get attached to the posterior lens capsule. These fibers, ultimately form the zonules of the lens.

Congenital anomalies of the vitreous

In spite of being most voluminous intra ocular structure, the congenital anomalies of the vitreous are few. The congenital anomalies directly correspond to the stage of development of the vitreous.

The congenital anomalies may be as small and insignificant as vitreous floaters or as extensive as to replace the whole of the vitreous by mesodermal tissue. The former is very common while the latter is very rare.

The congenital anomalies mostly involve the mesodermal tissue. They can be:

1.Limited to hyaloid vascular system without hyperplastic changes in vitreous or,

2.They may be associated with hyperplastic changes in the vitreous.

Anomalies of hyaloid vascular system

There are three possibilities:

1.The whole of the artery may be seen to exist between the posterior lens capsule to optic nerve head. The vessel is attenuated, may contain blood. This is very rare.

2.The anterior end of the artery may persist as a free floating stalk attached to the posterior lens capsule.

3.The posterior end may remain attached to the optic nerve head.

4.Occasionally the remnants of the posterior part of the tunica vasculosa lentis may persist as grey opacity in the posterior lens capsule and is called Mittndrof dot. This is almost asymptomatic, may be visible on oblique illumination, look like a black dot in pink retinoscopy glow, seen best by slit lamp.

5.The remnants of the posterior part of the hyaloid artery is known as Bergmeister’s papilla. This too is asymptomatic but when large may be mistaken as growth on the optic nerve. The papilla is made up of central core of vessel surrounded by fibro glial tissue.

Persistent hyper plastic primary vitreous (see chapter Retinoblastoma) Symptoms of diseases of vitreous

Diseases of vitreous are rare in children as compared to adults.

The two functions of the vitreous are optical and support to the retina, one or both may be involved. Moreover diseases of surrounding structure may also involve the vitreous i.e. the retinal vessels may bleed to cause bleeding in the vitreous.

The vitreous being avascular is not capable of bleeding. The vitreous itself is not capable of inflamation either, but is generally involved in inflamation of choroid or retina that may be either in the form of endophthalmitis or vitritis. Vitritis is a condition where inflammatory cells from choroid, retina or optic nerve invade the vitreous without exudation.

Commonest symptom of vitreous disorder is vitreous floaters. Other symptoms are - photopsia, a visible ring shaped opacity, erythropsia, diminished vision, sudden painless loss of vision. The symptoms may be unilateral or bilateral. The vitreous is devoid of any nerve supply, hence disease of the vitreous alone is painless.

Signs of vitreous disorders

The sings comprise of

460 PEDIATRIC OPHTHALMOLOGY

1. Diminished vision.

The vitrial causes of diminished vision are: (i) Large opacities in front of the macula

(ii) Haemorrhage in front of the macula—Diminished vision may range from loss of one to two lines on Snellen’s chart or the vision may be reduced to perception of light. Disorder of vitreous never causes loss of perception or faulty projection.

2.Oblique illumination—Only a few physical findings of vitreous can be seen on oblique illumination. They are:

(i) Retrolental white mass

(ii) Strands of liquid anterior vitreous

(iii) Less commonly a bloch of fresh haemorrhage can be seen just behind the lens or in the lower part of the vitreous, when the patient looks down with dilated pupil.

3.Slit lamp biomicroscopy—Ordinary biomicroscopy can not focus the whole depth of the vitreous unless the optics of the eye is modified to bring the various depths of vitreous within the focus of the slit lamp biomicroscope. This can be brought about by

(i) Goldman three-mirror contact lens—Its central part brings the posterior pole in focus. The mirror with an angle of 55° focuses the vitreous up to ora serrata, while the mirror with 67° angulation can focus the peripheral fundus.

(ii) Hruby lens this is a pre set concave lens of – 55D

(iii) El Bayadi lens—This is a pre set convex lens of + 55D.

Beside these there are other lenses i.e. + 90D or + 78D that are also used to view the vitreous with slit lamp.

4.Ophthalmoscopy—Both direct and indirect ophthalmoscopes are used to examine the fundus. Indirect ophthalmoscope has added advantage of stereopsis, larger field and brighter illumination.

5.Ultrasonography—Both A and B scans are used. B scan gives better view than A scan. Both are useful in opaque media.

6.X-ray. It is indicated only when intra ocular foreign body is suspected. Both AP and true lateral view should be taken.

7.Electroretinography—ERG has limited role in transparent media. In opaque media, a non recordable ERG is not an absolute contra indication for vitreous surgery because a totally detached retina that gives non recordable ERG on successful attachment may gain some visual function.

8.Fluorescein angiography is indicated in proliferative vascular retinopathy and cystoid macular edema that is common following vitreous loss.

Vitreous opacities (floaters)

Vitreous opacities are commonest symptom of disease of vitreous. They cause loss of transparency of the vitreous, may be in the form of scattered dots, strings, sheets. They are generally mobile, hence called floaters. They may change their position in space in different

direction of movement, may be felt all through the waking hours or may be more visible after sleep. They are not visible in darkness or when the eyes are closed.

Vitreous opacities can result due to—

1.Primary change in the vitreous

2.Secondary changes in the vitreous due to pathology in retina, choroid, and optic nerve.

Primary changes in vitreous

Muscae volitantes

These opacities are so common that they are considered to be physiological. They represent remnants of primary vitreous. They can be unilateral or bilateral, are not associated with loss of vision. They are perceived either as scattered dots or dots in string. They are best seen against light coloured background such as sky or white wall. They have no pathological significance nor do they require any treatment. Sudden onset of shower of vitreous floaters should not be taken lightly. All such eyes should be examined with indirect ophthalmoscope, as it may be the beginning of parsplanitis, retinal break or inflammation of the uvea. Floaters are common in moderate to high myopia due to degenerative change in the vitreous.

Vitreous degeneration

Vitreous is a semisolid gel, does not show any movement or ripple within its body unless it is liquefied. Vitreous in a child’s eye is more firm and solid than vitreous in senile group.

The liquefication of the vitreous is known as synchisis. It is a common feature of old age. In children liquefication is seen in high myopia and trauma with or without retained foreign body. It is also seen following vitreous haemorrhage, endophthalmitis and severe posterior uveitis. The vitreous looses its semisolid nature and becomes watery in consistency. It may be so fluid as to flow out during intra capsular lens extraction in age related cataract.

The liquification invariably leads to syneresis or collapse of vitreous. Liquified vitreous does not require any specific treatment.

Synchisis scintillans

This is a different kind of liquifaction of vitreous seen in younger patients, is bilateral without much complains. The patient may not be aware of its presence. There is deposition of cholesterol crystals in the vitreous. The crystals are suspended in the vitreous. They may remain hidden at the bottom of the vitreous and become visible on movement of the eye like golden shower. Sometimes they are visible on oblique illumination in clear media. They are best seen by slit lamp. They are also visible with direct ophthalmoscope. On retinoscopy they may be visible as cloudy dots. Synchisis scintillans does not require any treatment and persist life long. They are not to be confused with astroid hyalitis, which is seen in elderly males. They are accumulation of calcium soaps and are fixed bodies, show minimum movement.

Vitreous detachment

Normal vitreous does not detach from its attachment. For a vitreous to detach its consistency must change towards fluid rather than semi solid gel. It is more common after sixth decade but not exceptional under twenty. The common causes of vitreous detachment in

children are—Myopia, chronic uveitis, trauma, both concussion and penetrating, vitreous haemorrhage, vitreous disturbance during intra ocular surgery.

According to configuration of the detachment, it has been divided into two broad groups:

1.Posterior vitreous detachment (P.V.D.)

2.Anterior vitreous detachment.

The posterior vitreous detachment is more common than anterior vitreous detach-

ment.

Posterior vitreous detachment can be

1.Small peripheral, which may later increases in size.

2.Infundibular or conical detachment—When the vitreous is attached round the disc and base but separated from internal limiting layer of the retina all round.

3.Globular detachment—When the attachment round the disc has been severed but the basal attachment is maintained.

The posterior vitreous detachment can be simple or with collapse. In simple PVD, the detached posterior surface retains its spherical shape. In detachment with collapse, the detached posterior border of the vitreous hangs vertically from the region of its superior base.

Anterior vitreous detachment

The whole of the anterior vitreous cortex is separated from the lens, zonule and base, pushing the vitreous posteriorly. It can be localised to zonule or lens or both.

Symptoms of vitreous detachment are variable. It may be symptomless. Common symptoms are photophobia, and floaters in front of the eye or a Weiss ring, which is an annular vitreous floater due to detachment of posterior vitreous from the optic nerve head.

There is no specific treatment for vitreous detachment. All cases of vitreous detachment should be examined by indirect ophthalmoscope for possibility of peripheral retinal degeneration and holes, which may require treatment to prevent rhegmatogenous retinal detachment.

Vitreous haemorrhage

Vitreous haemorrhage is in fact an inter vitreal bleeding originating from retinal vessels. Vitreous being avascular, is incapable of bleeding.

Vitreous haemorrhage is a common causes of painless, sudden loss of vision which when unilateral may go unnoticed in children. If the cause of the bleeding is local, the bleeding is unilateral. It is bilateral if the cause is systemic. Vitreous haemorrhage is less common in children. The commonest cause of bleeding in third and fourth decade is periphlebitis (Eale’s disease) which in not seen under fifteen years of age. In fourth decade onwards incidence of diabetics proliferative retinopathy and venous obstruction, which are again not seen in children are the main causes of vitreous haemorrhage. However, proliferative retinopathy in juvenile diabetes may on occasion present as vitreous haemorrhage.

The common causes of vitreous haemorrhage in children are:

1.Congenital—Persistent primary hyper plastic vitreous, angiomatosis, Coat’s disease, remnants of hyaloid vessels.

2.Trauma—By far trauma is the commonest cause of vitreous haemorrhage in children. It can be blunt injury or may be penetrating injury. Blast injuries may cause bilateral vitreous haemorrhage. Rupture of retinal vessels due to vitreo retinal traction, a vessel passing across a large tear can also bleed.

3.Blood dyscrasia—Leukaemia, purpura and other coagulation disorders can cause vitreous haemorrhage.

4.Inflammation—Periphlebitis is commonest cause of vitreous haemorrhage in third and fourth decade and parsplanitis is less common cause in that group. Parsplanitis is more likely to cause haemorrhage in children than periphlebitis.

Miscellaneous

1.Terson’s syndrome, where a sub arachnoid haemorrhage near the optic disc may trickle down to sub hyaloid space.

2.Retinopathy of prematurity

3.Inadvertent perforation a globe during squint, retinal surgery, retro bulbar or peri bulbar injection can also cause vitreous haemorrhage.

Symptoms of vitreous haemorrhage

A bleeding away from the posterior pole may be asymptomatic and go unnoticed. Commonest symptom of a pre macular haemorrhage is sudden, painless loss of vision that may vary between loss of one to two times on Snellen’s chart to only perception of light. The patient may have better vision as the blood settles down only to be reduced when the blood comes in front of the macula.

One rare occasions, small haemorrhage may present as showers of floaters. In still rarer conditions there may be erythropsia.

Signs of vitreous haemorrhage

On rare occasions fresh blood in anterior vitreous may be visible on oblique illumination.

Commonest form of presentation is a keel shaped sub hyaloid haemorrhage that has red colour with round bottom with a horizontal line denoting the upper limit of settled blood.

A massive intra vitrial haemorrhage may obscure the fundus when seen by direct ophthalmoscope. The same when viewed by indirect ophthalmoscope makes it possible to see the retinal periphery that may have the clue to the haemorrhage i.e. tear, degeneration, disinsertion, parsplanitis.

Fate of vitreous haemorrhage

Vitreous haemorrhage is a self-limiting disease. In four to six weeks the haemorrhage is absorbed without leaving trace of haemorrhage. However, recurrence of bleeding takes more time to absorb than original bleeding. Each episode of bleeding lasts longer than the previous one. Recurrent and non absorbing haemorrhage may lead to formation of vitreous bands and are called retinitis proliferans. It generally starts near the disc where the central retinal artery is rich in mesoblastic tissue. If haemorrhage does not clear within six months the condition

is called hemophthalmos where no part of the retina is visible on ophthalmoscopy, retinoscopy or slit lamp examination. The only useful investigation in such cases is ocular ultrasonography that may show retinal detachment as well.

Management of vitreous haemorrhage

There is no specific treatment for vitreous haemorrhage. Most of the vitreous haemorrhage get absorbed by four to six weeks. Some of the new vessels may require closure by laser or cryocoagulation. Vitreous haemorrhage not clearing by three months require parsplana vitrectomy, some may require additional endo laser coagulation. Associated retinal detachment is treated by standard methods.

Vitreo retinal degeneration66,67,68,69

These are a group of inherited conditions that manifest in childhood due to close proximity of retina and lens during development of the vitreous. The vitreous is seldom involved alone in these degenerative conditions.

The condition can be divided in two broad groups:

1.Those that have only ocular involvement

2.Those that have associated systemic involvement along with vitreo retinal degenerations:

The group I consist of

—Stickler syndrome.

—Wagner’s disease.

—Congenital retinoschisis

—Favre Goldmann syndrome

—Exudative vitreo retinopathy

—Snow flake degeneration

The group II Consist of

—Marfan’s syndrome.

—Homocystinuria.

—Ehlers-Danlos syndrome

—Lawrence-Moon-Biedl syndrome.

Most of the conditions in-group I have predominant ocular involvement but may have systemic involvement as well especially in Stickler syndrome.

Stickler syndrome

It is an autosomal dominant disorder, the children may have skeletal changes similar to Marfan’s syndrome. Joint involvement is common, the ocular change consist of vitreo retinal degeneration that consist of liquified vitreous with collapse giving an optically empty vitreous. Translucent membrane may develop on the periphery. The retinal changes include lattice degeneration. There may be sheathing of peripheral retinal vessels. Peripheral retina

shows clumps of vitreo retinal scar. Retinal detachment is common. There is mild to moderate degree of myopia. Cataract and open angle glaucoma are common complications.

Wagner’s disease

This is as an autosomal dominant inheritance. The ocular structures involved besides vitreous are retina, optic nerve and lens. The vitreous changes are similar to those seen in Stickler’s disease without retinal detachment. There may be diminished night vision with abnormal ERG. The disease is generally bilateral, starts in infancy and continues in adolescence. Liquification of vitreous is seen after second decade.

Congenital retinoschisis (see retina also page 403)

It is also known as juvenile retinochisis, though the retinochisis is a dominant feature both vitreous and retina are involved simultaneously. It is commonly seen in childhood, more common in boys. It is known to be present at birth. The children may be brought to ophthalmologist for presence of strabismus and/or nystagmus and on examination found to have congenital retinochisis. The condition grows slowly, there may be periods of worsening in between the main fundus finding consists of retinochisis. The inner layer of retinochisis is extremely thin, the blood vessels on the inner leaf are normal. The inner leaf has large hole resulting into smooth ballooning of immobile inner leaf. The outer layer is difficult to distinguish until it is detached from the RPE, which happens when the outer layer also develops hole. There may be some haemorrhage in the vitreous. The posterior border of schisis may show line of pigmentary demarcation.

The retinoschisis may remain on the periphery or may extend into the macula. The maculopathy consists of small cystoid spaces with radial lines, which probably represent folds in the internal limiting membrane. The appearance is called bicycle-wheel pattern, which does not fluorescence. The Cloquet’s canal seems to be larger, the vision is diminished if either the macula is involved or there is retinal detachment.

The condition has x linked inheritance. It is bilateral and ERG shows subnormal B wave with normal A wave.

Management

There is no specific treatment that may give uniformly satisfactory results. The modalites tried are—Photo coagulation of outer layer this may regress the condition and the balloon may flatten. Photo coagulation is more indicated if there is a hole in the outer leaf. Retinal detachment when present, it is treated by standard retinal detachment surgery.

Favre—Goldmann syndrome

This is a vitreo retinal degeneration that has night blindness as main symptom. It is an autosomal recessive disease. It affects boys and girls equally, it is generally bilateral. The vitreous is liquified, may have peri retinal membrane. Retinochisis and retinal detachment are seen. The other symptoms are diminished vision, floaters, ERG is sub normal or absent. Cataract is a common complication. There is no specific treatment.

Familial exudative vitreo retinopathy

This autosomal dominant disorder is also known as Criswick-Schepen Syndrome. The ocular involvement is generally bilateral and symmetrical. The condition can be present in two forms:

1.The child is asymptomatic and the condition is detected on routine ophthalmoscopy.

2.The child is brought with squint and found to have diminished vision.

The fundus findings are less in the first group that includes peripheral avascular zone, arterio venous anastomosis, vitreo retinal adhesion. The condition may be mistaken as retinopathy of prematurity.

In second group—The vitreo retinal findings are more extensive and have more similarity to retinopathy of prematurity. This includes retinal and pre retinal haemorrhage, exudation, fibro vascular bands, retinal fold, retinal detachment.

The children have moderate myopia, the retina may show white with pressure or without pressure.

There is no specific treatment.

Snow flake degeneration

This is rarer than those described above. It is an autosomal dominant disorder that has myopia and pre senile cataract for which the patient may seek help. On examination it is found to have following:

Wide spread areas of white with pressure that may have snow flake deposits. Posterior to snow flakes there may be increased pigment deposit. The peripheral retinal vessels show sheathing, there may be breaks in the retina leading to detachment.

Lebers congenital amaurosis70

This is one of the frequent causes of blindness in new born. The child may be blind from birth or goes blind during first year. Poor vision from early months predispose nystagmus.

Poor vision and nystagmus herald sttrabismus. Parents of these children with squint and/or nystagmus bring the child to the ophthalmologist to know if the child has vision or not71. Unfortunately they are told that the child has very poor uncorrectable vision. The child develops a peculiar habit of rubbing the eyes. The condition is autosomal recessive in nature. Fundus findings are variable, initially the fundi may look normal or may have pepper and salt like pigmentation all over the retina. Later they may develop bone spicule pigmentation similar to retinitis pigmentosa, which is not seen in such a young child.

These children generally have high hypermetropia. The pupillary reaction may be sluggish or paradoxical.

ERG both photopic and scotopic are subnormal. The patients may have keratoconus, keratoglobus, and cataract. Mental retardation is common.

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