Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

9.Cornea. The cornea is normal but may show megalo cornea, keratoconous or even cornea plana.

10.Sclera. The sclera is thin and stretched may have small staphylomas.

11.Error of Refraction. If there is gross difference in refraction between the two eyes there may be squint and ambloyopia, rarely their may be ptosis.

12.Glaucoma: Eight percent of the eyes have developmental glaucoma that is generally open angle glaucoma rarely the lens may be entrapped in the pupil causing pupillary block glaucoma.

B. Skeletal Changes

Skeletal Changes are prominent and may be the first cause to bring the child to the physician. The child is tall and thin for age, most striking are long slender limbs, the span of out stretched arms is more than the height of the child, the fingers are long, spidery hence called arachnodyctalous. The tip of the thumb passes beyond the ulnar border of the palm when flexed. The thumb and index finger of one hand when wrapped round the wrist of the other hand, over lap each other. The thumb can be extended back wards to touch the radial border of the forearm. The metacarpals and phalanges are long and thin. The large joints are prone for subluxation. The head is often dolicocephalous with high arched palet.The spine shows scolio kyphosis. Occasionally there may be hemivertebrae, and spinabifeda. The chest is long and narrow, the sternum shows pactus deformity.The muscle are hypoplastic, the skin is loose without subcutaneous fat, weakness in abdominal muscles predispose hernia formation.

C. Cardiac changes

Cardiac changes begin with dilatation of aorticroot, leading to aortic insufficiency, fuciform aneurysm of aorta is common and the aneurysm may show dissecting changes.

D. Other changes consists of

Winged scapulae, flat foot, contracture of joints, pulmonary and renal anomalies, malformation of ears. The children have normal I.Q and there is no biochemical changes.

E. Management

Management depends upon severity and duration of the condition it consists of:-

Improvement of vision

1.Some children may not have much visual disturbance inspite of subluxation if there is no error of refraction.

2.When error of refraction is present it is generally axial myopia, because the aphakic is exclude from the pupil due to small, rigid central pupil.

3.With a large aphakic area in the pupil it should be decided if, the child will benefit by minus glasses with constricted pupil or aphakic correction with dilated pupil. Aphakic power is considerably counter balanced by presence of axial myopia hence it is invariably less than

+10D.

4. The lens should not be tempered with unless it is :

Cataractous, dislocated or causing glaucoma.

(a) The lens is generally removed through limbal route.

(b) The posteriorly dislocated lens is removed through parsplana with extensive vitrectomy.

(c) Aphakia is managed by spectacle or contact lens. It is not possible to put an IOL in the bag in subluxated lens following phacofragmentation. The options open are- iris clip lens, lens in the sulcus or sclera fixated lens all which has their advantages and disadvantages.

5. The retinal detachment can be as a part of axial myopia or vitreous disturbance. It may require extensive surgical procedures.

HOMOCYSTINURIA

Homocystinuria is second most common cause of bilateral subluxated lens. It’s skeletal and ocular features have many similarities with that of Marfan’s syndrome. Important differentiating point are:- Homocytiruria is associated with mental retardation, gives positive bio chemical test for uninary homocystine, and is autosomal recessive in nature41 However it is of utmost importance that the two conditions be differentiated because symptoms of homocystinuria can be eliminated by proper diet and medication.

Homocystinuria is one of congenital errors of metabolism due to deficiency of more than one enzyme i.e. methionine metabolism42. The main causes of the clinical features are excess of methionine (an essential amino acid) and homocystine in blood. The patients excrete large amount of homocystine in urine. The syndrome is caused mostly due to lack of cystathionine B. synthase that helps to convert methionine to cystine . The result is rise of methionine and homocystine in body fluid.

The disorder is equally common in boys and girls.

The clinical signs are not noticed at birth. The condition manifests itself by eight to ten years. However the child may show signs of delayed physical milestone from early age. The mental retardation becomes obvious as the child goes to school. This is initially attributed to illhealth and diminished vision. The subluxation of lens becomes apparent by tenth year.

The condition has following components:

A.Ocular

B.Skeletal

C.Mental

D.Cardiovascular

E.Positive biochemical test.

A. The ocular changes comprise of

1. Lens. Bilateral progressive subluxation of lens that has the tendency to fully dislocate. The accommodation is poor or absent. As the zonules are broken which may be matted

over the lens surface39. The shape of the lens may be small and spherical. The lens may develop lamellar opacification.One of the initial presentation may be painful acute loss of vision due to pupillary block or endothelial damage caused by the lens dislocating in A.C. . If the lens dislocates in vitreous it may start phacogenic uveitis and glaucoma or may remain silent. The aphakia produced due to subluxation or dislocation compensates pre existing axial myopia, thus the aphakic power is generally less than +10 D.

2.Iris. The iris is generally tremulous over the aphakic part. Occasionally there may be aniridia which makes diagnosis more difficult.

3.Sclera. The Sclera may be stretched and thin .May develops staphyloma due to associated buphthalmous.

4.Retina. There is high incidence of retinal detachment mostly due to myopia. However aphakic detachment is very common following lens exaction.

5.Vision. Most of the children have diminished distant vision due to:

(a) Error of refraction (b) Glaucoma

(c) Squint

(d) Amblyopia

B. The skeletal changes are

The skin is light coloured, with malarflush, the check bones are flat, and the skin is dry. The limbs are long, the fingers are spidery (arachnodactyly),

Joints are prone for subluxation. Feet are flat with floppy gait.

The spine shows kyphosis and scoliosis. Osteoporosis is common leading to fractures.

Hernia is common due to under developed abdominal muscles.

C. The mental changes consist of

Low IQ and other psycho somatic disorders are common. However some of the children may have normal intelligence.

D. Cardio vascular changes consist of

Various congenital anomalies of heart.

Thromobo embolic episodes are common leading to-cerebrovascular accidents. Myocardial infarction in early adulthood and pulmonary embolism are frequent. All these factors make these children very poor surgical risk. They have high rate of death during general anaesthesia. The child with homocystinura generally does not live beyond third decade.

E. Biochemical test43, 44

Cyanide sodium nitropruside test is a good secreting test but not conformatory due to high rate of false positive results.

The test consists of:

Adding two ml of 5% sodium cyanide to 5ml of fresh and acidified urine. This mixture is allowed to stand for ten minutes, then two to four drops of sodium nitropruside is mixed to the previous solution. This gives bright red colour which is common both to homocystine and cystine present in urine. To confirm the diagnosis of homocystinuria electrophoresis is required. Bacterial contamination of urine of normal child may also give false positive result.

F. Management

Management of homocystinuric child is more complicated due to :

(1)Associated mental changes which may hinder visual rehabilitation.

(2)Increased risk of thromboembolic phenomenon that makes them poor surgical risk.

(3)Only positive point in homocystinuria is that the condition can be helped by : (a) Restricting dietary methonine and supplementation of oral cystine42.

(b) High doses of vitamin B6 (Pyridoxine). The dose recommended is 600 mg to 1200 mg daily and folic acid orally.

(c) Those individuals not responding to pyridoxine may be put on Betaine that reverses degradation of methonine.

F.Ocular Management is similar to any other ectopia lentis.

G.Mentally retarded children may have to be put in institutions meant for mentally and visually challenged.

XVII. WEILL—MARCHESANI SYNDROME45a,45b,45c

This is the third of the three common disorders that cause ectopia lentis with systemic involvement. It is rarer than Marfan’s syndrome and homocystinuria both of which have many common features. The only common feature of Weill Marchesani syndrome with the former two is ectopia lentis.

It is an inherited disorder of mesoderm. It may have both types of inheritance i.e. autosomal dominant or recessive.

The components of the disorder are

A.Ocular

B.Non ocular

A. The Ocular features are

1. Microspherophakia where the lens is small in equatorial diameter but has greater than normal anterio posterior diameter. The shape of the lens is not apparent unless the pupil is dilated, with dilated pupil the lens has a circular bright crescent on the periphery. The zonules are visible on slit lamp examination. The lens has tendency to move anteriorly rather than upward or downward. This results into a ball and socket pupillary block. The block is enhanced by use of miotics. The spherophakia results in index myopia. Occasionally the A.C. is shallow and tremulousness of iris is better seen on the periphery. The lens may completely

dislocate in anterior chamber with its resultant complications. Posterior dislocation is less commaon.

2. Secondary pupillary block glaucoma is most troublesome complication. As the pupil constricts over the spherical lens a pupillary block results that shuts off the flow of aqueous from posterior chamber to anterior chamber, resulting in shallowing of A.C. and narrowing of angle which itself may have strands of mesodermal tissue. The tension is relived flowing maydriasis or establishing a path between A.C. and P.C. by iridectomy or laser iridotomy.

B. Non ocular signs

The non ocular signs are striking. The patients have a short stubby stature. Their maximum height seldom exceeds five feet and many are considered to be dwarfs and investigated as such. They have brachycephly, well developed subcutaneous fat, muscles are hypertrophied, arms and legs are short, the hands and feet have squarish shape, and the joints are prominent and stiff. The thorax looks larger as compared to the body. They have tendency to develop carpal tunnel syndrome. There is no fixed pattern of cardiac disorder, the children have assorted cardiac anomalies, there is no mental retardation, life expectancy is better than in homocystinuria and no specific biochemical change have been attributed to the conditions.

Management Consists of

1.Correction of error of refraction.

2.Prevention of glaucoma by doing prophylactic surgical peripheral iridectomy or laser iridotomy.

3.Management of lenticular opacity by standard microsurgical procedure.

4.Removal of dislocated lens.

Comparison between Marfan, homocystinuria and Weill-Marchesani syndrome.

result following lens extraction, same is not true with childhood cataract. Childhood cataract surgery has poorer visual prognosis and more complications.

It is estimated that congenital cataract is found roughly one in every 250 live births46 Very few have clinical symptoms, only few require treatment, incidence is higher in developing countries where hardly any prophylactic measures are taken for maternal rubella, and correction of maternal malnutrition, incidence also increases due to consanguinity47. Congenital cataract is a leading cause of blindness in children about 20% of blindness in children is due to congenital cataracts46.

In one third of the cases of cataract no cause can be detected. In developing countries trauma is a major cause of cataract in children. Congenital and developmental cataracts have a strong heredity. However sporadic cases are also common. Though most of the congenital cataracts are bilateral, many of the children present as unilateral cataract, in such cases the other eye must be examined in detail for subtle signs of cataract. Unilateral cataracts have poorer prognosis as compared to bilateral cases. Trauma and intraocular diseases are common causes of unilateral cataracts.

A. The cause of congenital cataracts can be

1.Commonest cause being maternal rubella in first trimester, other causes can be maternal diabetes, parathyroid disorder and malnutrition.

2.In another group of children, the mother is normal but the child has various errors of metabolism i.e. galactocimia, hypoglycaemia, homocystinuria and other aminoaciduria.

3.There are numerous syndromes associated with congenital cataract. Some frequent syndromes are Lowe’s syndrome, Alport’s syndrome and Turner’s syndrome.

4.Congenital cataract may be the only anomaly or else it may be associated with other maldevelopments of the eye.

5.All opacities in the lens do not cause visual disturbance and may go unnoticed till later life, only to be discovered on routine examination.

B. Symptoms of congenital and developmental cataract46, 48

Symptoms depend on

1.Position of the opacity. Visual loss is more in central cataracts than peripheral, opacity near the nodal point is likely to cause more visual disturbance than one away from it.

2.Size of the opacity. Opacities larger than normal pupil cause more visual loss. The

matter is worsened when pupil constricts in bright light or the child has moitic pupil due to any cause.

3.Number of the opacities. Scattered small opacities hardly produce any symptom but nuclear opacity with posterior capsular opacification cause more visual loss than any one of them.

4.Density of the opacities. Denser opacities cause more loss of vision than translucent opacities.

5.Unilateral cataracts. They may go unnoticed if the other eye has good vision; these eyes develop amblyopia and squint more frequently.

6.Age of on set. Congenital cataracts that are apparent before three months of age cause intractable nystagmus.

7.Associated ocular malformation. Microphthalmos, persistent hyaloid system, persistan primary hyperplastic vitreous, retrolental fibbroplasia, Reigers anomaly have poorer vision and prognosis.

8.Associated with symptoms of other systemic syndromes.

9.Physical under development is a frequent associated feature of congenital cataract.

10.Frank mental retardation is common in homocystinuria. Even children with normal IQ may fail to attain expected academic grades due to poor vision.

C. Presenting Features of Congenital and Developmental Cataract

Various age groups have different presenting features. 1. An infant may be brought with following complaints :

(a) White Reflex in pupillary area

(i) A dense opacity that fills the pupillary area is obvious even in natural light and noticed by the mother, midwife or the attending neonatologist.

(ii) Faint, Peripheral and posterior opacities are missed initially. Such an infant is brought to ophthalmonologist by parents with the suspicion that the child does not have expected vision. It is only with the dilation of pupil the cataract becomes obvious.

(b) The child is brought with nystagmus or squint.

(c) There is positive history of developmental cataract in the family, so the child is brought to get it excluded.

2.Older Children are brought with white reflex, nystagmus that dates back to first three months, squint or diminished vision in various combinations.

3.Some children are brought with glare. The child with unilateral cases may close the effected eye to wardoff the glare.

4.Congenital cataract per se does not cause pain, photo phobia or redness of eye. If these symptome are present the child should be investigated for retinoblastoma.

5.Sick children who fail to thrive are likely to have metabolic cataract or rubella cataract.

6.Unilateral cataracts are detected late because the child carries out his routine with better vision in the other eye. They are fist brought with squint. Unilateral dense cataracts draw attention earlier than posterior cortical and posterior polar cataracts.

7.Some of the children are referred by paediatricians who have diagnosed a syndrome that is likely to have cataract.

UNILATERAL CATARACT

Unilateral congenital and developmental cataracts are unique in many ways:

A.30% of idiopathic congenital and developmental cataracts are unilateral.

B.Some of the heredity cataracts are also unilateral.

C.Children with unilateral cataract seek medical help later than bilateral cases. Generally they are brought with strabismus.

D.In case of obvious cataract in one eye the other eye should be examined for of subtle signs of cataract.

E.All cases of uniocular cataract should be examined in details for evidence of occult or forgotten trauma, uveitis, retinal detachment etc.

F.Post operative visual prognosis in unilateral congenital or developmental cataract is always poorer than bilateral cases.

G.Unilateral traumatic cataracts have better vision following cataract surgery than congenital and developmental cataract.

H.The purpose of operating unilateral cataract is to improve vision even when it is known that there are no chances of improvement of central vision following successful surgery, the lens should be removed to improve peripheral field on that side.

I.Developmental cataracts that have relatively clear lens for first few years like posterior lenticonous have good visual prognosis.

J.All cases of unilateral congenital and developmental cataracts should be encouraged to have P.C.I.O.L than conventional extra capsular cataract operation49 with spectacle or contact lens.

WORK UP IN A CASE OF PAEDIATRIC CATARACT

A.Eyes of all new born children should be examined routinely by attending obstetrician, neonatologist for evidence of dense lenticular opacity. The traditional midwives and nurses can be taught to screen neonates for lenticular opacities.

B.All neonates who have hepato spleenomegaly, abnormal heart sound and fail to thrive should be examined for possibility of galactocemia, rubella and toxoplasmosis. Urine examination for reducing substance will exclude galactosaemia while torch test28 is helpful for rubella and toxoplasmosis. Galactokinase deficiency is seen in otherwise healthy children with congenital cataract.

C.Positive family history of developmental cataract in parents, siblings and first cousins should alert the physician for possibility of lamellar cataract.

D.All white reflexes in pupillary area in children are not congenital cataracts.

Cataract should not be confused with retinoblastoma and vice versa. It should be kept in mind that all non lenticular opacities need not be retinoblastomas. (See differential diagnosis of white reflex in pupillary area.)

E.Examination of an eye with congenital cataract

1. As infants can not be examined on usual slit lamp they should be examined either with hand held slit lamp or under operating microscope. In absence of these an examination with uniocular loupe with a bright torch is good enough. Binocular loupes give very low magnification.