Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

CONGENITAL ANOMALIES OF THE GLOBE8,9,10

The Congenital anomalies of globe are caused due to faulty embryogeneses before the closure of the embryonic fissure. They can happen :

A.During formation and development of primary optic vesicle i.e. Cyclopia, anophthalmos, and extreme degree of microphthalmos.

B.During development of optic cup i.e. Congenital cystic eye ball, colobomatous cyst and typical coloboma of eye. (Uvea, retina disc.)

C.Maldevelopment of formed eye is Microphthalmos (True nanophthalmos)

1. Cyclopia. This is an extremely rare congenial anomaly that has either a single mid line eye or two developing eyes with deformity of the forebrain and multiple anomalies of mid line. There is either one orbit or two maldeveloped fused orbits. There is one palpebral fissure with two rudimentary lids, and lacrimal apparatus. The IPA is wide, the lids do not close, the rudimentary cornea and conjunctiva are exposed. These children have neonatal death.

2. Anophthalmos. Strictly speaking term anophthalmos is reserved for a condition where no ocular tissue is present in the orbit due to non formation of optic vesicle. However in clinical practice eye with minimal ocular tissues are also called clinical anophthalmos. Generally these eyes do not have any evidence of formed globe. They are also known as extreme microphthalmos. Anophthalmos differs from enophthalmos. In enophthalmos a fully developed globe is pushed back in the orbit due to secondary causes.

3. Microphthalmos. These include all eyes that have size less than normal eye due to congenital cause. They can be unilateral or bilateral. In bilateral cases both eyes are smaller than normal but not of equal size. The defects in one eye need not be the same in other eye. In unilateral cases the other eye may be normal and remain so for rest of the life.

Microphthalmos has been divided in following groups more on clinical features rather than embryological.

(a) Pure microphthalmos (Nanophthalmos) (b) Colobomatous microphthalmos.

(c) Complicated microphthalmos. (d) Microphthalmos with cyst.

(e) Microphthalmos associated with systemic syndromes.

(a) Nanophthalmos11,12 (pure microphthalmos). Nanophthalmos is a rare congenital condition where a fully developed eye fails to grow like any other eye. This is caused due to failed growth after the embryonic fissure has closed from end to end. There are no colobomas present in the globe, it occupies normal position in the orbit, has normal movement but may be strabismic due to associated high axial hypermetropia. The cornea is smaller, AC is shallow. The sclera is thickened and the vertex veins are narrow11. There is pseudoneuritis, hypoplasia of macula, nystagmus, amblyopia. There are various types of glaucoma i.e. late onset of simple glaucoma, narrow angle glaucoma, precipitation of glaucoma following mydriasis13. These children require high hyper meteoric correction may require near correction. They have been described as phakia children with aphakic correction. The nanophthalmic eyes with glaucoma do not respond well either to medical or surgical treatment, the later is generally

associated with Chroroideal effusion syndrome13 that may follow any intra ocular surgery or injury to the globe.

(b) Colobomatous microphthalmos. colobomatous microphthalmos is a congenitally small eye that have associated failure of embryonic fissure. These eyes have multiple colobomatous defects at the site of fusion of embryonal fissure, mostly in uvea and or retina. These eyes are small in all dimensions, the coloboma may range from a small notch in iris to coloboma extending up to optic nerve.

(c) Complicated microphthalmos. Is a term used to denote a congenitally small eye that develops cataract, iridocorneal defects, defects in iris, retina and vitreous. These are due to

(i) Failure of development of primary optic vesicle.

(ii) Arrest of development after the primary optic vesicle has formed.

(d) Microphthalmos with cyst. In case only retinal tissue protrudes through the embryonic cleft a cystic eye ball with coloboma results. The colobomatous cyst may have an almost normal eye with a small indistinguishable cyst or the cyst may be so large that the small eye is not visible. In between are the cases where a formed eye is associated with colobomatous cyst.

(e) Microphthalmos associated with various syndromes. There is a long list of conditions that are associated with microphthalmos most of which are cranio facial or mandibulo facial anomalies.

BUPHTHALMOS

This condition is just reverse of microphthalmos it is a large eye associated with various types of congenital glaucoma.

DEVELOPMENT OF OCULAR STRUCTURE FORM EMBRYONIC GERMLAYER

1.The eye along with its adnex develop from ectoderm and mesoderm. The Bruch’s membrane and the tertiary vitreous (zonule) have duel origin. Bruchs membrane develops from neural ectoderm and mesoderm. While zonules develop from surface ectoderm and mesoderm. No part of the eye or its adnexa develop from endoderm.

2.The surface ectoderm gives rise to :

A.The Lens

B.Corneal Epithelium

C.Epithelium of all the ocular adnexa i.e. conjunctiva, meibomian gland, glands of Zies and Moll, lacrimal gland, lacrimal passage.

3. The neural ectoderm gives rise to

Sensory retina, retinal pigment epithelium, epithelium of ciliary body, pigment epithelium of iris, sphinter and dilator muscle of iris, melanoeytes, neural part of optic nerve.

4. The Mesoderm gives rise to :

A.Corneal stroma and endothelium of cornea.

B.Iris stroma, ciliary muscles and chroid

C.Sclera, vitreous and extra ocular muscles.

D.Bony orbit

E.Blood vessels.

REFERENCES

1.Duke Elder.S. ; System of Ophthalmology, Vol-III, Part-I, First edition, Henry Kimpton, London, 1964.

2.Mann Ida ; Development of Human Eye, Third Edition, British Medical Association, London, 1964.

3.Barber A.N. ; Embryology of Human Eye, The C.V. Mosby St. Louis 1955.

4.Kozart D.M. ; Embryology of the human Eye in Text Book of Ophthalmology, Ninth Edition p79-92, Edited by Schcie H.G., and Albert D.M., W.B. Saunders Company, London, 1977.

5.Vaughan D and Asbury T. ; General ophthalmology, Ninth Edition p9-13, Lange medical publication, California 1980.

6.Hamming Nancy and Apple D. ; Anatomy and embryology of the eye in Principles and Practice of Ophthalmology, Vol-I, p3-20, First Indian edition. Edited by Peyman G.A., Sander D.R. and Goldberg M.F. Jay. Pee Brothers, New Delhi, 1987.

7.Buffam F.V. ; Lacrimal diseases in Text book of ophthalmology, Vol-4, Edited by Podos S.M. p7.1 to 7.3, Gower Medical Publication, London 1993.

8.Nema H.V. Singh V.D and Nema N. ; Congenital anomalies of the eye and its adnexa in Anatomy of the Eye and its Adnexa. Second edition. p162-165, Jay Pee Brothers, New Delhi 1991.

9.Duke Elder.S. ; System of Ophthalmology, Vol-III, Part-2, First Edition p415-495, Henry Kimpton London,1964.

10. Schaffer D.B. ; Abnormalities of the eye as a whole in Text Book of Ophthalmology Ninth Edition., p209-293, Edited by Scheie H.G. and Albert D.M., W.B. Saundes Company, Philaddphia 1977.

11.Dutta L.C. ; Uveal effusion syndrome in Ophthalmology, First Edition p-122-123 Current Books International, Kolkota 1995.

12.Shields M.B. ; Nanophthalmos in Text Book of Glaucoma, Fourth Edition, p-280, William and Wilkins Philadelphia 1999.

A. Intra uterine

The intra uterine ocular disorders produce mild to sever deformity and visual loss, are generally bilateral, many of them are genetic in nature. Some of them are life threatening.

Intra uterine factors that produce ocular malformation can be:

1.Genetic

2.Transplacental.

3.Mechanical.

4.Traumatic

5.Neoplastic (rare).

6.Nutritionational.

The genetic factors can be: (a) Inherited genetic defect. (b) Genetic mutation.

(c) Chromosomal aberration.

(d) Effect of exogenous factors like, drugs, radiation, diet.

The transplacental factors causing ocular defects are mostly infection, followed by various drugs taken in first trimester. In developing countries dietary deficiencies have a considerable influence on ocular organogenesis.

The common infections that cause ocular morbidly are Rubella, toxoplasmosis, syphilis, cytomegalo virus diseases.

Uterine bands, deformed uterus, fibroids and umbilical cord are common mechanical causes of ocular deformity.

Intra uterine traumas in the form of amniocentesis, attempted abortion in early pregnancy also cause ocular disorders.

NEONATAL CAUSES OF OCULAR DISORDERS CAN BE

A.Infection.

B.Mal developmental.

C.Effect of pre maturity .

The infection can be acquired during delivery or soon after. The after effects of such infection may cause ocular morbidity which may be noticed later. The same is true of congenital infections. These infections are gonorrhoea, herpes simplex, chlamydia, inclusion conjunctivitis and other bacterial infections. The congenital infections that cause ocular morbidity but do not manifest always at birth are rubella, toxoplasmosis and syphilis.

Maldevelopmental causes of ocular disorders are varied, they can involve a single structure or may involve more than one structure in various combinations themselves or their aftermath common among them are.

Anophthalmos, microphthalmos, microcornea, limbal dermoids, bluesclera, dysgenesis of anterior chamber, coloboma of uvea, polycoria, aniridia, total or partial

EXAMINATION OF EYES IN NEW BORN

Before embarking on examination of eyes of neonate it is essential to remember features of new born eye.

The new born eyes as sensory system are better developed than expected when weighed against its size. The eyes are smaller in size as compared to that of adults. The eye ball of a new born is 16.5 mm to 17.5mm in diameter as compared to 23 to 24mm of an adult eye. The volume of eye ball is 2.8 mm as compared 7.0 mm of adult, the eye reaches its adults size by 14 years of age. By the age of 3 years the eye is about 23 mm in diameters, contrary to general believe there is no spurt in axial length of an emmetropic eye at puberty.

The normal eye at birth has axial hypermetropia of about 3 to 4 D this is neutralised by physiological increase in axial length however if the axial length continues to increase two things are possible

1.Parts of this in neutralised by reduction of curvature mostly of lens and partly of

cornea4.

2.The eye becomes myopic.

A.The Vision. The vision of a new born is less as compared to a child of three years but is not very poor, it has been estimated to be about 1/607 the new born child has good accommodation, however there is no clinical method to measure accommodation and convergence. The fixation reflex is present but poor.

B.The movements of the eyes are bizarre; they can fix a strong stimulus for a short while and then give up. Movement of two eyes are independent and non conjugate.

C.The inter palpebral fissures are 18 mm in length, the width is less as compared to cornea hence the cornea looks larger and may be mistaken as abnormal. The new born sleeps for almost 18 hours a day so most of the time the eyes are closed. Any attempt to widen the IPA results is contraction of orbicularis and rolling up of eye ball due to Bells phenomenon which is well developed. However the blink mechanism is absent and develops by 7th or 8th week. Hence threatening gesture to find out presence or absence or vision is futile. it is difficult to evert the lids.

D.The orbits are smaller, shallower and round. The space between the globe and orbital wall is so less that the orbit seems to sit snugly round the globe. None the orbital contents are visible or palpable.

E.The Cornea is relatively large when compared to adult cornea. The diameter of new born cornea is 10.5 mm while that of adult cornea is little less than 12mm. However this growth is far less when compared to axial length of the globe which grows from 18mm at birth to 24mm at maturity. As the IPA is narrow in new born there is a false impression of cornea being large. The cornea is flatter when examined on kertometer. Its curvature is uniform, giving spherical look to the cornea. The Cornea has mild haze that clears within few days.

F.The Sclera is thin the under lying uvea shines through it so it has a bluish tinge that passes off within few month and sclera becomes white.

G.The Conjunctiva is well developed, the goblet cells are functioning, the conjunctiva is sterile at birth that gets contaminated within few days. The newly acquired organisms are generally non pathological.

H.The Lacrimal Glands are not fully developed at birth. It takes three to four years for them to adequately develop. The new born cries but does not weep; this is due to lack of reflex tearing that develops after four to six weeks. Psychic tearing takes about six to seven months to develop.

I.The Lacrimal Sac is fully developed at birth and its lumen is patent .

J.The Lacrimal Passages are canalised at birth. Even if the nasolacrimal duct is not patent at birth its block is not evident till end of first month as there is no reflex tearing before that.

K.The anterior chamber is fully formed. Its depth is normal or slightly less than adult depth. The contents are clear, the angle is wide. The pupil can be safely dilated without rise of IOP.

L.The pupil is smaller than adult, is shifted nasally and down. It is circular and reacts to bright light both directly and indirectly.

M.Accommodation and Convergence can not be tested clinically due to lack of fixation. Accommodation is well developed by 4 months.17

N.The iris is light coloured due to scanty pigments. There may be a few blood vessels on the iris surface.. The dilator muscles are poorly developed. The constrictor muscles are relatively stronger hence it is difficult to dilate the pupil.

O.The Lens is fully developed and functional. The lens grows in size throughout the life. The lens is more spherical than adult lens, its average diameter is 6mm in comparison to 9mm of an adult lens.

P.The fundus The fundus is visible, the colour is paler than normal, the optic disc is pale, the macula is not fully developed, it continues to grow postnatal. The foveal reflex is absent. The retinal periphery is also pale.

Q.The broader nose bridge of a new born gives an appearance of pseudo convergent squint. The movements are not co-ordinated and can not be tested precisely.

EXAMINATION OF THE EYES OF NEONATES AND INFANTS

Examination of the eyes of a neonate is difficult because a neonate sleeps almost eighteen hours of a day the waking period is in short spells and most irregular, a neonate wakes only when hungry or is ill at ease.

It is difficult to elicit correct visual response in an infant.

The examiner should be able to differentiate normal parameters of signs from the abnormals. Many a times a casual remark by the examiner may send a wave of panic in the parents least the baby may be blind.

An infants eyes are required to be examined under following circumstances

A. As a part of routine examination of all new borns. The protocols followed in various hospitals differ greatly. The examination is done either by attending neonatologist or resident of pediatric ophthalmology posted in nursery and well baby clinic. Nurses and midwives attending neonates can also be taught to examine a neonate’s eyes and refer for further examination for abnormal findings, or seemingly abnormal cases.

B.The neonatiologist has noticed some gross abnormality i.e. craniofacialdysostosis, faciomandibular abnormality, cryptophthalmos, anophthalmos, microphthalmos, large coloboma of the lid, proptosis, unilateral gross ptosis, corneal haze, pupillary abnormalities white reflex in the pupil and refers for detail examination and opinion.

C.Signs of infection in the eyes : Edema of lids, purulent or mucopurulent discharge. The above abnormalities are gross enough to be noticed by parents or even a village midwife.

D.There is

1.Family history of

(a) Lamellar cataract (b) Albinism

(c) Nystagmus

2.Maternal history of

(a) Suspected rubella in first trimester (b) S.T.D.

(c) Some drugs given in the first trimester that cause congenital anomalies. (d) Diabetes under treatment.

(e) Myasthenia in mother (f) Consanguinity

(g) Prematurity

(h) These babies may or may not have been on prolonged oxygen.

(i) Difficult labour fetal distress, neonatal apnoea, intensive resuscitation for above causes, birth trauma, specially injury by forceps.

(j) A critically ill child who may have congenital toxoplasmosis, herpes simplex galactosemia, hypoglycaemia.

VISION TESTING IN A NEW BORN

One of most difficult tasks in ophthalmology is to give opinion regarding exact quantitative vision present in each eye of a new born. A rough estimation of qualitative vision present is not difficult to express.

Vision of a new born is very poor in comparison to adult vision that is attainedby seven to eight year in other wise normal eye in a healthy child.

The vision of neonate improves very fast6 from 1/60 to 2/60 at 1 month and 6/60 at four months. With 1/60 vision the child is able to fix a face moving within one meter. These visual standards are based on various complicated methods by expensive instruments on small samples i.e. Optokinetic target, Catford drum test, visual evoked occipital potential

(VEP) and forced choice preferential looking (F.P.L)7,8

Definite fixation reflex and following reflexes take about six weeks to develop before that an infant may fix for few seconds and give up. These are associated with bizarre movements,

these movements disappear with development of clear fixation. More than one types of movements are common in between the fixations.

It is said that most suitable infant to examine for vision is an awake, alter and hungry baby.

Visual acuity in a new born is determined by optically elicited movements.

A.The first step is to observe if the child tries to look and fix a light when switched on in a semidarkned room. This must be repeated several times least some of the bizarre movements may be mistaken for fixation. Each eye should be tested separately. This indicates most primitive form of vision that can be elicited clinically.

B.Next step is ability of the child to fix and follow the face of the examiner when brought within the field of vision of the child with both eyes open. This gives a definite clue of vision being present in at least in one eye but can not indicate which eye. For that one eye is closed, and other examined, both eyes are examined in the similar way separately one after the other.

The incidence of blindness in neonates is very low if, visible causes are excluded.

C. The condition that result in bilateral sub normal vision can be

1.Ocular

2.Systemic

The Ocular causes consist of (a) Persistent corneal haze (b) Complete cataract

(c) Congenital glaucoma (d) Retino blastoma

(e) Aniridia

(f) Hypoplasia of optic nerve (g) Sever retinal degeneration (h) Albinism

(i) Achromatopsia.

(j) Recessive opticatrophy (k) Leber’s amaurosis.

(l) Tay’sachs disease. (m) Glioma of chiasma

The systemic causes are seen in (a) Premature children

(b) Full term with low birth weight (c) Foetal distress

(d) Asphyxiated child

(e) Birth trauma to occipital cortex