Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

Management28,29

There is neither prophylaxis nor specific treatment for the condition. The aim is to clinch the correct diagnosis. The treatment is directed towards vascular changes mostly on the peripheral telengectasis.

This is achieved by

1.Photo coagulation—This is a preferred treatment. The leaking vessels are treated directly by laser. This may initially increase exudation, which can be reduced by using lesser energy and smaller spots. The preferred laser is argon laser. It takes about six weeks for any improvement to be visible and takes months or years for the exudation to clear.

2.Cryo therapy—The cryo is applied through trans conjunctival route on the periphery and reaction monitored under indirect ophthalmoscope.

3.If retina is elevated, a scleral buckle may be required.

Recurrence after adequate treatment are known.

Retinal angiomatosis (von Hippel Lindau disease)

The angioma formed in this condition is a hamartoma, which comes under broad classification of phacomatosis. The lesion develops from retinal capillaries and endothelium of retinal vessels. In contrast to Coats disease, which is non inherited, this condition is inherited as autosomal dominant trait. It again differs from Coat’s disease due to multi systemic involvement that can be intracranial or visceral.

In fifty percent of cases it is bilateral which is less frequent in Coat’s disease. It can be seen on optic nerve head as well. It may be present in the members of the same family without any symptoms. The condition is most commonly detected in teens or early twenties. Both the sexes are equally affected.

The lesion starts on the periphery either as single or multiple lesions, all lesions need not appear simultaneously. The first change occurs in the capillary bed as micro aneurysm that gradually enlarges to become a small nodule. The final growth is a spherical orange nodule, may be larger than the disc. The nodule has a feeding artery and a draining vein. The calibre and the colour of both the feeding and draining vessels become identical with passage of time.30

The angioma on the optic nerve is generally not associated with abnormal vessels. The systemic involvement is seen in about 25% of cases. The systemic involvement becomes symptomatic later than ocular. It is not always possible to predict which child with angiomatosis retinae will have systemic involvement. Hence all cases should be subjected to neurological and systemic examination including USG for visceral lesions, CT and MRI for brain lesion. The parts of the brain involved are—Cerebellum, medulla and pons. The spinal cord may also be involved. Commonest cerebellar growth is hemangio blastoma.

The visceral involvement consists of cyst in liver, lung, kidney, pancreas, cpididymis and ovaries may also be involved. The skin is never involved, which is common in other vascular hamartomas. Rare systemic involvement consists of polycythemia, hypernephroma and pheo chromocytoma.

The clinical pictures are variable.

The retinal lesion may be dormant for years and become symptomatic when there is exudation under the macular which may form a macular star. In absence of macular involvement, the other causes of diminished vision are retinal detachment, retinal and vitreous haemorrhage, secondary glaucoma and complicated cataract.

Management

Treatment of choice is Laser photo coagulation of lesions smaller than optic nerve. Xenon arc photo-coagulation gives better result in larger angiomas. Small lesion are treated in single sitting, larger growth require multiple sittings. The aim should be to destroy the growth directly and not the feeding or draining vessels. Peripheral lesions are difficult to treat with laser. They are best treated by cryo coagulation.

Retinal cavernous haemangiomas

These are rarer than angiomatosis retinae. They are also hamartomas, may be seen in the retina or optic nerve head. The condition is also included in group of phacomas. Skin involvement is frequent. The condition is asymptomatic, does not require any treatment. However the patient should have regular follow up.

Arterio venous aneurysm

The condition is known by many other names but none of them are appropriate because the lesions are neither aneurysm, talengiectasis or angioma, though sometimes they may resemble one of them. It is a congenital malformation of the main retinal vessels, which have end to end anastomosis without capillary bed in between. Generally there are no systemic involvement. Rarely brain especially the mid-brain may have similar changes with corresponding neuro vascular presentation. Involvement of brain is called Wyburn-Mason syndrome. Occasionally facial bones may be involved.

Common age when the diagnosis is made is generally in the third decade. However it is not uncommon to see the condition in first decade. It is equally seen in both sexes. On examination the patient is generally asymptomatic but on a long run due to retinal exudation there is diminished vision. The anterior segment is normal. The fundus picture is characteristic, best seen by indirect ophthalmoscope. The veins and arteries are of same colour and calibre. It is difficult to find out the line of demarcation between the two. There may be some retinal exudation and haemorrhages. Fluorescein angiogram differentiates it from other angiomas. Initially the sensory retina is not involved. In well established cases micro-aneurysms and capillary non perfusion may be seen. Generally there is no leak. A few cases may regress without any treatment. There is no specific treatment. Rarely photo coagulation with laser may be required in selected cases.

Congenital anomalies of the macula

The development of the macula differs from rest of the retina. It starts differentiating early during embryogenesis, there is a period or retardation followed by growth that lasts in post natal period. The macula gets its blood supply mostly from the underlying chorio capillaries. It is almost exclusively packed with cones hence is the seat of central vision and colour vision. Congenital anomalies may start in early days of gestation or the anomaly may start late and be discovered late.

Commonest congenital anomaly of macula are macular colobomas. They are frequent but not as common as coloboma of the uvea. They can be unilateral or bilateral and single, or multiple, generally asymmetric coloboma is generally elliptical, are placed horizontally over the macula and extending well beyond the macula. It’s size may vary between one disc diameter to ten disc diameter. The edges are generally irregular with uveal pigments. As per appearance of the coloboma it has been classified into following groups -

(a) With normal retinal vessels (b) With abnormal retinal vessels

The second possible classification is (a) Coloboma with pigment

(b) Without pigment

Both the two groups may overlap.

The pigmented coloboma has heaped pigment. The retinal vessels course over the mound of pigment. The chorio capillaries under the macula are absent.

Non pigmented coloboma—These are more common. The area is white due to underlying sclera that may be ectatic, there are no vessels seen in the coloboma. On the periphery, which is irregular, clumps of pigmentation are seen.

Coloboma with abnormal vessels—This type of coloboma is rarest. There may be anastomosis between the choroidal and retinal circulation or a vessel may pass from the coloboma towards the vitreous.

The macular coloboma has a strong hereditary predisposition. The coloboma may be associated with anomalies of the globe, optic disc or choroid.

The exact etiology is not understood. It is said to be a variation of an atypical coloboma of the uvea. This theory is supported by absence of chorio capillaries and presence of retinal vessels in the coloboma. This further gets credence due to extension of vessels from the coloboma into the vitreous. However possibility of maternal toxoplasmosis should always be kept in mind.

Common clinical presentations are—Diminished central vision, nystagmus, myopia, convergent squint.

Hypoplasia of the macula—Some authors consider it as variation of coloboma23. It is generally associated with albinism but can be a primary defect. The exact mechanism is not known. These children have poor vision with absent foveal reflex.

Other congenital anomalies of macula consist of degeneration of macula.

Retinal diseases in children

Retinal diseases in children can be

1.Congenital

2.Acquired

Out of all the acquired conditions, the most common group of diseases in children are the retinal dystrophies and degeneration’s. The sequelae of which spill over adulthood and may terminate in legal blindness in adulthood. In contrast to this vascular retinopathies

which are a major cause of blindness in adults are less frequent in childhood. Some of them may be seen in childhood in milder form. One of the unique condition that is seen in children is retinoblastoma, a life threatening malignant tumour (It has been discussed in a separate chapter). Rhegmatogenous detachment is also less common in childhood but when present, is a potential cause of blindness if not treated. Trauma and myopia are two common causes of retinal detachment in children.

The acquired causes can be

1.Inflammation

2.Trauma

3.Degeneration

4.Retinopathies

5.Tumours

6.Retinal detachment.

Symptoms of retinal diseases in the children

The symptoms hardly differ from those in adults. The difficulty arises when the child can not express it or fails to realise its importance. This is more so because all retinal diseases per se are painless.

The symptoms

1.Vision. Commonest symptom is diminished vision. Degree of diminished vision depends on extent of the macular involvement. A large lesion on the periphery may not produce any dimness of vision, a small lesion on the macula produces extensive loss of vision. Macular lesions are more likely to produce sudden loss of vision except in degenerations and dystrophies.

2.Diminished night vision is foremost cause of retinal dystrophies which is gradual, progressive and associated with poor dark adaptation.

3.Loss of peripheral field again is a symptom of retinal dystrophies.

4.Metamorphopsia is common in retinal detachment and acute macular lesions.

5.Photopsia or flashes of light generally indicate retinal irritation or beginning of retinal or vitreous detachment.

6.Black spots in front of the eyes—Sudden development of black spots, increase in number and size of black spots in front of eyes require elaborate examination because they may herald retinal detachment. Slowly developing black spots are not harmful.

7.Colour defect may be present in macular degeneration.

Signs of retinal diseases

The signs of retinal diseases are generally not visible with oblique illumination or routine slit lamp bimicroscopy because the retina is beyond the focus of ordinary slit lamp. The optics of the eye/slit lamp needs to be modified to bring the retina in focus of the slit lamp. Rarely the condition is visible by oblique illumination if it is large enough or near enough the lens as white reflex in the pupillary area.

The retina is best examined by

1.Direct ophthalmoscopy

2.Indirect ophthalmoscopy

3.Slit lamp biomicroscope with minus contact lens - Goldmann three mirror contact lens

Non contact lens

(a) Minus lens—Hruby lens

(b) Plus lens—Volk, El-Bayadi lens

4.Retinoscopy for error of refraction, retinoscopy shows coloboma, large exudate, edema growth, detachment as grey reflex.

5.Fluorescein angiography

6.Ultrasonography, A Scan, B Scan

7.OCT (Optical Coherence Tomography)

8.Dark adaptometry

9.Photo stress test

10.Field examination

(a) Central 10°

(b) Central 30° Peripheral (i) Kinetic

(ii) Static

11. Electro physiological tests

(a) Electro oculography (EOG) (b) Electro retinography (ERG) (c) Visual evoked response (VER)

12.X-ray skull, orbit

13.CT

14.MRI

15.Trans-illumination.

Principles of some of the methods used in examination of retina Direct ophthalmoscope

This instrument uses the optics of the eye as simple magnifier of + 60D, the retina acts as the object. The ophthalmoscope acts partly as source of light to illuminate the retina and partly to focus the image of the retina. This gives a virtual image of the retina which is erect and fifteen times magnified in emmetropia. The magnification is less when the diopteric power of the eye is less i.e. aphakia or high hypermetropia where a small image is seen. In contrast to this, the myopic eye gives a larger image than emmetropia. A raised lesion on the retina or in front of the retinal plane requires addition of plus lenses in the viewing system of the ophthalmoscope. Similarly minus lenses are required to see a spot behind the retinal plane

i.e. floor of optic cup in glaucoma or floor of posterior staphyloma. The direct ophthalmoscope has a small field i.e. 10° at a time, which requires to be shifted frequently to see a peripheral lesion, retina beyond equator is not visible, scleral indentation which makes peripheral lesion visible by indirect ophthalmoscopy is not possible while using direct ophthalmoscope. The illumination of direct ophthalmoscope is not very bright. The direct ophthalmoscope lacks stereopsis. Its higher magnification is better suited for small lesions of macula and examination of optic nerve head by incorporating a grid, the size of a lesion can be measured by direct ophthalmoscope.

Indirect ophthalmoscope

The condensing lens of the indirect ophthalmoscope forms an inverted, real and magnified image of the retina between the condensing lens and the observer. The indirect ophthalmoscope uses the principle of astronomical telescope where both the eye pieces and the object are plus lenses. The indirect ophthalmoscope has a stereopsis and a large field, the condensing lens commonly used are + 15D, + 20D and + 30D. Commonly used condensing lens is a plano convex large + 20 lens which has anti reflection coating. More is the dioptre of the condensing lens, lesser is the magnification and wider the field. A condensing lens of + 15 gives magnification of 4x while that of + 20 and + 30 give magnification 3x and 2x respectively. Most commonly used indirect ophthalmoscope is binocular indirect ophthalmoscope which has head held viewing system and a hand held condensing lens.

Biomicroscopy of the posterior segment (Slit lamp examination of the retina)

Slit lamp is a compound microscope with a limited focal length. It is a versatile instrument to examine the anterior segment up to anterior few millimetres of the vitreous, structures beyond this are out of focus. To see the objects deeper to this, it is essential to modify the optics of the eye suitably. A normal emmetropic eye has a dioptric power of + 60, out of this about + 45D- + 47D is attributed to cornea and rest to the lens.

The optics can be modified either by

1.Neutralising the power of + 60D by a – 60D lens kept away from the eye i.e. Hruby lens which is placed 10 mm to 12 mm in front of the eye under examination. The pupil should be well dilated. This forms a virtual image 18mm in front of the retina. The biomicroscope is focussed on this, one of the disadvantages of Hruby lens is that the size of the pupil is reduced by high minus glass, this hampers the field of examination.

2.Replacing the corneal power by an afocal lens in contact with the cornea as by Goldmann three mirror gonioscope by which not only the posterior pole of retina, but also peripheral retinal and angle of anterior chamber can be examined. This has a disadvantage of being large and heavy. This is avoided by use of Koeppe lens which is light but focuses only the posterior poles. It is good for examination of macula and optic nerve head. The size of pupil is also reduced by these contact lenses and it reduces the field to 20°.

3.Using principle of indirect ophthalmoscopy with slit lamp. Plus lenses between

+60 to + 90 are held in front of the eye with a dilated pupil and image is seen through the slit lamp. The image is real, inverted and of same size. The image is away from

the observers eye. Stronger the power of the lens lesser is the size of the image, with pan fundic lens which is self illuminating, the magnification is 0.7x.

Fundus fluorescein angiography

This is one of the most important procedures in all retinal and choroidal disorders especially involving the retinal vessels, the retinal pigment epithelium, chorio capillaries and

Bruch’s membrane. Fluorescein angiography is less required in children than in adults where diabetic retinopathy, retino phlebitis, central vein thrombosis are main indication. In children it is mostly used in congenital anomalies of the retinal blood vessels, sickle cell retinopathy, retrolental fibroplasia, haemangiomas.

Fluorescein is a dye that when exposed to light of short wave length gives fluorescence and becomes visible. Intra vascular fluorescein is not visible in white light. To make it visible it should be excited by blue light in the wave length of 490 nm. This excitement of fluorescein then emits a yellow grey light in the wave length of 530 nm which can be recorded on a fundus camera.

For this purpose, the fundus camera which is essential part of fundus fluorescein angiography has two filters:

(1) A blue excitation filter and (2) Yellow grey barrier filter.

70-85% of fluorescein when injected in ante cubital vein gets bound to the serum protein and is called bound fluorescein, remaining part is called free fluorescein.

Free and bound fluorescein differs from each other by virtue of their ability to pass across the cells, RPE and Bruch’s membrane.

Neither free nor bound fluorescein can pass through the walls of large choroidal vessels. They also do not pass through tight junction of retinal capillary endothelium. A leak from retinal capillary is abnormal.

Free fluorescein can pass through fenestrated walls of the chorio capillaries. It can also pass across the Bruch’s membrane. It can escape into extra vascular space as well. Free fluorescein does not pass through tightly placed RPE.

Fluorescein injected in ante cubital vein reaches the systemic circulation. It reaches the fundus by two routes:

1.Short posterior ciliary arteries. This reaches the choroid earlier than the central retinal artery.

2.Central retinal artery. This delineates the retinal vessels. The dye drains by central retinal veins.

The normal fundus fluorescein angiogram has following phases:

1.Pre arterial (Choroidal) phase. The whole of the choroid gives a bright glow under six seconds. Brightness of the glow depends on amount of pigment present in the RPE. A cilio retinal artery when present stands out in choroidal phases.

2.Arterial phase. It takes about 8 seconds for the retinal arteries to fill up. The superior and inferior branches fill early, then the rest of the retinal vascular pattern stand out brightly.

3.Arterio venous phase. This indicates beginning of venous drainage. The dye is visible in both arteries and veins. The retinal capillaries become visible.

4.Venous phase. It is divided into three distinct phase i.e. early, mid and late phase.

Early venous phase. The fluorescein stains the peripheral part of the venous blood. This is attributed to the lower pressure in the veins. The arteries still show fluorescein in them.

Mid venous phase. The lamellar appearance of the dye is no more visible. The whole of the vein is uniformly filled with fluorescein. The arteries still retain some stain. The capillaries become visible.

Late venous phase. Fluorescence in the vein is less than mid venous phase. This is followed by an increased fluorescence of short period due to recirculation of the dye. Then the dye fades away.

Appearance of normal macula in fluorescein angiogram

The macula is avascular, more so in foveal avascular zone. Presence of xanthophyll, tall and more pigmented RPE masks the choroidal flush in early phase. Otherwise also a small area of central macula remains hypo fluorescent. The peri foveal arcade is seen in the venous phase.

The optic disc. Fluorescence in the vessels of the optic nerve head show variations in various phases due to difference in blood supply in different depth of the optic nerve. The capillaries at the level of lamina are visible in choroidal phase. The capillaries on the surface of the disc and peri papillary capillaries are seen after the choroidal flush. In late venous phase there is staining of optic nerve head. Fundus fluorescein angiogram helps to differentiate between pseudo neuritis, neuritis and papilledema.

Abnormal fluorescence

The two types of abnormality of fluorescein are—Hyper fluorescence and hypo fluorescence.

Hyper fluorescence is a state of enhanced fluorescence, this can be localised or generalised. The hyper fluorescent area stands out more prominently than the surrounding area. The causes are—Abnormality in the vessels, telangiectasis, aneurysms, shunts, neovascularisation, chorio retinal scar, ARMD (not seen in children), myopic degeneration, choroidal rupture.

New growth—Various hamartomas, angiomatosis retinea, retinoblastoma, malignant melanoma (not seen in children).

Increased transmission—Albinism (there is lack of pigment in RPE). Window defect—Atrophic RPE, angioid streak, drusen.

Leak—Pooling—Seen in late venous phase—RPE detachment, retinal detachment, cystoid macular edema, central serous retinopathy.

Staining—Drusen, soft exudate, scar.

Hypo fluorescence—This is a state of fluorescence that is either less than normal fluorescence or is totally absent.

It can be brought about either by masking of fluorescence or due to filling defect.

Masked (blocked) fluorescence can be due to pigment, exudate or serous fluid. The pigments are—Melanin, lipofuscin and xanthophyll.

Blood is a common cause of blocked fluorescence. It could be a haemorrhage in the choroid, retina. Both hard and soft exudates block the fluorescence so do foreign bodies and scar tissues, CSR, disciform degeneration and serous retinal detachment.

Filling defect—Vascular occlusion

Retinal artery obstruction, venous obstruction, choroidal infarct, healed scar of choroiditis, coloboma of choroid.

Indocyanine green angiography

This is less commonly used method of angiography. It is used to see outline of choroidal circulation because it delineates choroidal vessels better than fluorescein. Indocyanine green is a tricarbocyanine compound containing free iodine.31 It is totally bound to serum protein. It is excreted in bile, peak fluorescence is at 835 nm. It is injected intravenous like fluorescein. The fluorescence of indocyanine green is in the infra red range. The angiogram requires an exciting filter at 835 nm. ICG has 25 percent less fluorescence. It requires infra red sensitive video camera and video cassette recorder. It is mostly used to see choroidal neo vascularisation. It is used alternatively in patient sensitive to fluorescein. As ICG is iodine containing dye it is also likely to cause allergic reaction. Other use of indocyanine green is in maculorrhexis.32

Optical coherence tomography33,72,73,74

This is an imaging technology that give high resolution image of retina and optic disc, with modification it can be used to image cornea, lens and iris in diseases of anterior segment. The principle is almost the same as in ultrasonography, CT or MRI. The only difference is that the ultrasound uses sound, CT uses X-ray, MRI uses spin resonance, the OCT uses low coherent near infra red light beam (820 nm - 830 nm) from a super luminescent diode. It is important to have clear ocular media, the pupil should be atleast 4 mm in diameter. The results are reproducible, the method is non invasive, non contact.

The system consist of an inter ferometer that gives high resolution (10 to 20 ) in contrast to 100 of ultrasound. The light is delivered through a slit lamp with + 70D lens. It requires an infra red sensitive video camera. OCT is used to detect disorders of retina, especially the macula. It can differentiate between full thickness and partial thickness macular hole, the exact diameter of the hole and thickness of the retina surrounding the hole can be assessed. It can be used to document the progress of the treatment34. It is useful in central serous chorio retinopathy, macular edema, epiretinal membrane and age related macular degeneration, macular cyst. OCT has proved to be a valuable imaging method in evaluation of optic nerve changes in glaucoma.

Ultrasonography35

This is yet another non invasive procedure of multiple uses in ophthalmology. It uses inaudible sound. Sound audible to human ears range between 20 to 20,000 hertz (Hz). Sound used for ultrasonography is by far more than audible sound, it ranges in millions of cycles and noted as MHz or megahertz. Sound does not have any radiation or magnetism. Ultrasound used for ocular ultrasonography does not produce heat, it uses very low energy.

The ultrasound when directed towards the interior of the eye or orbit is reflected back towards the source as it meets a changed density or elasticity in the media through which it passes.

The ultrasound is generated in a transducer, which converts electric energy into sound waves. The transducer contains piezo electric crystal. This not only produces echo but also receives it back and converts it into electric potential that can be either photographed or printed on paper.

There are two main modes of ocular ultrasonography—(1) A scan, (2) B Scan. Each has its own utility. Sometimes both the methods may be required to clinch the diagnosis.

The A scan is time amplitude that gives linear one dimensional picture. The B scan is intensity modulated and gives two dimensional picture. Interpretation of A mode requires more skill than B mode.

A scan is used to find out ocular dimension i.e. AC depth, thickness of lens, thickness of the cornea. Length of the globe it is most widely used in calculating power of IOL. It has limited value in diseases of globe or orbit. The tracing is shown as a series of spikes. Distance between the two spikes is the distance between two acoustically different surfaces. Normal aqueous, vitreous do not produce any spike but anterior and posterior surfaces of lens give two spikes of almost same height with space in between. The space in between the two spikes is the thickness of the lens. Other important use of A scan is measurement of corneal thickness -

Ultrasonic pachymetry (Pachometry).

Abnormal content of vitreous like blood, blood clot, foreign body, cysts give positive spike. Retinal detachment, retinal tumours and choroidal growths also give positive spike provided they are in the path of the echo.

B scan gives a two dimensional picture of the globe and orbit. Instead of spikes it gives dots. Brightness of the dots depends upon size of the echoes reflected. The resulting picture though not very exact but is comparable to histopathological cross section. Different types of lesions have different shadows, some have specific appearance. B scan is mostly used to see vitreo retinal pathology in opaque media or hazy media where indirect ophthalmoscopy is not possible. It delineates opacities in vitreous. It differentiates between traction detachment, exudative detachment, celio choroidal detachment and rhegmatogenous. It also outlines intra ocular tumours, IOFB, endophthalmitis, cysts and parasites, position of dislocated lens. It is more useful in orbital disease than A scan. It is used in thyroid myopathy, orbital pseudo tumours, tumours of the optic nerve.

One of the advantages of ultrasonography is that it can be used as many times as possible in all ages in sitting or recumbent position with out any radiation hazard.

Dark adoptometery36,37

This investigation is performed less frequently, it measures the difference between recovery of rod and cone functions after they have been exposed to bright light. The cones recover faster than the rods. The cones have no vision in dark. They are photopic while rods function only in dark, they are scotopic. It is common experience that when some one walks in a dark area after being in the bright light for some time, it takes few seconds to start seeing in the dark.