Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

of the opacities are permanent, other may disappear with treatment or spontaneously. Some of the opacities may increase in size, number or depth. Central corneal opacities cause more visual loss. Peripheral opacities with clear pupillary area generally have only cosmetic effect. Corneal opacities in the centre of cornea not only block the light rays from reaching the pupil but also cause scattering of light and irregular astigmatism. Rarely corneal opacities can be congenital.

Causes of Corneal Opacities in Children

Corneal opacities in children can be caused by any of the following separately or in combination—Congenital, infection, inflammation, allergy, trauma, malnutrition, degeneration and dystrophies.

Congenital corneal opacities :

Cornea of new born is mildly hazy. The haze gradually disappears in next two to three days. If cloudiness persists following causes should be excluded :

1.Intrauterine infection

2.Birth trauma

3.Infantile glaucoma, mucopolysccharidosis and mucolipidosis. The congenital causes of corneal opacity includes—sclerocornea.

Corneal opacities in children have far reaching consequences not only regarding vision but also mental development. The child may remain permanently visually challenged. Thus corneal opacities are one of the most common but neglected cause of amblyopia and squint when unilateral and nystagmus when bilateral.

Causes of bilateral corneal opacities in children (on the basis of age of onset) :

catarrah, corneal dystrophies, band keratopathy, interstitial keratitis, limbal dermoid.

Corneal Edema

To maintain optical clarity, cornea must remain in a state of relative hydration. Accumulation of fluid in cornea causes it to swell up. Corneal edema may be localised in epithelium, stroma or may involve both. The corneal epithelium and endothelium regulate passage of fluid and ions. Deranged fluid transport across the cornea causes corneal edema. Epithelial edema causes more visual loss due to irregular astigmatism that results following accumulation of fluid in the basal cells of the epithelium and forming a bullae. Epithelial edema presents as diminished vision specially on awakening. In well formed bullae blinking causes foreign body sensation that becomes more marked if the bullae ruptures. There may be

associated pain, redness and photophobia. Ruptured bullae may result into anterior chamber reaction and formation of sterile hypopyon or may lead to bacterial corneal ulcer. Stromal edema causes less loss of vision and less symptoms. It results in haziness of stroma and thickening of cornea.

Common causes of corneal edema are :

1.Trauma to endothelium—accidental or surgical during IOL implant, placement of glaucoma valve, penetrating keratoplasty.

2.Trauma to epithelium—Ill fitting contact lens, chemical burn.

3.Aphakia

(a) Due to vitreous in AC

(b) Toxicity of irrigating fluid

(c) Trauma during manipulation of IOL (d) Silicone oil in AC.

4.Acute rise of tension, persistent raised tension, rupture of Descemet’s membrane.

5.Keratoconus—acute hydrops

6.Herpctic disciform keratitis

7.Fuchs dystrophy

8.Chronic uveitis

9.Keratocele (Descemetocele)

10.Iris incarceration

11.Corneal staphyloma (Anterior staphyloma).

Corneal neovascularisation15, 30, 31

Out of all refractive media i.e. cornea, aqueous, lens and vitreous, cornea has maximum refractive power. For a sharp retinal image all factors remaining within normal limits cornea must remain transparent. Avascularity of cornea plays a very important role in keeping cornea bright and transparent. Cornea is almost avascular except 1 mm of periphery adjacent to the limbus and vessels do not grow into corneal substance so long cornea is not diseased. Growth of vessels in cornea is blocked by compactness of corneal tissue and anti vascular chemical factors present in the cornea. Once the compactness of cornea is lost, vessels start growing into the substance of cornea both in epithelium and stroma. The anti vascular factor may be overwhelmed by a vasoformative factor in newly formed vessels. Vessels once formed in cornea never disappear, they may get obliterated leaving tell a tale sign of ghost vessels which are more prominent in deep vascularisation. Presence of corneal vascularisation is always pathological. Factors that encourage corneal vascularisation are—trauma, infection, inflammation, hypoxia, hypo vitaminosis B, allergy and degeneration.

Corneal vascularisation can be put into three groups depending upon the layer at which they develop i.e.

Superficial vascularisation of cornea is commonest form of vascularisation. This is due to extension of conjunctival vessels into the cornea in front of Bowman’s membrane. According to its extent in the cornea it is divided into

Pannus is a fibro vascular proliferation that extend up to the cornea, it is essentially a defensive process against infection, toxin, trauma etc. It can be sectorial or may involve whole of corneal periphery. It is always preceded by infiltration of corneal epithelium by polymorphonuclear and mononuclear cells. Cellular infiltration is followed by development of tufts of new vessels. It may destroy the Bowman’s membrane causing corneal haze. There are three clinical stages of superficial corneal vascularisation i.e. (1) Progressive stage, (2) Stationary stage, (3) Regressive stage.

In the progressive stage, blood vessels grow towards the centre of the cornea. They may be parallel to each other. A zone of cellular infiltration extends beyond the tip of the vessel terminal.

In regressive stage the zone of infiltration is between the tip of the blood vessels and the limbus, other things remaining the same.

Superficial vascularisation can be seen as—micropannus or as gross pannus.

Micropannus30 extend only one to two millimeter beyond the normal limbal arcade. It is most commonly seen is contact lens wearer. Milder form of chlamydia kerato conjunctivitis, vernal catarrh, chronic blepharitis.

Gross pannus extend more than 2 mm beyond normal limbal vessels. It is seen in trachoma, phlyctenulosis, rosaceakeratitis, atopickerato conjunctivitis, contact lens wearer, severe blepharoconjunctivitis, herpetickeratitis, riboflavin deficiency, corneal graft rejection. In gross pannus sometimes there may be a large and prominent vessel which may be very prominent or there may be a tuft of localised vessels as seen in fascicular ulcer.

Deep vascularisation of cornea

In this condition anterior ciliary blood vessels invade the cornea at the level of stroma. They have very characteristic feature :

1.They are generally straight and parallel to each other.

2.They do not anastomose with each other.

3.Branch at an acute angle from the main branch giving a bottlebrush appearance.

4.They are generally sectorial in distribution.

5.The vessel seem to disappear at limbus.

6.The vessels grow in the particular plane and remain in the same plane.

7.They are always associated with deep keratitis, and uveitis.

8.When severe, they give a pink hue to the cornea known as Hutchinson’s salmon patch.

9.Rarely there may be associated superficial vascularisation at the level of epithelium giving an epaulet appearance to the peripheral cornea.

10.Deep vascularisation gives a ground glass appearance to the cornea.

11.When the inflammation is under control the vessels obliterate leaving a track of ghost vessels that last for rest of the life.

Causes of deep vascularisation are—Congenital syphilis, tuberculosis, leprosy, herpes simplex, chemical burn.

Retrocorneal vascularisation. This type of vascularisation is mostly seen when blood vessels from uvea develop on the endothelium of the cornea either due to chronic uveitis, diabetic neovascularisation or thrombosis of retinal vein. They may also grow from conjunctiva following—penetrating injury at the limbus, penetrating keratoplasty, and conjunctival epithelial down growth.

Inter corneal vascularisation. This happens rarely when limbal vessels grow under the partial thickness wound of the cornea either accidentally or following large lamellar graft.

Rupture and folds in Descemets membrane32, 33, 34 :

Descemets membrane is likely to rupture :

1.If the eyeball is compressed suddenly like in birth injury or concussion injury to the globe.

2.The cornea stretches either due to thinning as seen in keratoconus and buphthalmos.

Rupture of Descemet’s membrane is more common in buphthalmos than in keratoconus. In buphthalmos there is not only thinning of the cornea but also an enlargement of cornea that stretches the Descemet’s membrane. The tears differ in shape, size, number and position. With ophthalmoscope they stand out as dark double lined areas in red background. The area between the two lines also give a red glow. They may be linear, curvilinear or whirl like. Their presence in buphthalmos is known as Haab’s line which are curvilinear. Opaque lines that represent healed breaks in Descemet’s membrane. With rupture of Descemet’s membrane there is a sudden influx of fluid into the stroma leading to stromal edema, lacrimation and photophobia. Stromal edema may subside with treatment but may persist to cause permanent scarring of cornea that is so common in untreated or poorly managed buphthalmos. Ruptures due to elevated IOP are either horizontal or parallel to limbus. Rupture in Descemet’s membrane due to trauma are generally central and vertical. Some of the dystrophies may look similar to Haab’s striae.

Folds in Descemets membrane are more common than tears. They can be caused by trauma, both blunt as well as incised wound. Other causes are prolonged uveitis with hypotony.

Keratic precipitate (see diseases of uvea)

Loss of corneal sensation. Cornea is very richly supplied by sensory nerve endings of trigeminal nerve. There is only one sensation in cornea i.e. pain. An intact corneal sensation is essential for health of cornea specially the epithelium. It is of diagnostic significance not only for local corneal diseases but also neuro ophthalmic diagnosis. Corneal sensation may be marginally reduced or may be totally absent.

Causes of diminished corneal sensation are :

1.Recent use of local anaesthetic agent,

2.Use of contact lens.

3.Herpes simplex, herpes zoster, leprosy.

4.Corneal edema, corneal scar, corneal vascularisation.

5.Buphthalmos

6.Repair of corneal wound, keratoplasty

7.Vitamin A deficiency

8.Deposits on cornea i.e. band keratopathy, tattoo

9.Cerbropontine angle tumour

10.Trigeminal neuritis

Xerosis of cornea (see xerophthalmia)

Corneal Ulcer in Children

Inflammation of cornea secondary to micro-organisms is called keratitis. Keratitis with loss of epithelium is called corneal ulcer. A large group of cases which are not caused by microbes are grouped under a loose term - Keratopathy. Keratitis in children basically does not differ from those seen in adults, however, complications are more in children. Most of keratitis in spite of good management leave corneal opacity that may produce amblyopia and squint. Keratitis in infancy may be responsible for nystagmus. Hence keratitis requires prompt diagnosis and efficient management.

Keratitis in general has been described under various heading. However most accepted classification by Duke Elder 1565 on the basis of etiology still remains most widely accepted classification. Though it too has its short comings. The classification is as follows -

3.Deep keratitis

1.Superficial keratitis has been divided into (a) Diffuse and punctate keratitis

(b) Corneal ulcer

(c) Degenerative superficial keratitis.

(a) Diffuse superficial keratitis can be

(i) Acute superficial keratitis as seen in acute bacterial and viral conjunctivitis that may result in corneal ulcer.

(ii) Chronic superficial keratitis is seen mostly in trachoma, leprosy, mollouscum contagiosum, phlycten. Chronic superficial keratitis is characterised by pannus formation.

Superficial keratitis can be diffuse or punctate.

Punctate keratitis stain irregularly and poorly with fluorescein but better with rose bengal. A lesion may stain partly with fluorescein and partly with rose bengal depending upon level of the lesion. The unstained lesion’s have a whitish appearance. The size, shape and distribution of superficial punctate keratitis vary depending upon severity and duration of the

(b) Systemic. Prolonged use of steroid, resistant organisms AIDS.

7.Cornea subjected to constant inoculation by micro-organism i.e. chronic dacryocystitis, blepharoconjunctivitis.

8.Central corneal ulcers are generally due to exogenous infection. Peripheral ulcers are generally non infective.

Pathogenesis of corneal ulcer35

Evolution of infective corneal ulcer has following stages :

1.Invasion by micro-organism. Organism generally get access to cornea following trauma, gonococci meningococci and diphtheria however may invade intact epithelium. In herpes simplex and zoster, organism reach cornea via sensory nerve ending. Organisms also reach cornea by direct continuity of conjunctiva, in case of acute bacterial conjunctivitis.

2.Progressive infiltration. Once micro-organism has reached traumatised epithelium, there is infiltration by polymorphonuclear and lymphocytes that results into a white corneal opacity with edema of epithelium over the opacity, this is followed by necrosis of epithelium and formation of ulcer that stains with fluorescein. If proper anti-microbial drugs are used at this stage, further progress can be averted or minimised resulting into clear cornea.

3.Active ulceration. The infected epithelium is necrosed and sequesteredoff with stromal infiltration. The ulcer deepens with infiltration and edema of the stroma. At this stage anterior uveitis develops due to toxins liberated by the organism which percolate to endothelium and spreads to uvea resulting into pain, photophobia, watering, circumciliary congestion disproportionate to size of the ulcer. If the anterior chamber reaction is severe, hypopyon may develop. The ulcer may spread all around towards the periphery and or it may deepen to reach the Descemet’s membrane which is tougher than other structures of cornea hence is not destroyed with ease. The Descemet’s membrane bulges through the defective stroma even with normal IOP and forms a keratocele or Descemetocele. If intraocular pressure rises suddenly or remains raised for considerable time, the Descemet’s membrane gives way and a perforation of cornea results with resultant loss of AC, softening of eye and plugging of perforation by iris. If the perforation is large, intraocular contents including lens may be expelled through the perforation.

Commonest site for perforation is centre of the cornea which is thinnest. If the perforation is small but is not closed by iris, a corneal fistula results.

4. Regression. Healing is initiated by natural defence mechanism of host cornea. This is enhanced by treatment. Healing starts with laying down of fibrocytes in place of normal keratocytes. The fibrocytes are opaque and do not confirm with normal corneal architecture, there may be associated superficial vascularisation. Over all result is formation of a corneal opacity depending upon the depth of the opacity it can be -nebular, macular or leucomatous. If iris is incarcerated, there will be a leucoma adherent. In case of a large perforation incarceration of total iris in the margin of the ulcer causes an anterior staphyloma which bulges even with normal intraocular tension.

Failure of regression. Small and superficial ulcers may heal in due course with resultant corneal opacity without treatment. Deep and large ulcers heal with treatment. If

progression of ulcers is not checked, the ulcer is bound to perforate, resulting into—leucoma adherent, anteriorpolarcataract, complicated cataract, cornealfistula, anterior staphyloma, endophthalmitis, pano-phthalmitis, phthisis.

Clinical features of corneal ulcer35, 37, 38. For a corneal ulcer to develop breach in epithelium is a prerequisite except in gonococcus, meningococcus and diphtheria. Breach in epithelium is brought about by trauma. Trauma is generally mechanical, severity of trauma is variable, it may be so trivial that the child may not be able to recollect. In infants trauma by own nails is very common. Depending upon type and virulence of offending organism ulcer may develop within hours to days. Fungal ulcers take weeks to manifest.

Pneunococcus, pseudomonas have short incubation period. Sometimes there may be more than one offending organism responsible for corneal ulcer.

Symptoms :

1.Lacrimation and foreign body sensation. These are the two early symptoms. Foreign body sensation becomes worse and is converted into dull ache, pneumococcal, pseudomonas, Koch-Weeks bacilli produce severe pain.

2.Redness of eye is due to circumciliary congestion.

3.Most of the bacterial corneal ulcers are associated with mucopurulent conjunctivitis.

4.Vision - Visual status depends upon position of ulcer itself, and area of surrounding infiltration. Central ulcers produce more visual loss while peripheral ulcers may not hamper vision at all or visual loss is minimal. With progression of ulcer, vision diminishes fast.

5.Blepharo-spasm is a prominent feature in children, this is associated with photophobia due to irritation or trigeminal nerve. Spasm of the ciliary body is the foremost cause of pain. Other cause of pain is stimulation of corneal nerve endings. Corneal nerve endings become numb with progress of ulcer.

6.In case of hypothesia of cornea that is found in herpes simplex and neurotropic ulcers patient may not complain of pain.

7.Late increase of pain is due to rise of intraocular pressure. Sudden relief of pain is an ominous symptom, it means perforation.

Signs. The ulcer starts as an area of greyish infiltration that is lustureless, there is distortion of windows reflex over the ulcer. The surrounding area is edematous and infiltrated by inflammatory cells. Generally there is single central ulcer, peripheral ulcers may be multiple. The ulcer stains bright green with fluorescein. The edge of the ulcer stains brighter than floor. The surrounding edematous and infiltration takes a yellowish green stain. Biomicroscopy shows anterior chamber reaction with flare and cells. In severe ulcer hypopyon may become evident.

Circumcorneal congestion is prominent sign of anterior uveal inflammation that follows deepening of the ulcer and liberation of toxin.

Corneal sensation is diminished in viral ulcers, large sloughing ulcers and neurotropic ulcers.

Staining of corneal lesions. Corneal lesions are stained by vital stains. Two commonly used stains are Fluorescein and Rose Bengal. Purpose of staining is to demonstrate presence of a stainable lesion i.e. abrasion, desquamation, ulceration, epithelial edema, mucous, dead and damaged cells.

Fluorescein remains extracellular, it stains tear film also but not the dry spot. It stains epithelial defect, large lesions are visible with ordinary flash light, small and faint lesions are best seen under cobalt blue filter with magnification. It is used either as one percent autoclaved solution or as 1% stain impregnated, pre sterilised, single use, disposable strip. Fluorescein does not cause irritation of cornea or conjunctiva. It is water soluble, hence washable.

Other purpose is to know the extent of ulcer, its progress or healing. Fluorescein staining should be performed after testing corneal sensation and before instilling local anaesthetic agent. While using fluorescein its sterility should be guaranteed. Fluorescein is notorious to harbour pseudomonas. Other uses of fluorescein are contact lens fitting, applanation tonometry, demonstration of leaking wound, tear film study. Extra corneal examination uses are fluorescein angiography, evaluation of patency nasolacrimal duct i.e. Jones I and II test. Seidel test to demonstrate leaking surgical wound 20% fluorescein solution has been used with some success in treatment of pediculosis and phthiriasis of lid margin.

Rose Bengal. Chemically rose bengal is similar to fluorescein and is water soluble. Dry crystals of both the chemicals are brown in colour. Rose bengal is used to stain mucous, dead and damaged cells. It is used along with fluorescein in many superficial corneal lesion. Rose bengal stains peripheral viral laden cells and fluorescein will stain floor of the ulcer in herpatic ulcer. Rose bengal stains filament of epithelium in filamentary keratopathy while base of the filament stains with fluorescein.

It does not share infectious tendency of fluorescein. Only drawback with rose bengal is its sting. Rose bengal causes severe stinging sensation of the conjunctiva. The patient should be informed about this phenomenon which is otherwise harmless. Prior instillation of local anaesthetic abolishes sting of rose bengal, however, xylocaine can cause epithelial changes that may stain with rose bengal. Proparacine hydrochloride 1% aqueous drops is the only recommended local anaesthetic that does not interfere with rose bengal stain.

Documentation of corneal lesions. Lesions of cornea are documented by drawing with international colour code. Like colour coded drawing of fundus for retinal lesions. Corneal lesions are drawn in two views. One is frontal and other is vertical section of anterior segment as seen on slit lamp. For finer details an optical section of cornea may be drawn.

Management of infective corneal ulcer :

Confirmation of diagnosis—History, clinical examination and stain give definite clue to causative factor.

Infective ulcers can be caused by—bacteria, fungi and viruses. Bacterial ulcer may be caused by single organism or there may be mixed infection. It is very common for viral and fungal ulcers to be contaminated by bacteria. Reverse is also possible but rare. Each group of organism have specific characteristics.

Characteristics of bacterial corneal ulcer :

They are :

1.Generally central, even when cornea is infected by bacteria on the periphery due to some ill understood phenomenon ulcer starts in the centre.

2.Most of the bacterial ulcers are associated with mucopurulent conjunctivitis.

3.They develop in short time following injury and spread fast.

4.Bacterial corneal ulcers are likely to develop hypopyon more frequently.

Most of the bacteria are capable of producing hypoypon. However pneumococci, pseudomonas, streptococcus and staphylococci are more common causative factors than others.

5.Bacterial ulcers are generally associated with severe pain especially in pneumococcal ulcers.

6.They promptly stain with fluorescein.

7.Sensation over clear cornea is generally normal.

8.Scrapping from fresh and untreated ulcer give positive smear, that can be cultured and sensitivity of the organism to antibiotic can be determined.

Characteristics of fungal ulcer37, 40, 41. Like bacterial ulcers, fungal ulcers are also central in nature, they are more indolent. In most of the cases there is history of trauma by organic material. It takes seven to fifteen days for a fungal ulcer to develop following injury. If an aggressive ulcer develops following corneal injury within twenty four hours, the chances are that it is a bacterial ulcer. History of prolonged and indiscriminate use of local and systemic steroid is second most predisposition. Exposure keratitis, anaesthetic cornea, edematous cornea are also likely to develop fungal ulcer.

Fungal corneal ulcer has a few typical features42 :

1.It is central, indolent, yellowishwhite ulcer with dull, dry surface that has zone of infiltration all round, there are smaller satellite lesions away from the main ulcer.

2.There is pronounced anterior chamber reaction that results in formation of endothelial plaque and thick almost organised hypopyon.

3.Scrapping from the ulcer show fungus in 10% KOH solution, and stains with Giemsa stain, P.A.S. or Gomori methamine silver stain.

4.Fungi are cultured at room temperature on blood agar and Sabouraud medium.

5.Corneal biopsy may be needed some time.

Characteristics of viral ulcer. Almost all viruses that invade conjunctiva also involve cornea and produce various types of superficial keratitis only herpes group of viruses i.e. simplex type I, type II and zoster virus are of clinical significance as far as corneal ulceration is concerned. Primary herpes simplex is disease of infants and children. Recurrent ulcers