CHEMICAL INJURIES OF

THE EYEBY JAYALAKSHMI MOHAN

CHEMICAL INJURIES

• THESE vary in severity from a trivial and transient irritation of little significance to complete and sudden loss of vision

MODES OF INJURY• These usually occur due to external contact withchemicals under

following circumstances

1. DOMESTIC ACCIDENTS;eg with ammonia ,solvents,detergents,cosmetics

2. AGRICULTURAL ACCIDENTS;due to fertilizers,insectisides,toxins of vegetables and animal origin

3. CHEMICAL LABORATORY ACCIDENTS;with acids and alkalies

4. DELIBERATE CHEMICAL ATTACKS;especially with acids to disfigure face

5. CHEMICAL WARFARE INJURIES

6. SELF INFLICTED CHEMICAL INJURIES seen in psychopaths

TYPES• 2 TYPES

ALKALI BURNS

ACID BURNS

1.ALKALI BURNS

• Most severe chemical injurie known to ophthalmologists

• Common alkalies responsible for burns:

Lime

Caustic potash or caustic soda

Liquid ammonia(most harmful)

MECHANISMS OF DAMAGE PRODUCED BY ALKALIES

1.Alkalies dissociate and saponify fatty acids of cell membrane

Destroy structure of cell membrane of the tissue

2.Being hygroscopic ,they extract water from the cells

3.They combine with lipids of cell to form soluble compounds,which produce a condition of softening and gelatinisation

The above effects results in

o An increased deep penetration of alkalies into the tissue

o Alkali burns,spread widely,

o Their action continues for some days

o Their effects are difficult to circumscribe

o Hence prognosis in such cases must always be guided

CLINICAL PICTURE

1.STAGE OF ACUTE ISCHEMIC NECROSIS

Conjunctiva shows marked oedema,congestion,widespread necrosis and copious purulent discharge

Cornea develops widespread sloughing of the epithelium,oedema and opalescence of the stroma

Iris becomes violently inflamed and in severe cases both iris and ciliary body are replaced by granulation tissue

2.STAGE OF REPARATION

Conjunctival and corneal epithelium regenerates,there occurs corneal vascularization and inflammation of iris subsides

3.STAGE OF COMPLICATION

Development of symblepharon,recurrent corneal ulceration,development of complicated catareact and secondary glaucoma

3 STAGES:

1) STAGE OF ACUTE ISCHAEMIC NECROSIS

2) STAGE OF REPARATION

3) STAGE OF COMPLICATIONS

2.ACID BURNS

• Less serious than alkali burns

• Common acids responsible for burns:

Sulphuric acid

Hydrochloric acid

Nitric acid

CHEMICAL EFFECTS

• Strong acids cause instant coagulation of all proteins which then act as a barrier and prevent deeper penetration of the acids into the tissue

• Lesion becomes sharply demarcated

OCULAR LESIONS

1.CONJUNCTIVAThere occurs immediate

necrosis followed by sloughing

Later symblepharon is formed due to fibrosis

2.CORNEAIt is also necrosed and

sloughed out

Extent of damage depends upon the concentration of acid and the duration of contact

In severe cases whole cornea may slough out followed by staphyloma formation

GRADES OF CHEMICAL BURNS

GRADE CORNEAL APPEARANCE

LIMBAL ISCHAEMIA

VISUAL PROGNOSIS

I CLEAR CORNEAL

NIL GOOD

II HAZY BUT IRIS DETAILS VISIBLE

<1/3 GOOD

III OPAQUE CORNEA.IRIS DETAILS OBSCURED

1/3 TO 1/2 DOUBTFUL

IV OPAQUE,NO VIEW OF THE IRIS AND PUPIL

>1/2 POOR

Depending upon the severity of damage caused to the limbus and cornea,the extend of chemical burns may be graded in ROPER-HALL classification as follows:

TREATMENT OF CHEMICAL BURNS

1.Treatment and thorough irrigation

With clean water or saline delivered through an I.V tube.Deliver minimum of 2L water or until pH is restored

2.Mechanical removal of contaminant

particles left behind should be removed carefully with swab stick

3.Removal of contaminated and necrotic tissue

Necrosed conjunctiva should be excised.

4.Maintenance of favourable conditions

5.Prevention of symblepharon

Done by using a glass rod in the fornices twice daily

6.Treatment of complicationsi.SECONDARY GLAUCOMA should be treated by topical 0.5% Timolol,instilled twice a day along with oral Acetazolamide 250 mg 3-4 times a dayii.POOR CORNEAL HEALING with limbal stem cell deficiency may be treated by amniotic membrane transplantation with or without limbal stem cell transplantationiii.PSEUDOPTERYGIUM should be excised together with conjunctival autograft or amniotic membrane facilitated by antimiotic drugs(eg:mitomycin-C)iv.TREATMENT OF SYMBLEPHARONv.CORNEAL OPACITY may be treated by keratoplasty if adequate tear film and stem cell population availablevi.KERATOPROSTHESIS remains a surgical option in severely damaged eyes

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