Chemical Injuries of the Eye: Signs, Symptoms, Types, Grading, Treatment, Prevention

Chemical injuries of the eye are by no means uncommon. These are actually true medical emergencies and need immediate assessment and set of action. These vary in severity from a trivial and transient irritation of little significance to complete and sudden loss of vision. Let us understand the various aspects of chemical injuries of the eye and be aware of their signs and symptoms, types, grading, treatment and prevention.

Recent studies show that ocular burns of the eye or chemical injuries of the eye are 7-8% more common than any other injuries of the eye. Majorly all the victims are young people and chemical injuries of the eye frequently occur at home, work and in association with criminal assaults. Alkali injuries occur more frequently than acidic injuries and are scientifically more dangerous than acid injuries.

Chemical injuries of the eye usually occur due to external contact with chemicals under following circumstances:

1. Domestic accidents, e.g., with ammonia, solvents, detergents and cosmetics.
2. Agricultural accidents, e.g., due to fertilizers, insecticides, toxins of vegetable and animal origin.
3. Chemical injuries of the eye due to laboratory accidents, with acids and alkalis.
4. Deliberate chemical attacks, especially with acids to disfigure the face.
5. Chemical warfare are also a common occurrence in chemical injuries of the eye.
6. Self-inflicted chemical injuries are seen in malingerers and psychopaths.

It is important to know the signs and symptoms of chemical injuries of the eye as it can help to reach for immediate medical care. Some of the early signs and symptoms noted in chemical injuries of the eye include

• Pain and redness of the eye
• Irritation and tearing
• Mucoid discharge from the affected eye
• Inability to keep the eye open
• Sensation of something in the eye
• Swelling of the eyelids
• Blurred vision
• Sudden blindness

In general, the serious chemical injuries of the eye mainly comprise alkali and acid burns.

1. Alkali Burns Causing Chemical Injuries of the Eye

   Alkali burns are among the most severe chemical injuries known to the ophthalmologists. Common alkalis responsible for burns are: lime, caustic potash or caustic soda and liquid ammonia (most harmful).

   Mechanisms of Damage Produced by Alkalis Includes:

   1. Alkalis dissociate and saponify fatty acids of the cell membrane and, therefore, destroy the structure of cell membrane of the tissues.
   2. Being hygroscopic, they extract water from the cells, a factor which contributes to the total necrosis.
   3. They combine with lipids of cells to form soluble compounds, which produce a condition of softening and gelatinization.

   The above effects result in an increased deep penetration of the alkalis into the tissues. Alkali burns, therefore, spread widely, their action continues for some days and their effects are difficult to circumscribe. Hence, prognosis in such cases must always be guarded.

   Clinically, such chemical injuries of the eye can be divided into three stages:

1. Stage of Acute Ischemic Necrosis – In this stage, the conjunctiva shows marked edema, congestion, widespread necrosis and a copious purulent discharge.

   1. Cornea develops widespread sloughing of the epithelium, edema and opalescence of the stroma.
   2. Iris becomes violently inflamed and in severe cases both iris and ciliary body are replaced by granulation tissue.
2. Stage of Reparation – In this stage conjunctival and corneal epithelium regenerate, there occurs corneal vascularization and inflammation of the iris subsides.
3. Stage of Complications – This is characterized by development of symblepharon, recurrent corneal ulceration and development of complicated cataract and secondary glaucoma.

2. Acid Burns Causing Chemical Injuries of the Eye

   Acid burns are less serious than alkali burns. Common acids responsible for burns are: sulphuric acid, hydrochloric acid and nitric acid.

   Chemical effects produced by such chemical injuries of the eye – Strong acids cause instant coagulation of all the proteins which then act as a barrier and prevent deeper penetration of the acids into the tissues. Thus, the lesions become sharply demarcated.

   Ocular Lesions

   1. Conjunctiva – There occurs immediate necrosis followed by sloughing. Later on symblepharon is formed due to fibrosis.
   2. Cornea – It is also necrosed and sloughed out. The extent of damage depends upon the concentration of acid and the duration of contact. In severe cases, the whole cornea may slough out followed by staphyloma formation.

Depending upon the severity of damage caused to the conjunctiva and cornea, the extent of chemical burns may be graded as follows,

• Grade 1 Chemical Injury of the Eye: – Epithelial damage usually occurs in cornea, conjunctiva is good with no ischemia and prognosis is good
• Grade 2 Chemical Injury of the Eye: – Cornea is hazy but iris details are visible, conjunctiva shows chemosis and ischemia affecting less than 1/3rd of limbal conjunctiva. Prognosis is good.
• Grade 3 Chemical Injury of the Eye:- Cornea loses all its epithelium and iris details are not visible. Ischemia affects one third to two third of limbal conjunctiva and prognosis is doubtful.
• Grade 4 Chemical Injury of the Eye: – Cornea becomes opaque and there is no view of iris or pupil and more than two third of conjunctiva becomes ischemic and necrosed, making very poor prognosis.

Some of the commonest ways of treatment of chemical injuries of the eye include:

1. Immediate and thorough wash with the available clean water or saline.
2. Chemical neutralization – It should be carried out when the nature of offending chemical is known. For example, acid burns should be neutralized with weak alkaline solutions (such as sodium bicarbonate) and alkali burns with weak acidic solutions (such as boric acid or mix) Ethylene diamine tetra acetic acid (EDTA) 1% solution can also be used as neutralizing agent.
3. Mechanical removal of contaminant – If any particles are left behind, particularly in the case of lime, these should be removed carefully with a swab stick.
4. Removal of contaminated and necrotic tissue – Necrosed conjunctiva should be excised. Contaminated and necrosed corneal epithelium should be removed with a cotton swab stick.
5. Maintenance of favorable conditions for rapid and uncomplicated healing by frequent application of topical atropine, corticosteroids and antibiotics.
6. Prevention of symblepharon can be done by using a glass shell or sweeping a glass rod in the fornices twice daily.

In case of complications due to chemical injuries of the eye, the following treatment options can be followed.

• Secondary glaucoma should be treated by topical 0.5 percent timolol instilled twice a day along with oral acetazolamide 250 mg 3-4 times a day.
• Corneal opacity may be treated by keratoplasty.
• Appropriate treatment of symblepharon

Safety officials estimate that up to 90% of chemical eye injuries can be avoided. These often include following the basic instructions every day and everywhere, which include:

• Always wear safety glasses when working with hazardous materials, both at work and at home whether indoors or outdoors.
• Children sustain chemical burns most often when they are unsupervised. Keep all hazardous home products away from children. If in case they need to work with them be their and assist them completely throughout the process.