Non mechanical injuries
- 1. Chemical injuries
Severity may vary from normal irritation to complete sudden loss of vision
Causes
- Domestic accidents such as ammonia, solvents, detergent and cosmetics
- Agricultural such as fertiliser, insecticides, toxins from vegetable and animal
- Chemical lab accident with alkali and acids
- And chemical warfare as well as riot control
Acid and alkali burns are the most serious
Alkali
Liquid ammonia, lime, caustic soda and potassium compounds
Mechanism :
Cause the dissociation and saponify Fatty acids hereby destroying cell membranes and tissues. The y also extract water from cells leading to necrosis and they also combine with lipids forming soluble compounds which produce soft and gelatine like substance .
These mechanisms are the reason for the deep penetration of alkalis and why their actions continues for days and their effects are difficult to limit
Clinically,
Conjunctiva shows oedema, congestion, necrosis and purulent discharge while cornea shed its epithelium , is full with oedema and starts to opacify . The iris becomes inflamed and can even be replaced by granulation tissue.
During reparation phase the corneal epithelium regenerates and it becomes vascularised and inflammation of iris stops
Complications include symblepharon, recurrent corneal ulceration as well as cataract and secondary glaucoma
Acids burns
Less serious than alkali and acids responsible for burns include hydrochloric/ nitric / sulphuric acid
It damages by causing instant coagulation of all the protein thus acting as a barrier to itself from entering deeper tissue hence the lesions are demarcated clearly.
Conjunctiva also experiences necrosis and symblepharon form
Cornea is also necrosed and also sheds and depending on the con of acid the entire cornea may be shed off causing Staphyloma formation
Treatment
Immediate and thought wash with clean water and saline and the use of chemical neutralisation is important with the weak acid/base equivalent , mechanical removal of substance as well as contaminated and necrotic tissue including conjunctiva and cornea . Symblepharon formation should be prevented and complicated should be tackled by treating secondary glaucoma with Timolol and corneal opacity with keratoplasty.
Thermal injuries
Caused by fire or hot fluids and mainly lids are affected, conjunctiva and cornea in severe cases
Electrical injuries
Causes congestion of conjunctiva and cornea develops opacities and iris and ciliary are inflamed while lens develops electric cataracts
Retina can also multiple haemorrhages and neuritis may develop