Does Your Job Involve Working Under High Temperature, How Does It Affect Your Vision

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Thermal or heat burns are of two types: flame and contact burns. These may be caused by hot bodies, fluids or gases. Burns usually involve the eye lids and not the globe, which will probably have been protected by the blink reflex. The characteristic picture is of marked oedema and tissue necrosis.

In some cases it may be necessary to open the lids forcibly to inspect the globe and then provide treatment, if required.

Flame burns

These occur frequently and may result where high temperatures and inflammable liquids are being used. Gases, ovens, furnaces and petrol stores are liable to explode and soaked overalls are also a potential fire hazard. The eye is rarely involved unless the heat is so intense and prolonged that the lids are destroyed. Generally the lashes and brow are scorched and the lids may be burnt with extensive damage to the face but the globe is unaffected. The burnt lids may need plastic surgery and ectropion must be prevented. There may be continuous weeping due to damaged lacrimal puncta and canaliculi, which have become blocked by subsequent fibrosis.

Contact burns

These may be caused by molten substances, such as metal or glass striking the cornea and entering the conjunctival sac. The molten substance solidifies as soon as it cools on hitting the eye and may fall into the lower fornix, where it continues to burn the surrounding tissue due to its latent heat. Prompt removal and irrigation reduces damage. The velocity of the hot particle may be such to perforate the eye, causing intra-ocular damage.

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Glowing solid bodies that retain heat, i.e. slag, molten metal, or glass at temperatures of, say, 1000C cause severe burns, scarring of the cornea and destruction of the conjunctiva, and this often leads to the loss of an eye. The intense reaction will lead to severe palpebral oedema, chemosis, and a purulent discharge. While superficial lesions are accompanied by pain, photophobia, and lacrimation, these corneal symptoms may be absent in severe cases because the nerves have been destroyed.

An entirely different reaction occurs with molten metal of relatively low melting point, such as lead, tin or zinc, which cause less damage. Accidents generally occur when pouring metals into moulds. The metal forms a thin mould over the eye, which can be picked off. Generally the tissue remains undamaged, but occasionally the cornea may be 'dull'. The conjunctiva may be oedematous in the contact area and plaques of encrusted metal may cause superficial burns of the palpebral skin and lid margins, where metal beads have adhered to the eye lashes. Vision is usually unimpaired, although small areas of symblepharon may result.

A burn to the cornea produces irregularity of its thickness and surface, and opacities that give distressing effects upon vision. Contact lenses may restore useful vision in mild cases but corneal grafting may be needed if more severe.

Scalds

Burns by hot fluids frequently affect the lids and face, but the eyes are protected by the blink reflex. Scalds may be caused by ruptures of pipes containing steam or due to splashes of pitch, tar, molten sulphur or boiling oil. Hence, there is usually partial skin loss of the face and lids.