Anterior Segment Cornea Harold Merle,1
Severe Ocular Burns Max Gerard2
and Norbert Schrage3
1. Service d’Ophtalmologie, Martinique; 2. Service d’Ophtalmologie, Centre Hospitalier de Cayenne, Guyane; 3. University Hospital Aachen, Department of Ophthalmology, Cologne
Abstract
The worst ocular lesions are chemical burns caused by strong bases and acids. Associated with the destruction of limbal stem cells (LSCs), there are repeated epithelial ulcerations, chronic stromal ulcers, deep stromal neovascularisation, conjunctival invasion and even corneal perforations. The initial clinical examination is difficult because the symptomatology is severe, but nevertheless it helps to classify the lesions, to establish a prognosis and to guide the therapeutic care. The classification system used most is that implemented by Hughes and modified by Roper-Hall. It is now completed neatly by those proposed by Dua and Wagoner, which are based on the importance of the deficit of LSCs. Prognosis of severe forms has progressed significantly thanks to a better knowledge of the physiology of the cornea’s epithelium. Surgical techniques to repair destroyed LSCs have changed the prognosis of severe corneal burns significantly. To limit the incidence of burns, prevention, especially in the industrialised world, is essential.
Keywords Ocular burns, chemical burns, ocular lavage, ocular irrigation, ocular surface, limbal transplant, amniotic membrane transplant
Disclosure: The authors have no conflicts of interests to declare. Received: 19 September 2011 Accepted: 13 October 2011 Citation: European Ophthalmic Review, 2011;5(2):130–3 Correspondence: Harold Merle, Service d’Ophtalmologie, Centre Hospitalier Universitaire de Fort-de-France, Hôpital Pierre Zobda Quitman, BP 632, 97261 Fort-de-France Cedex, Martinique, France (French West Indies). E:
harold.merle@
chu-fortdefrance.fr
Chemical or thermal ocular burns represent about 10 % of ocular traumas.1,2
Generally, bilateral burns are found in young male subjects. Work-related, domestic or recreation accidents, as well as assaults, are the main sources of ocular burns.
Epidemiology
Chemical burns are more common and caused by strong bases or acids. They are also responsible for the most severe and heavy psychological, social and legal consequences. The proportion of domestic accidents linked to ‘do-it-yourself’ or gardening is increasing constantly and exceeds one-third in some series.3
A lesion’s severity depends on the nature, concentration, quantity, length of exposure
and pH of the chemical substance. Bases (ammonia [NH3], sodium hypochlorite (NaClO], sodium hydroxide [NaOH], potassium hydroxide
[KOH], calcium hydroxide [Ca(OH)2], etc.) enter the ocular area easily. The anions saponify the fatty acid of the cells’ membranes, which results in the instant death of epithelial cells.
Among the acids (hydrofluoric acid [HF], hydrochloric acid [HCl],
chromic acid [Cr2O3], acetic acid [CH3COOH], etc.), sulphuric acid or vitriol (H2SO4) is the cause of the worst accidents. Acids infiltrate more slowly than bases because the protons (H+) accelerate and
denature the proteins. The superficial coagulation then created limits deeper infiltration of the acid in the cornea. For contact thermal burns, solids that retain heat and those with a high fusion point lead to deep lesions that sometimes result in the loss of the ocular globe.
The course of an ocular burn depends on the nature of the responsible chemical component; nevertheless, all share several evolving elements.
130 Semiotics and Classification
An ocular burn is an emergency and the initial clinical examination must lead first to therapeutic measures, especially during the ocular lavage. Data from the initial examination should be considered baseline and distinguished from further lesions observed during the burn’s evolution.
At the acute phase, questioning of the patient provides more details about the circumstances of the appearance and time of the trauma, as well as the nature of the products responsible and the procedures already performed. Symptomatology can be very expressive (photophobia, weeping, etc.) and the pain significant. Instillation of an anaesthetic eye drop can help to lower eyelid spasms. The eye is usually red because of a hyperaemia of the conjunctiva, subconjunctival bleeding, a perikeratic circle and/or a chemosis. Besides destruction of the epithelium, severe corneal burns are associated with an oedema of a porcelain appearance. A more serious affect is characterised by the existence of ulcerations and/or ischaemia or necrotic areas of the limbal
© TOUCH BRIEFINGS 2011
Thus, an initial incineration phase is followed after a few minutes to a few hours by a detersion of necrosis lesions and then the scarring phase. Detersion is defined as a rush of inflammatory cells to produce several enzymes, such as the matrix metalloproteinases (collagenases, gelatinases and stromelysin). While taking part in the detersion, these enzymes increase the destruction of the ocular structures.4
The scarring
results from the regrowth of healthy tissues that surround the burn. This involves ischaemic lesions consequent to the destruction of the vascular network and to lesions of the corneal and conjunctival cells. Scarring of the cornea and the conjunctiva can happen through the differentiation of surviving cells into fibroblasts or by the division of stem cells.5
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