Describe the classification and clinical assessment of ocular trauma.

Epidemiology and Classification

• Ocular trauma is a leading cause of monocular blindness worldwide, and is important out of proportion to its frequency because it affects young, working, predominantly male people and is almost entirely preventable
• In INDIA the pattern is distinctive — a high burden of agricultural and industrial injury in workers without eye protection; road traffic injury; firework injuries at Diwali, which produce a predictable annual surge affecting children and bystanders; bow-and-arrow, stone and stick injuries in rural children; acid attack, which is a devastating and characteristically Indian and South Asian form of assault; and injury from Holi colours and from cricket and badminton
• The BETT (birmingham eye trauma terminology) classification is the standard, and its value is that it is unambiguous. The whole eyewall — the sclera and cornea — is the reference tissue:

History and Examination

• The history determines the investigation, and three questions matter most:
• 1. What was the mechanism? — and specifically, was there hammering, chiselling, grinding, drilling or an explosion? A high-velocity metallic fragment produces a tiny, self-sealing entry wound and a comfortable, white eye with good vision. This history, not the appearance, is what leads to the radiograph
• 2. When did it happen? — for the timing of surgery, the risk of infection and the medicolegal record

Immediate Management and Prognosis

• IN A suspected open globe, the immediate measures are: a rigid shield (a plastic shield, or an improvised one from a paper cup) taped over the orbital rim so that NO pressure reaches the globe; nil BY mouth; systemic antibiotics; tetanus prophylaxis; antiemetics, because vomiting raises the intraocular pressure abruptly and can expel contents; analgesia; and strict instruction not to rub, press or squeeze
• Avoid — topical ointment (which may enter the eye); a pressure pad; tonometry; gonioscopy; scleral indentation; and depolarising muscle relaxants (suxamethonium) at anaesthesia, which raise the intraocular pressure
• The ocular trauma score gives a numerical prognosis from six variables: presenting visual acuity (much the most important), globe rupture, endophthalmitis, perforating injury, retinal detachment and a relative afferent pupillary defect. It is useful for counselling, and for documenting expectations at the outset
• Poor prognostic features — poor presenting acuity; an afferent pupillary defect; a posterior (zone III) wound; a wound longer than 10 mm; vitreous haemorrhage; retinal detachment; endophthalmitis; and a perforating injury with an exit wound
• Every penetrating injury carries the risk of sympathetic ophthalmitis.
• Documentation is part of the treatment — a drawing, the acuity of both eyes, the mechanism in the patient’s own words, and photographs where possible; these injuries frequently generate compensation and criminal proceedings
• Rupture is inside-out and laceration outside-in, which is why a blunt injury tears the eyewall at its weakest points
• Penetrating means entry only and perforating means entry and exit, a distinction commonly muddled and carrying a far worse prognosis
• A previously operated eye ruptures with far less force, and an old cataract section may give way decades later
• The sclera is thinnest behind the rectus insertions at 0.3 mm, which is where an occult rupture is most often found
• Zone III injuries carry the worst prognosis, extending more than 5 mm behind the limbus into the posterior segment
• Test the pupils before dilating; an afferent defect is the strongest single prognostic sign and is destroyed as information by mydriatics
• Record projection of light in four quadrants where the acuity is perception of light only; it guides both prognosis and surgical planning
• Never use suxamethonium in a suspected open globe; the depolarising block raises the pressure and can expel contents
• Give an antiemetic in an open globe injury; a single episode of vomiting can expel the intraocular contents
• Avoid B-scan in a suspected open globe; the probe pressure is dangerous and CT answers the question instead