Sir,

Intraocular foreign bodies are a common and potentially devastating sequelae to the impact of high velocity solid objects upon the globe. Here we report the unusual finding of small gas bubbles closely related to the location of the foreign body, but well away from the site of entry. The possible origins of the bubbles are discussed in relation to the clinical picture.

Case report

A 25-year-old male was admitted having been hit in the right eye by an object dislodged whilst hammering a metal machine punch. The patient complained of right visual blurring and his initial Snellen visual acuities were 6/9 in the right eye and 6/5 in the left. Ocular examination revealed a 1.5 mm conjunctival laceration immediately temporal to the limbus, with surrounding subconjunctival haemorrhage obscuring view of the underlying sclera. There was a mild cellular response in the anterior chamber, and intraocular pressures were 11 and 19 mmHg in the right and left eyes respectively. Fundoscopy revealed a small area of pre-retinal haemorrhage overlying the infero-nasal vessels, with blood extending from this site antero-inferiorly into the vitreous (Figure 1). Of particular note were a number of bubbles lying adjacent to the retina in the posterior vitreous, and superior to the above retinal lesion. These bubbles were only present in this one location, and slowly reabsorbed over the next 48 h. Plain radiographs of the orbits suggested the presence of a radio-opaque foreign body within the right eye, and this was supported by CT scan. The patient was therefore commenced on oral ciprofloxacin 750 mg b.d. and two hourly Predforte drops, together with topical Chloramphenicol and Atropine. By day 4 a metallic foreign body could be observed within the clot overlying the area of preretinal haemorrhage, and this was subsequently removed during a pars plana vitrectomy (Figure 2). Although the postoperative recovery was complicated by further vitreous haemorrhage, the patient made a good visual recovery with an acuity of 6/9 when discharged 6 months later.

Figure 1
figure 1

Fundus photograph taken on day 1 showing area of preretinal and intravitreal haemorrhage with associated gas bubbles.

Full size image
Figure 2
figure 2

The metallic foreign body recovered from the patient.

Full size image

Comment

The presence of free gas bubbles within the vitreous following the passage of a high velocity fragment has not been previously reported to our knowledge, and it is interesting to speculate on the origins of the bubbles seen in this patient. Free gas bubbles associated with both Clostridia sp and Bacillus cereus panophthalmitis have been reported, but such cases involved extensive inflammation with necrosis throughout the globe.1,2,3 In this case there was no evidence of vitritis and the bubbles were present within 1 h of injury, and it is therefore likely that the presence of the bubbles was related to the passage of the metallic fragment as it passed into the eye. A number of possible mechanisms for this can be postulated. Firstly the low pressure zone immediately following a high velocity projectile would draw air in its wake down an induced pressure gradient. This could have resulted in air being drawn into the eye, although the absence of air at the entry site or related to the path between this and the presumed site of impact is against this. The second possibility is that the bubbles represent the result of cavitation induced by the passage of the solid fragment through the semi-liquid vitreous medium.4 A low pressure region in the wake of a fast moving object can result in dissolved gases coming out of solution. Again though, it is odd that they are solely related to the final resting site of the fragment. Thirdly, a thermal or chemical reaction between the fragment and the vitreous gel could result in the liberation of free gas, and this cannot be excluded.

It therefore remains uncertain as to the exact mechanism that induced this interesting phenomenon. The authors would be pleased to hear of any further cases where similar findings were observed.