Staphyloma causing visual field defect, illustrating the risk of globe perforation with sharp-needle anaesthesia

Sir,

A 66-year-old man was investigated for an asymptomatic right-sided visual field defect (Figure 1). The right eye was blind following a failed buckling procedure (retinal detachment attempted correction procedure). The left eye had an axial length of 28 mm (96% of eyes are between 21 and 25.5 mm) and had been highly myopic (−15 dioptres) before cataract surgery.

Figure 1

Goldmann visual field plot with nasal scotoma in the left eye. The right eye has no perception of light.

Fundoscopy revealed a temporal staphyloma in the left eye (Figure 2). Staphylomata are most often encountered around the optic nerve of highly myopic eyes. They are bulgings of the sclera of the posterior pole of the eyeball and are associated with degenerative changes in severe myopia. Magnetic resonance imaging illustrates a globe that is longer and wider than average (temporal staphyloma). Figure 3 also demonstrate the failed buckling procedure in the right eye. Staphyloma is a recognised cause of field defects;² No other cause for the field defect was detected.

Figure 2

Composite fundal photograph, showing the staphyloma (shown as pearly-white cystic structures on the right of the composite photo) at the temporal side of the left eye.

Figure 3

(a) Magnetic resonance imaging of the brain and orbits, illustrating the large left eye with bulging of the temporal (left) side. No other pathology apart from the staphyloma seen in the left eye. (b) Note also the right intraocular lens implant and ‘funnel’ retinal detachment with failed scleral buckling (retinal detachment attempted correction procedure) in right eye.

It is well known that the incidence of staphyloma increases with increasing axial length. It is likely that nearly all eyes with pathologic myopia have some form of posterior staphyloma. Owing to their resulting bulging shape, eyes with staphylomata are prone to globe perforation with needle local anaesthesia (retrobulbar or peribulbar anaesthetic³). Preferred techniques that minimise this risk or overcome the problem completely include topical, sub-Tenon's or general anaesthesia.^{1, 4}