Sir,

Many of the complications of cataract surgery have been solved through the evolution of surgical and anaesthetic technique. The majority of cases today are performed as a day case under local anaesthetic, which may be administered topically, in to the Sub-Tenon's space or given as peribulbar block. The safety and efficiency of Sub-Tenon's anaesthesia is well documented.1 We present an unusual complication of Sub-Tenon's anaesthesia following routine cataract surgery.

Case Report

A 69-year-old man presented, 18 days following uncomplicated cataract surgery under Sub-Tenon's anaesthesia, with a 2-week history of a painless red eye. He had been picking blackcurrants at the onset of symptoms. He was known to be on long-term warfarin therapy following an aortic valve replacement. On examination his best-corrected Snellen visual acuity was 6/6 and a nasal subconjunctival haemorrhage was noted (Figure 1a). Slit-lamp examination revealed an intact subconjunctival insect associated with the subconjunctival haemorrhage located above the area that the Sub-Tenon's anaesthesia had been administered (Figure 1b). The rest of the ocular examination was normal. An uncomplicated removal of the insect was performed via a small conjunctival incision and the subconjunctival haemorrhage resolved. The insect has been identified as a Thrips (order Thysanoptera meaning ‘fringed wings’). Although tiny they may occur in large numbers, and are also know as ‘thunder flies’ because they often fly on warm, still (eg prethunder-storm) days. Thrips commonly inhabit flowerheads and feed on plant sap.

Figure 1
figure 1

Subconjunctival haemorrhage adjacent to the entry site of the Sub-Tenon's anaesthetic block. When viewed with higher magnification a small subconjunctival insect could be seen, this was later identified as ‘Thrips’.

Comment

Sub-Tenon's anaesthesia is an established and safe technique but involves incising the conjunctiva to access the Sub-Tenon's space, if as in this case the incision is large and sited too anteriorly it presents a potential porthole for unwanted foreign bodies.1, 2 There have been numerous case reports of the consequences of injury from hymenopteran insects, caterpillar setae, and insect wings.3, 4 However, we understand that this is the first report of insect entrapment in the subconjunctival space following Sub-Tenon's anaesthesia. Following cataract surgery, patients are instructed not to rub their eyes. This may explain why the insect was not wiped away after initial entrapment. Subconjunctival haemorrhages are common in patients taking oral anticoagulants who undergo Sub-Tenon's anaesthesia, and this presents as an unusual precipitant. Care should be taken when administering Sub-Tenon's anaesthesia to ensure that the conjunctival incision is small and sited correctly so as to minimise the potential complication of foreign bodies as illustrated in this case.