Trauma-induced filtering bleb formation and blebitis 40 years following a penetrating eye injury

Discussion

To our best knowledge, spontaneous filtering bleb is of rare occurrence and only a handful of cases have been reported to date. It is typically observed in patients with connective tissue disorders and patients with ocular abnormalities such as Axenfeld syndrome and Terrien marginal degeneration.3 4 Nemet et al reported the first case in a patient with Axenfeld syndrome postulating raised IOP as a causative factor of rupture of corneoscleral junction with subsequent formation of filtering bleb.3 5 Diseases of the peripheral cornea such as Terrien and Pellucid marginal degeneration resulting in rupture of the Descemet’s membrane are also known causes of spontaneous bleb formation.3 4 Khouri et al described a traumatic cause of filtering bleb many years after penetrating glass injury to the eye, with an apparent posterior communicating channel between the bleb and cilliary body on ultrasound biomicroscopy.6 This case is interestingly very similar to ours, except that our patient presented with blebitis—a potential complication of bleb formation (both spontaneous and surgical).

Blebitis was first described in 1994 as presumed infection of a filtering bleb with minimal or no anterior chamber reaction without vitreous involvement.7 According to Shaarawy and colleagues, the mechanisms causing blebitis remain largely unknown. In an early-onset bleb-related infection following a glaucoma filtration surgery, pathogens are likely to be introduced perioperatively or during the early postoperative period. The pathogenesis in a late-onset bleb-related infection is more likely associated with the barrier functions (both physical and immunological) of the conjunctiva and the virulence of invading organism. In this case, the patient developed blebitis during his 2-week vacation in a high ultraviolet (UV) environment which could have potentially suppressed his immune system causing invasion and proliferation of microorganism in this vulnerable area.8 Risk factors of increased bleb-related infections include bleb leak, recurrent blepharitis, conjunctivitis, ocular surface disease, inferior or nasal bleb and thin, cystic bleb. Younger age, male, diabetes, malnutrition and poor immune system are also important risk factors.2 8 9 In our case, the location of the thin cystic bleb was between 9 o’clock and 11 o’clock position however most surgical blebs are located between the 11 o’clock and 1 o’clock position. Surgical bleb also differ from traumatic bleb as they have a partial thickness scleral flap. Early diagnosis and management is vital with aggressive topical treatment targeting common pathogens in blebitis like Staphylococcus aureus and Staphylococcus epidermidis. Options include fluoroquinolones or fortified topical antibiotics such as vancomycin or cefazolin in combination with an aminoglycoside. A randomised control trial published by Cantor et al reported that topical levofloxacin provide better aqueous penetration compared with ofloxacin and ciprofloxacin eye drops in eyes with functioning filtering bleb.10 Nonetheless, our patient responded well with topical ofloxacin monotherapy. We also prescribed topical cyclopegic (mydrilate 1%) as a supportive measure to relieve pain and to prevent anterior-segment inflammation-related posterior synaechiae.11 Although there is no standard treatment regime of blebitis among glaucoma consultants, successful treatment will ensure good visual outcome. However if left untreated, blebitis may lead to bleb-associated endophthalmitis manifesting with severe pain, markedly reduced vision and vitreous inflammation.2 The use of prophylactic antibiotics is not recommended, but the management of ocular surface disease may play a key role in enhancing conjunctival resistance.8

Although our patient has been asymptomatic without bleb dysesthesia and with good IOP control, patients with filtering conjunctival bleb should be routinely observed to look for blebitis and bleb-associated infections. Disruption of globe integrity can cause bleb leak resulting in low IOP. This can subsequently cause hypotony maculopathy when IOP reduces to 4 mm Hg and below thereby affecting vision. Should this occur, dehiscence of old scleral scars can be repaired by tightly suturing the sclera, or by using amnion membrane, conjunctival rotation flap or scleral patch.12 Therefore, ultrasound biomicroscopy should be performed and documented for surgical planning if repair becomes necessary.6