Sir,

Formed visual hallucinations with retained insight and cognition or Charles Bonnet syndrome (CBS) is known to occur after ocular surgery, albeit rarely.1 We report an unusual case of CBS following macular hole (MH) surgery.

Case report

An 82-year-old Chinese woman presented with a best-corrected visual acuity of 6/120 in her right eye due to an idiopathic stage IV MH. The left eye had a best-corrected visual acuity of 6/12. She had no psychiatric illness or organic neurological disease.

She underwent surgical repair of the MH with three-port pars plana vitrectomy, internal limiting membrane peeling, and fluid–gas exchange with 16% perfluoropropane (C3F8) internal tamponade. The surgery was uneventful. She was instructed to position her head face-down for 2 weeks postoperatively.

At 2 days after the operation, she complained of ‘seeing’ ants crawling on the bed, kittens, and people when these were not actually present. She did not hear voices associated with these images. She was aware that these images were not real. Her vision was counting fingers and the eye had a near full fill of the gas with an attached retina. There were no similar complaints in the past. She was conscious, well-oriented, and had an intact memory. Her visual hallucinations stopped on the eighth postoperative day when the gas bubble had reduced to 80% and her vision had improved to 6/120. The MH was successfully closed and her vision improved further to 6/12 four months postoperatively.

CBS usually occurs in elderly individuals with severe visual impairment1, 2 and has been reported in a variety of ocular pathologies and following procedures such as laser peripheral iridotomy and macular translocation (MT) surgery.1, 3, 4, 5 The prevalence of CBS ranges from 0.4 to 13% in various study populations,2 but its incidence following ocular surgery is not known.

Two cases of CBS after MT surgery have provided the strongest direct observation supporting the ‘sensory deprivation’ theory for CBS.4 The visual hallucinations in these patients started within 24 h after MT and ceased after retinal reattachment and visual improvement 3 and 7 days later, respectively. Our patient developed hallucinations in the early postoperative period when her vision worsened owing to the intravitreal gas. These hallucinations ceased with a decrease in the size of the gas bubble and improvement in vision. The acute reduction in vision rather than the low visual acuity itself may have triggered the visual hallucinations, as suggested by Shiraishi et al.5

Our patient had good visual acuity in the left eye. Although CBS occurs more commonly in patients with bilateral visual loss, it has been reported in the presence of good visual acuity in the better seeing eye.1, 2, 4 The postoperative prone positioning may have contributed to the occurrence of hallucinations owing to occlusion of vision in the better eye in our case. This report extends the spectrum of ocular procedures associated with CBS.