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- Age-related macular degeneration
- Charles Bonnet syndrome
The Charles Bonnet syndrome (CBS) is characterised by vivid, complex and recurrent visual hallucinations occurring in psychologically normal people, and it is often associated with vision impairment.1 No effective treatment of CBS has been identified. We investigated whether intravitreal ranibizumab therapy for neovascular age-related macular degeneration (AMD) affects symptoms of CBS.
Over a 3-month period, we asked all patients with neovascular AMD midway in treatment course with ranibizumab (n=220) about CBS symptoms using the following question: ‘Some patients with the same disease as you have report seeing things which they know are unreal. Have you experienced this?’2 A positive answer led to further questioning about the nature of the hallucinations. Patients with obvious signs or medical records of dementia were excluded, as were patients reporting only flashes of light or shadows. We asked retrospectively if treatment had altered their hallucinatory experiences in relation to changes in frequency, length or intensity. Initial and current Snellen visual acuity were recorded. Minimum angle of resolution (logMAR) values were calculated to compensate for the non-linear scale of the Snellen chart.
All participants gave informed consent. Since the data were not normally distributed, differences among all groups were tested using the Kruskal–Wallis test, and differences between two groups using the Mann–Whitney test. A significance level of p<0.05 was employed.
Twenty-two patients were categorised as having CBS.3 The median age of the patients was 79.5 years (64–92 years). The female/male ratio was 73%/27%. One patient received bilateral treatment, and we treated each eye individually. The initial Snellen median visual acuity for all patients on the treated eye was 0.2 (range 0.05–0.63) logMAR −6.5 (range −1.3 to −0.2) and on the untreated eye 0.2 (range 0.1–1) logMAR 0.7 (range −2–0). After treatment, the median visual acuity for all patients on the treated eye was 0.25 (range 0.05–0.95) logMAR −0.6 (range −1.3–0). The median number of treatments with ranibizumab was 6 (range 3–13 months). The median follow-up was 11 months (range 4–33 months). Fourteen patients (64%) reported no difference in hallucinatory experiences following treatment; three (14%) worsening and five improving (23%). In the latter group, three reported a decrease in frequency of symptoms, one a decrease in intensity and one a complete resolution.
We found that patients who reported an improvement in CBS symptoms after treatment with ranibizumab also experienced a significant different increase in visual acuity compared with both patients who reported no change in CBS symptoms (Mann–Whitney p=0.027) and patients who reported worsening of CBS symptoms (Mann–Whitney p=0.022) (table 1).
In the group with unchanged symptoms, four patients still had active disease; in the group with worsened symptoms, two had active disease; and in the group with improved symptoms, none had active disease. When excluding patients with active disease from analysis, the patients with improved symptoms of CBS still had a significantly better visual outcome after treatment (p<0.05; Kruskal–Wallis).
As the assessment is retrospective, the possibility that patients experiencing vision improvement may be biased towards a favourable report of their hallucination outcome exists. No differences among the groups in final visual acuity measurements, age, gender, follow-up length, length of time with CBS symptoms and number of treatments were found (data not shown).
Spontaneous improvement has been reported in CBS.4 Our observed improvement of CBS was related to treatment efficacy, making it unlikely that our findings reflect spontaneous recovery.
We suggest that CBS symptoms can improve if visual acuity improves, supporting previous findings where cataract surgery or other methods of increasing vision through visual aids improved CBS symptoms.5 These data support current theories and evidence on the ‘deafferenting theory,’ where hallucinations would be expected to improve with recovery of vision.6
Competing interests None.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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