1. Seasonal variation of incidence
Medically unexplained visual loss A prospective observational study of incidence, diagnostic workup and outcomes
Daniel MC1, Blackshaw L1, Dahlmann-Noor A1
1 NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK; correspondence:
Background
MUVL: conversion disorder; visual loss/symptoms without any lesion of the eyes and visual pathways
Reported incidence: 1 to 1.75% [1, 2]
Associated conditions: psychosocial disorders (stress at home/school), psychiatric disorders (neurotic or hysterical personality, anxiety, depression), physical/sexual abuse, history of ophthalmological/neurosurgical procedures, physical illness [1, 3]
Reported resolution rate at 12 months: 37-73% [1,4]
Purpose
To describe the incidence, diagnostic workup, clinical characteristics and outcomes of children age 3 to 16 years presenting at our consultant-led children's eye casualty with suspected MUVL
Methods
Prospective observational service evaluation
We included all children with suspected MUVL presenting over a 12-month period, starting on 01/01/2015.
Cases were identified prospectively by the A&E nurses, and retrospectively by searching the electronic patient record system.
We reviewed all medical records at three months after initial presentation.
As denominator, we used the number of new patients attending our casualty clinic over the same time period (n=2,397).
Table 1. Number of children diagnosed with MUVL, demographical and clinical characteristics.
Seasonal variation of incidence
Results
We identified 91 cases of suspected MUVL; we excluded 5, as other diagnoses were established during follow-up visits. We included 86 cases in the analysis. The annual incidence in our setting was 3.6%. Median age at presentation was 9 (interquartile range 7 to 12) years. 54 patients were girls (63%). The median number of appointments was 2 (interquartile range 1 to 3); the median duration of follow-up was 36 (interquartile range 0 to 161) days (Table 1.).  There was seasonal variation in incident numbers, with peaks in the winter months and in early summer (Fig. 1). There was considerable variability in diagnostic investigations. No child was referred for psychological assessment or support.
Fig 1. Peaks in the winter months and spring.
Conclusions
Incidence is far higher and resolution far lower than previously reported. Incidence peaks prior to and during school assessment periods and during the winter months, when seasonal affective disorders may be more common. Children and their families may benefit from a referral to psychological services to reduce the duration of symptoms and the risk of further psychological problems.
Acknowledgments We thank the nurses in paeds A&E for their support. The authors have no financial interests to declare. The study was not supported by specific funding. MCD is employed by the National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, and as such the work was supported by the NIHR. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.
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