Approved Research

Visual Impairment in Psychosis: Cause, Consequence, or Biomarker?

Lay summary

Eyesight Problems and Psychotic Illnesses: What's the Link?

Psychotic illnesses affect about 1% of people. Symptoms include hearing voices and having confusing and distressing thoughts. These can have a large effect on people's lives.

People with psychotic illnesses seem to have more eyesight problems. We don't know why. Here are three possible reasons:

1: They find it hard to look after their eyes. For example, it might be harder to get to the optician's.

2: They have brain changes that cause both eyesight problems and psychotic illnesses.

3: Eyesight problems increase someone's chances of having a psychotic illness.

I plan to look at which of these reasons best explains why eyesight problems and psychotic illnesses occur together more than would happen by chance.

If people with psychotic illnesses have less good eye care, we need to improve this.

If the same brain changes are causing poor eyesight and psychotic illnesses, this would teach us more about the causes of psychotic illnesses.

If eyesight problems lead to psychotic illnesses, then improving eye health could help to prevent or treat psychotic illnesses.

I will look at two large datasets to test these theories: The UK Biobank and the UK Genomics Consortium. Genes are present before birth, so are decided before any psychotic illness develops. I will see if people with genes for short-sight have more psychotic illnesses. If they do, this suggests that poor eyesight increases a person's chances of getting psychotic illnesses. I will also find out if genes for psychotic illnesses are linked with eyesight problems. This would suggest the reverse: that people with psychotic illnesses have a higher chance of developing poor eyesight.

I will chair an advisory group every 6 months. People with psychotic illnesses and people with eyesight problems will be members and will help to decide how the research is run. The group will also include carers, charity members and doctors. We will discuss how to use any results to improve healthcare for people with eyesight problems and psychotic illnesses.

After 18 months the research should be finished. I will tell healthcare professionals and researchers about my results at meetings and in journals. I will write about them in publications aimed at people with mental health and eyesight problems. I will also present findings to public groups, through links with the Royal National Institute for the Blind (RNIB) and a forum of mental health service users.

Previous scope:

Research Question: Is visual impairment a cause, consequence, or biomarker of psychotic illness?

Aims:

To use data from the Psychiatric Genomics Consortium (PGC) and UK Biobank to test three hypotheses:

1. a)           Single Nucleotide Polymorphisms (SNPs) associated with reduced visual acuity in the UK Biobank are associated with a diagnosis of psychotic illness in the PGC.
2. b)           SNPs associated with a diagnosis of schizophrenia in the PGC are associated with reduced visual acuity in UK Biobank.
3. c)    Measured visual acuity in the UK Biobank is correlated with odds of reporting a psychotic illness diagnosis and this varies according to cause of visual impairment.

New scope:

Hypothesis 1: An association will be seen between psychotic illnesses and poorer subsequent visual acuity and reduce thickness of retinal structures at baseline OCT measurement.

Exposure Variable

*            ICD10 diagnosis F20-29 prior to 2006 from linked hospital records.

Outcome Variables

*            Visual acuity measured by final right eye and left eye LogMAR scores at baseline as a continuous variable.

*            Macular thickness on baseline OCT scan

*            Macular volume on baseline OCT scan

*            Retinal pigment layer thickness on baseline OCT scan

Hypothesis 2: Reduced macular thickness, macular volume, and retinal pigment layer thickness on OCT scan in 2009-2010 will be associated with increased odds of reporting psychotic experiences in 2016.

This will be mediated by cognitive impairment.

Exposure variables

*            Macular thickness on baseline OCT scan

*            Macular volume on baseline OCT scan

*            Retinal Pigment Epithelium (RPE) thickness on baseline OCT scan

Outcome Variable

*            Reporting psychotic experiences on questionnaire in 2016

Putative Mediator

*            Composite cognitive function score from baseline measuresPutative Mediator

*            Composite cognitive function score from baseline measures