NCT02392468

Who might be able to join this trial:

If you have schizophrenia:

• You have a confirmed diagnosis of schizophrenia and have been in a stable, non-acute phase of your illness for at least 8 weeks before joining.
• You have been on your current antipsychotic medication (a newer type, but not Clozapine) at the same dose for at least 8 weeks, OR on an older type of antipsychotic at the same dose for at least 6 months.
• Any other psychiatric medications you take (apart from anti-seizure drugs and lithium) have been at a stable dose for at least 8 weeks; anti-seizure drugs and lithium are allowed if you have been on them for at least 6 months.
• Your hallucinations and delusions are rated no more than moderate in severity (confirm with trial site).
• Your disorganised thinking is rated no more than moderate in severity (confirm with trial site).
• You have minimal movement side effects from medication and mild or moderate depressive symptoms at most (confirm with trial site).
• You are between 18 and 55 years old.

If you have Alzheimer's disease:

• You have a confirmed diagnosis of mild Alzheimer's dementia.
• Your score on a standard memory and thinking test (MMSE) is between 18 and 26 out of 30.
• You are between 55 and 85 years old (those over 85 may still be considered based on overall health, at the doctor's judgement).
• You have either not taken common Alzheimer's medications (such as donepezil, galantamine, rivastigmine, or memantine) for at least 3 months, or you have been on a stable dose of these medications for at least 3 months.
• You have a recent brain scan (CT or MRI) from within the past year, or you are willing to have one done at the screening visit.
• A carer or support person may be present with you during study visits if needed.

If you are a healthy volunteer:

• You are a male or female aged 18 to 85 years in good general health (those over 85 may be considered based on overall health, at the doctor's judgement).
• Your age will be matched to other participants in the study as the trial progresses (confirm with trial site for current availability).

For everyone:

• You are able and willing to follow all study procedures reliably.
• You have signed and dated a consent form before your first visit; if you have a legal representative, they must also give written consent.

Who may not be able to join:

• You have an active eye condition (such as cataracts, glaucoma, diabetic eye disease, or an eye infection) in one or both eyes.
• You are planning to have eye treatment or eye surgery during the study.
• You are currently using or plan to use steroid medications (as eye drops or taken by mouth/injection).
• You are currently using or plan to use medications known to be harmful to the eye or optic nerve.
• You are taking more than two antipsychotic medications.
• Your Alzheimer's diagnosis is caused by another condition rather than Alzheimer's disease itself.
• You have another neurological condition such as Parkinson's disease, epilepsy, multiple sclerosis, stroke, Huntington's disease, or vascular dementia.
• You regularly need strong sleeping pills or anti-anxiety medications (such as diazepam).
• If you have Alzheimer's disease, you have taken certain antidepressants (tricyclics or MAOIs), certain antipsychotics with strong anticholinergic effects, anticholinergic medications, St. John's Wort, carbamazepine, or Ginkgo extract within the past 3 months.
• You have significant blood vessel disease in the brain linked to memory or thinking problems.
• You have had serious thoughts of suicide in the past 3 months (confirm with trial site).
• You have made a suicide attempt or taken steps toward one in the past 2 years.
• You have an unstable or uncontrolled serious health condition affecting the gut, liver, kidneys, lungs, heart, immune system, blood, or hormones.
• You are a woman who is pregnant, breastfeeding, or of childbearing age and not