One million anonymised eye scans from Moorfields Eye Hospital will be used to train an artificial intelligence (AI) system from Google.
Machine learning algorithms will scour the images for signs of diseases such as macular degeneration and diabetes-related sight loss.
Moorfields is teaming up with Google's AI division DeepMind during the scheme.
Previously, DeepMind faced criticism over a little-known data sharing agreement with three London hospitals.
An agreement to share patient data from the Royal Free, Barnet and Chase Farm hospitals over the past five years and continuing until 2017 was revealed by the New Scientist in May.
In that case, Google said it was analysing kidney data in the hope of developing an app for medical staff.
The app, called Streams, would notify doctors should someone be at risk of developing acute kidney injury (AKI).
Announcing the latest venture with Moorfields, Google has cited the support of the Royal National Institute of Blind people (RNIB) and sight charities such as the Macular Society.
"How it plays out over time remains to be seen," Sam Smith, a co-ordinator at patient data campaign group MedConfidential, told the BBC.
"But you do have organisations involved that aren't principally concerned with DeepMind - they care about blindness in the case of RNIB and long term medical research in the case of the National Institute for Health Research."
"Maybe they have learnt the lessons of their Royal Free fiasco," the MedConfidential Twitter account tweeted, "Not that they've shared what they learnt from that..."
One tech journalist, Gareth Corfield, tweeted that he "hit the roof" after reading the news. He has written a letter to Moorfields citing the Data Protection Act.
"This is a serious dereliction of your duties as a data controller," he wrote.
"To be crystal clear, I have not consented for my personal data to be used by Moorfields NHS Trust for any purpose other than treating me for genuine medical purposes."
However, current rules state that as long as data is anonymised it may be shared for ethically approved projects.
Moorfields has published a Q&A on the DeepMind collaboration which adds, "patients can opt out of any data-sharing system by emailing the Trust's data protection officer".
"Our research with DeepMind has the potential to revolutionise the way professionals carry out eye tests and could lead to earlier detection and treatment of common eye diseases such as age-related macular degeneration," said Prof Sir Peng Tee Khaw, director of the National Institute for Health Research Biomedical Research Centre in Ophthalmology at Moorfields Eye Hospital.
Google has said it is estimated that up to 98% of sight loss that is a result of diabetes can be prevented with early treatment.
Recently, Massachusetts General Hospital announced a collaboration with semiconductor firm Nvidia to develop new artificial intelligence techniques to improve the diagnosis of diseases.