A near-blind Southfields woman who was denied sight-saving treatment by Wandsworth Primary Care Trust (PCT) will join a protest outside the High Court on Thursday during the hearing of a landmark case.

Joan Armstrong, 82, of Wimbledon Park Road, has macular degeneration in both eyes and will travel to central London in support of the Royal National Institute of Blind People (RNIB) in a fight against Warwickshire PCT.

If judges decide the Trust's failure to provide sight-saving treatments is illegal, it will set a precedent obliging Wandsworth PCT to give Mrs Armstrong and other Wandsworth residents the treatment they need.

Her son Martin, who will accompany her, said: "It's got to the stage now where I know it's not only my mother affected. I'm able to defend my mother but there's a lot of people who live alone who can't defend themselves and can't afford a lawyer, which is why the RNIB is doing this on their behalf."

The case involves three Warwickshire pensioners who suffer from the same disease as Mrs Armstrong are distraught at the thought of going blind as a result of the NHS refusing to fund their treatment.

This is the first time the RNIB has backed a High Court case and it is covering the legal costs of two of the claimants, as well as providing instruction to the national law firm Irwin Mitchell.

Steve Winyard at the RNIB said: "Warwickshire PCT claim to be operating a policy where they consider treatment on an individual basis. But as far as we understand they have not funded a single case of anti-VEGF treatment, rejecting over 50 appeals by patients in their care."

Macular degeneration is the leading cause of sight loss in the UK and if left untreated, can lead to blindness in as little as three months.