A mother from Watford is getting ready to run 26.2 miles blindfolded to raise money for a charity that helps prevent sight loss.
Catherine Parsi will join thousands of runners at the London Marathon on Sunday April 13 with her guide and friend Phyllida Jones, from St Albans.
Mrs Parsi said her main inspiration is her daughter, Sienna, who is 16 months and is registered blind.
In November 2012 Catherine gave birth to Sienna and twin brother Joshua prematurely, at under 29 weeks pregnant. Sienna weighed 2lb and 6oz and Joshua arrived 15 minutes later, weighing 3lb and 2oz.
After complications and months in hospital Sienna was diagnosed with Retinopathy of Prematurity (ROP) in both eyes at 39 weeks old.
Mrs Parsi, who lives at Appletree Walk, said: "When the twins were born we were over joyed to welcome them into the world. Having to hear that your child may never experience sight was heart-breaking and it was an incredibly difficult time. It has been an emotional rollercoaster. My challenge in the marathon is nothing compared to what Sienna has to face every day.
"Sienna is wonderful. She doesn’t know any different. It is difficult for me as her mum to come to terms with it, knowing her sight is damaged. That is why I am running blindfolded. I want to see the world as Sienna sees it."
ROP is a disease of the eye affecting premature babies - generally those who have received intensive neonatal care where oxygen has been used. Due to disorganised growth of the retinal blood vessels it can result in retinal detachment, which is what happened to Sienna.
Despite having an operation, at Great Ormond Street Hospital, they were unable to correct her sight. Sienna is due for another operation in August to see if her sight can be saved.
Mrs Parsi, 32, continued: "I'm a keen runner and wanted to support Fight for Sight and the vital research work they do, to prevent other children losing their sight.
"We recently completed Watford half marathon which was a challenge because of the floods and hills.
"I am ready for this marathon physically, it is emotionally that I must prepare for. When I run it will bring everything back about Sienna, feeling which are still raw.
"I want to give back to the charity though who have been offered us support. I hope one day that treatment will be available to give Sienna sight."
Fight for Sight is the main UK charity dedicated to funding eye research to prevent sight loss
They fund more than £8 million of research at 35 universities and hospitals across the UK.
Julian Jackson, director of development at Fight for Sight knows first-hand the effects of sight loss having lost his sight four years ago to a condition called Retinitis Pigmentosa. He said: "A huge thank you to Catherine and all our other runners for taking part in this year's marathon and literally going that extra mile for Fight for Sight.
"For Catherine to run blindfolded is a huge personal challenge. We're so grateful for her support and wish her the best of luck."
Mrs Parsi has nearly raised £2,000. To donate visit: http://uk.virginmoneygiving.com/team/Siennas.World