Family, friends and well wishers gathered for the special occasion at the North Shore Hotel on Saturday.
Ryan, from Chapel St Leonards, has defied medical opinion since suffering severe brain injuries in a cycling accident in July 2013 while not wearing a protective helmet.
He returned to the family home in September after months of rehabilitation at the Children’s Trust specialist centre in Surrey and now attends St Francis School in Lincoln.
The 18th birthday celebration featured casino tables, music and an eye-catching roulette wheel cake created by baker Kelly Saunders.
Video messages of congratulation were also screened from celebrities including comedian Tim Vine, Spandau Ballet musician and former EastEnders star Martin Kemp and 200m Paralympic champion Richard Whitehead, who described Ryan as his ‘inspiration’.