It is more than a year since Ben John last played rugby union, but still he feels the effects of concussion.

On Tuesday, he retired from the sport aged just 27, with a series of head injuries taking their toll on the former Ospreys centre.

John still suffers headaches and sensitivity to light - even though he was last concussed on Boxing Day 2017 - and, perhaps most alarmingly, his is not a unique story.

Former Wales forward Jonathan Thomas and ex-Saracens lock Alistair Hargreaves are among those who have been forced to retire following head injuries, and rugby's cases of concussion continue to pile up.

Leigh Halfpenny, the Wales and British and Irish Lions full-back, has not played since a late tackle from Australia's Samu Kerevi in November, while fellow Wales international Ross Moriarty is currently sidelined for a similar reason.

Then there is another Lion, Justin Tipuric, who temporarily lost his sight after he was concussed in 2016, a year after Wales coach Warren Gatland had admitted he feared wing George North might have to retire if he suffered another head injury.

The list goes on and, for John, each example is a chilling reminder of his own ordeal.

"The last year or two has been really scary," he tells BBC Sport Wales.

"It's been tough, not just symptoms. It's been a rollercoaster of emotions."

John announced at the start of this season he would be taking a year out from rugby in an attempt to recover from the three head injuries he sustained during 2017.

The first was against Munster in February, the second against the Cheetahs seven months later and, after returning to the Ospreys team on Boxing Day, he suffered the third and ultimately decisive blow as he fell to the ground after contesting a high ball with Scarlets wing Steff Evans.

John thought a season away from the physical demands of professional rugby could help him make a full return but, during a recent fitness test, the ill effects he experienced told him otherwise.

"The last one, around eight weeks ago, was headaches and being sensitive to light," says John.

"The effects I had from the last concussion I had a year ago was the same but a lot more prominent.

"Bright lights, a lack of energy, a loss of concentration, always in a fog, but the worst for me was my vision - it was all blurry and my eyes couldn't focus very well."

Ben John was concussed after this challenge with Steff Evans, who John does not blame for his injury

'Halfpenny is doing the right thing'

These are symptoms most rugby players will recognise.

Since rugby union turned professional in 1995, factors such as the ever increasing size of players and busier fixture schedules have contributed to a huge surge in cases of concussion.

According to a report from the Rugby Football Union, Premiership Rugby and the Rugby Players' Association released on Wednesday, the most commonly reported Premiership match injury was concussion, contributing 20% of all match injuries.

Governing bodies have tried to manage the problem by introducing measures such as head injury assessments, heavier sanctions for high tackles and technology-fitted gum shields which allow head impact data to be transmitted immediately to medical staff on the sidelines.

Such innovations contributed to a small reduction in concussions for the 2017-18 season in English Premiership matches - compared with 2016-17 - of one fewer concussion every eight games.

But that is only a marginal change, considering a study in 2017 concluded that rates of concussion rose from 6.7 per 1,000 player hours in 2012-13 to 15.8 per 1,000 player hours in 2015-16 - or one brain injury every couple of matches.

John believes rugby must ease its increasingly congested calendar if it is to take care of its players.

"Rugby's a long old season, 11 months, and for the international boys, it's high intensity all the time," he says.

"The best way around that is shortening the season or maybe having a month's break in between, just to give people time to recover, not just from concussion but from all injuries."

It would appear rugby is beginning to appreciate the need for patience when bringing players back into the fold after a spell of absence through concussion.

Leigh Halfpenny left the field in the final minutes of Wales' 9-6 win against Australia in November 2018

Halfpenny is one of the most high-profile current examples, having seen his return to action delayed since suffering a head injury against Australia in November.

The 30-year-old has consulted a specialist and, although he is back training, he is likely to miss another three to five weeks.

Wayne Pivac, Halfpenny's head coach at the Scarlets, says: "He's as frustrated as anybody is, but his health and wellbeing comes first."

That is the kind of thinking which helped convince John to take the difficult decision to retire.

There is no suggestion that Halfpenny's problem is as serious, but John is encouraged that the Wales full-back is not rushing his return.

"What I've learned with concussion is that time is what heals it," John says.

"Leigh Halfpenny at the moment is doing the right thing. I haven't spoken to him yet but he's taken his time, he's not rushing back - his health is most important."

On one hand, retiring from rugby was a wrench for John but, with his and his family's wellbeing in mind, it was the only course of action to take.

John now lives with his wife in London, where he works as a personal trainer.

It is not necessarily how he envisaged his life when he was playing for the Ospreys but, after everything he has endured with concussion, John is relishing his fresh start.

"One thing that kept on driving me to come back and play was that I always wanted my Wales cap - that was my goal and motivation," he says.

"It was hard to let that go but hopefully the motivation I had for that I can put into my new line of work.

"I'm focusing on my personal training, and I do a bit of rugby coaching on the side.

"So whether I go down the coaching route or the fitness industry, I'm not 100% sure yet but I'm keeping all options open and seeing where it takes me."