Lockyer was poised to return to Wales charge before crashing out in the Championship final play-off at Wembley in May.
However, Leeds United’s Dan James has been knocked out due to injury.
Meanwhile Page has added the uncapped trio of Tom King, Morgan Fox and Liam Cullen and withdrawn Josh Sheehan.
Queens Park Rangers defender Fox got his call-up aged 29 and 24-year-old Swansea City striker Cullen also has the chance to thrive at international level.
Winger James has an abductor problem.
Bolton Wanderers’ Sheehan, 28, returns in 2021 after last being involved with Wales.
Wolverhampton Wanderers goalkeeper King played for England at boy-grade level, but qualified for Wales through his Welsh father.
Lockyer suffered from atrial fibrillation, a condition described by the NHS as “an irregular and often abnormally fast heart rate”.
Centre-back Lockyer has not played for Wales since September 2021, although he was part of their squad for last year’s 2022 World Cup as well as Euro 2020.
He was named in the Championship Team of the Year after helping Luton reach the Premier League for 2022–23.
Lockyer spent his entire career below the top flight before being promoted.
Page said: “It’s a great story. We’ve all seen the events of the play-off final. We’ve all been concerned, but since that day there’s been nothing but positivity.
“He’s got some great news, he’s back to normal and now playing in the Premier League, which is incredible for him too.
“It’s always going to be a challenge when you get promoted to the Premier League, Luton have done really well to be where they are with the resources available to them.
“But for him personally he should be very proud of how he recovered after that. It was a dream for him to play in the Premier League and he achieved that.”
The Wales boss does not believe James’ injury is “too serious”.
“But it gets him out of this camp, unfortunately,” Page said.
“It’s probably a three-week injury so we can push and push him, but we won’t get him at his best. And it will be like pushing him the day before the Latvia game.
“I don’t think Leeds will want that and we need people on the grass fit and ready to go because it’s definitely an important game for us.
“We looked at the scan results and in the end it was an easy decision for us to release him.”
Wales return to action with a friendly at Cardiff City Stadium against South Korea on Thursday 7 September, before the Euro 2024 qualifiers in Latvia four days later.
Wales have won just one of their last 12 games, with losses to Armenia and Turkey in June severely damaging their hopes of qualifying for Euro 2024.
Wales are fourth in the five-team Group D, with just one win from four matches leaving them with slim hopes of automatic qualification and relying on the play-offs in March to reach next year’s tournament in Germany.
Football Association of Wales (FAW) bosses conducted reviews of defeats against Armenia and Turkey – as they do after every international window – and decided to stick with Page.
Page accepted “full responsibility” for his team’s plight and hopes his players’ match fitness has improved following concerns over a lack of game time for their clubs.