Stuart Hogg was warned that he risked losing his sight if he absorbed a further blow to his cheek injury.
Scotland full-back Hogg will miss the rest of the British and Irish Lions tour after sustaining a “facial bone fracture” during Saturday’s 12-3 win over the Crusaders.
Hogg collided unwittingly with Conor Murray’s elbow as the Ireland scrum-half sought to let the Glasgow star launch a counter-attack in the first half of the Crusaders clash.
The Lions hope a replacement will not be needed, but head coach Warren Gatland admitted they canvassed four specialists before ruling Hogg out of the rest of the New Zealand tour.
“It was just a freak accident,” Gatland told Sky Sports ahead of Tuesday’s Highlanders clash. “He’s absolutely gutted. We’re feeling for him.
“We saw about four different specialists: one of them said he’d be alright and another said it’s potentially serious and that he could lose his sight if he plays.
“We told him it was only a game of rugby and he understood that.”
Hogg revealed that he cried upon hearing the news that he must return home.
“I am absolutely devastated to be leaving the Lions,” Hogg told the Daily Telegraph.
“It means everything to me to be part of this tour and when, on Monday night, I first got the news that I had suffered a facial fracture and had to come home, I cried.
“I have done several times since then, too. It is tough, really tough, to take. As much as I love being at home, I do not believe I am ready to go.
“It still has not quite sunk in yet that I am going. I feel my game has been getting better and better in New Zealand and was a lot more confident going into the second game against the Crusaders.”
Defence coach Andy Farrell suggested on Monday that the tourists already have enough options to offset Hogg’s absence.
“It is hugely disappointing for Stuart to have to return home early and for us to lose one of our touring party,” said Gatland.
“Stuart has been a key member of our squad on and off the field and it is disappointing to see injury cut short his time with us in New Zealand.
“We all wish him the best with his recovery and we look forward to seeing him back in action in the future.”
Hogg would have been one of the main backline talents Gatland could have expected to deliver the X-factor attacking play he has been seeking in New Zealand.
Ireland’s versatile backline operator Jared Payne wore the 15 shirt against the Highlanders, while Leigh Halfpenny ought to be favourite to start at full-back for the Test series.
England’s Elliot Daly and Wales’ Liam Williams can also operate at full-back, while speed king Anthony Watson showed up well in the role against the Crusaders after Hogg’s injury.