Musgrove Park Hospital said the cause of the "technical issues" in the hired facility was being investigated.
Surgery was carried out on 62 patients with just under half reporting complications while some 15 people had "more significant" corneal issues.
The use of the mobile facility was ceased when the issues were discovered.
All affected patients have been spoken to and care plans are now in place for their ongoing treatment, a hospital spokesperson said.
Vanguard Healthcare had been hired to provide the theatre to help clear a backlog for some ophthalmic services.
The unit, which consists of an anaesthetic room, operating theatre and two-bed recovery, is at the hospital until the end of the year.
Vanguard said it was "co-operating fully" with the hospital for the investigation which would focus on the drugs, equipment, sterilisation and protocols used.
"The majority of operations were successful, however a number experienced an unusual level of discomfort after surgery," added a spokesperson.
"We have, with the hospital, conveyed to the patients our concern and sympathy for the discomfort or distress they have experienced."
The hospital's chief executive, Jo Cubbon, said the issues meant many patients who had already waited longer than they should have, will now have to wait again for their operation.
"We are very sorry this has happened and are working to put a solution in place so that these patients will receive their treatment as soon as possible," Ms Cubbon said.

Judges scored four restaurants selected to represent each town or city, assessing hygiene ratings and public votes.
The West Yorkshire city was praised for holding several curry-themed events, including a poppadom-eating challenge.
Glasgow finished second and Brighton came in third in the competition, which marks the end of National Curry Week.
Leicester and Birmingham finished fourth and fifth respectively.
The restaurants selected to represent Bradford were Aakash, Kiplings, Shimla Spice and Akbar's.
Patricia Tillotson, of Visit Bradford, said: "Winning the hotly-contested competition this many times in a row has never been done before.
"Our entry has created a real sense of community cohesion, which ultimately is what the Curry Capital of Britain competition is all about."
Our love affair with curry
See: BBC Food - Curry recipes
The curry capital title was first awarded in 2001. It was won by Bradford in 2004 in addition to  2011-2014.

In August, Scott initiated the investigation into a "disappointing" Olympic campaign that produced three medals from a target of five to seven.
A key finding of the report required Australia-based Scott to relocate to Britain, something he was unable to do.
Scott, who has been performance director since 2007, will step aside at the end of the month.
The Australian's removal allows British swimming to begin the search for a new performance director as attention turns to the next Olympics in Rio in four years' time.
"I respect this conclusion from the performance review I initiated following our results in London," Scott said.
"I wanted to make sure we left no stone unturned in understanding why we didn't achieve our goals.
"One of the key findings of the review requires a change to my current working practice by being based in Britain. However, for personal and family reasons, I'm unable to meet this recommendation and therefore offered my resignation."

The two nations meet in a 2018 World Cup qualifier on Armistice Day, also known as Remembrance Day, when the United Kingdom remembers those who have lost their lives in war.
But Fifa, who are in charge of world football, say they do not allow any nations to have any political, religious or commercial messages on shirts.
They had turned down a request to allow England and Scotland's players to wear armbands with poppies on.
The FAs have now said that they will let their players wear the armbands anyway and will accept any punishment.
Poppies are worn by millions as a symbol to remember those who have lost their lives in war or been injured.
British Prime Minister, Theresa May, has said Fifa's refusal of players being allowed to wear poppies is "outrageous".
Speaking at Prime Minister's Questions on Wednesday, she said: "Our football players want to recognise and respect those who have given their lives for our safety and security - I think it is absolutely right they should be able to do so."
The Football Association of Wales has also written to Fifa requesting permission to wear poppies on armbands during their game against Serbia in Cardiff on 12 November but has not yet said if it will ignore the ban.
About 30 patients in Somerset who had cataract surgery inside a mobile hospital theatre have been left with blurred vision or other complications.
[NEXT_CONCEPT]
Bradford has been named Curry Capital of Britain for a record-breaking fifth year in a row.
[NEXT_CONCEPT]
British Swimming's performance director Michael Scott has resigned following a review into results at London 2012.
[NEXT_CONCEPT]
The Football Associations of England and Scotland say they will ignore a ban on players wearing poppies in their upcoming match on 11 November.