But the risks were great.
It's always dicey to operate on wild animals. The physical and emotional stress can be enormous.
New smells could unsettle them. A needle could unnerve them. Worse yet, their mother could reject her cubs and even attack them.
The challenge for the caregivers came down to this: Could they do this technical procedure without breaking the animals' instinctive bonds to each other?
In August, University of Pennsylvania veterinary ophthalmologist András M. Komáromy crawled into the cage with the cubs for one of the more unusual eye exams he had ever done.
The team's assessment: They needed to operate. "Everyone was in agreement," Hinshaw said.
Native to central Asian mountains, snow leopards are on the World Conservation Union's "red list" of endangered species. Experts estimate that from 3,500 to 7,000 remain in the wild, threatened by poaching, habitat loss, and conflict with herders.
There are 142 snow leopards in 55 North American zoos, said Jay Tetzloff, who coordinates the continent's snow leopard breeding program and is superintendent of Miller Park Zoo in Bloomington, Ill.
Weeks of preparations culminated Tuesday in twin procedures on Kimti and Dian. The zoo's estimated cost: $2,500.
To avoid problems, the zoo staff wanted to reunite the cubs with their mother, Maya, as soon as possible.
The staff had picked the date because, at four months old, the cubs were weaned. If Maya rejected them or they had to be apart for more than a day, they'd be easier to feed.
The surgical team also needed to prepare for a recovery that had minimal aftercare. The doctors wanted to avoid eye medications, which might be tough to administer, and knew that they wouldn't be able to place a standard cone-like collar around the animals' heads to prevent them from licking their wounds.
The zoo has been relying increasingly on behavioral conditioning - training animals to "accept" procedures.
Weeks ahead of time, keepers Jen Robertson and Kay Buffamonte began going into the enclosure with the cubs - unusual in itself - with toys.
Day by day, as the cubs were distracted by the toys, the keepers touched them lightly, then more firmly, then with a false syringe, and finally with a real one.
Once accustomed to the needle, the cubs got their first vaccinations.
Since strange scents could disorient the cubs or alarm their mother, the zoo staff asked the Penn surgeons what substances they would use - and then began leaving towels soaked with a weak iodine solution in the cage.
On Tuesday morning, with the mother moved to a different area, the keepers injected the cubs with a rapid anesthetic.
In about two minutes, the cubs were drowsy. Two minutes more, they were asleep.
Robertson and Buffamonte carried each cub - at 22 pounds about double the weight of a large house cat, and more than twice as strong - to a van, where they were tethered to machines that would monitor their hearts and the oxygen in their blood.
In the zoo clinic's operating room, the medical team put intravenous catheters in the cubs' hind legs, tubes in their windpipes, and blood pressure cuffs on their tails.
Then they started on the defective upper eyelids.
Working side by side, Komáromy and fellow Penn veterinary opthalmologists William Crumley and Shelby Reinstein removed the skin from the defective portions, leaving triangular wounds.
They sewed the edges together with a double layer of the tiniest stitches they could manage. The sutures will eventually be absorbed.
The team also trimmed the cubs' claws. "Hopefully, this gives them one less thing to catch on the suture or incision," Hinshaw said.
The zoo staff took eyelid tissue and blood samples, which will be sent to Peggy Barr, professor of veterinary virology and immunology at Western University of the Health Sciences in California.
Conceivably, genetic information could help determine which animals, for example, might be more susceptible to eyelid problems and which might be more vulnerable to infections after being stressed.
In such small populations of unknown genetic origin, it may also help prevent inbreeding.
Two hours after being taken from their quarters, the snow leopard cubs were back.
They were given drugs to wake them up quickly. Soon, they started making a characteristic cry that meant they wanted their mother.
The staff opened a gate between Maya and her cubs, but left a mesh panel in place so that they could see and smell each other but she couldn't do harm. Maya came close and answered her cubs.
"They were all doing the right things," Hinshaw said. So the keepers opened the panel. Maya started licking her cubs' fur.
Now, the staff has to watch and wait.
"The surgery went perfectly," Komáromy said. "But we know this is not the end yet."
The cubs are too active for close inspection, so the keepers will take numerous photos, hoping to get images that show their eyes.
On Wednesday, they were squinting a bit - as expected - but were eating well and seemed happy.
Depending on how things go, Kimti and Dian could make their public debut next month.
Contact staff writer Sandy Bauers at 215-854-5147, email@example.com, or @sbauers on Twitter. Visit her blog at philly.com/greenspace