If you do che trul [Liberating from Harm] puja and Four Mandala Offerings to Tara, then having the eye operation is very good.

Another option through practice is to do the following:

Turning the prayer wheel, visualize Chenrezig. Light is emanating from Chenrezig, purifying your eye disease and purifying all the harms and the disease completely. After several malas [of the Chenrezig mantra, OM MANI PADME HUM], then visualize that all sentient beings are purified. Focus strongly and think that all the four things—negative karma, sickness, spirit harm and obstacles—are completely purified.