Flying is generally restricted for conditions where air or gas has been surgically introduced into the eye, such as during retina repair surgery or certain corneal transplants. In these procedures, a gas bubble is often used to hold tissue in place; due to Boyle's Law, this bubble expands as cabin pressure drops at high altitudes, which can cause a catastrophic rise in intraocular pressure, leading to permanent blindness. Patients must wait until the bubble is fully absorbed—typically 2 to 6 weeks depending on the gas used. Additionally, acute infectious conditions like severe bacterial or viral conjunctivitis (pink eye) are often discouraged or prohibited by airlines to prevent spreading the infection in the confined cabin space. Individuals with recently diagnosed retinal tears, acute glaucoma with uncontrolled high pressure, or those who have had very recent intraocular surgery (within 24–48 hours) are usually advised against flying until stabilized, as the physical stress of travel and dry cabin air can exacerbate complications or lead to wound leakage.