Should you have LASIK or LASEK on both eyes on the same day?

The norm in the USA and in much of Europe is to do LASIK on both eyes at the same sitting. i.e. treating both eyes whilst the patient is still on the operating table. There is obviously a lot of financial sense in this for the various clinics as it increases their throughput of eyes treated and hence their profits. However, what is best for the individual patient? The arguments are in 2 groups:

1. Safety:

    It goes without saying that if, in a planned bilateral operation, there is any intraoperative complication in the first eye then the second should be abandoned. In practice this usually means any flap problems. I would also include any marked epithelial loss or "slide" due to the passage of the microkeratome. This is because the incidence of the "sands of the Sahara" syndrome is 10 times higher in these cases and will not present until day 1 after the surgery if it occurs. Such epithelial problems are commoner in older patients.

    Any infection, inflammation, flap wrinkles etc. almost always show up on day 1 post op and by waiting 2-7 days between eyes one should avoid a simultaneous bilateral problem. However, these are unusual and most people opt for same day bilateral surgery. I had no bilateral LASIK complications last year.

The only real complication of surface laser, whether PRK or LASEK, is a delayed one of "haze", which is usually maximal about 6 to 8 weeks post-op. Haze is commoner in higher prescriptions or in people with delayed epithelial healing.  We used to do no bilateral PRK's for this reason, but now, as haze is much more uncommon, most people think that up to about -5 Dioptres on the same day is reasonable. I have personally not had a haze problem for the last 2 years, so feel more comfortable going even somewhat higher than -5 in some patients.

    LASIK/PRK is dependant on the technology of the excimer laser machine. These are gas lasers and are calibrated at the beginning of each day and several times during it. They are complicated machines but are generally reliable and have a lot of safety features. However, if there is a technical problem and both eyes are treated, it could affect both eyes adversely without the surgeon being aware of it at the time of surgery. The most likely fault could be a simple over or under treatment which could be corrected fairly easily in most cases. A worse case would be a beam irregularity. There are checks on all the common machines to pick this up but there has been a reported case in Canada of a mirror problem in a machine leading to irregular astigmatism in a group of bilateral patients. These patients were sorted out with a lot of angst and it was realised that the fault in the machine should have been picked up before the surgery. However, it is a salutary lesson!

2. Accuracy:

Both eyes tend to behave the same way when lasered. Hence, in theory, it is more accurate to do one eye at a time, so that, if the first eye behaves in an unusual way, then you can modify the laser settings on the second. However, in practice, this is generally such a small advantage that most people tend to have both eyes on the same day.  Also, I have seen a number of cases where I have treated both eyes on the same day and they have different results. This must only mean that each eye has a sort of unique microenvironment that responds to the laser energy and heals in its own particular way.