Hi Jayden
There is some variation in practice here, but I do not recommend assessment and LASIK surgery on the same day too.
In terms of risks and benefits, the major downside (to doing everything on the same day) is that pre-LASIK assessment requires dilation of the pupils of your eye. This is obligatory to:
- Relax the focusing muscle of your eye and ensure the most accurate spectacle power measurement possible
- Allow a full eye check including the retina and lens of the eye, which are not fully visible otherwise
However, pupil dilation affects the size and position of the pupil, which is used by most lasers to determine the location on your cornea to treat. Lasering an eye with a dilated pupil could result in a decentered treatment, which can cause an irregular cornea with blurred vision.
It is therefore essential to only perform LASIK on an undilated eye. If the pupil has been dilated on that day, it is necessary to wait until the pupil size has returned to normal before performing LASIK. The time taken for this to happen is different for different people, but could be 5-6 hours or more.
For assessment and LASIK surgery to be done on the same day, you would need to do the assessment early in the day, and then go back or hang around for some hours waiting for the pupil to return to normal size, before having LASIK surgery. Sometimes the pupil has not yet returned to normal size at the scheduled time for surgery. So in such centers, eyedrops are instilled to cause faster constriction of the pupil, but a pharmacologically constricted pupil may also not be in the same position as a natural pupil.
Doing LASIK on a different day than the assessment ensures that the pupil has returned to a normal size at the time of treatment, thus ensuring the best possible treatment centration.
The possible benefit of doing everything on the same day is that the logistics could be simpler, with one fewer visit to the clinic. But remember that even with same day LASIK, there is a need to wait some hours for the pupil to return to normal size. You could be hanging around for the better part of a day not being able to do too much while staying close to the clinic. Either that or getting home and then coming back again, which is really not that different from doing it on 2 separate days.
Another reason why I prefer to do it on separate days is to allow patients time to think over their decision and most importantly, not feel rushed into doing something that is still an operation after all, with its attendant risks and benefits, pros and cons.
But for someone who has already made up their mind, and taken the (whole) day off to have everything done on that one day, and who has a pupil that recovers from dilation pretty fast, I suppose having everything done on that one day can work too.
