Cheating with Contacts Before Your Consultation
We recommend the holiday from contacts prior to consultation and surgery for your own good. We want to make absolutely sure your corneas are their true shape and not an altered shape from wearing the contact lenses. Saying that, your little dalliance in lenses is probably OK, but don't push the limits on that. I often say that leaving your contacts out prior to LASIK is the hardest part of the procedure!
Wearing Contact Lenses before LASIK
You are ready for your consultation. 72 hrs without the use of soft contacts is enough prior to the exam.
Contact lenses before LASIK
It is not possible to give a complete answer to this question because it depends on many factors. In general, soft lenses have a more limited effect on the stability of the baseline refraction before LASIK than hard or gas permeable lenses. If you are wearing the hard type, it may take longer for your eyes to stabilize. In addition, toric or astigmatism correcting soft lenses also can distort the eye shape for some period of time.
It may be possible to have your consult, but what we look for is several measurements separated in time with minimal change to the refraction or we might not give the best results possible for a particular patient. There are other things we can look at such as topography patterns and other technical information.
The basic concept is that we want the eyes to be at their baseline level without the influence of contacts since there will not be contacts influencing the eye after the LASIK procedure. Sometimes contacts can change the prescription, and hide some of the correction that is necessary and this could result in a higher chance of needing a second surgical procedure.
Contact lens wear prior to LASIK
There's really no hard and fast answer to this. In general, the more you wear contacts prior to your measurements for surgery, the higher the chance the cornea will not be back to its "natural" shape, and the less accurate the surgical result. The less time elapsed between contact lens wear and measurements, and the longer the time of wear, the worse the situation. A "few hours" five days before measurements may not make a huge difference, but it could make a slight difference.
It also depends on what type of lens is being worn--a gas permeable lens will potentially cause more corneal changes than a soft lens.
If it's not terribly inconvenient, the ideal solution would be to follow your doctor's directions and truly stay out of lenses the prescribed period of time before your surgical measurements are taken. If you don't mind having a slightly increased risk of needing a touchup or enhancement, then I wouldn't worry about it. There is no data I'm aware of which quantifies all this.
I will say in my practice, I've seen nearly everything, including patients who refuse to take their lenses out the prescribed period of time, and are willing to accept a potentially less accurate correction. As long as the patient is fully informed, and the corneal shape is within the bounds of normal (no inferior corneal steepening, or keratoconus), I will proceed if they wish.