I have been diagnosed as good for PRK, as I have thin cornea and dry eye. I know there are risks with the dry eye. What's your opinion on going ahead? I have 2 prescriptions. Many thanks.
PRK for Thin Cornea and Dry Eye?
Doctor Answers (9)
Thin corneas and PRK
It is typically better to perform PRK rather than LASIK on a patient with a thin cornea. Of course, I don't have your corneal thickness measurements in front of me. Assuming there are no other abnormalities, PRK is a better option as it does not thin the cornea as much as LASIK. You must remember that the long term results of PRK and LASIK are almost identical.
It is the short term that is different, with the recovery phase of PRK being somewhat longer than LASIK. When I look at a patient with thin corneas, I decide if there is enough corneal tissue to safely proceed with PRK. If there is not, then we can proceed with what is called a Phakic Intraocular Lens, which is another good choice, though PRK is likely less invasive.
PRK for Thin Corneas
- PRK has been shown to cause less dry eye postoperatively. This is thought to be because there is no temporary disruption of corneal nerves as with the LASIK flap (nerves regenerate over 6 month period, but during this time LASIK patients may experience more dry eye)
- PRK is very safe, effective and stable over time.
- The drawback of slightly prolonged visual recovery is well worth the benefits of gaining excellent vision a few weeks after the procedure.
PRK Eye Surgery
PRK uses less cornea than LASIK and causes less dry eye. The outcomes are the same or better. If you are a candidate for PRK and can tolerate the initial discomfort and blurred vision, it is at least as good as having LASIK.
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PRK and dry eyes
While PRK is preferable over conventional Lasik for those with thinner corneas, newer all laser Lasik surgeries like RelEx SMILE have made laser vision possible for many of those who were advised against conventional Lasik. You could discuss with your ophthalmologist if they offer surgeries like SMILE and if your cornea is suitable for it.
PRK is safer for those with thinner corneas
The concern with those with thin corneas is getting too close to the bottom of the cornea which can potentially lead to ectasia which may in some situations require a corneal transplant. There are limits to LASIK and PRK both and it is best to use alternatives such as phakic IOL's instead of taking risks with long term complications.
PRK may be safer for dry eye and thin corneas
PRK may be safer for dry eye and thin corneas, but bladeless all laser LASIK may be your wisest choice for accuracy and the most precise vision correction.
PRK and dry eyes
Both LASIK and PRK can cause dryness after surgery. However, many believe including myself that PRK may have less of a drying effect. This is due to the fact that without a flap in PRK, the ablation is not as deep into the stromal bed of the cornea and may affect less of the corneal nerves.
In patients associated solely with contacts, I think LASIK is OK. In patients with dryness requiring frequent lubrication or medicated eye drops I will often recommend PRK. Patients with severe dryness are likely not good candidates for anything.
In your case having a thinner cornea and some dryness, I would definitely go with PRK over LASIK.
PRK and dry eyes
Both Lasik and PRK can exacerbate the dry eye symptoms for several months after surgery. If the preop exam indicates severe dry eye with corneal changes you may be better off with a refractive lens implant. Certainly starting Restasis preop is indicated.
PRK may be your best option
When patients have thinner corneas that are a normal shape, and a relatively high prescription then PRK may be the best option for vision correction by laser.
PRK is photorefractive keratectomy and this is essentially the same type of procedure as LASIK but unlike LASIK it is not done under a protective corneal flap. Instead, the outer skin of the eye is removed either mechanically or with alcohol, and then the laser reshapes the eye cutting through a thin Bowman's membrane and into the corneal stroma. Bowman's does not heal but a new skin or epithelium grows over the front of the eye and gradually over several days to weeks the vision is recovered. This procedure is less invasive than LASIK, meaning it goes less deep into the surface of the eye, since a flap would have some additional thickness and thus make the treatment deeper. In cases of thinner corneas, it may be prudent to leave more tissue beneath the treatment and PRK can make sense for these cases.
There are some other considerations however. First is that with all laser femtosecond LASIK the flap can be made very thin where the invaseiveness is only minimally increased. Second, with PRK there can be scarring, so an "off label" treatment is often done of using a drug called mitomycin to stop potential scarring but this can have an unknown effect on healing and the cornea in general. Although this is thought to be safe, it is a consideration when deciding on which procedure to have.
As to dry eye, this is an open question. Some believe that PRK causes less dry eye due to the reduced cutting of corneal nerves, whereas others believe that the increased healing of the epithelium required in PRK can lead to greater dry eye problems post operatively. There is no clearcut answer as to an advantage from this perspective.
Therefore the real question becomes, how thin are the corneas, how high is the correction, how large must the treatment zone be, and how strong is the cornea to begin with. In other words, there is much to consider before one can accurately and completely answer this complex question.