Pachymetry Assisted Laser Keratoplasty
New Keratoconus treatment with pachymetry assisted laser keratoplasty
Some corneal disease such as keratoconus and corneal dystrophy can cause scar and opacity in the anterior part of the cornea while leaving the posterior part and Descement’s membrane of the cornea clear and in this case it would be greta just to treat the anterior part while leaving the unaffected posterior part in a procedure called Lamellar Keratoplasty. In this procedure the affected anterior part of the cornea is replaced with a donor corneal graft.
There are many advantages of lamellar keratoplasty over the traditional penetrating keratoplasty such as:
1- Faster visual rehabilitation.
2- Reduce the incidence of post operation astigmatism.
3- Reduce the risk of corneal graft rejection especially endothelial rejection.
4- In Lamellar Keratoplasty there is no invasion of the anterior chamber as penetrating Keratoplasty and this help to reduce the incidence of intraoperative complications that results from penetrating the eye such as endophthalmitis, cataract and glaucoma.
The disadvantage of this procedure is that the interface between the donor tissue and host corneal bed can develop opacities and haziness which can cause irregular astigmatism and decrease the final visual acuity.
Lamellar Keratoplasty can be done with excimer laser ablation which provide high degree of accuracy. Laser ablation is guided by pachymetry and this new procedure is called Pachymetry assisted laser keratoplasty (PALK).
In this procedure, the desirable diameter and thickness of the scared anterior part of the cornea (should be less than 300 microns in depth) that we want to remove can be obtained by using excimer laser that is guided by automatic pachymetry.
Pachymetry provides a map of the thickness of the whole cornea and helps the surgeon to measure the exact depth of scared tissue, obtain uniform and even thickness of ablation and avoid microperforation into the anterior chamber that mainly happen accidently in manual lamellar Keratoplasty.
The created flap is removed and the donor corneal tissue is placed on the host corneal bed and sutures are applied. Patients who underwent this procedure had faster visual recovery and had less post operative astigmatism.
In a study, this procedure can be used as new keratoconus treatment to treat moderate to severe keratoconus instead of using the traditional penetrating Keratoplasty. They found that the visual recovery was faster for patients who underwent this procedure and the best corrected vision after the procedure was better.