UNDERSTANDING THE ANATOMY OF YOUR EYES

We hope that this information about your eye will help you to evaluate your options understand what happens during your surgery.

The cornea is the clear tissue in front of the pupil and iris. It is living tissue but has no blood vessels.

You see through the cornea, just as you would look through a window. Behind the pupil is the lens, which along with the cornea, focuses the light entering the eye. The retina in the back of the eye is composed of specialized nerve cells that transmit the light impulses coming through the front of the eye to the optic nerve and then to the brain. In a healthy, normal eye, light passes through the cornea and lens, and is focused on the retina. Sharp vision requires all structures of the eye to be in good working order. Like a foggy window, loss of transparency of the cornea will contribute to reducing vision.

The cells that line the inside of the cornea are endothelial cells. These cells pump water out of the cornea. Without these cells the cornea would swell to five times its normal thickness, causing clouding of the cornea. Clouding of the cornea can be related to many factors, such as injury, infection, congenital disorders, and aging.  To remedy this resultant swelling and cloudiness, a corneal transplant may be indicated to restore vision.  

CORNEAL TRANSPLANTS

The corneal transplant procedure involves the surgeon removing a window of cloudy tissue (or just the depleted endothelial cells) from the cornea and replacing it with healthy corneal tissue donated from a local eye bank. There are various methods by which a surgeon can perform corneal transplantation, each with its own indications and advantages.

PENETRATING KERATOPLASTY (PKP, full-thickness corneal transplant)

More than 40,000 full- thickness corneal transplants are performed in the United States each year. In this procedure, a round, button-shaped section of tissue is removed from the patient’s diseased or injured cornea and replaced with donor tissue. This new tissue is then held in place with many tiny sutures (between 16-24), which you will not see or feel. To heal properly, the sutures must be in place a minimum of six months but are often left in place for years.  Full visual recovery can take up to 12- 18 months.

Advantages: Full thickness corneal transplants have been performed since the early 1900’s, good long term follow up data is available, and they allow for full access to other structures in the eye, facilitating reconstruction of the iris and exchange of lens implants if warranted.

Disadvantages: post -operative astigmatism

Indications: corneal scar, keratoconus, pellucid marginal degeneration, corneal ulcer, corneal edema or swelling from disease such as Fuch’s dystrophy or following cataract or other eye surgery.

DESCEMENTS STRIPPING AUTOMATED ENDOTHEIAL KERATOPLASTY (DSAEK)

The DSAEK procedure is a partial-thickness corneal transplant that only replaces the diseased endothelial layer of tissue along with a thin layer of supporting corneal tissue, A thin piece of healthy donor tissue is carefully folded and inserted into the eye through a small (5 mm) incision in the sclera (white part of the eye) and attached to the back, inner "dome" of the cornea.  The donor tissue is then held in place with an air bubble until it adheres to its new place in the patient’s eye, usually in about 24 hours. The small incision is secured with three to four small sutures. In some cases, the air bubble needs to be replenished in a secondary procedure. In most cases, the vision will begin to improve in about one- two weeks.  Full recovery is typically 3 months.

 

Advantages:  Less astigmatism, shorter recovery, smoother surface, less susceptible to serious injury from trauma.  

Disadvantages: risk of graft dislocation in the first 24-48 hours after surgery requiring repositioning

Indications: Fuch's endothelial dystrophy, corneal swelling after cataract or other eye surgery

INTRALASE ENABLES KERATOPLASTY (IEK)

This is an advanced form of penetrating (full thickness) or lamellar (partial thickness) keratoplasty.   Conventional keratoplasty is performed using specialized blades called trephines to cut the donor and host cornea. These blades are limited in that they can produce only a single type of cut.  Intralase enabled keratoplasty (IEK) utilizes a femtosecond laser to vary the size and shape of the cuts of the corneal tissue. The laser can be used to precisely and accurately cut a more complex shape of both the donor tissue and the host tissue. Surgeons can choose the appropriate configuration for the corneal graft depending on the type of disease or opacity present. This produces a stronger union between the old and new cornea, allowing for fewer stitches that can be removed earlier, with less astigmatism and faster restoration of vision in most cases.

In this procedure, the surgeon first prepares the patient’s and the donor cornea with the laser in the laser suite. The next day, the procedure is completed in the operating room where the donor tissue is sutured into place under sterile conditions.

Advantages: results in secure grafts that require fewer sutures, reduced induced astigmatism, allows for better wound sealing and stronger wound healing, earlier suture removal,  and more rapid restoration of functional vision.

Disadvantages: Two stage procedure: first the laser treatment to prepare the corneas and then the transplant is performed in the operating room; additional cost for laser treatment

Indications: Keratoconus, corneal scar, keratoconus, pellucid marginal degeneration, corneal ulcer, corneal edema or swelling from disease such as Fuch’s dystrophy or following cataract or other eye surgery.