The cornea is the transparent anterior part of the eye. It can be thought of as the windshield of the eye. The cornea and the intraocular lens both focus the incoming light rays onto the retina to form images. A thin layer of tears called the tearfilm covers the cornea and prevents it from drying. Blinking cleans the cornea and distributes a uniform layer of tearfilm on the surface of the cornea.
A variety of conditions can affect the cornea and result in blurry vision. Dry eye occurs when lacrimal glands do not produce enough tears, or when tears evaporate too quickly. A healthy and uniform tearfilm is a critical factor necessary to achieve clear vision. Minor trauma to the cornea can result in an abrasion or a scratch. Minor abrasions can usually heal without a scar, but major trauma to the cornea can result in permanent scars and blurry vision. A variety of dystrophies and degenerations can also result in corneal scarring and blurry vision. Furthermore, corneal infections can leave permanent scarring on the cornea. Infections also known as ulcers typically result from improper contact lens use or trauma. The corneal surface must be uniform to focus light rays on the retina. Conditions such as keratoconus or ectasia result in warpage of the corneal surface and blurry vision.
PKP -Full Thickness Corneal Transplant
Penetrating keratoplasty or PKP is a full thickness transplant of the cornea. The cloudy, diseased, or scarred cornea is surgically removed and replaced with a full thickness cornea from a donor.
PKP is indicated for visually significant corneal scars, long-standing corneal swelling, corneal dystrophies, and corneal degenerations such as keratoconus and pellucid marginal degeneration where rigid contact lenses no longer provide adequate vision. PKP has a long track record and was first performed in the early 1900’s.
After surgery patients must remain on steroid eye drops for many years to prevent rejection. Non-dissolvable sutures remain in the cornea for several months, and are slowly removed in the office to reduce astigmatism. It may take up to 12 months to reach the best possible visual acuity. PKP may result in regular or irregular astigmatism, and may require prescription glasses or rigid contact lenses after surgery. Corneal transplants which have failed and become cloudy may be repeated and replaced with a new transplant.