The Cornea

The cornea is a dime-sized clear tissue that is the front of the eyeball.  It is the eye’s outermost layer, normally invisible when viewed straight on.  The cornea is a clear, dome-shaped surface that covers the front of the eye, much like a watch crystal or “window” of the eye.  It helps direct light rays towards the lens for focusing and allows light to pass through it to reach the back of the eye.

 

In order for vision to be clear, the cornea must be clean and clear.  Corneal disease can cause the cornea to become opaque or cloudy, preventing light from passing through clearly.  Corneal scars, scratches, surface roughness, and irregular curvature will distort vision, and are frequently associated with sensitivity to light (photophobia).

Corneal Edema

Corneal edema is a swelling of the cornea, the clear dome at the front of the eye. The cornea works with the lens to refract light and help the eye to focus. When the cornea swells, it is often because of a problem with the endothelial layer of the cornea. The endothelial layer makes up the inner layer of the cornea and consists of a network of cells, endothelium. The endothelium pumps fluid in and out of the cornea to keep it dry and maintain its clarity. These cells can be damaged by both trauma and disease. Once these cells are damaged, they cannot repair or replace themselves. The cells are not able to function as well, and the cornea begins to swell with fluid (corneal edema). This causes clouding of the cornea and blurry vision.

At The Cornea and Laser Vision Institute, our doctors can diagnose corneal edema with a detailed but painless eye examination.

Corneal Dystrophy

Corneal dystrophies are rare, inherited disorders associated with dystrophy microscopic chemical deposits in specific layers of the cornea.

Most dystrophies are inherited as autosomal dominant traits. This means that one would expect to find half the family members of a patient to be similarly affected. Because corneal dystrophies present with wide variations in severity, it is not unusual for a patient’s family ocular history to be unremarkable. In many such cases, silent, asymptomatic findings of the dystrophy will be seen in other family members when a thorough ophthalmologic examination is performed.

Dystrophies are often subtle, having minimal or no effect on vision. These dystrophies require no specific treatment. In other cases, irregularity of the corneal surface or repeated surface breakdown may lead to blurred or distorted vision and pain. While drops and ointments may reduce these symptoms, the surface changes sometimes need to be scraped or peeled away. Some of the more severe dystrophies cause clouding of the cornea with considerable loss of vision and require corneal transplantation to restore vision to a normal level.

The following is a partial list of corneal dystrophies that we see as corneal specialists:

  • Anterior basement membrane dystrophy (Map-Dot-Fingerprint dystrophy)

  • Reis-Bucklers’ dystrophy

  • Granular dystrophy

  • Lattice dystrophy

  • Macular dystrophy

  • Snyder’s crystalline dystrophy

  • Fleck dystrophy

  • Posterior polymorphous dystrophy

  • Fuchs’ or Endothelial dystrophy

Corneal Ulcer

Corneal ulcers are infections of the cornea.  They are most often associated with soft contact lens use or trauma to the cornea.  A break in the surface layer of the cornea can occur, through which a microorganism can gain access to the rest of the cornea.  Prompt identification of the pathogen (usually bacteria) and aggressive treatment is needed to limit damage to the eye.

Symptoms:

  • Watery eyes

  • Acute pain

  • Sensitivity to light

  • Blurry vision

  • A feeling as something is in your eye

  • Discharge from the eye

Corneal ulcers generally heal well if treated early and aggressively.  In some cases however, infection of the cornea can lead to perforation (a hole in the cornea), infection inside the eye (endophthalmitis) and, rarely, loss of the eye.  Early testing possibly may be required to determine the cause of the infection.  This could include a diagnostic scraping culture or biopsy.  Our corneal specialists work with microbiologists and pathologists at nearby laboratories to obtain results of these tests quickly. Corneal ulcers are a serious vision-threatening condition and require prompt medical attention.

 

Corneal Abrasion

The cornea is the clear, outer window of the eye.  A corneal abrasion is simply a scratch in the epithelium (skin), or the thin, outer layer of the cornea.  Abrasions usually heal in a short time period, sometimes within hours. Deeper or larger scratches may take up to a week.  The cornea has a tremendous number of nerve endings, which makes any damage to the cornea very painful.

A corneal abrasion is simply a scratch in the outer layer of the cornea.

Symptoms:

  • History of a recent eye trauma

  • Watery eyes

  • Acute pain

  • Sensitivity to light

  • Blurry vision

  • The feeling that there’s something in your eye

  • Twitching eyelid

Causes:

  • Foreign body in the eye

  • Contact lenses

  • Chemicals

  • Blow to the eye

  • Scratched eye (fingernails, hairbrushes, tree branches, curling iron, etc)

Treatment:

Our corneal specialist may apply a topical anesthesia to help relieve the pain.  He also may prescribe an antibiotic to prevent infection.  If the abrasion is small, the epithelium should heal overnight.  If the abrasion is large, it may take a few days and your doctor may recommend a bandage contact lens or tight patch to wear overnight.  It is important that you do not rub your eye, especially during the healing process.

Fuchs Dystrophy

A corneal dystrophy is a bilateral (both eyes) abnormality occasionally present at birth but more frequently appearing later in life. Any of the five layers of the cornea can be involved. Of the many known dystrophies, the one most commonly encountered in clinical practice is Fuchs’ Corneal Dystrophy.

Fuchs’ dystrophy is an inherited eye disease that causes the cells in the endothelium, the last layer of the cornea, to deteriorate. This leads to distorted vision and corneal swelling (corneal edema). The exact cause of Fuchs’ dystrophy is unknown, but is believed to be a combination of hereditary, hormonal and inflammatory factors. This condition affects both eyes and is more common in women than men.

 

The cornea is made up of five different layers, each of which has a specific function that controls vision. The endothelium is the back layer of the cornea, which removes excess fluid from the cornea. Excess fluid can cause the cornea to swell and vision to become distorted. Occasionally the swelling can become so severe that bullae (blister-like lesions) will develop that can result in pain. Once endothelial cells are lost, they do not grow back, so this condition will continue to progress with time.

Symptoms

Although this condition is inherited, symptoms do not usually appear until the patient is over the age of 50. Patients with Fuchs’ dystrophy may experience blurred vision as the first sign of this condition. Blurred vision occurs in the morning as a result of fluid accumulating in the cornea while you sleep. As this fluid evaporates throughout the day, vision may improve. Progressive swelling and thickening of the cornea may also lead to painful erosions and difficulty recovering from cataract surgery. Other symptoms of Fuchs’ dystrophy may include:

  • Sensitivity to bright lights

  • Halos around lights

  • Poor night vision

  • Sharp pains in the eyes

  • Sandy, gritty sensation in the eyes

  • Fluctuating vision

Treatment

While there is no cure for Fuchs’ dystrophy, there are several treatment options available to help relieve the symptoms of this condition and to prevent permanent damage. In its early stages, Fuchs’ dystrophy can often be treated with a salt solution to remove fluid from the eye and reduce swelling. In more advanced stages, Fuchs’ dystrophy may begin to interfere with daily activities and prevent patients from functioning normally. In this stage, patients may require a corneal transplant to replace the cornea with full, thick layers that allows them to see clearly. The DSAEK procedure is an innovative, new, partial corneal transplant procedure performed on an out-patient basis.

Corneal Transplant

An unhealthy cornea prevents light from entering the eye, which can cause blurred vision, or in advanced cases, blindness. This occurs when the cornea is swollen, or scarred, or irregular as in the disorder known as Keratoconus.

Cornea transplantation can successfully replace these unhealthy corneas with a healthy new one and restore vision. The corneal transplant is a wonderful procedure and has restored eyesight to millions. The most common reasons for undergoing a corneal transplant are to improve vision, reduce pain, or to maintain the structural integrity of the eye. Cornea transplants have been performed for several decades and approximately 40,000 are done in the USA yearly. New understandings and therapies of eye surface disease in tandem with advances in cornea transplantation have allowed for greater cornea transplant success than ever before.

With a conventional corneal transplant, the full thickness of the central 7-8 millimeters of the cornea is completely removed. A whole new donor cornea that has been prepared by an eye bank is carefully sutured in place with very fine stitches. These stitches can remain in the eye for over a year. You will not have any pain during the procedure or see the surgery while it is happening. On the day of surgery you will go home with a patch and shield over your eye. You will need to be seen one day after surgery, then one week after that, and then every 3-6 weeks, depending on how the eye is healing.

 

Unlike cataract surgery, where visual recovery is rapid, the healing time after a full thickness corneal transplant can take between 6 months to over one year before the best vision is obtained. The stitches used often cause the cornea to take on an irregular shape during the healing process that must be corrected with glasses or contact lenses.

Careful postoperative management is critical to ensure the success of the transplant. It will require you to take frequent visits to the doctor to measure the cornea, prescribe glasses or contacts, and remove the stitches over time. You must also use eye drops to prevent infection or rejection of the transplant, most likely for many years. Graft rejection occurs in approximately 10% of patients. This needs to be treated aggressively with steroids and usually heals. Occasionally, there are problems with sutures which can come loose, cause infections, or cause astigmatism. The astigmatism after traditional corneal transplant surgery can be significant enough that eyeglasses alone won’t give adequate vision. These patients may ultimately require contact lenses or additional surgery to reduce or eliminate the astigmatism. Eyes with a transplant are also more at risk from minor trauma. It is important to wear safety glasses at work or during sports.

DSAEK

An innovative procedure known as DSAEK is getting high marks from our doctors at the Cornea and Laser Vision Institute. Until recently, cornea transplant patients in the St. Louis area had very few treatment choices if they ever wanted to see clearly again. The most likely option was to undergo full thickness corneal transplant – a complicated procedure that surgically replaces the entire damaged cornea with a donor cornea.

 

Short for Descemet’s Stripping Automated Endothelial Keratoplasty, DSAEK (pronounced de-sak), is not nearly as invasive, and requires considerably less recovery time. Rather than removing your entire cornea, our cornea specialists make a small incision in the side of the eye and replace only the damaged portion at the back inner dome of the cornea with donor cells. DSAEK uses the innovative instrumentation designed for LASIK. The donor cornea is prepared using the LASIK instrumentation to create only a thin layer of tissue to transplant. This thin layer contains a new healthy layer of pump cells. The surgeon then delicately pushes the new cells in place with a bubble of air. It’s like replacing the wallpaper instead of replacing the wall. During the first twenty-four hours, it is important to stay on your back as much as possible to keep the air bubble positioned correctly, anchoring the new tissue in place. The transplanted cells begin pumping fluid out of the cornea, thus creating a suction that causes them to adhere to the back of the host cornea.

We’re excited about DSAEK at our practice. Rather than facing a potential one-year recovery period (a huge drawback for full thickness corneal transplant patients), the healing time is mere months for DSAEK patients. Another benefit: the procedure involves little or no stitches. The incision required for the surgery is very small. DSAEK is performed as an outpatient procedure under local anesthesia. The patient can go home after surgery without even having to have an eye patch. Finally, there is also less risk of rejection because the majority of the cornea remains in place.

The main disadvantage of the DSAEK procedure is that the new layer of cells is manipulated more directly than in a full thickness corneal transplantation, potentially producing more damage and possibly resulting in graft failure. There is a 10% chance that the new tissue will not adhere properly requiring repositioning and a new bubble, or in less than 1% of cases, re-operation. The cornea is also left somewhat thicker than the original due to the addition of tissue to your current cornea. This may make it more difficult to follow glaucoma. Antibiotic eye drops will be used for a week or so to help prevent infection, and a mild steroid eye drop will need to be used for long term to help prevent rejection.

 

1 day after surgery with air bubble holding new cornea in place

The results of corneal transplantation are excellent, but as you can see, it takes a long time to heal. That is why it is such a wonderful thing to be able to replace full thickness corneal transplantation with the new partial thickness DSAEK procedure. This is now an option for many who would otherwise have been limited to a full thickness transplant. Although DSAEK is one of the most sophisticated and precise microsurgical procedures performed by an eye surgeon, as far as the patient is concerned, a big procedure has now been replaced by a much simpler, outpatient procedure that allows you to return to normal activities and restores your vision sooner.

What is Keratoconus?

According to the AAO website, keratoconus is an uncommon condition in which the normally round, dome-like cornea (the clear front window of the eye) becomes thin and develops a cone-like bulge. Keratoconus literally means “cone-shaped cornea.” Keratoconus is a non-inflammatory eye condition in which the normally round dome-shaped cornea progressively thins causing a cone-like bulge to develop. This results in significant visual impairment.

Because the cornea is irregular and cone shaped, eyeglasses do not appropriately correct the vision in patients with keratoconus. This is a result of the glasses not conforming to the shape of the eye. It should be no surprise that patients with keratoconus see best with rigid contact lenses since these lenses provide a clear surface in front of the cornea allowing the light rays to be projected clearly to the retina. Therefore; the vast majority of patients are treated with rigid contact lenses. There are however some excellent new surgical options for patients with keratoconus who cannot tolerate these lenses. Many patients are initially unaware they have keratoconus and see their eye doctor because of increasing spectacle blur or progressive changes in their prescription.

The Causes of Keratoconus

The actual incidence of keratoconus is not known. It is not a common eye disease, but it is by no means rare. It has been estimated to occur in 1 out of every 2,000 persons in the general population. Keratoconus is generally first diagnosed in young people at puberty or in their late teen years.

CORNEAL COLLAGEN CROSSLINKING

The Doctors at Ophthalmology Associates are excited to be investigators for this revolutionary new treatment for Keratoconus and corneal ectasia.  For more detailed information about this treatment please visit www.cxlusa.com or call the office at 314 966-5000.

 

BREAKING NEWS: Five-year data shows CXL can stop keratoconus progression

This prospective study evaluated long-term results of corneal collagen cross-linking (CXL) with ultraviolet A irradiation and riboflavin in 32 patients (40 eyes) with grades I through III progressive keratoconus. At five years, CXL halted disease progression, stabilized UCVA, refraction, corneal thickness, corneal power, and posterior elevation. Improvements also were noted in BCVA and anterior elevation. One patient dropped out due to an increase in BCVA and an inability to tolerate contact lenses or spectacles. No safety issues were noted. Ophthalmology, August 2013

NEW STANDARD: CXL should be considered in all patients with progressive keratoconus or corneal ectasia

Investigators analyzed a cohort of 104 eyes to determine preoperative characteristics that may influence outcomes from corneal collagen crosslinking (CXL) treatment. No factor was independently predictive of CXL failure. In general, eyes with worse CDVA and higher maximum K readings were more likely to improve. They conclude that all eyes be considered for treatment with the goal of stabilizing disease progression. Patients and physicians should be aware of the risk for loss of visual acuity.
Journal of Cataract & Refractive Surgery, August 2013

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