Recurrent corneal erosion is a condition affecting the outermost layer of corneal cells called the epithelium. The problem is caused when the bottom layer of epithelial cells adhere poorly to the cornea, causing them to slough off easily.
Cornea: Basic anatomy
The cornea is the transparent, dome-shaped window that covers the front of the eye. Although most people don’t know a lot about this part of the eye, it is a powerful refracting surface that provides two thirds of the eye's focusing power. Like the crystal on a watch, the cornea gives us a clear window to look through. The cornea has nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. It is made from several different layers:
-
Corneal epithelium. This is one thin epithelial layer of fast-growing and easily-regenerated cells, kept moist all the time with tears.
- Bowman's layer. This layer is one tough layer that protects the corneal stroma, consisting of irregularly-arranged collagen fibers.
- Corneal stroma. We are talking about one transparent middle layer responsible for most of the focusing that the cornea performs. It is made from regularly-arranged collagen fibers along with fibroblasts. The corneal stroma consists of approximately 200 layers of type I collagen fibrils.
- Posterior limiting membrane. This is a thin acellular layer. The role of this membrane is to be a modified basement membrane of the corneal endothelium
- Corneal endothelium. This is a simple squamous epithelium, which works as a barrier to prevent water inside the eyeball from moving into and hydrating the cornea, which would lead to blurred vision. The corneal endothelium is bathed by aqueous humour, not by blood or lymph, and has a very different origin, function, and appearance from vascular endothelia. The middle of our eye is filled with a jelly-like substance called the vitreous. The vitreous is clear and allows light to pass directly from the front to the back of our eye.
The iris, the colored circle at the front of our eye, changes the size of the pupil which allows different amounts of light into our eye. The pupil is the dark hole in the middle of the colored part of our eye. The pupil gets smaller in bright conditions to let less light in and bigger in dark conditions to let more light in.
Cornea size
In humans, the cornea has a diameter of about 12 mm and a thickness of 0.5 mm - 0.7 mm in the center and 1.0 mm - 1.2 mm at the periphery. Transparency, avascularity, and immunologic privilege makes the cornea a very special tissue. In humans, the refractive power of the cornea is approximately 45 diopters, which amounts to roughly three-fourths of the eye's total power.
Recurrent Corneal Erosion: Incidence of the condition
Recurrent corneal erosions are quite frequently reported in most developing countries, where a lack of proper nutrition plays a significant role in threatening the health of the cornea. If corneal erosions are inherited, the pattern is dominant; however, most corneal erosions are acquired. Recurrent corneal erosions usually are seen as a bilateral (meaning it strikes both eyes) problem occurring somewhat more frequently in females than in males.
This condition occurs in adults, usually after the fourth decade of life. However, there are studies that have associated recurrent corneal erosions with juvenile Alport syndrome and renal complications.
Recurrent Corneal Erosion: Etiology of the condition
Recurrent corneal erosion syndrome is characterized by a disturbance at the level of the corneal epithelial basement membrane, which results in defective adhesions and recurrent breakdowns of the epithelium. Recurrent Corneal Erosion can occur secondary to corneal injury or spontaneously, although some predisposing factors, such as diabetes or a corneal dystrophy may be the underlying cause.
The most common cause of RCE syndrome is definitely trauma to the cornea. In these cases, patients will generally give a history of previous oblique corneal abrasion with an object such as a fingernail, piece of paper… Corneal abrasions may result from:
- foreign bodies
- contact lenses
- chemicals
- fingernails
- hair brushes
- tree branches
- dust
The original injury is generally well recalled by the patient as it is usually followed by several days of pain, watering and photophobia (sensitivity to light). The first recurrence may then not occur for quite a few months after the original trauma. This syndrome can also occur spontaneously, although in this situation there is often some predisposing factor. For example, many corneal dystrophies are associated with recurrent corneal erosions. Other possible causes of Recurrent Corneal Erosion are:
- Post infectious ulcers from herpes simplex
- Exposure
- Cockayne syndrome
- Reis-Bücklers dystrophy
- Vitrectomy
- The improper use of contact lenses
Symptoms of recurrent corneal erosion
Recurrent corneal erosions are usually bilateral, meaning they occur on both sides, and are characterized by various patterns of dots, parallel lines that mimic fingerprints, and patterns that resemble maps, which appear in the epithelium. All this is accompanied by:
- Severe pain (especially after awakening)
- Blurred vision
- Foreign body sensation
- Dryness and irritation
- Tearing
- Red eye
- Light sensitivity
- Visual acuity loss
- Astigmatism
- Epithelial blebs
Diagnosis of recurred corneal erosions
Second option is a careful slit lamp examination which often reveals corneal erosions. Many times, there may be associated generalized or localized patches of corneal edema.
Corneal topographic analysis often reveals focal areas of corneal flattening in eyes of people with this syndrome. This finding is important, as the identification of areas of focal abnormality in RCE syndrome remains a significant clinical problem in those patients with symptoms but no evident epithelial abnormalities.
Prevention
There are some advices for all the people that are in high risk fore developing this syndrome! Some of the most effective are:
- avoiding dry or irritating environments, such as cigarette smoke
- drinking plenty fluids to help prevent drying of the eyes
- not sleeping-in late, as corneal hydration from lid closure may be a factor affecting epithelial adhesion
- use of long-lasting eye ointments applied before going to bed
- Keep high quality artificial tears within reach at bedtime. If eyes feel stuck upon awakening, insert the tip of tears bottle slightly into inner corner of eye, gently squirting the tears, which will seep under the eyelid, often allowing opening of eyes without an erosion episode. Several repeated applications of tears may be necessary.
- Control air quality and humidity while sleeping.
- Avoid having an over ventilated room while you sleep.
- Having air flowing over your face, even with your eyes closed, can and will increase eye dryness.
- Cool, moist and still air is the best environment to prevent unnecessary evaporation of eye moisture.
Treatment of recurrent corneal erosion
The cornea has a remarkable ability to heal itself, so treatment is designed to minimize complications.
Lubricants
If the abrasion is very small, the doctor might just suggest an eye lubricant and a follow-up visit the next day. A very small abrasion should heal in one to two days; others usually in one week.
Antibiotics
However, to avoid a possible infection, an antibiotic eye drop may be prescribed. Sometimes additional eye drops may make the eye feel more comfortable.
“Patching”
Depending upon the extent of the abrasion, some doctors may patch the affected eye. It is very important to go for the follow-up checkup to make sure an infection does not occur. Use of contact lenses should not be resumed without the doctor's approval.
The immediate treatment goal of an acute corneal epithelial erosive episode is to promote epithelial regeneration and reestablish an intact ocular surface. This often must be maintained for sufficient time to allow reformation of the normal basement membrane complexes responsible for tight adhesion. It is important, however, not to confuse epithelial cysts or dots, which are characteristic of newly healed epithelium, with signs of anterior basement membrane dystrophy. An attempt at recording visual acuity should be made. For an abrasion, first examine the eyelid and the palpebral conjunctiva, ocular surface and fornices to rule out the presence of a foreign body. The area of erosion may appear like a wrinkled carpet or even as a frank epithelial defect. The size of the epithelial defect can be determined with the instillation of fluorescein.
Prognosis
Everyone should wear eye protection whenever this is recommended. This should be standard practice when using power tools and playing certain sports. Eyeglasses should be worn when whenever it is possible because the injury could occur in most amazing situations!
Contact lens wearers should be careful to follow their doctors' instructions on caring for and wearing their lenses. Ill-fitting or dirty lenses could lead to an abrasion, so patients should go for their prescribed checkups.
Sources & Links
- en.wikipedia.org/wiki/Corneal_erosion
- www.emedicine.com
- www.optometry.co.uk