Dr. Michael Saidel, a comprehensive ophthalmologist, joined the North Bay Eye Medical Staff in 2016. He is board certified in Ophthalmology and specializes in diseases of the cornea, refractive surgery and uveitis.
The cornea is an integral part of the eye. It helps the eye to focus properly and causes the involuntary reflex for the eyelids to close. A healthy cornea is needed for a healthy eye. The cornea consists of a highly ordered group of cells and proteins with essential nerve endings. It is the transparent front part of the eye; covering the pupil, iris, and anterior eye chamber. Its transparency allows it to refract the right amount of light in the right direction; even a slight change in this consistency results in altered vision. If transparency lessens, blurred vision can result.
The human cornea has five layers in order, listed outermost to innermost:
5 Layers of The Cornea
- Corneal Epithelium – The cornea’s outermost region makes up approximately 10 percent of the tissue’s thickness.
- Bowman’s Layer – This sturdy layer of collagen protein fibers is beneath the membrane of the epithelium. If this layer is damaged, it can develop a scar when it heals. If the scar is towards the middle of the eye, it often causes some vision loss.
- Corneal Stroma –The stroma layer comprises 90 percent of the cornea’s tissue. The unique shape of this layer and lack of blood vessels produce the cornea’s transparency.
- Descemet’s Membrane – This layer is a thin piece of tissue. Its main function is to protect against injuries and infection. The Descemet’s membrane consists of collagen fibers.
- Corneal Endothelium – An extremely thin layer, this is the innermost layer of the cornea. These cells are necessary in order to keep the cornea transparent.
If any injury breaks through to a deeper layer of the cornea, the healing process takes longer and may result in the following symptoms: blurred vision, pain, redness, sensitivity to light and tearing. More serious injuries will produce corneal scarring, which can cause distorted vision or even dramatically impaired vision. If you experience any of these symptoms, please consult an eye care professional.
Here is a comprehensive list of five cornea conditions and typical symptoms.
Allergies affect almost everyone at some point in their life. Typically eye allergies are triggered by one of the following:
- Indoor allergens like dust, mold and dander
- Outdoor allergens like pollens
- Irritants like smoke and perfume
Symptoms: Itching, redness, burning, clear or watery discharge, mucus discharge, sensitivity to light, puffiness, hazy vision, and foreign body sensation. A foreign body sensation is when a person feels there is something in their eye even when there is not.
2. Ocular Surface Disease / Dry Eye
One of the most common eye conditions that people experience is dry eye. For some, the condition is persistent and extremely painful.
Tears provide a crucial role in eye health. They wash away dirt and irritants while keeping the eye’s surface moist and clean. This prevents potential irritation, damage or even infections caused by injuries or bacteria.Tears consist of three elements to protect the overall health of the eye:
- An oily layer – lipid
- A watery layer – aqueous
- A coating layer – mucin.
When the eye no longer produces enough tears or the quality of tears necessary to maintain eye health, everyday activities may become difficult and/or painful.Common causes for dry eye include: allergies, contact lens use, skin disease around the eyelids, exposure to chemicals or tobacco smoke, and some medications. Age is also a factor as most people over the age of 65 have experienced dry eye.
Symptoms: Red eyes, redness of the eyelids, foreign body sensation, itching, eye discomfort, hazy vision and burning or stinging in the eye.
Eye infections can affect one or both eyes and any part of the eye. In order to maintain its transparency, the cornea, unlike most other tissues in the body, does not contain blood vessels. This puts the cornea at a particular disadvantage when it comes to fighting infections. Two common eye infections are conjunctivitis – also known as pink eye – and corneal ulcers. Viral infections of the cornea including herpes simplex (the cold sore virus) and herpes zoster (the virus responsible for shingles) can severely affect vision and comfort.
Symptoms: Redness, itching, swelling, discharge, pain, or distorted vision.
4. Herpes Zoster (Shingles)
This condition is an infection caused by the common chickenpox virus or the varicella-zoster virus. Once someone contracts the virus, it remains inactive within the central nervous system and if reactivated, produces an agonizing blistering rash called shingles. Anyone exposed to the varicella-zoster virus can develop herpes zoster; however, there are two general risk factors: 1) advance age and 2) a weakened immune system. An essential note about herpes zoster is that corneal damage can appear once the shingles have disappeared. It is important to schedule a follow-up appointment if you’ve experienced facial shingles to avoid any long-term effects.
Symptoms: High temperature, painful rash, eye redness, light sensitivity, blurry or foggy vision. Decreased corneal sensitivity can be caused by herpes zoster and is often permanent.
5. Corneal Dystrophies
There are more than 20 different types of corneal dystrophies – each one affecting different parts of the cornea. With a corneal dystrophy, one or more pieces of the cornea’s regular clarity changes due to a shape change or an increase in cloudy-like material within the eye. A dystrophy is typically inherited and can affect both eyes equally. Usually dystrophies progress gradually.
Symptoms: Symptoms vary depending on the dystrophy. Some cause severe visual impairment, while others are discovered during regular checkups because they show little to no symptoms in the early stages. Still other dystrophies are periodic and cause pain from time to time but leave no permanent loss of vision.