Chemical Eye Injury
Chemical Eye Injury
Eye exposure to chemical materials may result in a chemical eye injury or chemical eye burn. Many chemical burns can cause only minor eye injury while other can cause severe damage to the eye with possible permanent vision loss and blindness.
The severity of chemical eye injury depends mainly on:
1- Type of substance caused it.
2- The duration of contact between substance and the eye.
3- What parts of the eye is involved and how deep is the chemical eye injury.
4- How the injury is treated.
Parts of the eye that can be involved in the chemical eye injury:
1- Eyelid and Eyelash.
3- the conjunctiva.
Chemical that penetrate deep through the cornea to the anterior chamber can cause cataracts and glaucoma.
Causes of Chemical Eye Injury
Most chemical eye injuries occur at work. Industries use a variety of chemicals daily. However, chemical injuries also frequently occur at home from cleaning products or other regular household products; these injuries can be just as dangerous and must be treated seriously and immediately.
Alkali agents with PH above 7 are lipophilic and therefore they can penetrate the eye deeper and more rapidly.
Hydroxyl ions of the alkaline material can saponify the fatty acids of cell membranes and destroy the proteoglycan matrix of corneal stroma which allow the alkali material to penetrate deeper into the Cornea and reach the anterior chamber and cause damage to trabecular meshwork, iris, lens and ciliary body. Damaged eye tissues secrete a lot of proteolytic enzymes that cause more inflammation and damage.
Example of alkali materials that can cause eye burns are sodium hydroxide which is found in drain cleaners, ammonia which is found in fertilizers and household cleaning solutions and calcium hydroxide which is found in cement and plaster.
Acids damage the eye but they are less harmful than alkali eye burns. They precipitate corneal proteins which act as a barrier and prevent further penetration of the acid.
You might have some of acidic chemical products at your home such as vinegar, acetic acid in nail polish remover, hydrofluoric acid in glass polish or sulfuric acid in automobile batteries.
How to protect your eye from chemical eye burn
1- Always wear eye protection
Most of chemical eye burns are avoidable. You should always use protective goggles every time you with chemicals. Regular Prescription glasses do not provide reliable protection, because they don’t cover the whole eye. Appropriate safety eye wear are the best way to protect your eye.
- Safety glasses. These glasses are different from regular prescription glasses. They have lenses that are resistant to break into small pieces. These glasses also have stronger frames and side shields.
- Safety goggles. They are made from smash-resistant materials and seal against the face. Some styles of safety goggles are large enough to be worn over the top of prescription glasses.
- Face shields. They offer maximum protection against splash injury. In some cases, safety goggles are also worn. Face shields should always be used when you are working with dangerous chemicals, such as cryogenic fluids, corrosive liquids or biological materials.
2- Don’t wear contact lenses while working with chemicals as the contact lens can absorb the chemical and concentrate it on the eye surface.
3- Store and dispose of the chemicals safely.
First aid for chemical eye burn
1- Eye irrigation
- The goal of irrigation is to normalize the PH of the eye and washout any chemicals. Irrigate your eye with running water for at least15 to 20 minutes. It is better to use sterile emergency eyewash or isotonic saline solution but if they are not available you can use tap water.
- Keep your eye wide open as possible as you can and use your fingers to hold your eyelids apart.
- If you wear contact lens, you should remove it as soon as possible.
- During irrigation, you should move your eye in all direction so the fluid can reach all parts of your eye including the conjunctival sac.
2- Seek medical attention as soon as possible
In the emergency department, the medical staff will start irrigate your eye again and then when they are sure the PH of your eye is normal they will start the physical examination.
Eye Irrigation in the emergency department
- Topical anesthetic can be applied prior to irrigation to increase patient comfort.
- Speculum can be used to keep your eyelid open.
- A device called Morgan therapeutic lens can be used to ensure better eye irrigation. This lens is attached to IV tubing.
Types of Irrigating fluid that can be used in the emergency department
- Hypotonic solutions can increase water movement into the cornea and also further diffusion of chemical material into the eye and increased corneal edema.
- Isotonic solution such as normal saline, balanced saline solution, Ringer lactate and phosphate buffer solution.
- Hypertonic solutions increase the osmotic pressure to move water and dissolved chemicals out of corneal stroma and reduce corneal edema. These solution normalize the PH of the eye better than normal saline and phosphate buffer solutions.
Examples of hypertonic solution are borate buffer solution called Cedderroth eye wash, Previn solution and Diphthorine.
Diphoterine is a hypertonic solution that can be used in the treatment of chemical eye burns by acid and alkali materials. It reduces pain, inflammation and neutralize the PH of corneal stroma to normal levels.
1- The first step is to check pH of both eyes. If the pH is not within the normal range, then the eye must be irrigated again to till the pH in normal range (between 7 and 7.2).
2- The doctor will check the eye for any chemical remaining especially in the fornical sac. Eyelid should be inverted for examination.
3- Parts of the eye involved and depth of injury should be assessed.
4- If possible, the intraocular pressure should also be examined as alkali chemical burns can penetrate deep in the eye to reach the anterior chamber.
Grades of Severity
Grades are very important to describe ocular surface, guide treatment and assess the prognosis. Grades depend on:
- Degree of limbal ischemia.
- Corneal haze, whether you can see the iris and anterior chamber through this corneal haze.
The corneal epithelium is involved only without limbal ischemia. The cornea is clear. This grade has excellent long-term visual prognosis.
There is mild corneal haze with a good view of anterior chamber structures. There is focal limbal ischemia with can lead to neovascularization. The prognosis is good.
There is significant ischemia of most of the limbus with corneal haze that limits the view of anterior chamber structures. There is extensive corneal neovascularization and conjunctivalization.
There is total loss of limbal stem cells with total destruction of the conjunctival epithelium. The cornea is completely opaque and corneal melting is one of the known complications of this grade. This grade has the worst prognosis.
Treatment of Chemical eye injury
Treatment depends mainly on the grade of injury. The goal of treatment is to promote the healing of the external part of the cornea or corneal epithelial layer, reduce pain and inflammation and to prevent bacterial infection.
1- Topical antibiotic ointment such as bacitracin or erythromycin typically is prescribed. In severe cases, fluoroquinolone such as vigamox can be used.
2- Preservative-free artificial tears should be used frequently to reduce the symptoms of burning, foreign body sensation and irritation.
3- Topical steroid such as pred forte eye drops should be used to control inflammation and facilitate re-epithelialization. Topical corticosteroids should be tapered and stopped after days 10 to reduce the risk of corneal melting.
4- Topical cycloplegic agent such as short acting such as cyclopentolate or long acting such as atropine sulfate should be used to reduce eye pain, along with oral pain medications.
5- The intraocular pressure should be controlled by eye drops or oral medications. Surgical operation can be done later.
6- Debridement. Necrotic or dead tissue of the corneal epithelial and conjunctival epithelium should be removed.
7- Ascorbic acid is very important factor in collagen synthesis. Chemical burns can cause deficiency of ascorbic acid in the eye. It can be used as a topical drop or orally to prevent corneal ulceration and melting and to promote corneal healing.
8- Doxycycline has antibacterial and anti-inflammatory properties. It reduces the effects of matrix metalloproteinases (MMPs) that helps to reduce inflammation and prevent corneal melting.
9- Citrate drops. Citrate works as calcium chelator and it inhibits collagenases and prevents corneal melting. Calcium promotes the activity of Polymorphonuclear leukocytes which release many proteolytic enzymes that dissolve the collagen in corneal stroma and cause corneal melting. It attaches to calcium and therefore decrease proteolytic activity.
10- Platelet rich plasma eye drops. It has many growth factors that help in the healing of corneal epithelial layer.
- Conjunctival and Tenon’s transposition to promote limbal vascularity which helps in corneal epithelial layer healing.
- Amniotic membrane transplantation (AMT). AMT has many growth factors that help to reduce limbal and corneal stromal inflammation rapidly, prevent the formation of corneal neovascularization and symblepharon and promotes the generation of corneal epithelial layer.
- Limbal stem cell transplant. Limbal stem cells are responsible for the repopulating the corneal epithelium and for inhibition of conjunctival growth over the cornea. Limbal stem cell can be used from the healthy contralateral eye or from other donors. Studies showed that Limbal stem cell transplant in chemical eye help to reduce in corneal vascularity, promote corneal epithelialization and improve corneal opacity.
- Cultivated oral mucosal epithelial transplantation (COMET). The mocus membrane is taken from the patient’s own buccal mucosa. This treatment can be used to reduce inflammationa and promote corneal re-epithelialization.
- Boston Keratoprosthesis: can be used in severe corneal burns and total loss of limbal stem cells.
Long term complications of Chemical Eye Injury
Glaucoma is a common complication and can occur in 15%-55% of chemical severe burns. The mechanisms of glaucoma are contraction of the anterior segment of the eye secondary to chemical and inflammatory damage, inflammation of the trabecular meshwork and damage to the trabecular meshwork itself.
- Dry eye
Dry eye occurs due to loss of conjunctival goblet cells, which are responsible for the secretion of mucus layer of the tear film.
- Damage to the eyelids and conjunctiva
Chemical damage to the conjunctiva can cause:
- Conjunctival scarring and shortening of the fornix with the formation of the symblepharon which is adhesion between the conjunctiva that cover the sclera and the conjunctiva the lined the inner surface of the eyelid.
- Cicatricial entropion or ectropion that can occur weeks to months after the chemical injury