Staging
The classification of the eye burn is divided into four stages. The classification is based on the severity and depth of the injury and the expected prognosis. Stage I and II describe rather minor and superficial injuries.
They are characterized by hyperemia (excessive blood supply to the affected area due to dilated vessels) and chemosis (edema of the conjunctiva, fluid retention in the tissue). Furthermore, minor erosions of the cornea are visible. These are crater-like injuries of the cornea, caused by the chemicals acting on it.
The epithelium often takes on a lighter greyish-glass colour. Stages III and IV are more severe burns that affect a larger area and especially deeper layers of the eye. In contrast to the slight damage, stages III and IV do not show hyperemia, but rather a lack of blood circulation (ischemia).
Thrombi (clumps of blood platelets) are often found in the vessels, which can lead to vascular occlusion. Damage to the superficial and deeper parts of the eye also causes changes in the iris and lens. Discoloration of the iris and persistent clouding of the lens occur.
In addition, necroses (areas with dead cells) are found in the conjunctiva. The injury or inflammation may include involvement of the anterior chamber of the eye. An exudate (fluid with inflammatory cells, pus) is formed.
Depending on how corrosive the substance was, there can be no damage at all, ranging from slight to severe changes to the most serious consequences, including blindness. In general, caustic burns are much more severe than acid burns, as they can penetrate further into the depths of the eye. Light burns cause no or only slight superficial corneal damage.
The blood circulation of the conjunctiva is then intact and consequential damage is not to be expected. However, medium to severe burns can lead to severe corneal abrasion. The cornea can also be clouded (possibly permanently).
A reduced blood supply to parts of the conjunctiva is possible. Sometimes the conjunctiva of the eyeball and eyelid also sticks together (symblepharon). The complete loss of the corneal surface and the conjunctiva at the corneal edge is caused by an extremely severe chemical burn.
There is no blood circulation and the cornea is completely clouded. Conjunctival adhesions form (symblepharon) and especially caustic burns also cause damage to the inside of the eye (lens, iris, eye pressure increase). Blindness is possible.
Follow-up
Once the first aid measures have been carried out and a doctor has been consulted, further treatment can be given. The use of antibiotics is important to prevent further infections of the injured eye. A detailed examination of the eye by the doctor is relevant to assess the stage of the burn.
If there is a higher stage, i.e. a deeper injury with necrotic areas, surgical treatment is often necessary. Surgical removal of the destroyed tissue must therefore be performed. This can be done under local anesthesia, but also under general anesthesia.
In the case of more extensive damage, a transplant can be performed on the eye. This means that the cornea or conjunctiva is restored by other tissue. Amniotic membrane transplantation is a principle that has been used for some time.
Here, placental tissue (endometrial cells that divide very well) is applied to the areas where the necroses have been removed. The idea behind this is that new epithelium (superficial protective cell layer) is better formed and inflammation and pain are reduced. A more recent method is Tenon’s plastic surgery, in which functional connective tissue (intermediate and supporting tissue) from the eye is placed on the surface of the eye and fixed in the depth of the eye.
It has been observed that further necroses in the area of the anterior eyeball (bulbus oculi) occurred less frequently. However, a complete new formation of corneal epithelium rarely occurs, which is why the use of a donor or artificial cornea is necessary. The use of a corneal graft is generally relevant when the cornea has become irreversibly cloudy due to the burn.