Corneal Ulceration. Client Information Sheet Copyright Bilton Veterinary Centre All rights Reserved. What is the cornea?

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1 What is the cornea? Corneal Ulceration The cornea is the central clear part of the eye that is surrounded by the white of the eye called the Sclera. Looking through the cornea, you can see the coloured part of the eye (Iris) and also the Pupil which is the hole in the iris, which allows light to pass through to the back of the eye and the retina. What is corneal ulceration? Corneal ulceration is used to describe a condition whereby the integrity of the cornea is damaged or compromised. The clear cornea is actually made up of three layers a thin outer epithelium, the thicker stroma and then the incredibly thin inner endothelium (called Descemet s Membrane.) An ulcer (or any injury to the cornea) is classified as to which structures have been damaged. A Superficial Ulcer is where just the outer epithelium is partially damaged and the stroma is not exposed. (These are quite rare as the outer layer is very thin) A Shallow Ulcer is where the epithelium has been breached and the stroma is exposed. A Deep Ulcer is where both the outer epithelium and the stroma are damaged and the inner endothelial membrane is exposed. Corneal Rupture is where all three layers are damaged and fluid from within the eye can leak out. What causes corneal ulceration? Corneal ulceration can be caused by: Physical trauma - such as a cat scratch, or thorn Chemical trauma such as being splashed with a caustic solution or acid/alkali. Anatomical issues such as turned in eyelids (entropion) or poorly placed eyelashes (distichiasis) Foreign body trapped under the eyelids (such as grass seeds) Bacterial infection Viral infection such as Herpes Virus in cats. Hereditary/Congenital disposition in certain breeds Age related degeneration of corneal health. Dry Eye (lack of tear production) Page 1 of 6

2 What are the signs of corneal ulceration/injury? Signs of ocular pain including squinting, holding eyelids closed, rubbing at the eye, red conjunctiva, watering eye, increasing blinking rate, protrusion of third eyelid. The whites of the eye may look red and vessels can look engorged. If infection present then you may have a purulent discharge from the eye. You may see an abnormal roughened/irregular area within the cornea itself. How are corneal ulcers diagnosed? If you are suspicious that something is wrong with your pet s eye then you must get it checked by a vet as soon as possible. To examine the eye your vet may do some/all of the following: Thorough visual exam of the eye, eyelids and surrounding tissues Corneal exam using an ophthalmoscope Examination of the deeper structures of the eye, including the anterior chamber, the lens, the iris and the posterior chamber and retina. Fluorescein test (see below) What is the fluorescein test? The fluorescein test is where a special dye is placed onto the eye. Fluorescein only sticks to the stromal layer, and so this means that when you apply it to the normal cornea it will just run off the healthy epithelium. If the epithelium is damaged and the stroma is exposed, the dye will stick to it thus revealing its position. This can be shown by using a blue filtered or ultraviolet light. Page 2 of 6

3 Interestingly as the dye doesn t stick to the inner endothelium, you can get a bullseye appearance with these really deep ulcers where the central area appears clear. These are really serious as it means that the eye is VERY close to perforating. Figure 1. A shallow ulcer of the right eye, showing up bright green after the application of the Fluorescein Dye. This means the epithelium is damaged, exposing the stroma. How are corneal ulcers treated? Many ulcers will heal fairly easily with time and topical medication. Treatment will often depend on the type, cause and progression of the ulcer. Usual treatment for ulcers may involve: Topical Antibiotic treatments. These aim to either remove the primary inciting cause (if bacterial) or more usually to keep bacterial infection away from the damaged tissue whilst it is healing. Lubrication. This removes a lot of the discomfort from the eye, by minimising the effect of the eyelids rubbing over the damaged corneal tissue. Pain relief. These are usually drugs called Non-Steroidal Anti-Inflammatories (NSAID) and can be given topically or systemically if very painful. Contact Lenses. We often use special soft lenses (called bandage lenses) that are relatively easy to apply and act to protect the cornea from the rubbing effect of blinking as it heals. EDTA Plasma/Anticollaginases. These are used for severe bacterial ulcers which are caused melting ulcers. Ulcers can melt as certain bacterial infections will literally dissolve the cornea as they spread. This treatment is made using a chemical (EDTA) and plasma extracted from blood. This can either be the animal s own blood or a donor. Treatment may need to be done hourly and so can be quite intensive. Surgery. Severe ulcers may require a procedure such as a Conjunctival Pedical Graft or a Corneo-Scleral Transposition. A Conjunctival Pedical Graft is where an area of healthy conjunctival tissue is taking from Page 3 of 6

4 the sclera (the white of the eye) and then rotated and carefully sutured over the ulcer. This acts as a kind of sticking plaster and provides structural support to the damaged cornea as well as providing lots of blood vessels and healing properties directly to where it is needed ie right over the ulcer. Although this can be performed in general practice, we will often refer these cases to a specialist with access to a special operating microscope as it is very fine and delicate surgery. What are Indolent Ulcers? In certain breeds and many older dogs, we see a type of ulcer called an indolent ulcer. Indolent ulcers are typically shallow ulcers that can occur spontaneously or sometimes due to a previous corneal insult. They are characterised by their seemingly absent/very slow attempts at healing. Spontaneous indolent ulcers are called Superficial Chronic Corneal Epithelial Defects (SCCEDs). SCCEDs are usually caused by an inherent weakness of the glue that sticks the epithelium to the stroma. This means that the epithelium ends up sliding over and separating from the stroma with normal blinking and eye movement. Eventually this causes the epithelium to break down with resultant ulceration. New epithelium has an inability to adhere to the underlying stroma and so this results in abortive and prolonged healing. These types of ulcers often have a central area where the epithelium is missing, and then a peripheral flap of loose non-adhered epithelium around the edge. These are usually seen in older dogs (over the age of 7 years old) and can be seen in any breed, although the fact they are very common in Boxers, explains why these are sometimes called Boxer Ulcers. How are Indolent Ulcers/SSCEDs treated? Intervention is always required with these ulcers as otherwise they never heal properly. The aim of treatment is to try and force the epithelium to stick to the stroma again. This usually involves removing any loose epithelium and also trying to remove a small amount of the underlying stroma to make it sticky enough to receive the new epithelium as it heals. Topical Debridement. Using some local anaesthetic drops, a sterile cotton bud is used to gently scrub the ulcer. This removes all the loose non-adhered epithelium and also roughens the stroma. This is usually tolerated very well and is normally done in a routine consultation. We will normally attempt this procedure a couple of times before moving onto a different method if things are not successful. Diamond Burr Keratectomy. Again we usually perform this under local anaesthetic, but some dogs may require sedation as well. We use a very fine diamond burr and mechanically remove the loose epithelium again along with a very small amount of the stroma as well. This is very similar in principle to the debridement with a cotton bud, but is a bit more of an aggressive treatment and often has very good results. Phenolic Debridement. With this technique, any loose epithelium is removed again with a cotton bud, but this time the periphery and the stromal bed is very briefly cauterised with the caustic chemical phenol. The eye is then flushed with copious saline to remove all traces of the chemical. This is usually done under heavy sedation or general anaesthetic. Page 4 of 6

5 Punctate/Grid Keratotomy. Even after debriding, some ulcers still may not start to heal properly. In these cases we may perform a keratotomy. This is where (usually under heavy sedation or general anaesthetic), a tiny needle is used to make a series of shallow nicks or scratches across the surface of the ulcer and the surrounding epithelium. By causing this diffuse microtrauma to the eye, it aims to both stimulate the healing process, and also to provide a series of button-holes that the new epithelium can adhere to as it creeps across the surface of stroma. Thermokeratoplasty. With severe cases where we can tell that the corneal health is very poor to start with, or with very stubborn refractory cases, we may refer to a specialist who can perform this procedure which effectively spot-welds the epithelium back onto the stroma again. Figure 2 - Cornea immediately after having had a grid keratotomy performed. Page 5 of 6

6 What is the prognosis? Corneal ulceration always need rapid and accurate diagnosis and treatment needs to be instigated quickly and aggressively if necessary. Close attention needs to be made to the instructions for medication - particularly the frequency and order that treatment needs to be given. This can involve having to give treatment every hour or so in some instances; even through the night! Ulcers that heal quickly and with no complications are often straightforward to manage and should cause no long term problems. With some deep ulcers or severe ulcers, you may end up with a corneal scar which often looks like a small puff of smoke within the cornea itself. This is a minor issue and is not likely to cause any long term issues. If the ulcer becomes full thickness the eye can become perforated; then this is often a terminal event and usually results in the eye needing to be removed. Every effort is always made to prevent ulcers from becoming full thickness. Certain breeds such as Boxers, are predisposed to ulcers and short-nosed/bulbous eyed dogs such as Pugs, Cavaliers, Shih-Tzu s etc are more likely to suffer trauma to the eye and so it is certainly possible for these types of dogs to suffer more than one episode of eye ulceration. Page 6 of 6