What is corneal dehiscence and why do some keratoconus sufferers get it? Keratoconus patients who have previously had a corneal graft have an weaker corneal structure compared to an intact cornea.
The junction between the donor tissue and your own eye is inherently weak. This is true for both full-thickness grafts and deep lamellar grafts (partial thickness). If you subsequently sustain trauma to your eye, there is a much higher risk of the cornea rupturing.
This rupture – or split – in the cornea is called traumatic wound dehiscence.The corneal integrity is less compromised by a lamellar graft (compared to full-thickness or penetrating keratoplasty) and the risk of a rupture is lower. Rupture can occur before or after the sutures are removed after a corneal graft. Everything that’s inside your eye is supposed to stay in there! If the eye ruptures, various structures can bulge out of the wound, which often leads to a poor outcome for your vision.
Why does corneal dehiscence occur?
There are a number of reasons for this weakness.
• One is that the junction never knits together as tightly as the components of smooth, continuous intact corneal tissue.
• Another reason is that the cornea normally has no blood vessels to supply blood to the wound, which would allow for stronger wound healing to occur.
• Use of topical corticosteroids can also contribute to a weakness in the cornea.
• Finally, the alignment of the host and donor tissue at the wound can also be a factor in how strong the wound is. This is an area where the latest techniques make a difference. The latest graft surgeries use a femtosecond laser to create a perfect fitting edge between the two tissues – much like a jigsaw puzzle – and this leads to a stronger wound.
What are the complications if corneal dehiscence occurs?
When corneal dehiscence occurs it usually causes the wound to rupture extensively, requiring a surgical procedure to suture the wound closed again. The damage that occurs when the wound ruptures is usually very extensive. The internal structures of the eye – the iris, crystalline lens and vitreous can prolapse out through the wound and it is common for the retina to become detached. Surgical intervention is usually required to regraft the cornea, replace the crystalline lens or treat glaucoma caused by the trauma. The retina or vitreous may also need surgery to repair those structures. All of this leads to a poor visual outcome and in some cases blindness
How can I avoid traumatic wound dehiscence?
If you’ve had a corneal graft – even if it is not a full thickness graft – you should strive to minimise the chance of blunt trauma to your eyes. Contact sports, such as rugby, and any pursuits involving fast, unpredictable movement should be avoided, for example, mountain-biking, horse-riding, surfing or skiing. Protective goggles should be worn if this type of activity is pursued. Care should be taken with babies and small children not to allow their little fingernails near your eyes – especially when playing with them or strapping them into their car seat. A pair of glasses is good protection against this kind of trauma. Falls, assaults and accidents (such as walking into things) can also cause the blunt trauma required to bring about dehiscence.
The leading reason for corneal graft in patients under forty is keratoconus, while for over forties it is Fuchs’ corneal dystrophy. Corneal graft can be a solution to poor vision in advanced keratoconus but it comes with it its own set of problems, including an inherent weakness in the cornea. Corneal graft should only ever be performed as a last resort when adequate vision cannot be achieved with glasses or contact lenses fitted by an expert in keratoconus.