Understanding Dellen
Dellen refers to a localized thinning of the cornea, the clear, dome-shaped front surface of the eye. It appears as a shallow, saucer-like depression, typically found at the limbus, the border where the cornea meets the white part of the eye (sclera). This condition is usually benign and localized.
Unlike more severe corneal conditions, dellen typically presents without significant inflammation or infection. The epithelium, the outermost layer of the cornea, usually remains intact over the thinned area. While it can cause foreign body sensation or mild irritation, it does not involve infectious processes.
Causes of Dellen
Dellen primarily develops from localized dehydration of the corneal surface, which disrupts the tear film. This disruption often occurs due to an elevated structure or lesion near the cornea that prevents the tear film from properly spreading. Examples include pingueculae, pterygia, subconjunctival hemorrhages, or filtering blebs from glaucoma surgery.
When the tear film is unstable or absent in a particular spot, the corneal epithelium repels water, leading to a dry area. This localized dryness causes dehydration and subsequent thinning of the underlying corneal stroma, resulting in dellen formation. Other contributing factors include dry eye syndrome, long-term contact lens wear, post-surgical changes (such as after cataract or strabismus surgery), and conditions affecting eyelid closure, like paralytic lagophthalmos. Idiopathic cases, occurring without an apparent cause, have also been observed, particularly in elderly individuals.
Treating Dellen
Treatment for dellen typically focuses on rehydrating the affected corneal area and addressing any underlying causes. The primary method involves frequent application of lubricating eye drops or ointments, often preservative-free, to help restore the tear film and promote rehydration. These can be applied every two to four hours, or more frequently in severe cases.
An eye patch may be used to help keep the eye moist and facilitate healing. A large diameter bandage contact lens can also be applied by an eye care professional to protect the cornea and maintain a more uniform tear film. If an elevated lesion is the root cause, its management or surgical removal may be considered to prevent recurrence. Surgical excision of a pterygium or pinguecula can eliminate the physical barrier disrupting the tear film.
Preventing Dellen and Recovery
Preventing dellen often involves managing existing risk factors and maintaining good ocular surface health. For individuals prone to dry eyes, consistent use of artificial tears and environmental modifications, such as avoiding direct airflow from fans or air conditioning, can help preserve tear film stability. Proper contact lens hygiene and adherence to wearing schedules are also important for contact lens wearers to prevent localized dryness. Regular eye check-ups allow for early detection and management of any elevated lesions or tear film abnormalities that could predispose to dellen.
With proper and timely management, corneal dellen usually resolves without long-term vision impairment. Most dellen heal within 10 to 15 days, though some may take up to four weeks for complete resolution. The rehydration of the corneal stroma typically leads to the restoration of normal corneal thickness and appearance.