Corneal Dellen: Causes, Symptoms, and Available Interventions
Learn about corneal dellen, including its underlying causes, clinical presentation, and approaches for assessment and management.
The cornea plays a crucial role in maintaining clear vision, but certain conditions can disrupt its delicate balance. Corneal dellen is a localized thinning of the cornea that can cause discomfort and visual disturbances if left unaddressed.
Clinical Features
Corneal dellen appears as a shallow, saucer-like depression, typically near an elevated lesion or irregularity on the ocular surface. This thinning results from localized dehydration of the corneal stroma due to inadequate tear film coverage. The affected area often has a slightly grayish hue due to altered light transmission. Unlike corneal ulcers, the epithelial layer remains intact.
Patients commonly report foreign body sensation, mild irritation, and transient visual disturbances. Symptoms worsen with environmental factors like wind exposure or prolonged screen use, which further reduce tear film stability. While pain is usually minimal, persistent dryness can lead to complications if untreated.
Slit-lamp biomicroscopy helps identify corneal dellen, often found near limbal elevations such as post-surgical conjunctival grafts, pterygia, or scleral buckles. Fluorescein staining may show pooling in the depression without significant epithelial breakdown, distinguishing it from ulcers. Optical coherence tomography (OCT) provides cross-sectional imaging to quantify stromal thinning and assess adjacent corneal layers.
Common Contributing Factors
Corneal dellen develops due to factors that disrupt corneal hydration and surface contour. These include ocular surface irregularities, post-surgical anatomical changes, and tear film instability, all of which reduce tear distribution and cause localized dehydration.
Ocular Surface Changes
Structural irregularities on the ocular surface interfere with tear film distribution, creating dehydration-prone areas. Elevated lesions such as pterygia, pingueculae, or conjunctival chemosis act as physical barriers, preventing adequate tear coverage.
Inflammatory conditions like chronic blepharitis or ocular rosacea can alter tear film composition and promote surface irregularities. A study in Cornea (2021) found a higher incidence of corneal dellen in patients with chronic ocular inflammation, likely due to persistent epithelial stress. Prolonged contact lens wear, especially with rigid gas-permeable lenses, has also been linked to localized corneal dehydration.
Post-Surgical Alterations
Surgical procedures involving the conjunctiva and cornea can create anatomical changes that predispose certain areas to tear film insufficiency. Pterygium excision, scleral buckle placement, and conjunctival grafting can elevate tissue near the cornea, disrupting normal tear flow. Sutures and post-operative edema can further exacerbate tear film disruption, leading to stromal thinning.
A retrospective study in Ophthalmology (2022) found that nearly 12% of patients who underwent pterygium removal developed transient dellen within two weeks postoperatively. The study suggested that post-operative lubrication and early suture removal could reduce this risk. Additionally, procedures involving amniotic membrane transplantation or conjunctival flaps may affect tear film stability, requiring close monitoring.
Tear Film Instability
A stable tear film is critical for corneal hydration, and disruptions in its composition or distribution contribute to dellen formation. Dry eye disease, meibomian gland dysfunction, and autoimmune disorders affecting tear production can lead to inadequate lubrication.
A The Ocular Surface (2023) study found that patients with severe aqueous-deficient dry eye had a significantly higher risk of corneal dellen, especially near conjunctival elevations. The study emphasized the role of preservative-free artificial tears and punctal occlusion in management. Environmental factors like air conditioning, wind, and low humidity can further destabilize the tear film, increasing the likelihood of corneal dehydration.
Methods of Evaluation
Assessing corneal dellen requires clinical examination and imaging to differentiate it from other corneal conditions. Slit-lamp biomicroscopy allows direct visualization of the affected area, revealing a subtle indentation with a grayish hue. Evaluating surrounding ocular structures helps identify contributing factors like conjunctival grafts, pterygia, or post-surgical changes.
Fluorescein staining helps assess epithelial integrity. Unlike ulcers, which show intense staining due to epithelial defects, dellen exhibit fluorescein pooling without significant epithelial breakdown. Tear break-up time (TBUT) testing can further clarify whether poor tear distribution is contributing to dehydration.
Anterior segment optical coherence tomography (AS-OCT) provides high-resolution cross-sectional imaging, offering precise measurements of stromal thinning. Unlike slit-lamp examination, AS-OCT objectively quantifies tissue loss, aiding in monitoring progression and treatment response. In complex cases, anterior segment ultrasound biomicroscopy (UBM) can visualize deeper structures and confirm subclinical abnormalities affecting tear film stability.