Corneal Dellen

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Article initiated by:

Sashwanthi Mohan MBBS, DNB, FICO

All contributors:

Madhuvanthi Mohan, Sujatha Mohan, Vatinee Y. Bunya, MD, MSCE, Colleen Halfpenny, M.D., Augustine Hong, MD, Sashwanthi Mohan MBBS, DNB, FICO, Benjamin B. Bert, MD, FACS

Assigned editor:

Benjamin B. Bert, MD, FACS

Review:

Assigned status Up to Date

 by Benjamin B. Bert, MD, FACS on July 25, 2024.

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Contributing Editors:	add

Corneal dellen are peripheral excavations in the cornea occurring secondary to tear film disturbance caused by limbal elevations.

Disease Entity

ICD-10: H18.49

Disease

“Dellen” dimple was first described by Ernst Fuchs as shallow, saucer-like excavations at the margin of the cornea.

They are thought to occur due to localized tear film instability especially the mucin layer and dehydration.

Figure 1: Saucer shaped depression in the peripheral cornea with clearly defined margins called dellen. Photo Courtesy: Rajan Eye Care Hospital, Chennai

Etiology

1. Secondary to paralimbal elevation due to
   • Episcleritis or scleritis
   • Thick pingecula or pterygium
   • Subconjunctival hemorrhage
   • Severe conjunctival chemosis
   • Subconjunctival injections
   • Filtering blebs
   • Suture granuloma
   • Limbal tumours
   • Lesions like angioma
   • Subconjunctival silicone oil
2. Post-surgery – cataract/rectus muscle surgery/trabeculectomy
3. Long term contact lens wear
4. Following paralytic lagophthalmos
5. Idiopathic, in elderly persons
6. Ocular trauma

Pathophysiology

• Paralimbal elevation causes localised break in the tear film, especially a focal absence of the mucin layer.

• Cornea epithelium is hydrophobic and in absence of mucin will repel water causing a dry spot and eventually localized dehydration.

• This is followed by thinning of cornea in that area forming a dellen.

Diagnosis

History

History of:

• Ocular surgery
• Ocular trauma
• Previous ocular complaints
• Contact lens wear

Symptoms

• Redness
• Foreign body sensation
• Grittiness

Signs

Slit lamp examination reveals

Figure 2: Slit view of the dellen showing the well defined depression in the peripheral cornea Photo Courtesy: Rajan Eye Care Hospital, Chennai

• Depressed region with clearly defined margins
• Around 2-3 mm in diameter
• Commonly on the temporal side, forming ellipses parallel to the limbus
• Corneal wall is steep, limbal wall is sloping
• Epithelium is usually intact overlying a thinned area of dehydrated stroma
• Fluorescein pools in the depression and at times there is overlying staining
• Epithelium within the dellen can either be clear or opaque (hazy and dry) in appearance
• Corneal sensation can be decreased with the dellen compared to rest of the cornea
• Adjoining vascular loops and conjunctival vessels can be injected
• Adjacent cornea is usually normal

Figure 3: Slit lamp photo with cobalt blue filter showing fluorescein pooling in the dellen Photo Courtesy: Rajan Eye Care Hospital, Chennai

Progression

• Dellens usually last for 24-48 hours and disappear spontaneously. Most will heal within 2 weeks.
• However, they can become chronic with breakdown of epithelium, inflammation of stroma and scarring.

Complications

• If left untreated, the underlying corneal stroma may undergo secondary degeneration, leading to corneal scarring and/or vascularisation with accompanying loss of vision.
• Rarely can lead to corneal perforation.

Management

Treatment needs to be initiated expeditiously to avoid the above mentioned complications.

General treatment

• Reduction of the paralimbal elevation i.e. treating the underlying cause

Medical therapy

• Rapid re-establishment of the mucin layer and a hydrophilic corneal surface by:
  • Frequent lubrication with artificial tears and ointments
  • Patching the eye
  • Large diameter bandage contact lens

• Dellens following filtering blebs – limbal elevation cannot be changed in these cases as bleb is necessary. These patients benefit with chronic frequent use of artificial tears.

Figure 4: Corneal dellen which was managed with tissue adhesive and bandage contact lens. Photo Courtesy: Rajan Eye Care Hospital, Chennai

Surgery

Surgical excision of paralimbal elevations like pterygium, pingecula, limbal tumours etc.

Minor procedures like tarsorraphy to limit ocular surface exposure can be considered.

Additional Resources

• Boyd K, Pagan-Duran B, Hazanchuk V. Lubricating Eye Drops. American Academy of Ophthalmology. EyeSmart/Eye health. https://www.aao.org/eye-health/treatments/lubricating-eye-drops-2. Accessed February 28, 2023.