Corneal dellen are peripheral excavations in the cornea occurring secondary to tear film disturbance caused by limbal elevations.
“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. 
- Secondary to paralimbal elevation due to 
- Episcleritis or scleritis
- Thick pingecula or pterygium
- Subconjunctival hemorrhage
- Subconjunctival injections
- Filtering blebs
- Suture granuloma
- Limbal tumours
- Lesions like angioma
- Subconjunctival silicone oil
- Post-surgery – cataract/rectus muscle surgery/trabeculectomy 
- Long term contact lens wear 
- Following paralytic lagophthalmos
- Secondary to severe conjunctival chemosis
- Idiopathic, in elderly persons
- Ocular trauma
- Paralimbal elevation causes localised break in the precorneal oily tear film especially a focal absence of the mucin layer.
- Cornea epithelium is hydrophobic and in absence of mucin will repel water and localized dehydration occurs producing a dry spot leading to a dry epithelial surface.
- Ocular surgery
- Ocular trauma
- Previous ocular complaints
- Contact lens wear
- Foreign body sensation
Slit lamp examination reveals 
- 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
- Base of lesion appears hazy and dry
- 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 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
- They usually last only for 24-48 hours and disappear spontaneously.
- However, they can also become chronic with breakdown of epithelium, inflammation of stroma and scarring.
- They usually heal in 2 weeks.
- If left untreated, the underlying corneal stroma may undergo secondary degeneration, leading to corneal scarring and vascularisation and loss of vision. 
- Can lead to corneal perforation. 
Treatment needs to be rapid to avoid the above mentioned complications.
- Reduction of the paralimbal elevation i.e treating the underlying cause
- Rapid re-establishment of the mucin layer and a hydrophilic corneal surface by:
- Frequent lubrication with artificial tears and ointments.
- Patching of eye can help in faster healing.
- Large diameter Bandage contact lenses can also help.
- Dellens following filtering blebs – limbal elevation cannot be changed in these cases as bleb is necessary. These patients benefit with frequent artificial tears.
Surgical excision of paralimbal elevations like pterygium, pingecula, limbal tumours etc.
Minor procedures like tarsorraphy for rapid healing can be considered.
- Fuchs, Adalbert. "Pathological dimples (“Dellen”) of the cornea." American Journal of Ophthalmology 12.11 (1929): 877-883.
- Mai G, Yang S. Relationship between corneal dellen and tearfilm breakup time. Yan Ke Xue Bao 1991;7(1):43-6.
- Accorinti M, Gilardi M,Giubilei M, De Geronimo D, Iannetti L. Corneal and scleral dellen after an uneventful pterygium surgery and a febrile episode. Case Rep Ophthalmol. 2014;5(1):111‐115.
- Fresina M, Campos E. Corneal “dellen” as a complication of strabismus surgery. Eye (Lond) 2009;23(1):161-3.
- Jampel, Henry D., et al. "Perioperative complications of trabeculectomy in the collaborative initial glaucoma treatment study (CIGTS)." American journal of ophthalmology 140.1 (2005): 16-22.
- Ng LH. Central corneal epitheliopathy in a long term, overnight orthokeratology lens wearer: a case report. Optom Vis Sci 2006;83(10):709-14.
- Baum, Jules L., Saiichi Mishima, and S. Arthur Boruchoff. "On the nature of dellen." Archives of Ophthalmology 79.6 (1968): 657-662.
- Corneal 'dellen' as a complication of strabismus surgery. Fresina M, Campos ECEye (Lond). 2009 Jan; 23(1):161-3.
- Dua HS, Forrester JV. Clinical patterns of corneal epithelial wound healing. Am J Ophthalmol 1987;104:481
- Kymionis, George D., et al. "Treatment of corneal dellen with a large diameter soft contact lens." Contact Lens and Anterior Eye 34.6 (2011): 290-292.