Dellen is-
Impaired eyelid function. It is seen in patientswith Bell's palsy, exposure keratitis, dellen,symblepharon, pterygium, nocturnal lagophthalmosand ectropion. REF:Comprehensive ophthalmology,20th edition,AK Khurana,pg no.365.
Localized thinning of peripheral cornea
b) Raised lesions in corneo limbal junction
Age related macular degeneration
Marginal keratitis
Cornea and sclera