*5.2.3.1 Penetrating keratoplasty (PK)*

Penetrating or lamellar keratoplasty techniques are used depending on the extent of corneal scarring [15]. PK provides long term good vision but has slow visual rehabilitation from residual astigmatism and anisometropia [15]. Both PK and DALK tend to worsen any existing ocular surface problems, as both involve surface incisions, injury of corneal nerves, placement of long-lasting sutures, and requiring post-operative topical corticosteroids [18]. Despite the facts that long term graft survival following PK for keratoconus is good, averaging 97% at 5 years, 90% at 10 years and 80% at 20–25 years, most of the patients with advanced KC are transplanted early in life, therefore it is more likely that more than one graft may be required over their lifetime ultimately [18].
