Keratoconus: tissue engineering and biomaterials

Abstract

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. The prevalence of KC is stated to be 1 in 2000 persons worldwide; however, numbers vary depending on size of the study and regions. KC appears more often in South Asian, Eastern Mediterranean, and North African populations. The cause remains unknown, although a variety of factors have been considered. Genetics, cellular, and mechanical changes have all been reported; however, most of these studies have proven inconclusive. Clearly, the major problem here, like with any other ocular disease, is quality of life and the threat of vision loss. While most KC cases progress until the third or fourth decade, it varies between individuals. Patients may experience periods of several months with significant changes followed by months or years of no change, followed by another period of rapid changes. Despite the major advancements, it is still uncertain how to treat KC at early stages and prevent vision impairment. There are currently limited tissue engineering techniques and/or "smart" biomaterials that can help arrest the progression of KC. This review will focus on current treatments and how biomaterials may hold promise for the future.

Figure 1

Penetrating keratoplasty. (A) Distorted cornea removed; (B) Corneal graft placed in recipient bed; (C) “Stay sutures” placed; (D) Single running suture in place at end of surgery.

Figure 2

Deep anterior keratoplasty (DALK). (A) After partial trephination, a cannula is inserted deep in the corneal stroma; (B) Air injection through the cannula separating Descemets membrane from stroma; (C) Manual dissection ensuring that only the recipient’s Descemets membrane is preserved; (D) Lamellar donor graft sutured in place at end of surgery.

Figure 3

Intracorneal ring segments. Scheimpflug image inserts show keratoconic cornea before and after insert of one intracorneal ring segment. Color images show corneal power before and after a segment insert and the change in corneal power. Note that corneal power after segment implantation is more regular.

Figure 4

Application of riboflavin drops during corneal cross linking procedure.