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M. Harissi–Dagher, B.F. Khan, C.H. Dohlman; The Importance of Nutrition to Corneal Grafts When Used as a Carrier of the Boston Keratoprosthesis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3932.
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Dellen formation, epithelial defects, stromal thinning, and melt allowing leaks have historically been frequent in the corneal tissue around a Keratoprosthesis (KPro). Autoimmune diseases such as Stevens Johnson Syndrome (SJS) and Ocular Cicatricial Pemphigoid (OCP) have been notorious in this respect. Since the cornea derives its nutrition primarily form the aqueous humor, nutrition may be an important factor for the retention of a KPro. The purpose of this study is to compare the degree of tissue melt after implantation of two designs of the Boston KPro, one allowing much better access of nutrition to the carrier graft than the other.
The Boston KPro, made of PMMA, is shaped like a collar–button. It is implanted into a carrier corneal graft which is then sutured into the patient’s cornea. Thus the graft is sandwiched between the plastic plates. In the two designs of back plate compared here, one was solid, and therefore impermeable, whereas the other had 8 holes, 1.3 mm in diameter each. The charts with sufficient information of 157 consecutive Boston KPros performed since 1990 were reviewed with regard to tissue melt around the two types of devices as well as the ocular diagnosis.
There were 79 eyes implanted with the newer model consisting of the back plate with holes to facilitate nutrition and 78 eyes implanted with the older solid back plate. 48 eyes developed some degree of tissue melt around the stem. Of these, 40 eyes (83.3%) with melts occurred in the solid back plate group. Only 8 eyes (16.7%) with a back plate with holes melted; half of the latter suffered from an underlying autoimmune disease such as SJS or OCP.
Adding holes to the KPro back plate radically protected the overlying corneal tissue from necrosis and melt. Undoubtedly, this improved situation is due to increased aqueous access and therefore nutrition to the graft tissue. In addition, this study confirmed earlier work regarding the particular corneal fragility of patients with autoimmune diseases.
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