Investigating sodium hexametaphosphate as a topical treatment for calcific band keratopathy

Bennett, Naomi (2022). Investigating sodium hexametaphosphate as a topical treatment for calcific band keratopathy. University of Birmingham. Ph.D.

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Abstract

Calcific Band Keratopathy is a condition affecting the cornea, leading to the deposition of hydroxyapatite mineral in the Bowman’s membrane, sub- epithelium and anterior stroma. This condition reduces visual acuity and causes discomfort. Band keratopathy is most commonly treated with a superficial keratectomy and ethylenediaminetetraacetic acid (EDTA) chelation, however, patients may not be offered this treatment if they have other ocular co-morbidities, or the condition is not advanced. Therefore alternative, less invasive treatment options are required. In this investigation, it was found that sodium hexametaphosphate (HMP) could form the basis of an alternative topical treatment for the condition, with HMP significantly reducing the mineral present in a hydroxyapatite sol in vitro. Both cellular monolayer assays of corneal cells and tissue biopsy assays of corneal tissue provided evidence of HMP affecting cellular metabolism and reducing intra-cellular adherence. Gellan, alginate and chitosan gels each responded differently to the addition of HMP. Alginate showed a reduction in shear viscosity when assessed using rheometry, whereas both gellan and chitosan crosslinked with HMP addition and increased in viscosity. The increase in crosslink density exhibited in the gellan fluid gel and chitosan gel rendered both unsuitable for use as an eye drop. Chitosan films were developed, however, only alginate was found to release a suitable therapeutic dose of HMP. An ex vivo porcine model of band keratopathy was developed, and assessment of 0.5M HMP, 1M HMP, alginate and 0.5M HMP and 2% EDTA showed that each was successful in significantly reducing mineralisation, with 1M HMP as the most effective.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):