Treatment of band shaped keratopathy: March 2011
Ans. C: EDTA In band shaped keratopathy, improvement of vision may be obtained by dissolving it with the sodium salt of ethylenediamine tetra-acetic acid (sodium edetate) Band keratopathy It derives its name from the distinctive appearance of calcium deposition in a band across the central cornea. Band keratopathy is the result of precipitation of calcium salts on the corneal surface (directly under the epithelium). Elevated serum calcium or serum phosphate can tip the balance in or of precipitation. Topical medications that contain phosphates also may contribute to this problem. Finally, elevation of the surface pH out of the physiologic range changes the solubility product and ors precipitation. This type of tissue pH change can be seen in chronically inflamed eyes and may explain, in pa, why patients with uveitis are at risk for the development of band keratopathy Presentation Visual acuity will be decreased in propoion with the density of deposition of calcium salts in the central cornea. Slit lamp examination often reveals a whitish-grayish plaquelike deposition that occurs in a band across the cornea. The very periphery of the cornea may be spared because of the buffering effect of limbal blood vessels. Holes in the plaque may be apparent; these holes represent spaces where the corneal nerves are traversing the Bowman membrane to the epithelial surface Features of calcium deposition The calcium deposition typically begins in the periphery and progresses centrally but, occasionally, may begin centrally. The calcium may be very fine or thick and plaquelike. When it is thick, it may flake off, causing epithelial defects and painful symptoms Medical therapy It is ineffective in treating band keratopathy. However, underlying conditions associated with elevated levels of calcium or phosphate should be treated to prevent deposition from recurring (eg, patients on dialysis who subsequently undergo renal transplantation often have a more normal phosphate level). The goals of pharmacotherapy are to reduce plasma calcium levels, to prevent complications, and to reduce morbidity. Edetate calcium disodium Chelates with many divalent and trivalent metals. Because of its affinity for calcium, lowers serum calcium levels during IV infusion. Slow infusion causes mobilization of extracirculatory calcium stores. Also chelates with other polyvalent metals, therefore increasing urinary excretion of magnesium, zinc and other trace elements. Although it does not chelate with potassium, it may reduce the serum potassium level. Do not use for lead toxicity.
BAL
Chlorhexidine
EDTA
Propamidine