Topographical corneal edema. An update

Measurement of the topographical corneal edema response has been previously restricted by the use of optical pachometry and small sample sizes. This study uses ultrasound pachometry to measure changes in the corneal thickness of 23 subjects at 9 locations during 2 hours' wear of a thick soft contact lens. The data are analysed using both averaged and individual location data. The averaged location analysis supports the current paradigm that less edema occurs in the peripheral cornea than in the central cornea during contact lens wear. However, the individual location analysis reveals a more complex corneal edema response in which the greatest amount of edema following 2 hours' contact lens wear occurred in the central and mid-peripheral temporal cornea, in comparison with the peripheral nasal and peripheral inferior cornea which showed the least edema. The edema measured in the peripheral temporal and peripheral superior cornea following 2 hours' contact lens wear was not significantly different from that measured in the central cornea. The edema measured in the central cornea following 2 hours' contact lens wear was not significantly different from that found at any mid-peripheral location. This study demonstrates that the corneal edema response associated with 2 hours' wear of a thick soft contact lens is a complex dynamic topographical process and cannot be simply modelled using averaged data from small samples.