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April 1985

A Study of Optical Zone Size and Incision Redeepening in Experimental Radial Keratotomy

Author Affiliations

From the Department of Ophthalmology, Estelle Doheny Eye Foundation, Los Angeles (Dr Salz and Mr Caroline); and the Departments of Preventive Medicine, University of Southern California, Los Angeles (Dr Azen and Mr Suter); and Dean McGee Eye Institute and University of Oklahoma, Oklahoma City (Dr Rowsey and Mr Monlux).

Arch Ophthalmol. 1985;103(4):590-594. doi:10.1001/archopht.1985.01050040132036

• The effects of optical clear zone size and incision redeepening following four-and eight-incision radial keratotomy were studied in a series of human cadaver eyes. Keratometry was measured with both the Terry keratometer and corneascope photographs. After eight incisions, induced corneal flattening for each clear zone (Terry keratometry readings) was 3.0 mm, 9.06 diopters; 4.0 mm, 6.44 D; 5.0 mm, 5.23 D; and 6.0 mm, 2.29 D. Differences were statistically significant, except for the 4.0-mm and 5.0-mm zones. Induced corneal flattening following eight incisions (corneoscopy) was 3.0 mm, 9.83 D; 4.0 mm, 8.87 D; 5.0 mm, 6.04 D; and 6.0 mm, 2.59 D. Differences were statistically significant, except for the 3.0-mm and 4.0-mm zones. Peripheral redeepening of the incisions did not significantly increase the amount of corneal flattening for any optical zone, as measured by the Terry keratometer. However, the 3.0-mm optical zone flattened an additional 1.23 D after the redeepening incisions, as measured by corneoscopy. The redeepening incisions were complicated by perforations in 38% of the eyes. Titrating the effect of radial keratotomy by varying the size of the optical zone appears to be valid, but the value of peripheral redeepening in the acute laboratory situation is not supported by these data.

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