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Clinical effect of blowing nitrogen gas across the cornea during photorefractive keratectomy
1Department of Ophthalmology, University of Rochester Medical Center, New York, USA.
Objective:
We evaluated the clinical effects of blowing nitrogen gas over the cornea during photorefractive keratectomy.
Methods:
We retrospectively compared clinical outcomes of 32 patients (37 eyes), divided into two groups who had photorefractive keratectomy with nitrogen gas blowing across the cornea (n = 19) and without nitrogen gas (n = 18). All photorefractive keratectomies were performed between April 1991 and August 1992. Ablation zone diameters were 5.0 or 5.5 mm. The average attempted correction was -3.47 +/- 1.76 diopters (D) in the nitrogen gas group, and -3.48 +/- 1.25 D in the non-nitrogen gas group.
Results:
The nitrogen gas group achieved more accurate corrections than the non-nitrogen gas group, but had a significantly greater amount of corneal haze at all postoperative examinations. Corneal haze was most evident at 1 month and gradually diminished therafter in both groups. At 6 months, videokeratography revealed a central island in 2 eyes (11.1%) of the non-nitrogen gas group. Because of undercorrection (2 eyes) or central island (1 eye), 3 out of 18 eyes in the non-nitrogen gas group were reablated 6 months later.
Conclusions:
The non-nitrogen gas group had more undercorrections and a higher frequency rate of central steep islands, but nitrogen gas blowing caused a greater amount of corneal haze.