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B. B. Markowitz, R. M. Davis; Irregularity Index as an Indicator of Risk in Hyperopic Laser Vision Correction. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2917. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The irregularity index (II) derived from corneal topography is a measure of the corneal epithelial surface and may be an indicator of risk in patients undergoing laser vision correction. In this retrospective cohort study, we examined the relationship between II, meridional asymmetry, and dry eye syndrome (DES) in patients undergoing hyperopic laser vision correction.
Retrospective chart review of 27 hyperopic eyes for pre-operative irregularity index and meridional asymmetry on the Orbscan II (Bausch and Lomb), presence of dry eyes (defined as less than 5mm on the Schirmer I test), 6-month post-operative visual acuity, and 6-month post-operative spheroequivalent, sphere, and cylinder.
Of the 27 eyes, 15 had LASEK and 12 had LASIK. The mean spheroequivalent for the 27 eyes at the 6-month postoperative visit was -0.74 + 1.41D (range -4.75 to +2.88). The mean sphere and cylinder were -1.00 + 1.38D (range -4.75 to +1.75) and +0.70 + 0.36D (range 0 to +1.75), respectively. Forty percent of eyes obtained UCVA of 20/20 at 6-months (57% of those with meridional asymmetry, 56% of those with DES) and 93% obtained UCVA of 20/40 or better (86% of those with meridional asymmetry, 88% of those with DES). The mean preoperative II was 1.3 + 0.4 (range 0.7 - 2.5) for the 27 eyes that underwent hyperopic vision correction. Seven eyes were found to have meridional asymmetry and a mean II of 1.46. This was significant compared to a mean II of 1.24 in the 20-eyes without meridional asymmetry (p = 0.046). A mean II of 1.12 was found in the 9-eyes with DES. This was decreased compared to a mean II of 1.41 in the 18-eyes without dry eyes (p = 0.041).
Hyperopic eyes with meridional asymmetry have a higher irregularity index than those without asymmetry. Hyperopic eyes without dry eye syndrome have a higher irregularity index than those with dry eyes. This may be explained by confounding due to the effect of meridional asymmetry in this relatively small sample. Despite these relationships, 93% of hyperopic eyes obtained a 6-month UCVA of 20/40 or better.
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