Effect of tropicamide and phenylephrine on astigmatism axis and its implications in corneal marking
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First Author: C.Rocha de Lossada SPAIN
Co Author(s): J. Sánchez-González F. Zamorano-Martín R. Rachwani-Anil M. García-Lorente D. Flikier S. Nebro-Cobos
To analyze astigmatism power and axis changes after tropicamide and phenylephrine combined instillation.
1)Regional University Hospital of Malaga (Malaga, Spain), (2) Ophthalmology Clinic Dr. Nebro (Malaga, Spain) and (3) Ocular Surgery Institute (San José, Costa Rica).
108 eyes from fifty-four patients enrolled this prospective, cross-sectional study. Before tropicamide and phenylephrine dilation an exhaustive ocular test was achieved. Power and axis value from flat, curve and mean keratometry were extracted from auto kera-refractometer. In a second test, topography and tomography pattern were measured with the Pentacam HR® single rotation Scheimpflug camera. Subsequently, tropicamide 1% (Alcon Cusí, Barcelona, Spain) and phenylephrine hydrochloride 10% (Alcon Cusí, Barcelona, Spain) were instilled twice, with a five minutes time difference between each instillation. The quantity instilled was a drop in each eye. After thirty minutes, the AKR and Pentacam tests were repeated.
Mean flat and steep counterclockwise axis change was 3.94 ± 5.76 and 3.48 ± 7.64 degrees, respectively (P < 0.01). More than 10 degrees in 15.0% and 13.55% for flat and steep meridian. Mean flat and steep clockwise axis change was 4.38 ± 6.02 and 4.58 ± 7.53 degrees, respectively (P < 0.01). More than 10 degrees in 10.00% and 10.30% for flat and steep meridian, respectively.
Astigmatism axis significantly change after tropicamide and phenylephrine dilation. Eye marking prior to a toric intraocular lens implantation or astigmatism corneal refractive surgery should be done under the same dilatation terms in which astigmatism has been quantified