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F. Hafezi; The Impact of Tobacco Smoking on Corneal Biomechanics and Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4626.
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To investigate whether chronic tobacco smoking induces changes in the biomechanical properties of the human cornea and the accuracy of intraocular pressure measurements.
We investigated potential changes in the biomechanical properties of the cornea in chronic smokers and non-smokers using the Ocular Response Analyzer (ORA), a device that utilizes a dynamic bi-directional applanation process to measure biomechanical parameters. We conducted a prospective comparative case series study including 122 eyes (60 eyes from non-smokers and 62 age-matched eyes from chronic smokers). The study was approved by the institutional review board of the canton of Zurich and adheres to the tenets of the Declaration of Helsinki. Patient age ranged from 20 to 69 years (Non-smokers: mean age 43.4 years, median age 45.5 years. Smokers: mean age 44.1 years, median age 42.6 years). Inclusion criteria for smokers were current smoking and a smoking history of at least 10 pack years.
The main parameters for corneal rigidity, as measured by the ORA, are the Corneal Resistance factor (CRF) and Corneal Hysteresis (CH). In smokers, we observed statistically significant increases of CRF (P<0.0001, Student’s t-test) and CH (P=0.02, Student’s t-test). Concerning measurement of intraocular pressure (IOP), we observed statistically significant increases of the Goldmann-correlated IOP (IOPG) (p = 0.02), but no significant changes in the cornea-compensated IOP (IOPcc) (p = 0.18) in smokers. Data analysis was performed using Student’s t-test.
Regarding corneal biomechanics, our results suggest that chronic smoking has a beneficial effect on corneal biomechanics. Obviously, we can not recommend tobacco smoking in patients suffering from keratoconus due to the associated health risks. However, the relationship between chronic smoking and corneal biomechanics observed here may help the clinician to better assess the speed by which keratoconus will probably progress. Regarding IOP measurements, a raise in Goldmann IOP in smokers might represent a measurement artifact due to the increased rigidity of the cornea. In the light of an estimated 1.2 billion smokers worldwide in 2010, nomograms need to be established for accurate glaucoma monitoring in chronic smokers.
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