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Carlo Bruttini, Alice Chandra Verticchio Vercellin, Beatrice Montanaro, Massimiliano Manera, Carmine Tinelli, Annalisa De Silvestri, Giovanni Milano; The Mont Blanc Study – The effect of altitude on intraocular pressure and central corneal thickness in healthy volunteers . Invest. Ophthalmol. Vis. Sci. 2018;59(9):1662.
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To investigate the relationship between intraocular pressure (IOP), central corneal thickness (CCT), and altitude in healthy subjects.
33 healthy volunteers (mean age: 24.8 [Standard deviation: 3.3] years, 16 male) were assessed for CCT by ultrasound pachymetry (Pachmate 2, DGH technology) and for IOP by I-CARE rebound tonometer at the University Eye Clinic, Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, Pavia (PV), Italy (77 m above sea level) at 9am, 11am, 1pm and 3pm (±30’, respectively). These measurements were then repeated with the same instruments at 9 (±30’) in a closed environment at the starting station of the Mont Blanc cableway (Courmayeur station, CM, 1300 m above sea level), and upon arrival at the ending cableway station (Pointe Helbronner station, PH, 3466 m above sea level), reached within 15-20 minutes. IOP and CCT measurements were then assessed at 3466 m above sea level according to the schedule described previously (11am, 1pm and 3pm, ±30’). Multilevel (measures, eyes and patients) mixed models were fitted considering CCT and IOP as dependent variables, altitude (PV vs. CM vs. PH) and time as independent variables in the fixed part of the model; finally eyes and patients were the random factors. Post hoc comparisons between places at each time point were also performed. Statistical significance was set at p<0.05.
IOP measurements assessed at 9am by I-CARE rebound tonometer significantly decreased at CM and at PH compared to PV (p<0.001 and p=0.013, respectively). In details, compared to PV, IOP was significantly lower at PH at 11am and 15 pm (13.7 mmHg+/-3.67 vs 14.3 mmHg+/-3.69, p<0.001, and 12.9 mmHg+/-3.07 vs 14.0+/-3.66 mmHg, p=0.005, respectively). CCT measured at 9 am±30’ significantly increased at PH compared to CM (562 um+/-34.25 vs 558 um+/-32.60, p=0.002), and at PH compared to PV (562 um+/-34.25 vs 559 um+/-33.54, p=0.006).
Upon ascension from the sea level to medium altitudes, IOP significantly decreased and CCT significantly increased. Altitude may be considered a protective factor for glaucomatous patients. Further studies are needed in order to investigate the influence of altitude in a glaucomatous population and the effect of acclimatization on IOP and CCT.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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