WHICH ANGLE OF HEAD-DOWN TILT BETTER SIMULATES THE INCREASE IN INTRA-OCULAR PRESSURE THAT OCCURS IN MICROGRAVITY? Luís Francisco B. Chotgues, MD Dario F. G. de Azevedo, Ph.D. Thais Russomano, MD, Ph.D.

Physiology of the eye on Earth Microgravity Laboratory-PUCRS Aqueous Humor

Intra-ocular pressure (IOP) in microgravity AUTOMATIC SELF-TONOMETRY 1st German-Russian MIR mission 1992 : 92% IOP rise Schwartz R, Draeger J, Groenhoff S, Flade K D Ophthalmologe 1993 Dec; 90(6): nd German D-2 Spacelab-Mission 1993: 114% IOP rise Draeger J, Schwartz R, Groenhoff S, Stern C Ophthalmologe 1994 Oct; 91(5): Microgravity Laboratory-PUCRS

IOP during parabolic flight IOP increased 58% (19 mmHg) during parabolic flight (20 s of µG) compared to baseline values (12 mmHg) ( n =11) Mader TH et al., Am J Ophtalmol Mar 15; 115(3): Microgravity Laboratory-PUCRS

IOP during HDT Objectives To determine the angle of head-down tilt that best simulates the increase in IOP after 15 min insertion in microgravityTo determine the angle of head-down tilt that best simulates the increase in IOP after 15 min insertion in microgravity To evaluate the mechanisms involved in the increase in the IOP during microgravity and HDTTo evaluate the mechanisms involved in the increase in the IOP during microgravity and HDT To contribute to the diagnosis and treatment of patients who suffer from glaucomaTo contribute to the diagnosis and treatment of patients who suffer from glaucoma Microgravity Laboratory -PUCRS

IOP during HDT Protocol Number of subjects: 8 (16 eyes)Number of subjects: 8 (16 eyes) Portable aplanation tonometerPortable aplanation tonometer IOP measurements:IOP measurements: –Sitting position (after 5 min - baseline) –4 randomized angles of HDT (after 15 min): 6, 12, 18 and 34 degrees 6, 12, 18 and 34 degrees –Time of day: AM –Test duration per subject: 2 h Microgravity Laboratory-PUCRS

IOP during HDT Material and Methods Microgravity Laboratory-PUCRS

IOP during HDT Material and Methods Microgravity Laboratory-PUCRS

Results Intra-ocular Pressure (mmHg) Microgravity Laboratory-PUCRS

IOP during HDT Results Microgravity Laboratory-PUCRS

IOP during HDT and Microgravity * Draeger J et al., 1993 ** Schwartz R et al., 1992 Microgravity Laboratory-PUCRS

IOP during HDT Conclusion IOP enhanced 110% after 15 min of 34° of HDT 34° of HDT was accepted as the angle that best simulates the acute increase in IOP that occurs in microgravity 6° of HDT did not produce the rise in IOP that has been found during space missions Microgravity Laboratory-PUCRS

IOP during HDT Future Studies Increase in IOP in microgravity versus during HDT - Mechanism?Increase in IOP in microgravity versus during HDT - Mechanism? Measurement of venous pressure and IOP during HDTMeasurement of venous pressure and IOP during HDT Increase in IOP = GlaucomaIncrease in IOP = Glaucoma Microgravity Laboratory-PUCRS

Central venous pressure in space Buckey J. C. et al, 1996 Microgravity Laboratory-PUCRS

Venous pressure in the forehead during HDT Microgravity Laboratory-PUCRS