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Luís Francisco B. Chotgues, MD Dario F. G. de Azevedo, Ph.D. Thais Russomano, MD, Ph.D.

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. Aqueous Humor. Microgravity Laboratory-PUCRS.

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Luís Francisco B. Chotgues, MD Dario F. G. de Azevedo, Ph.D. Thais Russomano, MD, Ph.D.

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  1. 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.

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

  3. 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): 640-2 2nd German D-2 Spacelab-Mission 1993: 114% IOP rise Draeger J, Schwartz R, Groenhoff S, Stern C Ophthalmologe 1994 Oct; 91(5): 697-9 Microgravity Laboratory-PUCRS

  4. 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. 1993 Mar 15; 115(3):347-50 Microgravity Laboratory-PUCRS

  5. IOP during HDTObjectives • To 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 HDT • To contribute to the diagnosis and treatment of patients who suffer from glaucoma Microgravity Laboratory -PUCRS

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

  7. IOP during HDTMaterial and Methods Microgravity Laboratory-PUCRS

  8. IOP during HDTMaterial and Methods Microgravity Laboratory-PUCRS

  9. ResultsIntra-ocular Pressure(mmHg) Microgravity Laboratory-PUCRS

  10. IOP during HDT Results Microgravity Laboratory-PUCRS

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

  12. IOP during HDTConclusion • 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

  13. IOP during HDTFuture Studies • Increase in IOP in microgravity versus during HDT - Mechanism? • Measurement of venous pressure and IOP during HDT • Increase in IOP = Glaucoma Microgravity Laboratory-PUCRS

  14. Central venous pressure in spaceBuckey J. C. et al, 1996 Microgravity Laboratory-PUCRS

  15. Venous pressure in the forehead during HDT Microgravity Laboratory-PUCRS

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