WHICH ANGLE OF HEAD-DOWN TILT WHICH ANGLE OF HEAD-DOWN TILT BETTER SIMULATES THE INCREASE IN BETTER SIMULATES THE INCREASE IN

INTRA-OCULAR PRESSURE THAT OCCURS INTRA-OCULAR PRESSURE THAT OCCURS IN MICROGRAVITY?IN MICROGRAVITY?

Luís Francisco B. Chotgues, MDLuís Francisco B. Chotgues, MD

Dario F. G. de Azevedo, Ph.D.Dario F. G. de Azevedo, Ph.D.

Thais Russomano, MD, Ph.D.Thais Russomano, MD, Ph.D.

Physiology of the eye on EarthPhysiology of the eye on Earth

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

• Aqueous Humor

Intra-ocular pressure (IOP) Intra-ocular pressure (IOP) in microgravityin microgravity

AUTOMATIC SELF-TONOMETRYAUTOMATIC SELF-TONOMETRY

1st German-Russian MIR mission 1992 : 92% IOP rise1st German-Russian MIR mission 1992 : 92% IOP rise

Schwartz R, Draeger J, Groenhoff S, Flade K DSchwartz R, Draeger J, Groenhoff S, Flade K D

Ophthalmologe 1993 Dec; 90(6): 640-2Ophthalmologe 1993 Dec; 90(6): 640-2

2nd German D-2 Spacelab-Mission 1993: 114% IOP rise2nd German D-2 Spacelab-Mission 1993: 114% IOP rise

Draeger J, Schwartz R, Groenhoff S, Stern CDraeger J, Schwartz R, Groenhoff S, Stern C

Ophthalmologe 1994 Oct; 91(5): 697-9Ophthalmologe 1994 Oct; 91(5): 697-9

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during parabolic flightIOP during parabolic flight

IOP increased 58% (19 mmHg) during parabolic flight (20 IOP increased 58% (19 mmHg) during parabolic flight (20 s of µG) compared to baseline values (12 mmHg) (s of µG) compared to baseline values (12 mmHg) (n =11)n =11)

Mader TH et alMader TH et al., Am J Ophtalmol. 1993 Mar 15; 115(3):347-50., Am J Ophtalmol. 1993 Mar 15; 115(3):347-50

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDTIOP during HDTObjectivesObjectives

• To determine the angle of head-down tilt that To determine the angle of head-down tilt that best simulates the increase in IOP after 15 min best simulates the increase in IOP after 15 min insertion in microgravityinsertion in microgravity

• To evaluate the mechanisms involved in the To evaluate the mechanisms involved in the increase in the IOP during microgravity and increase in the IOP during microgravity and HDTHDT

• To contribute to the diagnosis and treatment of To contribute to the diagnosis and treatment of patients who suffer from glaucomapatients who suffer from glaucoma

Microgravity Laboratory -PUCRSMicrogravity Laboratory -PUCRS

IOP during HDTIOP during HDTProtocolProtocol

• 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)Sitting position (after 5 min - baseline)

– 4 randomized angles of HDT (after 15 min):4 randomized angles of HDT (after 15 min):

• 6, 12, 18 and 34 degrees6, 12, 18 and 34 degrees

– Time of day: 8 - 12 AMTime of day: 8 - 12 AM

– Test duration per subject: 2 hTest duration per subject: 2 h

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDTIOP during HDTMaterial and MethodsMaterial and Methods

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDTIOP during HDTMaterial and MethodsMaterial and Methods

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

ResultsResultsIntra-ocular PressureIntra-ocular Pressure

(mmHg)(mmHg)

Body position Mean +/- SE p < or = 0.05

Sitting 12.6 +/- 0.5

6 HDT 17.0 +/- 0.7 S

12 HDT 18.9 +/- 0.7 S

18 HDT 19.6 +/- 0.7 S

34 HDT 27.0 +/- 1.5 S

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDT IOP during HDT ResultsResults

31

5563

110

0

20

40

60

80

100

120

6° HDT 12° HDT 18° HDT 34° HDT

Body Position

% C

han

ge

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDT and MicrogravityIOP during HDT and Microgravity

31

5563

110 114

92

0

20

40

60

80

100

120

6° HDT 12° HDT 18° HDT 34° HDT D2mission*

Ger-RussMir**

Body Position

% C

han

ge

* Draeger J et al., 1993 ** Schwartz R et al., 1992Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDTIOP during HDTConclusionConclusion

• 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-PUCRSMicrogravity Laboratory-PUCRS

IOP during HDTIOP during HDTFuture StudiesFuture Studies

• Increase in IOP in microgravity versus during Increase in IOP in microgravity versus during HDT - Mechanism?HDT - Mechanism?

• Measurement of venous pressure and IOP Measurement of venous pressure and IOP during HDTduring HDT

• Increase in IOP = GlaucomaIncrease in IOP = Glaucoma

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

Central venous pressure in spaceCentral venous pressure in space Buckey J. C. et al, 1996Buckey J. C. et al, 1996

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS

Venous pressure in the Venous pressure in the forehead during HDTforehead during HDT

Microgravity Laboratory-PUCRSMicrogravity Laboratory-PUCRS