T. Russomano*T. Russomano*

L. F. B. Chotgues*L. F. B. Chotgues*

O. A. Lima de Sá*O. A. Lima de Sá*

M. A. dos Santos*M. A. dos Santos*

J. Ernsting**J. Ernsting**

*Microgravity Laboratory-Brazil / ** King’s College London-UK*Microgravity Laboratory-Brazil / ** King’s College London-UK

Intra-ocular and Venous Pressures Intra-ocular and Venous Pressures during Head-down Tiltduring Head-down Tilt

ObjectivesObjectives

1) To determine the relationship between IOP 1) To determine the relationship between IOP and forehead venous pressure produced by 15 and forehead venous pressure produced by 15 min exposures to:min exposures to:

0° (supine position), 17° HDT and 34° HDT0° (supine position), 17° HDT and 34° HDT

2) To compare the results obtained with HDT 2) To compare the results obtained with HDT with the ones found in microgravitywith the ones found in microgravity

3) To discuss the physiological mechanisms 3) To discuss the physiological mechanisms involved in the increase of IOP and venous involved in the increase of IOP and venous pressures with HDT and in microgravitypressures with HDT and in microgravity

Physiology of the eye on EarthPhysiology of the eye on Earth

Physiology of the eye on EarthPhysiology of the eye on Earth

Physiology of the eye on EarthPhysiology of the eye on Earth

IOP in MicrogravityIOP in Microgravity

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; 90: 640-2Ophthalmologe 1993; 90: 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; 91: 697-9Ophthalmologe 1994; 91: 697-9

IOP - Parabolic FlightIOP - 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

MethodMethod

0° (control) 17° HDT 34° HDT 0° (recovery)0° (control) 17° HDT 34° HDT 0° (recovery)

15 min15 min 15 min15 min 15 min15 min 15 min 15 min

IOP IOP IOP IOPIOP IOP IOP IOP

IOP = intra-ocular pressure VP = forehead venous pressureIOP = intra-ocular pressure VP = forehead venous pressure

VPVP VPVPVPVP VPVP

MaterialMaterial

MaterialMaterial

ResultsResults

ResultsResults

IOP and VP during HDT

13.5

25.520.7

14.7

4

19.3

13

5.2

0

10

20

30

Supine 17º HDT 34º HDT Supine

Body Position

IOP

an

d V

P

(mm

Hg

)

IOP

VP

ResultsResults

IOPIOP Venous Pressure Venous Pressure (mmHg) (mmHg) (n=8) (n=8) (mmHg) (n=4)(mmHg) (n=4)

Mean ± SEMean ± SE MeanMean

SupineSupine 14.7 ± 0.5 14.7 ± 0.5 5.2 5.2

17° HDT17° HDT 20.7 ± 0.6 20.7 ± 0.6 13.013.0

34° HDT34° HDT 25.5 ± 0.3 25.5 ± 0.3 19.319.3

Supine 13.5 ± 0.8 Supine 13.5 ± 0.8 4.0 4.0

Expected Forehead Venous PressureExpected Forehead Venous Pressure

17° HDT = approximately 13.0 17° HDT = approximately 13.0 mmHg mmHg

6.0 6.0 mmHgmmHg (Hydrostatic Pressure)(Hydrostatic Pressure)

7.0 7.0 mmHgmmHg (Venous Pressure)(Venous Pressure)

Our result: 13.0 Our result: 13.0 mmHgmmHg

34° HDT = approximately 19.0 mmHg34° HDT = approximately 19.0 mmHg

12.0 12.0 mmHg (Hydrostatic Pressure)mmHg (Hydrostatic Pressure)

7.0 7.0 mmHg (Venous Presssure)mmHg (Venous Presssure)

Our result: 19.3 Our result: 19.3 mmHgmmHg

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

ConclusionConclusion

• IOP and forehead venous pressures IOP and forehead venous pressures simultaneously increased during simultaneously increased during HDT HDT (r=0.99)(r=0.99) regardless the angle of regardless the angle of tilt employed and both returned to tilt employed and both returned to their control values in the supine their control values in the supine position.position.

Future StudiesFuture Studies

• Measurements of peripheral venous Measurements of peripheral venous pressure of the forehead in pressure of the forehead in microgravity should be made to microgravity should be made to clarify the mechanisms involved in clarify the mechanisms involved in the rise of IOP, which may differ the rise of IOP, which may differ from those found during HDTfrom those found during HDT