173.
INTRAOCULAR PRESSURE AND MACULA FUNCTION CHANGES DURING HIGH-
ALTITUDE ACCLIMATIZATION. Mitrofanis Pavlidis
1
, Tobias Stupp
1
, Ilias Georgalas
2
, Evi
Georgiadou
2
, Michael Moschos
2
, Solon Thanos
1
. University of Münster Germany
1
, University of
Athens Greece
2
.
Objective: To evaluate the relationship between hypobaric hypoxia, acclimatization
intraocular pressure (IOP) and the effects of high altitude hypobaric hypoxia to macula
morphology and function during ascent, acclimatization and descent between 2286 m and 5650
m. Methods: The following acclimatization-indicative physiological parameters were compared
daily with IOP changes in eight healthy climbers of a Karakorum Himalaya expedition (2003):
Hemoglobin oxygen saturation (PO2), resting heart rate, blood pressure, retinal findings, and the
Lake Louise score of acclimatization. Macula function was evaluated in three of the climbers
with multifocal electroretinogramms (MF ERG), near vision acuity and amsler grid tests. Macula
morphology was tested with the optical coherence topography (OCT) and with stereoscopic
fundopscopy obtained one week before ascent, as well as one week and two weeks after high
altitude exposure. Results: IOP decreased significantly in the ascent phase and recovered
following acclimatization. A direct proportional correlation between decreases in PO2 and IOP
was evaluated. No retinal hemorrhages were observed in well- and incompletely acclimatized
climbers. The central macula MF ERG responses reduced significantly one week after high
altitude exposure and recovered in the next week follow up examination. Near vision acuity and
amsler grid tests remained unaffected in both follow up examinations. Few but not significant
changes could be found in the follow up OCT and daily fundoscopy examinations by all three
well acclimatised climbers. Conclusions: IOP changes could be related to hypoxia-induced
respiratory alkalosis and acclimatization stage, which could be used as a simple mobile screening
test for acclimatization level to reveal acute mountain sickness and its severe consequences. By
high altitude tourists, travellers and athletes with macula diseases like age related macula
degeneration, tapetoretinal degeneration or diabetic retinopathy high altitude exposure could
accelerate the disease progression.
174.
EFFECT OF FROSTBITE UNDER HYPOXIA ON MICROCIRCULATORY PERFUSION IN
RATS . Yan Pei-Hua
1
, Yang Zeng-Ren
1
, Liu Jia-Ying
1
, Li Feng-Zhi
1
. Institute of Hygiene and
Environmental Medicine,Academy of Military Medical Sciences, Tianjin
1
.
Changes of microcirculatory perfusion in rats following cold injury of right hind 1eg under
hypoxia were investigated_ Male Wistar rats weighing 200±20 g were random1y divided into
three groups_ frostbite at normoxia (FN) group; frostbite during acute hypoxia (4 h at 6 km
simulated altitude, FAH) group and frostbite during hypoxia after acclimation (exposure to
hypoxia at 6 km, 4h daily for 4 weeks, FHAC) group. A low temperature bath was used as a
freezing device, 95% alcohol as a freezing mixture. Right hind 1eg of rats were immersed in the
mixture at -25_ up to 2 cm above ankle joint. When the tissue temperature cooled down to -15_,
they were frozen another 2 min, then rewarmed immediately in a water bath at 20_ until the tissue
temperature reached 20_. At pre-freezing and at 1, 3, 5 d post-freezing, microcirculatory
perfusion was measured at the outside of both hind 1egs 1 cm above ankle joint by Laser Doppler
Flowmeter (LDF). Before freezing, microcirculatory perfusions of left and right hind 1egs of FN
group were 243.87±9.91_mV, ±s
x
, the same in the following) and 257.60±10.31 respectively;
In FAH group they were 169.00±7.41 and 164.93±5.95 respectively; in FHAC group they were
90.87±6.90 and 91.53±5.55 respectively. At 1, 3, and 5 days after freezing, the microcirculatory
perfusions of left hind leg of FN group were 132.46±9.76, 189.38±10.23, 139.69±7.91
respectively, in right hind leg they were 51.31±10.09, 166.46±12.40, 81.21±17.40 respectively; in
left hind leg of FAH group they were 176.64±8.32, 106.46±7.34, 86.92±7.34 respectively, in
right hind leg they were 109.93±10.30, 102.77±7.44, 2.00±2.00 respectively; in left hind leg of
FHAC group they were 152.93±6.66, 143.00±6.07, 130.21±8.17 respectively, in right hind leg
they were 26.47±8.17, 0.00±0.00, 26.21±12.17 respectively. The results showed that the
microcirculatory perfusions of both hind legs of FAH group were marked1y lower than those of
