Table 2. Results of two examinations upon return to the baseline altitude (x±s, μm).

Checkpoint	Parameters	After ascent to Tibet (N=23)	The first examination (N=23)	The second examination (N=23)	Comparison of the two examinations
					t	P
Macular area	Superior nerve fiber layer	35.65±4.21	35.52±3.98	33.02±3.22	2.340	0.024
	Inferior nerve fiber layer	38.50±5.06	37.37±5.20	34.48±3.94	2.125	0.040
	Superior ganglion cell layer	71.48±5.66	71.59±6.12	70.48±7.07	0.569	0.573
	Inferior ganglion cell layer	69.41±5.92	69.85±6.20	69.63±7.09	0.111	0.912
Optic disc	Superior area	123.47±10.50	125.09±9.71	119.61±13.37	1.590	0.120
	Inferior area	113.83±11.52	117.98±11.68	124.73±12.83	−1.869	0.068
	Nasal area	80.57±9.97	79.15±8.00	72.91±8.09	2.630	0.012
	Temporal area	78.43±11.48	80.54±10.91	73.21±8.65	2.524	0.016
	Mean thickness	99.08±7.23	100.69±7.02	97.62±6.90	1.496	0.142

P<0.05 indicates significant difference.