Table 3.

A statistically significant relationship was found between the preferred sleep posture and the side with the larger cup-to-disc ratio using a McNemar test for paired data with dichotomous outcomes

	Cup-to-disc ratio difference of at least	Side with the larger optic cup	Side preferred during sleep		Probability of agreement	Agreement (%)
			Right	Left
1)	≥0.10	Right	71	15	P=0.001	78
		Left	15	36	n=137
2)	≥0.15	Right	47	8	P=0.001	81
		Left	7	18	n=80
3)	≥0.20	Right	31	3	P=0.01	85
		Left	5	13	n=52
4)	≥0.25	Right	21	2	P=0.005	84
		Left	3	5	n=31

Notes: Data were subgrouped into those patients exhibiting a cup-to-disc ratio disparity ≥0.10, 0.15, 0.20, and 0.25. Agreement between the reported preferred side of eye dependency during sleep and the optic nerve with the larger cup-to-disc ratio was calculated for each subgroup. For patients observed to have at least a 0.10 cup-to-disc ratio asymmetry, there was a 78% agreement (71+36/total).