Binocular summation decreases with age and when large interocular differences are present. A pale, golden interocular line is almost always present but is sometimes indistinct. The supraoculars are narrow and undivided with 9-11 interocular scales between them. Many individuals have a dark interocular bar. The chromostereoptic effect is generally attributed to the interocular difference in TCA. There are 15-20 interocular scales and 15-20 circumorbitals. The supraoculars are narrow (occasionally enlarged and undivided) with 8-12 interocular scales between them. There are 9-14 interocular scales across the top of the head and 14-21 circumorbital scales.