44 Trans. Amer. Oph. Soc., 1879, p. 548.
When carefully examining eyes with the ophthalmoscope, it is not a very unusual circumstance to see a small grayish tag arising from the lymph-sheath of the central retinal vessels and extending a short distance forward into the vitreous. These tags usually present slow, sinuous movements, following motions of the eyeball. It is, however, rare to have such obliterated vessels extend through the vitreous and show their previous distribution in the posterior capsule of the lens, as in the instances reported by Zehender,45 Liebreich,46 and Becker;47 in Zehender's case the artery was patulous and blood-bearing. Little48 has also depicted a case where the hyaloid artery was filled with blood. The central canal of the vitreous, which is occupied in the foetal eye by the artery in question, is readily demonstrated in pigs' eyes by allowing colored fluid to flow into it from its central end. According to H. Müller,49 atrophied remnants of the artery are always present in the eyes of oxen. Manz50 gives an anatomical description and plate of a continuance of the lymph-sheath of the central artery through the vitreous forward to the capsule of the lens, the remnants of the artery being found only in its proximal portion: observation had been impossible during life on account of corneal opacities. The same writer describes a convolution of vessels as penetrating the posterior part of the vitreous from the retina in the eyes of some Australian reptiles (Trachyeaurus and Lygosoma), and regards it as a similar formation to the pecten of the bird's eye. According to Ammon, some forms of congenital cataract are connected with the too early obliteration of the hyaloid artery, which is so important in furnishing nutriment to the growing lens.
45 Klin. Monatsblät. f. Augenheilkunde, 1863, pp. 260-349.
46 Ibid., p. 350.
47 Annales d'Oculistique, 1865, p. 350.
48 Trans. Amer. Ophth. Soc., 1881, pp. 211-213.
49 Gessamm. Schriften, p. 365.
50 Graefe und Saemisch, vol. ii. pp. 97-99.
Von Graefe remarks, however, that this very unusual yet incomplete development of the retinal vessels is common in congenital amaurosis. He reports51 an instance in a blind eye of a boy ten years of age, who also exhibited a convergent squint and nystagmus. Mooren52 also gives a case of entire absence of the retinal blood-vessels in a child seven months old. Pathological conditions of the blood often give rise to visible changes in the eye-ground.
51 Arch. f. Ophth., vol. i., part 1, pp. 403, 404.