These fossils are interpreted as most probably being early sponges.Trace fossils such as tracks and burrows found in the Tonian period (from 1 gya) may indicate the presence of triploblastic worm-like animals, roughly as large (about 5 mm wide) and complex as earthworms. However, similar tracks are produced today by the giant single-celled protist Gromia sphaerica, so the Tonian trace fossils may not indicate early animal evolution. Around the same time, the layered mats of microorganisms called stromatolites decreased in diversity, perhaps due to grazing by newly evolved animals. Objects such as sediment-filled tubes that resemble trace fossils of the burrows of wormlike animals have been found in 1.2 gya rocks in North America, in 1.5 gya rocks in Australia and North America, and in 1.7 gya rocks in Australia. Their interpretation as having an animal origin is disputed, as they might be water-escape or other structures. Phylogeny
Animals are monophyletic, meaning they are derived from a common ancestor. Animals are sister to the Choanoflagellata, with which they form the Choanozoa. The most basal animals, the Porifera, Ctenophora, Cnidaria, and Placozoa, have body plans that lack bilateral symmetry. Their relationships are still disputed; the sister group to all other animals could be the Porifera or the Ctenophora, both of which lack hox genes, important in body plan development.These genes are found in the Placozoa and the higher animals, the Bilateria.
The authors conclude that current evidence does not show a benefit of either intravenous or oral corticosteroids for rate of recovery of vision (in terms of visual acuity, contrast sensitivity, or visual fields). There are a number of reasons why this might be the case. Epidemiology
Optic neuritis typically affects young adults ranging from 18–45 years of age, with a mean age of 30–35 years. There is a strong female predominance. The annual incidence is approximately 5/100,000, with a prevalence estimated to be 115/100,000. Society and culture
In Charles Dickens Bleak House, the main character, Esther Summerville, has a transient episode of visual loss, the symptoms of which  are also seen in people who have optic neuritis. Legal historian Sir William Searle Holdsworth, suggested that the events in Bleak House took place in 1827. In an episode of Dr. Quinn, Medicine Woman ("Season of Miracles", season five), Reverend Timothy Johnson is struck blind by optic neuritis on Christmas Day 1872. He remains blind for the duration of the series. See also
Optic neuropathy
Visual snow

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