Australia antigen
The next insight regarding hepatitis B was a serendipitous one by Dr. Baruch Blumberg, a researcher at the NIH who did not set out to research hepatitis, but rather studied lipoprotein genetics. He travelled across the globe collecting blood samples, investigating the interplay between disease, environment, and genetics with the goal of designing  targeted interventions for at-risk people that could prevent them from getting sick. He noticed an unexpected interaction between the blood of a patient with hemophilia that had received multiple transfusions and a protein found in the blood of an indigenous Australian person. He named the protein the "Australia antigen" and made it the focus of his research. He found a higher prevalence of the protein in the blood of patients from developing countries, compared to those from developed ones, and noted associations of the antigen with other diseases like leukemia and Down Syndrome. Eventually, he came to the unifying conclusion that the Australia antigen was associated with viral hepatitis. In 1970, David Dane first isolated the hepatitis B virion at Londons Middlesex Hospital, and named the virion the 42-nm "Dane particle". Based on its association with the surface of the hepatitis B virus, the Australia antigen was renamed to "hepatitis B surface antigen" or HBsAg. Blumberg continued to study the antigen, and eventually developed the first hepatitis B vaccine using plasma rich in HBsAg, for which he received the Nobel Prize in Medicine in 1976.
Ophthalmoparesis  refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease. Internal ophthalmoplegia means involvement limited to the pupillary sphincter and ciliary muscle. External ophthalmoplegia refers to involvement of only the extraocular muscles. Complete ophthalmoplegia indicates involvement of both. Causes
Ophthalmoparesis can result from disorders of various parts of the eye and nervous system:

Infection around the eye. Ophthalmoplegia is an important finding in orbital cellulitis. The orbit of the eye, including mechanical restrictions of eye movement, as in Graves disease. The muscle, as in progressive external ophthalmoplegia or Kearns–Sayre syndrome. The neuromuscular junction, as in myasthenia gravis. The relevant cranial nerves (specifically the oculomotor, trochlear, and abducens), as in cavernous sinus syndrome or raised intracranial pressure. The brainstem nuclei of these nerves, as in certain patterns of brainstem stroke such as Fovilles syndrome. White matter tracts connecting these nuclei, as in internuclear ophthalmoplegia, an occasional finding in multiple sclerosis. Dorsal midbrain structures, as in Parinauds syndrome. Certain parts of the cerebral cortex (including the frontal eye fields), as in stroke. Toxic envenomation by mambas, taipans, and kraits.Thiamine deficiency can cause ophthalmoparesis in susceptible persons; this is part of the syndrome called Wernicke encephalopathy. The causal pathway by which this occurs is unknown. Intoxication with certain substances, such as phenytoin, can also cause ophthalmoparesis.