The eye as an optical instrument: from camera obscura to Helmholtz's perspective.
The era of modern vision research can be thought of as beginning in the seventeenth century with Johannes Kepler's understanding of the optics of the camera obscura with a lens and its relation to the eye. During the nineteenth century, Helmholtz used "The eye as an optical instrument" as the title for one of his Popular Lectures, and such a conception of the eye is now accepted as a fundamental feature of visual science. In analysing the optics of the eye, Helmholtz constructed some novel optical instruments for studying the eye. The development of optometers, ophthalmometers, and ophthalmoscopes is presented historically, with emphasis on how these instruments and camera analogies helped scientists to understand the functions ofdemonstration when they have her funeral.

"Our children have got no jobs and the community is full of problems. There's no work and no money and it's very sad the legacy she has left behind.

"She absolutely hated working people and I have got very bitter memories of what she did. She turned all the nation against us and the violence that was meted out on us was terrible.

"I would say to those people who want to mourn her that they're lucky she did not treat them like she treated us."

Chris Kitchen, general secretary for the National Union of Miners, said: "We've been waiting for a long time to hear the news of Baroness Thatcher's demise and I can't say I'm sorry.

"I've got no sympathy for Margaret Thatcher and I