Optical instrument with a continuously adjustable zoom

An optical instrument for indirectly observing an object, comprising a first lens system for producing a first image of the object, and an adjustable second lens system for producing a second image of the object, said second lens system being continuously adjustable between a first position wherein the second image has maximum magnification and/or a minimum area of view and a second position wherein the second image is of a minimum magnification and/or a maximum area of view, wherein said optical instrument defines a folded optical path which includes a generally U-shaped portion so as, in use, to reduce the separation of the observer and the observed object.

A method, comprising the steps of:

• indirectly observing an eye of a patient with the eye of an observer through an ophthalmoscope;
• producing a first image of the eye through a first lens system in said ophthalmoscope;
• and producing a second image of the eye through an adjustable second lens system in said ophthalmoscope, said second lens system being continuously adjustable between a first position wherein the second image has maximum magnification and/or a minimum area of view and a second position wherein the second image is of a minimum magnification and/or a maximum area of view, wherein said ophthalmoscope defines a folded optical path which includes a generally U-shaped portion so as, in use, to reduce the separation of the observer and the observed object.