Answer
The slit lamp, an ophthalmic device, was significantly enhanced by Allvar Gullstrand, a Swedish ophthalmologist. This apparatus combines a high-intensity light source with a biomicroscope, enabling detailed examinations of the eye's anterior segment, including the cornea, iris, lens, and anterior chamber. Gullstrand's innovations refined the slit lamp's optical system and illumination techniques, revolutionizing eye examinations and facilitating early diagnosis and treatment of various ocular conditions.