The direct ophthalmoscope is a portable optical diagnostic device that enables direct visualization of the retina and the posterior segment of the eye. First developed in 1850 by Hermann von Helmholtz, it evolved throughout the 20th century with the addition of light sources, filters, and diopter adjustment mechanisms, reaching its modern form. In both human and veterinary medicine, it plays a critical role in diagnosing conditions such as glaucoma, diabetic retinopathy, hypertensive retinopathy, optic neuritis, and retinal detachment. The device consists mainly of a handle and a head. The handle contains the power source and rheostat, while the head houses the optical system, light source, diopter disc, apertures, and filters. Today, light sources are mostly LEDs, directed toward the pupil via a reflector or prism. The image produced is upright, magnified approximately 15 times, and highly contrasted, though limited by a narrow field of view (5–10°). Filter systems enhance clinical evaluation: the red-free filter increases vascular contrast; the polarizing filter reduces glare; and the cobalt blue filter, combined with fluorescein, highlights corneal defects. The diopter disc compensates for refractive errors and helps differentiate lesion depth at different ocular planes. Improper diopter or aperture selection, insufficient proximity, or inadequate light intensity may result in poor imaging. Thus, correct adjustment and regular maintenance are essential for optimal use. In conclusion, the direct ophthalmoscope remains the “first-line tool” in clinical settings due to its low cost and portability. It is widely used in both education and practice, allowing not only the detection of ocular pathologies but also the early diagnosis of systemic diseases through ophthalmoscopic findings.