The eyes are the most important organ because they are directly related to a person's vision. Accordingly diseases of the eyes are of a great concern. Especially, corneal diseases, glaucoma, and retinal detachment require timely diagnosis and treatment. Recently age-related diseases tend to show an increasing trend with the increasing life expectancy in general. A significant proportion of patients with age-related macular degeneration and diabetic retinopathy end up with vision loss. Consequently, appropriate control of diabetes and regular ophthalmologic examinations are necessary. In addition, various external eye diseases caused by environmental pollution also show an increasing trend. Dry eye and conjunctivitis by bacteria, virus, various allergens, and air pollution are commonly encountered by primary health care providers. We hope this article will provide a quick and useful guide for the diagnosis and treatment of some of the most common eye diseases.