The paper presents a case of a 13-year-old girl admitted to the Department of Ophthalmology due to bilateral vision deterioration persisting for about one month, who 9 years earlier was diagnosed and irregularly treated for hypertension. Her best-corrected visual acuity was 0.05 for the right and 0.2 for the left eye. Grade 4 hypertensive retinopathy was diagnosed based on the appearance of the fundus of the eye and significantly increased blood pressure (220/130 mm Hg). The girl was urgently referred to the Department of Nephrology for further diagnosis and treatment. Intensive antihypertensive treatment and reduction of blood pressure led to minor improvement in visual acuity. This case report emphasises the significance of periodic blood pressure monitoring in children as well as shows how serious the ophthalmological consequences of untreated hypertension can be.