Secondary visual impairment induced by sinusitis is a rare condition that cannot be recognized in all cases. A steady decline in visual acuity and visual field together or alone is the main symptom patients may complain of on admission. This might be hard for general practitioners in Uzbekistan, as possible causes are either intracranial or ophthalmic abnormalities. Hence, it is frequently misdiagnosed or leads to late diagnosis once visual impairment becomes severe. In this paper, we discuss the case of a 9-year-old boy with impaired vision on the left side that was detected almost too late and could have led to complete vision loss. Ineffective conservative therapy was provided for four months. CT and MRI confirmed a lesion in the left sphenoethmoidal sinus. The patient then underwent endoscopic sphenoiethmodotomy with drainage of the left sphenoethmoidal sinus. In the early postoperative phase, as early as the next day after the surgical procedure, the patient experienced visual improvement. Forty days following surgery, in combination with postoperative conservative care in an eye hospital, there was a noticeable improvement in vision. In conclusion, it is crucial for ophthalmologists, neurologists, and ENT surgeons to focus on inflammation in the sphenoethmoidal sinus in children even with mild vision impairment.