When eyes appear to turn black, it’s usually due to the surrounding area darkening or the pupil significantly enlarging. This visual effect isn’t a literal change in iris color but stems from various factors. These factors can range from common injuries and physiological responses to more serious internal eye conditions. Understanding these causes helps determine when medical attention is needed.
External Causes: Bruising and Injury
A common reason for the eye area to appear black is trauma or injury to the face, known as a “black eye” or periorbital hematoma. This occurs when blood vessels beneath the skin around the eye break, leading to blood pooling and dark discoloration, often with swelling. It may initially appear reddish, then darken to purple, blue, or black.
As the body reabsorbs the blood, the bruise changes colors, typically to green, yellow, and brown before fading. Common causes include falls, sports injuries, or direct blows. While usually temporary, the underlying trauma can cause more serious injuries to the eye or facial bones. It typically heals within one to three weeks.
Physiological Changes: Pupil Dilation
The pupil, the black circle in the center of the iris, appears black because it’s an opening allowing light into the eye. Light entering is mostly absorbed by internal tissues, creating its dark appearance. When the pupil widens (dilation), this dark area becomes more prominent, making the eye appear darker or even entirely black.
This is a natural response, with iris muscles controlling pupil size to regulate light. In dim lighting, pupils dilate to allow more light to reach the retina, enhancing vision. Emotions like excitement, fear, or attraction can also trigger dilation. Additionally, medications, including some antidepressants, antihistamines, decongestants, and certain recreational drugs, can cause pupils to dilate.
Internal Eye Conditions
Less common but more serious internal eye conditions can also lead to the eye appearing black. Hyphema involves blood collecting in the anterior chamber of the eye (between the cornea and iris). This blood can partially or completely cover the iris and pupil, making the eye appear dark or black and obscuring vision. Hyphema is frequently caused by eye trauma, such as a direct blow, but can also occur spontaneously due to abnormal blood vessels, certain infections, or blood clotting disorders.
Another condition is aniridia, a rare genetic disorder characterized by the complete or partial absence of the iris from birth. With a missing or underdeveloped iris, the pupil appears unusually large, making the entire eye look black. Individuals often experience increased light sensitivity because the iris cannot regulate light entry. This condition can also be associated with other eye issues, including cataracts and glaucoma, which may further affect vision.
When to Seek Medical Attention
While many instances of an eye appearing black are benign, certain signs warrant prompt medical evaluation. If a black eye results from trauma, see a healthcare provider to rule out serious injuries beyond bruising. Seek immediate medical attention for any vision change, such as blurriness, double vision, or vision loss.
Persistent or severe eye pain, headaches that do not subside, or bleeding from the eye, nose, or ears also indicate a need for urgent care. Other concerning symptoms include inability to move the eye, a noticeable change in pupil size or shape, or if one pupil is significantly larger than the other.
Swelling that worsens rather than improves, the presence of pus or discharge, or any signs of infection around the eye should also prompt a medical visit. If a black eye appears without a known cause, or if discoloration doesn’t improve within a few weeks, consult a healthcare professional to investigate potential underlying conditions.