Snake Eyes

Over the last few months, Animal Care staff noticed something a little funny about one of our boa constrictors. Esteban’s eye appeared cloudy, as though a thin white film were covering part of his eye and pupil. While snakes normally experience a brief period before shedding when their eyes cloud over and are nearly opaque, the rest of the time they are usually bright, shiny and clear.


When we brought him to The Center for Bird and Exotic Animal Medicine (BEAM), Dr. Maas used a bright, narrow beam light to pinpoint the source of the clouding. To our relief, it was not deep in the eye like a cataract, but right on the surface of the eye.


To understand what we did next, it is necessary to understand a bit of snake eye anatomy. Snakes are well known for their unblinking stare, and in fact snakes are unable to blink. Their eyelids are greatly modified, into a fused, clear covering over the eye, called a spectacle or eye cap.

This cap is strong enough that snakes can strike their prey, swim, slide through underbrush, and in some species use their heads for digging, all without blinking and without damage to their eyes. The spectacle itself may be scuffed up in the course of daily activities, but luckily it is shed when the snake sheds its skin, so it is always being replaced by a newer, clear covering.


Snakes’ eyes are mobile, and to allow this, there is a layer of liquid, like our tears, between the eye itself and the spectacle. Our concern was that if the eye were infected, bacteria would grow in that liquid layer, and be the source of the clouding.

To see what was going on with Esteban’s eye, Dr. Maas carefully inserted a very small needle between the spectacle and the eye, and removed a small amount of this liquid for testing. What he found was reassuring.


Esteban has no sign of infection in his eye tissue. Most likely, he produced excess protein due to a minor injury, or slight inflammation, and the cloudiness will take care of itself in the next few sheds. If not, we will need to inject minute amounts of anti-inflammatories into the space around Esteban’s eye – not a task for the faint of heart.