Crested geckos are a popular pet reptile known for their unique eyelids and eyelashes. But do they actually have eyelids like humans and other animals? The short answer is yes, crested geckos do have eyelids, but they are very different from mammalian eyelids.
In this comprehensive article, we’ll take an in-depth look at the anatomy of crested gecko eyes, examining their eyelids, eye structure, and how their eyes work. We’ll compare gecko eyelids to human eyelids and other reptiles.
Read on to learn all about the eyes and eyelids of these fascinating lizards.
Anatomy of Crested Gecko Eyes and Eyelids
Upper and Lower Eyelids
Crested geckos have both upper and lower eyelids like humans do. The upper lid protects the eye from above, while the lower lid shields the eye below. When open, the gecko’s large, bulging eyes give it excellent vision. When closed, the eyelids offer protection and keep the eyes moist.
Transparent Eyelid Called the Nictitating Membrane
In addition to the upper and lower lids, crested geckos have a third eyelid known as a nictitating membrane. This translucent eyelid sits inside the eye socket and moves horizontally across the eye. It keeps the eye lubricated and protected while allowing some vision.
Lack of Connective Tissue Between Upper and Lower Lids
Unlike human eyelids that are connected at the outer corners, a crested gecko’s upper and lower lids are not joined together. This gives them the ability to independently blink the upper or lower lid as needed.
| Human Eyelids | Crested Gecko Eyelids |
|---|---|
| Upper and lower lids connected at corners | Upper and lower lids completely separate |
Gecko Eyelids Protect Eyes and Lubricate Cornea
When closed, a gecko’s eyelids prevent debris, dirt and sunlight from reaching the sensitive eyeball. The inner surface of the eyelid contains lubricating fluids that coat the cornea each time the gecko blinks. Without lubrication, reptiles’ eyes would quickly dry out.
Eyelashes and Scales on Eyelids
Crested geckos lack eyelashes, but their eyelids are covered in shiny scales. These scales protect the lid edges. Geckos are also unable to produce tears. To keep the eyes moist, they depend on the lubrication from the nictitating membrane.
Immobile Eyes in Eye Sockets
Unlike humans who can move their eyes around, crested geckos have eyes that are immobile in their sockets. To scan their environment, they have to turn their heads. However, gecko eyes can focus quickly on prey. Their visual acuity is estimated to be about 5 times better than human eyesight!
How Gecko Eyes and Eyelids Differ from Humans and Mammals
Gecko Eyelids Don’t Blink
Unlike humans who blink frequently, geckos don’t have eyelids that close to moisten and protect their eyes. Their eyelids are essentially transparent scales called spectacles that protect their eyes but don’t move or blink.
Eyelids Stay Open Most of the Time
Geckos only close their eyelids when sleeping or shedding skin. Their eyelids remain open during awake hours to constantly survey their surroundings for prey and predators.
Humans Blink Frequently to Lubricate Eyes
Humans blink every 2 to 10 seconds to spread tears across the eyeball, keeping it moist and vision clear. Blinking also momentarily blocks light from entering the eye. Without frequent blinking, human eyes would quickly dry out and become damaged.
Geckos Lick Eyes to Lubricate
Since geckos don’t blink, they lick their eyes with their tongues to keep them moist. They have a special translucent scale called a spectacle that protects the eye between licks.
Mammal Eyelids Connected by Tissue, Gecko Lids are Not
In mammals like humans, the upper and lower eyelids are connected by a thin tissue called the palpebral conjunctiva. Gecko eyelids are not connected, allowing them to lick each lid separately.
Gecko Eyes Don’t Move, Mammal Eyes Do
Mammals like humans have eye muscles that control eye movement and blinking. Gecko eyes are fixed in place and can’t move around in their sockets. They move their head instead of their eyes to change their gaze.
Gecko Eyes Protected in Sockets, Mammal Eyes are Exposed
The mammalian eyeball sits in a shallow orbital socket, leaving it partially exposed. The gecko eye sits deeper in the skull, offering more protection. Their fixed eyelids provide an extra defense layer.
Crested Gecko Eyelid Function and Behavior
Cleaning Eyes and Lens with Eyelids
Crested geckos lack movable eyelids, but they do have small flap-like eyelids that help protect their eyes. When a crested gecko blinks, the eyelids help lubricate and clean the surface of the eye. Blinking spreads tears across the cornea and washes away dust and debris (1).
The eyelids also contain modified eyelashes that help remove particles from the eye.
Moistening Eyes by Licking
Since crested geckos don’t produce enough tears to keep their eyes moist, they also lick their eyes frequently. Their broad tongues are perfect for spreading saliva across the eyeball to lubricate it (2). You may notice your crested gecko licking its eye area several times a day.
This helps supplement the moisture provided by blinking.
Using Nictitating Membrane for Protection
In addition to small eyelids, crested geckos have a protective nictitating membrane. This clear third eyelid helps keep the eye moist and provides extra protection (3). When a crested gecko blinks, the nictitating membrane sweeps horizontally across the eye, catching debris and wiping the surface clean.
Shedding Eyelid Skin and Eyelashes
Like the rest of their body, crested geckos shed their eyelid skin and eyelashes periodically. The old skin peels off in patches, revealing new clean skin underneath. Shedding helps remove bacteria and parasites from the eyelids (4).
Be sure to provide a humid hide box to help your crested gecko shed its eye caps cleanly.
Basking or Sleeping with Eyes Closed
Crested geckos sometimes close their eyes fully while basking under heat lamps or sleeping. With eyes closed and nictitating membranes drawn over their eyes, crested geckos can achieve total darkness for resting (5). However, they never close their eyes tightly for long periods of time.
Sleeping with eyes wide open is also common for safety’s sake.
Interesting Facts About Crested Gecko Eyes
Excellent Night Vision Ability
Crested geckos have superb nocturnal vision allowing them to see well in low light conditions. Their large eyes with a reflective layer behind the retina called the tapetum lucidum enhances their ability to see at night.
The tapetum acts like a mirror to reflect light back through the retina, providing a “second chance” for light detection. This allows crested geckos to see up to 350 times better than humans in low light!
Mostly Colorblind, Seeing Limited Color
Although crested geckos have excellent night vision, they have limited color vision. Their eyes contain only cone photoreceptor cells, making them potentially tetrachromatic and able to detect some colors.
However, crested gecko retinas lack red-sensitive pigment, so they likely see a limited range of colors, mostly in the blue-green-violet wavelength ranges. So vibrant reptile habitat decor may appear dull through crested gecko eyes.
Eyes Allow Binocular Vision
With large, forward-facing eyes, crested geckos have binocular vision, meaning their field of vision overlaps between both eyes. This gives them depth perception to accurately judge distances when hunting prey and climbing in trees.
Their visual field spans nearly 360 degrees around their head, giving superb detection of predators.
Unblinking Stare to Mesmerize Prey
Crested geckos lack eyelids and are unable to blink! To keep their eyes moist, they have a transparent scale called a brille that protects their eyes. This also allows them to fixedly stare at prey without blinking to help mesmerize and hunt insects.
The unblinking gaze with their vertical slit pupils gives them an intense reptilian look!
Ability to See UV Light
Research suggests crested geckos may see in the ultraviolet (UV) spectrum, beyond visible human light detection. Many of their prey, like insects and spiders, display UV markings, so seeing UV wavelengths likely aids gecko hunting and mating success.
UV light also aids calcium absorption for healthy bones. Special UVB lighting is recommended for captive crested geckos.
Vertical Pupils
Crested geckos have vertical slit-shaped pupils, optimizing light control in bright and dim conditions. The shape constricts in bright light to limit excess light entry. In darkness, the vertical slit dilates fully to allow maximal light capture.
Other benefits are precise focusing on prey and gauging distances for accurate leaping and landing abilities while climbing trees and rocks.
Conclusion
While crested gecko eyes share some similarities with human and mammalian eyes, their eyelids and eye anatomy are quite unique. Geckos have movable upper and lower lids, a see-through third eyelid, eyelashes, and immobile eyes.
Their eyelids stay open most of the time and geckos clean and moisten their eyes by licking. The gecko stare with their eyelids open helps them hunt insects.
Understanding the special eyelids and eye structures of crested geckos gives insight into how these reptiles function and perceive the world around them. Their specialized eyes and eyelids allow crested geckos to thrive in their environments as expert nocturnal hunters.
