Turtles evolved to survive a semi-aquatic lifestyle requiring them to have good eyesight to navigate and track food whether on land or water. Land-dwelling turtle varieties like Galapagos have downward-facing eyes allowing them to have a more precise visual perception of what’s on the ground around them.

On the other hand, aquatic species such as snapping turtles have their eyes located at the top of their head. Night vision is common among soft-shelled turtles that hunt at night, and their retinas have more rods to discern more light spectrums beyond what is visible to the human eyes. 

Sea turtles are better adapted for muddy coasts and seeing through the darkness of the sea by having the lens behind the cornea handle all of the focusing needs. These variations extend to the size of the eyes, larger lenses, and the ability to see the bioluminescence of prey at night.

This article digs deeper into the appearance of turtle’s eyes, their eyesight as well as eye problems in turtles.

Can Turtles See Colors?

Human eyes can perceive within the wavelength of about 400nm to 740nm. While turtles might see other vision wavelengths, they can also perceive colors within 400 nm to 740 nm. They seem to be more sensitive to shorter wavelengths around 300 to 370 nm, which falls within the range of UV light.

Surprisingly, it used to be thought that turtles could see the world in greyscale. However, research has proven this to be incorrect and that turtles can differentiate between different colors. In fact, turtle eyes have UV receptors capable of perceiving more colors than humans.

They possess the CYP2J19 that makes them sensitive to shades of red more. The gene helps them to different shades of red better than us. Not only do turtles see color, but research has also shown that they can see a broader spectrum of colors.

Owners have noticed that turtles can react better to colors such as orange, yellow, and red.  When they see objects with these colors, they seem to be curious about them. Most of the time, they want to investigate if the thing is edible.

Can Turtles See In the Dark?

Generally, humans can see better in the dark than turtles do. In other words, turtles lack excellent night vision. Like humans, their iris narrows and pupil constricts during the day. This reflects more light away and allows little light in to ensure our eyes aren’t overwhelmed by the amount of light. When it’s dark, the pupils enlarge to let in more light since there’s less light. This allows them to see pretty well in the dark. However, if the light goes off all of a sudden, the eyes may need some time to adjust. After that, turtles can see things clearly. It’s probably why you’ve been seeing your turtle moving around its tank at night.

However, note that turtles are not nocturnal because they lack tapetum lucidum, just like humans. This is a thin layer found in the eyes of several vertebrates like cats, dogs, deers, lemurs, and more. The tapetum lucidum allows light to reach the retina, the reason why nocturnals like owls can see better in the dark.

What Color Are Turtle Eyes?

Like most animal species, the color of eyes can differ from turtle to turtle, but there are defining colors for each subspecies. Most turtles have a yellow-brown eye color with a black pupil. The second most popular eye color is darker and brown variations, but some species have distinctive colors from others.

Also, gender determines the eye color, with most females showing yellow to brown and males a reddish-brown color. However, there are exceptions where males have lighter eyes than females. For example, male mangrove terrapins of S. Asia and India have light-colored iris while the females of the same species have brown eyes.

Other species like cooters have green and yellow eyes. The ornate box turtle has green eyes. Wood turtles of central America have bright blue eyes. Other turtles with blue eyes are Spanish terrapins in Mexico and the brown-roofed turtles of India.

It’s also worth noting that turtles of the same species can have different eye colors. For instance, the false map turtles are two subspecies – the Midwest false map turtle and Mississippi false map turtle. The Midwest subspecies have a yellow-brown iris with a black bar that runs horizontally across the pupil. On the other hand, the Mississippi subspecies have a white Iris and black pupil with no bar, perhaps because the pupil is black.

How Do Turtles See Underwater?

Ever been into a swimming pool and tried to open your eyes underwater? The view is murky and unfocused. The curvature of our cornea refracts light which enables us to see clearly. For aquatic animals such as turtles, their cornea is merely a protective barrier for their lenses that can refract light underwater. Unlike humans, turtles need to see both when submerged and underwater.

They can easily accomplish this by having spherical lenses and flat corneas. Besides, they have an even distribution of cones and rods, which make their eyes better suited for bright light. It’s no surprise why turtles are diurnal creatures. Additionally, some studies suggest that sea turtles can see bioluminescence underwater, which helps them locate their bioluminescent prey deeper in the sea.

How Do Turtle Eyes Adapt to Deal With Obstructed Vision?

Turtle eyes are located on the side of the head, which poses a challenge to their visual range when the head retracts back into the shell, obstructing their vision. Researchers have found that turtles have evolved to have their eye muscles operate as if their eyes were both on their side of the head and in the front. This works by coordinating the direction 0f pull in each of the eye muscles, ensuring that the eye’s position remains in focus even when their peripheral vision gets obstructed by the shell. 

Turtles can move their superior oblique muscles when turning their head from side to side, allowing them to focus on objects directly in front of them when their head is retracted deep into the shell. The change in eye reflexes depending on the position of the turtle’s head allows these semi-aquatic animals to survey their environment even when in danger and improve their hunting outcomes when pursuing prey. 

How Far Can Turtles See?

Turtles can see far much better underwater compared to when they are on land. Since they feed inside water and have to hunt underwater, it’s the reason their vision has evolved so much. They mainly have flat corneas and spherical lenses, two features that enable aquatic turtles to see underwater. The same features make turtles near-sighted out of water. However, being short-sighted out of the water is not a significant disadvantage because they only come out of the water to breathe in air and bask.

Why Does My Turtle Has Swollen Eyes?

Puffy eyes are not uncommon in turtles, primarily due to vitamin A deficiency and unclean water. If your turtle is suffering from this disease, you need to find a solution as soon as possible. Unfortunately, there’s little you can do to save the turtle as an average owner. Immediate professional help is needed. The vet closely examines your turtle to find the issue and prescribes foods and medicines for your turtle.

Symptoms of Problematic Eyes in Turtles

Discharge – fluid discharge or tears are a clear sign of eye problems, mainly due to dehydration. Sometimes, it could be a symptom of more significant issues such as a virus and bacterial infection from the water. If the discharge appears like pus, you can be almost sure it’s an eye infection. For this, you should see a vet immediately.

Swelling – eyes that become puffier than average could be due to a variety of factors. Swelling the gland behind the eyes near the ears may result from vitamin A deficiency but could also be caused by injury or overexposure to UVB. If the eyelids are also swollen, it could be a bacterial infection that requires a vet’s attention.

Continuous rubbing – just like humans, turtles rub their eyes when they experience discomfort. Although turtles get allergic reactions, the symptom may also result from too humid or too dry air, especially if the turtle can’t keep its eyes open.

Sunken eyes – if the eyes appear swollen yet sunken, it might be a sign of dehydration. Always ensure they have access to plenty of fresh water and that the enclosure has a comfortable temperature. Also, a low humidity level is a possible cause and can even lead to the inability to open eyes.

Red and inflamed eyes – there are many conditions in turtles that can cause the tort’s eyes to appear inflamed. It can be caused by overexposure to UVB light. If this is the case, you need to keep your UV bulbs switched on for at least 10 hours every day. Another cause of red, inflamed eyes respiratory infections.

Other symptoms include:

• Turtles may lose weight
• Loss of appetite
• Difficulty breathing

Causes of Swollen Eyes in Turtles

Vitamin A deficiency

Vitamin A consists of retinoids such as retinol and provitamin A such as beta-carotene. The pigments can be found in veggies and algae. The leading roles of vitamin A include maintaining the skin, ears, mouth, eyes, and mucous membranes. This problem is common among turtles and particularly the pet box turtles.

If it’s a case of swelling of the Harderian gland of your turtle, you can be pretty much sure that it’s a vitamin A deficiency. Also known as Hypovitaminosis A, it’s a common condition but preventable. especially in captive turtles. When it occurs, it can cause squamous metaplasia, a condition that blocks eustachian tubes and the inner ear, leading to the accumulation of dead cells.

As a result, Vitamin A deficiency can lead to other health problems such as aural abscesses and related infections. If the swelling and condition are especially severe, the vet should inject a dose of vitamin A. You also need to feed your turtle a nutrient-rich diet containing adequate vitamin A. rich sources of vitamin A include dark leafy greens such as red peppers, winter squash, parsnips, sweet potatoes, etc.

Turtles use Vitamin A to maintain a healthy mucous membrane in the upper respiratory tract. This acts as an essential physical barrier against germs that lead to respiratory infections. The most common symptoms of Vitamin A deficiency are swollen pus-filled eyes, respiratory issues, unexplained stunted growth, lethargy, white patches, anorexia, mouth rot, and ear abscesses.

What causes Hypovitaminosis A to develop? Well, it’s the overreliance on turtle pellets among pet owners who believe this is the only thing to feed them. Most aquatic pet turtles must eat a plant-based diet, especially when they reach maturity. These vegetables to include in their diet include dark green lettuce, dandelion leaves, and veggies like squash, cucumber, and zucchini.

Eye infection

In some cases, the swelling can be caused by bacterial infection due to poor water quality. Aquatic turtles can be messy eaters who leave the water contaminated with leftovers and feces. Poor quality water that stinks is likely to harbor thousands of bacteria that can cause severe health issues for the turtle. If the condition is not addressed on time, the bacteria can move to other body organs, such as the respiratory tract. Infections that reach the respiratory tract can cause death.

Common Symptoms of Eye Infections

• Puffier eyes than normal
• Teary eyes with discharge
• Edges of the vision appear red
• Reddening of the conjunctiva
• Small white spots on the cornea
• Turtle wants to scratch and rubs the eyes

Since eye infections can be confused for respiratory tract infections, you also want to look out for Respiratory Tract Infections such as:

• Sneezing and wheezing
• Discharge from mouth and nose
• Loss of balance when swimming

As opposed to swollen eyelids, and eye infections caused by bacteria can be more severe. A big concern with a bacterial infection is how quickly it can spread to the mouth and nose. Although the symptoms can easily be confused with swollen eyelids, there are quite a few key differences to look out for. Sometimes the bacterial infections can spread from the fish to the turtle’s eyes.

The best way to prevent bacterial infections is to clean the aquarium every week and carry out nitrite and ammonia level tests to ensure they stay below recommended levels.

Other causes of swollen eyelids apart from Vitamin A deficiency and bacterial infections include:

Dehydration

Another cause of swollen eyes is dehydration. The fact that turtles lose lots of water through their eyes at a rapid rate can result in dehydration if there’s a water shortage. Box turtles especially need plenty of humidity in their habitats to prevent eye woes. If your turtle is healthy, dehydration is likely the cause of swollen eyelids.

If you think dehydration is the cause of swollen eyelids, you should ensure access to enough water in their enclosure at every time of day. Lettuce and cucumber also provide extra moisture to address this. Cactus is also an excellent rehydration food for turtles and can grow in most areas.

Watch out for foods that trigger a diuretic effect or substances that lead to more water loss, for example, dandelions. This easy food source will grow in your home, but you should moderate its use.

Besides, test to see if the humidity levels in their enclosure are enough according to the turtle species. For instance, ornate box turtles love lower humidity around 60%, while gulf and Florida require slightly more, around 90%. Most of the time, 60% to 100% should work for most turtles.

Issues with humidity

Whenever turtles feel the air drying out around their eyes, their natural reaction is to keep their eyes closed. Like in humans, dry air can affect a turtle’s vision to the point where it feels like there’s sand stuck in there.

If the problem is not low humidity, the opposite may be the cause. Too much humidity can make the air around them stagnant and lead to bacteria growth and the formation of allergens, leading to eye problems. To avoid this, ensure your turtle’s enclosure has adequate ventilation.

Trauma

Your pet turtle’s swollen eyes could be a result of an eye trauma they experienced recently. It could be a pointed accessory in the enclosure that has poked the eyes, or there has been a fight with another turtle. Too many obstacles in their enclosure can scratch their eyes, causing injury. Consider removing any sharp objects from the turtle’s enclosure, such as tank decorations.

Also, heat lamps that are too close can dry their eyes out. Also, eye injuries can result from sand and dirt entering the turtle’s eye and causing irritation. It’s the reason why you need to keep a turtle’s substrate damp, so they don’t get kicked up into the air.

How to Treat Swollen Eyes in Turtles?

There are three ways you can address swollen eyes in turtles: through diet, improving water quality, and getting help from the vet.

Offer a wide range of foods

It’s impossible to give your turtle the same diet he would get in the wild, so you may have to provide them with a diet with a complete nutrition profile. A mistake many pet owners make is to give their turtles commercial pellets only. While pellets are nutrient-rich, they shouldn’t form 100% of the diet. You also need to provide live prey and greens.

Along with pellets, omnivore turtles should eat veggies such as dandelions, mustard greens, collard greens, and romaine lettuce, which have a decent amount of Vitamin A. Swiss chard is recommended for Vitamin A but should only be fed once in a week because it contains oxalates which can interfere with calcium absorption. Carrot and cooked sweet potato provide high levels of carotenoids but should be used occasionally due to high sugar levels.

Many turtle owners also provide vitamin A supplementation by giving the turtle gut-loaded insects. These are insects that were fed vitamin-rich foods before being fed to the turtle. You can do this yourself or look for shops that sell gut-loaded insects like crickets. Make sure the turtle gets a gut-loaded insect diet once a month.

Keep in mind that juvenile turtles need more protein than adults because their growth is more rapid. For example, omnivore juvenile turtles need to have 60% live prey items in the diet compared to 40% in adults. On the other hand, adults need more greens: 40% of greens for adults and 20% of greens for juveniles.

Ensuring that the pet’s dietary needs are met is by far the easiest way to prevent Vitamin A deficiency from happening.

Improve the water quality

Turtles are pretty messy and can fill the water with leftovers and feces in no time. As such, you need to take a few measures to maintain good water quality. Check out these tips.

Check the tank size – as said above, turtles can mess a lot, so you need more water to keep the waste to water concentration lower. A general rule of thumb is to have 10 gallons of water for every inch of their shell size. For instance, if the shell is 5-inch long, you’ll need a 50-gallon tank or more. Smaller tank size is harder to clean and the number one reason for poor water quality.

Get a powerful filter – turtles produce more waste than other reptiles and fishes, so you need a more efficient filter to cope up with the high waste production. There are filters that have been specially designed for turtle tanks with more capability. Also, consider cleaning the filter regularly to keep it working at its best. Too much chlorine in water can clog the filter.

Perform water changes regularly – no matter how efficient the filter is, no filter can cope up with the load for an indefinite amount of time. You need to do entire water changes weekly or at least 50% changes per week. Water that stinks can keep too much bacteria and trigger a secondary infection such as swollen eyes.

Vitamin A eye drops and supplements

Vitamin A eye drops are used to treat turtles with sore eyes as a result of Vitamin A deficiency. Some of the vitamin A in the drops is absorbed through the turtle’s eyes. These drops seem to work so well, and you’re likely to see an improvement in a few weeks. The problem with eye drops is they are a band-aid solution. As such, you can just use them while awaiting the vet’s treatment. They are not a long-term cure for vitamin A deficiency.

For a long-term cure, your best bet is supplements packed with Vitamin A. However, most turtle experts suggest the use of gut-loaded insects as a means of vitamin A supplementation. Ensure to feed your turtle gut-loaded insects regularly alongside its diet.

Your vet can also provide supplementation with Vitamin A injections. Sometimes they can also prescribe antibiotics and oral drops. In some cases, a blood test will be needed to determine the levels of Vitamin A.

Make sure you never miss appointments and follow the changes the vet tells you to. That said, prevention is by far the safest way to deal with the condition. The turtle owner should improve the diet of their turtle to prevent relapse. Although Vitamin A deficiency is the leading cause of swollen eyelids, it isn’t always the cause.

What Is This Stringy Discharge from Turtle Eyes and Ears?

A white stringy discharge from your turtle’s ears and eyes is usually a sign of an abscess. This is related to hypovitaminosis A or a lack of adequate vitamin A. the pus-filled swellings can occur anywhere inside a turtle’s body. Still, it’s more common near the eyes and ears.

Apart from vitamin A deficiency, another cause of abscesses is poor water quality, wrong temperature or humidity for your turtle species, or problems with the water filter. Abscesses escalate quickly in turtles and sometimes require immediate vet care. When treated early, you can quickly stop them by trying a different diet and ensuring water is clean and of standard quality.

However, if not caught early, you need to book an appointment with the vet, or you may watch their health deteriorate. The vet treats abscesses by administering anesthesia to the lump, making an incision, and draining the fluid out to remove the infection. The condition is disgusting, but they are generally less severe and usually don’t lead to death.

Conclusion

Turtles have evolved over the millennia to have a specialized vision to best fit their habitats and the challenges of living a semi-aquatic life. From hunting prey to running away from danger, turtles require their visual perception at all times, and their eyesight must remain healthy at all times.

Be sure to feed your turtle a range of foods, including those with vitamin A such as veggies and gut-loaded insects. Chlorine water can also irritate turtle eyes and even cause blindness. Change the tap water regularly to prevent bacterial infections. In case of puffiness, use eyedrops and consult a vet.

This guide should help you understand your turtle’s eyes much better and equip you with the knowledge you need to keep them happy and healthy.