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Sight in the Dark: How Night Vision Works and Which Animals Can See at Midnight

Sight in the Dark: How Night Vision Works and Which Animals Can See at Midnight

As the days get shorter, you’ll have to face the dark when you go outside in the evenings. Maybe in the summer you could walk your dog after dinner and come home before the sun set, but not anymore. The nights will continue to get longer until late December.

If we could see better in the dark, we wouldn’t mind the change so much. But human eyesight functions much better during the daytime. Keep reading to find out why that is and why some animals see much better than you do after dark.

How Do We See in the Dark?

The human eye lets light in through a hole called the pupil. A lens inside the eye focuses the image, and the retina detects that image—you might picture the retina as the wall a projector puts the image on. The retina contains two structures called rods and cones that detect light and send the image to the brain.

Rods are great at capturing very dim light and movement. However, they do not detect colors. We can see colors so vividly because of cones, which can only function when there is plenty of light. We have four times the number of rods than we have cones.

This ratio means that we see pretty well during the day, and though we have more rods than cones overall, we have more cones than many animals. We can see many kinds of colors during the day, and we still see reasonably well in the dark.

However, other animals that have more rods and fewer cones than we have can see even better in the dark, even if their color vision during the day isn’t as good.

Which Animals Have Great Night Vision?

Many nocturnal animals have spectacular night vision, including some animals you’ve heard of. Learn what makes their eyes work so well at night.

1. Cats

If you have a cat, you’re probably aware that your kitty finds his or her way around the house during the nighttime perfectly well. If your cat goes outside, you know that your pet has plenty of adventures after dark.

Cats have 25 rods per single cone in each eye, instead of our four-to-one ratio. This means that your pet doesn’t have many cones and therefore doesn’t have very good color vision. However, your cat can see with just one-eighth of the amount of light we would need.

The extra rods aren’t the only advantage cats have. Our pupils can widen and narrow to let in more or less light, depending on how bright it is where we are, but cats’ pupils widen much more than ours. Additionally, cats have a reflective tissue behind their retinas. It’s called the tapetum lucidum, and it basically bounces light around inside the eye so that the eye needs less input to see. This layer is also why your cat’s eyes glow in the dark.

2. Owls

Owls are much smaller than humans, but our eyes are nearly the same size. Owls’ extra-big eyes are great for capturing as much light as possible, making use of whatever glimmers of light are available. The results are great—if you put an owl on a soccer field lit by a single candle, with no other illumination from the moon or stars, the owl would probably be able to see a mouse anywhere on the field.

However, because owls’ eyes are so big for their head size, they cannot swivel their eyes inside the sockets like we can. In order to see from side to side, the owl has to turn its head. To compensate, owls can turn their heads almost completely around, granting them a wide vision field.

3. Tarsiers

The tarsier is a tiny primate in Southeast Asia. The little animals are only about four inches long, excluding their tails. However, their eyes are about half an inch wide, which means their eyes take up nearly their entire head. Tarsiers have the biggest eye-to-body-size ratio known in the animal kingdom.

Tarsiers are nocturnal predators, looking for insects and small lizards or birds when there is little to no light available. They have to be able to spot and stalk prey in the treetops, jumping from branch to branch in the dark, and their prey is tiny and often camouflaged.

Like owls, tarsiers’ huge eyes gather and reflect any speck of light available to give them a clear picture of their surroundings. Again like owls, their eyes are so big that they can’t move in their sockets, so tarsiers can turn their heads 180 degrees.

 

Other animals can see well in the dark in different ways. Snakes, for example, rely less on rods in their retinas and more on thermal vision, which lets them see the body heat of nearby mammals. Bugs have very different eyes from ours. They don’t have rods and cones, but their eye structure has still evolved in some species to see well in the dark.

Though you’ll never see as well as a cat in the dark, if you feel that your eyesight isn’t what it should be, come to All About Eyes. Humans can suffer poor night vision as a result of problems like cataracts or nearsightedness. We’ll do a full evaluation of your eyes and help you find effective treatment.

Stressed Out? How Stress Affects Your Eyes

Stressed Out? How Stress Affects Your Eyes

If you’re going through a busy patch in your life, you may be feeling the effects of stress. Maybe you’re grouchy, tired, and on edge, or maybe you constantly crave comforting foods, no matter how unhealthy they are.

However, did you know that stress can also affect your eyes? During this difficult time when your life feels much too busy or difficult, your eyes can pay a price like the rest of your body does. Learn what eye symptoms can result from too much stress and what to do about them.

What Are Common Stress-Related Eye Problems?

Most stress-caused eye issues are temporary—if you have a consistent issue with your eyes, no matter what’s going on in your life, the problem is likely with your eyes instead of your stress level. Make sure to see an eye doctor if you have persistent eye trouble.

But when you have a massive deadline or your children all get sick at the same time, you may notice these problems:

  • Tunnel vision. You may lose some of your peripheral vision and feel like you can only see straight in front of you.
  • Sensitivity to light. You may feel like bright light hurts your eyes or makes it difficult for you to see.
  • Eye twitching. Maybe one, or both, of your eyes will randomly spasm.
  • Very dry or very wet eyes. While these are opposite symptoms, either one can be caused by stress. It all depends on how your body responds to a difficult situation.
  • Blurry vision. When caused by stress, blurry vision will probably be mild instead of severe.
  • Eye strain. Eye strain may be caused by something simple, like staring at your computer screen too long at work. However, it can also be caused by stress.
  • Eye floaters. Eye floaters are tiny spots that swim across your vision.

These symptoms are usually not terrible—you can live with them without seeing an eye doctor. The problems are more annoying than debilitating. However, if they last a long time or are very uncomfortable, you should still see a professional just in case.

What Causes Stress-Related Eye Problems?

When you get anxious, frightened, or stressed, your body’s instinct is to go into what scientists call “fight or flight” mode. Your body will start producing hormones like adrenaline, which speed up your heart rate, and your brain will direct more blood to essential functions like your internal organs and less blood to your extremities.

The reason your body takes these actions is to protect you. Your brain detects a threat when you worry about something, so its response is to gear up for either fighting the threat or running away from it. While this is a great response to physical danger, like an intruder in the home or a dangerous animal, it isn’t helpful for most problems that cause stress, like an argument with your spouse or a big project at work.

Though your brain’s response to stress isn’t helpful for non-physical problems, it still happens. When you’re in fight or flight mode, your eyes can suffer because your brain will cause your pupils to dilate. The idea behind this response is to get more light into your eyes so you can see any potential threats more clearly.

However, when you’re stressed out for a long time, the constant dilation makes you sensitive to light and can cause serious strain on your eyes. Additionally, when you’re very tense, as many stressed-out people are, the muscles in and around your eyes can tighten, causing twitching and soreness.

What Can You Do?

If you think that your eye problems are stress-related, you can start by trying to relax. Think about your symptoms as warning signs—your body is obviously trying to respond to a threat, and it’s hurting you. The best thing to do is to try to calm down your brain’s response to danger.

You probably know what de-stresses you better than anybody. However, if you need some ideas, try:

  • Taking a long, warm bath and focusing on how it feels
  • Meditating
  • Taking slow, deep breaths, sending the air into your belly instead of your chest
  • Writing in a journal
  • Exercising

As always, you’ll feel better if you make sure to get enough sleep and eat well. Even though you’re busy, taking at least a few minutes to consciously relax will help your body calm down.

If you feel stressed or worried most of the time, you may need to make bigger changes. You may be trying to do too much in too little time and need to cut back. Alternatively, you may have an anxiety disorder, which is highly treatable. If you constantly feel like you’re on edge, it might be time to speak with a doctor or counselor to make sure that you’re emotionally and physically healthy.

Once you’ve found a way to deal with your stress, your eyes should go back to normal. Stress-related eye issues should be temporary and easy to fix. However, if you continue to have problems, make sure to visit your eye doctor. The optometrists here at All About Eyes are ready to assist you so that your eyes are as comfortable as possible.

The Disabled List: Athletic Eye Injuries and Proper Safety Measures

The Disabled List: Athletic Eye Injuries and Proper Safety Measures

Plenty of people play sports for entertainment or to stay in shape, and while a great game of baseball can be fun, it can come with its share of accidental injuries. While taking care of your limbs and appendages is important, you should also remember to care for your eyes while playing.

When you get your protective gear together, remember to put the proper eye protection in your bag. Failing to do so can result in lifelong eye issues or other problems. Below, we’ll discuss possible sport-related eye injuries, eye safety, and the significance of eye exams so you can keep your eyes healthy.

Potential Eye Injuries in Sports

If you play tennis, racquetball, or basketball, your eyes could easily be at risk. Athletic eye injuries normally fit under three different kinds: blunt trauma, penetrating, and radiation eye injuries.

But no matter what type of eye injury you have, get immediate care to ensure you don’t have a serious condition. If you leave an injury untreated for too long, it could result in permanent damage or other issues, such as infections.

Penetrating

Penetrating injuries are exactly what they sound like. You’ll know you have a penetrating injury when an object cuts or embeds itself in the eye. While these injuries aren’t all that common, you should seek medical attention right away. And if there is something in your eye or another’s eye, absolutely don’t touch the object or move it. If you do, you could make the situation worse.

Radiation

If you like snowboarding or water sports, you may be subject to a ton of sun exposure. When your eyes aren’t properly protected from the UV rays, you can get a radiation injury. These are especially common with water and snow sports since the sunlight can reflect off the water and snow, creating a more harmful environment for your eyes.

Blunt Trauma

Some sports have quite a bit of physical contact, and you might find yourself with an accidental elbow to the eye, or a baseball may even hit your eye directly.

If there’s enough force, the bone around your eye could be fractured, and the pieces of bone could penetrate the eyeball and result in a ruptured eye. Liquids can leak out of the affected eyeball or the injury could open up the eye to infection or other issues.

But even if the bone doesn’t break or lodge in the eye, a well-placed hit to the eye could cause retinal detachment, which could affect your vision. Blunt trauma eye injuries are the most common of the three injury types, so you must properly protect your eyes to keep them protected as you play sports.

Athletic Eye Safety

When you play sports like racquetball, baseball, or soccer, wear protective goggles to guard your eyes against the odd fist or ball. But don’t choose just any goggles—find a pair that has been properly tested for sportswear and is approved for high-risk sports. The last thing you want is a malfunctioning pair of goggles when you need them most.

And if you’re worried about the goggles inhibiting your vision or performance, many goggles are designed with your performance in mind to ensure you’re at the top of your game while protecting your eyes.

If you’re regularly exposed to the sun and harmful UV rays, invest in glasses or goggles that adequately protect your eyes from the UV rays. For some sports, like hockey, you should have a helmet with eye protection. Or with baseball, you should have an adequate faceguard.

The Benefits of Eye Exams

Even if you have perfect vision, consider going to your eye doctor regularly to make sure everything is in great shape, especially if you’re often in the sun. Your optometrist will do a careful screening of your vision and eyes to spot any problems.

He or she can also provide great advice and suggest the best protective eyewear for any particular sport. And if you’ve recently been hit in the eye or otherwise injured, it’s always better to be safe than sorry and get your eye checked out. Your optometrist can also give you the best care tips for your injury, no matter how minor.

 

When you’re out on the field or on the court, don’t risk your eyes or your vision. Get the right gear and take the proper measures to guard your eyes from the elements, debris, and stray elbows. And if you do get an injury, get medical attention right away.

For an eye exam and advice, depend on an experienced eye doctor, such as All About Eyes. Our friendly, helpful staff can help you keep your eyes healthy, and we can offer suggestions for what you need. Give us a call today to schedule an appointment or discuss any concerns you may have.

Orthokeratology: A Noninvasive Vision Treatment Option

Orthokeratology: A Noninvasive Vision Treatment Option

If you suffer from poor vision, you’ve likely explored different corrective treatments. You’ve probably worn glasses or contacts to see properly, but now you want to see without the use of corrective lenses. While LASIK seems like a good treatment option, the procedure may seem a little too invasive for your preferences.

Rather than continue using contacts or glasses all the time to correct your vision, you may want to explore a noninvasive treatment option: orthokeratology. Below, we’ll explain what this treatment is and why your eye doctor might recommend it to improve your eyesight.

What Is Orthokeratology and How Does It Work?

As mentioned above, orthokeratology is a noninvasive treatment for poor eyesight. This treatment is also called Corneal Refractive Therapy (CRT), Ortho-K, or Overnight Vision Correction. The corrective method uses gas permeable contact lenses to temporarily reshape a person’s corneas. As the corneas are reshaped, refractive issues like far-sightedness, near-sightedness, and astigmatism are reduced.

In the 1940s, optometrists discovered that glass lenses could reshape a person’s cornea. Over the decades, eye doctors have developed different kinds of lenses to not only improve vision but also correct the cause of the issue.

During the early stages of development, the treatment wasn’t wholly successful because of the design and materials eye experts used for Ortho-K lenses. As new lenses were developed, researchers tested the materials to see if they could effectively reshape the cornea as patients wore the lenses during the day.

In the 1990s, corneal topography was invented and allowed professionals to examine the eye’s curvature and create custom lenses that could successfully reshape the cornea. When rigid gas permeable lenses were invented, orthokeratology became a nighttime treatment. The base material for these lenses allows more oxygen to enter the eye to prevent dry eye and similar irritations.

Today, eye patients wear these FDA-approved lenses as they sleep so they can see clearly during the day—without the need for glasses or contacts. Depending on what your prescription is and how rigid your eyes are, you could see results in as soon as one day. Typically, though, patients see results in about four weeks.

What Vision Problems Does It Treat?

While you can use orthokeratology to treat near-sightedness, far-sightedness, and astigmatism, eye doctors have recently used this method to treat childhood near-sightedness. This process is still undergoing research, but the idea is that orthokeratology can slow down childhood myopia and prevent children from experiencing poorer vision as they age.

Children as young as five years old can wear Ortho-K lenses, but ultimately, their eye doctors should determine if they are ready for this treatment option.

Additionally, orthokeratology isn’t a permanent treatment for poor vision. You must wear the lenses every night to experience clear, sharp vision during the day. If you stop wearing your lenses on a regular basis, your vision will revert back to your original prescription. This deterioration can occur as soon as 72 hours after you’ve stopped using the lenses.

Who Is an Ideal Candidate for Orthokeratology?

As with LASIK and other corrective procedures, orthokeratology has some requirements—and not everyone is an ideal candidate for this treatment. To qualify for this procedure, you must meet the following requirements:

  • Have low or moderate amounts of near-sightedness
  • Have refractive issues no higher than -6.00
  • Have an astigmatism error no higher than -1.75

For best results, patients should have refractive errors of -1.00 to -4.00, though the treatment will work if your vision falls within the parameters listed above.

To discover if you’re a good candidate for orthokeratology, schedule a comprehensive eye exam with your eye doctor. If your test results show that you’re a good candidate, your eye doctor can fit you with temporary lenses until your custom lenses are ready. Then, your doctor will fit them to your eye, teach you how to insert and remove them, how to clean them, and how to care for them.

What Side Effects Does This Treatment Have?

Like most treatments, orthokeratology does have a few side effects. Since you’ll wear lenses, you’ll still face the same risks you would if you wore traditional contact lenses. If you don’t clean your Ortho-K lenses properly or regularly, you increase your chances of getting eye infections.

You may also experience the following side effects:

  • Dry eyes
  • Inflammation
  • Eye injury
  • Allergies

You may notice the following vision-related side effects during the first month of treatment:

  • Double vision
  • Starbursting
  • Ghosting

Follow your eye doctor’s care instructions as you clean and wear your lenses to avoid serious issues or injuries. If any of these symptoms last for more than a month, see your eye doctor immediately. He or she can determine the source of these issues and either provide you with new lenses or suggest a different treatment option.

 

If you’re interested in correcting your vision without undergoing surgery, talk to your optometrist about orthokeratology.