The ketogenic diet, or keto diet, has gained significant popularity as a weight-loss plan in recent years. It's a high-fat, low-carbohydrate diet that shifts the body’s primary energy source from glucose to fat. This shift leads to the production of ketones, molecules the body uses for energy instead of glucose from carbs. While many have found it effective for weight loss and other health improvements, some individuals have reported experiencing blurred vision after starting the diet. This article explores the potential causes of blurred vision on the keto diet, its connection to underlying conditions, and ways to manage and prevent it.
What is the Keto Diet?
The keto diet is a high-fat, low-carb, normal-protein diet that aims to keep the body stable, known as ketosis. Typically, glucose-derived from seeds, starches, and refined sugar-is your body’s primary fuel source. A ketogenic diet results in rich keto and encourages the body to burn fat rather than glucose. The term “ketogenic diet” was developed by Dr. Russell Morse Wilder, who started using it to treat epilepsy in 1921, especially when medication was ineffective.
On the ketogenic diet, maintaining ketosis depends on eating the appropriate proportions of lipids, proteins, and carbohydrates. Even consuming too much protein can cause problems. The recommended daily intake of carbohydrates ranges from 20 to 50 grams, with a cyclical diet allowing up to 600 grams per day, but only on specific days.
Potential Causes of Blurred Vision on Keto
Several factors associated with the keto diet may contribute to blurred vision. These include electrolyte and fluid imbalances, dehydration, and blood sugar fluctuations.
Electrolyte and Fluid Imbalances
As you transition into ketosis, your body burns through your glycogen stores, the backup supply of carbs stored in your muscles and liver. These carbs are stored with large amounts of water, which contain electrolytes, such as potassium and sodium, that help regulate your body's fluid balance. As you burn through your glycogen stores, all of the water and electrolytes they contain are flushed out through your urine. This can cause dizziness if you're not drinking enough, not adding enough salt to your diet, or both, according to Jean LaMantia, RD, a registered dietitian in private practice in Toronto.
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When there are huge shifts in electrolyte levels, such as those that occur when you first start keto, you're also likely to experience so-called “keto flu” symptoms. These fluid losses can easily lead to dehydration, which can cause extreme thirst, dry mouth, dry skin, and dizziness. Additionally, electrolyte losses may also cause dizziness because they can lower your blood pressure, says LaMantia.
Dehydration
Another potential cause of blurry vision on a low-calorie diet is dehydration. "Dehydration can trigger eye strain, which in turn can lead to tired eyes and blurry vision," says Palinski-Wade. "Since the brain is made up mostly of water, dehydration can also impair mental function, which in turn can impair vision in a similar way as low blood sugar. If you're dieting, keep tabs on your fluid intake as you scale back on calories.
Blood Sugar Fluctuations
Dialing back on carbohydrates can have a major impact on the amount of sugar in your blood. "A keto diet provides very few carbohydrates, the macronutrient easiest to convert into glucose in the body," Palinski-Wade says. When you go long periods of time without eating, such as during a fast, the body can drain energy stores and see a drop in blood sugar levels," she says.
Blurry vision from low blood sugar isn't likely to cause permanent damage. Glucose is the main source of energy to the brain. Fortunately, blurry vision from low blood sugar isn't likely to cause permanent damage. Still, Palinski-Wade says that blurry vision on keto is unlikely for most people. However, you'll need to be more careful if you have diabetes.
The Connection Between Keto, Diabetes, and Eye Health
The health of your eyes is directly connected to the health of your heart and blood vessels. It may seem strange that what you eat could affect how well you see, but there's a scientific reason behind the diet-vision connection.
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Blurred Vision and Diabetes
Blurry vision is a common symptom of diabetes, but many other things can cause it too. If you've already been diagnosed with diabetes, blurred vision could mean your blood sugar isn't being controlled well enough. It may also mean there's a problem in your eyes or another part of your body.
Different forms of diabetes can cause blurry vision. The most common types are:
- Type 1 diabetes - Your immune system mistakenly stops your pancreas from making insulin.
- Type 2 diabetes - There is a problem with the way your body makes or uses insulin. More than 9 in 10 people with diabetes have this type.
- Gestational diabetes - This is high blood sugar in a non-diabetic woman during pregnancy.
Normal blood sugar is between 70 and 100 mg/dL after fasting for at least eight hours. You have hyperglycemia when your blood sugar is over 180 mg/dL one to two hours after a meal. This target number may be higher or lower, depending on what your doctor says. Hypoglycemia usually means your blood sugar level is below 70 ml/dL.
High glucose levels can make parts of your eyes swell up. Too much swelling makes it harder for your eyes to focus, so objects look blurred or fuzzy. Blurred vision should go away as your blood sugar level gets closer to normal. Low blood sugar can cause blurry vision and other symptoms like feeling hungry, dizzy or anxious, feeling weak, exhausted or confused, and sweating. These symptoms should go away when your blood sugar goes back to normal.
Diabetic Retinopathy
The retina is a thin layer of cells in the back of each eye that helps you see. Diabetic retinopathy happens when the retina's tiny blood vessels are damaged. Researchers believe around 1 in 3 diabetic people have some level of diabetic retinopathy. It's the top cause of vision loss in people with diabetes.
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At first, diabetic retinopathy usually doesn't cause symptoms and is painless. Routine dilated eye exams can help you catch these problems early on and save your eyesight. As retinopathy gets worse, it can cause symptoms like blurred vision, eye floaters (small spots or shapes in your vision), eye pain, night vision problems, and vision loss.
Diabetic retinopathy happens because your blood sugar levels are too high. By controlling your glucose levels, you may be able to prevent future vision loss or even reverse some existing damage. People with more advanced retinopathy may need treatment from a medical eye doctor (ophthalmologist).
Retinopathy increases the risk for other diabetic eye problems that cause blurry eyesight and, potentially, vision loss. They include:
- Diabetic macular edema (DME): DME is when diabetic retinopathy causes swelling in the small spot on your retina called the macula. This can cause blurred vision, worsening eyesight over time, objects that look wavy or curved, faded colors, and loss of vision in the center of your eyesight. Managing your blood sugar and other treatments could help your DME symptoms and protect your eyesight.
- Neovascular glaucoma (NVG): Blood vessel problems in your retina can raise the pressure inside your eye. If it gets too high, it can damage your optic nerve and other parts of your eye that help you see. This is called neovascular glaucoma (NVG). It can eventually cause blurry vision, sensitivity to light, a red, painful eye, and vision loss. Diagnosing and treating NVG early can help you keep as much of your eyesight as possible.
- Retinal detachment: As it worsens, scarring from diabetic retinopathy can make your retina peel away from the back of your eye. This is an urgent problem called tractional retinal detachment. It needs to be treated right away and can cause sudden blurry vision, the appearance of a dark curtain or shadow over part of your vision, many new eye floaters, flashes of light, and vision loss.
Other Diabetes-Related Vision Problems
Other diabetes-related complications and side effects can make your vision blurry, too. Some of them are:
- Cataracts: High blood sugar raises your risk of getting cataracts. The cloudiness of a cataract changes the way light enters your eye. This can cause symptoms like blurry vision, light sensitivity, problems seeing in low light, yellowed or dull colors, and double vision. These problems can be treated with cataract surgery.
- Reactions to treatment: The hormone insulin can be prescribed to help your body use glucose better. It can cause vision changes for a little while after you start taking it. Blurriness can also be a sign of a serious insulin side effect, so tell your doctor if you notice it. Diabetic drugs like metformin can cause blurry vision, too. Blurred eyesight is a relatively common side effect, but you should still tell your doctor if you experience it.
- Inaccurate eye prescription: Diabetic blurry vision can come and go over time. If it's causing fuzzy vision during an eye exam, your eye prescription might not be accurate when your blood sugar is normal. This means your eyesight won't be as sharp as it should be when you're wearing glasses or contacts. For the best results, your blood sugar levels should be stable for at least one full week leading up to your exam.
- Dry eye: A diabetic person is twice as likely to have dry eyes as someone who doesn't have diabetes. This can cause blurred vision that gets better when you blink, watery eyes, red eyes, scratchy, stinging or burning feelings in your eyes, and light sensitivity. Dry eye sometimes goes away as soon as your blood sugar is under control. Other people may need to use dry eye drops, punctal plugs or other treatments.
- Diabetic ketoacidosis: Chemicals called ketones can build up in your body when it doesn't make enough insulin. This can lead to a life-threatening emergency called ketoacidosis. It needs to be treated right away. Ketoacidosis is more common in people with type 1 diabetes, but it can also happen with type 2 diabetes that requires insulin. It can affect someone who hasn't been diagnosed with diabetes, too. Some of the warning signs are feeling really thirsty, urinating a lot more than usual, stomach pain, nausea, vomiting or diarrhea, tiredness or confusion, and blurred vision.
- Stroke: Diabetic people are twice as likely to have a stroke. Some of the warning signs are one side of the face is drooping, one arm is weak, speech sounds strange and doesn't make sense, problems understanding others, and vision is suddenly blurry. A stroke is an emergency. Get medical help right away if you have stroke symptoms.
Prediabetes and Vision
Prediabetes is high blood sugar that isn't high enough for a doctor to diagnose it as diabetes. More than 1 in 3 American adults have it. Prediabetes itself rarely causes blurred vision, but it can still damage your eyes. The harmful effects of diabetic retinopathy can start while your blood sugar is still in the prediabetic range. If you have prediabetes and start to notice blurry vision, it could mean you now have type 2 diabetes and need to start treatment.
Managing and Preventing Blurred Vision on Keto
Fortunately, blurry vision from low blood sugar isn't likely to cause permanent damage.
Staying Hydrated
These fluid losses can easily lead to dehydration, which can cause extreme thirst, dry mouth, dry skin, and dizziness. If you're dieting, keep tabs on your fluid intake as you scale back on calories.
Balancing Electrolytes
Electrolyte losses may also cause dizziness because they can lower your blood pressure. When there are huge shifts in electrolyte levels, such as those that occur when you first start keto, you're also likely to experience so-called “keto flu” symptoms.
Monitoring Blood Sugar
Blurry vision is a common symptom of diabetes, but many other things can cause it too. If you've already been diagnosed with diabetes, blurred vision could mean your blood sugar isn't being controlled well enough. It may also mean there's a problem in your eyes or another part of your body.
Incorporating Eye-Healthy Foods
The keto diet is rich in nutrients that are good for the eyes. Fish, leafy greens, peppers, and squash are just a few of the components in the keto diet. Try incorporating these foods into your daily meals to ensure you're getting enough eye-healthy nutrients on the keto diet.
Regular Eye Exams
Routine dilated eye exams can help you catch these problems early on and save your eyesight. An early diagnosis is one of the most important ways to stop diabetic eye disease from permanently damaging your vision.
Does Blurry Vision from Diabetes Go Away?
It depends on what's causing it. Temporary blurred vision can usually be corrected, but other diabetic eye conditions can cause permanent vision problems. Keep in mind that many things can cause blurry vision, including common problems like eye strain and nearsightedness. An eye doctor can help you figure out whether your symptoms are related to diabetes or not.
If it's caused by a temporary spike or drop in your blood sugar, blurry vision should go away once your glucose levels are back in the normal range. If it's connected to a condition like diabetic retinopathy, some blurriness could be permanent. But you may be able to get part of your vision back if you control your blood sugar well.
When to See an Eye Doctor
Any time you experience blurry vision, you should speak to your physician to determine the cause. If you have diabetes and blurred vision, it could mean your blood sugar isn't being controlled well enough. It can also be a sign of several serious eye problems. Talk to a doctor as soon as possible and tell them your symptoms. People with diabetes have a higher risk of having a stroke and should get medical help right away if they have stroke warning signs, which can include sudden blurred vision.
The Broader Impact of Diet on Eye Health
Generally, we’re aware of foods that aren’t very good for overall health, but have you considered that some foods do not support healthy vision and may contribute to vision loss? The American Heart Association recommends aiming for about 5 to 6% of daily calories from saturated fat. A healthy diet leads to healthy eyes; an unhealthy diet leads to unhealthy eyes.
Foods to Avoid
- While delicious, the carbs found in pasta and white bread have been linked to a higher risk of eye diseases. When broken down, simple carbs cause a spike in blood sugar. A diet rich in simple carbohydrates can also cause weight gain and increase the risk of high cholesterol and heart disease.
- A high sodium diet with frequent salt spikes can lead to high blood pressure (hypertension). Over time, hypertension causes profound damage in the eye including blood vessel damage, a buildup of fluid beneath the retina, and a blockage of blood flow that kills nerves.
- Health experts recommend staying away from food items that include hydrogenated oils and trans fats. Cooking oil with less than four grams of saturated fat per tablespoon is recommended. Margarine is considered a healthy alternative to butter but is full of trans fats that can increase blood cholesterol levels.
- Soda, sports drinks, energy drinks, and other sweetened drinks can contain up to 7 to 10 tablespoons of sugar per drink.
Potential Benefits of Keto for Eye Health
While the keto diet may present some challenges for vision, there is also evidence suggesting potential benefits, particularly in the context of glaucoma and retinal degeneration.
Glaucoma
In a study published in the Journal of Neuroscience, researchers observed that in humans and mice with glaucoma, the optic nerve tended to be metabolically stressed. The team selected a special breed of mice known to develop glaucoma. The mice ate a “regular” (high-carb) diet for the first nine months before they were switched to a keto diet of approximately 10% protein and 90% fat. After eight weeks of keto, the researchers sacrificed the mice to examine the structure and function of their eyes and optic nerves. The scientists who performed this study did so under an NIH grant.
Retinal Degeneration
According to a study done by NHI, one of the side effects of keto is that it helps shield the eyes against retinal degeneration and mitochondrial illnesses. A ketogenic & low-protein diet slows retinal degeneration in rd10 mice. Removing unneeded sugars from the diet reduces the risk of macular degeneration. A Tufts University study found a link between macular degeneration and a high glycemic index, which suggests consuming lots of bread, pasta, and rice.