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How UV Light Harms the Eye.

When it comes to the eyes—we only get two! Therefore we need to do our best to take care of the eyes we have.

One of the major culprits of eye damage is the sun. It’s something that is unavoidable, and therefore it is best to understand how to prepare and prevent as much sun damage as possible.


What Exactly Does the Sun Do to the Eye?

The sun emits UV light, specifically UV-A, UV-B, and UV-C.

UV-C light is the most dangerous and is typically blocked by the ozone layer. UV-A and UV-B, however, are ably to freely pass through the atmosphere and can penetrate through the skin and also the eyes.

We all have heard about how dangerous UV light sources are to the skin with the uprise in skin cancer cases. Therefore, we now know how important it is to wear sunscreen when going outdoors.

What is not commonly discussed, however, is that these harmful sunrays can pass into the eye even easier and cause just as harmful damage to the eyes as it does to the skin.

What is it about UV light that is so harmful to our bodies? A process called oxidative stress is the main culprit.

The sun is good in moderation, in general our bodies are able to take the UV light and break it down into useful, non-harmful components through a physiological process called oxidation. In the oxidation process, free radicals are broken down prior to entering cells and causing harm.

However, when we are exposed to too much UV light and the body is no longer able to keep up with the oxidation process, it undergoes oxidative stress and free radicals build up within the cells, causing irreversible damage.

Oxidative stress is one of the causes of cataract development as it causes the normally wellorganized cells of the lens of the eye to become disorganized. When the cells of the lens become disorganized the lens of the eye becomes hazy, cloudy, and yellow in color as the cells begin to break down.

These findings are all characteristics of cataracts.

While cataracts can develop as part of natural aging, we are finding that excessive sun exposure has been linked to early cataract development as well as more dense and advanced cataract development.

Cataracts typically do not begin to cause problems in individuals until they reach the age of 65 or older. However, with more exposure to UV light it is hypothesized that we will begin to see this age of cataract formation begin to become younger and younger.

Other ways UV light can damage the eye include creation of a pinguecula or pterygium (yellow thickened growths on the conjunctiva of the eye), UV keratitis, and macular degeneration (a progressive disease affecting the backmost structure of the eye called the retina).


How Can the Eye Protect Itself Against UV Light?

The eye has several mechanisms to protect itself against UV light. The main mechanisms are that the cornea, lens, and vitreous humor can all absorb UV light to prevent it from reaching the retina.

If too much UV light reaches the retina, it causes irreversible damage and death of light-detecting cells called photoreceptors. When this occurs, an individual can develop macular degeneration (death and destruction of the part of the retina responsible for our 20/20 vision) and even permanent vision loss.

Hence, the eye wants to have as many protective measures in place as possible to prevent UV light from ever even reaching the retina!

The cornea, lens, and vitreous humor, however, all have their breaking points and can only absorb so much at a time before losing the structural integrity.

If too much UV exposure occurs to the cornea, a person can develop UV Keratitis (also known as Welder’s Keratitis or Photokeratitis).

This is a very painful non-infectious inflammation of the cornea (very front structure of the eye) that appears 8-12 hours after excessive exposure to UV light. It is seen most commonly after skiing (UV light is reflected off snow, thus amplifying the amount of UV that reaches the eye), Welding, or spending time on water without sun protection.

Think about UV Keratitis almost as a sunburn on the eye. However, since the cornea has the most concentrated amount of nerves in the human body, it is like an extremely amplified sunburn.

If too much UV is absorbed by the lens, it creates a more chronic problem rather than just “sunburn”. Over time the UV absorption causes oxidative stress and cell denaturing of the lens cells—hence creating cataracts.

Another important protective mechanism the eye has against UV light is that it turns slightly yellow with age due to accumulation of vitamins zeaxanthin and lutein. These two vitamins are known to protect against oxidative stress, and therefore act as extra UV absorbers in the eye.

In short, we want high amounts of zeaxanthin and lutein in the eyes. Unfortunately, we do not reach adult levels of these vitamins until around the age of 20 years old.

This means that those under the age of 20 have a weaker defense mechanism against UV light and therefore are at an even higher risk of saturating the lens of the eye with UV and therefore developing cataracts earlier on in life.

In other words, the younger you are, the more important it is to protect your eyes against UV light to prevent serious damage from occurring to the eyes.

UV damage is something that accumulates over time to cause big problems—we do not want to accumulate an excessive amount before our eyes have even matured enough to defend against the UV particles!


Other Sources of Harmful UV Light

UV light is emitted from sources besides just the sun, too.

One of the most important ones to note is that electronic screens emit UV-B light. While we do not have enough research to state exactly what UV-B light from electronic screens does to the eyes, it is hypothesized that excessive screen time could result in early onset cataracts.

This is especially true with young children with excessive screen time as their eyes have not yet completely developed their UV protection mechanisms.

Other sources of UV light include tanning beds, black lights, fluorescent lights, lasers, and UV sanitizing lights.

While these sources all emit small amounts of UV light—very minimal in comparison to the sun—excessive use of them can accumulate to be large amounts of UV light absorbed by the body.


What Can I Do to Protect my Eyes from UV Light?

Ultimately, UV light exposure is impossible to avoid. UV light is a good thing in moderation, we just need to limit how much we are getting.

It is always a good thing to wear sunscreen when going outdoors. This includes on the face and eyelids too! Be sure to pick up a sunscreen that is safe for the face as the skin of the face and eyelids is a bit more fragile than on the rest of the body.

Wearing sunglasses when going outdoors is also important—especially for kids! Look for sunglasses with the UV protectant sticker on them.

Sunglasses are particularly important when going outdoors for extended periods of time, and when being around water, sand, or snow as all of these elements are known to reflect light and thus increase the amount of UV light being absorbed by the body.

Another way to protect your eyes from the sun is by wearing a billed hat such as a baseball cap, wide-brimmed sunhat, or bucket hat to keep the eyes shaded from directly overhead sunlight.

Blue light filters on glasses are also a good idea if you or your child use electronics for more than 1 hour a day. This includes computers, tablets, cell phones, and TVs.

The thing that is tricky about UV light and the eyes is that you do not necessarily feel pain from UV accumulation.

UV light causes gradual changes over time that builds up to cause a big issue. Having good prevention methods to protect your eyes against UV damage is the best way to keep your eyes strong and healthy for years to come!


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about UV light exposure and the damage it can cause.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

Understanding Soft Contact Lenses

Contact lenses eliminate the need for having to wear glasses, which can be beneficial for sports, cosmetic reasons, and the ability to see outside the limitation of a glasses lens.

In today’s world, with so many different outlets for getting contact lenses, it is more important than ever to understand why you should see your eye doctor yearly and how to properly care for your lenses.


What Does an Optometrist Consider When Prescribing Contacts?

When prescribing corrective lenses—whether they be glasses or contacts—your eye doctor takes many different parameters into consideration including: the distance between the correction and your eye (known as the vertex distance), what your primary working distance is (are you wanting to see best up close, far away, or at an intermediate distance?), the shape of your eye, the health of your eye, and many others.

Contact lenses are a little more complicated than glasses because they fit directly onto the eye and therefore need to sit just right to allow for optimal vision. Your eye doctor will take many different measurements before choosing the best lens for you—sometimes this takes multiple attempts!

Contact lens fittings can be broken down into two major categories—finding a lens that is comfortable and finding a lens that optimally corrects your vision.

At the beginning of a contact lens evaluation, the eye doctor must evaluate the health of your cornea—the very front clear structure of the eye. Your eyes need to be free of any surface disease or infection prior to wearing a contact lens.

Next, your eye doctor will take some measurements to determine what size lens would be best for your eyes, as well as mapping out the curvature of your cornea to make sure the lens is not too flat (resulting in a loose fit) or too steep (resulting in a tight fit) for your eye.

Arguably, the most important part of fitting a contact lens is ensuring that it properly corrects your vision. Since the lens sits directly on your eye, your glasses prescription will need to be converted to a contact lens prescription.

Yes, you read that right. Believe it or not, your glasses prescription and your contact lens prescription are not the same thing!

Glasses prescriptions and contact lens prescriptions can be converted interchangeably using several different complex equations. However, just because a person’s glasses prescription mathematically computes to a certain contact lens prescription does not necessarily mean that ordering the converted prescription will result in optimal vision.

Once your doctor has made all of these measurements and selected what is believed to be the “perfect” lens for your eye, they need to take a look at the lens on your eye to determine if this is actually the case.

The human eye is like a finger print—no two are the same. Therefore, your doctor will need to take your input into consideration when fitting your lens to make sure your vision is the best it can be. He or she may need to tweak a parameter or two to get your prescription exactly right.

Sometimes everything fits great and you may see great, but the lens is not comfortable. Your doctor may need to switch brands or materials to find a lens that is more comfortable to you.

Or, sometimes a lens fits great and is comfortable, but the contact lens needed for your exact prescription does not exist. Therefore, your doctor may have you try two different sets to determine which lens you see the best out of, and you may have to settle a little on not having “perfect” vision.

But wait, glasses can be made to your exact prescription, so why can’t contact lenses?

As noted above, contacts sit directly on your eye. The eye is a wet, round surface, so lenses tend to move around when blinking, looking to the right or left, up or down, etc. The main point to note here is that contact lenses have some movement whereas glasses lenses do not. This complicates things a little bit.

Contact lenses are also made in bulk by contact lens manufacturers. Since there is an infinite number of different prescriptions possible, contact lens companies have to put some limit to what they make, otherwise some lenses would be bought all the time, and others would sit on shelves for years and eventually go bad and need to get thrown away.

Therefore, unlike glasses that can be made exactly to a very specific prescription, contact lenses have to be estimated and altered to fit what is available. Your eye doctor has to make this decision each and every time your glasses prescription is adjusted.

Here’s an example patient to help explain this system:

Let’s say a person has a glasses prescription of -6.25 -3.25 X 163. After converting this prescription from glasses form to contact lens form, the “optimal” contact lens prescription would be:     -5.81 -3.11 X 163.

Prescriptions are written to the nearest quarter diopter (.00, .25, .50, or .75). For a patient with astigmatism, the available axes in contact lenses are to the nearest 10th, (i.e. X 010, X 100, X 180, X 160, X 170, etc.) Thus, this is where the doctor would need to do some educated trial and error work to find the lens that would best for this example patient.

A good place for the doctor to start would be a lens that is -5.75 -3.00 X 160. However, the doctor could also try a -6.00 -3.00 X 170, or a -5.75 -3.25 X160, or a -6.00 -3.25 X 170, or other combinations of these options.

Then, perhaps after all this calculated decision making, the doctor puts the lens on the patient’s eye and the lens rotates. Now even more calculations have to be considered to make sure the patient’s vision is corrected in the proper manner!

As you can see, it is not quite as straightforward as one might think!


Different Contact Lens Options

There are hundreds of different contact lens options in existence. In fact, every few months an entire book is published to give eye doctors the complete list of contact lenses and their available parameters.

Contact lenses are available as spherical only lenses (i.e. no astigmatism correction), or can correct for astigmatism as well. Astigmatic contact lenses are referred to as “toric” lenses.

Contact lenses that correct for astigmatism tend to be a bit more expensive, so if you have a low amount of astigmatism your eye doctor may try to adjust your prescription to be a spherical contact lens in order to help you save money. This does not work for all patients—only sometimes in those with very small amount of astigmatism (-0.25 to -0.50 diopters)

Contact lenses can also be used to change your eye color! In today’s market, essentially any color is available. Some of the most common colors are blue, green, purple, grey, or hazel.

Another of the most notable differences between contact lenses is their wear schedule. Some lenses are meant to be worn for 1 day only, others may be worn for up to a month, 3 months, etc.

It is very important that you know what your lens wear schedule is and that you discard and change out your lenses as recommended. Over-wearing your lenses can lead to infections and even permanent damage to your eyes.

Daily contact lenses tend to be a little more expensive, but are a great option for children, individuals who have allergies, those with dry eyes, or those who only like to wear lenses every now and again for special occasions.

Monthly lenses must be taken out every night and stored in a contact lens case. They tend to be a little more affordable than daily disposable lenses. It is recommended that these contacts be replaced on the same day every month (for example, the 1st of every month) to help to remember when to change lenses as to not over-wear an old lens.

There are also lenses that can be approved to sleep in, but there are not quite as many prescriptions options for these lenses as other types, as it is not recommended to sleep in contact lenses.


The Do’s and Don’t of Contact Lenses

Do NOT swim or take showers in your contact lenses. Bacteria and fungi within the water system are known to latch onto contact lenses. When these sit on your eyes all day long every day it can lead to some very serious infections.

Do replace your contact lens case every month. Bacteria like dark, warm, moist environments—like contact lens cases! You might be cleaning your lenses properly, but putting clean contacts into an old, contaminated contact lens case will only transfer the bacteria to your lenses, which will be put into your eyes, and will result in a nasty infection.

Do replace your contact lens solution each night. Letting solution sit in a case all day is asking for bacteria to move in and proliferate in the solution. Just as mentioned above, this can result in bad infections!

Do NOT sleep in your contact lenses. When we sleep, our eyes get less oxygen and dry out a little bit. When this happens, the contact lens shrinks up slightly and will tighten onto your eye—allowing even less oxygen to get to your eye. This is very dangerous!

Do replace your lenses as directed. If your lens is a monthly lens, it must be replaced after 1 month—even if you only wore it a couple of times! Lenses only stay “good” for a given amount of time. If you have a 2-week lens, it will go “bad” 2 weeks after it was removed from its foil package. Not properly disposing lenses after the time indicated by the manufacturer increaes your risk for infection.

Do discard contact lenses after they have expired. All boxes of contact lenses should be marked with an expiration date (if not, you shouldn’t be wearing that brand!). Just like medications, contact lenses expire. New contact lenses are stored in air-tight foil packets filled with a sterile solution. After the expiration date, the sterile solution has lost its effect and the lenses could be contaminated with bacteria. It is also possible that the expired lenses have lost their integrity and may no longer properly correct your prescription. Either way, it is not safe to wear expired lenses (or use expired solutions!).

Do NOT overwear your lenses. This is super important. Overwearing your lenses increases risk for infection, results in poorer optical quality, and can damage the structural integrity of the eye. One of the most common findings in contact lens over-wearers are corneal ulcers. These are very painful and can result in permanent vision loss, sometimes even blindness, if they occur on the central cornea.

Do clean your contact lenses every night. There are different types of solutions, but be sure yours has a disinfectant property to it and manually rub your lenses to ensure bacteria, debris, makeup, dirt, etc. are removed from the lenses prior to inserting them into the case for storage each night.

Do NOT fib to your eye doctor when they ask you questions about your contact lens care. Contact lenses are a wonderful tool for those who have prescriptions but do not want to be hindered by the glasses lifestyle. They are safe when used as directed. It is of utmost importance that you tell your eye doctor the truth about how you handle your contact lenses—they will not judge you, they only want what is best for your eye health. If you are not honest with your doctor, they may not be able to help you properly when problems arise. Who knows, there might be a better options to suit your lifestyle and preferred care regimen! Open conversations with your doctor are key.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about soft contact lenses.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, West University, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

Understanding Your Glasses Prescription

When you receive an eye examination, you often leave with a copy of your prescription, which includes numbers for the exact specifications of the glasses you need. These numbers include the sphere, the cylinder, and the axis.

Sphere, cylinder, and axis can also all be broken down into different categories. Read on to learn about these specifications.


Sphere is the first number on your glasses prescription

The sphere power is the first number in the prescription and specifies the overall type and amount of power in the lens. It can be positive, indicating a hyperopic or farsighted prescription, negative, indicating a myopic or nearsighted prescription, or it can be zero.

If you have a farsighted prescription, your eyes have an easier time focusing far away and need some extra power for seeing things up close.

If you have a small to moderate number, you may have gone most of your life without needing glasses and only start requiring them when the focusing system inside your eyes begins to noticeably decrease in power (presbyopia).

For a nearsighted (ie: myopic) prescription, the eyes are naturally adapted to see at near without spectacles but require diverging power to make distant objects clear.

For low myopic prescriptions, you might only want your glasses or contact lenses to drive or see a movie, while for higher prescriptions, you pretty much need your glasses for everything you do.


The cylinder power is used to correct astigmatism

The second number is the magnitude of the cylinder power, which is used to correct astigmatism. It is usually specified in minus form, but can be converted to plus form by changing the entire prescription to an equivalent format.

Astigmatism is when the eye requires different powers in different orientations to see clearly, owing to its bending light like a football rather than a soccer ball: one direction with much more curvature than the other.

This can also be imagined in that someone with uncorrected astigmatism might see the vertical part of a capital letter L as perfectly clear while the lower horizontal part of it is blurry, or vice versa in any direction.

Everyone usually has a little bit of astigmatism, but some people may have none at all. Astigmatism is also not directly related to the amount of sphere power: you can have zero sphere power and a lot of cylinder power which still requires you to wear your spectacles or contact lenses.


The axis determines where to put the astigmatism in your glasses

The axis is the final number and is written as an angle made of three digits without the extra degree sign usually put in geometric angles.

This specifies the direction of the astigmatism correction, as it is a line that can be any degree or orientation from 180 degrees (a straight line left and right) to 90 degrees (a straight line up and down) and anywhere in between these.

The axis can be specified as with the rule (close to a flat horizontal line), against the rule (close to a straight vertical line), or oblique (somewhere in between these, close to a 45 or 135 degree angle).

As we age, we tend to move from with the rule astigmatism as children to against the rule as elderly.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about your glasses prescription is made and interpreted.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

Eye Problems and Down’s Syndrome

Down’s syndrome is a condition in which chromosome 21 is duplicated, resulting in three copies rather than just two. It is associated with intellectual, developmental, and physical changes.

The eyes are one component and there are a variety of conditions that individuals diagnosed with Down syndrome may be affected by or more susceptible to. Read on to learn about some of the most common ocular findings.


Refractive Error and Glasses

This refers to an individual’s prescription in corrective eyewear such as glasses or contact lenses in order to see as clearly as possible. Patients with Down syndrome are more likely to need corrective eyewear whether for nearsightedness, farsightedness, or astigmatism.


Strabismus is a Common Feature in Down Syndrome

Strabismus refers to an eye turn that the individual may have. This could be one eye turning in and out, or both eyes turning and switching back and forth. It could also be present at all times or only at some points in the day and associated with certain activities.

An eye more often turns inward, but in either case amblyopia or lazy eye may develop. This means that because the turned eye is not being used as frequently, it will not receive as much visual stimuli and its pathways to the brain will not fully develop, leading to permanent vision reduction in that eye if the eye turn is not fixed in childhood.


Down’s Syndrome Can Cause Keratoconus

At the very front of the eye is the clear cornea, which is thinned in this condition, causing the fluid from inside the eye to push outwards. This causes the cornea to bulge outwards into a cone shape and distorts the curvature, affecting vision. This condition has been shown to be associated with eye rubbing and our optometrist will check to make sure that there are no underlying causes inducing this.


A cataract refers to the clouding of the lens within the eye, causing blurry vision or a spot in vision. If noted, our optometrist will assess to see how severe the cataract is and, if needed, refer the patient to receive surgical treatment to replace the lens. Patients with Down syndrome are at higher risk for either congenital cataracts (present at birth) or developing cataracts as they age earlier than the general population.


This is a group of disorders that refer to the death of the nerve cells at the back of the eye, which are responsible for providing peripheral vision. This is often associated with higher eye pressure but this is not the only variable.

Treatment includes eye drops, instilled everyday, to lower eye pressure or certain laser procedures that help with outflow of the fluid within the eye to lower the pressure. Individuals with Down syndrome are at higher risk for higher eye pressures and glaucoma.


This is a condition that leads to inflammation of the eyelids and the glands within them. It is often associated with a dry or burning feeling in the eyes and redness. Eyelid hygiene is an important component for this condition and it can be treated with eyelid cleaning, warm compresses, steroids, or antibiotics.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about how Down’s syndrome can affect the eyes.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

How Pregnancy Can Affect Your Eyes

In addition to the many other bodily changes taking place during pregnancy, a mom-to-be can also have changes in the eyes. These are usually transient and go back to normal after the pregnancy, but it is wise to keep a close watch on them with an eye examination if changes to vision are occurring. This article will outline some of these possible changes.

Your Glasses Prescription May Change When Pregnant

It is common for the mother to experience blurry vision due to a change in her refractive error, which can also be understood as a change in her degree of nearsightedness, farsightedness, or astigmatism as measured in her glasses prescription.

This is due to increased fluid retention throughout the body during pregnancy, including within the eye. One location for this is within the cornea, the clear front surface of the eye, causing a change in its thickness and curvature. It can also occur in the natural lens within the eye as well.

This would in turn alter the prescription needed to allow one to see clearly. This change is temporary and will likely return to normal after delivery.

It is common that our optometrist will wait six to nine weeks after delivery to update your prescription for glasses or contact lenses.


Gestational Diabetes Can Occur During Pregnancy

During pregnancy, women can develop gestational diabetes, defined as an increase of glucose in the blood during pregnancy that usually resolves after delivery.

Diabetes on its own can have detrimental effects to the health of the eyes in addition to the rest of the body if it is not well controlled for long periods of time.

Gestational diabetes usually does not get bad enough to cause these changes or symptoms, but it may exacerbate pre-existing diabetes by making blood sugar more difficult to control and regulate.

Other risk factors for diabetic retinopathy include coexisting hypertension, preeclampsia, greater severity and duration of diabetes, etc.

If you have an eye examination during your pregnancy, our eye doctor will find anything out of the ordinary if it is present and manage it accordingly or inform your other doctors of the changes.

Dry Eyes May Also Worsen

As mentioned previously, fluid can accumulate in the cornea during pregnancy, causing a decrease in sensitivity at the front of the eye.

The eyes are thus less responsive to debris or dryness in the eyes, exacerbating the effects of dry eyes due to a lack of activation of the body’s defense responses like tearing.

In addition, pregnancy and its associated hormonal changes disrupt the cells that are responsible for creating the watery fluid that makes up the tear layer.

This is key as it helps keep the eye moisturized, nourished, and healthy overall. Common symptoms of dry eye disease include a gritty, burning feeling and are often transient as well.

Mild dry eyes experienced during pregnancy can be managed with interventions like artificial tears and hot compresses, but there is a lot that can be done if the signs and symptoms are more intense and pose a risk of eye damage. 

Contact lens intolerance may also be experienced, secondary to symptoms associated with dry eye disease. For this reason, it is common to wait six to nine weeks after delivery to get fitted for contact lenses again.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about more ways pregnancy can affect your eyes.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

The Causes and Treatments of Uveitis

If you have ever visited an eye doctor for light sensitive and sore eyes, you may have been diagnosed with uveitis, prescribed various medications for treatment, and possibly undergone laboratory testing to find an underlying systemic cause, if present. You may have visited the optometrist several times during the course of your treatment. Uveitis is common and can be caused by various factors. This article explains classifications, causes, and treatment of uveitis.

The Types of Uveitis

Uveitis means inflammation of the uvea, the vascular layer of the eye that houses the iris (colored portion), ciliary body (focusing muscle and fluid producer), and choroid (full of blood vessels). This inflammation results from an immune reaction carried out by the body inside these tissues, where immune cells and other mediators cause swelling and pain.

Swelling is what causes the extreme light sensitivity commonly reported in certain types of uveitis. The iris houses the pupil, the dark hole in its center, which the iris is causing to constantly increase or decrease in size in response to light and other stimuli.

If the iris becomes inflamed and swollen, these movements will cause great pain, just like moving a broken arm would. If uveitis is located further back in the eye and is not affecting the iris, there may be minimal pain but reduced vision because of inflammatory cells affecting structures needed for seeing and causing cloudiness of the fluids inside the eye.

Uveitis is classified through several means and there are many forms. It can be taking place in just one part of the uvea, at the front, middle, or back, or all of them at once. It can happen just once or recur several times. It might last days to weeks or become chronic for months.

What Causes Uveitis to Ocurr?

Uveitis might have an autoimmune cause, where the body attacks its own cells because it recognizes them as foreign and hostile tissue. It might also be caused by infections, trauma, or, rarely, cancer.

Usually, however, a uveitic episode has no identifiable cause, and if it is not severe or does not recur, no further testing will be done to look into it. Uveitis with an unknown cause that is localized to the iris is the most common type of all.


How Do We Treat Uveitis?

Uveitis is treated by reducing the inflammatory response within the eye, as this inflammation can lead to other problems if left alone. This reduction in inflammation is usually brought about with antiinflammatory corticosteroid eye drops, dosed every hour or two to rapidly calm down the immune response.

If severe or located at the back of the uvea, oral or injected steroids might be needed. After the uveitis is nearly gone, the frequency of taking these drops will be decreased very slowly so that the uveitis does not suddenly flare up again. For this reason, it is vital to follow our eye doctor’s instructions exactly.

In addition to the steroid drops, our optometrist will likely prescribe drops to make your pupils bigger, which will stop the iris moving in response to light and reduce the amount of immune cells entering the eye. This will decrease pain, speed healing, and prevent the inflammation from damaging other parts of the eyes.

If there is a clear underlying cause of the uveitis, such as an infection in the eye, that underlying cause will be treated by our eye doctor or referred as necessary to the appropriate medical provider.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about uveitis.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

When Should My Child Get an Eye Exam?

There are many recommended health care appointments for children, and a comprehensive eye examination with an eye doctor is an important part of these. It may be confusing as to when you should bring your child for an eye examination and what can be done at each age.

This article will explore expert recommended guidelines for children’s eye examination intervals and what to expect from these appointments. In addition, the information here may be different if our optometrist finds certain conditions that they want to watch more closely.

0 – 2 Years: One Eye Examination Between 6 – 12 Months of Age

Although young and unable to do a typical eye examination, infants are able to have their eyes examined for various entities that can affect their development. After birth, hospital staff check for basic eye functioning and any noticeable diseases, like infections or the media of the eyes not being clear.

Our optometrist can check the eyes again between 6 – 12 months of age, where they are doing simple objective tests to check again for opacities in the eyes, glasses prescriptions that are outside of normal levels and can impact development, eye turns that require prompt treatment, etc.

These are short appointments that can do a great deal for a child if an issue is found.


3 – 5 Years: At Least One Eye Exam Between 3 – 5 Years of Age

As the child grows older, a more thorough eye examination is possible that can more precisely determine variables like the glasses prescription, which can be increasingly important as the child begins school.

This can be quite important as changes in the eyes that are not likely to be noticed by parents, like different refractive errors between the two eyes, can lead to amblyopia, or “lazy eye.” Amblyopia results when an eye does not have a clear image during the childhood years until age 9, causing the brain to not develop proper connections to that eye.

If the problem is corrected before age 9, proper function can develop, but if correction occurs afterwards, then there may be residual lack of vision in that eye.


6 – 18 Years: Once Before First Grade Then Annually Thereafter

As kids grow older into school, sports, and other activities, closely looking after their vision remains important. Even once we are beyond the ages where amblyopia could be a problem, optional correction of refractive error is important to optimize learning.

Treatment of errors in how the eyes focus, and how they work and move together, are also important for school and, especially, homework. Contact lenses may become important for sports and other extracurriculars like performances.

If a child is nearsighted, methods exist to reduce the rate that their prescription grows, leading to a smaller prescription overall when they finish growing.

Parents sometimes believe that if there is an issue with their child’s vision, they will be able to see it themselves, and put off routine eye care for their kids.

On the other hand, when an issue is found in an eye examination that was not previously known about, some parents blame themselves for not bringing their children in sooner. The best way to avoid this feeling, and to maintain the eye health of our kids, is to just simply get their eyes examined at proper intervals.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to set up an eye exam for your child.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.

How Do Your Eyes Work?

Have you ever wondered how your eyes actually see? It is an incredibly complex and intricate process that allows light rays to contact your eyes and transmit signals to the brain in an instant.

Beyond simply getting through all the structures of the eye and being properly focused on the back of the eye, the retina, these signals must then be propagated throughout the entire length of the brain to be processed at the very back of the brain and skull and fed into many other brain areas. Read on to learn more about this process.

Front to Back of Your Eye

Light rays first contact the transparent tear film and cornea at the front of the eye. These structures bend or refract the light for the first time as it enters the eye. It proceeds through the aqueous humour, a watery substance surrounding the colored iris, and is refracted further as it transmits through the natural lens behind the iris.

It carries on through the gel-like vitreous humor near the back of the eye before contacting photoreceptor cells near the most outer layer of the retina at the back of the eye.

These photoreceptor cells finally change these light signals into electrochemical signals that are then transmitted forward through the retina along various cell types.

At the front edge of the retina, ganglion cells transmit the signals along their nerve lengths which run from the eyes back into the middle of the brain. These are cells with very long nerves attached to them, similar to cells in the spinal cord with long lengths to transmit signals throughout the body.

In the eye, the visual signals travel along the ganglion cells as they join together in the optic nerve as they exit the eye.


From Your Eye to Your Brain

The optic nerve from each eye runs backwards from the eye and joins together with the other optic nerve near the front of the brain. At this point, some fibers cross over from each nerve to the other, meaning that some visual information from each eye is actually processed on the complete other side of the brain.

All of these nerves run further back and come to the thalamus, a sensory relay station for the entire brain. They connect with new cells that begin processing of the visual information being received, and these cells in turn pass the signal further back.

Nerve fibers then run primarily through other parts of the brain until they reach the primary visual cortex near the extreme backwards edge of the brain and skull. At this point, information from each eye is processed together for the first time.


How the Brain Processes What the Eye Sees

Depending on the type of visual information reaching the primary visual cortex, it is then sent to different areas of the brain for final processing. For example, highly detailed or color oriented information is sent to the temporal lobe of the brain for form information processing.

Spatial or motion oriented information might be sent to the parietal lobe. There is also feedback to previous points in the visual pathway like the thalamus to determine how further visual information is filtered and stored.

All of this occurs in an instant to provide us with incredible amounts of visual information about our world, and it is a process that is still under study.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about how your eyes see and work to provide information to your brain.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, and Southside Commons (Southside Place) vicinities of Houston, Texas.


Glaucoma and Eye Pressure Testing

One of the most common tests completed at the optometry office is the Non-Contact Tonometer (NCT), more often known as the “air puff test” or “glaucoma test”. To many patients, it is a mystery what this test is truly measuring but here is a quick run-down of the purpose of this test and its importance. 


Eye Pressure and Glaucoma

At your eye exam, our optometrist will often want to keep a record of your eye pressure, which is the pressure exerted in the eye from the fluids acting within/ around it. The importance of this measure is that, like other parts of the body, it is important to maintain a normal value. 

Eye pressure can have small fluctuations in the short term due to a variety of factors (i.e. body posture, exercise, eye movement, time of day) that do not have a detrimental effect on the body. The most important change that your optometrist would find significant would be a large increase or decrease in eye pressure. Low pressure could indicate leakage of internal fluid or intraocular inflammation. A pressure that is too high could indicate changes in blood pressure, disease, or injury. High IOP is also a strong risk factor for glaucoma, a disease that can decrease the size of your visual world slowly without your awareness.  


There are a variety of ways that your eye pressure can be measured: 


Indentation Tonometry

This refers to a method of indenting a small area on the cornea, the front surface of the eye. The amount of force needed to indent a specific amount of the cornea is measured, but this technique is rarely done today.


Applanation Tonometry

This method uses a force (air or physical pushing) to applanate (or flatten) a specific small area of the cornea. The force and area flattened is measured and used to determine the pressure. 

The Goldmann Applanation Tonometer, Perkins Tonometer, Tonopen and i-Care are all instruments that utilize a probe to physically push into the cornea a small depth. Our optometrist will be looking to see how much pressure needs to be exerted on the front surface in order to flatten the cornea a specific amount. Our optometrist may instill an eye drop prior to the procedure to numb the eye so you will not feel any sensation of the probe. This also does not affect the health of the eye.

The Non-Contact Computerized Tonometer is commonly used for assessing eye pressures. This is an automated test that produces a puff of air that flattens the cornea. The value that is measured is the amount of time it takes for the cornea to be flattened a specific amount, meaning that the longer it takes for the air puff to flatten the eye, the higher the internal pressure. The thickness of the cornea can affect the measurement of the eye pressure so this is often automatically accounted for after the air puff is delivered and the final IOP is calculated.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if you would like to learn more about how we use eye pressure to assess your risk of glaucoma.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services  and eye exams in the Midtown, Downtown, Museum District, and Southside Commons (Southside Place) vicinities of Houston, Texas.