There’s been quite a bit of talk about increased blue light exposure in our society and it’s possible harmful effects to the human eye. Today I’d like to brief you on the latest information.

The short answer is YES. As it turns out, blue light has been shown to increase the incidence of macular degeneration and contribute to its progression. It has also been shown to decrease visual performance and affect our circadian rhythm and sleep cycles.

Why is this happening? Haven’t humans always been exposed to blue light? Well, are paying more attention to blue light because of our increased exposure to CFL light bulbs and computer devices as technology is rapidly advancing. These devices emit the same proportion of blue light as the sun, and we are continuously bombarding ourselves with them from morning till bedtime. Before all this technology, our peak blue light exposure from the sun was from about 10AM to 2PM, and that was it!

Why does blue light harm our eyes? So we’ve been harping on protecting your eyes from UV with proper sunglasses for decades now, so I will start there. UV light is not visible and has a wavelength range from 100 to 380 nm. As wavelengths go, the shorter the wavelength, the higher the energy. Therefore UV light has a very short wavelength and carries a much higher energy yield which damages the tissues of the body. The natural lens inside our eyes blocks nearly 100% of UV light from hitting the retina. This is a good thing as far as protecting the retina. However, this is why we develop cataracts (cloudy lenses) faster if we over-expose our eyes to UV. In addition, the lens does not block blue light from hitting the retina.

Blue light is the shortest wavelength of light that is visible, so it carries the highest energy of the light we can see. It has a wavelength range from about 380nm to 495nm. Now, not all of this blue light spectrum is harmful. In fact, we need exposure to the blue-turquoise (465-495nm) range to help our contrast sensitivity, our pupil reflex, and melatonin release for proper sleep patterns.

The shorter wavelength blue-violet light range of 415 to 455nm has been shown to be the most harmful to our retina in causing cell death. Our increasing exposure to blue light will undoubtedly create a cumulative detriment the health of our eyes.

How can we protect our eyes from the ever-increasing amount of blue light in our environment? To begin, if you or your child has poor sleep patterns, please refrain from any LCD or devices at close range 3 hours prior to bedtime. As far as filtering blue light, there are new options in ophthalmic lenses that can help. For instance, we have newer anti-reflective coating options like Crizal Prevenica that will block roughly 20% of harmful blue-violet light. In addition, there is a company that makes a lens material called BluTech ( This lens material contains the optical pigment density filters that block closer to 100% of the harmful blue-violet wavelengths. It has a slight yellow tint to it, but you will still perceive most blue colors just like normal.

These lenses are also a good option for light-sensitive individuals or for those who experience eye fatigue after prolonged computer use. Occasionally I will prescribe “anti-fatigue” glasses that are powered in a way that relaxes the eyes works them together more smoothly while at a computer. Add in the BluTech technology and you have one comfortable pair or office glasses!

Thanks for reading, and protect those eyes!

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There are a few different types of amblyopia (commonly referred to as lazy eye). You are probably envisioning someone you know that has a crossed or turned out eye, and it makes you uncomfortable because you’re not sure which eye they’re looking at you with. Don’t worry, even eye doctores occasionally do a double take to make sure they are addressing the correct eye during conversation…

A more common form of amblyopia is the refractive type. This occurs when a child is born with a glasses prescription that is much stronger in one eye than the other. As the child’s vision developes, the brain wires up the clearer eye and ignores the worse eye. We call this phenomenon “suppression” of the amblyopic eye.

When an eye is suppressed during development, the vision in that eye is still blurred even when the correct prescription lens is first placed in front of it. Depth perception (also known as stereopsis or binocular vision) is not developed properly either.

Occasionally the child’s ambyopic eye and stereopsis will develop correctly simply by fitting them with a current glasses prescription. Often though, this needs to be coupled with patching of the good eye at least 2 hours per day. Eye-patching will force the brain to develop the neurological pathway needed to get the clear visual signal from suppressed eye to the back of the brain where the occipital lobe is located.

Important note: In general, the brain is mostly developed by age 9. Although it can learn new things after this age, it is not nearly as “plastic” to where it can develop a neuronal pathway from the eye to the occipital lobe. Therefore, it is extremely important to have an eye care professional perform a comprehensive examination at a much younger age. Sometimes a eye may be only mildly amblyopic, but you do not want to lose the opportunity to correct it while you can.

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And YES – I know you hate it, but the air puff test is still very important!

I always tell my glaucoma-suspect patients to imagine the optic nerve as a bundle of a million nerve fibers connecting the eye to the brain. Now imagine if you were to lose those nerve fibers one by one slowly over the years until you go blind. That is essentially the typical process of glaucoma. It is usually caused by high internal fluid pressure inside the eye, but it often occurs in patients with normal pressures.

There are several types of glaucoma and low (or normal) -tension glaucoma makes up about 30% of the glaucoma patients in our practie. The exact cause is unknown but it is probably due do poor oxygen delivery to the optic nerve. This can be caused by type 2 diabetes, low blood pressure, chronic migraines etc.

You may be wondering; how do eye doctors detect glaucoma if someone’s pressures read normal? A thorough eye exam will typically reveal an optic nerve that has a thin appearance. Then, I consider a patients other risk factors such as family histroy, systemic desease, age, race etc. For example, 60 year-old female migraine sufferers are classic low-tension glaucoma suspects.

In other cases, a patient may have low eye pressure during the daytime, and a very high pressure at night. Most peoples’ eye pressures are highest at night. Lets say someone has a VERY high pressure at night. That day-to-night fluctuation by itself could eventually damage the optic nerve. Now, lets add another factor in; the patient takes their blood pressure medications before bedtime. Now we have low blood pressure at night, and therefore low oxygen perfusion to the optic nerve. Couple that with high internal eye pressure physically exerting force on the nerve, and voila! You have normal pressures at the eye doctor’s office by day, glaucoma damage by night.

Normal-Tension Glaucoma can be at times difficult to diagnose. However, with proper testing, the disease can be detected, treated and stabilized just the same as high pressure glaucoma. Whatever your age, be sure to have your comprehensive eye examinations on a regular basis.

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Recently I had a patient return for her yearly contact lens exam (6 months late). I had fit her in colored contacts at her last exam. She reported to me that she falls asleep in her contacts very often, and that her eyes were very dry.

Upon examination I discovered that her lenses were fitting very tightly, showing no movement whatsoever upon blinking. Her visual acuity was decreased in both eyes. I also noticed that the lens seemed be different than what I prescribed 18 months earlier.

I questioned her about this and she stated to me that she was trying a different brand that she ordered online. After removing her contact lenses I evaluated her corneas and discovered dense scars on her corneas.

Luckily she can still achieve 20/20 vision now that I ordered her to discontinue wearing contact lenses over the past few weeks. There will be scaring on her corneas forever, but not in her line of sight.

This is a good example of why we should not abuse the privilege of wearing contact lenses, and why online contact lens ordering is unpopular with eye doctors. There are some lenses that can be worn overnight – as long as they are properly fit by your eye doctor. FYI – THERE IS NO COLORED OR TINTED CONTACT LENS ON THE MARKET THAT SHOULD BE WORN OVERNIGHT!

Online contact lens retailers are required by law to verify a prescription by checking with that doctors office. They usually send us a fax and if no reply is received within 8 business hours, the order is automatically shipped – assuming the Rx is valid.

In case of this patient, she wanted to try a new contact lens color – and the Rx verificatoin fax was received while we were closed. The result was an improperly fit lens and severe corneal scaring. Had the scar been 1mm higher on her cornea she would have suffered severe vision loss. Had she returned to us in 1 year for her exam I may have been able to prevent this from happening.

So please, if you wear contact lenses, have them evaulated yearly. Talk to your doctor if you sleep in your lenses often , and they will get you set up with a safe brand. And please, do not try to order something online that was not properly prescribed for you.

Brad Kaster O.D.

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