Video monitors play an increasingly large part in our lives. Many folks do far more reading from the computer screen than from printed text like books and newspapers.

Are you a speed reader? If you read from a computer monitor the answer is probably “No!”

Numerous vision researchers have shown that people read text much slower on computer screens: 28 percent slower.

Here are some explanations why reading text off a monitor takes more time:

• distance between the reading material and the reader
• angle of the reading material
• character shape
• resolution
• characters per line
• lines per page
• words per page
• inter-line spacing
• actual size of characters
• inter-character spacing
• margins
• contrast between characters and background
• posture of the reader
• familiarity with the medium
• distortion in corners
• method for text advancement (scrolling vs. turning pages)

So, if you are in a big hurry you might want to print that on-screen text before reading it!

Related Topics: Tips for general good vision, Office Ergonomics

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You really don’t want to know what the acronym LASIK stands for. It is an outrageous mouthful. Its little brother LASEK is not much better. Other than an inarticulate vocabulary, there are significant differences between these two popular laser refractive surgical procedures.

Both LASIK and LASEK create a tissue flap that is elevated before laser energy is applied to the clear cornea. LASIK creates a thin slice of deeper corneal stroma. Think about an ordinary hamburger bun. Most of the time the bun is split 90% across, leaving one portion of the top of the bun hinged to the lower half. The LASIK flap is just like that. As previously discussed in this blog, the LASIK flap never heals. The LASIK flap is vulnerable to trauma, dislodgment, even separation from the cornea.

This is where LASEK differs from LASIK.

LASEK achieves similar vision correction without creating that corneal stromal flap. Instead, the LASEK flap is limited to the superficial corneal epithelial cells. Once the laser is applied the epithelial ‘carpet’ is repositioned and the cells immediately begin to heal, firmly reattaching themselves to the cornea. In 5 days or so an entire new population of cells will replace the epithelial flap like it never happened. With LASEK there is no long-term concern over a ‘lost flap’.

If you are considering refractive surgery make sure you are fully familiar with all treatment options. This includes the option to decline any surgery.

Related Topics: Eye Health, Common Vision Problems

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Every so often someone asks me about Legal Blindness.

Not too long ago a legal blindness determination was a pretty big deal because folks could qualify for an added exemption on their federal income taxes. That provision has since been eliminated.

Here are the USA standards for legal blindness:

Visual acuity of 20/200 or worse in the better eye with corrective lenses (20/200 means that a person at 20 feet from an eye chart can see what a person with normal vision could see at 200 feet)

-or-

Visual field restriction to 20 degrees diameter or less (tunnel vision) in the better eye. Folks with advanced glaucoma, retinal degenerations, and neurologic disorders usually qualify under this criterion.

Visit WebMD to learn more about vision testing.

Remember to apply the ‘better eye’ rule. If a person is totally blind (no light perception) in one eye yet can see better than 20/200 in the other eye there is no legal blindness. A person may even be missing an eye and not qualify as legally blind!

Driving vision standards require 20/40 vision or better in at least one eye. Yes, you can get a driver’s license even if you have monocular vision. You’d be surprised to learn how many one-eyed drivers there are out there on the highway!

Related Topics: Vision Problems, Eye Health

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Here’s another little secret you should know. Many excellent daytime drivers are dangerous behind the wheel after sunset! Healthy drivers included, not just folks with progressive cataracts or retinal diseases. Do you have more trouble driving in the dark? The reason may be as clear as night and day.

Daylight vision is also called photopic vision. Bright photopic light (red and yellow wavelengths) stimulates the central photoreceptors of the retina – the cells responsible for crisp, precise visual tasks like reading. Dimmer environments (blues and green wavelengths) utilize scotopic vision – peripheral photoreceptors that provide far less precise vision.

Let’s simplify things: Bright lights wipeout night vision whereas darkness prevents your critical central retina from seeing.

Some auto designers attempt to override the Laws of Nature. Although bright oncoming headlights can temporarily dazzle the driver, a stylish dashboard instrument panel may cause a bigger problem.

Sexy sportscars with bright white or bright red instrument panel illumination can actually wipeout your night vision when it’s needed most as the driver gazes upwards to look ahead in the dark. Traditional blue-green illumination was not chosen by accident. Large blue-green numbers and indicators can be read without jeopardizing critical central vision.

Did you know that many nearsighted myopes become more myopic in the dark? We call this ‘night myopia’. Night vision is also affected by normal pupillary dilation that occurs in the dark. Big pupils can induce a variety of optical aberrations. Drivers adapt differently differently to low-light levels, so the dashboard light intensity is adjustable. Thinking about buying a car or truck? Schedule an evening test drive to make sure the vehicle offers optimal night viewing.

Related Links:Vision Problems in Aging Adults, Understanding Vision Problems

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1. The medical term for lazy eye is Amblyopia.

2. Amblyopia is a healthy eye that does not see well. Intrinsic eye disorders (cataract, corneal scarring, etc.) can worsen amblyopia.

3. Amblyopia always begins in childhood, usually before age 3.

4. Don’t blame the eyes! The brain decides whether or not an eye becomes amblyopic. Remember, the eye is healthy!

5. When a conflict exists the brain is forced to make a choice between processing visual information from the better of the two eyes.

6. Visual conflicts include crooked eyes (strabismus), blockage of the normal visual pathway (as in a dense infantile cataract), or a marked difference in the refractive power of the two eyes (as an example: one eye nearsighted and the other farsighted).

7. A child can have a densely amblyopic eye and not complain.

8. Visual penalization of the better eye is the recommended treatment for lazy eye. Methods include patching the better eye or administration of atropine ointment to blur the better eye so as to force the lazy eye back to work. A specific treatment schedule is customized for each child’s needs.

9. Parents of amblyopic children need to be very aggressive towards enforcing amblyopia treatment. The eye doctor educates and encourages. It is a daily parental responsibility that cannot be neglected. The earlier treatment is started the better the chances for good visual recovery.

10. Beyond age 7 (and certainly after age 11) the chances of significant reversal of lazy eye are very poor. By then the brain’s circuitry has reached maturation. No matter how many times treatment fails, start again and commit to do the best job possible. A lifetime of good eyesight hangs in the balance!

Related Topics: Never Too Late to Treat Kids with Lazy Eye, Vision Exams for Infants and Children

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Here’s a helpful website that may help you explain your visual symptoms to your eye doctor.

Click here to understand the difference between blur, glare, and ghosting. Many other visual phenomena are demonstrated.

Visitors can adjust the severity of each aberration from mild to wild. This interactive website also exhibits what patients are likely to experience with different eye disorders.

One unexpected feature of this website is a prominent notice on the home page offering to provide (sell) simulations for courtroom use. Hey, everybody has a right to make a living!

Related Topics: WebMD Eye Health Center

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Every so often somebody asks me about marijuana. No, they don’t want to sell me some weed, rather, they want to know if I can prescribe them some!

The practice of ophthalmology and controlled substances go way back. Did you know that the first legitimate medical use of cocaine occurred in 1885? Cocaine drops were administered for local anesthesia during eye surgery. Eye specialists also used topical cocaine eyedrops to establish (or refute) the diagnosis of Horner’s Syndrome – an interruption of sympathetic nerve fibers to the eye.

Many glaucoma medications work by reducing the production of eye fluid (aqueous) and/or accelerating its drainage from the eye. For over a decade researchers have known that the active ingredient in marijuana (tetrahydrocannabinol-THC) can lead to a pressure reduction in the eye.

So, dude, should all glaucoma patients start lightin’ up?

Scientists want to create chemical analogs, drugs that simulate THC’s chemical activity without the psychoactive high. Best data to date shows that THC will reduce the intraocular pressure, but not as much (nor as consistently) as other proven medications. Volunteer patients using topical THC eyedrops do not get high, horny, or hungry.

There already exist many more consistently effective eyedrops that are proven to lower pressure and reduce the risk of glaucoma damage. Given that doctors want to offer their patients the best treatment, there is no moral justification to prescribe an inferior drug.

Related Topics: Supreme Court Rules Against Medicinal Marijuana, Glaucoma

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Remember 35mm cameras? Most of them are collecting dust with the popularity of easy-to-use digital cameras. Anyway, about the 35mm camera…if you removed the lens from the camera body you were unable to take clear photos. And so it is with cataract surgery. By removing the cloudy lens through cataract surgery the eye immediately loses about 18 diopters of focusing power, roughly one-third of the eye’s total focusing power.

For the past 20 years eye surgeons have relied on an artificial intraocular lens (IOL) implant to correct for the loss of focusing power. IOLs are available in a range of optical powers to match the needs of individual patients, however, until recently, IOLs offered one optical correction: distance or near. Most IOL recipients still wore glasses after their surgery to help with reading.

Now things are changing.

Multifocal IOLs are now available. The FDA has determined that they are safe and effective. The leading multifocal IOLs have pleasing names like Crystalens, ReSTOR, and ARRAY.

Unfortunately, Medicare has not kept up with change.

Although there are a few exceptions, most patients receiving a multifocal IOL will incur a huge out-of-pocket expense, typically exceeding $2000 per eye. Medicare and most private insurers only reimburse for the standard, less-expensive monofocal IOL.

If you are considering cataract surgery make sure you clearly understand exactly which charges you will be expected to pay out of your own pocket. Many seniors don’t have $2000 to spend for medical devices that are totally elective. Speak with your surgeon to determine if your situation qualifies for multifocal IOL reimbursement.

Related Topics: Should I Have Cataract Surgery?, Vision Problems in Aging Adults

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Everybody has heard about Saw Palmetto, right? It’s a natural substance touted to prevent prostate enlargement in men (abbreviated BPH). Most men over 60 have some form of BPH and the urinary symptoms that accompany the condition.

Just this week a large study published in the New England Journal of Medicine discredited any medicinal value of Saw Palmetto. (Full Report)

This product made it into the mainstream marketplace without rigorous proof of any genuine benefits. Most clinical studies were short term with few participants. Oftentimes there was no placebo or inadequate ‘blinding’ to keep the study objective. There remains no concensus regarding how the ‘active ingredient’ in Saw Palmetto works!

So you ask, why is the WebMD ‘Eye Guy’talking about prostate and palmetto?

Many folks consume a variety of vitamins, nutrients, herbals, botanicals, and antioxidants because they believe these supplements will prevent aging changes to the eyes and preserve clear vision. Will there soon be more stories to dispute the benefits of Vitamins A, C, E as well as zinc?

Fortunately, eye care will not be similarly blindsided.

A huge, expensive, well-designed, objective and controlled clinical study has been underway for many years. It is sponsored by the National Eye Institute and it is called AREDS (Age-Related Eye Disease Study).

AREDS studied thousands of people and the healthy effects of vitamins and zinc in the prevention of Macular Degeneration. Review the findings here. NEI also reports that Lutein has received intense scrutiny and has been found to be beneficial to preserving eyesight. NEI is organizing more clinical studies to verify the efficacy of other supplements.

Related Topics: Food-aceuticals: Drink – and Eat – to Your Health, , Nutrition Advice You Can Take to Heart

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One of the most mystical terms used in ophthalmology is astigmatism.
Well, what is it?

Uncorrected astigmatism is a frequent reason why people cannot see clearly.
Okay, but what is it?

Astigmatism keeps many people from wearing soft contact lenses.
Enough already! What is astigmatism?!?

First things first. Let’s start with a perfect uncorrected 20/20 eye. This eye clearly “sees” an object because the eye is precisely focusing light rays that come from the object. Follow me so far?

The outer surface of the normal, healthy, clear cornea is smooth, even, and round. We call the surface spherical because its shape is just like half of a sphere – like half a racquetball. We’ve previously mentioned that two-thirds of the eye’s focusing power occurs along the front surface of the cornea. Curvature of the cornea contributes greatly to that focusing power.

Light rays bombard the cornea from every conceivable angle: straight down the middle (axial), horizontal, vertical, and every oblique angle in-between. Since the curvature of the spherical cornea is uniform and identical along every conceivable meridian (any line that passes through the center of the cornea and connects opposite points at the edge of the cornea, like 0 and 180 degrees – better known as 3 and 9 o’clock), every ray is equally focused.

What happens when it is not?

At long last. Astigmatism loosely means “not spherical”*. Eyes (corneas) with astigmatism have an uneven curvature. Let’s stick with the ball analogy. Imagine cutting a football in half tip-to-tip along its long axis. Right away you can appreciate how the curvature of this ‘hemi-football’ is flatter along the longer meridian and steeper along its shorter meridian. For all nonspherical surfaces there is a steepest meridian and a flattest meridian. The difference in curvature between these two meridians creates cylindrical error, the quantity of astigmatism.

Want to easily demonstrate some astigmatism on yourself? Look at your reflection in a round silver soup spoon and compare what you see with an oval teaspoon.

Don’t be frustrated if you had trouble absorbing all of this information. Next time we’re together we’ll apply some of these optics to everyday real-world vision correction.

* Here’s the fine print: The etymology for astigmatism more accurately means “without a point”. Spherical surfaces focus the image at a single point. Uneven curvature prevents that from happening. Less frequently, the crystalline lens can also generate some astigmatism.

Related Topics: Eye on New Vision Procedures , Eye Cell Implants Help Parkinson’s

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