UV and You

On a recent trip to SoHo, I witnessed sunglasses adorned with "100% UV protection" stickers sold for as low as $1.00. And would you believe it, they were also Coco Chanels, Guccis, and Dolce and Gabanas! OK, so the manufacturer labels may have been fictitious, but what about the Ultraviolet (UV) protection? Chances are these glasses really do filter UV rays, though the only way to be certain is to have them measured by an optician. Multiple studies have demonstrated that the price of sunglasses has little bearing on their ability to filter UV light, so don't rush to dismiss the bargain glasses.

UV filtration standards are assigned by continental jurisdiction: Australian, European, or American. The US standard is the lowest (land of the free!) We allow 1% UV transmittance of wavelengths up to 400 nm (Hence the UV 400 stickers), while the Europeans are a little more selective in awarding wavelengths VISAs (up to 380 nm). Our mates down-under fall somewhere in between. There is no enforcement of these standards in the US, so the presence of UV stickers may be misleading.

But what’s so bad about a little sunny delight for the eyes anyway?

UV rays may inflict damage in several layers of the eye cake. Too much UV exposure can cause squamous or basal cell carcinomas to crop up on the eyelids. Likewise, squamous cell carcinoma may develop on the skin of the eyeball (the conjunctiva) and spread onto the cornea. More commonly, chronic UV exposure may result in a growth called “pterygium” to spread over the cornea. Pterygium is Greek for “little wing,” which describes perfectly the shape of this flightless lesion. If these growths are detained on conjunctival territory, they look like little stumps and are fondly named “pinguecula.” Folks who spend their life outdoors are more prone to these conditions: farmers, sailors, the crew of Jersey Shore.

Intense UV exposure may also lead to corneal inflammation (keratitis) and cause a sterile conjunctivitis when the surface cells (epithilium) die off. Welders and DNA lab-workers or those who seek “perma-tans” in their friendly neighborhood spas also fall victim to this ultraviolet infliction.

Sun gazers (usually these folks are high on something, and it's not vitamin D) can damage their retinas with solar rays. The retinas of sober individuals who stare at solar eclipses may also be burned by the sun. The diagnosis “solar retinopathy” is not an eco-friendly energy solution, but rather a transient loss of central vision for one to twelve months!

Finally, some believe excess sun may play a role in the development of cataracts and macular degeneration, though far stronger genetic factors contribute to these entities.

In conclusion, the benefits of sun protection cannot be overstated. Thanks to role models such as Bon Jovi, Paris Hilton, and David Hasselhoff, these accessories are also considered really cool.  Right?

Color me Bad

I once asked a colleague of mine whether he was color blind, and he replied with great agitation that he was not color blind, but color deficient!  Defensive, are we?  Color perception is one of the great wonders of the human eye. Our retinas house a high-tech built-in imaging system that consists of 90 million rod and 4.5 million cone sensors.  Rods are in charge of night vision, peripheral vision, and large movements.  The cones, being more refined, take care of daylight vision, fine details, central vision, and color.

As you may remember from your physics days of yore, color is a wavelength of light that is reflected by an object.  And, like old technicolor televisions, we have three cone types capable of perceiving three color wavelengths: green, blue, and red.  This makes us trichromats.  Allegedly, there are individuals who have a fourth cone type, and they are called tetrachromats. (Although a tetrachromatic retina is exceedingly rare amongst humans, people immediately think they are tetras when they first read about it.)  Because the human lens filters out most ultraviolet light, we do not perceive it, but there have been reports of aphakic patients (patients without a lens) who see into the ultraviolet spectrum (!)

Many different forms of hereditary color deficiency and color blindness exist, and they usually have to do with either complete absence of one (or more) type of cone, or a reduced sensitivity of one cone type.  The most common type of color deficiency (red-green) is due to a reduced sensitivity of the green cones in affected individuals.  Because most of the genes that code for vision are on the X chromosome, males are much more likely to suffer from color deficiency and females are much more likely to be tetrachromats.  Seven to ten percent of males are color deficient (which explains why some dress the way they do).  Other reasons for deficient color perception are acquired causes related to optic nerve and retinal health.

But, it's not all bad news for color deficient folks.  Studies conducted by the military have shown an evolutionary advantage to color deficiency: the ability to see through camouflage.  Was GI Joe color deficient?  Maybe so.

Eye Contact: taking care of your contact lenses

As a cornea specialist, I see a fair amount of corneal ulcers, contact lens overwear, and allergic reactions to contact lenses or solutions.  I have always believed first time contact lens wearers should take an exam, much like the driver's ed test.  If only patients would obtain a license to wear contacts, corneas around the world would be healthier, and eyeballs will breath a sigh of relief.  But the FDA has so far ignored my fringe opinions on the subject.  So, here are my top ten tips for good contact lens care:

10. Never sleep with your contacts in.  No ifs ands or buts!
9. Always clean your lenses at night.  The best types of cleaning solutions to minimize allergic reactions and infections are Clear Care or Aeosept.  These solutions are hydrogen peroxide based -- this acid kills most living organisms and bubbles out into water by morning (virtually preservative-free). Please read the instructions carefully before using the product!  You cannot put the solution directly in your eye before it is neutralized into water.
8. Limit contact lens wear to 8 hours a day or fewer.
7. If you are too lazy to clean your contacts at night, consider daily wear contacts that you may carelessly fling out of your eyes at night.
6. For those whose corneas show signs of choking out (we call it "neovascularization" or "neo" for you Matrix fans), I recommend lenses with high oxygen diffusion such as O2 Optix from Ciba.
5. For the dry eye folks who have a hard time tolerating contacts, try Acuvue Oasis, which will help keep the eyes better lubricated.
4.  Use preservative-free artificial tears if you are wearing contacts and need a "spot" of lubrication.
3. Never wear contacts that were not fitted for your eyes by an ophthalmologist or optometrist, because damage can occur.
2.  Do not use expired lenses, solutions, or old cases.  Would you drink expired milk?  Why do this to your eyes?
1.  If your contacts irritate your eyes, take them out and see your eye doc!

It's a sign of the seasons: itchy eyes

Cherry blossoms are budding in DC, Central Park is bespeckled with frosty pink and white patches, and tulips are sprouting along Boston’s Comm. Ave. In other words, tissue boxes are making cameos, children are a-sneezing, and our friends and loved ones are rubbing their eyes out. Allergy season is hitting the East Coast full force, and those of us who suffer from the affliction are crying for help.

Signs of ocular allergy include itching, tearing, and red eyes. Interestingly, systemic medicines prescribed for seasonal allergies (such as Claritin D, Allegra, or Benadryl) do not improve ocular allergy symptoms. Usually, topical drops such as Pataday, Elestat, or Bepreve are necessary to curb the irresistible urge to rub. These drops combine anti-histamine action with mast-cell stabilization (mast cells are like time-bombs full of itchy substances).  Mild steroid drops like Alrex may help as well.  If you are uninsured (not for long!), there are a few effective over-the-counter drops too, such as Zaditor or Alway.  The main thing to try and avoid is eye rubbing.  If your eyes are itchy and you rub them, you enable their bad behavior!  The more you rub, the more mast-cells are goaded to release their allergenic explosives.  Putting one of these drops in your eyes is a far better (and more pacifist) way to control your symptoms.  

So, stop and smell the flowers?  Maybe.  Just make sure you are properly equipped.

3-D Films: behind the scenes

Unless you live under a rock or somewhere on Pluto, you have probably seen or at least heard of the film Avatar by now. Perhaps you also watched the Clash of the Titans, or Tim Burton's Alice in Wonderland. Curious about these eye-popping 3-dimensional cinematographic experiences, you may have wondered, how'dey do it?

Films produced for your 3-dimensional watching pleasure depend on special projectors and eye-gear. In everyday life, you are able to perceive the world around you in three dimensions (provided you have fairly good vision in both eyes). This is because your eyes are spaced approximately 6 cm apart, each conveying to your brain a slightly different perspective image from its position on the head. Your brain (nerd) takes these two slightly dissimilar images and fuses them into one three-dimensional picture.

When you watch a conventional film, your brain is unable to appreciate depth of field, because the two eyes send fairly similar information to the brain. However, if the movie projector were to display two slightly dissimilar images to each eye, your brain would be fooled into thinking the film is 3-dimensional. With the RealD technology used in creating Avatar, two slightly dissimilar images are produced as the film's projected light-rays are polarized (oriented) in two opposing directions. Normally light waves bounce randomly in all different ways, but if subjected to a polarizing filter, they will follow in the ordained direction of their filter (clockwise and counterclockwise, in this instance). The opposing polarizing filters on the Avatar projector actually alternate the image light-rays from clockwise to counterclockwise at a rate of 144 times per second! If you were to see both projected images at once, however, the picture would appear fuzzy, not 3-dimensional; so for the low price of $16.50 you are also provided with a pair of 3-D glasses. The right and left lenses on these glasses also contain circular polarizing filters: one oriented clock-wise, the other counter-clockwise. This way, while one eye filters out the clockwise rays the other receives the counterclockwise ones. So each eye sees a slightly different image. These two images are dispatched to your brain, which computes the information into a 3-dimensional picture.  Et, voilá.

Interestingly enough, we use a similar technique in everyday pediatric ophthalmology. With linear polarizing filter glasses (one lens filters only vertical image rays the other only horizontal image rays), children are asked to look at a tablet containing a fly, circles and animals. These images are preprinted on a material that allows light rays to be projected vertically alongside a shadow image that projects horizontally. If the child identifies the correct “3 dimensional” images in the tablet (Titmus test), we know s/he has good binocular vision from both eyes. The test serves as a great screening exam for amblyopia (a condition in which a child does not develop good vision in one or both eyes). It can also be used to assess depth perception in adults.

So, now you know how they work, prepare for an onslaught of 3-D films!

Transplant Surgery

Some folks do not know what an "ophthalmologist" really does. So whenever people mistake me for an optician at Lens Crafters, I proudly announce that I perform transplant surgery.  Put that in your pipe and smoke it, I chuckle to myself.  Because of their unique position in the body, pristine islands in a sea of blood vessels, corneas receive an immunity necklace.  In professional jargon, they are "immunologically privileged", i.e. white blood cells cannot easily reach a corneal transplant and cause its rejection, because the highways to the cornea are unpaved. Therefore, corneas are the only transplanted organs that do not require systemic immunosuppression or blood-typing.  

Forget "I see dead people."  Recipients of corneal transplants see thanks to dead people!  Cadaveric corneas are harvested from deceased individuals who checked the appropriate box at the DMV.  They are then rushed to an institution on Wall Street called, you got it, an eye bank.  In Optisol storage media, they can be stored for approximately seven days before they are delivered to an operating room.  Meanwhile, they undergo rigorous testing to ensure quality and good health.  There are several eye banks in the country and the world, but the oldest one was established right here in New York.  It was founded by Dr. R. Townley Paton, who pioneered and then performed the first corneal transplant in 1905.  He did not establish The Eye Bank for Sight Restoration until 1944, when he was able to procure proper news-press and funding for his unique project.  Dr. Paton's first donor corneas were obtained from deceased inmates on death row at the nearby Sing-Sing prison and later expanded to deceased law-abiding citizens.  As the New York Eye Bank continued to grow and append surgeons, it sprouted 25 branches throughout the country.  Nowadays, 33,000 corneal transplants are performed in the United States each year.

Who needs corneal transplants?  The most common reasons for a transplant are a pointy cornea condition called keratotconus and a swollen cornea condition called bullous keratopathy.  Corneal scars due to trauma, infection or ulcers are also a hot commodity.  Finally, there are congenital conditions that cause the translucent corneal window to opacify.  These too, qualify for transplant surgery.

The procedure of transplantation is relatively simple: (1) cut out a circle of recipient cornea (2) replace missing circle with cookie-cut donor cornea (3) suture new cornea into its new 'hood and wait for it to jive.  The suture material consists of nylon thread, a fraction of a hair-width (it is only visible under a high-power microscope).  Full visual recovery takes about a year, and the cornea usually lasts approximately 15 years before it fails.  In the meanwhile, topical steroid drops are applied to prevent white-cells from reaching the graft.  There is only a 10% rejection rate in most cases, which, if caught in time, can be reversed.  Several years ago, exciting new technology emerged that allowed for partial corneal transplantation in a procedure called Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK).  This surgery forgoes the need for sutures, promises an even lower rejection rate than conventional transplants, and allows for visual recovery within three months!  It is only appropriate for folks with corneal swelling, though.  To learn more about the fascinating history of the New York Eye Bank, check out their website: http://www.eyedonation.org/