Mystery Diagnosis: Optic Disc Drusen

The optic nerve is a bundle of 1.2 million nerve axons, and is the structure that transmits the visual signal detected by the rods and cones of the retina to the visual cortex in the brain.

This is what a normal optic nerve looks like. You can clearly see where it stops and starts, and it has a healthy pink/yellow hue to it.

  A healthy optic nerve. Image courtesy of  eyerounds.org .

A healthy optic nerve. Image courtesy of eyerounds.org.

The optic nerve can be damaged or abnormal in many ways. In glaucoma, the central, whiter part of the nerve (the "cup") becomes larger as progressive damage occurs due to pressure too high within the eye. The optic nerve can turn pale, meaning it loses its natural pink/yellow hue, because of tumors, nutritional problems, or after lack of blood flow to the nerve, just to name a few.

Another way in which the optic nerve can appear abnormal is due to swelling, known as optic disc edema. When the nerve is edematous, the normally crisp edges of the nerve head become blurred and indistinct, almost like someone smudged them with their finger. Take a look at the optic nerve pictured below. There is one large hemorrhage at the 8:30 position, and a number of smaller ones as well. Compare the edges of this nerve with those above; notice how here it's harder to tell where the nerve "starts and stops," so to speak. Finally, examine the blood vessels as they course just outside the optic nerve. Particularly with the two vessels at 4:30 and 5:30, there is an area where it is hard to see the vessels. This is a sign that this nerve is truly edematous, or swollen.

  Optic disc edema. Image courtesy of  eyerounds.org .

Optic disc edema. Image courtesy of eyerounds.org.

When optic disc edema is due to raised pressure inside the head -- because the nerve is part of the central nervous system, it is bathed with cerebrospinal fluid, and can swell when the pressure inside the skull is too high -- it is known as papilledema. If this is the case, an MRI and MRV (magnetic resonance venogram) should be performed to determine the cause, often followed by a lumbar puncture.

Sometimes, however, the nerve can appear swollen, when in fact it actually isn't. The most common reason? Optic disc drusen. Drusen (from the German word for stone) are small concretions of protein and calcium salts within the optic nerve that may cause the nerve to appear swollen, and are found in 1-2% of the population. While rarely, disc drusen may cause small areas of visual field loss, or even more rarely, sudden vision loss, the vast majority of patients with this condition have zero symptoms.

The diagnosis of optic disc drusen is made with the help of a dilated eye exam and additional imaging, most often an ocular ultrasound. While the pseudo-edema look caused by disc drusen is often present in young children, the drusen themselves often aren't visible to the eye doctor until later in the patient's life. However, many otherwise-invisible drusen can be seen on ultrasound, where calcium within the concretions will show brightly.

In this image below, from a young patient with no symptoms, the black arrow shows a part of the nerve where there is no appearance of swelling. It is easy to see the edge of the nerve. The white arrow shows an indistinct disc margin. The blue arrow shows how it's easy to see these vessels as they enter and exit the nerve (contrast this with the image above), which is a reassuring finding. Encircled in red in the ultrasound images are the disc drusen, which appear as bright white spots.

Thanks to a careful history and examination and the use of a simple ultrasound, which can be done quickly and non-invasively in the eye clinic, the diagnosis of pseudo-edema due to optic disc drusen can be made, and in most cases, further, invasive testing (MRI, spinal tap) can be avoided.

opticdiscdrusen

Thank you to The University of Iowa and EyeRounds.org for permission to reproduce this copyrighted material.

Stars' Eyes: Abraham Lincoln

Widely regarded as perhaps the greatest of the Presidents of the United States of America, Abraham Lincoln held office during the Civil War, from 1861 until his assassination in 1865. Many aspects of Lincoln's life -- from his humble beginnings in Kentucky and Indiana, to his practicing law before becoming a leader in the nascent Republican party -- are well known. But did you know that he also had strabismus?

lincoln strabismus

Look carefully at this image. Notice how his left eye appears to be looking higher than his right. This is suggestive of a vertical strabismus (eye misalignment), as are the reports that Lincoln suffered from double vision and that his left eye would "roll upward when he was excited or tired."

The intermittent nature of this symptom is consistent with either an intermittent left hypertropia or a dissociated vertical deviation. Both of these conditions are easily diagnosed by a pediatric ophthalmologist, and treatment options may include prisms glasses or corrective surgery.

Because of his very tall, thin stature, many historians have suggested that Lincoln had a condition called Marfan syndrome, a genetic disease which affects the connective tissues in the body. People with Marfan syndrome are typically very tall, thin, and "loose jointed." They are more likely to have strabismus, and may also develop early cataracts, glaucoma, corneal problems, or retinal detachments.

Note: Special credit to my partner, Dr. Jeffrey Colburn MD, of the Spokane Eye Clinic, for making me aware of President Lincoln's strabismus.

PEDIG Meeting -- Tampa, Florida

This week, I've had the opportunity to attend the annual meeting of the Pediatric Eye Disease Investigator Group (PEDIG) in Tampa, Florida. PEDIG, founded in 1997 and funded by the National Eye Institute/National Institutes of Health, is a collaborative network dedicated to supporting research in amblyopia, strabismus, and other childhood eye disorders.

PEDIG

As part of my practice at the Spokane Eye Clinic, my partner Dr. Colburn and I are honored to participate in several PEDIG research studies. This research allows us to help define and develop new and cutting-edge treatments for children with eye problems.

Prior PEDIG research has helped us learn these important findings, among many others:

  • Infantile esotropia: Constant, large esotropia (eye crossing) in infants is exceedingly unlikely to go away on its own, and very likely to require corrective surgery.
  • Treatment of amblyopia: For moderate amblyopia, with vision in the 20/40 to 20/100 range, part time patching and atropine eye drops are equally effective treatments.
  • Nasolacrimal duct obstruction: For infants between 6 and 10 months old who have tear duct obstruction, there is a 66% chance the symptoms resolve without surgery over the next 6 months.

To see the complete list of over 100 PEDIG research articles published in peer-reviewed scientific journals, click here.

Although I can't discuss the actual research data I've seen at this meeting -- stay tuned, as it will be published in scientific journals in the near future! -- I can say that there are a number of exciting potential advances in treatment of retinopathy of prematurity, amblyopia ("lazy eye"), and strabismus (eye misalignment).

One wonderful thing about PEDIG is that it allows eye doctors in private practice, like myself, to participate in nationwide research studies along with physicians in university settings. I am grateful for the chance to help both current patients and future generations by learning more about childhood eye disease and how best to treat it. I've enjoyed the chance to reconnect with old colleagues and make friends with a lot of highly intelligent, motivated people, all of whom want the same thing I do: to figure out how best to take care of our little patients and their eyes.

Guest on "Straight From the Cutter's Mouth" Podcast

I had the great honor of being invited on the "Straight From the Cutter's Mouth" podcast this past week. The host, Dr. Jayanth Sridhar MD, is a friend and colleague whom I met while we were both interviewing for ophthalmology residency positions.

We talked, among other things, about taking care of patients with inherited eye diseases like retinitis pigmentosa and Stargardt disease, as well as strabismus in patients with history of scleral buckle surgery to correct a retinal detachment. We had a great discussion, and I hope you like it!

The episode can be found here, and you can subscribe to the podcast on iTunes here.

Through Their Eyes

Different vision problems can affect our eyesight in different ways; not all eye problems cause blurriness or can be fixed with glasses. Here are some images I created that help illustrate how the world looks with different types of eye conditions. These images are based on the pathology that is causing the issue and on my experiences talking with patients.

How to Be Successful When on Call

I was on call over Christmas here in Spokane, and it was fairly busy. Not as busy as it would be for some other specialties, but still busy. For 96 straight hours, I was the ophthalmologist covering all consults for three hospitals in the city, and I was also on call for the patients in our call group, which consists of about 25 ophthalmologists. 

For the past eight years, I've had the opportunity to be on call hundreds of times. It's not my favorite part of my job -- and I'm not sure it is for anyone! -- but I've found a few tips that have helped me be successful on call:

1. Manage your expectations. If you assume you won't be busy, at best you will be satisfied, and more than likely you will be disappointed. By contrast, if you prepare for nonstop action, you will be pleasantly surprised and grateful if you get some sleep or time to sit down.

2. Be efficient. Focus on the "W-I-N" strategy: what's important now? What do you need to do to save this person's life/limb/vision until the morning? Don't get bogged down.

3. Most importantly: Remember, you signed up for this. Your patient did not. He or she is seeing you at one of the most vulnerable times in their life. They need your help.

When I posted this on my Facebook page, Dr. Tom Oetting, a great mentor and friend, had the following to say:

People are scared and often just need reassurance. Took me a long time (and having kids) to figure out just how anxious we as parents can get. . . Even though some of the things we see on call seem trivial to us they can really jazz up a family unit! So we shouldn't be surprised or resentful if some of our on call activity seems trivial.

Another friend, the retina surgeon Dr. Jayanth Sridhar, whose new podcast can be heard here, recommend the following:

Keep snacks in your bag. Something quick may end up being longer than you think. Always carry a phone charger.

What do you think? What tips for success on call have you found? Have you had any experience with on-call physicians that were particularly memorable? Comment below!

Being Fast

It was a hot, sunny summer afternoon, and we were all excited for high school graduation the next day. As was our habit, after school got out, my friends and I went over to a neighbor's house to play basketball on their beautiful outdoor full court, complete with painted lines and breakaway rims, just like the pros used. I grabbed a rebound, dribbled the length of the court, and went up for a dunk. I vividly recall being in midair, the defender underneath/in front of me, and realizing my body was now parallel to the ground and bad things were about to happen. I landed awkwardly on my arm, figured it was broken, and went to the emergency room with my mother.

  Dr. Swensen, recipient of the Utah State Orthopaedic Society's  2013 Sherman S. Coleman Humanitarian Award .

Dr. Swensen, recipient of the Utah State Orthopaedic Society's 2013 Sherman S. Coleman Humanitarian Award.

Mom asked for Dr. Laird Swensen, a hand surgeon who had taken care of my family in the past. Dr. Swensen, a tall, kind, soft-spoken 50-something-year-old, graciously rearranged his schedule to come see me. My wrist was indeed broken, and Dr. Swensen set the fracture and put on a cast. A few weeks later, when X-rays revealed the fracture wasn't healing perfectly, Dr. Swensen recommended surgery. Nervous that I would never be able to play basketball again (18-year-olds have a different version of what's important), I called him the night before surgery. He reassured me. The surgery went great, and my wrist has been as good as new ever since. Dr. Swensen became a hero of mine.

A few years later, I had the opportunity to work as an orderly in the operating rooms where Dr. Swensen and other orthopedists operated. I took patients to and from surgery and helped prepare and clean the operating rooms. Early on, while chatting with one of the surgical technicians, I mentioned how highly I thought of Dr. Swensen. My coworker shrugged and said, "He's so slow."

This comment caught me completely off guard. Slow? What does that mean? Who cares if he's slow? Why is that even a thing? Isn't the only thing that matters whether he's "good" or not? Perhaps my colleague was just accustomed to other orthopedic surgeries, which are often much quicker, and not to hand/wrist surgery, which, due to the intricate anatomy, is meticulous and often drawn-out. But I was still miffed that the first adjective used to describe this excellent surgeon was the word "slow."

Since that time, I have on occasion noticed that a slow surgeon can be an annoyance to others that work in an operating room -- including nurses, technicians, anesthesiologists, etc. -- because of how long their cases take. Also, from a patient safety standpoint, all other things being equal, the less time spent under anesthesia, the better, and from a business standpoint, the quicker a procedure is, the more time available for other patients and procedures. And slow doesn't automatically equate with good. I understand all of that. Maybe I was naive, but I just never imagined that a physician's speed would have any bearing on what colleagues thought of him or her.

This pressure, to be not only excellent but also efficient, is something that every surgeon and every physician faces. Clearly, the ideal is that care is both excellent and efficient, 100% of the time. That's what's best for patients. In most cases, it's possible. But sometimes things aren't straightforward; surprises happen in the operating room or in the clinic, and when that happens, it's crucial that speed take a back seat to quality. I believe it's important to strive for perfection, not just "good enough."

My favorite anecdote regarding this issue comes from a surgeon I know who, during a meeting with his boss, was made aware that he took longer to do a given type of surgery than his colleagues did. The surgeon -- accurately, by the way -- replied, "Yeah. But mine work." That surgeon understood that while time is of the essence in the operating room for many reasons, the most critical aspect of the case is that it's done well, not that it's done quickly.

Every time I enter the operating room, I think about that surgeon, and about Dr. Swensen. I am so fortunate to have trained at the University of Iowa and to work at the Spokane Eye Clinic with colleagues that share this same approach.

What do you think? Have you faced pressure to be both good and fast in your career? How have you handled that? Comments welcome!

Stars' Eyes: Casey Harris

You may not know Casey Harris by name, but odds are, you've heard his work:

Casey is the keyboard player for the alternative rock band X Ambassadors. Their hit single "Renegades," a tribute to people with disabilities who use and overcome them to accomplish greatness, came out in 2015, peaked at #17 on the US Billboard Hot 100 chart, and went platinum.

Why was this song so personal for Casey and his bandmates? Because Casey is blind.

He was born with Senior-Loken syndrome, a genetic disease that affects his eyes and his kidneys. Senior-Loken is a type of Leber congenital amaurosis (LCA), a blinding eye disease of childhood. Unlike other forms of LCA, Senior-Loken also affects kidney function; Casey needed a kidney transplant at age 23. At the time of this writing, there is no cure for this condition.

LCA can be caused by mutations in at least 19 different genes, and is usually inherited in autosomal recessive fashion, meaning one "bad copy" of the gene must come from both parents in order for a person to have it. A landmark gene therapy treatment trial has been performed for patients with LCA due to mutations in the RPE65 gene. One of several peer-reviewed publications from this study can be found here.

During my career, I have often been simply awestruck by the incredible accomplishments of patients with severe visual impairments like Casey has. They can do things -- like star in a band, run in the Olympics, be a champion weightlifter or golfer, or a prestigious scholar, to name a few -- that would be impressive for anyone, let alone someone with a disability. Their success helps give hope to others, and I'm grateful to be able to share their stories.

After my ophthalmology residency, I did an extra year of fellowship training in ophthalmic genetics, which gave me the opportunity to see patients with inherited eye diseases like LCA. Working with and learning from my mentors Dr. Edwin Stone and Dr. Arlene Drack at the University of Iowa, I marveled at the perseverance of the people I met, both the patients with the severe eye diseases and the doctors and scientists who had dedicated their lives to helping them. Here in eastern Washington, I have a special clinic just for patients with inherited diseases, and it's one of my favorite parts of what I do.

Here's the official music video of "Renegades," which shows different people with disabilities excelling, overcoming, and dominating. It's just awesome!

My efforts as an artist: learning to draw the retina

While in training at the University of Iowa's ophthalmology department, I was fortunate enough to have Dr. Stephen R. Russell as one of my mentors. Dr. Russell, a vitreoretinal surgeon and researcher, had himself trained at Iowa, and developed a love for retinal drawings.

In the past, ophthalmologists would often spend 30 minutes or more drawing a picture of what they saw during the patient's eye exam. The retina, the thin layer that lines the inside of the back of your eye, is the most expressive part of the eye, and even the exact same disease can look different from one patient to the next.

Since the advent of improved ophthalmic photographic techniques -- and the increase in the number of patients needing to be seen each day -- ophthalmologists don't take nearly as much time to draw their findings anymore. Lamenting this, Dr. Russell put together a beautiful book containing many exquisite drawings done by dozens of different ophthalmologists at Iowa.

Looking through this book for the first time was an emotional experience. Taking care of people's eyes means so much to me, and I could literally feel the love that these doctors -- all of whom had walked the same halls I was then walking, and many of whom had gone on to become giants in our profession -- had for their patients and their craft as they made these meticulous, beautiful drawings. I decided to put a little more effort into my drawings as time allowed.

Take a look at my own comparatively very unimpressive retinal art in this slideshow, and then scroll down to see a showstopping example from Dr. Russell's book.

Isn't strabismus just a cosmetic problem?

  Strabismus is more than just an aesthetic issue, as it can interfere with visual development in childhood.

Strabismus is more than just an aesthetic issue, as it can interfere with visual development in childhood.

This is a common question. The short answer is "No!" Want the the longer answer? Here are five reasons why:

  1. Strabismus, or eye misalignment, in children can cause amblyopia, or poor visual development, in the eye that isn't straight. This can be so severe as to cause permanent, severe vision loss. Fortunately, if detected, it can be treated effectively and reversed.
  2. Strabismus in children can prevent the natural development of something called "binocular fusion," a process in which the eyes learn to work together, so to speak. In the first year or two of life, the neural connections between the eyes and the brain are rapidly developing, and the brain learns to put the images produced by both eyes -- images which are similar, but not identical -- into one single image. This process allows us to develop depth perception. Strabismus very commonly inhibits this.
  3. Strabismus in adults typically causes diplopia, or double vision. It's easy to understand why: if the eyes are looking in different directions, they will produce different images, which the adult brain will see as double images. Want to know what that's like? Cross your eyes and walk around for a few minutes. It's decidedly unpleasant!
  4. Strabismus surgery, because it is not cosmetic, is covered by medical insurance.
  5. Strabismus in our society is unfairly associated with things like reduced intelligence and diminished potential for success in the workplace. Below is a review of the scientific literature on the negative societal implications of strabismus:
  • A 2001 study published in the Journal of the American Association for Pediatric Ophthalmology and strabismus allowed children to play with "normal" dolls and dolls that had been made to have strabismus. They were questioned after 10 minutes of play. Grade-school children were 73 times more likely to express a negative bias toward the dolls with strabismus. PubMed link
  • A 2003 study published in Acta Ophthalmologica Scandinavica showed photographs of the same children with and without strabismus to 30 elementary school teachers. Kids with strabismus were considered by teachers to be more unhealthy, less hard-working, and less happy. They were also felt to be less likely to be accepted by their peers and more likely to have difficulty learning. PubMed link
  • A 2000 study published in Ophthalmology showed photos of the same job applicants, both with and without strabismus, to potential employers. Women with strabismus were less likely to be considered for the job compared to women without strabismus. Strangely, this unfair bias was not seen toward men with strabismus. PubMed link
  • A 2008 study published in the British Journal of Ophthalmology interviewed 40 dating service agents, and 92.5% of them felt that a client having strabismus would make it more difficult to find a partner. Among facial disfigurements, only very prominent acne or a missing tooth had a greater negative impact. PubMed link
  • A 1993 study published in the Archives of Ophthalmology interviewed 43 teens and adults that had strabismus in childhood which was not corrected. Over 1/3 of them reported that their friendships had been moderately to severely affected, particularly friendships with the opposite sex. 84% reported that their strabismus interfered with school, work, and/or sports. Sadly, 50% said they had experienced ridicule or abuse because of their eye misalignment. The majority said it had a negative impact on their self image, and 1/3 made some attempt to hide their strabismus, with their hair, head position, or sunglasses. PubMed link

In sum, strabismus is much more than just a cosmetic problem. It has a significant impact on people's vision and quality of life. And it can be fixed! Helping patients fix their strabismus is one of the most gratifying parts of my job.

What do you think? Have you had strabismus and realized it's much more than a cosmetic issue? Have you treated patients who had been told previously that this was the case?

Special thanks to Dr. Scott Larson, MD, for compiling these scientific papers. Dr. Larson, a mentor and friend, is a pediatric ophthalmologist at the University of Iowa. His excellent website can be found here.

Stars' Eyes: Babe Ruth

  Many people don't know that Babe Ruth had severe amblyopia.

Many people don't know that Babe Ruth had severe amblyopia.

You probably know that George Herman Ruth Jr., also known as Babe, The Great Bambino, and The Sultan of Swat, was indisputably one of the greatest baseball players of all time. You may know that he came up with the Boston Red Sox before joining the New York Yankees. You might even know that began his career as a pitcher.

But did you know he had 20/200 vision in his left eye? Shocking, isn't it?

After his playing days were over, Ruth was examined by Dr. Gerald Kara, who found that the prolific slugger had surprisingly poor vision in his left eye (and 20/15 vision in his right), which Dr. Kara attributed to amblyopia. Because Ruth said he had never had an eye exam before, it is theoretically possible that his poor vision developed after his career was over, but Dr. Kara found no evidence that this was the case.

Amblyopia is the most common cause of reversible vision loss in children, affecting between 3-5% of all kids. It is defined as decreased vision due to abnormal development of vision in childhood, typically in one eye, and most commonly occurs due to unrecognized need for glasses or due to eye misalignment (strabismus). It is treated sometimes with glasses wear, and most frequently by patching the child's better-seeing eye. This forced use of the amblyopic eye helps the neural connections between the eye and brain develop properly, allowing for better vision.

I love treating amblyopia. Seeing a child start with one eye that doesn't see well at all, and then, over a period of months, thanks to the diligent work of the patient and parents in helping him/her keep the patch on, watching the vision improve -- it's a very gratifying experience.

With regard to Ruth, he is just one of the countless examples of people with a vision problem overcoming their circumstances and excelling in life.

Stars' Eyes: Jeremy Poincenot

Over the past year or so, on my Facebook and Instagram accounts, I've shared dozens of short posts with the tag "Stars Eyes Sunday," describing a famous person with an eye disease. These were popular posts, and I plan to continue sharing similar stories on this blog. Here's the first!

Jeremy Poincenot ("Points-en-oh") was a 19-year-old college sophomore at San Diego State when he suddenly lost his central vision in his right eye, followed shortly thereafter by his left. He was diagnosed with a rare optic nerve disorder, called Leber hereditary optic neuropathy (LHON).

LHON is a genetic condition caused by mutations in the DNA within mitochondria. Patients with LHON typically develop sudden, painless, central vision loss in one eye, followed weeks later by the other eye. The likelihood of developing LHON in a person who carries the mutation depends in part on what fraction of their mitochondria, the energy-producing organelles within each cell, harbor the genetic change. LHON occurs most frequently in young males, but females and much older patients can be affected, as well.

Jeremy hasn't let his severe vision loss hamper his love of the links. In fact, just today, he won the United States Blind Golf Association's National Championship! Jeremy has been featured on ABC's 20/20, MTV, and GolfWorld, and his website can be found here.

 Jeremy Poincenot, winner of the 2016 US Blind Golf Championship, as shared on his  Twitter account .

Jeremy Poincenot, winner of the 2016 US Blind Golf Championship, as shared on his Twitter account.

Will wearing glasses fix it?

  Wearing glasses helps fix some eye problems, but certainly not all of them.

Wearing glasses helps fix some eye problems, but certainly not all of them.

There is a common misconception that any eye problem can be fixed by wearing the proper glasses. This, unfortunately, is not true. Glasses and contact lenses help correct eye problems related to focus, and that's it.

Think of the eye as a camera. If the camera is out of focus, then it won't take a good picture. Focus the camera (or wear glasses, in our analogy), and you'll have a clear image.

Extending the analogy, here are a few categories of eye problems that cannot be fixed by wearing glasses:

Cataract (lens smudged)
Corneal disease (cloudy screen)
Optic nerve disease (dead battery)
Retinal disease (bad film)

What is this thing?

  A phoropter is used to measure refractive error.

A phoropter is used to measure refractive error.

The device you see pictured here -- from the cover of Justin Timberlake's 2013 album "The 20/20 Experience" -- is called a phoropter.

Used primarily to help determine a patient's glasses/contact lens prescription, it has been around for over 100 years. It contains dozens of different lenses which can correct for hyperopia, myopia, or astigmatism. With you seated comfortably, with both eyes open, and your forehead up against the back of the phoropter, the eye doctor will show you an eye chart and check each eye individually with different combinations of lenses. He or she will ask you which is sharper: #1, #2, or if they are the same. The goal is to find two options that appear the same to you in terms of clarity/sharpness. Based on the results, a prescription for eyeglasses or contact lenses can be issued.

What is astigmatism?

  Astigmatism occurs when the focusing structures of the eye -- the cornea and lens -- are not perfectly round.

Astigmatism occurs when the focusing structures of the eye -- the cornea and lens -- are not perfectly round.

I get this question a lot, and since it's often misunderstood, I thought it would be a great topic to discuss.

Astigmatism, along with the previously-discussed entities of hyperopia (farsightedness) and myopia (nearsightedness), is one of three common types of refractive error. Refractive errors are problems with the focusing system of the eyes.

A normal eye is round, like the baseball you see here. An eye with astigmatism, by contrast, has a cornea -- the clear, front part of the eye that focuses light -- that is steeper/more curved in one axis and flatter in the axis 90 degrees away, like a football. This means that light in an eye with astigmatism is focused at two different points on the retina, creating a blurry image.

Astigmatism, like all refractive errors, can be corrected with glasses, contact lenses, or laser surgery (e.g. LASIK). It is easy to identify in a routine eye examination.

What does it mean to be "farsighted?"

  The anatomy of hyperopia, or farsightedness

The anatomy of hyperopia, or farsightedness

In the simplest of terms, people who are farsighted have an easier time seeing far away than up close.

Why is this? Well, a farsighted eye is an eye that is either too short or too weak. Take a look at this picture. The image is focused behind the retina, not right on the retina where it will be sharpest. You can imagine that this could happen either because the eye is too small, or the focusing power is too weak.

Now, here is where hyperopia is a bit different from simply the opposite of myopia. Young people have the ability to accommodate -- to increase the power of their lens focus -- and this can neutralize farsightedness. Hence, a young person who is farsighted may have no trouble at all seeing far away or up close, even if their prescription is high, because there lens can change shape and focus the image. The natural decline of this ability with age is called presbyopia, and is the reason why many people need reading glasses beginning in their 40s and 50s.

If a person's hyperopia is significant enough to warrant correction, the available options are the same as those we discussed last time, for myopia, namely: glasses, contact lenses, and corrective surgery.

What does it mean to be "nearsighted?"

  Anatomical diagram illustrating myopia, or nearsightedness

Anatomical diagram illustrating myopia, or nearsightedness

First of all, myopia, or nearsightedness, means that relatively speaking, you see things better up close than far away. This is easy to remember, because the term "nearsightedness" suggests that you are best "sighted" at "near."

Take a look at the drawing here, of a myopic eye. Ideally, the cornea and lens at the front of the eye (left side of the drawing) should focus the light rays, from the image the eye is trying to see, right on the retina, at the back of the eye (right side). But look at this eye -- the image is focused in front of the retina. Nearsightedness! The eye is either too strong in its focusing ability or too long for its focal power.

So how can this be corrected? One way is by moving the object you look at closer to your eye. Why does this work? Simple optics. As the distance from the object to your eye decreases, the distance from the front of the eye to the image created by the eye increases -- the focal plane "moves backward." This means that instead of being focused in front of the retina, the image will be in focus farther back -- ideally, right on the retina. The more nearsighted you are, the closer this distance between the object you are looking at and your eye will need to be for you to see best.

OK, Dr. Weed, holding things close might work for books and whatnot, but it's not so great for sporting events, oncoming cars, other humans, etc. How else can nearsightedness be corrected? There are a variety of medical and surgical options. By wearing corrective lenses -- eyeglasses or contact lenses -- that "push the image back," so to speak, the eye can then focus images on its retina. Alternatively, a variety of surgical options, most commonly laser vision correction (e.g. LASIK), can be pursued.

Why do stars disappear when I look directly at them?

  Stars disappear when you look directly at them because of the anatomy of the photoreceptors in your retina.

Stars disappear when you look directly at them because of the anatomy of the photoreceptors in your retina.

We all have two types of light-sensing cells in our eyes, the rods and the cones. Cones see fine detail and color. Rods see better in dim light. When you look right at something that is small or far away, the image falls on a part of your retina where there are only cones. This means that if you're in a well-lit environment, you will see this object very well. If however you are in dim light, you'll see the object better out of your peripheral vision (looking just off to the side of your target) because then the image will fall on the part of your retina that has rods, which can see in dim light. This is true of everyone's eyes, but many people have never noticed it. There are a few VERY rare conditions that can exaggerate this phenomenon, but they are like 1 in 10,000 level rare. A dilated eye exam could detect them.