Have you ever wondered why your eyes must be dilated for an exam?  Find out why it’s so important.

Do you think of getting your eyes dilated as a nuisance?  We’ll be the first to admit that even though it’s painless, dilating your eyes is probably annoying at best.  Maybe you’ve never really understood just what we’re accomplishing by putting those pesky drops in your eyes.  Here’s your chance to find out.

Your eye exam begins with a thorough investigation of the lids, lashes, conjunctiva, sclera and cornea – the external surfaces.  Using a microscope and a bright light, the doctor will move in for a closer look at the anterior chamber, iris and crystalline lens.  The iris is very similar to the shutter of a camera.  When you take a picture on a bright sunny day, the shutter becomes smaller, allowing less light to enter.  Likewise, your pupil becomes smaller when we shine a bright light at your eye, making it very difficult to peer inside.  That’s where the dilating drops come in.

Dilating drops work on one of two principles:  they either stimulate the iris muscle that opens the pupil (the dilator), or prevent action of the iris muscle that closes the pupil (the sphincter).  After the drops take effect, your doctor can get a much better view of your retina, optic nerve and vessels in the back of the eye.  This is a very important part of your preventative eye care as well as some eye surgeries.  From this simple step, we are able to gather a lot of important information about your eyes.  In fact, some systemic diseases such as hypertension and diabetes are first discovered during the dilated eye exam. 

Some dilating drops also prevent accommodation.  The natural lens is able to accommodate or adjust the eye’s focus until about the age of 40.  Children and young adults are especially good at this, and their ability to accommodate sometimes prevents the doctor from getting an accurate refraction for glasses.  That’s why young eyes are often dilated for a “wet” refraction so the doctor can get a true picture of what the child’s prescription really is. 

There are a few things you can do to make your visit a bit more comfortable:

1. Don’t plan any activities after your appointment that require crisp vision.  (Plan to read the stock market page another time.)
2. Bring along a pair of dark sunglasses for the ride home.  Don’t worry if you forget yours, just ask for a disposable pair as you check out.
3. If you know you’ll have trouble seeing to drive home (even with the sunglasses), please bring a friend.
4. Bring a newspaper, book or magazine with larger print to read after the drops begin to work.

Strabismus
(Crossed or turned eye)

Overview

Strabismus is a problem caused by one or more improperly functioning eye muscles, resulting in a misalignment of the eyes.  Normally, each eye focuses on the same spot but sends a slightly different message to the brain.  The brain superimposes the two images, giving vision depth and dimension.  Here's an easy way to see how the eyes work together:  hold your finger at arm's length.  While looking at your finger, close one eye, then the other.  Notice how your finger changes position.  Even though the images are slightly different, the brain interprets them as one.

Each eye has six muscles that work in unison to control movements.  The brain controls the eye muscles, which keep the eyes properly aligned.  It is critical that the muscles function together for the brain to interpret the image from each eye as a single one.

Strabismus must be detected early in children because they are so adaptable.  If a child sees double, his or her brain quickly learns to suppress or block out one of the images to maintain single vision.  In a very short time, the brain permanently suppresses vision from the turned eye, causing a weak or amblyopic eye.  Children may also develop a head tilt or turn to compensate for the problem and eliminate the double image.  Unlike children, adults with a newly acquired strabismus problem typically see double.

There are many causes of strabismus.  It can be inherited, or it may be caused by trauma, certain diseases, and sometimes eye surgery. 
 
Signs and Symptoms

Adults are much more likely to be bothered by symptoms from strabismus than young children.  It is unusual for a child to complain of double vision.  Children should undergo vision screening exams to detect problems early.  The younger the child is when strabismus is detected and treated, the better the chance of normal vision.  The following are common signs and symptoms:

• Turned or crossed eye

• Head tilt or turn

• Squinting

• Double vision (in some cases)

 Detection and Diagnosis

Strabismus is detected with a comprehensive eye exam and special tests used to evaluate the alignment of the eyes such as: the Krimsky test and prism testing. 
 
Treatment

The appropriate treatment for strabismus is dependent on several factors including the patient's age, the cause of the problem, and the type and degree of the eye turn.  Treatment may include patching, corrective glasses, prisms, or surgery.

With patching, the better eye is covered, forcing the child to use the weaker eye.  Over time, the brain adjusts to using the weaker eye and vision gradually improves.  For this treatment to be effective, it must be done at a young age before the child can develop amblyopia.

Surgery is sometimes performed for both adults and children to straighten a crossed eye.  The procedure may be done with local or general anesthesia.  There are several different surgical techniques used to correct strabismus.  The appropriate one is dependent on the muscle involved and the degree of the eye turn.

Astigmatism

Overview

Astigmatism means that the cornea is oval like a football instead of spherical like a basketball.  Most astigmatic corneas have two curves – a steeper curve and a flatter curve.  This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near.  Astigmatism often occurs along with nearsightedness or farsightedness.

Illustration by Mark Erickson 

 
Signs and Symptoms

·         Blurred vision (near and distance)

 
Detection and Diagnosis

Astigmatism can be detected and measured with corneal topography, keratometry, vision testing and refraction.

 
Treatment

Astigmatism can be corrected with glasses, contacts, or surgically.  The most common surgeries used to correct astigmatism are astigmatic keratotomy (procedures that involve placing a microscopic incision on the eye) and LASIK.  The objective of these procedures is to reshape the cornea so it becomes more spherical or uniformly curved.

Nearsightedness (Myopia)

Overview

Nearsightedness or myopia, occurs when light entering the eye focuses in front of the retina instead of directly on it.  This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye.  Nearsighted people typically see well up close, but have difficulty seeing far away.  

This problem is often discovered in school-age children who report having trouble seeing the chalkboard.  Near-sightedness usually becomes progressively worse through adolescence and stabilizes in early adulthood.  It is an inherited problem.

Illustration by Mark Erickson

 
Signs and Symptoms

• Blurry distance vision
• Vision seems clearer when squinting

 
Detection and Diagnosis

Nearsightedness is detected with a vision test and refraction.

 
Treatment

The treatment for nearsightedness depends on several factors such as the patient’s age, activities, and occupation.  Vision can corrected with glasses, contacts, or surgery.  Refractive procedures such as LASIK can be considered for adults when the prescription has remained stable for at least one year.  

Presbyopia

Overview

Presbyopia, also known as the “short arm syndrome,” is a term used to describe an eye in which the natural lens can no longer accommodate.  Accommodation is the eye’s way of changing its focusing distance:  the lens thickens, increasing its ability to focus close-up.  At about the age of 40, the lens becomes less flexible and accommodation is gradually lost.  It’s a normal process that everyone eventually experiences.

Most people first notice difficulty reading very fine print such as the phone book, a medicine bottle, or the stock market page.  Print seems to have less contrast and the eyes become easily fatigued when reading a book or computer screen.  Early on, holding reading material further away helps for many patients.  But eventually, reading correction in the form of reading glasses, bifocals, or contact lenses is needed for close work.  However, nearsighted people can simply take their glasses off because they see best close-up.

 
 
Signs and Symptoms

• Difficulty seeing clearly for close work

• Print seems to have less contrast

• Brighter, more direct light required for reading

• Reading material must be held further away to see (for some)

• Fatigue and eyestrain when reading

 
Detection and Diagnosis

Presbyopia is detected with vision testing and a refraction. 

   
Treatment

The treatment for presbyopia is very simple, but is entirely dependent on the individual’s age, lifestyle, occupation, and hobbies.  If the patient has good distance vision and only has difficulty seeing up close, reading glasses are usually the easiest solution.  For others, bifocals (glasses with reading and distance correction) or separate pairs of reading and distance glasses are necessary.  Another option is monovision:  adjusting one eye for distance vision, and the fellow eye for reading vision.  This can be done with contact lenses or permanently with refractive surgery.

Conjunctivitis
(Pink Eye)

Overview

Signs and Symptoms

Diagnosis

Treatment
 

Flashes and Floaters
(Posterior Vitreous Detachment)
 

Overview

The space between the crystalline lens and the retina is filled with a clear, gel-like substance called vitreous.  In a newborn, the vitreous has an egg-white consistency and is firmly attached to the retina.  With age, the vitreous thins and may separate from the back of the eye.  This is called posterior vitreous detachment (PVD), a very common, usually harmless condition. 

As the vitreous pulls free from the retina, it is often accompanied by light flashes or floaters.  Floaters are caused by tiny bits of vitreous gel or cells that cast shadows on the retina.  Flashes occur when the vitreous tugs on the sensitive retina tissue.

There are other more serious causes of flashes and floaters, however.  Retinal tears, retinal detachment, infection, inflammation, hemorrhage, or an injury such as a blow to the head may also cause floaters and flashes.  (Have you ever seen stars after bumping your head?)  Occasionally, flashes of light are caused by neurological problems such as   When related to a headache, the flashes of light are seen in both eyes and usually lasts 20-30 minutes before the headache starts.

 
Signs and Symptoms

• Black spots or “spider webs” that seem to float in the vision in a cluster or alone
• Spots that move or remain suspended in one place
• Flickering or flashing lights that are most prominent when looking at a bright background like a clear, blue sky

Symptoms that may indicate a more serious problem  

• Sudden decrease of vision along with flashes and floaters
• Veil or curtain that obstructs part or all of the vision
• Sudden increase in the number of floaters

 
Detection and Diagnosis

Notify your physician immediately if you notice a sudden shower of floaters, new light flashes, a veil or curtain obstructing your vision, or any other change.  The doctor will dilate your pupils with drops and examine the vitreous and retina inside the eye with an ophthalmoscope. 

 
Treatment

Because of the risk, surgery is rarely indicated for PVD except when the floaters obscure the vision.  In these cases, surgical removal of the vitreous (vitrectomy) may be considered only if the vision is significantly affected. This treatment is rarely needed since floaters typically become less bothersome over a period of weeks to months as they settle below the line of sight.   However, vitrectomy may be indicated in a select group of patients with visually disabling vitreous floaters, as long as an objective assessment of the patient's visual disfunction from the floaters is made.

If the flashes and floaters are related to a problem other than a PVD, surgical treatment may be required.

Be proactive and monitor your vision

It is important to periodically assess the vision of each eye.  Many problems can be detected early by simply comparing both eyes. 

To test your vision:

1.  Cover one eye and pick a point to look at straight ahead

2.  Note the quality of your central and peripheral vision, noting any change

3.  Look for any obstructions, veils or curtains in your peripheral vision

4.  Watch for floaters, flashes

5.  Note the duration and intensity of the symptoms

6.  Cover fellow eye and repeat

Report any new symptoms or changes in vision to your eye doctor.   

The Retina

The retina is a very thin layer of tissue that lines the inner part of the eye.  It is responsible for capturing the light rays that enter the eye.  Much like the film's role in photography.   These light impulses are then sent to the brain for processing, via the optic nerve. Illustration by Mark Erickson