The results are the familiar ratio of 20/20, 20/40 etc. which is a comparison of your vision
compared to the average person with good vision, which is typically 20/20. For example, a patient
that has 20/40 vision, can only see at 20 feet what the normal person can see from a distance of 40 feet.
This test is a preliminary test of how clearly you are seeing in each eye but it does not give you a
prescription for corrective lenses.
Those who don’t have 20/20 vision have what is referred to in most cases as a “Refractive Error.” The patient may have nearsightedness, farsightedness, astigmatism or other eye conditions that prevent the patient from seeing 20/20. A refraction will tell the doctor which prescription lenses will correct your eyesight to achieve 20/20 vision or whichever amount your vision is correctable to.
A refraction may include a couple of steps.
Retinoscopy is a test that allows the doctor to obtain an approximate prescription for eyeglasses. In this test the doctor uses a hand-held instrument called a retinoscope that shines a light into the patient’s eye. The doctor then analyzes the reflex of the light from the patient’s eye to determine the patient’s prescription for glasses.
An instrument called a phoropter is something most patients associate with an eye exam. This space age appearing instrument, positioned in front of the patient’s face during the eye exam, gives the doctor the ability to determine the patient’s focusing ability as well as their eye alignment. The phoropter also determines which, out of the hundreds and hundreds of potential eyeglass prescriptions, will help the patient see as clear as possible. Using the phoropter, the doctor will ask the patient which series of lenses makes their vision the clearest.
While retinoscopy is quite effective for children and nonverbal patients, there are now a number of computerized or automated instruments available today to help doctors accurately determine a patient’s eyeglass prescription.
Autorefractors and Aberrometers
Autorefractors and aberrometers are computerized machines that are able to measure your refractive error to determine your prescription for glasses or contact lenses. These instruments are usually used in addition to testing described earlier:
– An autorefractor is similar to retinoscopy, which electronically analyses the light reflex from the patient’s eye.
– An aberrometer measures distortions or aberrations in the cornea and lens of the eye that disrupt proper focus of light on the retina. Using wavefront technology, the instrument measures the rays of light as they pass through your eye to look for imperfections which may indicate a refractive error.
During the comprehensive eye exam, your eye doctor will also want to test how your eyes function individually and together from a mechanical perspective. In order to see clearly and comfortably, your eyes need to work together as a team.
The final and most important aspect of a comprehensive eye exam is a check of your overall eye health. These tests (below) are done to identify any eye conditions or diseases, both inside the eye as well as the external parts of the eye, that could affect your vision and general health.
Slit Lamp Test
The slit lamp or biomicroscope is an instrument that allows the doctor to examine the internal and external parts of the eye in detail, such as the conjunctiva, iris, lens, cornea, retina and the optic nerve. The patient rests their forehead and chin on a headrest to stabilize the head, while the doctor looks into the eye with the slit lamp microscope, which is magnified with a high-intensity light. A slit lamp test enables the doctor to evaluate the eyes for signs of normal aging and eye pathology, such as conjunctivitis, cataracts, macular degeneration or retinal detachment. Early diagnosis and treatment of eye diseases are essential for preventing vision loss.
Tonometry is a test to detect glaucoma by measuring the pressure inside your eye or IOP (intraocular pressure). Glaucoma can cause vision loss and even blindness if the IOP in the eye is too high and damages the optic nerve.
The applanation tonometer, typically attached to a slit lamp, is one of the most common instruments used to measure the pressure in the eye. Prior to doing this test the doctor will numb the patient’s eyes using an anesthetic, before gently applanating (putting pressure on) the patient’s cornea to measure the pressure in the eye.
During your comprehensive eye exam, your doctor may decide to do a dilated eye exam. In this test, your doctor will instill dilating drops in each eye, which would enlarge your pupils to give the doctor a better view of certain parts of the back of the eye. Dilation is done at the discretion of the doctor, with some patients dilated every year and others at specified intervals; the frequency of dilation will vary for each patient.
Typically the drops take around 20 to 30 minutes to take effect and may last up to several hours following the exam; each patient is different. Since more light enters your eyes when your pupils are dilated, you will be more sensitive to bright light, especially sunlight. Although your doctor may provide disposable sunglasses, you may want to bring a pair of sunglasses to wear after the exam to make it more comfortable until the drops wear off.
If you decide to opt for contact lens wear, it is very important that the lenses fit properly and comfortably and that you understand contact lens safety and hygiene. A contact lens exam will include both a comprehensive eye exam to check your overall eye health, your general vision prescription and then a contact lens consultation and measurement to determine the proper lens fit.
The Contact Lens Consultation
The contact lens industry is always developing new innovations to make contacts more comfortable, convenient and accessible. Therefore, one of the initial steps in a contact lens consultation is to discuss with your eye doctor some lifestyle and health considerations that could impact the type of contacts that suit you best.
Some of the options to consider are whether you would prefer daily disposables or monthly disposable lenses, as well as soft versus rigid gas permeable (GP) lenses. If you have any particular eye conditions, such as astigmatism or dry eye syndrome, your eye doctor might have specific recommendations for the right type or brand for your optimal comfort and vision needs.
Now is the time to tell your eye doctor if you would like to consider colored contact lenses as well. If you are over 40 and experience problems seeing small print, for which you need bifocals to see close objects, your eye doctor may recommend multifocal lenses or a combination of multifocal and monovision lenses to correct your unique vision needs.
Contact Lens Fitting
One size does not fit all when it comes to contact lenses. Your eye doctor will need to take some measurements to properly fit your contact lenses. Contact lenses that do not fit properly could cause discomfort, blurry vision or even damage the eye. Here are some of the measurements your eye doctor will take for a contact lens fitting:
In order to assure that the fitting curve of the lens properly fits the curve of your eye, your doctor will measure the curvature of the cornea or front surface of the eye. The curvature is measured with an instrument called a keratometer to determine the appropriate curve for your contact lenses. If you have astigmatism, the curvature of your cornea is not perfectly round and therefore a “toric” lens, which is designed specifically for an eye with astigmatism, would be fit to provide the best vision and lens fit. In certain cases your eye doctor may decide to measure your cornea in greater detail with a mapping of the corneal surface called corneal topography.
Pupil or Iris Size
Your eye doctor may measure the size of your pupil or your iris (the colored area of your eye) with an instrument called a biomicroscope or slit lamp or manually with a ruler or card. This measurement is especially important if you are considering specialized lenses such as Gas Permeable (GP) contacts.
Tear Film Evaluation
One of the most common problems affecting contact lens wear is dry eyes. If the lenses are not kept adequately hydrated and moist, they will become uncomfortable and your eyes will feel dry, irritated and itchy. Particularly if you have dry eye syndrome, your doctor will want to make sure that you have a sufficient tear film to keep the lenses moist and comfortable, otherwise, contact lenses may not be a suitable vision option.
A tear film evaluation is performed by the doctor by putting a drop of liquid dye on your eye and then viewing your tears with a slit lamp or by placing a special strip of paper under the lid to absorb the tears to see how much moisture is produced. If your tear film is weak, your eye doctor may recommend certain types of contact lenses that are more successful in maintaining moisture.
Contact Lens Trial and Prescription
After deciding which pair of lenses could work best with your eyes, the eye doctor may have you try on a pair of lenses to confirm the fit and comfort before finalizing and ordering your lenses. The doctor or assistant would insert the lenses if you are unable and keep them in for 5-10 minutes before the doctor exams the fit, movement and tearing in your eye. If after the fitting, the lenses appear to be a good fit, your eye doctor will order the lenses for you. Your eye doctor will also provide care and hygiene instructions including how to insert and remove your lenses, how long to wear them and how to store them if relevant.
Your eye doctor may request that you schedule a follow-up appointment to check that your contact lenses are fitting properly and that your eyes are adjusting properly. If you are experiencing discomfort or dryness in your eyes you should visit your eye doctor as soon as possible. Your eye doctor may decide to try a different lens, a different contact lens disinfecting solution or to try an adjustment in your wearing schedule.
An eye that suddenly becomes red is a cause for worry. Any increased discomfort and blurred vision are often accompanied with red eye. Without a red eye exam performed by a professional it is difficult to determine the cause or cure for a patient’s red eye.The condition may not be an emergency, however, red eye can be an indicator of scleritis, episcleritis, fungal / bacteria / viral pink eye, a necessity for foreign body removal (a piece of metal, for example), or allergic conjunctivitis.
We want you in as soon as possible to ensure everything is okay with your eyes, as your health is our number one concern!