An eye exam at your local optometrist was essentially a vision checkup, resulting in a new eyeglass prescription.
In this new millennium, optometrists have become true doctors of eyes providing not only vision exams but treating eye disease due to infections, inflammations, allergies, dry eyes, and a host of other conditions.
Optometrists are involved in the treatment and management of cataracts, LASIK, glaucoma and corneal refractive therapy (CRT).
They are also responsible for primary eyecare, in the diagnosis and monitoring of systemic disease such as diabetes, hypertension and other vascular conditions.
Understanding the side-effects of systemic medications and how they can interfere with eye health and vision is crucial to the patient’s well being.
Writing prescriptions for medicine, communicating with Primary Health Care doctors and partaking in the entire healthcare of the patient has become a daily routine.
Optometrists are now specializing in specific areas of eyes and vision and becoming experts in those fields. It’s not uncommon, to find doctors of optometry advising patients on all aspects LASIK surgery, helping patients decide on the most appropriate type of intra-ocular lens for cataract surgery, providing expert advice and treatment with regard to eye nutrition, using the most advanced type of contact lenses, in hybrid and scleral form, to treat and provide excellent comfort and vision to those patients with post-surgical eye traumas, corneal transplants and medical conditions of severe dry eyes.
Furthermore, optometrists are becoming experts in conditions involving the eyelids which play an integral part in many dry eye diseases and treatment.
With the advent of conditions such as macular degeneration, many patients are still losing their sight even after extensive medical treatments with eye injections.
These patients still need to see and after the physician has maximized all medical therapy, Low Vision specialists in optometry are providing functional vision allowing them to conduct a near normal visual existence.
The days of optometrists being general eyecare providers for eye exams, eyeglasses and contact lenses are becoming a thing of the past.
There is a case to be made for a distinction between Optical Optometrists, who provide routine eye exams for eyeglasses and regular contact lenses and Medical Optometrists, who still provide those basic services but specialize in specific medical eye conditions involving comprehensive eyecare.
WHAT SHOULD YOU EXPECT IN A COMPREHENSIVE EYE EXAMINATION?
Before an exam is even performed, a thorough overview is undertaken.
- We essentially want to know your chief complaint.
- What is it that brings you in for an eye examination?
- Do you have issues with night time vision, glare, light sensitivity and double vision?
- When was your last exam, were there any changes in your eyes or vision at the time?
A Review of Systems is performed, encompasses your entire body into thirteen distinct areas to ascertain any medical conditions you have, both acute (short term) and chronic (long term).
We also need to know your mental status, mood and alertness at the time of the exam.
Are you taking any type of medication, including prescription, OTC (over the counter), nutritional or herbal supplements, as well as alcohol and tobacco use and recreational drugs? All of these can have an effect on your eyes and vision.
(Don’t worry, all this information is protected privacy.)
From a purely optical perspective, we need to know what your most current eyeglass prescriptions are. So be prepared to bring all your eyeglasses with you, especially if you have an old pair that’s your favorite.
All this information is a good start!
This entails several procedures, often conducted by optometric techs or assistants before the doctor sees you.
This is an instrument that uses a computer laser to measure your optical prescription
It is completely objective, meaning you don’t have to answer any questions, it’s all automatic.
This measures and maps the entire surface of the cornea (or front of the eye).
Very important to establish aberrations or distortions in the optical zone of the eye
Family history or your genetic makeup can be extremely valuable as to your risk factors with many eye conditions.
CCT (Central Corneal Thickness)
It measures the thickness of the cornea. Extremely valuable for LASIK consultations, as a laser is used to sculpt and reshape the cornea by ablation (shaving) hence removing some of the tissue.
Also, the CCT provides valuable information in the diagnosis of the condition of glaucoma.
Much of this information can be found in a search engine like Google and we encourage you to research it.
But be careful – “Dr. Google” will give you lots of “information” but your doctor will give you “knowledge!”
The difference of course is the doctor’s “experience” and how it specifically impacts you and your eyes.
This establishes what you are capable of seeing, both with and without your eyeglasses at both far and near.
We quantify this as “20/something.” The first “20” relates to optical infinity which is the equivalent of 20 feet away (or further.) This “20” is generally a fixed number, as most doctors examine in a room (with mirrors) that is approximately 20 feet. The second /20 or other number relates to the acuity of the size of an object that most normal eyes can see “with or without an eyeglass prescription” at 20 feet away. For example, 20/40 acuity means the image size has to be double that of the 20/20 image in order to see it at 20 feet and 20/200 would require the image to be 10X (times) the size of 20/20.
This brings up the most commonly or frequently asked question in all of vision – “What is legally blind?”
The answer has often been misleading for many reasons.
“Legally Blind” implies that one is unable, with the best possible eyeglass prescription, to see adequately for economic purposes. What that implies, is being gainfully employed, in that you can see sufficiently well to conduct yourself in job that requires usable everyday visual tasks. There is often misleading confusion as to what constitutes the phrase “legally blind.” This is perpetuated in the media when claims are made with someone having 20/200 or 20/400 vision and are considered to be legally blind. In reality, many people without their eyeglass prescriptions have 20/200 or worse for far away or distance vision.
The vast majority of them can be corrected with eyeglasses or contact lenses to 20/20 vision or thereabouts!
However, an extremely small percentage of those people, mostly having severe eye disease or other eye conditions, cannot be improved beyond 20/200. In that instance, the term “legally blind” is appropriate. In essence, if you are able to perform in a job which requires you to see what you are doing, then you are most likely NOT legally blind.
The Eye Examination can generally be considered to be composed of two distinctive and possibly unrelated components.
The one type is a “routine” exam for the purpose of correcting one’s vision, takes into consideration the measurements to obtain the formulation of your prescription for eyeglasses or contact lenses.
The other type of eye exam relates to an “eye problem” with eye health and/or medical implications, independent of your eyeglass or contact lens prescription.
Often, patients having a routine eye examination for a prescription alone, have medical conditions known or unknown to them, that can affect, not only their prescriptions, but their eye and systemic health as well. Most frequently, during a routine eye examination, the doctor will perform procedures that encompass not only your eyeglass prescription, but evaluating all the structures within the eye.
Cataracts, glaucoma and retinal issues are a few eye conditions doctors are diagnosing.
In addition, there are many systemic conditions, such as diabetes, hypertension, neurological damage, to name but a few, are first diagnosed during a routine eye exam.
Conversely, patients examined for a specific medical “eye problem”, are not considered ideal at the time for a routine exam for their eyeglass prescription, and need to return for that once that eye problem has been resolved. Irrespective, a comprehensive eye examination should encompass everything related to eyes and vision, including a general health evaluation, too.
The Actual Eye Exam
There are many diverse tests that doctors perform to ascertain your eyeglass prescription and to evaluate the condition of your general or specific eye health.
If you present with a medical eye condition, it is often not prudent to perform an exam for eyeglasses at the time. It’s best to do that at a later stage when the medical eye condition has been resolved.
Tests performed during a routine exam
Most doctors rely on their favorite tests, to provide them with all the information in obtaining your final prescription.
Very few doctors reach this final prescription the same way. Most do it differently but more often achieve the same end result.
There are two distinctive ways doctors obtain this information.
Primarily obtains information by the doctors’ observance, without the patient’s verbal interaction – such as would happen with an exam on a small child or infant.
This requires a response from the patient that allows the doctor to ellicit which lens is the correct one. The infamous “Is it better one or two?” is part of subjective testing
These are done without the patient’s response or input. The doctor gets this information by looking and observing, not by listening to the patients response to a test.
By shining a beam of light onto the retina at the back of the eye and observing the reflected light coming back
The eyeglass prescription can be ascertained by interspersing lenses in that beam of light changing the pattern of reflected light.
This can be extremely accurate if performed correctly and highly valuable in infants and young children whose verbal response is not possible or unreliable.
This test is the “old fashion” version of the more current computer driven Auto-Refraction.
It’s debatable as to which is more accurate.
This test is performed to ascertain the natural alignment of the two eyes.
Since the eyes are about 3-4ins apart, if they were pointing exactly straight ahead you would see two images.
The brain tells each eye to move slightly inward to point at the same target to obtain single vision.
This amount of movement can be significant and if so create eyestrain, headaches and even double vision.
This is often a problem when reading or doing close work as the eyes have a lot more turning in to do, especially if it’s for long periods of time.
An occluder (or cover) is placed over each eye separately and once removed the doctor observes the movement of the covered eye as it tries to align with the other open eye.
The pupil of the eye (black part in the middle of the color) is actually an opening for all the light to pass into the eye. It moderates the exact amount of light the eye needs in order to see. When it’s bright and sunny, the pupil constricts to being very small. However, at night it has to enlarge to obtain as much light as possible.
The pupil’s response to light is directly connected with many parts of the brain.
These pathways to and from the brain can be affected by any lesion, disease or trauma in the central nervous system and manifest in observing the pupils response to different light sources.
Brain Tumors, vascular disruptions, strokes etc as well as many types of drugs or medications that affect the central nervous system can be observed in the pupils.
This is essentially a microscope to observe and inspect all aspects of the front, middle and back of the eyes.
The details provide extensive information on the health of the eyes. Virtually every eye exam includes the use of this instrument.
Since the eye is filled with fluid, there is a measurable amount of pressure exerted within the eye.
If that pressure was too low, the eye could shrivel up like a prune.
However, if that pressure goes up too high, the force of this internal fluid presses on the retina and optic nerve head, temporarily cutting off the blood supply to these areas (Ischemia) which can often lead to the condition known as glaucoma.
Unfortunately for us, there are no pressure or pain sensors in the retina or optic nerve head.
Consequently, this continual lack of blood to nourish the retina leads to eventual cell and nerve fibre death.
Having undetected glaucoma can lead to blindness ultimately.
Tonometry is a test which measures this internal eye fluid pressure.
The proverbial “puff test” is known as non-contact tonometry.
(Interestingly, the puff test was developed about 40 years ago, in response to laws and scope of practice prohibiting non-MD doctors, like optometrists from using numbing eyedrops to perform the standard contact tonometry known as Goldmann Applanation Tonometry (GAT).
Fortunately, these days in all 50 states in the US not only does the law allow optometrists from using these drops to perform GAT, but actually allow optometrists to now treat many types of glaucomas with a variety of eyedrop medications.)
DILATED FUNDUS EXAM (DFE)
This is where the “dreaded” drops that dilate the pupil(s) are used, allowing a view of most of the retina or back of the eye.
A comprehensive inspection of the retina and all its structures allows the doctor to establish the health of the back of the eye. Everything that is one sees is projected onto the retina and then transmitted through nerve fibres to the visual cortex in the brain. Without a healthy retina, the eye cannot function properly.
If an area of the retina does not perform, a true blind area will exist.
If the entire retina is affected this way one would be considered completely blind and therefore see absolutely nothing, as if your eyes were permanently closed shut!
Since the retina is full of blood vessels, representative of the entire body, any disease such as hypertension, diabetes, metastatic cancers and a host of other conditions can be visualised and observed in the eye.
A DFE is not only the mainstay of a comprehensive eye examination for the purpose of determining eye health,but also one in which many people considered to be physically healthy have been diagnosed otherwise.
These are done with the specific intent of eliciting a verbal response to a test. The doctor often uses these tests to confirm what was established objectively
This is done to measure how “well” one can see both at far and at near, with or without eyeglasses.
It’s essentially the 20/20 or 20/something else measurement. (As outlined in great detail above)
By constantly changing lenses and asking if it’s “Better or worse?” is an excellent way of determining the prescription. The test “better one or two” makes up a significant part of this procedure.
Generally the end point of this test is the final eyeglass prescription.
This test is designed to establish if both eyes are looking or pointing in exactly the same position. This alignment is done both vertically (at the same level) and horizontally (one above the other)
Since the external eye muscles need to be 200-300 times more precise than arm or leg muscles, to work together to maintain single vision with both eyes, this information is highly valuable to assess whether eyes can maintain this for extended periods of reading, computer work and driving.
This measures the eye’s ability to focus from far away to up close vision. It establishes the flexibility of the lens inside the eye. This flexibility is directly related to one’s chronological age. If performed correctly, it can accurately predict one’s approximate age. For virtually every human being, without exception, if both eyes are fully corrected for far away vision, the ability to focus inwards in order to read at about 16ins, begins to become problem between the age of 42 and 45. Humans living closer to the equator, are more apt to have this happen slightly earlier between the age of 38 and 42 – primarily due to excessive ultraviolet ray exposure and conversely those living closer to the poles are affected a little later between the age of 45 to 48. There are exceptions to these numbers but only by a few years.
The classic statement that “my granny never wore glasses to read” is a heart-warming myth. The reality was that granny lived in denial of this and if given an eye exam at the appropriate age – she wouldn’t have been able to see small print, all things in her vision being equal.
Read more later under “Cataracts”