Eye Exam Refraction
Refraction is a fundamental foundation for all eye exams. Refracting gives the best lens prescription in giving optimal visual acuity, which includes determining whether the patient is ‘nearsighted’ or ‘farsighted’.
- What is Myopia (Nearsighted vision)?
Nearsighted patients see well close up but have difficulty seeing at a distance. Anatomically, the eye is too long compared to the focusing power of the eye, causing light to focus in front of the retina. This may cause difficulty seeing street signs, white boards, box scores on the television, and recognizing people who are still a distance away. However, as the reference name implies, most “nearsighted’ patients are able to see objects that are near very well. This can be easily corrected with glasses and contacts.
- What causes Myopia?
An excessively curved cornea or elongated eyeball are factors related to nearsighted vision, also known as myopia. Nearsightedness is believed to primarily be hereditary passed on through ‘myopia prone genes’.
- Can I do anything to improve or prevent Myopia?
The human eye usually matures to a stable point soon after 20 years. There are several treatment options that have been studied, including specialty contact lenses, prescription eye drops (.01% atropine), multifocal glasses or contact lenses, and different eye exercises. However, it is important to note that every myopic patient has unique variables to their condition and should consult with a licensed eye doctor to address realistic options. Myopic prescriptions will always have a minus (-) as the sphere portion of the prescription (i.e. -5.00DS).
- What is Hyperopia (Farsighted vision)?
Farsighted patients see well in the distance but have difficulty seeing up close. Anatomically, the eye is too short compared to the focusing power of the eye, causing light to focus behind the retina. Typically, you are able to strain to focus your eyes to see, but this may cause eyestrain and headache, especially with extended computer work or reading. This can be easily corrected for in glasses and contacts.
- What causes Hyperopia?
Hyperopia, also known as farsightedness, is caused by a shortened eyeball or an abnormally flat cornea. Most children are naturally farsighted because the eye is still maturing, but are able to adjust distance vision with a natural squint. For the most part, chronic hyperopia is considered hereditary, but may develop randomly.
- Can I do anything to improve or prevent Hyperopia?
Corrective glasses and contact lenses should help most hyperopic patients to see clearly. There are some corrective surgeries that can help to correct mild to moderate cases of hyperopia. It is important to note that every hyperopic patient has unique variables to their condition and should consult with a licensed eye doctor to address realistic options. Hyperopic prescriptions will always have a plus (+) as the sphere portion of the prescription (i.e. +3.00DS).
- What is Astigmatism?
- Although astigmatism sometimes is mistaken as a more serious eye condition, it is a common refractive error that can be easily treated with corrective eyewear. Most eyes are not shaped perfectly as a sphere (like a baseball), but more oval (like a football). This changes how light is focused and can cause images to look blurred vertically or horizontally, or ghosting/double images. It is important to note that astigmatism can occur independently or with myopia (nearsightedness) and hyperopia (farsightedness). It can also manifest in both eyes or one eye.
- There are technically three primary types of astigmatism: myopic (nearsighted), hyperopic (farsighted) and mixed astigmatism (combination of myopic/hyperopic). The three different types of astigmatism are determined by the anatomy of the primary meridian observed through a slit lamp by your optometrist or ophthalmologist.
- Some cases of astigmatism may cause headaches, severe blurred vision, eyestrain, constant squinting and difficulty seeing at night. This can be easily corrected with glasses and contacts.
- What causes Astigmatism?
Every eye has a natural contact lens called the cornea. Astigmatism is caused by an abnormal curvature of the cornea. There are also two classes of astigmatism: regular astigmatism and irregular astigmatism. Regular astigmatism is usually hereditary. Irregular astigmatism is usually the result of eye surgery, an eye condition called keratoconus, or an eye injury.
- Can I do anything to improve or prevent astigmatism?
- Astigmatism can be corrected with prescription glasses, contact lenses and some refractive surgeries. It is always important to consult a licensed eyecare provider to address all viable options to help improve your vision. Astigmatic prescriptions will be designated by both an amount and an axis (i.e. -1.25 x180).
- Although regular astigmatism cannot be avoided, protecting your eyes from injury and strain can help prevent irregular astigmatism. Drinking water regularly to keep the eyes hydrated, avoid reading in low lit areas and limit time staring at monitors (tablets, computers, etc) may also help prevent the progression of eye disorders.
Can I do anything to improve or prevent Presbyopia?
- What is Presbyopia?
- Needing additional prescription to see up close.
- Official definition: normal loss of near eye focusing ability caused by the loss of elasticity of the lens of the eye; typically occurs with middle and mature age groups.
- An optometrist can determine if you have presbyopia during the exam:
- Near visual acuity - how well you see up close
- Accommodation (Eye focusing ability) is tested during entrance exam
- Determining your Add
- Understanding your Working Distance - A standard working distance is about 16 inches (40cm). However, where you naturally hold your reading material or phone may differ and can be accommodated for when prescribing your reading prescription.
- Computer glasses prescriptions can be made and tailored to your office set up.
Knowing how far away from your eyes your laptop or desktop screen is can help determine the best computer glasses prescription.
- What causes Presbyopia?
- Every functioning eye has a natural focusing system called the crystalline lens. Initially the lens and the surrounding muscles have the elasticity to zoom in and out on objects close up and at a distance. Presbyopia is generally related to age; as the eye matures the lens begins to thicken and loses flexibility, which prevents the eye from zooming into objects up close.
Presbyopia can be treated with prescription eyeglasses, contact lenses and various surgeries are also available.
- Prescription eyewear
- Progressive Addition Lenses (PAL) allow the most flexibility in multifocal glasses. The top of the lens is for distance viewing, the central portion gradually increases in reading prescription (intermediate viewing), and the bottom of the lens is for reading/near work.
- Bifocal lenses have a clear delineation between distance viewing and near viewing seen as a line on the lens. This allows for clear vision for far away and for reading, but may have some difficulty in the intermediate distances (2-4ft).
- Trifocal lenses are similar to bifocal lenses but have an additional segment for intermediate viewing.
- Contact lenses
- Multifocal Contact Lenses use a special technology to allow you to see both far and close without having to wear glasses.
- Monovision Contact Lenses designates one eye to see far and the other eye to see close, teaching the brain to adapt to when to use each eye as needed.
- Refractive Surgery
- Karma Inlay
- Monovision Lasik
- NearVision CK
- Refractive Lens Exchange (RLE)
What is binocular vision?
Although it may seem obvious that we have two eyes (The prefix “bi” means two and “ocular” means eyes), how the eyes team and work together is not as well known. Each eye sees a different image that is then sent to the brain to be processed into one image. If there is any misalignment of the eyes, the signals the eye sends to the brain may cause confusion leading to blurry or double vision. Binocular vision is responsible for how we perceive depth perception and see 3D images (i.e. 3D movies! If you have any difficulty appreciating 3D movies or feel nauseous or uncomfortable afterwards, you may have a binocular vision problem).
How do you check binocular vision?
There are many different tests to evaluate binocular vision. Here are just a few that may be used in your comprehensive eye exam:
- Cover Test: This test involves having you stare at a letter/picture while the optometrist covers and uncovers your eyes to check eye alignment. This can be tested at both far and then close distances.
- Extraocular muscles Test: This test involves following an object with your eyes in multiple different directions. These evaluate the 6 different muscles each eye has that are responsible for moving the eye.
- Stereo Acuity Tests: Typically for this test you wear polarized glasses and look at specially made polarized images to evaluate how detailed your depth perception is.
- Near Point of Convergence (NPC): This test involves following an object with your eyes as it is moved from arms length towards your nose.
- Vergence Ranges: This test uses prism (special lenses that change the direction of light) to see the range the eyes are able to cross and uncross. This can be tested at both far and near distances.
What is Convergence Insufficiency?
For any kind of near viewing such as reading, using your phone/tablet, computer, sewing, drawing, writing, our eyes have to point closer together more than when looking far into the distance. If near work causes any kind of eyestrain, headaches, tired eyes, blurry/double vision, you may have Convergence Insufficiency. “Convergence” means bringing together and “Insufficiency” meaning not enough. This condition is very treatable with vision therapy. After treatment, many patients feel they can do near work without difficulty and for much longer than before.
What is Strabismus/Amblyopia?
Strabismus is a misalignment of the eyes (eye turn) which can be outward (“wall-eyed”) or inward (“cross-eyed”) or vertical. This condition can occur during infancy, or develop at a later time. It is important for later-onset eye turns to be evaluated promptly as the cause of the eye turn can be a brain tumor. Amblyopia, also known as “lazy eye,” occurs when an eye does not develop 20/20 vision. Thus, even with the proper glasses prescription, the eye cannot see as sharply as is should. This is commonly caused by strabismus or anisometropia (having very different glasses prescriptions between the eyes).
There are many treatments, including vision therapy, to help the eye achieve individual vision goals including comfortable visions.
Vision Therapy Exam
Checking Eye Pressure
What is the purpose of checking the eye pressure?
Intraocular Pressure (IOP) is measured with the practice of Tonometry measured in millimeters of mercury (mm Hg). Eye pressure should range between 8-22 mm Hg. Measuring eye pressure is important to help the optometrist evaluate the levels that are higher than normal (exceeding 22 mm hg), which can potentially lead to eye disease like glaucoma.
How does eye pressure work?
The eye is composed of many different fluids that need to consistently drain and regenerate. While the eye generates new fluids, the existing fluids need to drain to maintain a consistent pressure within the body of the eye. Disruption of the flow causes the fluid to back up and increase the pressure of the eye, which can damage the optic nerve (how the image travels to the brain) and cause vision loss. Extensive stress to the optic nerve is known to lead to eye disease like glaucoma. Early detection and treatment is vital to preventing permanent damage including blindness.
What can change eye pressure?
Eye injuries are a common factor with disrupting the fluid flow within the eye. Most injuries usually heal and resume a normal flow. However, there are many unique factors that are a silent disruptor and may disrupt this flow of the fluid, which is the reason that it is important to regularly have your eyes checked.
What are symptoms of glaucoma?
Glaucoma has been known as the “silent thief” of eyesight. You may not notice any symptoms of glaucoma, such as peripheral vision loss, until permanent damage has occurred. This is why it is important to have annual eye examinations to check the health of your eyes.
However, a less common form of glaucoma, called angle closure glaucoma, can be very symptomatic. Symptoms include blurred vision, halos around lights, severe eye pain, tunnel vision, headaches, and in some cases nausea and vomiting. If you are experiencing any of these symptoms you should contact a physician as soon as possible.
How do you treat Glaucoma?
Every glaucoma case is unique and should be treated by an Optometrist or Ophthalmologist licensed to treat glaucoma. Some common treatments include oral medication, eye drops, laser treatment, or surgery. Every patient is unique so you should always contact a licensed physician to address all your available options.
How do you check eye pressure?
- Non-contact Tonometry: This is commonly called the “air puff test.” While the patient looks in at a blinking light, the instrument will blow a puff of air at the eye.
- Applanation tonometer: After instilling an eyedrop that has an anesthetic and dye, the patient sits in the slit lamp while a blue light illuminated cone shaped probe is gently put in contact with the eye to measure the pressure.
- Icare: This handheld instrument uses a small plastic probe to gently take eye pressure. There is no need for anesthetic drops with this test.
- Tonopen: After instilling anesthetic into the eye, this handheld instrument gently touches the eye to take multiple eye pressure measurements.
- Palpation: If a patient or child is unable to do the other eye pressure tests for any reason, the eye care provider can do a broad check of eye pressure by gently pressing on the patient’s closed eye.