Common Ocular Conditions
All information on this site is provided for educational purposes. It is not a substitute for the advice of your optometrist.
Myopia (near-sighted) is a refractive error that causes blurred distance vision. It results from the eye being longer than average and as a result light focuses in front of the retina providing an unclear image. Myopia may present at any age although typically before the age of 20. Since the blur comes from the length of the eye the prescription can increase with growth and often changes after the initial presentation.
Hyperopia ( far-sighted) is a refractive error that causes blurred near vision. It develops when an eye is shorter than average and the light focuses behind the retina.
Occurs when the cornea has more curvature than average. When the cornea is shaped like a football instead of round it causes light to split and focus in two places. To correct the vision, a lens with two powers 90 degree apart is required. Astigmatism can present by itself or in combination with myopia or hyperopia. Uncorrected astigmatism can cause blur, headaches and eyestrain.
Presbyopia is a condition that affects everyone and presents in our early to mid 40s. The lens inside our eye that focuses for near vision becomes hard over time and can no longer automatically focus us for reading. Effectively the near prescription and the distance prescription have now become two different things. To correct presbyopia a lens is needed on the outside of our eye to compensate. The lens inside the eye continues to harden with age and whether we correct with reading spectacles or not, the condition progresses. Usually the reading spectacles increase in power every couple of years until mid 50s where the changes level off. If a patient has no refractive error they typically use reading glasses that they take on and off as needed. If there is already a refractive error present at the time presbyopia presents bifocals or progressive lenses are typically prescribed to ensure near and far clear vision. Although many myopic patients can take their distance spectacles off to read clearly since they are near sighted and have an up close advantage.
Strabismus: (Eye turn)
Strabsimus is an eye turn. The eye can turn in or out and usually presents in childhood. High refractive errors, muscle weakness and ocular disease are causes of strabismus. Most often the strabismus is caused by a high refractive error in young children. However in the case of every strabismus ocular disease must be ruled out. It is important to see an optometrist as soon as an eye turn shows up even if it only occurs when the child is tired. Strabismus untreated causes amblyopia ( lazy eye) which is the leading cause of reduced vision in children and is completely preventable. Very rarely strabismus can present in adulthood and usually is the result of trauma, loss of vision or cardiovascular disorders.<
Amblyopia: (lazy eye)
Amblyopia is a lazy eye. That is an eye that has poor vision regardless of any spectacle therapy. It is a problem with the development of the vision. The eye’s job is to focus light on the retina, the optic nerve then transmits that information from the eye to the occipital lobe in the back of the brain. If the eye is out of focus the pathway to the brain does not develop properly and the child is unable to process to the level of 20/20 vision. There is a critical period that this can be corrected, afte r the age of 8 it becomes very difficult to prevent a lazy eye because the brain is hard wired at that point. Amblyopia can be caused by any condition that causes one eye to be out of focus, that includes high refractive error, congenital cataract, ptosis (lid droop) and strabismus. Treatment involves removing the source of blur such as prescribing spectacles, cataract surgery or lid surgery. Often the strong eye will be patched to help development of the weaker eye. Due to the limited time we have to correct a lazy eye it is important to diagnose and treat early. If the amblyopia is not corrected early or watched closely depth perception can be reduced and certain careers may be limited. Annual eye exams will monitor for strabismus and amblyopia and prevent any reduced vision.
Posterior Vitreous Detachment (PVD):
Posterior Vitreous Detachment is the gel (vitreous) peeling off the back of the eye. It happens to every eye at some point, with increasing incidence with increasing age. The gel is attached to the retina in a ring around the optic nerve and around the outer retina periphery. With age the gel turns to liquid and the vitreous detaches from the back of the eye. Often there are no symptoms. Occassionally as the gel pulls off the retina it will pull on the retina causing flashing lights, and the ring attachment around the optic nerve may hover in the line of vision as a large floater. If you are having a symptomatic PVD in the form of a large floater or flashing lights it is important to see your optometrist immediately for a dilated retinal examination. When the gel pulls off the back of the eye it is possible that a tear or hole can be pulled in the delicate retinal tissue, which may lead to a retinal detachment. Retinal holes and tears need to be ruled out and often you will be monitored over the next 4 –6 weeks to ensure as the vitreous continues it’s detachment no problems occur.
Retinal tears/ holes and detachments:
The retina is very thin delicate neural tissue that lines the inside of the back of the eye and processes light. A tear or hole may develop if there is a head injury, thin area in the retina, vitreous pulling on the retina or if the tissue wears down (atrophy). Myopic patients have longer eyes than average and therefore the retina has to stretch over a larger area than normal leading to higher incidence of retinal tears and holes in moderate to high mypoes. If a tear or hole develops it can lead to retinal detachment. The eye is filled with gel/vitreous and that gel can work it’s way behind the retina through the hole and cause the retina to peel off the back of the eye. Since the retina processes light without it we cannot see. The signs and symptoms of a retinal tear or detachment are flashing lights, numerous floaters, and/or a curtain shadow obscuring the vision. If any of these things occur you need to see your optometrist immediately or if the office is closed head to your nearest emergency room for evaluation. If a tear or hole is detected an eye surgeon (ophthalmologist) can repair the area usually with laser. If it progresses to detachment the surgery is more invasive so to preserve vision it is important to act quickly.
Diabetes can affect the eyes in many ways. If the blood sugar rises, the sugar in the fluid of the eye rises and the lens swells causing the prescription to change. These changes may occur over days or rapidly over hours. Fluctuating blood sugars can lead to fluctuating vision. Most importantly diabetes affects the circulation in the body and the walls of the blood vessels can become weak and leak blood and lipids into the retina. This is referred to as diabetic retinopathy. If there is extensive bleeding, the retinal tissue becomes damaged and cannot be repaired.Therefore it is important to have annual eye exams with pupil dilation and retinal digital imaging to detect any leaks before they cover a large area. Early detection and treatment is crucial to prevent vision loss.
Cataract is clouding of the normally clear crystalline lens within the eye. It causes spectacle prescription changes, blur and glare. Factors that increase the risk of cataract development are age, accumulated UV exposure, trauma, certain eye diseases, certain systemic diseases, some medications and poor nutrition. In the early stages your optometrist will monitor cataracts and spectacle changes may help improve the vision. Wearing sunglasses with UVA and UVB protection may help prevent the progression of cataracts. If the cataract progresses and the vision is affected a referral to an ophthalmologist for a surgical consultation will arranged by your optometrist.
Glaucoma is progressive damage to the optic nerve resulting in reduced peripheral vision. The optic nerve is responsible for transmitting the information from the eye to the brain for processing. It may lead to tunnel vision and blindness if undetected and untreated. Typically the optic nerve is damaged from high pressure inside the eye (intraocular pressure), although there is a form of normal tension glaucoma where the pressures are within normal ranges. To detect glaucoma the optic nerves, eye pressure and peripheral visual fields need to be monitored by an optometrist.
Blepharitis is a chronic inflammation of the eyelids. This causes the eyelid margins to turn red with flakes at the base of the lashes. The ocular surface is often irritated with a foreign body sensation, burning, itching and there may be crusting of the lids in the mornings. The inflammation is usually caused by bacterial toxins on our skin. Left untreated it can affect the glands in the lids that produce our tear film, resulting in dry eye syndrome and styes.
Treatment for blepharitis is as follows:
- warm compresses twice daily
- lid scrubs with lid care towlettes twice daily
- artificial tears 6-8 times daily
- an antibiotic ointment for the lids may be prescribed by your doctor to control the bacterial load and decrease inflammation
Blepharitis is a chronic condition and the treatment tends to be ongoing to prevent reoccurrences.