If you are nearsighted or myopic, distant objects are blurred while near objects are seen clearly. The reason for this is too much focusing power, either because your cornea is excessively curved, or the eyeball is abnormally elongated. To have normal vision, the light rays entering the eye must be focused on the retina. However, in the case of myopia, the light rays are focused in front of the retina. The brain then receives blurry images of objects, which leads to blurry vision when looking at the distance.
1.2 What is farsightedness?
Farsightedness, also known as hyperopia, is when near objects are blurred, while distant objects are seen clearly. You have either a smaller shaped eyeball or insufficient curvature of the cornea, leading to decreased focusing power of the eye. Light rays entering your eye come into focus behind the retina, instead of focusing on the retina, where normal vision are retrieved, sending blurred messages to the brain. The brain interpreter the near objects now as blurred, and distant objects as clear.
1.3 What is astigmatism?
Astigmatism is the inability of your eye to focus clearly at any distance because your cornea is not symmetrical. The cornea is the transparent round central surface that covers the coloured iris and the black pupil. It is shaped like a rugby ball instead of a soccer ball, thus the one meridian is more curved than the other. Blurry messages are send to the brain at any distance, leading to headaches, eyestrain, red eyes and fatigue if not corrected. Astigmatism is often associated with hyperopia or myopia, and can be corrected either with spectacle lenses or contact lenses.
1.4 What is a cataract?
The crystalline lens, situated inside the eye, is the focusing mechanism of the eye. As we age, this clear lens becomes cloudy and yellow and loses its ability to change focus. This condition is called a cataract, and cannot be seen with the naked eye. The result is a general dimming of vision. A cataract may be slow to develop but once it appears, it almost always continues to become cloudier.
There is no known treatment such as diet, exercise, eye drops or laser technology to prevent formation or to cure a cataract. When it has developed, the only way to restore normal vision is surgical removal of the lens, through a small surgical stab incision and replacement with a permanent implant. Once a cataract has been removed, it will not come back.
Cataract removal is probably one of the most successful operations done on the human body, and no person should feel frightened if they are developing cataracts. For the first few days after cataract surgery, the eye may be red and sensitive, but full recovery usually takes about four weeks. For more information visit www.eyesite.co.za
1.5 What is a pterygium?
A pterygium is the pinkish yellow growth on the conjunctiva, which can be seen with the naked eye. The conjunctiva is transparent and covers the white sclera of the eyeball. The cornea is the round central transparent area that covers the coloured iris and black pupil. A pterygium can grow towards and onto the cornea, inducing astigmatism and loss of vision. When this happens, it needs to be surgically removed.
Pterygiums are fairly common in areas where people live mostly outdoors, and where they are more exposed to ultra-violet rays, wind and dust. When a pterygium is irritated by above factors it can become inflamed, red and uncomfortable. Therefore it is always wise to wear a good pare of sunglasses and use a moisture drop, to relieve discomfort.
1.6 What is a floater?
Floaters are a condition characterized by cloudy particles within the eye that seem to float about in the field of vision. As we age, the fluid in the eye becomes more compact, forming these cloudy particles. Due to gravity, these particles lay at the bottom of the eye and only on movement of the eye we seem to notice them. A good exercise is to stand facing a white wall, keeping the eyes very still. Upon movement of you eye, notice the shape and amount of floaters moving. Almost everyone has some floaters; they are quite common and are usually harmless.
When to consult your optometrist:
• When floaters increase drastically in a short period of time
• When you see a bright flashing of light
1.7 I am pregnant, how is my vision affected?
During pregnancy, a woman's body changes drastically to prepare for the birth of her child. Temporary eye conditions, due to an increase in hormones, can occur but vision returns almost to normal after delivery.
Symptoms can include:
• Reduced tolerance for wearing contact lenses
• Increases dryness
• Blurred and distorted vision
• Tunnel vision
1.8 Can medication trigger visual problems?
Drugs, and mostly drug combinations, where it improves one condition, can cause side effects in another part of the body. Taking these medications may have a drastic effect on your vision, due to the eye's blood vessels that are very sensitive and physiologically different from the rest of the body. These visual changes may be symptomatic of a reaction to medication: it includes dry or teary eyes, blurred, yellow or double vision, sensitivity to light, puffy eyelids, increased pupil sizes, poor night vision, and change in your normal eye color. Consult your GP before reducing any intake of medication.
2.1 Why do I need reading glasses?
As we get older, regardless of whether or not we have always had normal vision or have suffered from myopia, hyperopia or astigmatism, a natural age-related process steps in that affects everyone. When you go past the age of 40-50, the lens inside your eye loses its elasticity and cannot accommodate any more. Accommodate means it becomes difficult to focus on objects that are close at hand. Holding reading material at arms length, we temporarily compensate for this problem, however for this condition, called presbyopia, you normally need reading glasses.
2.2 How do corrective lenses work?
To correct visual problems, lenses are manufactured to adjust light waves, as they enter the eye, to focus optimally on the retina.
As previously discussed, in myopia, light rays are focused in front of the retina. A lens that is thicker on the edge than in the center is called a minus lens. This lens is used to place the light rays that is in front of the retina, back on the retina, correcting myopia. The more myopic you are, the thicker the edge of your lens will be. With this in mind, it is important when choosing your frame. A rimmed smaller shaped or plastic frame will hide your lens thickness, while the HRI lenses will decrease minification as well as lens thickness.
In hyperopia, the light rays entering the eye are focused behind the retina. A plus lens, which is thicker in the middle, than the edge, redirects the light onto the retina, correcting hyperopia or farsightedness. The higher your prescription of hyperopia, the thicker the center of your lens will be. It is important choosing HRI or knife-edge lenses, which will make the lens thinner, decrease weight, decrease magnification which will improve cosmetics. A rimmed or semi-rimmed plastic or metal frame is also advised.
To correct astigmatism, we use toric lenses. These lenses are extremely complex in that they have to bend light rays at different angles. Remember when choosing a frame, especially a semi-rimmed or rimless frame, that the angle at which you are astigmatic will be the thickest part of the lens.
When manufacturing contact lenses, it is based on the same principles as above. For more information on the best lens for your prescription, ask our trained optical dispensers and eyewear consultants.
2.3 What is a progressive lens?
A progressive lens is also known as a multifocal lens. Progressives are bifocals or trifocals without the lines, offering a continuous, gradual change in prescription strength from the lower (reading correction), to the intermediate (mid distance correction) to the upper (distance correction) portion of the lens. As a first time wearer of progressive lenses, you need to consider a two to three week adaptation period. During this time you learn to locate the areas of the lens needed for different viewing distances.
Head posture is of great importance when using progressive lenses and here two things play a role. Firstly you should point your nose at the object being viewed. Secondly you should lift or drop your head (chin) until clear vision is obtained. It might feel strange at first but adjustment is quick and automatic. Be careful when going down a flight of stairs, if you look down it will be blurry, due to the fact that you are looking through the reading portion. Either take off your glasses or move your head to look through the distant portion.
3. Contact Lenses
3.1 Can I wear contact lenses?
Contact lens technology had advance greatly in recent years, giving people freedom, comfort and choice. Today, almost all refractive errors can be corrected with contact lenses. There are essentially two types of lenses, hard and soft. Soft lenses consist of disposables lenses (worn either daily, two weekly or monthly) and conventional lenses (usually worn for a year). Hard contact lenses can be worn for longer periods than soft lenses. However the fitting of hard lenses has decreased, due to patient adaptation period, cleaning regime, fitting time and comfortability. Unlike glasses, a long contact lenses need special care to retain efficiency.
• Contact lenses require er initial examination and more frequent follow-up visits to maintain eye health; and more time for lens care.
• To wear your lenses successfully, you will have to clean and store them properly; adhere to lens wearing schedules; and make appointments for follow-up care.
• If you are wearing disposables, you will have to carefully follow the schedule for throwing away used lenses.
3.2 Can I sleep with my contact lenses?
You can sleep in certain contact lenses that are specific manufactured for continuous wear. Continuous wear, meaning sleeping in contact lenses for up to 30 days. These lenses can correct myopia, hyperopia and now even astigmatism. The silicone hydrogel material, allows more oxygen moving through the lens, supplying the eye with more oxygen, decreasing corneal swelling and improving the health of your eye. However not all patients can sleep in their contact lenses, therefore it is very important to have a thorough contact lens assessment, confirming suitability by your optometrist and regular follow-up visits to asses your eye's health.
3.3 I want to wear coloured contact lenses, what do I do?
If you want to wear coloured contact lenses for fun, you still need to see an optometrist for a contact lens consultation, even if you don't have visual problems. The reason for this is to determine if you are suitable for wearing contact lenses, giving instructions how to care for your lenses and to rule out any eye health problems. There are a variety of coloured lenses on the market, mostly monthly disposable. Dark and light coloured eyes can benefit from these contact lenses, whether you want a drastic change or just enhance your natural eye color. Remember that it is just as important to care for your coloured contact lenses, than any normal contact lens, even if you don't wear them everyday!
4. Laser Eye Surgery
4.1 What is laser surgery?
Laser surgery is a computer controlled excimer laser correction of the refractive error of the cornea. Refractive error means your visual problem which includes myopia, hyperopia and astigmatism. After surgery you don't need to wear your glasses or contact lenses any more. To determine whether you are a suitable candidate, the following must be taken into consideration:
• Your age,
• The stability of your refractive error
• The degree of your refractive error
• Thickness of your cornea
• Dry eyes
• Any diseases e.g. Diabetes Mellitus
• The risk factors involved in this surgery.
5.1 What are Vision Optometrists' product guarantees?
• A year guarantee is given on manufacturing faults on our frames.
• Polycarbonate, trivex and airwear material lenses are guaranteed on breakage of the lenses, until your prescription changes. Glass and plastic lenses are not guaranteed on any breakage.
• Anti-reflex coatings have a year guarantee on cracking and peeling of the coating.
• There is no guarantee on any scratching of lenses. If lenses are scratched, the scratch cannot be buffed out, you can only replace the lens.
• Children, up to the age of ten, spectacle lenses will be replaced on breakage or scratches, within a year from consultation date.
• No guarantee on tearing of contact lenses, unless the batch is faulty.