“The two most beautiful things you open every morning are your eyes”, the adage is indeed so true.
Having said that, it cannot be stressed enough that good eye health is inevitable. Talking of care, where to start? Well, the answer to that is “Awareness”.
In the fast-paced digital world, there is so much noise about health and lifestyle but very little is talked about eye conditions and treatments. It is studied that by 2050 more than half of the world population will need correction for accurate vision. If that is true, it is an individual responsibility to have a basic understanding of eye conditions, corrections and most importantly what product to purchase to mitigate these vision needs.
Furthermore, before moving to the topic of this blog let me tell you another interesting fact. Just like Iris of the eye that is distinctive for each human, Astigmatism along with Myopic or Hyperopic correction has possibilities for so many power combinations; it is hard to find 2 people with the same power.
Without any further delay, let us move on to what is Astigmatism?
Out of various refraction conditions of the eye, Astigmatism has a significant impact on our overall health other than just blurred vision.
Astigmatism meaning
By definition, Astigmatism is a refractive error of the eye in which light rays coming in the eyes form two focal points. This is because of horizontal or vertical axis or meridians are different.
In other words, it is the inconsistencies of the surface of the Cornea or the crystalline lens that causes the formation of two focal points. A normal Emmetropic eye forms only one focal point that falls on the center of the retina for impeccable vision.
Let us look at the diagram below, to understand this better.
Types of astigmatism
Broadly, there are two types of Astigmatism; irregular and regular. Let us look at each in detail:
Irregular astigmatism: A condition where the curvature of the cornea and the crystalline lens is uneven at the various axis, in other words; highly uneven, it is known as irregular astigmatism. This is a rare condition that cannot be cured with spectacle or contact lenses.
Regular astigmatism: A condition when light rays form two focal points on the retina, in front of the retina or behind the retina in one eye or both. The amount of correction required could be different for each eye. Although, not both eyes may necessarily be astigmatic.
Causes of regular astigmatism
However, there is more than one factor that causes regular astigmatism. Experts in the field have classified them as follows:
- Corneal Astigmatism: This type of astigmatism is caused by the irregular or uneven curvature of the cornea as the name suggests.
- Curvature Astigmatism: Another type of astigmatism caused by the irregular curvature of the crystalline lens of the eye.
- Index Astigmatism: When the light rays travel from one medium to another, their speed and direction change. This reduction of speed is known as the refractive index. By default, the refractive index of the lens is 1.39. In this type of astigmatism, the index of the lens is different at every place of the lens. Having said that, let me also tell you that our lens is only 9 to 10 mm in size and every bit of it matters for your vision.
- Positional Astigmatism: A condition where the lens is tilted. Hence, causes the light rays to form two focal points.
Astigmatism may not necessarily be present in both the eyes and if it does the power required for correction and the axis may not be the same for both the eyes. For example, your right eye may be Emmetropic (Normal eye) or may require correction at say 180o axis wherein your left eye may require correction at 15o axis.
Types of regular astigmatism
To understand further, here are different types of regular astigmatism with its example:
- Simple Hypermetropic Astigmatism: Hyperopia is a condition in which a plus power correction is required to achieve an accurate vision. Here, the distant objects are blurred but nearer objects are clearly seen by the patient. This is because light rays focus behind the retina. In this type of astigmatism, two focal points are formed; one on the retina and the other behind the retina. Hence, a Plano +cyl lens is used for correction.
| Sph | Cyl | Axis | |
| R | – | + 0.25 | 180o |
| L | – | + 0.50 | 10o |
- Simple Myopic Astigmatism: Unlike Hyperopia, Myopia is a condition where a minus power correction is given to extend the focal point falling in front of the retina to fall on the retina. A major symptom of this condition is that the patient has clear near vision but the distance vision is blurred. In this type of Astigmatism, one focal point forms on the retina while the other forms in front of the retina. A Plano –cyl is used for correction.
| Sph | Cyl | Axis | |
| R | – | – 1.50 | 10o |
| L | – | – 1.75 | 160o |
- Compound Hypermetropic Astigmatism: Similar to simple hypermetropic astigmatism but here both the focal points fall behind the retina. Correction required is +Sph or +Cyl.
| Sph | Cyl | Axis | |
| R | +1.00 | +0.50 | 180o |
| L | +1.50 | +0.75 | 20o |
- Compound Myopic Astigmatism: In this condition both the focal point falls in front of the retina. Hence the correction required is –Sph or –Cyl.
| Sph | Cyl | Axis | |
| R | -4.00 | – 1.00 | 90o |
| L | -1.00 | – 0.75 | 110o |
- Mixed Astigmatism: A very distinctive condition where one focal point forms in front of the retina and other behind the retina. Hence, both plus and minus power correction is required i.e, +Sph & -Cyl.
| Sph | Cyl | Axis | |
| R | -3.00 | + 0.75 | 20o |
| L | -3.25 | + 1.00 | 170o |
Astigmatism symptoms
The symptoms of astigmatism are quite obvious:
- Regular headache
- Irritation or mood swings or grumpiness
- Difficult in vision or blurred vision
- Nausea
- Double edges are seen on the periphery of the objects
Astigmatism correction
Now, that Astigmatism is clearly understood it is to be known that there are 3 types of treatments possible for this condition:
Astigmatism glasses: It is best recommended to visit an eye doctor, optometrist, or your local optician if you are experiencing any of the above symptoms.
Furthermore, using ARC (Anti-reflective coating) lenses with UV protectors can help protect your eyes from damage and permit high light transmission through the lenses.
The correction for astigmatism can be a little more expensive than myopic or hyperopic corrections, especially if the power required is high. In such cases, the lens needs to be designed based on your power hence the cost increases. However, you can still manage your cost for your astigmatism glasses with the type of frame and coating you choose.
Soft Contact lenses for astigmatism: The contact lenses designed for astigmatism are known as toric lenses. How is it different from a regular contact lens? Well, it has a correction set on the required axis and it is slightly weighted at the bottom of the lens so that axis is automatically adjusted to the cornea.
Another thing to remember is that the power you need for your spectacle lenses is not the same for contact lenses as they back vertex i.e, the distance between the lens and your eye is removed in a contact lens. Why? That because you directly wear them on your eye. So before making a purchase it is important you check with a doctor or your optician to what power you need even if you are looking to buy online.
There are various parameters to check while purchasing contact lenses like the expiry time such as monthly or yearly contact lenses and also the type of lens i.e., semi-soft, hydrogel, or silicone. The difference lies in the transmission of oxygen and the level of comfort. Silicone is the latest advancement in the field of contact lenses. However, you may take advice from experts for determining the best suit for your eyes.
Again the cost of toric lenses goes slightly above the regular contact lenses. You may also request customized color toric lenses with your astigmatic correction.
If you are a presbyopic patient you can buy multifocal contact lenses for astigmatism.
Lasik eye surgery for astigmatism:
While this may seem to be a one-time investment; the complaint ratio is quite high. It is best suggested to do prior research before choosing to go for Lasik eye surgery.
Finally, astigmatism can cause havoc in your daily life. It is crucial to get an eye test done without delay. Though this type of condition is not usually seen developing with age, it is a good practice to get your eyes checked every six months.
