Myopia, Hyperopia and Astigmatism

Introduction

Do you have trouble seeing close objects' Distant objects' Both' These are common vision problems called refractive errors. Glasses or contact lenses can almost always correct these problems. However, in some cases, a laser may be used to correct your vision. Your eye doctor can tell you what your vision problem is and suggest the best treatment for you.
Testing your vision
A simple eye examination can reveal most vision problems. By using eye-charts, lenses, and special instruments, your eye doctor can measure your eyes' focusing power. This way, he or she can provide the prescription you need for glasses or contact lenses. Your eye doctor may also dilate your eyes to see how healthy they are.

Glasses

Glasses change the way light focuses on the inside of your eye. Glasses are fairly easy to get used to and take care of.

Contact Lens
Contacts lenses work just like glasses. But contacts are worn on your eyes. They can take more time to adjust to and care for.

Refractive surgery
This surgery changes the shape of your eye itself. Most often, a laser is used to reshape the cornea (clear front layer of the eye). This reduces your need for glasses or contacts.

The normal eye

If your eyes are normal, you can see close and distant objects clearly. The objects do not look blurry or distorted. If your eyes are normal, your eyes see objects as light. The cornea focuses light rays onto the retina (a layer that lines the back of the eye). If your eyes are normal, this process produces a focused image on the retina. This makes objects look clear.

If your eyes are normal, you can see close and distant objects clearly. The objects do not look blurry or distorted.
If your eyes are normal, your eyes see objects as light. The cornea focuses light rays onto the retina (a layer that lines the back of the eye). If your eyes are normal, this process produces a focused image on the retina. This makes objects look clear.

Refractive errors cause imperfect vision
Refractive Errors are the most commonly found type of vision defects. Refractive error may be of three types:

Myopia
Hypermetropia
Astigmatism

What is 'Myopia' or 'Short Sightedness' ?
In myopic patients, rays of light are focused at a point in front of the retina instead of on the retina. Due to this defect a person can see near objects clearly but distant vision is blurred.

Causes of myopia:

Axial myopia : In the great majority of cases, myopia is axial, that is, it is due to an increase in the antero-posterior diameter of the eye. It is more commonly called the elongated eye.
Curvature myopia : This is myopia caused by refractive errors resulting from excessive corneal curvature.
Index myopia : This is caused due to the change in the refractive index of one or more of the eye media.

Symptoms that indicate Myopia :

If you are suffering from :

Blurred distance vision
Eye-strain and headache
Watering and congestion of the eye

Chances are you are Myopic.
How to treat Myopia?

Concave Spectacle Lenses
Contact lenses - Soft & Gas Permeable
Laser surgery for myopia - Lasik & Custom LASIK
Phakic Intra Ocular Lens - ICL & Phakic Intra Ocular lens
Refractive Lensectomy

In a myopic LASIK procedure:

The doctor first creates a thin protective flap of corneal tissue using an instrument called the Microkeratome.
He gently folds back this flap, thereby exposing the deeper corneal layers.
He uses an Excimer laser to remove tissue from the central portion of the cornea.
This flattens the central corneal curve, refocusing light back on to the retina.
He gently folds back the protective flap, where it heals naturally and securely.

Hypermetropia

What is 'Hypermetropia' or 'Far-Sightedness'?

The cause of Hypermetropia is the failure of the lens to return to its normal rounded shape. Hypermetropia is also caused by the eyeball being too short. Both these conditions result in the image being focused on a point behind the retina.

Causes of hypermetropia :

Different types of hypermetropia include:

Axial hypermetropia :
This condition occurs when the antero-posterior diameter of the eye is too short and the retina is too near the optical system.

Curvature hypermetropia :
This condition occurs when the curvature of the cornea or the lens is too small.

Index hypermetropia :
This condition occurs under any of the following circumstances :

The refractive index of the aqueous humour is too low.
The refractive index of the vitreous humour too high or
The refractive index of the lens is too low.

Symptoms that indicate Hypermetropia :

Blurring of vision for the close work
Eyestrain
Headache
Muscular fatigue, the symptom of eyestrain

Treatments for Hypermetropia

Spectacles Convex Glasses
Contact lenses - Soft & Gas Permeable
Laser surgery for Hyperopia - Lasik & Custom LASIK
Phakic Intra Ocular Lens - ICL & Phakic & Verisyse Intra Ocular lens
Refractive Lensectomy

In the hypermetropic LASIK procedure :

The doctor first creates a thin protective flap of corneal tissue using an instrument called the Microkeratome.
He gently folds back this flap, thereby exposing the deeper corneal layers.
Then he removes the tissue from the central portion of the cornea with an Excimer laser.
PThis steepens the central corneal curve, refocusing light back on to the retina.
He gently folds back the protective flap, where it heals naturally and securely.

Astigmatism

What is 'Astigmatism?

'Astigmatism' is a condition that is caused by an irregularly shaped cornea or an irregularly shaped lens. In Astigmatism, the unequal power in different meridians of the cornea causes rays of light to form a distorted line instead of focusing on a point. This results in the blurring of both distant and near vision.

What are the causes of Astigmatism?

Curvature astigmatism
Disease of the cornea resulting in its deformity; extreme example of this is seen in conical cornea
Trauma to the eye involving cornea

What are the symptoms of Astigmatism?

A point of light appears tailed off and a line, which consists of series of points, appears as a succession of strokes fused into a blurred image.
Eye-strain
Headaches
Reflex nervous disturbances such as dizziness, neurasthenia, irritability and fatigue.

What are the treatments available to correct Astigmatism?

Toric glasses
Semi-soft contact lenses
Laser surgery for Astigmatism - Lasik & Custom LASIK
Phakic Intra Ocular Lens - Toric ICL & Toric Verisyse Phakic IntraOcular lens
Refractive Lensectomy - Toric Intra Ocular Lens Implantation

Toric glasses :

Toric spectacle lenses have two prescription powers; one to correct long or short-sight and the other to correct astigmatism. The two lenses lie perpendicular to each other and the spectacle lens has different or varying thickness across the lens surface.

Contact lenses - Soft Toric & Gas Permeable :

Soft Toric lenses have twin power that is possible due to the different curvatures at different angles (one for astigmatism, the other for either myopia or hyperopia). Some soft toric lenses also have a mechanism to keep the contact lens relatively stable on the eye. This prevents movement of the lenses when you blink or look around. Stability of the toric contact lenses is necessary for steady vision.

In the astigmatic LASIK procedure,

Your doctor first creates a thin protective flap of corneal tissue using an instrument called the Microkeratome.
He gently folds back this flap, exposing the deeper corneal layers.
Then he uses an Excimer laser to remove tissue from the central portion of the cornea.
This makes the central corneal curve more spherical, refocusing light back on to the retina.
He gently folds back the protective flap, where it heals naturally and securely

Get regular eye exams

Regular eye examinations are a must.

Eye exams are important to measure and correct vision problems. But seeing an eye doctor regularly also helps detect other eye problems. Early diagnosis and treatment of eye problems could save your eyesight.