Myopia, Hyperopia & Astigmatism

If your eyes are normal, you can see near and distant objects clearly. The objects do not look blurry or distorted.

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
• Hyperopia
• 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 media of the eye.

Symptoms that indicate Myopia
If you are suffering from-

• Blurred distance vision
• Eye-strain and headache
• Watering 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

LASIK is a safe and permanent treatment for myopia that eliminates the dependence of myopic patients on spectacles or contact lenses.

In a myopic LASIK procedure

• The doctor first creates a thin protective flap of corneal tissue using an instrument called the Microkeratome or by a blade-free procedure (Intralase Femtosecond laser).
• He gently lifts 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 replaces the protective flap, where it heals naturally and securely.

This procedure is quick, painless and in most cases you can return to your normal activities very quickly, usually within hours.

What is ‘Hyperopia’ or ‘Far-Sightedness’?
People who have hyperopia can focus on distant objects but cannot clearly view objects in the near distance. The rays of light come to a focus behind the retina.

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

Different types of hyperopia include

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

Curvature hyperopia – This condition occurs when the curvature of the cornea or the lens is too flap.

Index hyperopia – 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.

The absence of the crystalline lens in its normal position in the eye causes high hyperopia which is also called ‘aphakia’.

Symptoms that indicate hyperopia

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

Treatments for hyperopia
There are a variety of correctional methods for hyperopia. These include

• 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 or by using Intralase femtosecond laser (blade-free LASIK).
• He gently lifts this flap, thereby exposing the deeper corneal layers.
• He then removes the tissue from the central and and mid-peripheral portion of the cornea with an Excimer laser.
• This steepens the central corneal curve, refocusing light back on to the retina.
• He gently replaces the protective flap, where it heals naturally and securely.

This procedure is quick, painless and in most cases you can return to your normal activities very quickly, usually within hours.

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 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 eg: keratoconus
• 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?
The remedies for astigmatism include the use of :

• Toric glasses
• Semi-soft contact lenses/rigid gas permeable 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
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/blade-free femtosecond laser procedure (Intralase).
• He gently lifts this flap, exposing the deeper corneal layers.
• Then he uses an Excimer laser to remove tissue from the portion of the cornea in the steeper axis preferentially.
• This focuses light back on to the retina by decreasing the irregularity in the various meridia.
• He gently replaces the protective flap, where it heals naturally and securely

This procedure is quick painless and in most cases you can return to your normal activities very quickly usually within hours.