Hyperopia, also known as farsightedness or long-sightedness, is a common vision condition in which distant objects can be seen clearly, but close ones do not come into proper focus. This happens when the light that enters your eye lands behind your retina, rather than directly on it.
The eyeball of a hyperopic person is shorter than normal or the cornea is too flat, causing light to focus at a point beyond the retina. This could be a genetic trait inherited from parents.
What are the three types of Hyperopia?
Hyperopia can be categorised into three types, which are determined by the cause of the condition:
Simple Hyperopia
This is the most common type and usually develops in childhood. It's often caused by genetic factors where the eyeball is shorter than average, or the cornea or lens does not have enough curvature. As a result, light focuses behind the retina. Simple hyperopia can often improve as a child grows and the eye develops.
Pathological Hyperopia
This is a less common form of hyperopia and is usually caused by diseases, disorders, or other physical abnormalities in the eye. For example, it may be caused by an eye that did not develop correctly in the womb (a condition known as microphthalmos).
Functional Hyperopia
This form of hyperopia occurs when the eye's lens or cornea does not function properly, even though it may be physically normal. It can occur due to trauma, surgery, or other medical conditions affecting the lens's ability to change shape for focusing.
What are the causes of Hyperopia?
It's primarily caused by an irregularly shaped eye that prevents light from properly focusing on the retina. Here are the two primary structural issues that cause hyperopia:
- Short Eyeball: The most common cause of hyperopia is an eyeball that's shorter than normal. This shape means that light entering the eye focuses behind the retina, instead of directly on it, leading to a blurry image.
- Flat Cornea: If the cornea lacks an adequate curve, it can also cause light to focus behind the retina rather than on it, leading to hyperopia.
How can hyperopia be corrected?
There are several methods to correct hyperopia:
Eyeglasses or Contact Lenses
These are the simplest and safest methods for correcting hyperopia. The glasses or contacts have lenses that are thicker at the centre or edges, respectively, which refocus the light onto the retina.
Refractive Surgery
These are procedures that change the shape of your cornea to allow light entering your eye to be properly focused. Examples include:
- LASIK (Laser-Assisted In Situ Keratomileusis): A surgeon creates a thin flap in the cornea, and then uses a laser to remove a layer of corneal tissue. This effectively changes the cornea's shape and allows light entering the eye to be properly focused.
- PRK (Photorefractive Keratectomy): A surgeon removes a layer of the cornea's surface and then uses a laser to reshape the cornea.
- LASEK (Laser Epithelial Keratomileusis): A surgeon creates an ultra-thin flap in the epithelium (the cornea's outermost layer), preserves it during surgery, and then repositions it during recovery. This is a hybrid procedure that combines elements of LASIK and PRK.
- RLE (Refractive Lens Exchange): Also called clear lens extraction (CLE), lens replacement surgery (LRS), or lens exchange (LE), this surgery is essentially the same as cataract surgery. The eye's natural lens is removed and replaced with an artificial one.
- Phakic Intraocular Lenses (IOLs): A phakic IOL is an implantable lens that is added to the eye to correct the refractive error. The lens is placed without removing the natural lens.
Orthokeratology (Ortho-K)
This involves the fitting of a series of rigid contact lenses to reshape the cornea. The final lens in the series is left on for several hours a day to maintain the new shape.
