Defects of Vision and Their Corrections > Myopia

Myopia, also known as nearsightedness, is a common refractive error where distant objects appear blurry, while nearby objects are seen clearly.  This occurs when light rays converge in front of the retina instead of focusing directly on it. It is also referred to as a refractive error because the eye cannot bend light properly.

Nearsightedness

Myopia is mainly caused by structural defects in the eye that affect light focusing.

Structural Causes:

1. Excessively curved cornea or lens → Increases the converging power of the eye lens.
2. Elongated eyeball → Increases the distance between the lens and retina, causing premature light convergence.

Due to these structural abnormalities, images of distant objects form in front of the retina, leading to blurred vision.

1. Simple Myopia: A mild form of myopia, correctable with glasses or contact lenses.
2. High Myopia: A severe form that progresses with age, increasing the risk of cataract, glaucoma, and retinal detachment.
3. Pathological (Degenerative) Myopia: A rare and severe form that can lead to permanent vision loss and cannot be corrected with lenses.

Symptoms of Myopia:

• Blurred vision when looking at distant objects (e.g., road signs, classroom boards).
• Squinting or partially closing eyelids to see clearly.
• Eyestrain and fatigue while performing activities like driving or playing sports.
• Frequent headaches due to prolonged focus strain.

Myopia Correction Methods:

A. Spectacles and Contact Lenses

Concave lenses (negative power lenses) are used to diverge incoming light rays, allowing the eye’s lens to focus the image directly on the retina. Eyeglasses and contact lenses are the most common correction methods.

B. Orthokeratology (Ortho-K)

A non-surgical treatment where a person wears rigid contact lenses overnight to temporarily reshape the cornea.  It is used for mild cases of myopia.

C. Surgical Treatments for Myopia

• Laser Surgery (LASIK, PRK, SMILE): It uses laser technology to reshape the cornea, correcting the light focus.
• Lens Implant Surgery: Involves inserting a corrective artificial lens inside the eye for permanent correction.

• Myopia is a vision defect in which distant objects appear blurry, while near objects are seen clearly.
• This occurs because the image of distant objects forms on the retina.
• The far point is not at infinity but is shifted closer to the eye.
• Causes include increased curvature of the cornea/lens or elongation of the eyeball.
• Corrected using a concave lens of negative power, which diverges light rays to focus the image on the retina.