Spectacles

Glasses, also known as eyeglasses or spectacles, are vision eyewear with clear or tinted lenses mounted in a frame that holds them in front of a person’s eyes, typically utilizing a bridge over the nose and hinged arms, known as temples, that rest over the ears for support.

Glasses are often used for vision correction, such as reading glasses for farsightedness and also to correct nearsightedness. Specialized glasses may be used to view visual information, such as 3-D glasses for 3-D films (stereoscopy). Possibly in Pisa, Italy, in the 13th century, the first pair of eyeglasses were made, although it is unclear who the inventor was.

Eyesight Correction – Nearsightedness

Myopia, or nearsightedness, is typically corrected with spectacles using negative or minus lenses.  These lenses diverge incoming light rays, ensuring they focus to a sharp point on the retina and improve distance vision. Spectacles for myopia are a standard and effective treatment option. 

Explanation

  • Minus lenses: Myopia is corrected with concave, or minus lenses, which are thinner in the center and thicker at the edges. These lenses diverge light rays entering the eye, so they focus slightly further back than they would without correction, landing directly on the retina. 
  • Prescription: The prescription for myopia glasses is a negative number, indicating the strength of the lens needed to correct the refractive error. The higher the negative number, the stronger the lens. 
  • Myopia management: While traditional spectacles correct myopia, some spectacle lenses, like Stellest lenses, MiYOSMART lenses, and those with ZEISS MyoCare technology, are designed not only to correct vision but also to help slow down the progression of myopia in children.

Eyesight Correction – Farsightedness

Farsightedness, or hyperopia, is a refractive error that can be corrected using various methods, including eyeglasses, contact lenses and refractive surgery. The goal is to focus light correctly on the retina, enabling clear vision. 

Corrective Lenses

  • Bifocals/Multifocals: For those with presbyopia (age-related farsightedness), bifocal or multifocal contact lenses can provide correction for both near and distance vision,
  • Eyeglasses: Prescription eyeglasses with convex lenses can be used to correct hyperopia. These lenses converge light and focus it correctly on the retina. 
  • Contact Lenses: Similar to eyeglasses, contact lenses can also correct hyperopia by refocusing light on the retina. 

Figure 1: Human Vision and Optical Correction of Focussing Errors