Vision Disorders – and Their Correction

Not all blurry vision is the same. This short video simulation shows how different eye conditions – called refractive errors – can change the way the world looks. It also explains which of these can be corrected with glasses or contact lenses, and which may require more advanced treatment. Watch the video to see how myopia, hyperopia, astigmatism, and keratoconus affect how people see every day.

What Are Refractive Errors?

Refractive errors occur when the eye doesn’t focus light properly onto the retina, resulting in blurred or distorted vision. They are extremely common… and mostly treatable.

Normal Vision​

With a healthy, well-shaped eye, light rays focus perfectly on the retina. This gives you a crisp, clear image at all distances with good contrast and no distortion.

Types of Refractive Errors

Myopia (Nearsightedness)

Myopia makes distant objects look blurry while close-up vision remains clear. The simulation shows how vision becomes progressively worse with increasing severity:

  • Mild (2 diopters): Slight blur for far-away objects.
  • Moderate (5 diopters): Clear only at short range.
  • Severe (10 diopters): Distant vision is very blurred.

Myopia can usually be corrected with refractive surgery, or alternatively, spectacles or contact lenses.

Hyperopia (Farsightedness)

Hyperopia causes difficulty seeing nearby objects, particularly during close-up tasks like reading. In more advanced cases, even distance vision can be affected.

Hyperopia is usually corrected with glasses or contact lenses, although some refractive surgery approaches are possible – especially if it forms part of cataract surgery or “refractive lens exchange”.

Astigmatism

Astigmatism is caused by an irregularly shaped cornea or lens, which bends light unevenly. This leads to distorted or stretched images—often at all distances.

  • Mild to Moderate (3 diopters): Mild blur and smearing.
  • High (6 diopters): Severe distortion and ghosting.

Correction: Glasses or toric contact lenses compensate for the irregular focus, but in general, laser refractive surgery can produce better visual outcomes.

Keratoconus: Several Refractive Errors in One

Keratoconus is a progressive disease that affects the structure of the cornea. Instead of being smooth and dome-shaped, the cornea becomes thin and cone-shaped. The video simulation shows how the consequences of this: leads to severe blur, ghosting (seeing double or triple), glare, and high sensitivity to light.

Unlike standard refractive errors, the irregular astigmatism seen in keratoconus cannot be fully corrected with conventional glasses. Instead, vision often requires rehabilitation with customized contact lenses (such as scleral or hybrid lenses), or surgical approaches such as corneal cross-linking to stabilize the disease, and intracorneal ring segments or topography-guided laser procedures to improve visual quality.

Presbyopia

If you’ve ever used a traditional SLR camera, you know that you can manually focus the lens by twisting it, which changes the distance of the lens to the photographic film or digital sensor. It’s the same with your eye’s lens. The lens is held in a transparent bag that is suspended from ciliary muscles – which can contract and relax to change the shape of the lens, achieving focus.

If the SLR camera’s focusing mechanism starts to rust, it gets harder and harder to move it and focus; eventually it will stop moving and it gets fixed to one focal length: only objects at one distance will be in focus; everything else is blurred. It’s similar with the eye; as you age, the lens gets stiffer and stiffer; the ability of the ciliary muscles to change its shape gets lower and lower, until (like the rusted SLR camera lens focusing mechanism) the lens is rigid, fixed to a single distance and everything else is blurred.

What to do?

Correction of visual errors

The classic method of vision correction has been to use spectacles. But there are a number of other methods that can be used to correct visual defects.

Contact Lenses

They offer an excellent way of correcting refractive errors, and are usually well tolerated to begin with. However, over time, many people become intolerant of contact lenses. Wearing them becomes uncomfortable and the risk of infection increases.

PRK

Photorefractive keratectomy (PRK) involves the use of an excimer laser to reshape the cornea to correct refractive errors like myopia, hyperopia and astigmatism. 

TransPRK

This is a completely non-contact method of performing PRK, in which the excimer laser is used to remove the corneal epithelium before reshaping the corneal stroma. The laser platform we use offers “SmartSurface” PRK which generates a smooth cornea which has optical advantages over previous generation lasers.

LASIK

Laser in situ keratomileusis. The cornea is cut to generate a flap, which is folded back and an excimer laser reshapes the underlying cornea. The modern variant is femto-LASIK, in which the incision required to make the flap for the procedure made by a second laser (a femtosecond laser) instead of a mechanical blade called a microkeratome. 

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