Vision Correction Simulator Guide

PhysicsIntermediateReading time: 3 min

Overview

Our eyes are like an extremely precise fully automatic camera: the crystalline lens acts as the lens (convex lens), and the retina acts as the film (screen). If the focusing function of this "lens" malfunctions, or if the "body" length does not match, it leads to vision impairment. This experiment simulates the causes of myopia and hyperopia, visually demonstrating how to use the deflection properties of lenses to make the blurry world clear again.

Background

Human understanding of vision defects dates back to the 1st century AD, when the Roman philosopher Seneca recorded the magnification of text using a glass globe of water. In the 13th century, Italian artisans invented the world's first reading glasses. In 1604, Kepler formed the first correct explanation of the optics of myopia and hyperopia in his book "Dioptrice" — explaining them as the focal point being offset relative to the retina. Since then, the use of concave lenses for myopia and convex lenses for hyperopia has become the fundamental principle of ophthalmic optics, a solution still relied upon by billions of people today.

Key Concepts

Myopia (Near-sightedness)

Characterized by seeing near objects clearly but distant objects blurrily. Caused by the eyeball being too long or the lens having too much refractive power, causing light to converge in front of the retina.

Hyperopia (Far-sightedness)

Characterized by seeing distant objects clearly but near objects with difficulty (similar to presbyopia). Caused by the eyeball being too short or the lens having too weak refractive power, causing light to converge behind the retina.

Concave Lens

A lens that is thinner in the middle and thicker at the edges. It diverges light rays and can move the focal point backward.

Formulas & Derivation

Lens Focal Length Relation

P = \frac{1}{f}

The refractive capacity of a lens is called its Optical Power (P). The higher the power, the shorter the

f

. The key to correction is ensuring the focal point of the compound system (eye + glasses) falls exactly on the retina.

Experiment Steps

1
Observe Normal Vision
Start with normal vision. Notice how parallel light rays converge precisely on the retina (the back wall of the eyeball).
2
Simulate Myopia
Switch to "Myopia" mode. Observe how the convergence point of the light rays changes relative to the retina. The focal point is ____ of the retina.
3
Correct Myopia
Click "Show Corrective Lens". What effect does the concave lens have on the light? Adjust the lens power. How does the focal point move? what power makes the focus fall exactly on the retina?
4
Simulate Hyperopia & Correction
Switch to "Hyperopia" mode and observe how the focal point differs from normal vision. Then enable the corrective lens. How does the effect of the convex lens distinguish from the concave lens?

Learning Outcomes

Master the geometric optical causes of myopia and hyperopia (relative focal position)
Understand the diverging effect of concave lenses and the converging effect of convex lenses
Learn to select the appropriate corrective lens based on the type of vision defect
Realize that the essence of protecting eyesight is to reduce the burden on the crystalline lens and maintain its accommodative elasticity

Real-world Applications

Myopia Glasses: The most widespread application of concave lenses among students
Reading Glasses: Convex lenses used by the elderly to compensate for the loss of lens elasticity
Contact Lenses: Same principle, but fit directly on the cornea, reducing visual distortion caused by framed glasses

Common Misconceptions

Misconception

Myopia is because the eyes ran out of strength

Correct

The opposite. Myopia is usually because the lens is "trying too hard" (excessive accommodation or spasm) or the eyeball has grown too long, causing light to converge before reaching the destination.

Misconception

Vision defects disappear when wearing glasses

Correct

Incorrect. Glasses provide optical compensation but do not change the physiological structure of the eye itself. Without glasses, the focal point will still deviate from the retina.

Ready to start?

Now that you understand the basics, start the interactive experiment!

Start Experiment Start Quiz