New technologies now include hard and soft contact lenses, laser surgery…

The idea

The eye focuses light using the cornea and lens, but defects like myopia and hyperopia blur vision. New technologies correct these defects by altering how light is refracted. Hard and soft contact lenses sit on the surface of the cornea to provide the correct refraction; soft lenses are flexible, while hard lenses are rigid and durable. Laser surgery permanently reshapes the cornea so its refractive power matches the eyeball's length, removing the need for glasses. Alternatively, a replacement artificial lens can be implanted inside the eye to correct severe focusing errors.

What earns the marks

• State that contact lenses sit on the surface of the cornea and refract light to compensate for visual defects.
• Describe laser surgery as a procedure that permanently changes the shape of the cornea to alter its refractive power.
• Explain that a replacement lens involves implanting an artificial lens inside the eye to correct severe focusing errors.
• Compare the risks of these technologies, noting that surgery carries risks of internal eye infection or permanent damage, whereas contact lenses carry a risk of surface infections if not cleaned properly.
• Contrast hard and soft contact lenses, noting that soft lenses are generally more comfortable but hard lenses are more durable.

Common mistakes and how to put them right

• Thinking contact lenses sit inside the eyeball or change the shape of the cornea.

  Put it right: Contact lenses sit on the outer surface of the cornea and refract light, but they do not alter the cornea's physical structure.

• Confusing the cornea with the lens when describing laser surgery.

  Put it right: Laser surgery reshapes the cornea (the clear front surface of the eye), not the internal lens.

• Assuming all corrective procedures carry the same risks.

  Put it right: Distinguish between surface risks (e.g. corneal infections from dirty contact lenses) and internal surgical risks (e.g. retinal damage from replacement lens surgery).

Exam tips

• Link each technology to its specific mechanism: laser surgery reshapes the cornea, contact lenses sit on the cornea to refract light, and replacement lenses are implanted internally.
• When asked to evaluate these technologies, always provide a balanced argument by giving at least one specific benefit (e.g. convenience for sports) and one specific risk (e.g. surgical complications) for each method.