👓 Patient Guide — Eye Condition ஀யறியின் கல்வி — கண் நோய்

Refractive Errors

தெறி஫ு பிழ்

Understanding myopia, hyperopia, astigmatism, and presbyopia — diagnosis and correction options explained.

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Patient Guide

Refractive Errors

Myopia · Hyperopia · Astigmatism · Presbyopia
What are Refractive Errors? தெறிவு குறைபாடு என்றால் என்ன?

For clear vision, the eye must bend (refract) incoming light so that it focuses precisely on the retina. A refractive error occurs when the shape of the eye prevents light from focusing correctly, resulting in blurred vision.

Four Types of Refractive Error

  • Myopia (short-sightedness): The eyeball is too long, or the cornea too curved — distant objects are blurry, near objects are clear. Very common and often begins in childhood.
  • Hyperopia (long-sightedness / far-sightedness): The eyeball is too short — near objects are blurry; distant objects may also be blurry if severe. Young children often have mild hyperopia which resolves naturally.
  • Astigmatism: The cornea or lens is oval (like a rugby ball) instead of round. Light focuses at two different points, causing blur and distortion at all distances.
  • Presbyopia: The natural age-related loss of near-focusing ability that affects virtually everyone after age 40. The lens becomes less flexible and cannot accommodate for near vision. Reading glasses or bifocals are the usual solution.
How are Refractive Errors Diagnosed? எப்படி கண்டறிவார்கள்?
  • Visual acuity test: Reading the eye chart at distance and near with and without correction
  • Retinoscopy / auto-refraction: Objective measurement of the refractive error using light reflex
  • Subjective refraction: Patient feedback — "which is clearer, 1 or 2?" — to fine-tune the prescription
  • Keratometry: Measures corneal curvature — important for astigmatism assessment and contact lens fitting
  • Corneal topography: Detailed mapping of the corneal surface — screens for keratoconus (progressive corneal thinning)
  • Dilated fundus exam: After dilating drops, the retina and optic nerve are examined to rule out pathology behind any visual symptoms
Correction Options — Spectacles, Contact Lenses, Surgery சரிசெய்யும் வழிகள் — கண்ணாடி, கான்டாக்ட் லென்ஸ், அறுவை
OptionAdvantagesLimitations
SpectaclesSafest, no risk to eye, easy to update, corrects all typesVisual field restriction, fogging, inconvenience for sports
Contact LensesBetter cosmesis, full visual field, good for sportsInfection risk if hygiene poor, dry eyes, not for all cornea types
LASIK / Laser SurgerySpectacle/lens independence, quick recoveryRequires suitable cornea thickness & stable power, cost, not reversible
ICL (Implantable lens)Suits thin corneas, reversible, excellent qualitySurgical risk, cost, requires specialist assessment

The best option depends on your age, power, corneal thickness, and lifestyle. Dr. Laavanyaa will assess your eyes and discuss the most appropriate solution for you.

Children's Eye Health & Myopia Control குழந்தைகள் கண் ஆரோக்கியம் மற்றும் Myopia கட்டுப்பாடு

Children's refractive errors are very common, often undetected. A child who cannot see the board in school may not volunteer this information — they assume everyone sees the same way.

Warning signs in children

  • Sitting too close to the TV or screen
  • Squinting to see the board or distant objects
  • Frequent headaches, especially after school
  • One eye turning in or out (possible amblyopia — lazy eye)
  • Poor academic performance despite effort

Myopia progression in children

Myopia often worsens rapidly between ages 8 and 18. Strategies to slow progression include:

  • Outdoor time: At least 90 minutes of outdoor activity daily has been shown to slow myopia progression
  • Atropine eye drops: Low-concentration atropine drops (0.01%) at night — proven to slow myopia progression
  • Orthokeratology (Ortho-K): Special contact lenses worn overnight to reshape the cornea temporarily
  • Myopia-control spectacle lenses: Specific lens designs (e.g. DIMS, MiSight) that reduce eye growth

First eye check: All children should have a complete eye examination before starting school (age 4–5) and annually thereafter. Early detection of amblyopia (lazy eye) before age 7–8 is critical for successful treatment.

Refractive Errors — Focus Points Normal Focus on retina Myopia Focus in front of retina Hyperopia Focus behind retina Astigmatism Two focal points ⇒ Concave lens ⇒ Convex lens ⇒ Cylindrical lens

Types of refractive error

Power Ranges (Approximate)
Mild Myopia ≤-3.00D
Moderate Myopia -3 to -6D
High Myopia ≥-6.00D
Mild Hyperopia +1 to +3D
Presbyopia add +1 to +3D

Need a Consultation?

Book an appointment with Dr. Laavanyaa at SRM Prime Hospital or P&G Multispeciality Hospital, Chennai.