+91 701-691-2180 [email protected] Time: Morning 10:00am to 1:00pm, Evening 5:00pm to 8:00pm (Sunday Closed) International Patients

Home Patients' Zone Patient Leaflets Biometry Before Cataract Surgery

Biometry Before Cataract Surgery

How the power of your new lens is calculated

Before cataract surgery, the eye is measured carefully so the surgeon can choose the right power for the lens implant (IOL). Accurate biometry is the main reason most people see well without distance glasses after modern cataract surgery.

What is measured

  • Axial length: the length of the eye from front to back
  • Keratometry: the curve of the cornea
  • Front chamber depth, lens thickness and corneal diameter on modern machines

How it is done

  1. Optical biometry: you look at a light in a machine for a few seconds per eye. Nothing touches the eye.
  2. If the cataract is too dense, ultrasound biometry (A-scan) is used with a probe after numbing drops.
  3. Both eyes are measured and compared; unusual results are repeated.

Before the test

  • Stop contact lenses before biometry: soft lenses for at least 1 to 2 weeks and rigid (RGP) lenses for longer, as advised, because lenses change the corneal shape.
  • Tell us if you have had LASIK or other refractive surgery: special formulas are needed, and old records help.
  • Treat dry eye first if advised; a dry surface gives inaccurate readings.

Choosing your target

Most people aim for clear distance vision and use reading glasses. Some choose monovision, or premium lenses for more spectacle independence, and people with astigmatism may benefit from a toric lens. Your surgeon will discuss the options; see our lens types guide and cataract packages.

Frequently asked questions

Why are both eyes measured if only one is being operated?

Comparing the eyes helps catch measurement errors and plan a balanced result between the eyes.

Why must I stop contact lenses?

Lenses flatten or reshape the cornea temporarily, which would lead to the wrong lens power.

Can biometry be wrong?

Modern biometry is very accurate, but unusual eyes and previous LASIK make it harder. Results are always checked.

Is biometry painful?

Optical biometry is touch-free. Ultrasound biometry uses numbing drops and is painless.

Related: Cataract Surgery in Ahmedabad, IOL Lens Types Explained: Monofocal to Trifocal, Pre-Operative Guide: Cataract & LASIK Surgery.

This leaflet gives general information and does not replace advice from your own eye doctor. Reviewed by Dr. Dhaval Patel, MD (Ophthalmology, AIIMS New Delhi), November 2026.

Questions about this?

Sadbhaav Eye & Dental Clinic, Motera, Ahmedabad. Dr. Dhaval Patel, MD (AIIMS New Delhi). Monday to Saturday, 10 am to 1 pm and 5 pm to 8 pm. For a serious eye injury outside clinic hours, go to the nearest eye hospital or emergency department.

+91 70169 12180

Dedicated to Your Smile, Devoted to Your Sight

Where healthy eyes and confident smiles come together.

Qualification from AIIMS

Eye care by an AIIMS-trained ophthalmologist; dental care by an MDS endodontist — both dedicated specialists in their respective fields.

Vast Experience

Dr. Dhaval Patel brings 15+ years of clinical experience since starting his ophthalmology residency at AIIMS, New Delhi in 2011.

Bilingual, Patient-Friendly Team

Our staff communicates comfortably in both Gujarati and English, so every step of your visit — from reception to aftercare instructions — is easy to follow.

International Camps

Dr Dhaval Patel has conducted many eye camps in Africa and visits yearly for the same.