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What is a refraction test?

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When the eye doctor is talking about 1 & 2 which is better back and forth all of that junk..

It is an attempt to determine, by trial and error using the patient's cooperation, the combination of lenses that will provide the best corrected visual acuity (BCVA).

It is a clinical examination used by optometrists, orthoptists and ophthalmologists to determine a patient's need for refractive correction, in the form of glasses or contact lenses. 

Following equipments are used for refraction testing:

  • Retinoscope or autorefractor
  • Trial frame 
  • Trial lens box including the pin hole and ocloder
  • Keratometer
  • Snellen chart
  • Slit lamp
  • Phoropter


Performing the test

Before commencing a refraction, ensure that:
The patient is seated at a 6-metre distance from the Smellen Chart. 
The illumination in the testing room is at a comfortable level of brightness for an indoor setting.

Setting up the patient

Comfortably fit the trial frame onto the patient, by adjusting the nose piece, Inter-pupillary Distance (IPD) and vertex diatance to ensure that they are properly centered.
A pinhole is then placed before the patient's eye, and their vision is then tested again. If the patient is able to read more lines on the Snellen chart with the use of the pinhole, this indicates the presence of refractive error.

Preliminaries

The examination begins by testing the patient's BCVA in both eyes separately, without correction. Conventionally, the right eye is tested first. An occluder is placed over the eye that is not being tested.

Objective Refraction

First of all, we will extract the value of objective refraction of the patient from the retinoscope or autorefractometer.
Suppose our objective refraction is this
           +3.00 / +1.00 x 180°


The Process Includes The Following Stages:

  1. Refining the sphere
  2. Refining the cylinder axis
  3. Refining the cylinder power
  4. Duochrome testing
  5. Binocular Balancing Test

Steps

The entire process of subjective refraction involves the patient fixating at the Snellen chart, whilst the clinican presents a variety of lenses and alters the power of the lenses in the trial frames according to the patient's subjective responses regarding improvements to their vision.




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