Clinical Refraction Procedure

Presented by

T.Muthuramalingam

Introduction

It is a combination of adequate examination and correction of vision .

According to eye care system clinical refraction is used to described the process of measuring a patients refractive error and determining the optical correction needed to provide patients with clear vision.

History taking Usually the optometry history should included

the following:- Chief complaint History of comfort ness with glass.

( if any) Family history of ocular disorder

(myopic , blindness,squint) Occupation

General Information Are essential facts that should be noted Include patient Name,Address,Age and

occupation Any allergy to drugs

Complaints related with vision Chief complaint should be noted first for which

patients has come to hospital. Vision related complaints can be pain ,loss of vision,

eye fatigue and blurred vision. For all these question ask the duration, date of

unset,sudden or gradual loss.

History of using glass

Duration of glass used. About of type of lens(glass or plastics) Present problem with glass(if any) Note the condition of glass like frame

alignment, scratches in lens etc.

Preliminary eye examination It is done to record any gross abnormality by using

torch light Position and size of eye balls and orbital socket. Position and size of eye lids and its margins and

lashes. Surface of cornea, its shape,size, opacities. Position and color of Iris. Ocular movement. Pupillary action, size-dilated or not dilated. Lens clear or opacity,aphakia or pseudophakia.

Preliminary vision assessment

It is done for finding out the existing vision . Check vision monocularly unaided and aided. Make sure whether patients is comfortable with

present glass or not. Decide whether the refraction is needed or not

Objective refraction It is done by streak retinoscope To determine objectively the actual refractive error

of patients. It is done monocularly by trial lens method It include following steps

Positioning and alignment of patients. Maintained the proper working distance Observing the retinal reflex (with or against movement. Finding the neutrality point using the appropriate lens.

Indication for Auto refraction

One who suspected to have high power in retinoscopy

The uncooperative patients while doing retinoscopy

One who comes for glass first time particularly children

All astigmatic patients having above 1D cylinder

Subjective refraction

Verification of findings obtained from retinoscopy with patients.

Always proceed the subjective refraction monocularly and also check the binocular comfortness.

Confirm the unaided vision first and proceed the lens accordingly

Find out the spherical improvement first to avoid unwanted cylinder

Add cylinder to correct the remaining. Apply supplementary test to confirm the final prescription

Indication of Cycloplegic refraction

All hypropes having the age group. One who complains of Asthenopic symptoms. Who come for glass for first time Accommodation is abnormally active.

Near vision assessment The near vision test is preferably done at 40cm by aging

method It is done with distance vision correction that is with

patients emmetropic level. Determine the correction depend upon the comfortness,

working distance, visual need of patients along with aging method.

Always check the unaided improvement first to find better correction. E.g. if pt’s with good reading speed indicates the under

correction.

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Prescription writing

It should be clearly written regarding the sign and cylinder axis.

Transpose the prescription with plus cylinder to provide comfortness to patients.

Measure and write the IPD properly. Mention the advice given to patients

regarding lens design.

Advice to patient

Advice properly Instruct the patients how to use the glass

(dist. Near,constantly) Counsel the patients about the difficulties and

limitation of lenses. E.g: slow adaptation in PAL, jumping effect in

bifocal.

Instruction to optician

Recommended only flat top bifocal for constant uses.

Advice only the plastics lens for safety reasons specially for children.