Page 34 - Practical-Refraction-English

D Final Check of Binocular Sphere, Subjective Subjective Refraction Vision Screening) Appreciation and Comfort (including Binocular separately and balanced one with the other, the front of both eyes. sphere must be confirmed binocularly. The patient’s 4 Finally, having determined the refraction of each eye 3) Now, in the same manner, place -0.25 D in a. If vision is worse, the refraction result in the binocular visual acuity may then be measured and trial frame is now correct. This is the final refraction. furthermore their subjective appreciation of the final prescription judged. b. If there is no change, the refraction result in the trial frame is correct or slightly over-minussed. Make a judgment whether or not to add the extra - Preferably, this final binocular verification of the 0.25D. Practical Refraction sphere should be performed using a trial frame to allow more natural visual and spatial conditions than c. If vision is better, the refraction is over-plus- those achieved when the patient is positioned sed or under-minussed: add -0.25 D and repeat step behind a phoropter. 3). If >-0.50 needs to be added, redo the refrac- tion. Have the patient look at distance at some small detail. Present ±0.50D and ±0.25D binocularly In summary, the response sought during binocular over the existing correction and ask the patient to verification of the sphere correction is a reduction of choose which lenses give the best vision. Record the clarity and comfort with an extra +0.25 D and an binocular visual acuity. absence of real change observed with an extra -0.25 D. The value of the sphere in the patient’s refraction Remember to take into account in the final prescription should be adjusted binocularly in order to obtain the fact that the subjective refraction has been perfor- this result. med at a finite distance and not at optical infinity. For this reason, when judging the final binocular sphere and comfort of the prescription, it is preferable to have the patient look outside, at the horizon. Indeed, the conven- tional test distance does not correspond to optical infi- Figure 31: Binocular Check of the Sphere, Subjective nity. Subjective refraction performed using a chart at a Appreciation and Comfort distance of 6m gives rise to an error of 1/6m = 0.16D; 5m to an error of 1/5m = 0.20D. Although these errors a) with +0.25D – vision is blurred are less than a prescribing increment of 0.25D, they are nonetheless potentially significant and may necessitate the adjustment of the final prescription by -0.25DS binocularly. The binocular sphere may be checked as follows: 1) Place the subjective refraction result in the trial frame and have the patient focus as far away as possi- ble (for example, on the horizon), looking with both eyes © Essilor International open. 2) Place an extra +0.25 D in front of both eyes b) with -0.25D – vision is unchanged (using a binocular lens holder) and ask the patient if this makes their vision ‘better, worse or no different’. a. If vision is worse, the refraction result in the trial frame is correct or over-plussed. Do not add the extra +0.25D to the refraction result. Go on to step 3). b. If there is no change, the refraction result in the trial frame is over-minussed or under-plussed; add the +0.25 D binocularly to the refraction result and repeat step 2). © Essilor International c. If vision is better, the refraction result in the trial frame is (even further) over-minussed or under-plussed; add +0.25 D and repeat step 2). If >+0.50 needs to be added, redo the refraction. 34 Copyright © 2008 ESSILOR ACADEMY EUROPE, 13 rue Moreau, 75012 Paris, France - All rights reserved – Do not copy or distribute.