HomeArticlesHow to Subjective Refract [ Sub – ENG ] – Refraction part 1
How to Subjective Refract [ Sub – ENG ] – Refraction part 1
November 7, 2019
Hi to everybody and welcome to OptoTubeChannel, the first Italian YouTubeChannel dedicated to Optometry Today let’s talk about subjective test also called max plus for the best visual acuity from far This is the test which finds the pluest lens which gives the best visual acuity from far This test is divided into three phases, the first which is monocular in which we have to find the max plus also for the right and left eye in this sequence; then the second phase which is the biocular phase in which we have to balance the perceptions of the two visual channels when there’s no fusion Then we have binocular phase in which both visual channels are activated and fusion is activated so a phase with a binocular vision. This test starts from monocular phase in which we have to occlude the non active visual channel, for example if we start with the right eye, we have to occlude the left Let’s start from objective data which could be static retinoscopy or autorefractometer so we have to insert the lenses combination that we have found in objective refraction on the trial frame or in the phoropter, and let’s blur adding plus lenses until the patient will have a visual acuity that is the half of the visual acuity in his/her habitual condition For example if after static retinoscopy I found -1.00D for both eyes with a visual acuity of 8/10 so I will blur until the patient will have a visual acuity of 4/10; after that I’ll be able to start. So we have to say to the patient to read, encouraging him/her when he/she has some difficult and gratifing him/her when he/she can read. If is absolutely not possible for the patient to read we have to subtract 0.25D until the patient will get his/her monocular best visual acuity. So the lenses combination which remains into the phoropter o into the trial frame and get the best visual acuity from far, is the max plus. After that I made this for the right eye, we have to occlude the right eye and open left eye and make back the entire procedure for the left eye. When we have found the max plus for the left eye too, we have to go on the next phase which is the biocular phase. In this phase we have to dissociate binocular vision by prisms which is the most used method, so we have to insert prisms on both eyes, 3 base up diopters on the right eye and 3 base down on the left eye. So a target which is an horizontal letters row, will be seen double, dissociated vertically So the patient is invited to say which is the better perception between these two, obviously after we have put the blur about of +0.50 – +0.75D. So if the patient says that the best perception is the low row we will add plus lenses to get worsen that perception. Once we got balance, we can remove prisms and blur and go on to the binocular phase. If isn’t like that, we will add minus lenses to the eye which has the worst perception, so in this example the left eye. Got the balance, we have to remove prisms and blur and go on to the binocular phase. Once we reached binocular phase, which is the last, we have to add blur about of +1.00D – +1.50D , and we can add minus binocularly when, during the reading, the parient has difficults The plusest lenses set in the phoropter or in the trial frame, are the binocular max plus from far. There are many methods to refract which are foveal suspension, this method, polarized method and other… So this is all for this video, if you liked subscribe my channel and leave a like! Let’s see at the next opto-video! OPTO-STYLE!!!