Subjective Refraction Binocular Balancing PDF

N RAWAT OTMS 2613 BINOCULAR BALANCING OUTCOMES FOR THE UNIT Describe the purpose of binocular balancing Describe the contraindications for binocular balancing Explain the different techniques that can be used to perform binocular balancing Explain the use and effect of prisms durin...

N RAWAT OTMS 2613 BINOCULAR BALANCING OUTCOMES FOR THE UNIT Describe the purpose of binocular balancing Describe the contraindications for binocular balancing Explain the different techniques that can be used to perform binocular balancing Explain the use and effect of prisms during binocular balancing techniques Explain the use of fogging lenses during HIC Explain the effect of added plus lenses during Prism Bichrome test Correctly perform different binocular balancing techniques Describe binocular refraction and its uses Correctly record findings following binocular balancing State possible reasons for not achieving 6/6 vision at the end of binocular balancing Describe ways to confirm reason for not achieving 6/6 vision at the end of binocular balancing CONTRAINDICATIONS What is the goal of Binocular balancing? So then, shouldn’t presbyopes be contraindicated from Binocular balancing? What about bilateral pseudophakes? What happens when we use prism? Image moves towards the __________ What is dissociation? Is this realistic? What would we be more realistic? PRISM TECHNIQUES ❖ Prism dissociation balance with fog ❖ Prism dissociation balance without fog ❖ Prism bichrome test Purpose and instruction to px “I am going to use special lenses, called prisms. This will cause you to see double. Please close your eyes (or I am going to close both eyes while I set up the prism).” “Now, with both eyes open, do you see double?” Equipment required Check Projector or Phoropter overview for Spectrum VA limitations See step-by-step guide, videos and practical manual for detailed notes Procedure Humphriss Immediate Contrast Test HIC: Introduction Use fogging lens to temporarily suspend central vision by blurring it to about 6/12 This creates a ‘psychological septum’ When the one eye is fogged, sharpness of vision is now dependent on the unfogged eye alone Binocular vision is still maintained through peripheral fusion as only central vision is fogged HIC: Introduction However, if a fogging lens is increased to +1,50D or more, binocular vision starts to collapse. You should not continue with the test if a fog of +1,50D or more is required This could that you have overminussed the myope or underplussed the hyperope HIC: Fogging lens Fogging lens used is typically +1,00 This can be increased to ensure that the px is fogged by 4 lines How should be we check to ensure that a px is fogged? Always important that 1 eye remains fogged throughout the test When moving from one eye to the next, insert the fog before removing the other eye’s fog. At any given time, one eye is always fogged HIC: Fogging lens Fogging lens used is typically +1,00 This can be increased to ensure that the px is fogged by 4 lines How should be we check to ensure that a px is fogged? Always important that 1 eye remains fogged throughout the test When moving from one eye to the next, insert the fog before removing the other eye’s fog. At any given time, one eye is always fogged HIC: Fogging lens Fogging lens used is typically +1,00 This can be increased to ensure that the px is fogged by 4 lines How should be we check to ensure that a px is fogged? Always important that 1 eye remains fogged throughout the test When moving from one eye to the next, insert the fog before removing the other eye’s fog. At any given time, one eye is always fogged HIC Instruction: “clear and comfortable” Purpose and instruction to the px Inform the px that you will be blurring one eye before you insert fogging lenses “Looking at the letters on the screen, are the letters clearer and comfortable with 1 (+0,25), 2 (-0,25) or 1 (+0,25)? Option 2 is shown for half the time for option 1 When using trial frame or phoropter, use numbers Equipment required Either trial Or Phoropter Distance visual frame + trial (still need loose acuity chart case +0,25/-0,25) Setup Room lights on Target is the line above best VA (isolated, if possible) However, if your patient has pinpoint pupils in However, the smallest line that should be used as a normal room illumination, you may consider target is 6/6. refracting in a dim room. This means that if the VA after Ret is 6/3,8, do not use This is due to the effect of pinhole and depth of 6/4,8 as a target. Use 6/6 line instead. focus. By performing refraction in a dim room, more accurate results can be found. NB. Subjective findings (at the end of JCC) remain in front of px Procedure THIS TECHNIQUE INVOLVES EACH TIME YOU WILL PRESENT TWO WE OFFER LENSES TO THE EYE THAT OFFERING THE PATIENT DIFFERENT OPTIONS ONLY, BUT IN THE IS NOT FOGGED LENSES IN ORDER TO SEE WHICH SEQUENCE 1/2/1 (OFFER THE PLUS LENS THE PATIENT PREFERS. TWICE)  Procedure See step-by-step guide. Videos and practical manual for detailed notes TIB (theory only) Turville Infinity Balance (TIB) 1946 Mirror is used with a removable vertical septum, white/black Width of septum is 30-35mm Effect of occluding strip is to divide the central portion of the test chart image into 2 separate monocular fields surrounded by a binocular field of view Spherical power is adjusted to give, if possible, equal acuity to both eyes Remember Following all Binocular Balancing techniques, you should only take Binocular VAs! However, as a student, if there has been a significant change in Rx (>0.50), you may take monocular VAs. As you become more proficient at subjective refraction, this step should not be necessary! At the end of Subjective refraction, DVA OD or OS is not 6/6… Causes Tests to check Incorrect refraction Pinhole VA***** Amblyopia Ophthalmoscopy Corneal distortion Reflex during Retinoscopy/Mires during Ocular disease (possible cataract/ARMD) Keratometry? Malingering? Other factors to consider… When choosing between two sph/cyl powers→ MPMVA If the cyl is large or significantly different from previous Rx→ Aniseikonia Change in power between old Rx and new Rx (0.75D sph, 0.50D cyl power, 10 degree axis) Other factors to consider… Generally, R and L Rx will be similar and cylindrical axes are symmetrical (R 170 L 10) As a general rule, if you have to choose between VA and visual comfort→ choose visual comfort. Patient in a trial frame- “real life” Ergonomic and practical considerations→ case history (visual needs, work environment, leisure activities) Other factors to consider… How do you know if you have overminussed/underplussed your patient? Quick check using +0,50DS REMEMBER goal is Maximum Plus For Maximum VA (MPMVA)