Subjective Refraction Best Sphere PDF

SUBJECTIVE REFRACTION: PART 1: BEST SPHERE OTMS 2613 N RAWAT  OUTCOMES FOR THE UNIT: Describe the different components of subjective Correctly perform fogging technique using the phoropter refraction Explain the different ins...

SUBJECTIVE REFRACTION: PART 1: BEST SPHERE OTMS 2613 N RAWAT  OUTCOMES FOR THE UNIT: Describe the different components of subjective Correctly perform fogging technique using the phoropter refraction Explain the different instructions/questions asked during best sphere techniques and their purpose Explain the purpose of spherical error determination List the common errors encountered during best sphere Describe the plus/minus technique technique and how to avoid them Describe the fogging technique Explain how the technique must be adapted dependent on the visual acuity found after retinoscopy Describe the equipment required for best sphere techniques Describe the implication of visual acuity that does not improve during spherical error determination Explain the setup for best sphere techniques Explain the circle of least confusion and how it relates Correctly perform plus/minus technique using the to subjective refraction phoropter and trial frame CLASS PREP PURPOSE OF SUBJECTIVE REFRACTION PURPOSE AND INSTRUCTION TO THE PATIENT I will place various lenses in front of your eye to find the lenses that give you the best vision PLUS/MINUS TECHNIQUE  PURPOSE AND INSTRUCTION TO THE PX “I will present different lenses to you, please tell me which lens makes the letters appear clear.” “Please look at the letters on the screen.” When using a trial frame, it is easier to pose the question as, “are the letters clearer with the lens or without the lens?” When using a phoropter, it is preferrable to use numbers when offering: Do not use the same numbers repeatedly Start at 1 and go up to 10, then start back at 1, if necessary “are the letters clearer with lens 1 or lens 2?” EQUIPMENT REQUIRED Either trial Distance visual frame + trial Or Phoropter acuity chart case SETUP Room lights on Target is the line above best VA (isolated, if possible) However, if your patient has pinpoint pupils in normal room However, the smallest line that should be used as a target is illumination, you may consider refracting in a dim room. 6/6. This is due to the effect of pinhole and depth of focus. By This means that if the VA after Ret is 6/3,8, do not use 6/4,8 performing refraction in a dim room, more accurate results can as a target. Use 6/6 line instead. be found. NB. Full retinoscopy findings remain in front of px and px is monocular during subjective refraction PROCEDURE THIS TECHNIQUE INVOLVES OFFERING THE EACH TIME YOU WILL PRESENT TWO OF THE TWO OPTIONS, WE WILL PRESENT PATIENT DIFFERENT LENSES IN ORDER TO OPTIONS ONLY. THE MOST POSITIVE OPTION FIRST. THIS IS SEE WHICH LENS THE PATIENT PREFERS. BECAUSE WE WANT TO ENSURE THAT WE LEAVE PATIENTS ON MAXIMUM PLUS.  PROCEDURE SEE STEP-BY-STEP GUIDE, VIDEOS AND PRACTICAL MANUAL FOR DETAILED NOTES REMEMBER If your patient’s VA after retinoscopy is 6/15 or worse, you may use a 0.50D lens as a testing power (probe) lens. If your patient’s VA after retinoscopy is 6/24 or worse, you may use a 0.75D or a 1.00D testing power (probe) lens. As the VA improves, you can lower the power of your testing lenses. If your patient’s VA is 6/12 or better, you may only use an 0.25D testing lens. TIPS AND Ensure that you are consistently checking VA throughout your Subjective TRICKS Refraction, VA should be checked for at least every 0.50 change in Rx Especially with px choosing minus lenses, ensure that the VA is improving Should be moved quickly and precisely, allowing enough time in each position for px to make a decision Usually need to repeat this process a number of times in order for px to confirm result When offering minus lenses, Do not hold the minus lens in front of the eye too long. (present it and remove it as minus lenses stimulate accommodation)*** MAX PLUS MAX VA E.g. -2,00 (6/6) Best sphere Continues to accept minus.. -2,50 (6/6) ➔ OVERMINUSSED PLUS MINUS→ AWARE OF THE VA, CAUTIOUS OF THE RX  COMMON Poor handling of lenses Ensure there is no tilt to the lens ERRORS Ensure that the lenses are clean Presenting the options too quickly for the patient to make a choice When using the Trial frame, do not simply insert your probe lens into the frame You need to change the sphere lens and keep using that probe lens. KEEP YOUR TRIAL CASE CLOSE BY  It is very easy to over-minus/under-plus patients when doing Plus/minus techniques. COMMON It is important that you are constantly aware of the Patient’s Rx and VA ERRORS E.g. of Overminussing (THE MYOPE): Ret: OD -2,00 (6/6) ➔ -3,00 SPEX (6/6) (OVERMINUS) During best sphere, px continues to take more minus (which makes the text smaller and darker) But if you do not ask, you could over-minus the patients E.g. of under-plussing (THE HYPEROPE) Ret: OD +2,00 (6/6) ➔ +1,00 SPEX (UNDERPLUS) During Plus/minus technique, px keeps choosing minus → OD +1,00 (6/6) Yes, px is still reading 6/6→ but is that Rx their MPMVA?  FOGGING TECHNIQUE ALTERNATIVE TO PLUS/MINUS FOGGING TECHNIQUE Fogging techniques is usually performed when retinoscopy was difficult, not done or suspected to be highly inaccurate. Can only be performed in the phoropter Very helpful technique to ensure that you do not over-minus/under-plus your patients!!! PURPOSE AND INSTRUCTION TO THE PX “Please look at the letters on the screen” “I am going to change the lenses and the letters will become blurry” “As we go through the test, the letters will become clearer” EQUIPMENT REQUIRED Distance visual Phoropter ONLY acuity chart (Full chart) SETUP Room lights on Start: Target INITIALLY is four lines above best VA However, if your patient has pinpoint pupils in normal room During this technique, a fogging lens is added. This must blur illumination, you may consider refracting in a dim room. the patient by FOUR LINES! This is due to the effect of pinhole and depth of focus. By Thereafter, as the fog is removed, the patient’s VA will performing refraction in a dim room, more accurate results can improve. be found. NB. Full retinoscopy findings remain in front of px and px is monocular during subjective refraction PROCEDURE THIS TECHNIQUE INVOLVES USE OF A IF THE +1,00DS DOES NOT FOG BY 4 LINES, ONCE FOGGED BY 4 LINES, THE FOG MUST FOGGING LENS. USUALLY A +1,00 FOGGING ADD MORE PLUS UNTIL FOUR LINES ARE BE DECREASED IN 0,25 STEPS AS THE PX IS LENS WILL CAUSE 4 LINES TO BECOME FOGGED. ENCOURAGED TO READ LETTERS UNTIL A BLURRY → 6/12 CONFIDENT 6/6 LINE IS READ  PROCEDURE SEE STEP-BY-STEP GUIDE, VIDEOS AND PRACTICAL MANUAL FOR DETAILED NOTES RECORDING No recording is done at the end of Best sphere (either fogging or plus/minus) Following Retinoscopy, is the subjective refraction and the Final Rx This means that we do not record after best sphere/ Duochrome End of JCC OD ➔ goal 6/6 VA. If you are not 6/6 → attempt pinhole VA. End of JCC OS ➔ goal 6/6 VA. Record Subjective refraction at the end of JCC OS Then perform Binocular balancing and record Final Rx. Subjective Refraction is always done for OD, then OS, i.e. Best Sphere, Duochrome and JCC for OD and then Best Sphere, Duochrome and JCC for OS  2nd problem list: Xx Xx Xxx Retinoscopy: OD -2,00 (6/6) OS -1,75/-0,25x180 (6/6) After JCC Subjective Rx: * Remember to also consider Pinhole, if OD 6/6 not achieved OS Final Rx: OD After BB OS