Subjective Refraction JCC PDF

Subjective Refraction: Part 3: Astigmatic correction OTMS2613 N RAWAT OUTCOMES FOR THE UNIT: State the different methods that can be used to determine astigmatic component subjectively Explain the appearance, setup and use of the Stenopaic slit Explain the appe...

Subjective Refraction: Part 3: Astigmatic correction OTMS2613 N RAWAT OUTCOMES FOR THE UNIT: State the different methods that can be used to determine astigmatic component subjectively Explain the appearance, setup and use of the Stenopaic slit Explain the appearance, setup and use of the fan/block to determine axis of cylinder Describe the Jackson Cross Cylinder Explain the purpose of the JCC technique Describe the JCC procedure when a cylinder was/was not found on Retinoscopy Explain the setup for JCC technique Correctly perform JCC technique using the phoropter and trial frame List the common errors encountered during JCC technique Explain and apply the sphere modification rule Compare the JCC and fan/block method  SUBJECTIVE REFRACTION SEQUENCE OF TESTS Objective refraction Retinoscopy Sphere determination Best sphere: Either Fogging technique OR Plus/minus technique Duochrome technique Cylinder determination Jackson Cross Cylinder (JCC) Binocular balancingPerform one of the four binocular balancing techniques you will learn about It is possible to fully complete subjective refraction either in a trial frame or using the phoropter. However, where there is a choice, some techniques can only be performed in the phoropter. UNIT 2: CLASS PREP  ASTIGMATIC CORRECTION Performed after Spherical refinement to ensure that COLC is on the retina PREVALENCE EFFECT ON VISION 33% of people have no cylinder Many people can still have 6/6 33% of people have approx. 0,25- vision and have an 0,25/0,50DC 0,50DC Stenopaic slit Our focus tends to be on JCC Fan and Block method (which is performed most often in JCC our clinics) DIFFERENT TECHNIQUES UNIT 4: CLASS PREP  JCC: PROCEDURE OVERVIEW NO CYLINDER FOUND CYLINDER FOUND ON ON RETINOSCOPY: RETINOSCOPY: START HERE START HERE Refine Refine Bracketing axis power Why do we only perform Bracketing if NO cyl was UNIT 4 : C L A S S found PREP on Ret? Purpose Sensitive method used to determine power and axis of cylinder Can be used to refine high and low levels of astigmatism Equipment required Phoropter OR Trial frame+trial case Spectrum or Projector Can be performed without Spectrum/Projector Please print circular targets Setup Patient is seated with Rx (following on from Room lights on Duochrome)  Procedure NO CYLINDER FOUND CYLINDER FOUND ON ON RETINOSCOPY: RETINOSCOPY: START HERE START HERE Refine Refine Bracketing axis power Why do we only perform Bracketing if NO cyl was found on Ret? Bracketing Purpose Purpose and instruction to the patient When no cylinder is found on Ret, “Is the letter CLEARER with lens 1 or lens Bracketing is used to narrow down the axis 2?” Target: letter or letters (at least one line above best VA) Bracketing +1st question +Present red markings of JCC – axis 90 (lens 1) +Present red markings of JCC – axis 180 (lens 2) Bracketing +2nd question +Present red markings of JCC – axis 135 (lens 3) +Present red markings of JCC – axis 45 (lens 4) Bracketing +Based on the patient’s responses, we have narrowed down the axis of the possible cylinder (remember this is because we did not find a cyl on ret) +Patient chooses 1 and 3 ➔ axis is between 90 and 135 +Patient chooses 2 and 4 ➔ axis is between ____ and ____ +Patient chooses 1 and 4 ➔ axis is between ____ and ____ +Patient chooses 2 and 3 ➔ axis is between ____ and ____ Bracketing +Next level… +Patient chooses “1” and “same” (when asked to choose between 3 and 4) ➔ ? +Patient chooses “same” (when asked to choose between 1 and 2) and “3” ➔ ? Bracketing +Must conclude bracketing by +INSERTING A -0,25 CYLINDER ANYWHERE WITHIN THE BRACKET FOUND Refine axis Purpose Purpose and instruction to the patient Refine the axis that has been found on “Is the letter/circle ROUNDER with lens 1 or Bracketing or that you found on Ret lens 2?” Target: circular letter or set of circles (must be a round target) Refine axis +When the handle of the JCC is placed in line with the axis of the cylinder, the red markings of the JCC fall on either side of the axis of the cylinder Refine axis +This helps us to determine in which direction to rotate the axis of the cylinder +Patient chooses left, then we rotate the cylinder in the trial frame to the left Refine axis 15—10—5 15—10—10—10….5 On the second question, patient On the second question, patient reverses direction (compared to continues in the same direction as the first question) the first question Refine axis 15—10—5 15—10—10—10….5 On the second question, patient reverses On the second question, patient continues in direction (compared to the first question) the same direction as the first question They have narrowed themselves into this little Patient continuing in one direction section Continue moving in 10 degree steps Usually concludes in 3 questions Upon first reversal, change by 5 degrees and stop  Refine axis +Concludes by narrowing down the axis of the cylinder to the closest 5 degrees. Refine power Purpose Purpose and instruction to the patient Refine the power of the cylinder “Is the letter CLEARER with lens 1 or lens 2?” Target: single letter or line of letters (at least one line above best VA) Refine power +When the markings of the JCC are in line with the markings of the cylinder +In this way, we are able to offer plus (black/white) or minus (red) Refine power +If the patient chooses plus, we change the lens in the trial frame by adding plus +If the patient chooses minus, we change the lens in the trial frame by adding minus Refine power +Patient chooses the same lens twice? +Sphere modification rule +For every 0,50DC change 0,50 DC 0,25 DS adjust sphere by 0,25DS in the OPPOSITE direction Refine power +Patient chooses the same lens twice? +Sphere modification rule +For every 0,50DC change, adjust sphere by 0,25DS in the OPPOSITE direction +E.g. Rx after Duochrome: OD +0,75/-0,50x180 During JCC, patient chooses red. Rx will change to _______________ Patient chooses red again, Rx will change to ____________________ +E.g. Rx after Duochrome: OS -0,25/-1,00x180 During JCC, patient chooses white. Rx will change to _____________ Patient chooses white again, Rx will change to __________________  Refine power “same” patient reverses Stop there without making any Immediately offer the patient the changes lens that caused the reversal or without it If the px chooses the lens that caused reversal: change the lens If the px chooses “without”: stop without making any changes Refine power +Next level.. +E.g. Rx after Duochrome: OD +0,50/-0,50x90 Patient chooses white, Rx will be __________________ Patient chooses white, Rx will be __________________ Do we need to offer again? What is the endpoint when refining power during JCC? Refine power +Next level.. +E.g. Rx after Duochrome: OD +0,75/-0,25x90 Patient chooses white, you change the Rx to read __________ When you offer again, patient chooses white at current axis again. What could this mean? Common Errors + Using a fast presentation time + Using different presentation time for 2 options + Making large changes in axis to patient with high astigmatism + Continuously changing cylinder power without checking VA