Refraction STUDENT 24-25 PDF

OPT505: Clinical Skills and Refractive Management: Refraction Ellie Livings Order of refraction recap techniques Tips Understand optics behind refraction Apply to own routine  Tailor 3rd year & beyond refraction...

OPT505: Clinical Skills and Refractive Management: Refraction Ellie Livings Order of refraction recap techniques Tips Understand optics behind refraction Apply to own routine  Tailor 3rd year & beyond refraction to px Learn binocular OPT505 refraction Combine objective & subjective OPT408 Perform separate ret/subjective Component parts (x-cyl, BVS etc) Work cleanly and efficiently Use me! Working Cleanly R L R L Patient Management Patient fatigue Confusion Clarity of instructions Reassurance Pre/mis conceptions Working Cleanly: Clear Recording 1. Write clearly 2. Avoid using ° for cyl axis – can be confused with 0 3. Record in 0.25 steps for sph and cyl 5. Horizontal cyl axis are 180 not 0 6. Put units on Add or if it’s a sphere only ( DS) Write down results as you go, not at the end  Visual acuity Two things: 1) Don’t give the px too many lines every time you ask - Just use three, or even one if the VA is poor 2) Limit the number of times you ask - To establish initial vision/VA - After ret - After finished refining the sphere to confirm BCVA - If you do +1.00 blur - You can always ask ‘’are those letters still clear for you?’’  OZ-TJ-EU What’s the smallest line you can read?................ https://www.thomson-software- solutions.com/test-chart-xpert-3di/ When to stop? 6/6 6/6+1 6/4.8 6/3.8 Initial VA/Vis: you want a start point for When measuring VA-think refraction how much you want to push it for each stage of refraction: During testing: to confirm they can still see the letter to which you are directing them ‘can you still see those letters?’ Can be enough In research, VA testing is often standardised and includes a Final VA: this is where you really want to push termination rule. them e.g. ≥4 mistakes in a 5 line row Ametropia effects: What does the VA/Vis tell us? Snellen Decimal LogMAR Sph Blur Cyl Blur 6/6 1.0 0.00 0.25 0.50 6/9 0.67 0.18 0.50 1.00 6/12 0.50 0.30 0.75 1.50 6/18 0.33 0.48 1.00 2.00 6/24 0.25 0.60 1.25 2.50 6/36 0.17 0.78 1.75 3.50 6/60 0.10 1.00 2.50 5.00 3/36 0.08 1.08 3.00 6.00 3/60 0.05 1.38 4.00 8.00 1/24 0.04 1.38 4.50 9.00 1/36 0.03 1.56 5.75 11.50 1/60 0.02 1.78 7.50 15.00  Simulation of the influence of spherical refractive error (−0.75 DS) and with-the-rule (WTR), against-the-rule (ATR) and oblique astigmatic refractive errors (−1.50 DC) upon vision of a letter, a fan chart and a typical street scene O P K X O Read, SA, Vincent, SJ & Collins, MJ. The visual and functional impacts of astigmatism and its clinical management. Ophthalmic Physiol Opt 2014, 34, 267–294 The eye’s ametropia is the opposite of it’s correcting lenses… A myopic eye is too long/ too strong, It refracts the light too much and is too plus powered. We use a minus lens to diverge the light rays so that the myopic eye will focus them on the retina. A hyperopic eye is too short and weak, it doesn’t refract the light enough (unless accommodation is present to ‘pull’ the light onto the retina.) Positive lenses are used to create the extra plus power needed to focus the light rays onto the retina with no accommodative effort Astigmatism: Focal lines and circle of least confusion Myopic Astigmatism Hyperopic Astigmatism Mixed astigmatism  Objective: Retinoscopy Instant check of media: corneal, lens and vitreous opacities Idea of corneal regularity: keratoconus? Overview of pupil size and shape: anisocoria? Instantly know if px old spec rx is overminused (very helpful—many px come to see us dissatisfied with old specs—this is often why) Can tell if px accommodation is fluctuating/latent hyperope Can do other useful techniques: Mohindra, dynamic ret, ret people who can’t access autorefractor Will never be stumped if autorefractor breaks Will have a useful and lifelong skill—VAO, hospital, domiciliary… Why do we ask the patient to look at the green whilst we perform retinoscopy? It helps to relax the patients accommodation 0.44D Recap ret: Recap ret: Recap ret: Lean in=against Lean back= with neutral Collar up to flip  Tips for better ret: Tip no 1: read this book: John M. Corboy. The Retinoscopy Book: An Introductory Manual for Eye Care Professionals. (I have requested this via the library for this course’s reading list ) Get rid of your working lens Don’t stress about finding the right meridian Look at ‘ret troubleshooter’ on Moodle Practice! Refraction: what’s going on? +6.00DS +6.00DS +6.00DS Plano This is a power cross diagram This lens is not a sphere. It has power in representing a lens: it is a +6 one meridian only: cylinder sphere We need to know where the power is: Both principle meridians are how will we specify this? +6.00, and it’s +6.00 all the way round.  +6.00D This power profile can be expressed in several ways: Crossed cyls Minus cyl Plus cyl +8.00D This lens is not a sphere. It has a difference of 2D between the principle meridians. *Which optical condition of the eye is this used for? Crossed cyl: We have a Two cyls are given (+6.00 x180/+8.00 x 90) ‘phantom’ +6 sphere under this… +8 DC axis 90 Power = +6.00DC +6 +6 Power = +6 +6 +8.00DC +6DC axis 180 We just need an extra +2D to make up to +8D What we actually do is give a spherocylindrical lens……… Sphero-cylindrical lenses: +8.00 +6.00 -2.00DC (+2.00DC@90) @180 =+6.00 +6.00 +8.00 +2.00DC (-2.00DC @90= +8.00 @180) We can either: Or: lay down the most plus sphere first: +8.00DS lay down the least plus sphere first: +6.00DS Then add a minus cyl at 180 Then add a plus cyl at 90 Remember the cyl axis is plano, the power is Remember the cyl axis is plano, the power is perpendicular. perpendicular. So -2.00 acts at 90 degrees So +2.00 acts at 180 degrees This is: +8.00/-2.00 x 180 This is: +6.00/+2.00 x 90  Background learning: Read chapter 3 of Jalie on cylindrical and sphero- cylindrical lenses. Work through the examples on properties of crossed cylinders, sphero-cylindrical lenses and transposition. Make sure you can explain a sph/cyl/axis prescription on a power cross diagram as we have done today. Read the retinoscopy book ch4 Look at the ret simulator: https://aao-resources- enformehosting.s3.amazonaws.com/resources/Ped iatrics_Center/Retinoscopy-Simulator/ret.html  Procedure for monocular refraction. (Follow the red arrows) Retinoscopy Occlude LE Un-occlude LE LE RE LE BVS BVS X-cyl X-cyl Refine sph Refine sph VA VA Plus 1 blur Plus 1 blur Occlude RE Un-occlude, BEO New concepts Binocular Balance Binocular Add (+0.25DS)  BR-TY-RN Monocular v Binocular Refraction Monocular refraction Binocular Refraction RE & LE RE LE Binocular balance included Plus 1 Plus 1 blur blur Binocular Balance Binocular Add (+0.25DS) End goal of refraction: code:QA-KI-NL =point focus on or just behind retina ba b a  Subjective: BVS/circle of least confusion The whole point of refracting is to find the combination of lenses which give sharp and comfortable vision. We must keep circle of least confusion on the retina (or v slightly behind: ‘on the green’) comfort Clear vision Bear this in mind for every stage of the subjective We must control accommodation! Circle of least Control confusion on The eye should be relaxed, taking minimal effort to accommodation retina have BCVA Balance is key!  Subjective: Best Vision Sphere (BVS) Complete the next steps with the RIGHT eye first 1. With final objective rx in place, and lights on, check and record monocular distance VA. 2. Occlude the LE and perform BVS on the RE. Choose appropriate letter size (recommend 3 lines on chart, with the VA you just got in the middle) Offer +0.25DS Ask “Do the letters look better, about the same, or a bit worse?” Better or same: give plus and repeat question. Worse: they don’t want the plus, try minus Offer -0.25DS Ask ‘’Do the letters actually look better, or just smaller and darker?’’ Better: give the minus and repeat question Smaller /darker: No more minus. Offer the +0.25DS again once, just to check. End goal of refraction: code:QA-KI-NL =point focus on or just behind retina 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 -0.25DS Smaller and darker better  End goal of refraction: code:QA-KI-NL =point focus on or just behind retina 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 +0.25DS Better-----→ same worse Check BVS: Duochrome Used to check the best vision sphere during monocular refraction Patient should see the red and the green as equal OR the green as just clearer 0.44D Virtual refraction: Best Vision Sphere: examples After retinoscopy: After retinoscopy: R-3.50DS VA 6/9.5 R-5.00/-1.00 x 90 VA 6/6 All pre-presbyopic with no patholgy After retinoscopy: After retinoscopy: R+5.00/-0.75 x 90 VA6/7.6- R+3.50DS VA 6/6 https://www.aao.org/education/basic-skills/cross-cylinder- technique-basics-of-astigmatism-tes 02.20 to 7.33 Cross cyl Keep the BVS on the retina: Prevent errors Don’t forget to alter the sphere if you change the cyl (0.25 change in sphere for every 0.50 change in cyl) Beware the cyl-hoovering patient! Control accommodation. Make sure you tell them it’s ok not to be sure which option is clearer--. Reassure your px! If your cyl changes dramatically from ret (assuming your VA was OK) go back and re-check the BVS. Or, turn the lights off and use your ret to confirm the cyl is really there) Cross-Cyl: technique and tips Hold the cross cyl steady and level in front of the px’x eye Flip quickly but in a controlled way Always Offer plus first and DON’T linger on minus Lens 1…or 2…(flip to 1) pause. Lens 1…or 2… (flip to 1) pause Give them several ‘flips’ If they say ‘uummm…’ reassure them, there might be no difference and everyone finds this hard. ‘I’m showing you tiny changes’ Can’t decide= no difference as far as we’re concerned Always err on the side of less cyl Most people have cyls at either 90 (ish) 180(ish) or properly oblique ( 45/135) Recommend NOT saying ‘3 or 4’ (don’t give px to many choices) Use 5 degree changes for low-mod cyls, but remember high cyls are more axis dependant ( think of spec tolerances) Can actually refine cyl axis BEFORE BVS if cyl is very high ( about 4DC) then go back to BVS and proceed normally  OZ-TJ-EU Mistake!! Correction If you start X cyl routine WITH a cyl in place If there’s no cyl on ret, you show the X cyl @ 90 and 180 You DO NOT show 90, 180 and oblique axes If there’s a strong preference for one or the other, do not show oblique. NO NO NO! Give the preferred 0.25DC If px says the same, or not sure, show If there is a cyl in place already, you refine oblique options-give the preferred its axis 0.25DC Then check power FIRST to see if px rejects cyl completely. Refine the Sphere: After cross – cyl, you need to refine the sphere: VA should be pretty good If you have done it right, there should be minimal change at this point. -Remember, you left them slightly on the green (minus) going in, so they should accept minimal plus, if anything. Clinical decision making is important Use +1DS blur to check they blur back to an acceptable level. - This depends on their final acuity: 6/6→ 6/12 - Go on px comfort and acuity rather than rigid definition - May alter once you binocular balance (upcoming lecture)  Plus 1 blur code:QA-KI-NL 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 ? +1.00DS Plus 1 blur Who? Why? Intended Result Wrong answer? When not to use? pre- presbyopes! To check you VA blurs back Re-visit Presbyopes and have max about 3-4 refraction pseudophakes! (but…..) accepted plus lines Re-ret If you are doing To ensure So 6/6--> 6/12 Consider a cycloplegic patients ish cycloplegia refraction aren’t left over- *Later in your accommodati career* ng If you suspect latent hyperopia Pinhole Acuity: If the VA isn’t coming up and you don’t know why Recording: VA 6/18 NIPH Is the reduction due to ocular pathology or uncorrected Rx? VA 6/12, 6/6 PH Is the reduction due to ocular pathology or uncorrected Rx? Pinhole Acuity OZ-TJ-EU Filled out example: OZ-TJ-EU Not all boxes compulsory. Background learning: Read article ‘’subjective refraction’ in clinical resources tab on Moodle: https://dle.plymouth.ac.uk/pluginfile.php/3158853/mod_resourc e/content/2/subjective%20refraction%20CET%20article.pdf Read ch 1 & 2 of Investigative Techniques and Ocular Examination ( Doshi & Harvey) Read Ch. 4 of Primary Eye Care ( Elliott) Read the clinic lab books from 408 and 505 about this topic Further reading Grosvenor, T. (2007) Primary Care Optometry. 5th edn. St Louis, Mo: Butterworth-Heinemann/Elsevier. Elliot, D.B. (2014) Clinical Procedures in Primary Eye Care. 4th edn. Philadelphia: Saunders/Elsevier. Rosenfield, M. & Logan, N. (2009) Optometry: Science, Techniques and Clinical Management. 2nd edn. London: Butterworth- Heinemann/Elsevier Benjamin, W.J. (2006) Borish’s Clinical Refraction. 2nd edn. St Louis, Mo: Butterworth-Heinemann/Elsevier. Tunnacliffe, A.H. (1993) An introduction to visual optics. 4th edn. Canterbury : Association of British Dispensing Opticians Rabbetts, R.B. (2007) Bennett and Rabbetts' Clinical visual optics. 4th edn. Edinburgh : Butterworth-Heinemann/Elsevier