Accommodation - PDF

ACCOMMODATION Ariette Acevedo Rodríguez, O.D. PPO 4 Accommodation and Convergence To have efficient single binocular vision (SBV) we need: pt who don't have single binocular vision Well focused retinal images, OD and OS...

ACCOMMODATION Ariette Acevedo Rodríguez, O.D. PPO 4 Accommodation and Convergence To have efficient single binocular vision (SBV) we need: pt who don't have single binocular vision Well focused retinal images, OD and OS - amblyopia raise : strabismic refractive or causes : N 11 their fovea out of target Images of similar size and shape, OU - signif. strabismus won't fecus on for correctly a Images placed and maintained on each fovea OU - nystagmus Therefore, accommodation is needed to keep the near target clear and convergence is needed to keep it in place Requires binocular vision and image focus Accommodation and convergence both are linked neurologically through CN III & and must be coordinated for clear vision and stereopsis Accommodation & Sheard's Hot NPA is now it's measured Amplitude of Accommodation armeasured in D : minustoble Amount of accommodation a patient has measured in diopters Facility of Accommodation if missing either a , problem How much accommodation can be stimulated and relaxed & how easy to exect then relax Accommodative Response we read 30-50 om acc less blung =. How accurate is the accommodative response to a given stimulus acc. more=overexerting asthenopia, , HA All require clinical tests to determine the patients capacity to accommodate Accommodation Accommodation: Change in focal length of the optical system in response to a stimulus rigidity of Uns : NN , cause Mediated by the ciliary muscle and the crystalline lens age process as we , acc. Specified in accommodative stimulus and response Accommodative Stimulus e neas Accommodative Response Resting state of accommodation Lag of accommodation Lead of accommodation Clinical methods of measuring accommodative response (objective and subjective) Dynamic retinoscopy Binocular Crossed Cylinder test ala Fused word Cyl (FCC) (Bee)a Accommodative Stimulus Accommodation can be stimulated by: Placing an object closer than infinity, or closer than 6m or 20 ft. value b1c + By placing an object at 20ft. and using negative lenses report as positive acc. response is Both methods increase the vergence of the rays of light in the eye Expressed in diopters always that have no sigh Stimulus of Accommodation Examples 1. A test object that is at 1m, will stimulate 1.00D of accommodation 1M= 1/1= 1.00D or (1/100) x 100= 1.00D. OD 2. An emmetrope patient with a -2.00DS lens placed at spectacle plane, fixating at an object that is at 1m, how much is the stimulus of accommodation? (lem) ( Huget) - - 2 00. DS = z 000 (new much stim acc..? 1. 00 + 2 00. = 3 D. 7/1 = 1D obj relaxed emmetrope = no acc , being induced or uncorrected if uncorrected , they ar over accomm., + 3D hyperope they've , acc. + 3D hyperope = no accomm.; -1 500 uncorrected e 17 -D myope = myope. cloc to will acc ? bringing 1 50. , Stimulus of Accommodation Examples 2. An emmetrope patient with a -2.00DS lens placed at spectacle plane, fixating at an object that is at 1m, how much is the stimulus of accommodation? An object at 1m = 1.00D of accommodation -2.00D lens stimulates 2.00D of accommodation 1 + 2 =3D stimulus of accommodation Stimulus of Accommodation Examples 3. A -2.00D myope, uncorrected has a -4.00D lens placed on the spectacle plane. An object is presented at 1m. How much is the stimulus of accommodation? stimulus of acc obj 1 00D =.. uncorrected-2 , -4. 00 lens (placed in front) -> now we left - 2A uncorrected D 3D stimulu : 2 00D. + 1 00. = + if corrected - > -2D mype corrected 5-4 lens in front they were stimulus = OD + 4 + 1 = 5D Stimulus of Accommodation Examples 3. A -2.00D myope, uncorrected has a -4.00D lens placed on the spectacle plane. An object is presented at 1m. How much is the stimulus of accommodation? Stimulus of accommodation from object at 1m = 1D From lens at spectacle plane = 2.00D 1 + 2= 3.00D Accommodative Response Accommodative response: the response of the accommodative system when the eye changes fixation from one point in space to another The accommodative response should match the accommodative stimulus Linsonce cases not always Measured with: , pt's dx dysfunctions ornormal in depending response - Haploscope is mainly use Dynamic retinoscopy (MEM, Nott Retinoscopy, Bell Retinoscopy) Fused Crossed Cylinder (FCC)  Targete 40 cm : Accommodative Response Dynamic retinoscopy (near retinoscopy) Used to determine accommodative response to an accommodative stimulus at near & don't measure Lead or lag of accommodation ~ ↳ do measur Different methods: Nott, Bell, MEM Fused Crossed Cylinder (FCC) or Binocular Cross Cylinder (BCC): subjective testing Performed at 40cm Patient responds when both sets of lines are equally distinct, while adding + lenses Lag vs Lead of accommodation Lag: the accommodative response that the patient has is less than the required for the presented stimulus Lead: the accommodative response that the patient has is more than the required for the presented stimulus Using dynamic retinoscopy and BCC expected results: Young patients: lag is between +0.25D to +0.75D ±0.50D Presbyope: these test will provide an estimate of the required near addition * target e 40cm : 1 50 50 D ? Dlag 2 ,.. Lead or lag results interpretation If > +0.75D = LAG If < +0.25D = LEAD Under corrected hyperope Under corrected myope or overplus Over-corrected myope Spasm of accommodation Accommodative dysfunction Near exophoria (XP’) Near esophoria (EP’) If > 2.00 presbyopia  Latent it's hidden & weren't hyperopia : unable to relax Monocular Estimation Method (MEM) Performed in normal illumination Attach an MEM card to the retinoscope, according to the patient’s reading level Use the patients Harmon WD No phoropter Perform retinoscopy on each eye as the patient reads the letters/words on the card. Quickly place a plus or minus lens in front of the eye to neutralize the reflex Measure the reflex along the horizontal and vertical axis, and repeat with the other eye The expected values for the accommodative response for the MEM test are +0.25D to +0.75D Lag vs Lead of accommodation “control” Lag depends on the depth of focus of the eye or the depth of field Dim Light for FCC: dim, because depth of focus varied with pupil size and object size. Avoiding pupil constriction. Use a 40watts light bulb at 2 feet from near chart to stimulate the accommodation, keeping it sharp Meaning that the room is not totally dark. Turn off computer screen and VA projector screen  Lag vs Lead of accommodation “control” Lead: fogging lenses are used to minimize lead of accommodation (young patients tend to accommodate even at 20ft.) Overaccommodation is responsible of latent hyperopia and pseudomyopia, therefore it is necessary to compare results from the dry and wet refractions mu Cyclopentolate Before starting streak retinoscopy, fog or use the R lens Atropine - "best" , dilated for 5-7d i Homatropine scopalamine Tropicamide system stimless ? Accomm response. : respond to how does on acc. - a not same A how much amplitude of acc. - measuring Amplitude of Accommodation tests Donder’s Push up Using habitual SRx Target: one line above BVA of the tested eye Full illumination of target Occlude one eye, target in one hand, hold the ruler on the side of the patient's temple, at spectacle plane Move the target slowly toward the patient starting at 50-30cm away Have the patient report the 1st blur, but have them try and clear it, then resume Endpoint is when the patient cannot clear the target Record the distance and report in diopters Repeat the procedure in the other eye Use Hofstetter’s Formula to compare Donder’s Disadvantages Tends to overestimate Target subtends a greater angle as it gets closer (relative size magnification) Small mistakes in measurement lead to a large difference in diopters Presbyopic patients must wear their prescription for near and then subtract the NPA from your findings Example: A presbyope with an add of +2.50D, while wearing the spectacles the target was reported blurry at 25cm. NPA: 25cm = 4.00D AoA= 4.00-(+2.50) = 1.50D Sheard’s/ Minus to Blur Lens Performed monocularly. Target remains still. w/ MPMBVA SRx, one line above BVA, 40 cm distance in near rod and full illumination This testing distance already requires a 2.50D of accommodation Accommodation is stimulated with minus lenses Ask the patient to keep the letters clear and blink as necessary to keep them clear Add -0.25D lenses until patient reports sustained blur Repeat in the other eye and recheck each eye to make sure its still blurry Results: (-diopters obtained) + (-2.50D)= ⎸diopters ⎸ WITHOUT SIGN  21 point exam Example https://www.youtube.com/watch?v=HftXs30f138 don't have sign Zubj ref a OD + 2 50 -0 25 x 180 / : :... 0S : + 1 50. - 0 25. x180 WD = You & Sheald's : Clicks -> 25 (. 25 per dich so b. 25P) on zo 6 25 +. 2 50 -. = 8 75. point in pharopter end -- 3 75. wherept said you dodidea end can a then subt. it was benny 10 00 + 7 50 + /2 801 =. + 30 clicks 6 00 (7 50). OS endpoint. - :.. , 6 75 33 y10pt + acc. should be 15-0 25. (age) =. + expected. min so they've whin suspected Expected Amplitude of Accommodation Values Hofstetter’s Formula & Minimum expected: 15 – 0.25 (Age) Average expected: 18.5 – 0.30 (Age) Maximum expected: 25 – 0.40 (Age) Donder’s Age Amplitude Age Amplitude 10 14.00 45 3.50 15 12.00 50 2.50 20 10.00 55 1.75 25 8.50 60 1.00 30 7.00 65 0.50 35 5.50 70 0.25 40 4.50 75 0.00 AoA Testing Errors Depth of focus Time of reaction quick whenswitching lenses so they went be able to focus Patient delay Reference point for measurement (ruler) Instrumentation errors Practitioner bias - subj test. I be carefull Errors in dynamic retinoscopy Interpretation for Sheard’s and Donder’s traumatic brain. Orbino I ini Mac dys... dys. occlardisease Young patients may have lower values due to functional or pathological causes For patients age 40 or older in order to have clear and comfortable vision, an individual should have to use no more than half of their accommodation in sustained reading or close work Example If an emmetrope with a 40cm WD (requires a 2.50D of accommodation) Based on this rule they need at least 5.00D of AoA for comfortable and clear vision BUT according to Donder’s table a 40 y/o has approximately 4.50D of AoA, thus a NPA should be considered  Interpretation for Sheard’s and Donder’s NPAa Sheard's Example: ↑ Emmetrope patient who has 3.50D of AoA, should use 1.75D of their accommodative amplitude for sustained near work They should not have to use more than half of their accommodation in sustained reading or close work that is 3.50D/2 = 1.75 Same patient, working at 40cm, which requires 2.50D. For sustained near work, they have to use ½ of their AoA,which is 1.75D, thus the patient needs an additional 0.75D for comfortable and clear vision. In this case a NPA should be considered. This is an excellent rule for NPA prescribing for presbyopes AoA = 3 50D. NPA = +1 00 ADD ↑. 1 75D - should not use morethanthat Donder's = /2 (3 50). =. " is 0 75D they need 2 50D The diff.. 40cm , so want to reada.. they  Example 1. If the patient has 4.00D of AoA, they should use no more than 2.00D of accommodation for sustained near work If this patient wants to read at 40cm, how much NPA do they need if any? If the same patient wants to read at 33cm how much NPA do they need if any? If the same patient wants to read at 50cm how much NPA do they need if any? 2. If the patient has 1.00D of AoA and wants to read at 40cm, what is the NPA? If they want to read at 33cm, what is the NPA? - 4 00D. , should not use ? = 2.00D I should not be over 2 50). ADD 50D RX 50D - > +O >+ 1 00D = 240cm 2... , +1 25, they'll be 12 under so just give more plus) (ifax. e 33 em 3 33 D + + 1 33D. >+ 1 50D.. ,. e 50 cm , 2 00. D + D 70D Other accommodative test everything must addup Negative Relative Accommodation (NRA) Positive Relative Accommodation (PRA) test for facility ↑ to relax or stim. Fused Cross Cylinder Test (FCC) - test response new easy Facility of Accommodation (flippers) Monocular and binocular non-strabismic binoculardisorders It is important to evaluate not only accommodative system, but also binocular vision system since a patient with low AoA can be suffering from Accommodative Insufficiency which can lead to Convergence Insufficiency Negative Relative Accommodation (NRA) A measurement of the maximum ability to relax accommodation while maintaining clear, single binocular vision Using the subjective refraction (MPMBVA) ask to view one line above BCVA on near card at 40cm they mention it's blury as soon as , stop Add plus (+) lenses OU in +0.25D until the letters become blurry Sustained blur relax ? somesort of lag Normal expected values: +2.25D to +2.50D why ? accomm e 40cm - ThID. High NRA values Over minus, uncorrected hyperopia or latent hyperopia these tests : NRA before PRA then Sheard's * order for then stimulate relax accomm. first Positive Relative Accommodation (PRA) A measurement of the maximum ability to stimulate accommodation while maintaining clear, single binocular vision. Using the subjective refraction (MPMBVA) ask to view one line above BCVA on near card at 40cm Add negative (-) lenses OU in -0.25D steps until the letters become blurry Expected values: -1.75D to -2.00D High PRA values: diagnostic of accommodative excess Low PRA values: typically, below -1.50D could be accommodative insufficiency Flipper Bar Procedure: Accommodative Facility Test This is a measurement of accommodative facility Very important in children ages 7 and older who complain of distance blur but have 20/20 at distance Flippers have -2.00/+2.00 (commonly) Use distance rx, full illumination and near target at 40cm, use one line above BVA Have patient fixate on target Introduce the lenses, changing them as soon as the patient reports that letters are clear and can be read It is done monocularly for accommodation and binocularly for vergences Test can be done both monocular and binocular Flippers Continues One cycle is considered a +2.00/-2.00 and back to +2.00 Once the image is clear, lenses are flipped again, and image must be cleared again: this equals one cycle Test is done for 1 minute measured in cycles per minute Take notice if it takes to long to clear plus or minus lenses or both binocular failed monocular will fail if ↑ results: Expected , can pass meno. Efail binocula Monocular: 8cpm Binocular: 11cpm ↳ testing vergence function Interpretation of Accommodative Facility Test Patient fails monocular test: an accommodative problem Fails (+) lenses: accommodative excess (cannot relax) Fails (-) lenses: accommodative insufficiency (cannot stimulate) Fails both (+ & -) lenses: accommodative infacility (neither stimulate nor relax) Patient fails binocular, but passes monocular: vergence problem Fails (+) lenses: convergence insufficiency or basic exophoria Fails (-) lenses: convergence excess or basic esophoria Fails both (+ & -): fusional vergence dysfunction FCC/BCC Use the cross grid from Roto near char at 40cm Using distance SRx, if presbyopic you can use a tentative add Illumination from overhead lamp on target should be dim and placed at 2 feet from target, room illumination should be dim too Either use JCC or auxiliary +/- 0.50DC lens add tentative add acc Presbyepic pts don't this clearly you must to see so. age 55 ylo -> add -+1 25-1 50 D add E then Bad -..  BCC in phoropter JCC is introduced in front of both eyes even if they've not clicking just , want red dots &090 Minus axis at 090 (red dots oriented vertically) Patient is asked to observe the target and report Which set of lines are clearer, darker or sharper or if both sets of lines are equally clear, darker or sharper Que lineas son mas oscuras? Las horizontales, verticales or iguales? add- until vertical lines are darker If horizontal lines are darker plus lenses need to be added - * then add minus until both sets are clear o horizontal lines come clear again, 1st If vertical lines are darker minus lenses need to be added whichever comes this r don't measure lag of accommodation so we've doing but we not Ex : Plano e distance 17 clicks) horizontal + vertical : + 75. - 0 75 was. added 13 eichs) + 1 00. BCC BCC Interpretation If the patient accommodates exactly for the target position, the two set of lines + until vertical darles 3 then-until horizontal darkn both clear should be equally clear add are are or Endpoint of test no plano BCC If patient is underaccommodating for the target, as in presbyopia, the horizontal lines will appear clearer (darker) Start adding plus until the lines are all the same If patient is overaccommodating for the target, the vertical lines will appear clear (darker) 1. check for wrong illumination lawer ; ll um 2. verify overaccommodation BCC Interpretation To verify overaccommodation 1. Reverse the JCC so that the red dots are along the horizontal meridian Ask again which set of lines are darker If the vertical are still are still darker, stop the test Vertical preference nothing they just prefer vertical we can , line If the horizontal are now clear Add minus lenses It measures a lead of accommodation - BCC Interpretation Measures the amount of accommodation free of convergence at near under fused conditions Gives information concerning a lag of accommodation, like Dynamic retinoscopy (assuming not a presbyope, without using convergence) Can identify latent hyperopes - hidden accommodation, comes outin cyclo. (High Bee values can find lotent hyp. E overmined pos) Be careful with overminused patients at distance In presbyopes is a quick and convenient method to determine tentative add and use in other near testing Calculated Add Anomalies of Accommodation Presbyopia Spasm of accommodation Lag of accommodation Insufficiency of accommodation Fatigue of accommodation Paralysis of accommodation Presents with CN III palsy or medications Anomalies of Accommodation Presbyopia is UNIVERSAL Crystalline changes that continues to grow New fibers are formed in the outer cortex The older fibers are compressed in the nuclear Nucleus becomes LESS elastic Lens loses the ability to change shape as the ciliary muscle contracts Plus, the ciliary muscle loses contraction power with age Anomalies of Accommodation Presbyopia AoA decreases gradually until none is available by age 70 As discussed before, the rule of thumb… Patients 40 y/o and older in order to be able to obtain clear and comfortable vision, they should use no more…. Presbyopia Determine the Add Power According to age (tentative add) tables According to age Not all humans are equal OTC what are your thoughts? Tentative add by age and then TF Make changes according to how the material is held Tentative add, NRA and PRA Tentative add + difference in both Tentative ADD, BCC, NRA and PRA BCC + (NRA –PRA)/2 Presbyopia Determine the Add Power Estimated from patient’s age: Age Estimated Add (D) 40-45 +0.50 to +1.00 46-50 +1.25 to +1.75 51-55 +2.00 to +2.50 56-60 +2.50 to +2.75 61-65 +2.50 to +2.75 66-70 +2.50 to +2.75 70+ +2.50 and above  Accommodative Problems Accommodative insufficiency 15 glopthas +10 50 D. of accom. in each eye Low amplitude of accommodation for their age + 11. 25D- minimum High Bee dy enough insuff ifthey code : not to dx acc.. Versus not enough (t) so they need more in BCC Large lag of accommodative response had of + 8 00D.. accomm Fail the minus lens of monocular and binocular accommodative facility testing ↳ they stimulates accom Accommodative excess Normal amplitudes of accommodation Low lag or lead of accommodation for the accommodative response Fail the plus lens side of monocular andrelax binocular accommodative facility testing E do not like to I plus lenses relax accom. they & minus lenses Accommodative Problems looking I dist is harder to clear they mention when leading I near for a while ,. - distance to going from wear Accommodative infacility same back & Normal amplitude of accommodation chier nate copying from switching: forth from board b distance to a Normal accommodative response relax stimulate bic cannot fail both nor accom Difficulty with monocular and binocular ( + and -) accommodative facility testing Ill-sustained accommodation prolonged near tasks & cannot sustain it Normal amplitude of accommodation High lag of accommodative response Fail minus lens part of the monocular and binocular accommodative facility test - ↳ blo they can't keep itup-do well initially inflipper then prolong Accommodative Spasm Patient exerts more accommodation than required for the visual stimulus or is unable to relax accommodation all the time AKA hyperaccommodation (abnormally excessive accommodation) & Etiology: Uncorrected hyperopia, very prolonged near work, emotional problems (anxiety or stress), spasm of accommodation, uveitis, trigeminal neuralgia, syphilis, meningitis, head trauma, state of neurosis or pharmacological side effect (pilocarpine) constrict, pupil (miotic-accomm is countant > -. mioris , Usually associated with convergence excess - triad of becom.: convergence , accomm ovelacom. = Overconvergence Symptoms: Blurred vision at distance, asthenopia and often headaches Treatment: debatable ↑ Functional: plus lenses and facility exercise Organic: treat underlying cause ↳ meds., systemic diseases anxiety , , stres Pseudomyopia Defined as a reversible from of myopia that results from a spasm of the ciliary muscle The excessive accommodative response produces a apparent myopic shift that will disappear when a cycloplegic agent is administered to produce relaxation of accommodation * Myopia vs. Pseudomyopia Myopia Pseudomyopia Blur distance vision Blur distance vision Consistent vision Fluctuating vision Usually no headaches Headaches and asthenopia aggravated by near work Consistent retinoscopy Fluctuating retinoscopy Mid-dilated pupils Miotic pupils pinpoint pupils - suspect perdomyopia Exophoric tendency or latent hyperopia Esophoric tendency Similar manifestation on cycloplegic refraction Very different manifestation on cycloplegic refraction Psychogenic factors usually present stress anxiety,