Accommodation & Convergence Investigation & Management 5LMS0072 PDF

Accommodation & Convergence Investigation & Management 5LMS0072 ACS Angela Gulati-Roy MSC., BSc (Hons.), MCOptom, AFHEA University of Hertfordshire  Online lecture etiquette... Schedule a time in your day to listen & review this content Turn off all o...

Accommodation & Convergence Investigation & Management 5LMS0072 ACS Angela Gulati-Roy MSC., BSc (Hons.), MCOptom, AFHEA University of Hertfordshire  Online lecture etiquette... Schedule a time in your day to listen & review this content Turn off all other devices / remove distractions Don’t be PASSIVE  be inter-ACTIVE Note pad & pen (paper/electronic) Scheduled pauses for you to write notes / think about the answers ? Learning Outcomes What will I need to know ? Components of the near vision triad & interaction of elements Convergence & Accommodation – Investigation – Norms – Anomalies & their Management Relationship between accommodation & convergence Near vision triad The effort to focus on a NEAR object results in: 1. Accommodation  increased optical power of the eye to allow clear focus on a near object 2. Pupil constriction  increases depth of field/focus 3. Convergence  single fused object, essential to achieve & maintain binocular single vision Near (synkinetic) vision triad Provides Clear & Binocular Single Vision (BSV) Convergence III Cr.N Acc. Miosis CONVERGENCE  Convergence  The ability of the eyes to make a co- ordinated inward movement in response to a near target – A vergence movement – ‘ADDUCTION’ – Contraction of bilateral medial recti (IIIN) Convergence – 2 aspects Pursuit (ramp) Jump (step) Tracking movement Sudden change of in response to a slow fixation from 1 object moving target being to another brought towards the (at a different eyes distance) To maintain bi-foveal fixation & BSV  eyes must converge Convergence Cues/Stimuli Voluntary Tonic 1/3 convergence input – Tonus in EOM’s Fusional – Involuntary, to maintain BSV 2/3 convergence Accommodative input Proximal – In response to the ‘nearness’ of an object Near Point of Convergence (NPC) Method Recap Conventional ‘ramp’ or ‘push-up’ Find nearest point of BINOCULAR convergence Think WHEN? (is not ‘always’ a prelim test) Be intuitive re: target visibility Refractive error / level of VA ?? With / without specs ?? Is a BINOC test.  CAN NOT do if MANIFEST deviation ! fixation & recognising double is difficult with a very blurred target  target MUST be in focus NPC (ramp) - Method Recap Test high hypermetropes –  whilst wearing spectacles Test presbyopes –  whilst wearing spectacles – ? Multi-focals/bifocals post Rx (TF) Most myopes and low hypermetropes –  test without spectacles *NB: Base IN prisms due to lens edge will assist convergence (myope) NPC (ramp) - Method Recap Clear instructions Lights ON (target visibility) ‘Natural position’ Slow, steady speed ‘some’ blurring of the target is not relevant – The test does NOT examine accommodation Listen & Watch your px When convergence breaks the patient may: – Recognise PATHOLOGICAL diplopia  +ve diplopia response – Suppress (target still appears single)  no diplopia response  Subjective & Objective NPC – break point Subjective (LISTEN) Objective (WATCH) Patient reports Watch the patients eyes PATHOLOGICAL Observe when diplopia or target jump convergence breaks – May not be possible if suppressing Think ??? Does subj. NPC = obj. NPC? Did the patient report diplopia or suppress? Record: Note which eye diverges first NPC – what to measure & record After break point has been noted, withdraw target Note subjective recovery point  BSV (no diplopia) and/or note objective recovery point Note the mid point between convergence break & recovery If convergence is good & consistent – record the mean of 3 repeated measures – Note which eye breaks objectively (if seen) – Note if subjective comment reported NPC – what to measure & record If difference between break and recovery > 5 cm – record both break & recovery – May indicate convergence fatigue if >> difference Repeating the test can help identify fatigue effects – If convergence worsens by >1 cm with each attempt – Record the deterioration Expectation of results: Normal NPC  opinions vary approx. 6-10cms (up to 12cms) 12-15cms  suspect >15cms  intervention NB: with age Presbyopes may report target appears blurred before it is double – Continue to probe diplopia Consider developmental - px height (arm length) Jump (step) Convergence Look from distant target (50cms)  near target (15cms) Then vice versa Observe smooth VERGENCE movements of both eyes Abnormal if: No OR jerky vergence movement OR version movements are seen  Other test methods: To increase sensitivity of identifying subjective break point Use pen-torch to test convergence with a red filter over one eye OR pen-torch with red Px to report & green goggles appearance of 2 different coloured spotlights at break point CONVERGENCE DISORDERS Convergence disorders Convergence insufficiency – Remote near point of convergence Convergence fatigue – Tiring of convergence on sustained / repeated use Convergence inertia – Ill-sustained near point of convergence Convergence spasm – Inability to diverge the eyes or relax convergence Convergence paralysis Convergence insufficiency C. 1862 Von-Graefe Inability to maintain convergence for comfortable BSV @ near Common & ‘usually’ symptomatic UK  remote near point of convergence (NPC) USA  Remote NPC + convergence weakness exophoria (near)  Convergence dysfunction (all types): Usually highly symptomatic From failure to maintain BSV – Blurred vision (near) – Jumbling of words (near) – Intermittent crossed HORIZONTAL diplopia (near) – Relief reported when 1 eye is closed Convergence dysfunction (all types): Usually highly symptomatic Muscular fatigue: – Aesthenopia, periorbital tension Worse with prolonged close work May ease when eyes are closed / with rest – Difficulty changing focus D  N – Itching, burning, gritty eyes – Possible nasal conjunctival hyperaemia ? Convergence insufficiency Convergence insufficiency can be associated with: Anatomical – large PD, divergent anatomical position of rest Poor GH – General weakness – Thyroid eye disease (Moebius sign) – Psychological instability / anxiety / stress Age Urban lifestyle – Excessive close work (over-use) Disuse of accommodative convergence – Myopes reading without specs – New presbyopes with near specs – Newly corrected low hyperopes Convergence dysfunction: Insufficiency, fatigue or inertia Probe symptoms – particularly onset AND associations Diplopia (horizontal, intermittent) Headaches Aesthenopia NV Blur (intermittent) Monocular comfort (closing 1 eye) Consider potential causes of convergence dysfunction  Probe GH/medication/stress/fatigue Probe environmental factors Management of convergence dysfunction: Insufficiency, fatigue or inertia Visual hygiene advice ALWAYS TREAT Remove cause of dysfunctionWHEN SYMPTOMATIC Vision therapy  generally very responsive to exercises Refractive modification – pre-presbyopic myopes to wear specs for NV – Stimulate accommodative convergence – Some BASE IN from concave lenses Prisms (Base IN) may help as a short term solution NB: beware NO symptoms could = suppression  ALWAYS CHECK objective NPC  Simple NPC exercises Pencil to nose Near-far exercises exercise (jump or step) (push up or ramp) Focus clearly & singly start with remote on near target, then target & bring closer shift focus on to until diplopia/eye distant target diverges Keep alternating Repeat and continue distancenear keeping until able to sustain at target single & clear a normal near point When? 10 minutes/day, 2x daily (aim for 10cms) Review? @ 1/12 then stagger to 3-6/12 pending symptoms/ compliance/progress > Complex exercise = Physiological Diplopia Hold 2 pens in front of the patient; one closer to the face than the other The pen NOT being looked at should be seen as double Start with closer pen @40cms Continue to change fixation( DND), noting diplopia of non-fixated target each time (pause 3- 4 seconds) > effective (than ramp/jump) as physiological diplopia serves as a cue to ensuring no suppression BUT > complex for patient (compliance) Management of convergence spasm (rare) = ‘over’ convergence Usually associated with accommodative spasm Intermittent, episodic maximal convergence, associated pupillary miosis H/A, ocular discomfort, blurred vision & diplopia May be associated with esotropia with cross-fixation Management of convergence paralysis (rare) Complete FAILURE of convergence Sudden onset near diplopia & aesthenopia Accommodation ‘can’ be normal, often reduced or absent Associated with serious systemic disease / trauma Referral for neurological investigation & treatment of cause Head injury Encephalitis Brain tumours  Accommodation & Convergence Investigation & Management 5LMS0072 ACS Angela Gulati-Roy MSC., BSc.(Hons.), MCOptom, AFHEA University of Hertfordshire ACCOMMODATION Accommodation – recap Process to enable clear viewing of near objects Assessment of accommodation Subjective techniques: amplitude range facility Objective techniques: retinoscopy – static/dynamic auto-refractors Subjective assessment 1: Amplitude of accommodation (AoA) Near point of accommodation limit – Monocular & binocular near point of clear vision – RAF rule (preferred) or detailed target & tape measure – Normally slightly higher AoA binocularly – if >> monoc. assymmetry – ? Recheck refraction end points/binocular balance – ? check pupils (triad) ? pathology KNOW YOUR amplitude NORMS: (Donders, Duanes tables, dated & debated ?) Use FORMULAE: Hofstetter’s Formula’s  AoA = ‘near point’ of accommodation LIGHTS ON, Hygiene, Explain, RAF rule Monocular 1st, then binocular amplitude WITH FULLY CORRECTED BALANCED DISTANCE Rx in trial frame N5 custom on the first day of every Measure in dioptres N8 no room for him at any Target N5 or smallest visible print people from far N10 N12 for many hours Technique (conventional) – push up target until Px reports target blur – withdraw target until Px reports target clarity – repeat push up if difference < 2 cm record mean if difference > 2 cm record range AoA = ‘near point’ of accommodation on early presbyopes? If Amplitude < 2.00DS (50 cm) Ensure full distance prescription is worn – ‘could’ add additional +ve power enable initial view of target at 50cm e.g. +2.00DS Find near point – subtract additional power added from final result A reliable test & endpoint ? – depth of field – small pupils, increased depth of field – changing subjective criteria (definition/tolerance of blur) Subjective assessment 2: Range of accommodation = Limits of clear vision through plus & minus lenses – ability to clearly focus through +ve and -ve lenses – Monocular & binocular – Better monocularly Fixate target at constant viewing distance – Add +ve lenses of increasing power until target blur first noticed (maximal relaxation) – Add –ve lenses of increasing power until target blur first noticed (maximal exertion) Subjective assessment 3: Accommodative facility Symptom investigation: slow change in accom.  changing fixation distance DND Use flipper lenses pairs of plus & minus spherical lenses – +/-1.00DS; +/-1.50DS; +/-2.00DS – view near target (≈ 40cms) through +ve lenses + 2.00 – when vision clears replace with -ve lenses repeat count cycles per minute 1 cycle = plus, minus, plus again Normal facility varies with age - 2.00 Objective assessment of accommodation Static retinoscopy Conventional retinoscopy, fixation in the distance – Encourage zero accommodation (fogging) – Maximum ‘dis-accommodation’ – ‘Can’ detect accommodation fluctuations Dynamic retinoscopy Retinoscopy whilst actively accommodating at near – Near fixation, encourage active accommodation Assessment of accommodative lag/lead – Compare dynamic ret result with stimulus accommodation  Objective assessment 1: Dynamic M.E.M. Retinoscopy (Monocular Estimated Method) Near fixation target (usually 40cms) – Detailed stimulus to accommodation Ret at same viewing distance as target To neutralise – Over px’s Rx, place lens before ONE eye – Fellow eye continues to view target – Quickly ret to see if neutralised (1 second/lens) Ret beam will dazzle non-fixing eye – Remove lens – Increase / decrease lens power Repeat until neutralised WITH movement  add +ve (there is a LAG) AGAINST movement  add –ve (there is a LEAD) Assumes accommodation equal in each eye Assessment of Accommodative Lag/Lead Response vs. stimulus accommodation Stimulus accommodation relates to target distance; 40 cms = 2.50DS; 33cm = 3.00DS; 25cm = 4.00DS; 20 cm = 5.00DS Response accommodation: – Dynamic ret  MEM retinoscopy (lag or lead) Accuracy of accommodative response dynamic ret result – +0.50  +0.75 normal range for lag (pre- presbyopes) – > +0.75 suggests an accommodative lag issue (pre-presb) – investigate further A small (+0.25+0.50D) amount of accommodative lag is normal LAG increases as stimulus accommodation demand increases Interpreting LAG/LEAD (pre-presbyopes) High LAG >> +0.75 – Accommodative dysfunction: insufficiency/infacility – Uncorrected or under-corrected hyperope Low LAG or LEAD < +0.25 – Accommodative spasm – Uncorrected or under-corrected myope Results should be ≈ same in both eyes – If unequal  un-balanced distance Rx ? – Unilateral pathology ? IIIN Dynamic retinoscopy – sources of error As with static retinoscopy – Small pupils, poor media, scissors reflex Px cooperation with fixation – Compromised further as looking directly at light WD errors are exaggerated if not working at 40cms Adaptation to lenses if carried out too slowly – Accommodation will relax further with +ve ACCOMMODATIVE DISORDERS Accommodative disorders Accommodative insufficiency – Remote near point for age norm Accommodative lag – Underactive accommodation on near viewing for age norm Accommodative infacility (inertia) – Problems adjusting from near to distance Accommodative excess (spasm) – Partial or total – Over-action of accommodative system Accommodative paralysis – Inability to accommodate in a pre-presbyope Accommodative Insufficiency & Accommodative Lag Under accommodation to near target Prescribe maximum plus; minimum minus – For optimal distance vision – Try near point ‘accommodation’ exercises Consider an add for near vision to ‘boost’ the lag – near visual comfort – use objective methods to prescribe the ‘lag’ Dynamic MEM retinoscopy – fixation disparity (if present with decompensated SOP) neutralise eso‘slip’using binocular plus lenses Accommodative infacility Treat Symptomatic pxs with low facility rates: Refractive management Issue optimal correction; Maximum +ve, minimum –ve Consider add for near work Exercises (try simple first, little & often); 2-6x daily – Push up & jump accommodation – Flipper lenses – Review progress regularly (every 4-6 weeks) – If px unable or unwilling to do exercise  manipulate Rx Accommodative excess Habitual over-accommodation – Accommodative LEAD on near vision Refraction to give maximum plus – Patient tends to want more minus! – +1.00 blur test VA better than expected – Careful binocular subjective refraction – Keep re-checking non-fixating eye is blurred – Always leave plus lens in trial frame when adding the new lens Cycloplegic refraction Accommodative excess Prescribe (following cycloplegic refraction) – Maximum plus refraction – Constant Rx wear – Close review (3/12) Exercises – flipper lenses – Stereograms to dissociate connection between accommodation & convergence (to artificially relax accommodation while vergence remains the same) ? Refer if neurological investigation needed Accommodative spasm Full spasm as opposed to accommodative excess Miosed pupils (triad) Esotropia with diplopia (if recent onset) Pseudo myopia Excess accommodation gives apparent false myopia Could be -10.00D pre cyclo refraction Important to investigate with cycloplegia Referral: If previously un-investigated  should be referred for neurological investigation Accommodative paralysis Paralysis; no ability to accommodate No subjective or objective accommodation May have semi-dilated pupils Referral: If previously un-investigated should be referred for neurological investigation Refractive management (longer-term) – Distance vision Rx, prescribe Max. +ve, Minimum – ve – Full‘add’required for near vision +2.50DS or + 3.00DS Exercises NOT appropriate  Accommodation & Convergence Investigation & Management 5LMS0072 ACS Angela Gulati-Roy MSC., BSc. (Hons.), MCOptom, AFHEA University of Hertfordshire ACCOMMODATION & CONVERGENCE Relationship between Accommodation & Convergence can be expressed in many ways: +ve and –ve relative accommodation (-ve/+ve DS) – Changes in accommodation demand whilst vergence remains constant (fixed target distance ≈ 40cms) – Increase negative sphere to stimulate PRA (around -3D) – Increase positive sphere to stimulate NRA (around +2D) +ve and –ve relative convergence (Base Relationship between Accommodation & Convergence can be expressed in many ways: AC/A ratio (prism dioptres/dioptre) – Accommodative convergence to accommodation CA/C ratio (dioptre/prism dioptres) – Convergence accommodation to convergence Not used in practice AC/A ratio Amount of accommodative convergence per dioptre of accommodation (Δ / DS) Convergence resulting entirely from accommodation Convergence per DS of accommodation Response AC/A convergence change per 1.00DS of absolute change in accommodation  Difficult to measure Stimulus AC/A Convergence change per 1.00DS change in the stimulus to accommodation or accommodative demand Measurement used in practice (younger pxs with BVA) Not appropriate with older px’s Measurement of AC/A ratio a) Heterophoria method Comparison of heterophoria at distance & near (cover test) XOP (assigned minus) SOP (assigned plus) Pd (cms) + _____(Near Phoria – Distance Phoria)_______ Accomm demand (near target in Dioptres) e.g. Pd (60mm), Distance CT = ortho, Near CT = 6Δ XOP @ 33cms  Measurement of AC/A Ratio b) Gradient method Keep distance of target constant at 33cm Measure deviation (near CT) through binocular spherical +ve & -ve adds +3.00 to -3.00 in 1D steps Plot graph Gradient (from 2 points=AC/A) e.g. near CT (no add) = 2ΔSOP Practical significance of AC/A ratio at Near Values will vary with test method (gradient vs. heterophoria) Normal AC/A = 4:1 (s.d.+/-2) Helps determine relationship & guide treatment strategy High AC/A ratio (> 6:1) – Excessive change in angle of deviation with accommodative effort Near eso (convergence excess) Low AC/A ratio (< 2:1) – Insufficient change in angle between near & distance fixation Putting it together - summary Listen & probe px symptoms – HA, diplopia, aesthenopia, blurring, monocular comfort Consider & investigate differential diagnosis – Convergence/Accommodation problems? – Heterophoria? – Changing refractive error? Review environmental factors Prescribe optimal refractive correction & usage Consider use of exercises (& review px !!) – Probe previous success/failure, Motivation, compliance ? Manipulate Rx (& review px !!) Optometric treatment - summary Visual hygiene Vision therapy – Convergence insufficiency / fatigue – Accommodative insufficiency / infacility Manipulation of spheres – Symptomatic or significant accommodative lag – Heterophoria or heterotropia with HIGH AC/A ratio Prescribing prisms – Convergence inertia – Heterophoria or heterotropia with LOW AC/A ratio  Additional reading resources: Evans, B. J. W., & Pickwell, D. (2007). Pickwell's binocular vision anomalies (5th ed.). Elsevier Butterworth-Heinemann Rowe, F. J. (2012). Clinical orthoptics. ProQuest Ebook Central https://ebookcentral.proquest.com