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Anomalies of accomodation ‫‬

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Anomalies of accomodation ‫‬

  3. 3. DEFINITION ACCOMMODATION is : -The facility enabling the change in dioptric power of the crystalline lens thereby altering the .focus of the eye
  4. 4. ASSESSMENT OF ACCOMODATION  Dynamic retinoscopy.  Subjective measurement of accommodation amplitudes with e.g., RAF rule.  Facility of accommodation with "lens flippers“.
  5. 5. ACCOMODATION FATIGUE Apart from overuse, factors that influence onset of fatigue include :- • refractive status. • Relationship with convergence. -Symptoms of accommodative fatigue:- • Asthenopia.(Ocular Symptoms).
  6. 6. Treatment of fatigue  Correct significant ametropia.  Correct significant OMB anomaly.  High astigmatism ? - check near cyl. Axes.  Discuss "Visual Hygiene“.  Consider "orthoscopic" spectacles.
  7. 7. FAILURE OF ACCOMMODATION • Presbyopia. • Pre-senile cataract. • Insufficiency of accommodation. • Sustained of accommodation. • paralysis of accommodation. • Inertia of accommodation.
  8. 8. FAILURE OF ACCOMMODATION  Presbyopia is a condition of physiological insufficiency of accommodation leading to a progressive fall in near vision.
  9. 9. PRESBYOPIA  Pathophysiology: - In emmetropic eye far point is infinity and near point varies with ages. Failing near vision due to age-related decrease in amplitude is called presbyopia.
  10. 10. PRESBYOPIA  Causes Decrease in accommodative power of lens with increasing age, leads to presbyopia, occurs due to:1)Age-related changes in lens: Decrease in elasticity of lens capsule, increase in size and hardness (sclerosis) of lens substance which is not easily molded(‫.)تتشكل‬ 2)Age related decline in ciliary muscle power.
  11. 11. PRESBYOPIA  Symptoms of presbyopia:-  "I have to hold my book further away“.  "my arms are not long enough“.  "newspaper print is not what it used to be’’.  Patients complain of reading difficulty in poor light, tired eyes after reading and BLURRED VISION for reading.  Treatment:-  Prescribe correction so that near point of focus is brought within normal working distance.
  12. 12. PRESPYOPIA  Determination of reading addition:-  Objective - dynamic retinoscopy  Subjective :- (a) complete distance refraction. (b) measure amplitudes of accommodation. (c) use amplitudes as a STARTING point to calculate an approximate reading addition. -Rule of thumb - leave 1/3rd accommodation in reserve.  Check clarity and range. Double check with +&- additions.
  13. 13. Pre-senile cataract  Cataract is likely to reduce accommodation  May be unilateral.  Unequal reading adds .  May have reduced VA.
  14. 14. Insufficiency of accommodation Definition : -Condition in which accommodative power is constantly less than lower limit of normal range according to patient’s age.
  15. 15. Insufficiency of accommodation Etiology :  1)Premature sclerosis of lens.  2)Weakness of ciliary muscle due to systemic causes: Debilitating illness(‫شديد‬ ‫أو‬ (‫ك‬ِ‫ه‬‫من‬ ‫مرض‬ , anemia, toxemia, malnutrition, diabetes mellitus, pregnancy, stress etc.  3)Weakness of ciliary muscle due to local causes: POAG(primary open angle glaucoma), mild cyclitis (‫الهدبية‬ ‫العضلة‬ ‫التهاب‬) as during onset of sympathetic ophthalmia.
  16. 16. Insufficiency of accommodation Symptoms of insufficiency :- • Asthenopia. • Blurred vision for near work . • Over- or under-convergence.
  17. 17. TREATMENT OF INSUFFICIENCY  1) Identification & treatment of any systemic cause.  2) Any refractive error should be corrected & if vision for near work is seriously blurred then additional near correction has to be prescribed same as presbyopia.  3) If associated with convergence excess then full spherical correction.  4) Convergence insufficiency is there, then base in prisms can be added.  5) Prismatic correction added should bring near point of convergence to same distance as near point of accommodation.
  18. 18. TREATMENT OF INSUFFICIENCY  6) Weakest convex lenses should be prescribed, so as to exercise and stimulate accommodation.  7) After recovery additional correction should be made weaker and weaker from time to time.  8) Accommodative exercises.  – While do exercises patient should wear correction for distance.  – Should be done simultaneously in both eyes, even if associated with convergence insufficiency.  – But with convergence excess then the exercise should done with one eye alternately.  – Accommodation test card exercise.  Accommodative exercises useless in generalized debility and sclerosis of lens.
  19. 19. SUSTAINED ACCOMMODATION Sustained accommodation:-  Amplitudes are normal but rapidly diminish with use.  Etiology of Ill sustained accommodation:  Commonest cause – debilitating illness. Investigation & Treatment:  In the same way as insufficiency.
  20. 20. PARALYSIS OF ACCOMMODATION  May be partial or total, unilateral or bilateral.  Signs and symptoms  Blurred vision  Micropsia -More accommodative effort required to see near object which is then perceived to be nearer than it actually is and therefore smaller.  Markedly reduced amplitude of accommodation.  If lesion is localized to the lens or ciliary body then these will be the only signs and symptoms.  If III rd. Oculomotor nerve is affected then there will be other signs. Oculomotor nerve innervates muscles that enable most movements of the eye and that raise the eyelid.
  21. 21. PARALYSIS OF ACCOMMODATION Etiology  Congenital defects e.g., no ciliary muscle.  Cycloplegic drugs (atropine).  topical eye drops .  Systemic drugs.  Degenerative conditions e.g. Parkinson’s-‫الرعاش‬ ‫.-الشلل‬  Exogenous poisons e.g., snake bites, bee stings.  III N lesion (tumors, aneurysm- -‫تمدد‬‫الدموية‬ ‫األوعية‬ , hemorrhage).  Ocular disease (anterior uveitis- -‫التهاب‬‫األمامي‬ ‫القزحية‬ , glaucoma).  Trauma to head or eye (temporary or permanent paralysis- ‫شلل‬ ‫دائم‬ ‫أو‬ ‫مؤقت‬- ).
  22. 22. PARALYSIS OF ACCOMMODATION  TREATMENT :-  Self recovery (‫ذاتي‬ ‫)شفاء‬ occurs in drug induced paralysis .  Dark glasses are effective in reducing the glare.  Convex lenses for near vision may be prescribed.
  23. 23. SPASM OF ACCOMMODATION  Tone of ciliary muscle is increased and a constant accommodative effort is expended by the parasympathetic nervous system. Pseudomyopia produced -over stimulation of parasympathetic nervous system- Symptoms:-  Blurred vision depending on patient’s refractive status.  Macropsia.  Asthenopia during close work.  Pain (brows/headache).  Poor concentration.  Miosis.  Convergence anomalies (excess or insufficiency).
  24. 24. SPASM OF ACCOMMODATION Investigation:- -Cycloplegic refraction used to determine true refraction.(atropine drops for 2-4 weeks or more) Aetiology:- -Spasm can be further categorized into:-  (a) Functional spasm.  (b) Organic spasm.
  25. 25. SPASM OF ACCOMMODATION Functional spasm:-  A response to over fatigue and "eye strain". o Precipitated by 3 factors:  Bad visual hygiene e.g., poor lighting, glare. unaccustomed work.  Optical or ocular motor difficulties e.g., anisometropia, early presbyopia, convergence anomalies. Treatment of functional spasm:-  Eliminate exciting cause.  Consider general health, mental state.  Correct refractive error and/or ocular motor anomaly.
  26. 26. SPASM OF ACCOMMODATION Organic spasm:- -Irritation ‫ُّج‬‫ي‬‫ته‬ of parasympathetic system. Etiology:-  Ciliary spasm: - drug induced e.g., physostigmine, pilocarpine, morphine, digitalis.  - lesions of brainstem.  Inflammation e.g., anterior uveitis ‫األمامي‬ ‫القزحية‬ ‫التهاب‬  Trigeminal neuralgia ‫الثالث‬ ‫العصب‬ ‫التهاب‬  Others ,e.g., diphtheria, tooth extraction  Treatment of organic spasm:-  Manage the cause.
  27. 27. Summary Anomalies of accommodation are very common. Management of these anomalies is an integral part of optometric practice.