9. Accommodation Flashcards
What is accommodation?
The function whereby the refractive power of the optical system can change, such that both near and distance objects can be brought to a clear focus on the retina.
Amount of accommodation required is relative to?
Related fixation distance
2 types of accommodation?
- Defective
- Excessive
5 classes of defective accommodation?
- Presbyopia
- Accommodative Insufficiency
- Accommodative fatigue
- Accommodative inertia
- Accommodative paralysis
What is presbyopia?
- NORMAL age change of the crystalline lens.
- Patients will attempt to increase their reading distance.
Causes of premature presbyopia?
- Premature presbyopia may be result of poor general health or glaucoma.
- Treat symptoms with convex lenses (readers).
- Identify cause in premature presbyopia and treat cause if possible.
What is accommodative insufficiency?
- Inability to obtain necessary amount of accommodation.
- Amplitude or near point of accommodation is below normal expected for age.
Symptoms of accommodative insufficiency?
Blurred near VA, Asthenopia
Causes of accommodative insufficiency?
Uncorrected refractive error, poor general health, viral infection, sudden increase in close work, drugs (prescription; including some hypertensive drugs, high oestrogen contractive pills, valium), Trauma.
Treatment of accommodative insufficiency?
Manage general health issues, correct refractive error, orthoptic exercises (if related to CI), miotics, convex lenses.
(Reducing the pupil size will increase the depth of focus and so less accommodative effort is needed).
Accommodative Fatigue
1. Meaning
2. Symptoms
3. Cause
4. Management
Symptoms:
Near VA blurs after periods of close work.
Aetiology:
Poor GH, Stress/Tiredness, Excessive close work, Uncorrected ref error, Hysterical rection.
Management:
This is usually a temporary problem.
Rest, treat GH, correct ref error, orthoptic exercises (Fusion/ conv poor), temporary convex lenses.
Accommodative inertia meaning, symptoms, cause, management
- Bilateral failure/ delay in adaptation of accommodation as fixation distance changes.
Symptoms:
Intermitted blurred VA at near and/ or distance.
Aetiology:
Poor general health, fatigue, Adies pupil.
Management:
Correct refractive error, hope that general health improves, improves fusion range and convergence- emphasis on changing fix’n distance.
Accommodative paralysis meaning, symptoms, cause, management
Total inability to accommodate
Symptoms:
Blurred VA at near (unless myopic), photophobia (pupils fixed and dilated), photopsia, micropsia, diplopia for near if convergence paralysis.
Cause:
Drugs (Cycloplegic), trauma (Eye or head), 3rd nerve palsy (Congenital/ acquired), space occupying lesion, general disease.
Management:
Treat cause, correct refractive error, reading add or prism for near (if exotropia present), miotics.
(If exophoria present) if there is no accommodation present there will be no accommodative convergence. This could result in exotropia.
Characteristic of Miller-Fisher syndrome with complete ophthalmoplegia and paralysis of accommodation
It is characterized by abnormal muscle coordination, paralysis of the eye muscle, and absence of the tendon reflexes.
Excessive accommodation- accommodative spasm: meaning, signs & symptoms, cause, management
Accommodative spasm: This is the bilateral inability of the ciliary muscle to relax, accommodation is continually exerted.
Signs and symptoms: Blurred distance VA (pseudo myopia), divergence weakness, esophoria/ distance esotropia, miotic pupils, headache, pain, difficulty judging distance, macropsia.
Cause: Uncorrected hyperopia, controlling distance XT using excessive accommodation, overworking/ fatigue, functional/ emotional (no clinical reason), cyclic oculomotor spasm, head trauma involving brain stem.
Management: 1% atropine, BT if conv spasm, treat GH cause, STOP close work, temporary convex lenses, refer to psychiatric services.
