Optometry Accommodation Quiz

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Accommodation and Eye Examination

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• Lecture title: Accommodation and Eye Examination, course OPT505, lecturer Ellie Livings

Intended Learning Outcomes

• Understand the role, purpose, and mechanism of accommodation
• Understand the relevance of accommodation in ametropia and its correction
• Know how to measure accommodation near point (AoA)
• Understand far point, range of accommodation, and accommodative demand
• Know how to calculate accommodation required and range of accommodation

Relevant GOC LO

• Undertakes safe and appropriate ocular examinations
• Informs clinical decision-making within individual scope of practice
• Refractive management
• Pediatrics
• Patients with learning disabilities & complex needs
• Occupational optometry
• Interprets the results of history-taking and examination of the refractive and ocular motor status
• Manages and dispenses appropriate spectacles
• Adapts practice environment and activity for individual needs
• Patient health informs clinical decision-making and care management plans

Recap Optics

• Simple Myopia: Dioptric power of the eye is too strong, axial length is too long, point focus is in front of the retina, blur circle
• Simple Hypermetropia: Dioptric power of the eye is too weak, axial length is too short, point focus is theoretically behind the eye, blur circle

Scale Model of Eye

• Cornea thickness, lens thickness, cornea to lens distance
• Radius
• Power (mm2)
• Various refractive indices (n) of eye components

Dioptric Power of Eye and Correcting Lenses

• Dioptric power measurements are shown on a number line
• Corrective lens needed for too-weak or too-strong dioptric power

Relaxed/Accommodated Lens

• Diagrams illustrating the relaxed and accommodated states of the lens
• Ciliary muscles, zonular fibers, and suspensory ligaments play roles in accommodation
• Far point and near point

Human Eye Accommodation Range

• Normal accommodation range (25 cm)
• Nearsighted accommodation range (18 cm)
• Farsighted accommodation (31 cm)
• Relaxed eye muscles

Accommodation over time

• Accommodation amplitude (AOA) declines with age.
• AOA is reduced at age 60, but depth of field/focus keeps subjective AOA from being the same as objective AOA.
• Distance Rx is corrected to measure the subjective AOA.

Depth of (object ) Field & Depth of (image) Focus

• Range of object distances where the circle of confusion is small enough to perceive a sharp image
• Range of image distances where the image of an improperly focused object is acceptably sharp
• The circle of confusion is the area of the retina stimulated by light from a point on an object, so the larger the circle, the more blurry the image

The Size of the Blur Circle

• Blur circle depends on focussing error, pupil size, axial length

Accommodation

• Amplitude of Accommodation (AOA) is the maximum amount of accommodation an individual can exert and is measured in diopters.
• AOA can be measured subjectively or objectively using RAF rule.

How do we measure Amplitude (AoA)?

• Push-up/pull-down method (using a RAF rule/Mallet unit)
• Minus lens technique
• Accommodative facility
• Lens rock
• Accommodative lag
• Dynamic retinoscopy

AOA: real life

• People can't hold maximum accommodation for very long periods, and overexertion can cause asthenopia (eye fatigue).
• When AOA is insufficient, near tasks become difficult.
• Rule of thumb: a patient can exert about two-thirds of their accommodative amplitude.
• Graph showing changes in accommodation over time based on age

AOA – Clinical Significance

• Symptoms relating to reduced AOA, such as headache and eye strain, are often associated with uncorrected hyperopia.
• Possible causes include latent hyperopia, medication, pathology (uveitis, etc), traumas, down's syndrome and cerebral palsy, stress, drug/alcohol misuse, and cataract

Accommodative Lag

• Measure with near retinoscopy (dynamic retinoscopy)
• Normal lag is 0.50–0.75D.
• Larger lag can be linked to myopic progression; hyperopic defocus during near work can increase myopia.
• Lag is associated with near esophoria in young myopes

Accommodative Anomalies

• Combined accommodative and convergence insufficiency is common
• Accommodative insufficiency/infacility/fatigue can lead to the use of exercises, plus lenses, or multi-focal lenses.
• (AC/A ratio) how convergence is changed from prism dioptres related to 1 diopter of accommodation. The high number means that the eyes may converge too much when accommodating

Case Scenarios (I - VI)

• Questions regarding accommodation levels required for various scenarios (emmetropic patient, myopic patient)

Further Reading

• List of suggested resources for further study

Test your knowledge on the level of accommodation required for various refractive errors in ophthalmology. This quiz covers emmetropia, myopia, and hyperopia, focusing on calculating accommodation levels for different distances. Perfect for students studying optometry or eye care principles.