accommodation Flashcards
(27 cards)
What is accommodation in the context of optometry?
Accommodation is the eye’s ability to change its focus from distant to near objects by increasing its optical power.
What is amplitude of accommodation?
Amplitude of accommodation is the maximum increase in optical power the eye can achieve when adjusting its focus from far to near, measured in diopters (D).
What is the purpose of measuring amplitude of accommodation?
Measuring amplitude of accommodation helps assess the focusing power of the eye, particularly in pre-presbyopic patients.
How is amplitude of accommodation typically measured?
Amplitude of accommodation is measured using the push-up/pull-down method (RAF rule), which involves moving a reading card towards and away from the eye while the patient reports when the text becomes blurred or clear.
What are the steps for measuring amplitude of accommodation using the push-up/pull-down method?
The patient wears distance correction (if needed).
The RAF rule is placed against the patient’s face.
The reading card is moved towards the patient until blur is reported (push-up amplitude).
The card is moved away from the patient until clarity returns (pull-down amplitude).
Record the average of both values as the amplitude of accommodation.
What is the difference between monocular and binocular amplitude of accommodation?
Binocular amplitude of accommodation is typically 1-2D higher than monocular amplitude due to the convergence response inducing additional accommodation.
What would you expect to see in a normal amplitude of accommodation for a 20-year-old?
A 20-year-old should typically have an amplitude of accommodation around 10D, though this value will vary depending on individual factors.
What factors can affect the amplitude of accommodation measurement?
Depth of focus: Can artificially raise the amplitude.
Moving target: Can overestimate the push-up amplitude and underestimate the pull-down amplitude.
Subjective reporting of blur and clarity: The accuracy relies on the patient’s subjective response.
What is the rate of decline in amplitude of accommodation with age?
: The decline is approximately 0.3 to 0.4D per year, and it accelerates after the age of 40, leading to presbyopia.
What is accommodative facility?
Accommodative facility is a measure of the speed at which the eye can change focus between near and far objects.
How is accommodative facility assessed?
Accommodative facility is assessed using ±2.00 DS flippers, where the patient focuses on a target while alternating between plus and minus lenses. The number of successful cycles per minute is recorded.
What is the significance of accommodative facility in diagnosis?
Accommodative facility tests the speed of accommodation. If the system is slow to respond, the patient may experience blurred vision, even if the amplitude is normal.
What is considered a normal accommodative facility result for adults?
For adults (up to 30 years of age), a result of >11 cycles per minute (cpm) for monocular testing and >8 cpm for binocular testing is considered normal.
What is the clinical significance of a failed accommodative facility test?
A result of <11 cpm (mono) or <8 cpm (binocular) indicates accommodative infacility, which can cause blurred vision when shifting focus between near and distant objects.
What is dynamic retinoscopy used to assess in accommodation?
Dynamic retinoscopy is used to measure accommodative lag or lead, which is the difference between the accommodative response and the demand for focus at a near distance.
What is the definition of accommodative lag?
Accommodative lag occurs when the accommodative response (the eye’s focusing effort) is less than the stimulus demand (i.e., the amount needed to focus at a near distance).
What is considered a normal range for accommodative lag?
Most pre-presbyopic individuals have an accommodative lag ranging from 0 to +0.75D.
What is considered pathological accommodative lag?
A lag of ≥ +1.00D indicates accommodative insufficiency, which may require further investigation or intervention.
What is the difference between accommodative lag and lead?
Accommodative lag: The eye’s accommodative response is less than the stimulus demand (the eye doesn’t focus enough).
Accommodative lead: The eye over-accommodates, focusing more than needed for the near stimulus.
How is dynamic retinoscopy performed using the MEM method?
The patient wears their distance correction (if needed).
A near target is held at 40 cm.
Retinoscopy is performed while the examiner observes the movement of light on the retina to assess accommodative response.
Record the lens power that neutralizes the reflex; +ve lenses indicate lag and -ve lenses indicate lead.
What is the Nott method of dynamic retinoscopy?
The Nott method involves adjusting the working distance of the retinoscope to achieve neutrality, where the amount of movement (with or against) indicates accommodative lag or lead.
How is a lag of accommodation recorded in dynamic retinoscopy?
A lag of accommodation is recorded as a +ve value (e.g., +0.50D), indicating that the accommodative response was less than the stimulus.
What would you record if a lag of accommodation was found to be +0.50D?
: You would record “MEM RE +0.50DS” for the right eye, indicating a +0.50D lag.
How can pseudomyopia or accommodative spasm be identified using dynamic retinoscopy?
Pseudomyopia or accommodative spasm can be identified by a negative accommodative lag (e.g., a lag < 0), which would indicate excessive accommodation.
