Amblyopia and Visual System Quiz

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Questions and Answers

Which type of amblyopia is characterized by the functional expectation of improvement from treatment?

Stimulus deprivation amblyopia

Functional amblyopia (correct)

Organic amblyopia

Hysterical amblyopia

Which type of amblyopia refers to conditions where no detectable lesion is present?

Organic amblyopia (correct)

Toxic amblyopia

Strabismic amblyopia

Idopathic amblyopia

What is a key characteristic of amblyopia in relation to testing methods?

Amblyopia is more easily detected using single optotypes.

Amblyopia can only be diagnosed through clinical observation.

Amblyopia is less likely to be identified when using single optotypes. (correct)

Amblyopia effects are negligible regardless of testing method.

Which type of amblyopia might result from conditions that impair visual acuity (VA)?

All of the above (D) Signup and view all the answers

What does complete stimulus deprivation in amblyopia imply?

Little or no light enters the eye. (B) Signup and view all the answers

What should be done if the red reflex is lost during the examination?

Move back until the red reflex is found again and then repeat the observation. (B) Signup and view all the answers

What may the presence of leukocoria indicate during an examination?

Underlying pathology such as cataracts or retinoblastoma. (C) Signup and view all the answers

Where is the macula located in relation to the optic nerve head?

Lateral (temporal) to the optic nerve head. (D) Signup and view all the answers

What is the appearance of the fovea when the patient looks directly into the light?

It produces a bright spot of light. (C) Signup and view all the answers

What characteristic differentiates the fovea from the rest of the macula?

It appears darker due to the presence of additional pigment. (B) Signup and view all the answers

What is the primary role of rods in the visual system?

Detecting movement and function well in low light (A) Signup and view all the answers

During which period does amblyopia develop?

Critical period (D) Signup and view all the answers

Which part of the visual cortex responds to visual stimuli from both eyes?

80-85% of the visual cortex (D) Signup and view all the answers

What is true about the parvocellular (X) system in relation to visual acuity?

It needs a stable, well-focused image (D) Signup and view all the answers

What defines the sensitive period in visual development?

A period of improved function following deprivation (A) Signup and view all the answers

Which type of cells in the retina synapse with rods and cones?

Ganglion cells (D) Signup and view all the answers

What primarily happens to the visual system during the critical period?

A significant loss of visual function may occur due to deprivation (C) Signup and view all the answers

What is the role of the lateral geniculate body in the visual pathway?

It serves as a relay station for visual information headed to the visual cortex (B) Signup and view all the answers

What is the primary purpose of spontaneous alternation in visual fixation?

To assess eye momentary occlusions (B) Signup and view all the answers

What is the main function of the visuscope during examination?

To project a fixation target on the retina (B) Signup and view all the answers

What is the recommended position of the examiner when using a direct ophthalmoscope?

At eye level with the patient and slightly lateral (C) Signup and view all the answers

Why is it necessary to darken the room during the examination with a direct ophthalmoscope?

To allow for better visualization of the retina (D) Signup and view all the answers

When occluding one eye during a visual examination, which area should the normal eye use for fixation?

The fovea (A) Signup and view all the answers

What should the examiner do with their free hand when assessing the patient's right eye?

Position it to stabilize the patient's head (A) Signup and view all the answers

What is the significance of maintaining fixation on a target behind the examiner during ophthalmoscopy?

It enhances the clarity of retinal visualization (A) Signup and view all the answers

What is the suggested approach angle when using a direct ophthalmoscope to examine the eye?

45 degrees slightly temporal (A) Signup and view all the answers

What denotes functional strabismic amblyopia based on the described method?

VA unchanged or slight change in the abnormal eye with NDF (D) Signup and view all the answers

What should be recorded after using the neutral density filter (NDF) on the abnormal eye?

The strength of the filter applied (C) Signup and view all the answers

What is the function of the neutral density filter (NDF) during amblyopia testing?

To determine the density of suppression in one of the eyes (D) Signup and view all the answers

Which of the following descriptions applies to anisometropic amblyopia based on the testing method?

Acts similarly to organic amblyopia during assessments (C) Signup and view all the answers

What occurs when the patient reports diplopia while using the NDF?

The density of the filter is recorded at that point (D) Signup and view all the answers

What is the key aim in the management of amblyopia?

To achieve and maintain maximum visual acuity (C) Signup and view all the answers

How is the strength of the NDF filter determined during the assessment of BSV?

By recognizing the light's color change from red to white (D) Signup and view all the answers

In what scenario would VA in the abnormal eye drop significantly during the testing method?

When indicators reveal organic amblyopia (A) Signup and view all the answers

What is the primary cause of strabismic amblyopia?

Unilateral strabismus with early onset (D) Signup and view all the answers

Which type of amblyopia is characterized by significant differences in refraction between the two eyes?

Anisometropic amblyopia (B) Signup and view all the answers

In which type of amblyopia is high bilateral hypermetropia a significant factor?

Ametropic amblyopia (C) Signup and view all the answers

What characterizes meridional amblyopia?

High levels of uncorrected astigmatism (B) Signup and view all the answers

What is a common feature of idiopathic amblyopia?

No refractive error and normal binocular vision (C) Signup and view all the answers

Which condition is associated with the irreversible form of amblyopia?

Achromatopsia (C) Signup and view all the answers

Which type of amblyopia is most likely to improve with treatment, but may recur if treatment is stopped?

Idopathic amblyopia (D) Signup and view all the answers

What is the most likely refractive issue in ametropic amblyopia?

Bilateral high refractive error incorrectable by lens (D) Signup and view all the answers

What psychological component may be a factor in hysterical amblyopia?

Malingering or psychosomatic disorder (C) Signup and view all the answers

High degrees of astigmatism pose the greatest risk for which type of amblyopia?

Meridional amblyopia (D) Signup and view all the answers

What defines the visual presentations in anisometropic amblyopia?

One eye produces a clearer image at all distances (D) Signup and view all the answers

What makes toxic amblyopia different from other forms?

It arises due to exposure to detrimental chemicals (A) Signup and view all the answers

What is a primary characteristic of congenital cataracts in relation to visual development?

They can affect the quality of the image formed on the retina (D) Signup and view all the answers

Study Notes

Visual Development & Amblyopia

Amblyopia is reduction in visual acuity due to neurological deficits that impact visual output. It typically develops during critical periods of visual development.
It's usually unilateral and is the most common cause of vision loss and monocular blindness in children.
Amblyopia is categorized into various types, including:
- Stimulus deprivation
- Strabismic (eye misalignment)
- Anisometropic (unequal refractive errors)
- Ametropic (refractive errors like nearsightedness or farsightedness)
- Meridional (astigmatism)
- Idiopathic (unknown cause)
- Hysterical/psychogenic (psychological factors)
- Organic
- Toxic
The prevalence of amblyopia is reported between 1–5% worldwide. The incidence may be higher in medically underserved or low socioeconomic populations. These figures may vary between studies.
The Greek word "amblyopia" means "dull sight" or "blunt sight."
Visual function involves light sense, form sense, colour sense and motion sense.
Visual acuity development has critical and sensitive periods
Normal visual experience is needed for the rods and cones in the retina to synapse with ganglion cells
Parvocellular (X) system needs a stable, well-focused image.
80-85% of visual cortex cells respond to vision from either eye.
15-17% of visual cortex cells respond to vision from an eye with strabismus.

Development of Visual Acuity

Visual acuity develops from birth to 3-5 years old.
A critical period for visual development exists from early childhood (few months to 7-8 years old).
A sensitive period for visual development exists from deprivation until teenage years (some cases extend to adulthood).

Critical Period

Deprivation during critical period results in loss of visual function.
Neural plasticity makes vulnerable visual systems to abnormal experiences such as strabismus and other visual deprivation
Severity of changes during these periods depends upon age when the defect develops.
Amblyopia typically starts when an infant becomes binocular (2-4 months old).

Sensitive Period

Amblyopia is treatable when treated during the sensitive period.
Amblyopia is most successfully treated in children.
The younger the amblyopic patient, the more rapid the response to treatment.
Treatment is rarely successful after age 8.
Exceptions include anisometropic amblyopia or those with no previous treatment.

Interfering factors in Normal Visual Development

Cataract
Unilateral ptosis (drooping eyelid)
Injuries affecting the eye or the back of the head (e.g., occipital cortex)
Tumours such as optic nerve tumours
Anisometropia (unequal refractive errors causing different image sizes)
Nystagmus (involuntary eye movements)

Mechanism of Amblyopia

Stimulus deprivation results in a loss of form vision.
Abnormal binocular interaction or competition results in incomplete images formed on the retina.

Amblyopia - Reduced Vision

Loss of Snellen and grating acuity
Loss of sensitivity to contrast
Distortions in stimulus shape
Uncertainty about stimulus position
Motion deficits
Crowding effect and separation difficulty

Crowding Phenomenon

Line of letters of symbols identified less easily than single optotypes.
A key characteristic of amblyopia, more prominent in amblyopic patients.

Types of Amblyopia

Stimulus deprivation
- Affects one or both eyes
- Complete - little or no light entering the eye.
- Partial - some light hits the retina, but poor quality image.
- Conditions such as ptosis, corneal scar, or congenital cataracts may result in stimulus deprivation.
Strabismic
- Constant or near-constant unilateral strabismus
- Onset usually in childhood.
Anisometropic
- Significant difference in refraction between the two eyes.
- One eye receives a clearer image for all distances, while the other eye's image might be blurry.
Ametropic
- High bilateral hypermetropia (farsightedness) greater than 6.00DS frequently causes reduced visual acuity and cannot be compensated by the eye's accommodation
- Bilateral occurs in severe myopia (shortsightedness).
Meridional
- Moderate or high degree of uncorrected astigmatism.
Idiopathic
- No refractive error.
- Normal BSV.
- Foveal suppression scotoma (4^ test).
Hysterical and psychogenic
- Psychogenic or psychosomatic disorders.
- Malingerring.
Organic
- No lesion detectable but can be irreversible.
- Conditions like achromatopsia, albinism, nystagmus, and MD may present.
Toxic
- Visual acuity loss occurs due to absorption or exposure to toxins such as cyanide, ibuprofen (some cases are reversible).
- Specific examples include tobacco, alcoholics, extreme diets.

Investigation & Diagnosis of Amblyopia

Case history
Fundus and media examination
Refraction test
Visual acuity test
Crowded visual acuity
Grating acuity (careful interpretation)
Pinhole test
Contrast sensitivity test
Strabismic & anisometropic amblyopes - may have marked losses of CS especially at higher spatial frequencies
Cover test
Prism test (10°prism)
Uniocular fixation
Neutral density filter test

Fixation Patterns and Amblyopia

Strabismic amblyopia typically presents with constant unilateral deviation.
Accuracy of fixation
Ability to hold fixation (blink/versions)
Objections to covering one eye.
Cross fixation.

10° Fixation Test

Allows observation of fixation preference in straight or small angle strabismus.
10° vertical prism is held over one eye (BD).
Induces vertical deviation.
Abnormal patterns include spontaneous alternation, delayed re-fixation, limited fixation durations, re-fixation delays not induced by blinks or pursuit movement.

Direct Ophthalmoscope

Viewing the inside portion of the eye
Filter switch, aperture dial, diopter dial, and rheostat are used to adjust viewing conditions.

Uniocular Fixation

Used as a diagnostic tool to test fixation with occlusion of the fellow eye.
Normal fixation is directed toward the fovea.

Direct Ophthalmoscope Procedure

Patient positioning and ophthalmoscope adjustments.
Darkening of the room.
Target fixation and finding the red reflex.
Identifying the optic nerve and retinal blood vessels.
Assessing fixation using graticule target and occluding fellow eye.
Identifying macula and fovea.

Retina

Macula, Fovea, Optic Cup and Optic Disc are central parts of the eye.
Bright spot of light is seen in the fovea when the patient looks directly into the light

Central and Eccentric Fixation

Central fixation - fovea used to receive the image (lying in the principle visual direction)
Eccentric fixation - fixation on a point on the retina other than the fovea.

Eccentric and Wandering Fixation

Fixation further away from fovea, worse vision.
Area of retina used for fixation, visual acuity indication.
Wandering fixation is a uniocular condition where the fovea has lost its superiority and fixation wanders around.

Neutral Density Filter (NDF)

Reduces all wavelengths of light equally.
Amblyopic eyes perform well in low lighting.
Differentiation between strabismic amblyopia and reduced VA due to organic factors.

Neutral Density Filter (NDF) Test

Patient wears refractive correction.
Record VA distance uniocularly.
Occlude the abnormal eye and place NDF in front of the normal eye.
Increase NDF density until the point where VA drops by 2 lines.
Occlude the normal eye and hold the same filter over the abnormal eye.
Record VA.

SBISA Bar

17 filters ranging from palest pink to dark red.
Used to assess density of suppression.
Used to judge the risk of intractable diplopia during occlusion treatment.
Method: Patient fixes on a spotlight at near. Lightest filter is placed over fixing eye. Density of filter is increased until the patient reports diplopia (one red, one white light), light changes from red to white.

Management of Amblyopia

Aim is to achieve and maintain maximum visual acuity.
Remove any cause of stimulus deprivation and correct the refractive erros.
Choose appropriate form of treatment (eg: occlusion, atropine).
Discontinue treatment when maximum acuity is achieved or watch for stabilization.
Go back to Step 2 (if VA isn't maintained).
Refractive Adaptation (if glasses required).
Occlusion
Atropine
Optical penalization.

Types of Treatment

Total light occlusion
Partial form occlusion
Cycloplegic occlusion
Optical penalization
Total form occlusion

Management Considerations

Age
General health and vision
Fixation type
School status
Duration and type of strabismus
Nystagmus
Density of suppression

Advice to Parents

Involve patient in choices.
Encourage compliance (especially in lower-income families, with education as a motivator).
Previous admittance to children's ward due to poor compliance.

Contraindications

Patch/atropine allergy.
Eye infection.
Pathological causes of reduced VA.
Low density of suppression (high risk of intractable diplopia)
Previous treatment failure.
Child with multiple diagnoses/syndromes
Terminal diagnosis
Emotional upset by treatment
Social problems.

When to Stop Treatment

When visual acuity (VA) is equal to the fellow eye on a linear test.
When free alternation occurs
When there is no further improvement, or the density of suppression reduces with a high risk of intractable diplopia.

Prognosis

Successful outcomes in 63-83% of patients
Success is dependent on Treatment age, Patient severity of amblyopia, Treatment compliance , Type of amblyopia, Number of amblyogenic factors
(E.g., strabismic and anisometropic factors).
The treatment is more cost-effective than cataract and macular hole treatments.

Extra Reading

Stewart, CE, Moseley MJ, Fielder AR, et al. Refractive adaptation in amblyopia: quantification of effect and implications for practice. British Journal of Ophthalmology, 2004;88:1552–1556.
Rowe, Fiona J. Clinical Orthoptics. 3rd ed. Hoboken: John Wiley & Sons, 2012.
Ansons, Alec M, and Helen Davis. Diagnosis and Management of Ocular Motility Disorders. Hoboken: Wiley, 2013.
Levi DM. Rethinking amblyopia 2020. Vision Res. 2020 Nov;176:118-129. doi: 10.1016/j.visres.2020.07.014. Epub 2020 Aug 28. PMID: 32866759; PMCID: PMC7487000.

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Description

Test your understanding of amblyopia, its types, and the visual system. This quiz covers key characteristics, treatment expectations, and various conditions related to visual acuity. Dive into the intricacies of the visual system and enhance your knowledge on how different factors can affect vision.