2. Amblyopia
Amblyopia is a condition of diminished visual form
sense which is not as a result of any clinically
demonstrable anomaly of the visual pathway and
which is not relieved by the elimination of any defect
that constitutes a dioptric obstacle to the formation
of the foveal image.
It occurs in up to 2 to 4% of the population
3. Aetiology
Amblyopia is caused by inadequate stimulation of the
visual system during the critical period of visual
development in early childhood
Light deprivation
Form deprivation
Abnormal binocular interaction
The prognosis for achieving good visual acuity decreases when more than
one of these factors is present together in one case.
5. Amblyopia Classification
Stimulus deprivation amblyopia:
Amblyopia, which is the result of lack of adequate
visual stimulus in early life. This may be unilateral or
bilateral and may be:
– complete, where no light enters the eye
– partial, where there is some passage of light into the
eye.
6. Amblyopia Classification
Strabismic amblyopia:
Amblyopia, which is the result of manifest strabismus
and is caused by constant unilateral strabismus in
childhood.
Anisometropic amblyopia:
Amblyopia, which is the result of a significant
difference
in the refractive errors of the two eyes where one eye
has the visual
advantage at all distances.
7. Amblyopia Classification
Meridional amblyopia:
Amblyopia, which is the result of uncorrected astigmatism
where one or both eyes are predominantly astigmatic.
Ametropic amblyopia:
Bilateral amblyopia, which is the result of a high degree
of uncorrected bilateral refractive error.
Occlusion amblyopia:
Amblyopia, which may occur after use of total occlusion
or atropine, particularly before the age of 2 years. Visual
acuity is usually restored with careful treatment and
monitoring
9. Management
Correct the refractive error as visual acuity often
responds when the correct prescription is worn
(refractive adaptation).
A period of 6 to18 weeks is recommended for
refractive adaptation before implementation of
occlusion
10. Methods of treatment to restore visual
acuity in amblyopia
Occlusion
Cycloplegic
Drugs
Optical penalization
CAM visual stimulator
Pleoptic
11. Management
Occlusion is the most commonly used method
of treating amblyopia.
The normal eye is occluded and occlusion may
be in the form of total light or form, or partial.
12. Management
Total light and form: Skin patches etc
Total form: Frosted glasses etc
Partial: Semi transparent material
which reduced VA up to some
extent
13. Duration of occlusion
• The starting level of occlusion is between 2 and 6 hours
daily coupled with near or distance activities.
• Two hours of occlusion daily has been shown to be as
effective
as 6 hours daily for amblyopia of 0.3–0.6 logMAR in
children under the age of7 years (PEDIG 2003, PEDIG 2006).
• For those with amblyopia of 0.7–1.3, 6 hours of occlusion
is as effective as full-time (Holmes et al. 2003, Stewart et al.
2007b).
14. Duration of occlusion
An ideal goal is less than 400 hours of occlusion or 6
months of occlusion treatment.
Late occlusion (after the age of 8 years) has been shown
to be effective in selected cases (Mohan et al. 2004, PEDIG 2005).
15. Consequences of amblyopia
The risk of permanent visual loss in the better eye is
reported as 32.9 per 100,000population (Rahi et al. 2002).
Presence of amblyopia interferes with schooling, work,
lifestyle, sports and career choice (Adams & Karas 1999,
Packwood et al.
16. Aims of occlusion
1. Equalize visual acuity
2. Achieve optimum visual acuity
3. Central fixation
Continue occlusion until:
1. equal visual acuity is achieved;
2. the optimum visual acuity is achieved;
3. there is no further increase in visual acuity with full-time
total occlusion.
17. Recurrence
Long-term follow-up of amblyopic patients shows an
average reduction in visual acuity for up to 75% of
patients of 1.2–2.6 Snellen lines at least 5 years post
cessation of treatment (Gregersen & Rindziunski 1965, Sparrow &
Flynn 1979,PEDIG 2004, Bhola et al. 2006, King et al. 2007, De Weger et al.
2010)ss
Regression of visual acuity is more likely to occur with
abrupt cessation of occlusion rather than tapered (Holmes
et al. 2004).
18. Compliance issues
• Success of occlusion treatment relates in part to the
compliance of the patient and parents/guardian in
undertaking the occlusion regime.
• It is generally agreed that thorough discussion of the
occlusion regime backed up by written information has a
positive impact on occlusion success (Newsham 2002).
• Compliance has been reported in 78% in those with
written information and 57% in those without
information (Loudon et al. 2006).
•
19. Unresponsive amblyopia
• Where visual acuity does not improve with occlusion
treatment, an increase in occlusion or switch to
another treatment option should be considered.
Where continued lack of improvement occurs,
detailed assessment of the visual pathway should be
made to exclude pathology.
20. Cycloplegic drugs
Where occlusion is not tolerated, cycloplegic drugs may
be used to blur the vision in the better eye, thereby giving
the amblyopic eye more stimulus.
Typically, atropine 1% has been used once daily but
atropine instilled only at weekends is equally effective
(PEDIG 2004, Repka et al. 2009).
Atropine has been shown to be equally as effective as
occlusion for visual acuity of 0.3–0.7 logMAR (PEDIG 2002)
with maintenance of visual acuity to long-term follow-up
(PEDIG 2008).
21. Cycloplegic drugs
Advantages
1. The patient cannot cheat as can occur with occlusion where the
child peeps over the patch or where there is poor or non-
compliance.
2. The child and parent often prefer it to occlusion.
3. There is little or no cosmetic problem.
Disadvantages
1. Side effects of atropine.
2. Visual acuity may not be reduced enough where there is dense
amblyopia.
3. Atropine takes a period of 10–14 days to wear off.
4. Frequent visits are required to monitor fixation as an indicator of
visual acuity.
22. Penalisation
Penalisation is the treatment of amblyopia by optical
reduction of form vision of the nonamblyopic eye at one
or all fixation distances.
The effect may be achieved by the alteration of the
spectacle correction or use of a cycloplegic drug
(Gregersen et al. 1965, Repka & Ray 1993).
23. Penalisation
Total penalisation is the use of the amblyopic eye at
all distances by using strong convex lenses before the
better eye .
Near penalisation is the use of the amblyopic eye for
near fixation by using a cycloplegic drug in the better
eye and adding a convex lens up to 3.0 DS before the
amblyopic eye.
Distance penalisation is the use of the amblyopic eye
for distance fixation by using additional convex lenses
before the better eye.
24. Drugs
Dopamine is a neurotransmitter which is involved
in several visual functions.
Levodopa given orally produces an increase in contrast
sensitivity in an amblyopic eye but does not induce
changes in the nonamblyopic eye (Gottlob & Stangler-
Zuschrott 1990).
These findings suggest an involvement of dopaminergic
function in amblyopia, and support the association
between amblyopia and neurotransmitters reported in
the literature.
25. Pleoptic treatment
The of this treatment was to eradicate the eccentric
fixation.
Apparatus based on the ophthalmoscope principle
(the Euthyscope, the Projectoscope and the
Pleotophore) was used to expose the peripheral retina
to very bright light while protecting the macular area.
26. CAM visual stimulator
This apparatus was designed by Campbell and his co-
workers to treat amblyopia by intense visual stimulation
for short periods of time (Banks et al. 1978). Gratings of
different spatial frequency are rotated in front of the
amblyopic eye while the other eye is occluded.
This method was based on the knowledge that cortical
cells respond to specific line orientations and to certain
spatial frequencies; therefore rotation of gratings of
different spatial frequencies ensured that a large range of
cortical neurones was stimulated
27. Risks of occlusion
Intractable diplopia
Occlusion amblyopia.
Dissociation of latent/intermittent deviation.
DVD: The eye may elevate further.
Allergic response.
Danger socially due to disorientation.
Latent nystagmus (become manifist)
