Macular and RNFL thickness evaluation in unilateral Amblyopia using OCT

1. EVALUATION OF MACULAR AND RETINAL NERVE
FIBRE LAYER THICKNESS IN UNILATERAL
AMBLYOPIC PATIENTS USING OPTICAL COHERENCE
TOMOGRAPHY
Presenter- Dr. Radha Mathur
Co-authors- Dr. Ashish Chander, Dr. Gopesh Mehrotra, Dr. Ranjot Kour
TMMC & RC, Moradabad, U.P.

2. INTRODUCTION
• Amblyopia or lazy eye is a common cause of preventable monocular vision loss in children and young
adults.1
• It is defined as “unilateral or bilateral decrease in best corrected central visual acuity caused by form vision
deprivation and/or abnormal binocular communication, without any organic cause to correspond with visual
loss’’. 2
• It is often developed during first 2-3 years of the postnatal period; however, it may be developed up to the
age of 8 -9 years. 3
• Amblyopia possess a high lifetime risk ( 3 times to general population) of severe vision loss of
corresponding eye, of at least 1.2%. 4
1. Hills A, Flynn JT, Hawkins BS. The evolving concept of amblyopia: a challenge to epidemologists. Am J Epidemiol 1983 Aug; 118(2):192-205.
2. Von Noorden G, Campos E. Binocular vision and ocular motility: Theory and management of strabismus. 6th ed. St. Louis. The Mosby, 2002: 246-97.
3. Alotaibi AG, Al Enazib. Unilateral amblyopia: Optical coherence tomography findings. Saudi J Ophthalmol 2011 Oct; 25(4): 405-9.
4. Rahi J, Logan S, Timms C, Russell-Eggitt I, Taylor D, Borja MC. Risk, causes and outcomes of visual impairment after loss of vision in the non- amblyopic eye: a population based study. The
Lancet 2002;360(9333):597-602.

3.  The common risk factors for amblyopia are 5-7
• Premature birth
• small for gestational age
• developmental delay
• having a first degree relative with amblyopia
 Environmental risk factors related to amblyopia are
• maternal smoking,
• drug or alcohol abuse in pregnancy 8,9
5. Mohan K, Dhankar V, Sharma A. Visual acuities after levodopa administration in amblyopia. J Pediatr Ophthalmol Strabismus 2001;38(2):62-7.
6. Repka MX, Kraker RT, Beck RW, Atkinson CS, Bacal DA, Bremer DL, et al. Pilot study of levodopa dose as treatment for residual amblyopia in children aged 8 years to younger
than 18 years. Arch Ophthalmol 2010;128(9):1215-7.
7. Dadeya S, Vats P, Malik KP. Levodopa/carbidopa in the treatment of amblyopia. JAAPOS 2009;46(2):87-90.
8. Hakim RB, Tielsch JM. Maternal cigratte smoking during pregnancy. A risk factor for childhood strabismus. Arch ophthalmol 1992 oct;110(10):1459-62.
9.. Chew E, Remaley NA, Tamboli A, Zhao J, Podgor MJ, Klebanoff M. Risk factors for esotropia and exotropia. Arch Ophthalmol 1994;112:1349-55

4. • UNILATERALAMBLYOPIA has 2 main types:
• Other forms include:
• Combined amblyopia
ANISOMETROPIC AMBLYOPIA
difference in state of refraction is
minimum 1 D or more between 2
eyes.10
STRABISMIC AMBLYOPIA
due to constantly unaligned optical axis;
amount of divergence is not related to development
and severity of amblyopia.
DEPRIVATIONALAMBLYOPIA
associated with vision obstructing disorders
blocking the visual axis and
deprive retina to get clear image 11
AMETROPIC AMBLYOPIA
Takes place because of uncorrected bilateral high
refractive error
10. Braverman RS. Types of Amblyopia. Am Acad Ophthalmol 2015 Oct 21.
11. Friedman DS, Repka MX, Katz J, Giordano L, Ibironke J, Hawse P, et al. Prevalance of amblyopia and strabismus in white and African American children aged 6 through 71 months:
the Baltimore Pediatric Eye Disease Study. Ophthalmology 2009; 116(11):2128-2134.

5.  Cell density of the retinal ganglion cell layer 12 Count of axons of human optic nerve 13
• At 18 – 30 weeks 2.2-2.5million cells At 16-17 weeks of pregnancy 3.7 million cells
• Postnatally 1.5-1.7 million cells Adult 1.1 million cells
 If amblyopia affects the process of postnatal decrease of ganglionic cells; then RNFL thickness may be thicker
than that in normal eye 14
 Macular hypoplasia and underlying structural abnormality can be one of cause for the bad prognosis for treatment
outcome. Therefore macular thickness in amblyopia needs to be investigated in detail to improve the treatment
outcome
 OCT has become extensively popular for assessing optic nerve disorders by precisely and reproducibly
measuring the retinal nerve fiber layer (RNFL) and ganglion cell layer thickness
12. Provis JM, VanDriel D, Billson FA, Russell P. Development of human retina: Patterns of cell distribution and redistribution in the ganglion cell layer. J Comp Neurol 1985 Mar
22;233(4):429-51.
13.Provis JM, VanDriel D, Billson FA, Russell P. Human fetal optic nerve: Overproduction and elimination of retinal axons during development. J Comp Neurol 1985 Aug 1;238(1):92-100.
14. Greenfield DS, Huang HR, Knighton RW. Effect of corneal polarization axis on assessment of retinal nerve fibre layer thickness by scanning laser polarimetry. Am J Ophthalmol 2000
Jun;129(6):715-722

6. AIMS & OBJECTIVES
AIM:
• To evaluate the macular and the retinal nerve fibre layer thickness in patients with unilateral amblyopia.
OBJECTIVES:
1. To measure macular thickness in unilateral amblyopic patients.
2. To measure retinal nerve fibre layer thickness in unilateral amblyopic patients.
3. To compare macular and retinal nerve fibre layer thickness of amblyopic eye to the normal eye.

7. MATERIALS & METHODS
• The study was carried out during the period of Jan 2019- Dec 2019.
• Informed consent was obtained from the subjects after explanation of the nature and possible consequences
of the study.
• Total 94 subjects were included into study who were diagnosed with unilateral amblyopia.

8. INCLUSION CRITERIA EXCLUSION CRITERIA
1. All patients of either gender between
18 -45 years of age
2. Patients with unilateral amblyopia
(difference in visual acuity was at least two
lines between the normal and amblyopic
eye on Snellen’s visual acuity charts)
1. Patients with any other significant
ocular/systemic condition which may hinder
examination on OCT.
2. Patients with any other systemic/ocular co-
morbidities that could substantially effect the
macular or RNFL thickness
3. Patients with any ocular trauma .
4. Patients with history of previous intraocular or
refractive surgery.
5. OCT showing abnormal macular and RNFL
thickness in normal eye.
6. Patient whose pupillary dilation is insufficient
to perform OCT.
7. Patient not able to maintain steady fixation
behind the OCT camera.
8. Patients not signing the informed consent.

9. EXAMINATION
Detailed
history
BCVA
IOP
Anterior segment examination Posterior Segment examination
OCT
RNFL T, Macular thickness
Systemic history
Ocular history
Snellen’s chart
Goldmann applanation tonometer
Slit Lamp examination with Mydriasis
Peripapillary RNFL thickness :
Optic Disc Cube 200x200 protocol.
Mean RNFL thickness of 360 degrees and
each quadrant was derived.
Macular thickness :
macular cube scan 512x128 protocol.
Zeiss Cirrus HD 500

10. STATISTICAL ANALYSIS
• Data was analyzed with IBM SPSS statistics software 23.0 Version.
• To describe the data descriptive statistics frequency analysis, percentage analysis was used for categorical
variables and the mean & S.D were used for continuous variables.
• To find the significant difference between the bivariate samples in Independent groups, the unpaired sample
t-test was used.
• In the above statistical tool the probability value of 0.05 was considered as significant level.

11. OBSERVATION & RESULTS
In our study we included total of 94 patients, among
them 60 were males & 34 were females
The age distribution of the study population was between
18-45 years with maximum patients in 21-30 years
94 normal fellow eyes with normal visual acuity
94 amblyopic eyes with visual acuity ranging from
6/12 to 6/60

12. Mean central macular thickness
p=0.343>0.05
no statistical significant difference
Similar studies by:
1. Yakar et al 15 -no significant difference ; study done in
anisometropic hyperopic amblyopes
2. Wang et al 16 –only 14 subjects with hyperopic
anisometropic amblyopia --no significant differences
15. Yakar K, Kan E, Alan A, Alp MH, Ceylan T. J Ophthalmol.2015;2015:946467.
16. Wang BZ, Taranath D. A comparison between amblyopic and normal fellow eye ocular architecture in children with hyperopic anisometropic amblyopia. JAAPOS 2012;16(5):428-430.

13. Mean average macular thickness
p=0.002<0.01
Highly significant difference
Similar studies by:
1. Dickmann et al 17 - higher thickness values of
macula and foveola in ‘strabismic’ amblyopic
eyes
2. Firat et al 18 also reported higher macular
thickness in amblyopic eyes versus fellow sound
eyes
17. Dickmann A,Petroni S, Perrotta V, Parrilla R, Aliberti S,Salerni A,et al. Measurement of retinal nerve fibre layer thickness, macular thickness, and foveal volume in amblyopic eyes using
spectral- domain optical coherence tomography. J AAPOS 2012 Feb;16(1):86-8.
18. Firat PG, Ozsoy E, Demirel S, Cumurcu T, Gunduz A. Evaluation of peripapillary retinal nerve fibre layer , macula and ganglion cell thickness in amblyopia using spectral optical coherence
tomography. Int J Ophthalmol 2013 Feb 18; 6(1):90-4.

14. Mean average RNFL Thickness
p=0.412>0.05
No statistical significant difference
Similar studies by:
• Andalib D et al (2013)19 No changes were seen in
peripapillary nerve fibre layer (p=0.55)
Contradictory result:
• Repka MX et al(2009)20 mean global RNFL
thickness of amblyopic eye was thicker than
corresponding eyes was (111.4 and 109.6μm, )
The difference may be a result of different sample
sizes, different ranges of age, and different OCT
devices in regard of technology and database.
19. Andalib D, Javadzadeh A, Nabai R, Amizadeh Y. Macular and retinal nerve fibre layer thickness in unilateral anisometropic or strabismic amblyopia. J Pediatr Ophthalmol
Strabismus 2013;50(4):218-221.
20.Repka MX, Kraker RT, Tamkins SM, Suh DW, Sala NA,Beck RW.Retinal nerve fibre layer thickness in amblyopic eyes. Am J Ophthalmol 2009;148(1):143-147.

15. Superior quadrant RNFL thickness
Inferior quadrant RNFL thickness

16. Temporal quadrant RNFL thickness
Nasal quadrant RNFL thickness

17. LIMITATIONS
1. The sample size was confined only to 94 amblyopic cases which did not allow segregation of the
patients into groups according to the type of amblyopia.
2. Absence of a controlled group to represent a reference to avoid any alterations that may occur to the
normal fellow eye in patients with amblyopia.

18. CONCLUSION
• Although amblyopia primarily affects the visual cortex, it also leads to secondary changes at retinal level.
• The RNFL thickness does not show corresponding outcomes with amblyopia and may actually be thinner
in amblyopes.
• The cause behind this can be racial difference or some other yet unknown factors.
• Further studies are warranted to establish retinal changes in amblyopia and to determine whether retinal
involvement has any effect on response to amblyopia therapy.

19. Thank You