Dr. Natasha Healey PhD BSc ( Hons ) MCOptom 31 st May 2014

transcript

Dr. Natasha Healey PhD BSc (Hons) MCOptom

31st May 2014

Dr Julie McClelland, Dr Kathryn Saunders, Prof Jonathan Jackson, Ms Eibhlin McLoone

The Northern Ireland Nystagmus & Albinism Study

The NINA StudyThe NINA Study

ContentsAlbinism

- Background and subtypes

- Ocular Features

- Visual Symptoms

Northern Ireland Nystagmus & Albinism (NINA) Study

- Background

- Results

Background

Albinism term used to describe a group of disorders with absent or reduced melanin production

Results in hypopigmentation of the hair, skin and eyes

Prevalence: 1 in 20,000 worldwide 1 in 10,000 **N. Ireland

** NEW Results

AlbinismAlbinism2 broad categories exist:

Albinism Subtype

Category Sub-category

OCA1OCA1A

OA OA1 Several others

OCA1AOCA Type

Cause Pigment Birth appearance

Adult appearance

OCA1A tyrosinase negative OCA

Mutation of tyrosinase gene

Nil •Snow white hair

•white pale skin

•pale blue/violet irides

No change

Skin does not tan

OCA1BOCA Type

Adult appearance

OCA1B Reduced function- tyrosinase enzyme is minimally active

Varies (normal to minimal)

Same as OCA1A

•Hair and iridies can darken with age

•Eyelashes darker than eyebrows/hair

•Skin may tan / develop freckles

OCA2OCA Type

Adult appearance

OCA2 •Normal tyrosinase activity

•defective trans-membrane protein

Varies •Hair / eyes pigmented at birth

•Hair colour at birth can range (light blonde-brown)

•Similar to OCA1B but in pigment is less pronounced

•Pigment can remain unchanged

OCA 3 Common in African & Papua

New Guinean populations. Brick reddish skin, hair and iris.

OCA 4 Mainly found in Japanese / Korean populations Physical appearance often indistinguishable from

OCA1B or OCA2.

Secondary OCA Blood clotting or immune disorders, more frequent in

Puerto Rico, Holland & Switzerland.

Eye muscle

The Eye

Characteristic Ocular Features• Iris transillumination*

Eye muscle

The Eye

• Foveal hypoplasia* **NEW FINDINGS

Eye muscle

The Eye

‘typical’ fovea Foveal Hypoplasia‘absent fovea’

• Foveal hypoplasia*

• Fundal hypopigmentation*

Typical fundus colour fundus hypopigmention

• Macular transparency

• Optic nerve hypoplasia

• Anomalous retinal vessel presence in the foveal avascular area

Typical fundus colour fundus hypopigmention

• Macular transparency

• Optic nerve hypoplasia

• Anomalous retinal vessel presence in the foveal avascular area

• Abnormal misrouting of retinal ganglion cell axons at the optic

chiasm (VEP asymmetry)

‘Typical’ Visual Pathway: 60% fibres cross, 40% remain uncrossed

Typical Visual Pathway: 60% fibres cross, 40% remain uncrossed

Albinism: Higher percentage of fibres cross (95%), 5% uncrossed

• Reduced visual acuity

Characteristic Visual Symptoms

• High refractive errors

No Refractive Error •Eye that does not need glasses

No Refractive Error •Eye that does not need glass•Light / image rays focused perfectly on fovea / retina

Long Sighted Eye•Hypermetropia•Light/image focused behind retina

Long Sighted Eye•Hypermetropia•Eye needs PLUS lenses to focus light/image on retina

Short Sighted Eye•Myopia•Light / image is focused in front of the retina

Short Sighted Eye•Myopia•Eye needs MINUS lenses to focus light/image on retina

• Reduced contrast sensitivity

• Nystagmus

• Photophobia

• Nystagmus

• Photophobia

• Reduced or absent stereoacuity

• Nystagmus

• Photophobia

• Amblyopia

• Nystagmus

• Photophobia

• Amblyopia

• Strabismus

The Northern Ireland Nystagmus & Albinism (NINA) Study

The NINA StudyAutumn 2008- Spring 2012

Location:

Royal Group of Hospitals

Altnagelvin Area Hospital

Recruited:

105 participants (age range 4.5 months-47 years)

Albinism n=73

ICN n=32 (control group)

Retrospective analysis (n=147 medical files, 1986-2010)

Control GroupIdiopathic congenital nystagmus (ICN)

Nystagmus may also occur in isolation

Onset prior to 6 months of age

Normal ocular and neurological anatomy

MethodRefractive Error: strict cycloplegic protocols

Visual acuity: age appropriate tests

Nystagmus assessment : video recorded/graded

Corneal curvature: Nidek Hand-held keratometer

Eye muscle

Axial Length: IOL Master (NC) Biometer

Eye muscle

Corneal curvature: Nidek Hand-held keratometerIOL Master (NC) Biometer

Axial Length:

Contrast Sensitivity & Straylight: -Pelli Robson Chart - Straylight meter

Axial Length: IOL Master (NC) Biometer

Contrast Sensitivity: Pelli Robson Chart

Foveal imaging: SD-OCT

Eye muscle

Prevalence of Albinism

In N. Ireland

•Worldwide prevalence 1 in 20,000•N. Ireland prevalence 1 in 10,000

•New NINA Study Results albinism prevalence in N. Ireland

1 in 4,500 – 6,000

•published March 2014, British Journal of Ophthalmology

1 in 4,500 – 6,000

NINA Study has highlighted:• Public health issue- with higher numbers than services are planned for

•Numbers need taken into consideration when planning future service- eye appointments, funding for benefits, classroom assistants etc

•NINA suggest this underestimation of albinism prevalence is not an isolated case, suspecting worldwide figures to be erronous

The Significance of Foveal Hypoplasia

Eye muscle

Normal Retinal Development

•Fovea begins @ 25 weeks gestation

•Continues to develop until 15-45 months of age

•During this time the foveal cells change shape and mature

typical fovea Foveal hypoplasia: OCA/OA

Foveal Morphology ResultsSpectrum of foveal hypoplasia occurred

Examples of Foveal Hypoplasia

Grade of foveal hypoplasia was statistically significantly related to Visual Acuity (Agreement with Thomas et al., (2011)

Poorest VA (mean VA 6/36) was associated with the severest foveal hypoplasia

NEW NINA Findings:Highest refractive error (highest hypermetropia) was

associated with the severest foveal hypoplasia

Grade of foveal hypoplasia was statistically significantly related to Visual Acuity (Agreement with Thomas et al., (2011)

Poorest VA (mean VA 6/36) was associated with the severest foveal hypoplasia

NEW NINA Findings:Highest refractive error was associated with the severest

foveal hypoplasia - published April 2013, Investigative Ophthalmology & Visual Science

Refractive Error

Previous studies of refractive error in albinism Author Location Subject

numbersAge range (years)

Most prevalent type of refractive error

Wildsoet et al 200027 Boston 25 3-51 Long sighted

Edmunds 194932 New York 16 7-45 Long sighted

Mvogo et al 199933 Cameroon 42 Not available Short sighted with astigmatism

Loshin and Browning 1983 34

Not available 8 Not available Long sighted

Nathan et al 198535 Australia 35 1-16 Long sighted

Perez-Carpinell et al 198231

Spain 9 7-39 Short sighted

Sampath and Bedell 200236

USA 19 10-35 Long sighted

Kasmann et al 199637 Germany 68 0.5-78 Link between short sight and OCA1

Refractive Error

Long sightedEye length typical Large range of refractive errors existedHigh horizontal astigmatism

Why are the high levels of refractive error present?Typically at birth babies have high levels of long

sightedness and astigmatism

sightedness and astigmatismTypically these levels decrease over the first 8 years

of life

sightedness and astigmatismThese levels decrease over the first 8 years of lifeProcess is called ‘Emmetropisation’

New: NINA study has found that the high levels

found at birth do not appear to decrease as much

as we would expect over the first 8 years of life.

Another important feature the NINA Study has found is:

That some element of astigmatism in albinism is

congenital (higher at birth than typical baby eye)

Therefore are not solely a mechanical consequence of nystagmus

Recommend, if have astigmatism to wear glasses as early as possible, don’t wait and to wear full time.

Another important feature the NINA Study has found is:

That some element of astigmatism in albinism is

congenital (higher at birth than typical baby eye)

Therefore are not solely a mechanical consequence of nystagmus

Future ResearchNINA Study Findings currently in process for

publication:

1.Corneal Astigmatism

2.Questioning SSI and SI Categories for Albinism

- worldwide call for further research

3.Advanced Clinical Guidelines for Eye care in Albinism

4.**Need for future research in genetics, and foveal hypoplasia during gestation and infancy

NINA Study SummaryPrevalence of Albinism is greater than expected in NI, and

also possibly worldwide

Need to look at public spending in this area

Role of Foveal Hyoplasia in Visual Acuity and Refractive Error

Longsighted with horizontal astigmatism most common, suggesting glasses from a very early age

Astigmatism generally corneal and some already there before birth

Re-diagnosed some of those participating in the ‘control group’

NINA OutcomesClinical recommendationsProvided answers to worldwide questionsIncreased awareness Increased awareness of support parents requireIncreased awareness of Albinism Fellowship and

Angel Eyes Charities (NI)Highlighted need for future researchFurther publications pending

Last thing to say is a huge.....

Thank YouThank You

AcknowledgementsChildren, adults and parentsMs. E. McLooneMr. C.E. WilloughbyMs. R.BrennanDr. G. MahonDr. D. BurnsThe Low Vision Clinic, RGHDayward, RGHOptometry Clinic, AAHCharities (AE/AF)University of UlsterDepartment of Education & Learning

Note: the author of this presentation does not give permission for its content/images to be copied or reused in any way.

Dr. Natasha Healey PhD BSc ( Hons ) MCOptom 31 st May 2014

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