reclaim the periphery - new approaches to old issues

7/28/2019 Reclaim the Periphery - New Approaches to Old Issues.

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Reclaim the periphery!New approaches to old issues

Lars Frisn

Institute of Neuroscience andPhysiology/OphthalmologyGteborg University, Sweden


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CAP

Terraincognita

Kinetic


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By definition, contractions proceed centripetally.Periphery test is required for early diagnosis.


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Generally, it seems reasonable toexpect that any progressive

disorder that ends up in a centralfield remnant should involve somecontraction and/or peripheraldepression at an early stage


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Progressive concentric depression & contraction.Periphery test may aid early diagnosis.


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Concentric visual field contractions

- Optic nerve hypoplasia

- Vigabatrin toxicity

- Idiopathic

- Fictitious- Somatoform (functional,

hysterical

)

- Fatigue

- Perioptic neuropathy

- Chronic papilledema

- Glaucoma

- Tapetoretinal degenerations

- Drusen of the nerve head


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- Anterior V1: loss of temporal crescent

Diagnosis requires periphery test

Examples oflocalized contractions


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- lateral geniculate body


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Retinotopy is less clear for the pathways

- good peripheral tests may well be useful


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- optic nerve hypoplasia

Frisn & Holmegaard: Spectrum of optic nerve hypoplasia.

Br J Ophthalmol. 1978; 62:7-15.


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Conditions of recent interest

- epilepsy surgery -> 50 (-100) % VFD

- vigabatrin toxicity -> ~ 50 (-100) % VFD


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Meyers loop

Centennial jubilee coming up!

Adolph Meyer

The connections of the occipital lobes andthe present status of the cerebral visualaffections

Trans Ass Am Physicians 22: 716, 1907


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Williams, Gluhbegovic &Jew: The Human Brain.Harper & Row, 1980

Klingler & Ludwig:Atlas Cerebri Humani.

Karger, 1956

Technique: teasingfreeze-thawed tissue


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Falconer & Wilson 1958 Van Buren & Baldwin 1958

Barton et al. Brain 128: 2123, 2005


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Magnetic resonance tractography

Nilsson, Starck, Ljungberg, Rydenhag & Frisn: Tractographyof the optic radiation after temporal lobe resection (in prep)


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Vigabatrin (Sabril, Sabrilex)

- partial epilepsy- pediatric epilepsyviGABAtrin (gamma-amino-butyric acid)transferase inhibitor

Vigabatrin is toxic to retinal ganglion cellsand/or their axons


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Concentric contraction & peripheral depression- central field remains largely normal


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C-shaped pattern of RNFL atrophyFrisn & Malmgren: Characterization of vigabatrin-associated optic atrophy.

Acta Ophthalmol Scand 81: 466, 2003


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Inclusion of peripheral field data shouldhelp illuminate relationships to opticdisk and nerve fiber layer parameters

~ 1/3 of RNFL axons belong to retinalganglion cells located outside 30


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Periphery is important

What determines the periphery ?

How to access the periphery ?


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For concentric contractions/depressions:focus on the nasal &temporal periphery

Outer limits with and without extra-polarfixation marks and retraction of eyelids:

25%


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Outer limit only is generally inefficient

Aim to assess border zone, i e, slope


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15 LCD screen at 0.25 m distance canaccess 60 - 120 of horizontal eccentricity


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LCD/CRT-based perimeters


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.

Rarebit micro dot 0.5 x MAR


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HRP, normal eye, right temporal periphery


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Motion perimetry, right nasal periphery(courtesy of Younger & Wall)

Normal

Ocular hypertension


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Rarebit test principles

- use stimuli of minimal subtense(ideally smaller than receptive fields),

- at high & fixed contrast (easy to see)

- check once only for the presence offunction (no thresholding),

- in ever-new, non-overlapping locations;

- calculate Hit Rate =

- exposed briefly (to negate sweep gains),

sum seensum shown


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Normal eyes Subtlecompressionof the chiasm

Rarebit perimetry, right temporal periphery


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3 subjects treated with vigabatrin, ordered bycumulative dose.

Rarebit perimetry, right nasal periphery


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Frisn L: Vigabatrin-associated loss of vision: rarebit perimetry illuminatesdose-damage relationship. Acta Ophthalmol Scand 82: 54, 2004

Rarebit perimetry, ctd


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Blum RG, Gates LK, Jamed BRHow important are peripheral fields?

Arch Ophthalmol 61: 1 8, 1959

- Arc perimeter: 2 mm white target

- 72 (seventy-two!!) examiners

- 3078 eyes

- Tangent screen: 1 mm white target at 1 m


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Reclaim the periphery!

The end


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reclaim the periphery - new approaches to old issues

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