Visual Fields III

What does the superior retina relate to ?

• inferior visual field

How do macular fibres sit?

• centrally → Papilomacular Bundle

what is the structure of the fibres at the optic chiasm?

• macula fibres move to centre

What happens at the Optic chiasm?

• NASAL fibres CROSS OVER

• inferior Nasal fibres → anterior chiasm

• Superior nasal fibres → posterior chiasm

temporal fibres stay at same side

What happens at the optic tract?

Macular fibres → crossed (nasal retina) + uncrossed (temporal)

Superior Peripheral → fibres from superior retina = inferior visual field

• Medial

• Ipsilateral Sup-Temp

• Controlateral Sup-Nasal

Inferior Peripheral

Lateral

Ipsilateral Inf-temp

Controlateral Inf-Nasal

What happens at the LGN?

• More organisation here

• 6 layers

• layers 1,4 + 6

→ crossed nasal fibres

→ Controlateral retina

• layers 2,3 and 5

→ uncrossed (temporal)

Ipsilateral retina → same side

Where are the Magnocellular layers?

• Layers 1+2

• Magno cells:

• Retinal rods

• magno ganglion cells

which layers are the parvocellular layers?

• layers 3-6

Retinal Cones

Parvo Ganglion cells

where are the Koniocellular layers?

• in between layers 1-6

• ganglion cells → process colour

what is the path of optic radiations that represent inferior retina?

• Fibres leaving lateral LGN

• Inferior radiations

• Head to OCCIPITAL LOBE via temporal lobe

• form Meyer loops along the way

What is the path involving superior radiations?

• Fibres leave medial LGN

• represent superior retina

• superior radiations → Parietal lobe

where are the macular fibres situated?

• between superior + inferior fibres

Primary Visual Cortex - superior radiations

• Occipital Lobe

• Cuneus gyrus → above calcarine fissure

• superior radiation terminated at cuneus gyrus

PVC→ Inferior radiations

• Occipital lobe

• Lingual gyrus → below calcarine fissure

• lingual → inferior radiation terminated

where are the macula fibres in the primary visual cortex?

• more posterior the cortex , relates more to central vision

Superior Macular fibres → Cuneus gyrus

Inferior Macular fibres → Lingual Gyrus

What is a Haeminopia?

• respects vertical midline

• affects ½ of VF → nasally or temporally

what is heterotonyomus ?

• affects opposite sides of space

what conditions relate to horizontal midline being obeyed?

• Retinal

• Glaucoma , MD, Retinal detachment

what conditions associated with vertical midline?

• Post retinal

• emergency if vertical midline until proven otherwise

• optic nerve , optic chiasm , LGN

What is a Junctional Scotoma?

• affects both eyes

• meningioma compressing on optic nerve just as its beginning to enter optic chiasm

• affects superior field , LVF completely affected

Pituiatry Tumour?

= more noticeable when one eye closed → notice ½ vision of one eye missing

• Bitemporal Haeminopia

what is Amsler grid used for?

• quick assessment of Mucular fucntion

• AMD

alternative to 10-2, can be used to self monitor at home

• used to look for scotomas+ metamorphopsia

what is Amsler chart No 1?

• Standard chart

• 5mm squares

• Central white fixation target

• Each square subtends 1 degree when held at 30cm

• white on black more sensitive than black on white

What is Chart NO. 2?

Diagonal lines assist with fixation → guidelines to look in centre

What is Chart No.3?

• RED GRID

• useful for

- Toxic amblyopia

- optic neuritis

What is Chart Number 4?

• Scattered white dots

• similar to chart 1 for relative scotoma detection

• Can NOT detect metamorphopsia

what is Chart 5 used for?

• can be rotated to change orientation of lines

• Investigates metamorphopsia at dif meridians

chart 6

• similar to 5

• black lines on white

• additional lines that subtend 0.5 degrees → greater sensitivity

chart 7

• 0.5 degrees for central 8 degrees

• used for more subtle macular disease → could be missed by 1 degree square