GANGGUAN VISUAL &

SARAF KRANIAL

Dr. Ahmad Muzayyin, Sp.S., M.Kes.

ANATOMY

The Protective Structures of the Eye :

• The Orbit• The Lids• The Sclera

ANATOMY

The Anterior Segment of the Eye :

• The Cornea• The Aqueous Humor• The Iris• The Crystalline Lens &

Ciliary Muscle

ANATOMY

The Posterior Segment of the Eye :

• The Retina• The Vitreous Humor

ANATOMY

ANATOMY

The Visual System Pathways to the Brain:

• The Optic Nerves & Optic Tracts

• The Lateral Geniculate Nucleus

• The Visual Cortex

VISUAL SYSTEM

Optics:• The purpose of the eye is to bring image from

outside world onto retina.• Image is best focused on the fovea (has

highest conc. of receptor elements)• This is achieved by powerful lens system

(cornea and lens).

VISUAL SYSTEM

• Cornea = convex lens that brings object into focus & supplies 40 diopters

• Lens = adds additional convergence. The lens can also thicken (accommodation) which adds a few more diopters, supplying a sum of 20 diopters.

• Total = 60 d

Vision disturbance

• Emmetropia (normal vision): cornea/lens system focuses images on the retina.

• Myopia (nearsightedness): cornea/lens system focuses images in front of the retina

• Hyperopia (farsightedness): cornea/lens system focuses images behind the retina

• Presbyopia (“old eyes”): Lens begins to stiffen (age >40) and loses the ability to accommodate (i.e. to focus on images closer than 30 feet, need reading glasses).

Lesions in Visual Pathway

• Blindness/scotoma affecting only one eye = lesion in the Eye (such as damaged retina or ophthalmic artery), the optic nerve, or optic neuritis (as in MS), or an optic tumor.

• Blindness/scotoma affecting different visual fields in each eye = lesion at Optic chiasm - Bitemporal hemi-anopsia (loss of temporal visual fields) = medial damage chiasm… which means loss of crossed fibers (Causes: pituitary tumor or aneurysm of ACA).- Unilateral loss of nasal visual field (macular region) = lateral damage at chiasm… which is a loss of uncrossed fibers (Cause: carotid aneurysm).

Lesions in Visual Pathway

• Blindness/scotoma affecting same visual field in each eye (also known as: Homonymous Hemi-anopsia) = lesion central to the optic chiasm. (Possible causes (all unilateral): lesion of optic tract, lesion of LGN, lesion beyond LGN).

• Blindness/scotoma affecting just a portion of visual field in each eye = lesion in Optic radiation.- Superior Quadrant Anopsia (as in #5) = lesion of temporal lobe (Meyers Loop… supplied by MCA).- Inferior Quadrant Anopsia = lesion of parietal lobe (supplied by PCA).

Lesions in Visual Pathway

• Blindness/scotoma sparing central visual field in each eye (Macular sparing Hemianopia) = lesion involving Visual cortex.- Usually result in incomplete visual loss w/ macular sparing. The macular region is disproportionately represented in the cortex, so an incomplete disruption of function is likely to allow some macular vision to remain.

- Common vascular lesions: PCA or MCA - Lesions: - Superior Quadrant Anopsia = Below calcarine fissure - Inferior Quadrant Anopsia = Above calcarine fissure

Lesions in Visual Pathway