Retinal Pathologies
Central Retinal Artery Occlusion
- In central retinal artery occlusion, there's sudden monocular vision loss: a “cherry-red” spot in the macula.
- In central retinal vein occlusion, there's retinal hemorrhage and venous engorgement.
Papilledema
Pressure along the optic nerve
- The meningeal layers transmit along the optic nerve. This is critical to understanding how increased intracranial pressure affects the optic nerve.
- Sclera transitions into:
- Dura mater (aka dural sheath)
- Arachnoid mater (aka arachnoid sheath)
- Pia mater lies along the surface of the optic nerve.
- Subarachnoid space exists between the arachnoid mater and pia mater, which allows increased intracranial pressure to translate along the optic nerve and impair its axoplasmic transport.
Papilledema
- Papilledema occurs from increased intracranial pressure.
- It refers to disc edema in the setting of increased intracranial pressure.
- Next, draw the retina of the right eye as a reddish circle: this is how we see it on ophthalmoscopy, called “fundoscopy”, because
- On the nasal side, we show the optic disc (aka the optic nerve head), which comprises the neuroretinal rim (which is pink) and the optic cup, a pale hole through which the central retinal vessels emanate.
- On the temporal side, we show the macula: in its center lies the fovea centralis.
- In papilledema, optic disc swelling manifests with an enlarged blind spot (the optic nerve head forms the blind spot in the visual field).
Glaucoma
- In glaucoma, there's optic disc atrophy manifests with thinning of the optic nerve head, typically from increased intraocular pressure (we address it in detail at the end).
Macular degeneration
- In macular degeneration, there's a loss of central vision.
- We divide macular degeneration into:
- Dry (nonexudative) degeneration for the slow deposition of extracellular material (it's yellowish on exam), and
- Wet (exudative) degeneration, which occurs from choroidal bleeding with rapid loss of vision.
Retinal detachment
- Retinal detachment manifests with crinkling of the fundus; the patient experiences loss of vision like a “curtain being drawn down.”
Diabetic retinopathy
- Diabetic retinopathy manifests as:
- Proliferative: chronic hypoxemia causes new vessel formation and retinal traction.
- Nonproliferative: damaged capillaries promote retinal hemorrhage.