RAO/RVO, TIAs/CVA, and ENT/Hearing-Balance — Comprehensive Lecture Notes

Retinal Artery Occlusion (RAO) and Retinal Vein Occlusion (RVO) — Lecture Notes

• Overview
  • Topics covered: retinal artery occlusion (RAO), retinal vein occlusion (RVO), transient ischemic attack (TIA), cerebrovascular accident (CVA), and a brief ear/nose module (hearing and balance).
  • Emphasis on signs, risk factors, patient education, and the imperfect, practice-based nature of medicine.

Retinal Artery Occlusion (RAO)

• Trigger and clinical course
  • If a patient rubs the eye during RAO, a clot can be propelled toward the brain, increasing the risk of stroke.
  • Consequence: stroke is a potential outcome of the embolic event.
  • The “minor” event discussed is TIA (transient ischemic attack).
  • RAO can be associated with a TIA; awareness of this link is important for providers.
  • RAO typically affects one eye (unilateral).
• TIAs and CVA definitions (per lecture)
  • TIAs stand for Transient Ischemic Attack.
  • TIAs dissolve within twenty-four hours; if symptoms persist beyond 24 hours, that is considered a stroke.
  • Some clinicians refer to stroke as a Cerebrovascular Accident (CVA).
  • ext{TIA}
    ightarrow ext{resolves within } 24 ext{ hours} \ ext{If > } 24 ext{ hours, it is a stroke (CVA).}
• Patient symptoms and behavior
  • Temporary blindness in one eye can occur; rubbing the eye is a natural reflex during visual disturbance.
  • Advice: when vision is unclear or temporarily lost, do not rub the eye.
  • The reflexive nature of rubbing is acknowledged; patients may not stop rubbing even with instructions.
• Risk factors and demographics
  • Most common risk factors: age (older individuals).
  • Diabetes increases risk; older age with diabetes markedly increases risk.
• Eye exam findings (RAO)
  • Retina is pale due to ischemia.
  • Classic exam sign: cherry red spot at the fovea, contrasting with a pale peripheral retina.
  • RAO is described as painless.
• Exam concepts and anatomy
  • In the ocular exam, the retina can be viewed to assess arteries, veins, and the optic nerve head.
  • The lecturer mentions the acronym “VAN” (Vein, Artery, Nerve) as a mnemonic during retinal examination.
  • The optic disc (head of the nerve) can be examined with ophthalmoscopy (the lecturer quips about a $200 device).
• Medical philosophy and uncertainty
  • Medicine is described as a practice rather than an exact science; many mechanisms and outcomes are not fully predictable.
  • An example given: predicting why a smoker develops lung cancer after years is complex and not fully explained—illustrating the imperfect nature of medical knowledge.
• Practical takeaways for RAO
  • RAO is dangerous due to the risk of stroke/TIA.
  • Key signs: painless, sudden vision loss in one eye; pale retina with possible cherry red spot.
  • Immediate consideration of cerebrovascular risk and urgent evaluation is warranted.

Retinal Vein Occlusion (RVO)

• Presentation and signs
  • RVO presents with engorged retinal veins and edema, producing a congested retina often described by the term "blood and thunder." This is a hallmark of venous congestion and hemorrhages.
  • The eye in RVO is typically painless; if pain is present, it is not the usual course described in this lecture.
• Pathophysiology
  • Vein occlusion impedes venous outflow, causing venous dilation/engorgement, edema, and retinal hemorrhages, leading to visual disturbance.
• Comparison with RAO
  • RAO: arterial occlusion → pale retina and cherry red spot; usually painless.
  • RVO: venous occlusion → engorged veins with edema/hemorrhages; described as "blood and thunder"; typically painless in this lecture.
• Exam terminology
  • The phrase "blood and thunder" is used to describe the congested retina seen with RVO.
  • As with RAO, the retinal exam is performed via ophthalmoscopy; the anatomy of veins, arteries, and the optic nerve is relevant (VAN framework).
• Summary points for RVO
  • RVO results from venous occlusion with venous engorgement and edema; signs include a congested retina with hemorrhages.
  • Pain is not the typical presentation in this lecture.
  • Recognize and differentiate from RAO by looking for the pale retina with cherry red spot (RAO) versus the congested, hemorrhagic retina (RVO).

Eye Anatomy and Fundoscopic Exam Pointers

• Fundoscopy and nerve head
  • The retina contains arteries, veins, and the optic nerve head; the examiner often assesses these structures during fundoscopic exam.
  • The optic disc is described as the head of the nerve during teaching; this is a commonly used teaching point in fundoscopy.
• Terminology to remember
  • Cherry red spot: classic RAO sign.
  • Blood and thunder: classic RVO sign (venous congestion with hemorrhages).
  • VAN: mnemonic for Vein, Artery, Nerve during retinal examination.
• Tools of the trade
  • Ophthalmoscopy is the primary method to visualize the retina, vessels, and optic disc.
  • The lecturer mentions a device (humorously described as a $200 device) used to view the retina.

Ear and Nose Module — Hearing and Balance

• Hearing pathway basics
  • Hearing involvement is described as a sensorineural process, implicating cranial nerve VIII (the vestibulocochlear nerve).
  • The pathway concept includes distinction between conduction and sensorineural components (air conduction vs. bone conduction).
• Cranial nerve VIII
  • Cranial nerve VIII (vestibulocochlear nerve) is the main nerve involved in hearing in this module.
• Conductive testing methods
  • Air conduction and bone conduction are used to assess hearing.
  • A tuning fork is highlighted as a practical tool in this context.
• Balance and the brain
  • Balance relies on multiple components:
  • Vestibular apparatus in the inner ear.
  • Cerebellum in the brain.
  • Visual input from the eyes.
  • Proprioception from the limbs.
  • Proper balance requires integration of these inputs; vision, proprioception, and vestibular input all contribute.
• Practical takeaways
  • The tuning fork assay and the distinction between air and bone conduction are emphasized for basic auditory assessment.
  • The ear plays a crucial role in balance, which is coordinated with the brain and eyes.

Synthesis and Exam-oriented Cues

• Key clinical contrasts
  • RAO: sudden, painless, usually monocular vision loss; pale retina; cherry red spot.
  • RVO: sudden, painless vision disturbance; engorged veins with edema and hemorrhages; "blood and thunder" appearance.
  • Both RAO and RVO carry cerebrovascular risk and may relate to TIAs or CVAs.
• Risk factors to memorize
  • Age (older adults) and diabetes significantly increase risk for RAO and RVO.
• Patient education points to emphasize
  • Do not rub the eye during transient vision loss.
  • Acknowledge the imperfect nature of medicine; emphasize quick evaluation and follow-up due to stroke risk.
• Terminology to be fluent in
  • TIA, CVA ( cerebrovascular accident ), RAO, RVO, cherry red spot, blood and thunder, VAN, optic disc.
• Final clinical message from the session
  • Ophthalmic emergencies require prompt recognition and understanding of systemic vascular risk.
  • The material also reinforces that clinical medicine is a practice with uncertainties, not an exact science.

Quick Reference Formulas and Facts

• TIAs vs CVA timing:
  • TIAs resolve within 24 ext{ hours}; after that window, the event is categorized as a stroke (CVA).
• Classic signs:
  • RAO: painless, unilateral vision loss; pale retina; cherry red spot.
  • RVO: painless vision disturbance; engorged veins; edema; hemorrhages; “blood and thunder.”