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Vision Loss: Vascular vs Gradual Causes — MRCP Part 1

TL;DR:

For MRCP Part 1, the single most reliable way to approach vision loss is by time course. Sudden, painless loss is usually vascular and urgent; gradual loss over weeks to months points to degenerative, metabolic, or compressive causes. Examiners reward candidates who localise anatomically and recognise classic patterns rather than chasing rare diagnoses.


Why this topic matters for MRCP Part 1

Vision loss sits at the intersection of neurology, ophthalmology, vascular medicine, and endocrinology. In MRCP Part 1 questions, you are rarely asked to manage definitively—you are tested on recognition, localisation, and prioritisation.

Candidates commonly lose marks by:

  • Ignoring the tempo of vision loss

  • Confusing optic nerve disease with retinal pathology

  • Missing giant cell arteritis (GCA) in older patients

This article supports the MRCP Part 1 hub at👉 https://crackmedicine.com/mrcp-part-1/

and should be read alongside question practice from👉 https://crackmedicine.com/qbank/


First principle: classify by time course

Before considering detailed differentials, decide whether the vision loss is:

  • Sudden (minutes to hours) → think vascular or neurological

  • Gradual (weeks to months) → think degenerative, metabolic, compressive

Pain, laterality, and fundoscopy refine the diagnosis—but tempo comes first.

Vascular causes of vision loss (typically sudden)

Vascular causes are high-yield because they are common, time-critical, and pattern-based.

1. Central retinal artery occlusion (CRAO)

  • Onset: Sudden, profound

  • Pain: None

  • Laterality: Monocular

  • Fundoscopy: Pale retina with cherry-red spot

  • Associations: Atrial fibrillation, carotid disease

Exam pearl: CRAO is the ocular equivalent of a stroke.

2. Central retinal vein occlusion (CRVO)

  • Onset: Acute or subacute

  • Fundoscopy: “Blood and thunder” appearance

  • Risk factors: Hypertension, diabetes, glaucoma

CRVO causes blurring rather than complete blindness—an important discriminator from CRAO.

3. Anterior ischaemic optic neuropathy (AION)

Non-arteritic AION

  • Sudden, painless loss

  • Altitudinal visual field defect

  • Vascular risk factors

Arteritic AION (GCA-related)

  • Age >50

  • Headache, scalp tenderness, jaw claudication

  • Raised ESR/CRP

Never delay steroids for biopsy in suspected GCA.

4. Occipital lobe stroke

  • Deficit: Homonymous hemianopia

  • Visual acuity: Preserved

  • Fundoscopy: Normal initially

This is frequently mislabelled as “eye disease” in questions.

Gradual causes of vision loss

Gradual loss is usually painless and progressive.

1. Chronic open-angle glaucoma

  • Peripheral vision lost first

  • Cupped optic disc

  • Often asymptomatic until late

2. Diabetic retinopathy / maculopathy

  • Gradual central visual blurring

  • Microaneurysms, exudates, haemorrhages

  • Long-standing diabetes

3. Cataract

  • Progressive painless blur

  • Glare, reduced colour contrast

  • Reduced red reflex

Simple but frequently overlooked in exam stems.

4. Optic nerve compression (e.g. pituitary adenoma)

  • Progressive vision loss

  • Bitemporal hemianopia

  • Endocrine features may coexist

5. Retinitis pigmentosa

  • Night blindness

  • Tunnel vision

  • Bone-spicule pigmentation on fundoscopy


High-yield comparison table

Feature

Vascular vision loss

Gradual vision loss

Onset

Sudden (minutes–hours)

Weeks–months

Pain

Usually painless

Usually painless

Laterality

Often monocular

Mono- or binocular

Visual fields

Altitudinal / hemianopia

Peripheral constriction

Fundoscopy

Acute changes

Chronic changes

Exam priority

Emergency recognition

Pattern recognition

MRCP Part 1 study setup with notes on vascular and gradual causes of vision loss

Mini-case (MRCP style)

A 72-year-old woman presents with sudden painless loss of vision in her left eye. She has a new headache and pain when chewing. ESR is markedly raised.

Most appropriate immediate management?

A. Arrange temporal artery biopsyB. Start high-dose oral prednisoloneC. Start aspirin and statinD. MRI brainE. Observe and review

Correct answer: B — Start high-dose oral prednisolone

Explanation: This is classic giant cell arteritis with arteritic AION. Steroids must be started immediately to prevent vision loss in the other eye.


Five examiner traps to avoid

  • Assuming pain is always present in vascular causes

  • Missing GCA in patients >50 with vision loss

  • Forgetting that optic neuritis can have a normal fundus initially

  • Mislocalising binocular field loss as ocular disease

  • Over-diagnosing rare conditions instead of common vascular ones

Practical study checklist

  • ☐ Decide sudden vs gradual within 5 seconds

  • ☐ Localise: eye, optic nerve, chiasm, or brain

  • ☐ Screen older patients for GCA symptoms

  • ☐ Memorise fundoscopy patterns

  • ☐ Practise mixed questions in the MRCP question bank

You can test this systematically using:👉 https://crackmedicine.com/mock-tests/


FAQs

How do I quickly differentiate CRAO from optic neuritis?

CRAO is sudden and painless with a cherry-red spot. Optic neuritis causes pain on eye movement and often has a normal fundus early.

Why is GCA so heavily tested in MRCP Part 1?

Because it is common, catastrophic if missed, and requires immediate treatment before confirmation.

Does normal fundoscopy exclude optic nerve disease?

No. Retrobulbar optic neuritis can present with a normal fundus.

Is visual acuity always reduced in occipital stroke?

No. Visual acuity is often preserved; the deficit is in visual fields.


Ready to start?

Consolidate this topic with structured revision via the MRCP Part 1 overview, then reinforce pattern recognition using targeted MCQs and a timed mock test. Pair this post with sibling reading on neuro-localisation for best yield.


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