Episcleritis sceleritis conjunctivitis difference ak khurana
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I have rich content. Note: The library has Kanski's Clinical Ophthalmology (10th edition) but not AK Khurana specifically — however, the content from Kanski's is the authoritative ophthalmology reference. Let me now compile a comprehensive comparison.
Episcleritis vs Scleritis vs Conjunctivitis — Differential Comparison
Note: AK Khurana's Comprehensive Ophthalmology is not in this library's collection; the following is drawn from Kanski's Clinical Ophthalmology (10th ed.) and Rosen's Emergency Medicine, which cover this topic authoritatively and align with Khurana's teaching.
Anatomical Basis — Key to Understanding the Difference
Fig. 9.1 (A) Episcleritis — maximal vascular congestion in the superficial episcleral plexus:
Fig. 9.1 (B) Scleritis — scleral thickening with maximal congestion in the deep vascular plexus:
There are three vascular layers anterior to the equator:
- Conjunctival vessels — most superficial; arteries tortuous, veins straight
- Superficial episcleral plexus — straight, radial; congested in episcleritis
- Deep scleral vascular plexus — congested in scleritis; produces the characteristic purplish hue
Comparison Table
| Feature | Conjunctivitis | Episcleritis | Scleritis |
|---|---|---|---|
| Layer involved | Conjunctiva only | Episclera (between conjunctiva & Tenon's capsule) | Full thickness of sclera |
| Colour of redness | Bright red / pink | Salmon-pink to bright red | Deep purple-red/blue-red hue (best seen in daylight) |
| Discharge | Prominent (watery, mucoid, or purulent) | None | None |
| Pain | Gritty / foreign body sensation | Mild discomfort to grittiness; up to 50% painless | Severe, boring, deep pain radiating to temple, brow, jaw; nocturnal, wakes patient; poor response to analgesia |
| Tenderness | None | Mild, if any | Globe tenderness on palpation |
| Nodule | None | Present in nodular type (moveable over sclera) | Present in nodular type (immovable, elevated on slit-lamp) |
| Visual acuity | Normal | Normal | May be reduced |
| Photophobia | May be present | Occasional | Common |
| Chemosis | Common | Rare | Can occur |
| Anterior uveitis | No | Very rare | Can occur as complication |
| Phenylephrine 10% test | Blanches vessels | Blanches superficial episcleral vessels | Does NOT blanch deep plexus vessels |
| Phenylephrine 2.5% test | Blanches conjunctival & superficial episcleral | Blanches | Does not blanch deep plexus |
| Slit-lamp beam | No displacement | Deep beam not displaced above scleral surface | Deep beam elevated (anterior scleral surface raised) |
| Systemic associations | Usually infectious; no major systemic disease | Minority: RA, gout, IBD, HZV, rosacea | Strongly associated: RA, Wegener's (GPA), polyarteritis nodosa, SLE, IBD, ankylosing spondylitis |
| Course | Self-limiting (days) | Self-limiting; lasts days to 3 weeks; recurrent | Chronic, mean ~6 years; can progress to necrotizing |
| Visual threat | Rare (corneal complications) | No | Yes — can cause scleral necrosis, uveitis, cataract, glaucoma, vision loss |
| Treatment | Topical antibiotics / antivirals; antihistamines | Cool compresses; topical steroid or NSAID; oral NSAID occasionally | Oral NSAIDs → oral corticosteroids → immunosuppressants (methotrexate, azathioprine) → biologics (adalimumab, infliximab) |
Episcleritis in Detail
Types:
- Simple episcleritis (75%): Sectoral or diffuse redness; peaks at 24 hrs, fades over days; frequently bilateral (>50%); recurrent in 60%
- Nodular episcleritis (25%): More prolonged; node is tender, salmon-pink, moveable over sclera; no slit-lamp elevation of deep beam
Key point: Topical phenylephrine 2.5% constricts conjunctival and superficial episcleral vessels → redness blanches in episcleritis.
Scleritis in Detail
Classification (Immune-mediated / Non-infectious):
| Anterior | Posterior |
|---|---|
| Non-necrotizing: Diffuse, Nodular | Less common |
| Necrotizing with inflammation: Vaso-occlusive, Granulomatous, Surgically induced | |
| Scleromalacia perforans (necrotizing without inflammation) |
Scleromalacia perforans — occurs in long-standing RA; painless progressive scleral necrosis; no active inflammation; treatment is largely unsatisfactory.
Necrotizing scleritis is the most dangerous form — severe pain, bilateral in 60%, can destroy the eye without systemic immunotherapy.
The Phenylephrine Blanching Test (Khurana's Key Differentiator)
| Test | Conjunctivitis | Episcleritis | Scleritis |
|---|---|---|---|
| 2.5% phenylephrine | Blanches (constricts conjunctival + superficial episcleral) | Blanches | No blanching of deep plexus |
| 10% phenylephrine | Blanches all superficial vessels | Blanches | No blanching |
This is the bedside test taught by Khurana: in scleritis the deep plexus is involved and does not blanch with phenylephrine, confirming the deeper pathology.
Quick Memory Aid
Conjunctivitis → Clear discharge, Conjunctival layer, Comfort mostly intact
Episcleritis → Episcleral layer, no discharge, Easily blanches, Excellent prognosis
Scleritis → Severe pain, Systemic disease, Scleral layer, Sight-threatening
— Kanski's Clinical Ophthalmology, 10th ed. (Ch. 9: Episclera and Sclera); Rosen's Emergency Medicine
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