Anatomy Of Cornea😊

Layers Of Cornea

• Epithelium and Descemet → Regenerate

• Endothelium → most metabolically active

1. Epithelium:

• Non-keratinized stratified squamous epithelium.

• Layers:
• Superficial:
• Squamous, has microvilli for tear film adhesion.
• Basal:
• Columnar, involved in mitosis and regeneration.

2. Bowman’s layer:

• False basement membrane (PAS -ve).

• Acellular.

• Does not regenerate.

• Heals by scar formation.

• Can lead to corneal opacity and vision loss (LOV).

• Breaking bow - cant fix it back, need to apply glue (scar)

Corneal Opacities:

• LMN () - PID (Pupil, Iris, depth in stroma)

3. Stroma:

• Composed of collagen (most common Type 1) and GAGs (most common keratan sulphate).

• Thickest.

4. Dua’s layer:

• Strongest corneal layer.

5. Descemet’s Membrane (DM):

• Capable of regeneration.

• SChwalbes line: 
• Peripheral termination of DM.

• Copper deposition in Wilsons

6. Endothelium:

• Most metabolically active.

• Maintains corneal transparency.

• Derived from Neural Crest Cells

Counted using specular microscopy.

Nerve Supply (Sensory)

• Path: 
• TON
• Trigeminal (CN V) → Ophthalmic → Nasociliary branch to cornea.

Test for Corneal Sensations

• Method: Touch cornea with a cotton wisp.

• Reflex Pathway: CN V (Afferent) → Brain → CN VII (Efferent) → Blink.

• Abnormalities: No blinking → Corneal anaesthesia.

General Properties of Cornea

• Corneal shape: Convex (Converging).

• Corneal power: +43D to +44D.

• Corneal colour: Transparent (appears black).

• Curvature is proportional to Power.

Special Investigations for the Cornea

1. Pachymetry:
• Measures corneal thickness (CT).
• Normal CT: Approximately 540 microns / 0.54 mm.
• Mnemonic: Corneal thick packing

2. Keratometry:



• Measures corneal curvature.
• Detects astigmatism (vertical ≠ horizontal curvature).
• Performed using a Keratometer.
• Correct positioning of keratometric mires is crucial.

3. Topography:



• Examines corneal surface.
• Uses a Placido disc.
• Topography of a place

4. Staining:

Dye Type	Stains
Fluorescein	• Areas of broken epithelium (ulcer base) • Orange dye, viewed under Cobalt blue filter  ↳ green fluorescence Other Uses (GST) • Goldmann’s applanation tonometry • Seidel’s test (perforation) • Tear film break up test (dry eyes) • Gold (Goldmann) Flooril (Flurescence) veenu Break up ayi sed (Seidel’s test)aayi (Tea film break up)
Rose Bengal	• Areas of necrotic tissue  (ulcer margins) • Appears red red bengal Rose margin (ulcer margin) pettannu vaadum (necrotic)
Lissamine green	• Both cornea and conjunctiva • Non-toxic, does not destroy normal tissue • Primarily used for dry eyes Eg: • Vitamin A deficiency, Bitot spot, Conjunctival Xerosis • Lisa is mine (Lissamine), she is not toxic, but she is always dry (dry eyes)

Order of staining

• Fluorescein -> Lissamine green -> Rose Bengal

Siedel’s test

• Detect Perforation with aqueous humor leak

Chemical Injury

Roper–Hall System

• Alkali burns
• Twice as common as acid burns

• Depth of injury
• Alkalis penetrate deeper than acids
• Acids coagulate surface proteins
• Coagulation forms a protective barrier

• Common alkalis involved
• Ammonia
• Sodium hydroxide
• Lime

Corneal Ulcer

Definition:

• Loss of epithelium + necrosis of underlying tissue.

• Loss of epithelium without necrosis = abrasion

PATHOGENESIS

Stage 1 - Initial Stage

• Saucer shaped ulcer with overhanging margins

Stage 2 - Progressive Stage

• Infiltration by PMNs

• Hypopyon
• Mobile: Liquid like pus
• Sterile

• Keratouveitis

Stage 3 - Regressive Stage

• Smooth floor and edges of ulcer

• Increased vascularization

• Decreased inflammatory response

Stage 4 - Scar/Cicatrization

• Permanent vision loss

Bacterial Corneal Ulcer

Causes:

• Pseudomonas:
• Most common cause of corneal ulcer in contact lens users.
• Lens users in Ophthal
• Acanthameba
• Contact lens misuse
• Dirty contact lens
• Pseudomonas
• M/c/c of corneal ulcer in contact lens users
• Giant Papillary conjunctivitis

Management:

• Mnemonic: 5S
• Scrape base of ulcer using a blunt edge of 15 no. blade.
• Gram staining & culture.
• Start fortified antibiotics
• Fortified cephazolin (5%)
• Fortified tobramycin (1.3%)
• Fortified vancomycin (5%)
• Supportive therapy:
• Atropine
• Mydriasis
• Cycloplegia → relax ciliary muscles → relieves pain
• (Pain is due to contraction of ciliary muscle due to toxin released by bacteria)
• Avoid steroids
• Due to epithelial thinning

Organisms that can penetrate intact cornea:

• Mnemonic: She (Shigella) Nicely (Neisseria) Penetrated Cornea (Corynebact) and Lens (Listeria) → Blood came (H. aegypti)
• Haemophilus aegyptius
• Listeria
• Corynebacterium diptheriae
• Neisseria gonorrhoeae
• Neisseria meningitidis
• Shigella
• NO PSEUDOMONAS

Fungal Corneal Ulcer

• Most common cause: 
• Aspergillus (Filamentous, septate).

• History: Trauma with vegetative material.

Symptoms:

• Mild pain and redness.

Signs (>> Symptoms)

• Dry ulcer.

• Feathery margins.

• Satellite lesions.

• Wessley immune ring (Antigen-Antibody reaction).

• Hypopyon:
• Immobile and unsterile

• Mnemonic:
• homeless immobile (hypopyon immobile) person → wearing dress with fungus () and waste (wesley) → Want to go to satellite () with a feather ()
• Full of Naatam (Natamycin)

Treatment:

• Aspergillus/Fusarium:
• DOC: 5% Natamycin eye drops

• Yeast/Candida:
• DOC: Amphotericin B

• Systemic only in deep fungal keratitis

• Rest of the management is similar to bacterial corneal ulcers.

Complications

• IOP↑↑↑ → Corneal bulging + Corneal thinning → Iris incarceration → Anterior staphyolma → Corneal perforation → IOP↓↓ →→ Iris prolapse →→ Iris plug →→ Psuedocornea → Endophthalmitis → Panophthalmitis

1. Ectatic Cicatrix

• Corneal thinning

• Corneal bulging due to increased IOP
• Can be temporary or permanent

2. Anterior Staphyloma

• Occurs when corneal ulcer takes more time to heal despite treatment

• Corneal bulging (due to thinning) + incarceration of iris

• Often has a lobulated appearance + Bluish pigmentation

3. Descemetocele

• Herniation of Descemet's membrane

• Occurs through a corneal ulcer

4. Perforation of Cornea

• Aqueous leak → Decreased IOP

• Iris prolapse

• Pseudo-cornea:
• Corneal surface formed by plugging of perforation by iris tissue

5. Endophthalmitis/Panophthalmitis

• Endophthalmitis → Panophthalmitis

Herpetic Keratitis

• Treatment:
• 3% Acyclovir eye ointment (not drops)
• Steroids are contraindicated.
• Eye drops 1st → Ointment 15 mins later.
• If ointment is applied first:
• It creates a barrier.
• Prevents absorption of the eye drop.

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NOTE

Similar terms	Seen in
Dendritic ulcer	HSV 1 Corneal ulcer
Pseudodendrites	Acanthameba
Pseudodendritic ulcer	Varicella Zoster

Other Lesions due to Herpes:

• Necrotising stromal keratitis.

• Disciform keratitis/endothelitis.

Acanthamoeba Keratitis

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NOTE

Similar terms	Seen in
Dendritic ulcer	HSV 1 Corneal ulcer
Pseudodendrites	Acanthameba
Pseudodendritic ulcer	Varicella Zoster

• Cause:
• Contact lens users exposed to dirty water
• (e.g., swimming, cleaning lens with tap water).

• Symptoms:
• Severe pain due to nerve inflammation (Radial keratoneuritis).

• Culture:
• Non-nutrient agar enriched with E.coli.

Herpes Zoster Ophthalmicus:

• If in trigeminal root ganglion

• Hutchinson's Sign: 
• Vesicles along ala of nose
• Means nasociliary nerve involved 
• (branch of ophthalmic division of trigeminal nerve)
• Patient will have ophthalmic manifestations
• ophthalmology referral needed

Treatment of Herpes Zoster:

• Most painful, so highest dose of antivirals

Antiviral	Dosage	Duration	Total/day
Acyclovir	800 mg x five times a day	7 to 10 days	4g
Valacyclovir	1g x three times a day	7 to 10 days	3g

• Need painkillers, B12, etc.

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NOTE

Similar terms	Seen in
Dendritic ulcer	HSV 1 Corneal ulcer
Pseudodendrites	Acanthameba
Pseudodendritic ulcer	Varicella Zoster

Hutchinson's

• H → Herpes Zoster Ophthalmicus

• U → subUngual Melanoma (superficial spreading melanoma)
• Hutchinson sign

• T → Triad → congenital syphillis
• Peg shaped teeth
• Interstitial Keratitis (IK + SNHL)
• SNHL

• CH → Chauffeur's Fracture/Backfire Fracture
• Intra articular #

• Son → looking older → Hutchison Gilford
• LMN A gene defect (laminopathy).
• Progeria (onset: Child)

• PUPIL → Hutchinson Pupil
• Herniation of uncus (medial temporal lobe) → compresses ipsilateral CN III → same side pupillary dilatation.
• Kernohan’s notch phenomenon:
• False localizing sign
• Ipsilateral pupil dilatation
• Ipsilateral UMN palsy

Corneal Dystrophies

• General Features:
• Primary Bilateral, non-inflammatory opacifying disorder.
• Autosomal dominant inheritance.



• Leash on Fragile fabry (XLR)

• AR → Gay → he was congenitally gay → do posteriorly (Conegnital posterior endothelial dystrophy)

Lisch epithelial dystrophy

• Leish vachitt Adi (AD)

Feature	Classic View	Latest Update (IC3D 3rd Ed, 2024)
Inheritance	X-Linked Dominant	Autosomal Dominant
Chromosome	Xp22.3	Chromosome 19
Gene	ㅤ	MCOLN1

Types

• Kamal → Rest → Leg →

• Epithelial (CML)
• Tholikattiyulla
• Like (Lisch) Common (Cogan m/c) man with Meesa ()

• Bowman (RST)
• Buckle (Ries buckler) Fish (Fishnet) with a bow
• put in Thee (Thiel)

• Stroma (LG)
• Middle of burger
• Lettuce (Lattice) & Granules (Granular)

• Endothelium
• Posteriorly
• Fuck Congenitally Posteriorly

Fuchs Terms	Notes
Fuchs heterochromia iridocyclitis	Chronic AU ⇒ • U/L Diffuse Iris atrophy + Heterochromia + Posterior SCC • Painless, No redness, No posterior synechiae Positive Amsler's Sign: ◦ Bleeding into Anterior chamber on paracentesis ◦ Without trauma to Iris/Angle ◦ D/t abnormal fragile Iris Stellate Keratin Precipitates ↳ Herpetic uveitis ↳ Toxoplasmosis ↳ Fuchs Heterochromia Iridocyclitis • Young stella → Fucked () by Toxic () Herpes () Guy
Dalens Fuchs	• Seen in Sympathetic ophthalmitis ↳ (granulomatous panuveitis) • Dalen Fucked Granny () sympathetically ()
Foster Fuchs	• In Pathological Myopia • Bleeding at macula • Fucking in Foster () home ↳ Blind child (Pathological myopia) ↳ Bled (Bleeding at macula)
Fuchs Endothelial dystrophy	• Cornea guttata: • Wart-like excrescences on posterior cornea • Fuck her Guts→ endothelial Stages • Stage 1: Central corneal guttata that spreads peripherally • Stage 2: Corneal oedema - beaten metal-like appearance • Stage 3: Bullous keratopathy • Stage 4: Subepithelial scarring and superficial vascularization

 

Stellate terms	Seen in
Stellate cells	• Cirrhosis • NAFLD • Chronic pancreatitis • Young stella → alcoholic → liver and pancreas
Stellate Keratin Precipitates	• Herpetic uveitis • Toxoplasmosis • Fuchs Heterochromia Iridocyclitis • Young stella → Fucked () by Toxic () Herpes () Guy
Stellate Granuloma	• Cat Scratch Disease • LGV • Leprosy • Syphillis • Stella granny → has a Cat, Lgtv, has leprosy and syphillis
Stellate scar	• Kidney → Oncocytoma, Chromophobe RCC • Liver → Focal Nodular Hyperplasia, Fibrolamellar Carcinoma • Pancreas → Serous Cystadenocarcinoma • Breast → Radial Scar: Premalignant

Keratoconus

• Definition:
• Cone-shaped cornea.

• Mnemonic: Munsoon (Munsun) valley (vogt striae) resort in ooty (Rizuutti) → avide Flush (Fleishner) illa, oil illa (oil droplet) and no scissors (scissoring)

Signs:

• Munson’s sign:



• V-shaped lower lid.
• Mnemonic: Munros → Munnottu

• Irregular myopic astigmatism
• Recurrent regular change in prescription

• Rizzuti’s sign:



• Light from one side refracts to form an arrowhead shape facing the opposite side.
• Rizutty → Resortil torch adichu nadakam

• Vogt’s striae:

Striae	ㅤ	ㅤ
Haab’s striae	• Horizontal breaks in Cornea	• Congenital glaucoma
Vogt’s striae	• Vertical stretching • In Slit lamp • Vogt → Valich stretch cheyth • Striae → Stretch → Slit lamp	• Keratoconus

• Fleischer’s ring:



• Due to iron deposition.
• In the basal epithelial layer of the cornea

• Oil droplet reflex:
• Seen on ophthalmoscopy.

• ScissoRing reflex:
• Seen on Retinoscopy.

Investigation:

• Topography (IOC).

Treatment:

• INTACS’s surgery:



• Intracorneal stromal ring segments.
• Ring stretches the cornea
• Effective in early to moderate cases by flattening the cornea.

• Rigid contact lens.

Keratoplasty:

• Corneal transplantation (Cadaveric donor).

C3R Corneal collagen cross-linking

• With riboflavin & UVA radiation.

• Stabilizing keratoconus progression

• improving contact lens tolerance

• Note: 

Rings	Disease	Layer of Cornea
Kayser Fleischer ring	Wilson’s disease	• Copper in Descemet’s membrane
Fleischer's ring	Keratoconus	• Fe Deposition Basal epithelial layer
Pseudofleischers ring	Hypermetropia	ㅤ

Term	FB
Chalcosis	Copper FB
Siderosis	Iron FB

• Hudson nte stallil () Iron bulb ()

• Stock () of teri ()

Band shaped Keratopathy:

• Band shaped Ca2+ deposition in Bowman’s layer.

• Mnemonic: Calcium → Bowman → Band (Bow is a band)

• Treatment is Chelation with EDTA.

Interstitial Keratitis

• Definition: Inflammation only of corneal stroma.

• Causes:
• Congenital syphilis
• Cogan syndrome
• Interstitial keratitis + SNHL
• Mnemonic: Co gone EE → Eye, ENT
• Tuberculosis
• Herpes Simplex Virus (HSV)

Keratoplasty

• Also known as corneal transplantation.

• McCarey Kauffman medium → storage

• Taken within 6 hours from cadaver

Types of Keratoplasty

• Penetrating Keratoplasty
• Full thickness

• Lamellar Keratoplasty
• Partial thickness
• Types:
• DSEK (Descemet's stripping endothelial keratoplasty)
• Mnemonic: Sex → Posterior
• DALK (Deep anterior lamellar keratoplasty)
• DALK → Anterior

Indications

• Corneal ulcer

• Bullous keratopathy

• Keratoconus

Comparison of Keratoplasty Types

Keratoplasty Procedure

• Host cornea cut using a trephine (Diameter: 7.5mm)

• Implant the graft cornea (Diameter: 0.25mm larger than host opening)

• Nylon sutures
• Also for
• Microsurgeries like Cataract

Graft Rejection

• Endothelial rejection
• Most common (m/c) type of rejection.
• Forms Khoda-daust line (Diagnostic feature).
• Kayes dots
• Keratic Precipitates

• Krishna Priya
• Khatta dost ()
• Corneal Graft () Kayyil (Kayes) thann
• Reject () ayipoi
• Should have put in Coffee (Kauffman)

Storage Media for Corneal Transplantation

• Kaufman → Coffee → Cornea

Sclera

Episcleritis vs. Scleritis

• Note:
• Nodular episcleritis and longstanding scleritis
• can show bluish discoloration.

Scleromalacia Perforans

• Description:
• Anterior necrotising scleritis without inflammation.

• Presentation:
• No redness/pain,
• progressive atrophy → leading to scleral perforation.

• Most common in:
• Women with rheumatoid arthritis.

• If no h/o RA → Staphyloma