Corneal Ulcer (Infectious Keratitis)

Definition and Pathogenesis

Etiology / Causative Organisms

• Pseudomonas aeruginosa accounts for >60% of contact lens-related keratitis - aggressive and potentially destructive.
• S. aureus produces a focal, well-defined white or yellow-white infiltrate.
• Streptococcal infections tend to be aggressive.
• Fungi must be considered after trauma with vegetable matter (e.g., tree branch) or in immunosuppressed patients.

Risk Factors

• Contact lens wear - the most important risk factor, especially extended-wear and soft lenses; risk increases dramatically with overnight wear and poor lens hygiene
• Trauma (including LASIK refractive surgery)
• Exposure keratitis / incomplete eyelid closure (Bell's palsy)
• Prior ocular surgery
• Topical or systemic corticosteroids / immunosuppressants
• Diabetes mellitus
• Vitamin A deficiency
• Local or systemic immunosuppression

Clinical tip: Bacterial corneal ulceration should be excluded in any contact lens wearer who presents with painful red eye and blurred vision. - Kanski's 10e

Clinical Features

Symptoms

• Unilateral eye pain (moderate to severe)
• Photophobia
• Blurred / decreased vision (especially if ulcer is central)
• Mucopurulent or purulent discharge
• Foreign body sensation
• Red eye; acute contact lens intolerance

Signs (slit-lamp examination)

• Epithelial defect (stains with fluorescein)
• Circumcorneal (ciliary) injection
• Stromal edema, Descemet membrane folds
• Anterior chamber reaction (flare + cells) - hypopyon in moderate-severe cases
• Miotic pupil from ciliary spasm (associated iritis)
• Mucopurulent discharge; eyelid and conjunctival edema
• Posterior synechiae, raised IOP in severe cases
• Descemetocele formation and corneal perforation in very severe cases (especially Pseudomonas)
• Scleritis with perilimbal infection
• Endophthalmitis is rare without perforation

Differential Diagnosis

Investigations

Corneal Scraping and Culture

• Scrape the center and edges of the ulcer under slit-lamp
• Specimens inoculated directly onto culture media at the bedside (C-streaks)
• Scraping may be delayed up to 12 hours if antibiotics have already been started

• Gram stain and KOH preparation for rapid presumptive identification
• PCR/nanopore sequencing for exact species ID and antibiotic resistance profiling
• Culture contact lens cases and solution bottles as well (patient must NOT clean case first)
• Conjunctival swabs may supplement corneal scraping, especially in severe cases

Treatment

General Principles

• Treat empirically while awaiting culture results
• Corneal infections are assumed bacterial until proven otherwise
• Contact lens wear must be discontinued immediately
• Do NOT patch the eye (especially in contact lens wearers - rapid infection spread risk)
• Emergent ophthalmology consultation for any significant ulcer

Antibiotic Selection by Risk Level (Wills Eye Manual protocol)

• Fluoroquinolone drops (moxifloxacin, gatifloxacin, besifloxacin, levofloxacin) q1-2h while awake
• OR polymyxin B/trimethoprim q1-2h while awake

• Fluoroquinolone q1h around the clock ± polymyxin B/trimethoprim q1h
• Consider loading dose: q5min x 5 doses, then q30min until midnight, then q1h

• Fortified antibiotics (from formulating pharmacy):
  • Fortified tobramycin or gentamicin (15 mg/mL) q1h, alternating with
  • Fortified cefazolin (50 mg/mL) or vancomycin (25 mg/mL) q1h
  • Net: one drop every 30 minutes around the clock
• If Pseudomonas suspected (contact lens wearer): fortified tobramycin q30min + fortified ceftazidime q1h + fluoroquinolone q1h
• Vancomycin reserved for resistant organisms or MRSA risk

Adjunctive / Special Circumstances

• Cycloplegic (cyclopentolate 1-2%, atropine 1%) for iritis-related spasm and pain
• Oral fluoroquinolones (ciprofloxacin 500 mg bid or moxifloxacin 400 mg daily) for scleral extension or impending perforation
• Neisseria infections: ceftriaxone 1 g IV q12-24h if corneal involvement (systemic spread risk)
• Haemophilus infections: oral amoxicillin/clavulanate (systemic complications possible)
• Atypical mycobacteria: prolonged topical moxifloxacin/gatifloxacin ± fortified amikacin (15 mg/mL) ± oral clarithromycin 500 mg bid

When to Admit

• Sight-threatening infection or impending perforation
• Difficulty self-administering drops at required frequency
• High noncompliance risk
• Suspected topical anesthetic abuse
• IV antibiotics needed (Neisseria with corneal involvement)
• Corneal perforation or scleral extension

Follow-Up

1. Pain level
2. Epithelial defect size (may initially increase after scraping)
3. Infiltrate size and depth
4. Anterior chamber reaction
5. IOP (can rise; treat if elevated)

Complications

• Corneal scarring and permanent visual loss
• Descemetocele (Descemet membrane bulging through thinned stroma)
• Corneal perforation (especially Pseudomonas)
• Hypopyon
• Endophthalmitis (rare without perforation)
• Elevated IOP / secondary glaucoma
• Posterior synechiae
• Persistent epithelial defects (may require amniotic membrane grafting - recent systematic review, PMID 39257085)

Summary Table: Organism-Specific Clues

NDPS Act - Short Notes (CFM / Forensic Medicine, MBBS 3rd Year)

Full Form & Introduction

• Passed by the Parliament of India in 1985
• Extended to the whole of India
• Administered by the Ministry of Finance (Department of Revenue)

Acts Repealed by NDPS Act 1985

1. The Opium Act, 1857
2. The Opium Act, 1878
3. The Dangerous Drugs Act, 1930

Objectives of the NDPS Act

1. Consolidate and amend laws relating to narcotic drugs
2. Strengthen existing controls over drugs of abuse
3. Enhance penalties, especially for illegal trading offences
4. Exercise effective control over psychotropic substances
5. Implement international conventions (UN Single Convention on Narcotic Drugs, 1961; 1971 Convention on Psychotropic Substances; 1988 UN Convention Against Illicit Traffic)

Important Definitions Under NDPS Act

Narcotic Drug

Manufactured Drug

1. All coca derivatives, medicinal cannabis, opium derivatives and poppy straw concentrate
2. Any other narcotic substance declared as such by the Central Government

Psychotropic Substance

• The schedule lists 77 psychotropic substances
• Examples: LSD, amphetamine, tranquilizers, barbiturates, benzodiazepines, methaqualone, ketamine, psilocybin, phencyclidine, mescaline

Addict

Small Quantity

Commercial Quantity

Quantity Schedule and Penalties

Punishment Grid

Offences Under NDPS Act (Chapter IV)

• Cultivation of poppy, cannabis, coca plants without licence
• Production, manufacture, possession, sale, purchase, transport, import, export of narcotic drugs/psychotropic substances
• Embezzlement of opium by a cultivator
• Illegal import/export/transshipment of narcotic drugs
• External dealings in narcotic drugs in contravention of Section 12
• Allowing premises to be used for commission of an offence (S.26)

Note: Ganja possession for personal use may not attract commercial quantity penalties but is still punishable.

Prevention of Illicit Traffic in Narcotic Drugs and Psychotropic Substances Act, 1988 (PITNDPS Act)

• A companion Act to NDPS 1985
• If a person produces, possesses, transports, imports, exports, sells, purchases, or uses any narcotic drug or psychotropic substance (except ganja) - punishable with imprisonment
• Death sentence for repeat offenders
• Provides for preventive detention of persons engaged in illicit drug trafficking

Licensing Requirement

• Poppy plant
• Cannabis plant
• Coca plant

Related Companion Legislation (Important for MCQs)

Relevant IPC / BNS Sections on Poisoning

Key legal principle: The law does not require an exact definition of "poison" - administration of any substance with intent to cause injury/death is sufficient for conviction. Intent is the key element.

High-Yield Points for Exams (MCQ + Short Notes)

1. Year of NDPS Act - 1985 ✔
2. Three Acts repealed - Opium 1857, Opium 1878, Dangerous Drugs 1930 ✔
3. Narcotic drug definition mnemonic - CCOP → Coca leaf, Cannabis, Opium, Poppy straw + manufactured drugs ✔
4. 77 psychotropic substances in the schedule ✔
5. Heroin small quantity - 5 g; commercial - 250 g ✔
6. Cocaine small quantity - 2 g; commercial - 100 g ✔
7. Ganja commercial quantity - 20 kg (highest threshold) ✔
8. Commercial quantity punishment - minimum 10 years, maximum 20 years RI + ₹1-2 lakh fine ✔
9. Death sentence - for repeat commercial-quantity offenders ✔
10. Burden of proof - on the accused to prove personal consumption for small quantity possession ✔
11. Cultivation of poppy/cannabis/coca requires licence ✔
12. PITNDPS Act 1988 = companion Act for preventive detention and trafficking ✔