Superficial Punctate Keratitis

Superficial punctate keratitis (SPK), also termed superficial punctate keratopathy or punctate epithelial erosions (PEE), is a non-specific clinical sign characterised by discrete, focal areas of corneal epithelial cell disruption or death. It is not a single disease entity but rather a common pattern of corneal response to a wide variety of insults — infectious, inflammatory, toxic, mechanical, and degenerative.

• Prevalence: One of the most frequently encountered anterior segment findings in clinical optometry practice. Highly prevalent in patients with dry eye disease, blepharitis, and contact lens wear.
• Thygeson's SPK: A distinct idiopathic entity first described by Thygeson in 1950, characterised by coarse, raised, stellate, grayish-white intraepithelial lesions with a chronic relapsing course, minimal conjunctival involvement, and absence of stromal disease.
• Importance: SPK serves as a sensitive marker of corneal epithelial health. Its pattern, distribution, and severity guide etiological diagnosis and inform management decisions.
• Demographics: Affects all ages. Thygeson's SPK typically presents in young to middle-aged adults and follows a recurrent course over years to decades.

Infectious Causes

• Viral: Adenoviral keratoconjunctivitis (epidemic keratoconjunctivitis, pharyngoconjunctival fever); Herpes simplex virus (HSV) epithelial keratitis; Varicella-zoster virus (VZV); Molluscum contagiosum (toxic effect on cornea from lid lesions)
• Bacterial: Staphylococcal blepharitis-associated toxic keratopathy; Chlamydial inclusion conjunctivitis (superior SPK)
• Parasitic: Early Acanthamoeba keratitis may present with pseudo-dendrites and SPK before ring infiltrate forms

Non-Infectious Causes

• Dry eye disease: Aqueous-deficient or evaporative dry eye — most common cause of inferior/diffuse SPK
• Toxic/Iatrogenic: Preservative toxicity (benzalkonium chloride in chronic topical drops); topical anaesthetic abuse; antiviral toxicity; aminoglycoside toxicity
• UV/Photokeratitis: Excessive UV-B exposure (welding arc eye, snow blindness, tanning beds)
• Contact lens-related: Lens deposits, hypoxia, mechanical trauma, solution toxicity, giant papillary conjunctivitis-associated
• Exposure keratopathy: Nocturnal lagophthalmos, seventh nerve palsy, proptosis, anaesthetic cornea
• Neurotrophic keratopathy: Reduced corneal sensation with epithelial breakdown — insidious onset
• Superior limbic keratoconjunctivitis (SLK): Superior tarsal and limbal inflammation; superior SPK
• Vernal/Atopic keratoconjunctivitis: Superior punctate epithelial erosions from giant papillae
• Rosacea: Inferior SPK from meibomian gland dysfunction and telangiectasia

Idiopathic

• Thygeson's superficial punctate keratitis: Idiopathic, chronic, relapsing-remitting condition with coarse intraepithelial lesions; no clear infectious cause despite extensive investigation; possible viral trigger postulated

The pathogenesis varies by etiology but converges on a final common pathway of epithelial cell death and surface disruption:

1. Initiating insult: Infectious pathogens (cytopathic viral replication, bacterial exotoxins), physical agents (UV radiation, desiccation, mechanical trauma), toxic agents (preservatives, topical medications), or immune-mediated injury trigger corneal epithelial cell damage.
2. Epithelial cell disruption: Intercellular tight junctions are broken down. Superficial epithelial cells undergo necrosis or apoptosis, creating discrete focal defects.
3. Focal epithelial loss: Devitalised or absent epithelial cells expose the underlying basement membrane or Bowman's layer. These areas stain with fluorescein (disrupted intercellular junctions) and rose bengal/lissamine green (devitalised cells).
4. Inflammatory cascade: Epithelial injury releases pro-inflammatory cytokines (IL-1α, TNF-α), recruits neutrophils and macrophages to the ocular surface, and activates conjunctival goblet cell dysfunction — perpetuating the damage cycle.
5. Thygeson's mechanism: Lesions are intraepithelial (cells are dysplastic rather than lost), possibly representing an immune-mediated or virally triggered epithelial dysmaturation. Stroma and endothelium are uninvolved, and cultures are negative. T-cell mediated hypersensitivity has been postulated.
6. Resolution and recurrence: When the inciting cause is removed, epithelial regeneration occurs rapidly (corneal epithelium turns over every 7–14 days). Without cause removal, chronic exposure leads to repeated cycles of injury and repair, potentially resulting in subepithelial scarring.

By Distribution Pattern (Clinical Utility)

By Etiology

• Type 1 — Infectious SPK: Viral (adenovirus, HSV, VZV), bacterial-associated (staphylococcal toxin), parasitic
• Type 2 — Non-infectious inflammatory SPK: Dry eye, blepharitis, allergic, SLK, vernal KKC
• Type 3 — Toxic/Iatrogenic SPK: Preservative-induced, topical drug toxicity, UV photokeratitis
• Type 4 — Mechanical/Structural SPK: Contact lens trauma, trichiasis, entropion, floppy eyelid, exposure
• Type 5 — Idiopathic SPK: Thygeson's SPK (distinct clinical entity)

Ocular and Adnexal Factors

• Contact lens wear (extended wear, poor hygiene, silicone hydrogel hypoxia, lens deposits)
• Anterior blepharitis and meibomian gland dysfunction
• Dry eye disease (aqueous-deficient or evaporative)
• Lid margin disease (entropion, ectropion, lagophthalmos, trichiasis)
• Reduced corneal sensation (neurotrophic risk)
• Previous herpetic or adenoviral infection

Pharmacological and Environmental Factors

• Chronic use of preserved topical medications (glaucoma drops, antihistamines, antivirals)
• Topical anaesthetic misuse or abuse
• UV exposure without protective eyewear (outdoor workers, welders, skiers)
• Low humidity environments (air-conditioned offices, aircraft cabins)
• Chemical splash or occupational exposure
• Systemic medications: isotretinoin, chemotherapy agents, antihistamines (anticholinergic dry eye)

Systemic Conditions

• Rosacea (sebaceous gland and meibomian gland involvement)
• Sjögren's syndrome, rheumatoid arthritis (aqueous-deficient dry eye)
• Thyroid ophthalmopathy (exposure from proptosis or lid retraction)
• Immunosuppression (increased viral susceptibility)
• Vitamin A deficiency (developing countries; diffuse epitheliopathy)

Slit Lamp Findings

• Epithelial defects: Fine, discrete, punctate epithelial erosions or raised intraepithelial opacities visible on diffuse illumination; number ranges from a few to hundreds depending on severity and cause
• Fluorescein staining: Punctate green staining under cobalt blue illumination; pattern and distribution diagnostic; mild staining may be missed without NaFl instillation
• Rose bengal / lissamine green staining: Stains devitalised epithelial cells; useful for identifying non-wettable or dead cells not apparent with fluorescein alone
• Thygeson's lesion morphology: Coarse, raised, grayish-white, stellate or granular intraepithelial opacities; appear elevated on retroillumination; may have faint surrounding haze; no staining of stroma
• Anterior chamber: Usually quiet; mild flare possible in severe cases or concurrent iritis (HSV)

Conjunctival and Adnexal Signs

• Conjunctival injection (variable — minimal in Thygeson's; prominent in adenoviral, toxic)
• Follicular or papillary conjunctival reaction depending on etiology
• Lid margin changes: telangiectasia, collarettes, crusting (blepharitis); meibomian gland inspissation (MGD)
• Pre-auricular lymphadenopathy in adenoviral or chlamydial infection
• Subepithelial infiltrates (SEI) — may develop 2–3 weeks after adenoviral keratoconjunctivitis
• Reduced TBUT (<10 seconds) and Schirmer's test results in dry eye-related SPK

• Foreign body sensation: Persistent gritty or scratchy feeling — hallmark complaint; correlates with epithelial defect density
• Photophobia: Often prominent; can be disabling in Thygeson's and UV photokeratitis; may be disproportionate to clinical signs in Thygeson's
• Epiphora (excessive tearing): Reflex lacrimation from corneal irritation
• Blurred or fluctuating vision: Due to epithelial irregularity and tear film instability over defects; clears momentarily with blinking
• Burning or stinging: Particularly with toxic/preservative-related causes; worsens with preserved drop instillation
• Contact lens intolerance: Early lens removal, reduced comfortable wearing time, awareness during wear
• Discharge: Mild mucoid discharge; mucopurulent if secondary bacterial infection
• Ocular redness: Variable; may be minimal in Thygeson's despite significant symptoms

• Persistent epithelial defect: Failure of epithelial healing if the underlying cause is not addressed; risk of corneal melt in neurotrophic cases
• Subepithelial scarring / haze: Chronic or recurrent SPK may produce anterior stromal fibrosis; reduces visual acuity, particularly if central; risk increased with prolonged topical steroid use in Thygeson's
• Recurrent corneal erosion syndrome: Epithelial basement membrane changes from chronic insult; episodes of acute pain and epithelial sloughing, particularly on waking
• Secondary bacterial keratitis: Breach in epithelial barrier permits bacterial entry; risk greatest in contact lens wearers with SPK
• Corneal neovascularisation: Peripheral or central stromal vessels in chronic or hypoxic cases
• Subepithelial infiltrates (post-adenoviral): Immune-mediated opacities persisting weeks to months after adenoviral EKC; may reduce visual acuity and cause photophobia
• Reduced visual acuity: From epithelial irregularity, scarring, or subepithelial infiltrates; rarely visually devastating with SPK alone

• Rosacea: Inferior SPK secondary to meibomian gland dysfunction and tear film lipid deficiency. Facial rosacea, rhinophyma, and telangiectasia are associated. Ocular rosacea may precede skin disease.
• Sjögren's syndrome / Rheumatoid arthritis: Aqueous-deficient dry eye causes interpalpebral or diffuse SPK. Systemic disease evaluation indicated in bilateral SPK with significant dry eye symptoms.
• Stevens-Johnson syndrome / Toxic epidermal necrolysis: Acute and chronic ocular manifestations include diffuse SPK, conjunctival scarring, trichiasis, and limbal stem cell deficiency. SPK may be a herald of early mucous membrane involvement.
• Thyroid ophthalmopathy: Proptosis and lid retraction cause exposure keratopathy with inferior interpalpebral SPK. Severity correlates with degree of proptosis and incomplete lid closure.
• Vitamin A deficiency: Severe deficiency causes diffuse SPK, Bitot's spots, and xerophthalmia — primarily a concern in nutritionally vulnerable populations. Corneal melting may follow.
• Thygeson's SPK: Possible association with HLA-DR3 has been postulated. Some authors hypothesise a viral or immune-mediated trigger. No confirmed systemic associations, but patients warrant monitoring for atopic conditions.
• Systemic viral infections: Adenoviral EKC may occur in epidemic clusters (healthcare settings, swimming pools). Systemic symptoms include pharyngitis, fever, pre-auricular lymphadenopathy.

Clinical History

• Onset, duration, and course (acute vs. chronic/relapsing)
• Contact lens wear history (type, solution, wearing schedule)
• All current topical medications (especially preserved drops)
• UV exposure history (occupation, recreation, recent welding)
• Systemic conditions and systemic medications
• Recent upper respiratory tract infection (adenoviral)
• Travel history, swimming pool or spa exposure

Slit Lamp Examination

• Systematic examination of lids, lid margins, tarsal conjunctiva, bulbar conjunctiva, limbus, and corneal epithelium
• Fluorescein instillation with cobalt blue filter: note number, distribution, and morphology of staining dots
• Rose bengal or lissamine green staining to identify devitalised cells
• Retroillumination for Thygeson's raised intraepithelial lesions
• Evaluate for corneal vascularisation, stromal infiltrates, or thinning
• Examine anterior chamber for cells and flare

Tear Film Assessment

• Tear break-up time (TBUT): <10 seconds is abnormal; <5 seconds suggests significant evaporative disease
• Schirmer's test I (without anaesthetic): <10 mm/5 min indicates aqueous deficiency
• Meibomian gland evaluation: expression, dropout assessment (meibography if available)

Ancillary Tests (Selected Cases)

• Corneal cultures/scrapings: if infectious keratitis suspected (bacterial, fungal, Acanthamoeba)
• Corneal PCR: for HSV, VZV, adenovirus in atypical or recurrent cases
• Adenoviral point-of-care immunoassay (AdenoPlus): rapid diagnosis of adenoviral keratoconjunctivitis
• Corneal sensitivity testing (Cochet-Bonnet aesthesiometer): reduced in neurotrophic keratopathy, herpetic disease
• Blood tests: ANA, rheumatoid factor, SSA/SSB antibodies if Sjögren's or autoimmune suspected; vitamin A levels if deficiency suspected

General Principles

• Identify and treat the underlying cause — the cornerstone of management
• Switch all current topical medications to preservative-free formulations
• Discontinue contact lens wear until resolution
• Prescribe UV-protective eyewear for prevention and during healing

Lubrication and Ocular Surface Support

• Preservative-free artificial tears (sodium hyaluronate, carboxymethylcellulose) QID to hourly depending on severity
• Lipid-containing artificial tears or eyelid warming for evaporative dry eye / blepharitis-related SPK
• Lubricating ointment at night for exposure or severe dry eye
• Bandage contact lens (silicone hydrogel, high Dk) for pain relief in severe SPK; monitor closely for infection
• Moisture chamber spectacles or swimming goggles for severe exposure or low humidity environments

Cause-Specific Treatment

• Blepharitis / MGD: Warm compresses, lid hygiene (lid scrubs), oral doxycycline 20–100 mg BD (rosacea-associated); azithromycin pulse therapy; intense pulsed light (IPL) therapy
• Dry eye disease: Preservative-free lubricants; topical cyclosporine 0.05% (Restasis) or 0.1% (Ikervis) BD; lifitegrast 5% (Xiidra) BD; punctal occlusion; dietary omega-3 supplementation
• Adenoviral keratoconjunctivitis: Supportive (lubricants, cold compresses); strict hygiene counselling; no proven antiviral; topical steroids for subepithelial infiltrates affecting vision (with caution); povidone-iodine 0.4% drops (off-label antiviral use)
• Herpes simplex epithelial keratitis: Topical ganciclovir gel 0.15% 5× daily or acyclovir ointment 3% 5× daily; systemic acyclovir or valaciclovir for recurrent or severe disease; avoid topical steroids without antiviral cover
• UV photokeratitis: Preservative-free lubricants; cycloplegic if photophobia severe; oral analgesics; bandage contact lens for comfort; self-limiting — resolves in 24–72 hours
• Toxic / preservative keratopathy: Cessation of all preserved topical agents; substitution with preservative-free formulations; consider switching to laser or surgical glaucoma treatment to reduce drop burden

Thygeson's SPK — Specific Management

• Topical corticosteroids (fluorometholone 0.1% or prednisolone 0.5%): effective symptom relief but do not alter disease course; risk of steroid-induced cataract, glaucoma, and rebound with chronic use; use sparingly
• Topical cyclosporine 0.05–0.1% (preservative-free): preferred long-term therapy; reduces relapse frequency; slower onset than steroids but steroid-sparing effect
• Bandage contact lens (silicone hydrogel): provides symptomatic relief; allows cessation of steroids in some patients
• Lubricants (preservative-free): adjunctive comfort; do not treat underlying lesions
• Tacrolimus 0.03% eye drops (off-label, limited evidence): emerging option

• Cause-dependent SPK: Generally excellent prognosis when the underlying cause is identified and corrected. Most cases resolve completely within days to weeks once the offending agent is removed or the infection is treated.
• UV photokeratitis: Self-limiting; resolves within 24–72 hours with supportive care. No lasting visual morbidity in typical cases.
• Adenoviral keratoconjunctivitis: Acute SPK resolves, but subepithelial infiltrates may persist for months to years; topical steroids may shorten infiltrate duration but risk rebound. Long-term visual acuity generally preserved.
• Dry eye-related SPK: Chronic condition requiring ongoing management. Prognosis for epithelial health is good with sustained treatment, but underlying dry eye disease typically does not resolve.
• Thygeson's SPK: Benign overall visual prognosis; vision rarely drops below 6/9. However, condition follows a prolonged relapsing-remitting course over years to decades before eventual spontaneous resolution in most patients. Subepithelial scarring is a risk with prolonged steroid use. Quality of life impact can be significant due to photophobia and discomfort.
• Herpetic SPK: Good prognosis with antiviral treatment; risk of recurrence if prophylactic antivirals discontinued. Avoid topical steroids without antiviral cover to prevent stromal keratitis.

• Herpes simplex epithelial keratitis (dendritic ulcer): Dendritic or geographic ulcer with terminal bulbs on fluorescein; reduced corneal sensation; unilateral; history of prior episodes. Distinguish from SPK pseudo-dendrites of Acanthamoeba or VZV.
• Adenoviral keratoconjunctivitis (EKC): Diffuse SPK followed by subepithelial infiltrates; significant follicular conjunctivitis; membranes/pseudomembranes on tarsal conjunctiva; pre-auricular node; epidemic exposure history.
• Recurrent corneal erosion syndrome: Acute episodes of severe pain on waking; epithelial map-dot-fingerprint changes (epithelial basement membrane dystrophy); history of prior corneal abrasion.
• Acanthamoeba keratitis (early): Initially SPK-like with pseudo-dendrites; severe disproportionate pain; ring infiltrate develops later; contact lens use in contaminated water; corneal PCR/culture confirms.
• Medicamentosa / toxic keratopathy: Diffuse SPK from preserved drops; whorled or diffuse pattern; clear history of chronic preserved topical drug use; resolves with cessation of agent.
• Superior limbic keratoconjunctivitis (SLK): Superior SPK with rose bengal staining of superior bulbar conjunctiva and limbus; superior tarsal papillary reaction; associated with thyroid disease; filamentary keratitis may co-exist.
• Neurotrophic keratopathy: Reduced or absent corneal sensation (key differentiator); persistent epithelial defect may develop; oval or round non-healing epithelial defect with rolled edges; associated with HSV, VZV, acoustic neuroma, diabetes, surgery.
• Vernal / atopic keratoconjunctivitis: Superior SPK from giant papillae; shield ulcer may develop; significant itching; young males; giant cobblestone papillae on superior tarsal conjunctiva; limbal Horner-Trantas dots.
• Dry eye disease: Inferior or interpalpebral SPK; reduced TBUT; variable Schirmer's; characteristic symptoms of fluctuating vision, burning, and foreign body sensation; responds to lubrication.

• SPK is a sign, not a diagnosis — always search for and document the underlying cause.
• The distribution pattern of staining is the single most useful clue to etiology: inferior = blepharitis/dry eye; superior = contact lens/SLK/VKC; central = Thygeson's/adenoviral; diffuse = toxic.
• Always ask about all topical drops the patient uses — preserved medications are a commonly missed and correctable cause of chronic SPK.
• Thygeson's lesions are raised and intraepithelial on retroillumination, not simply epithelial defects — this is the key morphological difference from other causes.
• In Thygeson's, photophobia is often disproportionate to the slit lamp appearance; this mismatch should raise suspicion for the diagnosis.
• Check corneal sensation in any case of unexplained, persistent, or non-healing SPK — neurotrophic keratopathy may be silent and progressive.
• UV photokeratitis has a characteristic latent period of 6–12 hours between exposure and onset of symptoms — always ask about UV exposure 12–24 hours before presentation.
• Adenoviral keratoconjunctivitis is highly contagious — counsel patients on hand hygiene, avoid shared towels, and consider time off work if employed in healthcare or childcare settings.
• Never prescribe topical steroids for suspected HSV keratitis without concurrent antiviral cover — stromal melting may result.
• When treating Thygeson's with steroids, use the minimum effective frequency and always counsel about the risk of steroid-induced glaucoma and cataract with prolonged use; cyclosporine is preferred for long-term management.

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