14.1 Staining Patterns: 3 & 9 O'Clock, Foreign Body, SPK, Arcuate, Smile & Dimple Veiling
Key Takeaways
- Corneal staining is fluorescein uptake under cobalt blue indicating epithelial compromise; grade severity 0 (none) to 4 (confluent) using the Efron or CCLRU scale.
- 3 & 9 o'clock staining is the classic RGP complication caused by incomplete blink, lid-lens interaction, or excessive edge lift at the horizontal meridian.
- SPK (superficial punctate keratitis) presents as diffuse fine punctate dots from dryness, solution toxicity, or overwear; punctate staining is the most common pattern seen in soft lens wearers.
- SEAL and arcuate staining at 12 o'clock signal mechanical interaction of a steep lens edge with the upper lid; smile staining curves inferiorly from a flat soft lens edge.
- Dimple veiling produces stippled staining from trapped air bubbles under an RGP; it usually resolves spontaneously but indicates a steep fit or poor tear exchange.
Staining Patterns in Contact Lens Follow-Up
Quick Answer: Staining = fluorescein uptake. Instill sodium fluorescein, evaluate under cobalt blue with a Wratten (yellow) barrier filter, and grade severity 0–4. The pattern tells you the cause: 3 & 9 o'clock points to RGP lid interaction, foreign body track is linear under the lens, SPK is diffuse punctate from dryness/toxicity, arcuate at 12 o'clock is SEAL, smile staining curves inferiorly from a flat soft lens edge, and dimple veiling is stippled air-bubble staining under an RGP.
Why Staining Matters
The corneal epithelium should be a continuous, hydrophobic barrier that resists fluorescein uptake. When epithelial intercellular junctions are disrupted — by mechanical chafing, desiccation, toxicity, or infection — fluorescein enters the defect and glows bright green under cobalt blue. Any staining in a contact lens wearer is abnormal and warrants an explanation, not just documentation.
Evaluation Technique
- Instill sodium fluorescein (strip wetted with sterile saline, touched to inferior tarsal conjunctiva — never directly to the cornea).
- Examine with the slit-lamp cobalt-blue filter and a yellow Wratten (barrier) filter over the observation pathway; the filter roughly doubles contrast.
- Grade severity using a standardized scale:
| Grade | Description |
|---|---|
| 0 | No staining |
| 1 | Trace — a few scattered punctate spots |
| 2 | Mild — localized punctate, not confluent |
| 3 | Moderate — confluent punctate or small macroerosion |
| 4 | Severe — large epithelial defect, possibly with stromal involvement |
Grade 0–2 generally allows continued wear with modifications; grade 3–4 usually requires lens discontinuation and treatment.
Common Staining Patterns
| Pattern | Location | Typical Cause | Lens / Fit Fix |
|---|---|---|---|
| 3 & 9 o'clock | Peripheral cornea at 3 and 9 (horizontal meridian) | RGP — incomplete blink, lid-lens interaction, edge lift | Larger diameter, flatter/rounded edge, better wetting, blinking exercises |
| Foreign body track | Linear streak, often under lens | Trapped debris under lens | Remove and clean lens; rule out defects |
| SPK (punctate) | Diffuse, interpalpebral or exposure zone | Dryness, solution toxicity, overwear, hypoxia | Re-wetting, preservative-free care, reduce wear time, higher Dk/t |
| Arcuate (SEAL) | Arc at 12 o'clock under upper lid | Mechanical edge interaction, high-modulus SiHy, steep fit | Lower modulus, flatter BC, thinner edge |
| Smile | Curved inferior cornea | Flat soft lens edge lifting and chafing inferiorly | Steepen BC, reduce diameter, change edge design |
| Dimple veiling | Stippled, often central, RGP | Trapped air bubbles under steep RGP, poor tear exchange | Flatten BC, increase peripheral curves, improve tear exchange |
3 & 9 O'Clock Staining (RGP)
The classic RGP complication. The peripheral cornea at 3 and 9 o'clock dries because the lid cannot rewet the cornea peripheral to the lens edge — the lid either stops at the lens edge (incomplete blink) or the edge lift prevents tear exchange. Chronic 3 & 9 staining can progress to dellen or sterile infiltrates.
Management:
- Increase lens diameter so the edge tucks under the lid.
- Modify the edge lift — round and flatten the edge so the lid can slide over it.
- Improve wetting (re-wetting drops, higher wetting-angle material).
- Teach complete blink exercises; video the patient's blink if possible.
Foreign Body Track
A linear staining track beneath the lens signals a foreign body (mascara, lint, dust) trapped under the lens and swept across the cornea with each blink. The track is typically thin, straight, and oriented with blink motion.
Management: Remove the lens, inspect and clean or replace it, irrigate the eye, and re-evaluate. Recurrent tracks suggest lens surface defect or environment (e.g., makeup particles).
SPK — Superficial Punctate Keratitis
Fine, diffuse punctate staining — the most common pattern in soft lens wearers. Causes cluster into three buckets:
- Desiccation — low tear film, incomplete blink, high-water low-Dk lens drying out.
- Toxicity — preservative (thimerosal historically; now PHMB, Dymed) or solution overload.
- Metabolic — hypoxia from overwear or low Dk/t.
Management: Switch to preservative-free care, increase Dk/t, shorten wearing time, add lubricating drops, evaluate for dry eye.
Arcuate Staining & SEAL
Superior Epithelial Arcuate Lesion (SEAL) is an arc-shaped staining at 12 o'clock under the upper lid. It is most associated with high-modulus SiHy lenses (first-generation SiHy) and a steep fit where the lens edge rubs the superior cornea under the upper lid pressure. See section 14.2 for full SEAL workup.
Smile Staining
A curved inferior staining pattern resembling a smile. It results from a flat soft lens edge that lifts away from the cornea inferiorly and chafes on downgaze or with blink. Management: steepen the base curve, reduce diameter, or select a lens with a different edge design (thinner, more lifted).
Dimple Veiling
Small, round, stippled staining under an RGP, caused by air bubbles trapped between lens and cornea. The bubbles compress the epithelium, leaving tiny dimple imprints that stain lightly when the lens is removed. The pattern usually resolves within hours without treatment, but its presence indicates a steep fit or poor tear exchange. Flatten the base curve, widen peripheral curves, and confirm tear exchange with fluorescein.
Key Takeaways
- Always grade staining 0–4 and document the pattern, location, and depth.
- 3 & 9 o'clock = RGP horizontal meridian; SEAL = 12 o'clock arcuate; smile = inferior curved.
- Foreign body track is linear — remove and clean the lens.
- SPK is diffuse punctate — solve desiccation, toxicity, hypoxia.
- Dimple veiling = trapped air under a steep RGP; flatten the fit and confirm tear exchange.
A patient returns for a 1-week RGP follow-up with grade 2 staining at 3 and 9 o'clock and a complaint of dryness. What is the MOST appropriate first lens modification?
Which staining pattern is classically associated with trapped air bubbles under an RGP and typically resolves spontaneously within hours?