Slit Lamp Evaluation With & Without Contact Lenses
Key Takeaways
- Without-lens evaluation proceeds tissue by tissue: lids, conjunctiva (with upper lid eversion to find GPC/papillae), cornea, and tear film; fluorescein staining reveals pattern-specific causes (SPK, 3 & 9 o'clock, foreign body track).
- RGP fit patterns are interpreted with fluorescein and cobalt blue: apical touch is dark central (flat fit), apical clearance is bright central pool (steep fit), alignment is a uniform thin layer, and edge lift shows as a peripheral band.
- Soft lenses do not produce a usable fluorescein fit pattern; fluorescein is used to detect corneal staining under or around the lens after the lens is removed, because soft materials absorb fluorescein.
- Soft lens fit is judged by coverage, movement (~0.5-1.5 mm/blink), centration, lid interaction, and edge behavior in white light, not by a fluorescein pattern.
- Lens surface evaluation covers deposits (protein, lipid, inorganic, microbial), wettability, coating, and physical defects such as scratches, nicks, and cracks.
Slit Lamp Evaluation With & Without Contact Lenses
A CLRE slit-lamp evaluation happens in two phases: the without-lens ocular health exam and the with-lens fit and surface exam. Both use the same instrument, but each has its own sequence, staining strategy, and pattern vocabulary. Domain III treats pattern recognition as testable material, so the candidate must connect a clinical picture to a structural cause, not just name it.
Phase 1: Without Contact Lenses
Before any lens is placed, the slit lamp must clear the eye for contact lens wear. Work tissue by tissue:
| Tissue | What to check | Technique |
|---|---|---|
| Lids & lashes | Blepharitis, lid wiper, Meibomian gland orifice plugging, lash misdirection | Diffuse beam, low magnification; express Meibomian glands |
| Conjunctiva (bulbar) | Injection, chemosis, pinguecula, pterygium | Diffuse, broad beam |
| Conjunctiva (tarsal) | Papillae, follicles, giant papillary conjunctivitis (GPC) | Evert the upper lid — large papillae hide here |
| Cornea | Staining, edema, infiltrates, vascularization (pannus) | Direct focal optical section + cobalt blue after fluorescein |
| Tear film | Meniscus height, debris, lipid layer, TBUT | Tangential / broad beam; fluorescein for TBUT |
Staining Patterns and Meaning
Fluorescein staining indicates compromised epithelium. Recognizing the pattern's location and shape points to a cause:
- Punctate staining (SPK) — fine, dotted, diffuse; often dry eye, solution toxicity, or mild mechanical trauma.
- 3 & 9 o'clock staining — staining at the 3 and 9 o'clock positions of the cornea; classic for RGP wearers due to poor tear exchange and lid interaction at those positions; often improved with edge design changes.
- Foreign body staining — linear or arcuate tracks from a foreign body under the lens or lid; tracks follow the path of the offending particle.
- Inferior arcuate staining — often soft lens-related, due to lens dehydration or interaction with the inferior lid margin.
- Dimple veiling — punctate staining from mechanical compression (often from overnight wear or a steep lens).
- Central corneal staining — possible tight lens syndrome, solution toxicity, or epithelial hypoxia.
Phase 2: With Contact Lenses
Once ocular health is confirmed, the fit and surface of the lens are evaluated on the eye.
RGP Lenses with Fluorescein
Fluorescein is essential for evaluating RGP fit patterns. Instill a small amount of fluorescein and observe with cobalt blue:
| Pattern | Fluorescein appearance | Interpretation |
|---|---|---|
| Apical touch | Dark central area (no fluorescein between lens and cornea) | Flat fit; cornea bears on lens back surface |
| Apical clearance | Bright central pool of fluorescein | Steep fit; excessive tear lens centrally |
| Alignment | Thin, uniform fluorescein layer across the central cornea | Ideal fit — base curve matches corneal curvature |
| Midperipheral bearing | Dark zone in the midperiphery with central clearance | Peripheral curve too steep or excessive central clearance |
| Excessive edge lift | Wide bright band at the lens edge | Edge stands off too far — risk of air bubbles and decentration |
| Insufficient edge lift | No fluorescein band at the edge | Edge too tight — reduced tear exchange, 3 & 9 staining risk |
| Air bubbles | Dark round voids, often peripherally | Excessive edge lift or trapped bubbles under a steep lens |
Soft Lens Evaluation
Soft lenses do not require fluorescein for fit pattern — the lens drapes over the cornea and a fluorescein pattern is not visible. However, fluorescein is useful to:
- Detect corneal staining under or around a soft lens (remove the lens to evaluate properly, since the lens may absorb fluorescein).
- Confirm lens fit indirectly — excessive movement, edge lift, or conjunctival interaction may show as staining patterns after lens removal.
Soft lens fit evaluation on the eye uses white light and observation of:
- Coverage — lens should cover the entire cornea, ideally 0.5-1.0 mm beyond the limbus.
- Movement — ~0.5-1.5 mm with the blink; too little = tight; too much = loose.
- Centration — ideally centered; temporal or nasal decentration suggests base curve or diameter mismatch.
- Lid interaction — lens should not ride under the upper lid excessively (causes discomfort and upper lid staining).
- Edge — should not compress conjunctiva (causes vascular blanching) or stand off (causes awareness and debris entry).
Lens Surface Evaluation
The lens surface is examined at low and medium magnification with diffuse illumination and direct focal beam:
- Deposits — protein (white/opaque film), lipid (oily, glistening), inorganic (calcium, colored), and microbial (colonies, fungal filaments).
- Wettability — poor wetting shows as dry spots on the lens surface; tear film breaks over the lens quickly.
- Coating — visible film indicates cleaning or replacement interval problem.
- Scratches, nicks, cracks — visible defects indicating handling damage or material fatigue.
For RGP surfaces, fogging or poor wetting often responds to in-office cleaning (surfactant, enzymatic, or solvent); scratches require polishing or replacement.
Common Traps
- Forgetting to evert the upper lid — GPC's large papillae are not visible without eversion.
- Evaluating a soft lens FIT with fluorescein — soft lens draping does not produce a usable fluorescein pattern.
- Misreading apical touch vs clearance — touch is dark (lens touches cornea), clearance is bright (pool of tears).
- Assessing soft lens staining with the lens on — fluorescein absorbs into soft materials, so the lens must be removed before evaluating corneal staining.
- Missing 3 & 9 o'clock staining — it is almost pathognomonic for RGP-related tear exchange issues.
Sequence Checklist
A complete CL slit-lamp evaluation, in order:
- Without lens: lids, then conjunctiva (evert upper lid), then cornea, then tear film.
- Without lens: fluorescein for TBUT and baseline staining.
- Insert lens: evaluate surface (deposits, wetting).
- With lens: movement, centration, coverage (soft) or fluorescein pattern (RGP).
- After lens removal: corneal staining pattern, conjunctival staining, lid wiper.
A patient returns for a soft lens follow-up with mild discomfort. The slit lamp reveals large papillae under the upper lid and mild punctate staining centrally on the cornea. What is the most likely diagnosis and the required exam technique?
During an RGP follow-up, the practitioner observes a dark central zone with no fluorescein between the lens and cornea, surrounded by a bright midperipheral ring of fluorescein. What is the most likely interpretation and remedy?