A peripheral infiltrate on a Friday afternoon
Ms. R, 24, has worn monthly soft spherical lenses for six years, typically 12–14 hours a day, and admits to napping in them two or three times a week. She presents on a Friday at 4:30 pm with a red, watering right eye, mild photophobia and a foreign-body sensation that began on Wednesday. Entering acuity is 6/9 OD (habitual 6/6) and 6/6 OS. Slit-lamp examination shows a 1.5 mm round focal infiltrate in the mid-peripheral cornea at 4 o'clock, a 1.2 mm overlying epithelial defect, mild circumlimbal injection, no cells or flare, and no discharge. She is flying to a wedding in four days, has no family doctor, and asks whether she can 'just switch to the left lens and use some drops until Monday'.
1. What features of this presentation push you toward microbial keratitis rather than a sterile contact-lens-related infiltrate, and what is your immediate management plan? Justify your choices rather than listing signs.
Read the worked answer
No single sign is decisive - the pattern is what matters.
Features that shift me toward microbial keratitis:
- An overlying epithelial defect (here 1.2 mm) of a size comparable to the infiltrate, which suggests tissue breakdown rather than simple deposition.
- Symptomatic photophobia and a lesion of 1.5 mm; most sterile infiltrates are smaller and less symptomatic.
- Overnight and nap wear, the strongest modifiable risk factor for keratitis.
- Onset and progression over 48 hours without lens removal.
Features that would lower my suspicion: a lesion under 1 mm, entirely peripheral, asymptomatic, with an intact epithelium, fading within 24 hours of lens removal.
Ms. R sits on the wrong side of that line. At first presentation you cannot reliably separate the two, so the safe default for a symptomatic, sizeable lesion with an epithelial defect is to treat as presumed microbial keratitis.
Immediate plan: remove the lens and retain it with the case; do not patch; no steroids; start a fluoroquinolone hourly while awake; telephone the on-call ophthalmologist for same-day or next-morning review rather than letting her wait until Monday; give written after-hours red flags and a contact number; document findings, advice and the referral.
2. She repeats that she cannot attend a wedding in spectacles and asks you to 'just give her a short course of drops' so she can keep wearing lenses. How do you handle this conversation, and what exactly do you arrange before she leaves?
Read the worked answer
Anchor the conversation in safety, then solve the practical problem.
What I would say: 'The safest assumption is that this is an infection. An infection in the cornea can scar and permanently reduce sight within a day or two. Not wearing lenses this week is not a preference - it is the single thing most likely to make this worse, so I can't agree to it.'
Then be useful rather than merely refusing:
- Offer a temporary spectacle prescription today, dispensed or trial-framed, so she has functioning vision for the trip.
- Give an explicit stop and restart rule: no lenses until the lesion has resolved and the epithelium is intact, then a staged return with a review before normal wear resumes.
- Write down red flags - increasing pain, discharge, halos, any drop in vision - and tell her not to fly before being seen.
- Use the moment to link napping and extended wear to this event; that is the behaviour most worth changing.
- Record that lenses were stopped, that spectacles were offered, and her response.
If she still declines examination, document that refusal and the risks explained. Do not let the appointment end without a scheduled review.
3. Thirty-six hours later she telephones: the eye feels much better, so she wore her lens to the wedding. What is your response, and what does this change about your documentation and plan?
Read the worked answer
Establish the clinical facts first, then address the behaviour.
Ask how long the lens was worn, whether vision has changed, whether pain or discharge has returned, and bring her in the same day. A presumed microbial keratitis followed by lens wear needs re-examination, not telephone reassurance.
Be direct without being punitive. Most non-adherence goes unreported precisely because patients expect a lecture; if she feels judged she will simply stop telling you things. Something like: 'I understand why you did it, and I need you to know how serious this was - this is the scenario in which people lose vision. The plan hasn't changed, but I need you to be straight with me about lens wear so I can judge the risk accurately.'
Documentation: record her account verbatim, that the advice was repeated verbatim, the re-examination findings, and that risks were re-explained - notes that would stand up if she later claimed she was never warned.
Plan: bring the review forward, extend the no-lens period, and escalate to ophthalmology the same day if the infiltrate has enlarged or now encroaches on the visual axis. Consider a written lens-wear agreement.