Bilateral gritty red eyes case: differential diagnosis
Summarise the history and physical for a 19-year-old with two days of bilateral gritty, red, itchy, tearing eyes as if presenting to a preceptor, give at least three differentials with pathophysiology, argue each for and against from the findings, rank them, and justify any testing with evidence-based medicine.
Editorial process
Last reviewed · August 14, 2026
The nasal exam decides an eye complaint
Read the whole record before you touch the eyes, because the findings that settle this case are in the nose and the medication history. He has known seasonal allergic rhinitis controlled on loratadine and fluticasone, he is not taking either at the moment, he has moved from Phoenix to central Illinois and is meeting a new pollen load, and his turbinates are pale and boggy with clear drainage. Against that, the eye findings are bilateral, itchy, tearing and gritty, with diffuse conjunctival redness, white sclera, no crusting and no mucoid or purulent discharge, and visual acuity is uncorrected 20/20. Itching plus bilateral involvement plus clear discharge in a patient with untreated atopy is allergic conjunctivitis; the absence of purulence argues against bacterial, and the absence of preauricular adenopathy, a recent upper respiratory infection or a watery unilateral onset weakens viral. Nothing in this record points away from atopy.
The assignment is graded on the argument, not on the answer. Each differential needs a brief statement of pathophysiology — for allergic conjunctivitis, IgE-mediated mast cell degranulation releasing histamine on the conjunctival surface — and then a paragraph that uses the pertinent positives and negatives from this case to argue for and against it. Rank the list explicitly from most to least likely rather than leaving the order implicit. The testing section is where an evidence-based argument is demanded in both directions: if you order nothing, you must justify that with evidence, and the honest answer here is usually that the diagnosis is clinical and that conjunctival cultures, fluorescein staining or allergy testing would not change management in a well-appearing patient with normal acuity. Fluorescein is worth discussing and excluding, since foreign-body sensation with a contact lens history would change that. Keep the opening summary concise and in shorthand, because the brief penalises redundancy directly.
Likely learning objectives
Inferred from the brief — check these against your own rubric.
- 01Summarise a history and physical concisely in the register used to present to a preceptor.
- 02Generate a differential for bilateral red eye and state the pathophysiology of each option.
- 03Use pertinent positives and negatives to argue for and against each differential.
- 04Rank a differential and defend the ordering.
- 05Justify ordering or withholding a test with evidence-based reasoning.
Read the full question
Review every instruction before using the planning guidance that follows.
Turn the brief into deliverables
- 01A brief, shorthand H&P summary using only the pertinent facts.
- 02A minimum of three differential diagnoses, each with a short pathophysiology statement.
- 03An analysis using case findings to argue for and against each diagnosis.
- 04The differential ranked from most to least likely.
- 05Any additional tests or procedures, each supported by an evidence-based argument.
- 06An evidence-based justification if no testing is indicated.
Present, differentiate, argue, rank, then justify testing
Concise H&P presentation
Give the preceptor the pertinent story and exam in shorthand.
Differential one: allergic conjunctivitis
State IgE-mediated pathophysiology and the findings that support it.
Differential two: viral conjunctivitis
Describe adenoviral spread and argue it from and against this case.
Differential three: bacterial conjunctivitis
Describe the purulent mechanism and say why this case argues against it.
Ranking the differential
Order the list and state the discriminating findings behind the order.
Testing decision with EBM support
Name any test considered and justify ordering or withholding it.
Sources for each conjunctivitis and for the testing argument
Recommended databases
- StatPearls via NCBI Bookshelf
- American Academy of Ophthalmology preferred practice patterns
- PubMed
- Your programme's clinical decision support tool
Search sequence
- 1.Read a current review of the red eye and note the discriminating features between the three conjunctivitis types.
- 2.Confirm the pathophysiology of type I hypersensitivity at the conjunctival surface.
- 3.Check what evidence supports or refutes conjunctival culture in an uncomplicated presentation.
- 4.Note the red flags that would mandate fluorescein staining or referral.
- 5.Draft the H&P summary and cut it until nothing irrelevant remains.
Reference shortlist
These are authoritative starting points, not a ready-made bibliography. A qualified reviewer must confirm that each source fits the assignment and supports the claim beside which it is cited.
Nothing here is cleared for citation until you have read it.
- 01
Allergic Conjunctivitis
StatPearls, NCBI Bookshelf · 2023
Pathophysiology and diagnostic features of the most likely diagnosis in this case.
- 02
Viral Conjunctivitis
StatPearls, NCBI Bookshelf · 2023
The features that would have been present if this were adenoviral, which is how you argue against it.
- 03
Bacterial Conjunctivitis
StatPearls, NCBI Bookshelf · 2023
Discharge character and culture indications, needed for the testing argument.
- 04
Allergic Rhinitis
StatPearls, NCBI Bookshelf · 2023
Explains the pale boggy turbinates and connects the nasal findings to the ocular complaint.
- 05
Type I Hypersensitivity Reaction
StatPearls, NCBI Bookshelf · 2023
The mechanism statement the brief asks for alongside each differential.
Review before submission
Common mistakes
- Repeating the whole case back instead of summarising it, which the brief explicitly penalises.
- Listing differentials without any pathophysiology.
- Arguing only for each diagnosis and never against it.
- Missing that the patient has stopped his antihistamine and nasal steroid.
- Ignoring the pale boggy turbinates, which are the strongest single finding in the record.
- Saying no testing is needed without the evidence-based argument the brief requires for that choice.
Submission checklist
- The summary uses approved abbreviations and omits irrelevant negatives.
- At least three differentials appear, each with pathophysiology.
- Every differential has both supporting and opposing findings named.
- The ranking is explicit and justified.
- The testing decision is supported by evidence either way.
- The medication history and the nasal findings are used, not just the eye exam.
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Written by
Aaron Bishop
MA, Education
assignment interpretation and research-methods coaching across disciplines
Aaron leads the EssayCrackers editorial desk. He works on how assignment briefs are read — what a rubric is actually asking for, and where students most often answer a different question than the one set.
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PhD, Rhetoric & Composition
Argumentation and thesis development
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