12-phase flow (12)

1. 1FRAME
   Frame around the ORBITAL SEPTUM: this engine owns PRESEPTAL (Chandler I — eyelid/periorbital soft tissue anterior to the septum, NO proptosis/EOM/acuity/RAPD/chemosis change, not toxic), the common (~71% vs ~28% orbital — Jackson & Baker Head Neck Surg 1987 PMID 3312114) and pediatric-predominant counterpart. The disciplined separation from orbital (postseptal) cellulitis IS the core job — any orbital sign routes OUT to ophtho.orbital-cellulitis.core.v1. Source sinusitis, sepsis, intracranial extension, and the necrotizing/facial-cellulitis look-alikes are recognised and routed OUT by engine_id, not re-authored here (Chandler 1970 PMID 5470225; Baiu & Melendez JAMA 2020 PMID 31935029).
   advance: septum-based scope confirmed; not-this-engine concerns routed by engine_id
2. 2ENTRY
   Recognise the entry: eyelid/periorbital erythema-oedema with normal acuity/motility/globe position (preseptal candidate) vs periorbital swelling WITH any orbital sign (postseptal → route out) vs skin/adnexal breach source vs sinusitis/dacryocystitis source vs the young-child / unreliable-follow-up entry. Record proptosis up front — its absence is the cardinal preseptal discriminator and proptosis is the single strongest surgical predictor (Murphy J Paediatr Child Health 2020 PMID 32987452).
   inputs: proptosis
   actions: workup.acute_red_eye
   advance: entry trigger present; proptosis status recorded
3. 3CONTEXT
   Build the preseptal-vs-postseptal pretest prior: source of infection (skin/adnexal breach tends to stay preseptal; ethmoid sinusitis / dacryocystitis carry higher cross-to-orbital risk — Jackson & Baker 1987 PMID 3312114; Shih Br J Ophthalmol 2021 PMID 34607790), age (pediatric predominance; young-child threshold), Hib/PCV immunization status (epidemiology shift — Ambati Ophthalmology 2000 PMID 10919886; Rimon 2008 PMID 18825903), fever, diabetes/immunocompromise. This phase assigns the preseptal pretest probability.
   inputs: source_of_infection, age, immunization_status_hib_pcv, temperature, immunocompromise_or_diabetes
   actions: workup.acute_red_eye
   advance: source + age + immunization + preseptal-vs-postseptal pretest prior assigned
4. 4RED_FLAGS
   The SEPTUM red-flag cluster — ANY of: proptosis, painful/restricted EOM, decreased acuity/colour vision, RAPD, or chemosis = postseptal (orbital) cellulitis → route OUT to ophtho.orbital-cellulitis.core.v1 (recognised here, NOT managed here). Black necrotic eyelid / dusky skin / crepitus / pain out of proportion → necrotizing lid emergency → surgical + route to id.necrotising-fasciitis.core.v1. Meningismus / altered mental status → intracranial extension → route to neuro.bacterial-meningitis.core.v1. qSOFA≥2 / hypotension → id.sepsis.core.v1. These are screened and routed by engine_id, not re-authored here (Chandler 1970 PMID 5470225; Murphy 2020 PMID 32987452).
   inputs: ophthalmoplegia_pain_on_eye_movement, visual_acuity_and_colour_vision, rapd_relative_afferent_pupillary_defect, chemosis, sbp
   actions: workup.acute_vision_loss, calc.qsofa
   advance: orbital / necrotizing / intracranial / sepsis red flags screened and routed by engine_id if positive
5. 5INITIAL_WORKUP
   Document the eyelid findings and explicitly record the NEGATIVE orbital exam (acuity, colour, pupils/RAPD, motility, globe position) — the disciplined preseptal "all-negative" snapshot. CBC + CRP baseline (rising CRP → post-septal risk/surgery — Murphy J Paediatr Child Health 2020 PMID 32987452); creatinine for oral dosing; blood cultures only if febrile/toxic or young child (low yield in the post-Hib era — Rimon J Pediatr Ophthalmol Strabismus 2008 PMID 18825903). Imaging is NOT routine for clearly preseptal disease (Murphy 2020 — only 30% imaged; Friedel Am J Ther 2019 PMID 28452841 — no insect-bite preseptal patient imaged).
   inputs: wbc, crp, creatinine
   actions: panel.cbc, panel.inflammation, panel.cmp
   advance: negative orbital exam documented + baseline labs sent; imaging deferred unless an indication present
6. 6BRANCHING_WORKUP
   Preseptal-vs-postseptal decision tree: clearly preseptal + well + reliable → no CT, oral-outpatient pathway (Friedel 2019 PMID 28452841). Equivocal orbital exam, sinogenic/dacryocystitis source, young child who cannot be examined, no improvement at 24-48 h, or rising CRP → contrast CT orbits + sinuses to exclude postseptal disease/subperiosteal abscess (Murphy J Paediatr Child Health 2020 PMID 32987452; Šuchaň Cesk Slov Oftalmol 2014 PMID 25640234). Identify and route the look-alikes: allergic/contact eyelid oedema (bilateral, itchy, no fever/tenderness), insect-bite reaction (punctum, itch), chalazion/hordeolum (focal lid nodule), dacryocystitis/canaliculitis (medial-canthal, expressible pus — source), herpes zoster ophthalmicus (V1 dermatomal vesicles, Hutchinson sign — route to HZO), necrotizing fasciitis of the lids (route OUT).
   inputs: contrast_ct_orbits_and_sinuses
   actions: workup.acute_red_eye, workup.cellulitis_necfasc
   advance: postseptal disease excluded or routed; preseptal confirmed or alternative diagnosis assigned + routed
7. 7DIFFERENTIAL
   Terminal differential with named pivots: preseptal cellulitis vs orbital (postseptal) cellulitis (proptosis + painful EOM + acuity/colour drop + RAPD + chemosis pivot — the septum; THE key pair) vs allergic/contact eyelid oedema (bilateral, pruritic, NON-tender, afebrile, no warmth pivot) vs insect-bite reaction (central punctum + itch + minimal systemic features pivot) vs chalazion/hordeolum (discrete focal lid nodule, minimal diffuse cellulitis pivot — may be the source) vs dacryocystitis/canaliculitis (medial-canthal swelling over the lacrimal sac, expressible mucopurulent reflux pivot — treat as source) vs herpes zoster ophthalmicus (V1-dermatomal grouped vesicles, Hutchinson sign, neuralgic pain pivot — route to HZO) vs necrotizing fasciitis of the lids (dusky/black skin, crepitus, pain out of proportion, systemic toxicity pivot — surgical emergency, route OUT)
   advance: single best diagnosis selected; orbital cellulitis and the necrotizing emergency explicitly excluded or routed
8. 8RISK_STRATIFICATION
   Stratify preseptal disposition: low-risk = older child/adult, mild, afebrile, normal WBC/CRP, skin/adnexal source, reliable follow-up → oral-outpatient. Higher-risk modifiers lowering the admission/IV/imaging threshold: young child (esp. incompletely immunized), systemic toxicity / high fever, dacryocystitis or sinogenic source, immunocompromise/diabetes, unreliable exam or follow-up, no improvement on oral therapy. Any orbital sign overrides → route to ophtho.orbital-cellulitis.core.v1 (Brugha Pediatr Emerg Care 2012 PMID 22344208; Murphy 2020 PMID 32987452).
   inputs: age, temperature, crp, wbc
   actions: calc.news2, calc.qsofa
   advance: preseptal risk tier + admission/IV/imaging modifiers assigned
9. 9TREATMENT
   Confirm-it-is-preseptal gate (negative orbital exam) → ORAL antibiotics covering streptococci + MSSA ± community MRSA: amoxicillin-clavulanate first-line (covers skin flora + sinogenic Haemophilus/anaerobes), cefuroxime or clindamycin alternatives, TMP-SMX or doxycycline if MRSA-risk (avoid doxycycline/TMP-SMX in pregnancy/young child) — typically 7-10 d with mandatory 24-48 h review (Friedel Am J Ther 2019 PMID 28452841; Shih Br J Ophthalmol 2021 PMID 34607790). IV escalation (ampicillin-sulbactam / cefazolin ± vancomycin) for the young child, systemic toxicity, dacryocystitis/sinogenic source, immunocompromise, or oral failure — ambulatory IV with daily review is a safe, cost-saving alternative to admission (Brugha Pediatr Emerg Care 2012 PMID 22344208). Treat the SOURCE in parallel: warm compresses ± incision for hordeolum/lid abscess, lacrimal-sac care/route for dacryocystitis, route the sinusitis source to ent.acute-sinusitis.core.v1. Corticosteroids are NOT added (insufficient evidence — Kornelsen Cochrane 2021 PMID 33908631). ANY orbital sign at any point → route to ophtho.orbital-cellulitis.core.v1.
   inputs: creatinine, pregnancy, source_of_infection
   advance: preseptal confirmed; oral (or ambulatory-IV/IV) agent + source control started; 24-48 h review booked; orbital route-out armed
10. 10DISPOSITION
    Low-risk preseptal (older child/adult, mild, afebrile, reliable) → discharge on oral antibiotics with a mandatory 24-48 h review and explicit return precautions (Friedel Am J Ther 2019 PMID 28452841; Brugha Pediatr Emerg Care 2012 PMID 22344208). Young child / systemic toxicity / dacryocystitis-sinogenic source / immunocompromise / unreliable follow-up → admit or ambulatory IV with daily review. ANY orbital/postseptal sign, necrotizing features, intracranial extension, or sepsis → admit + route OUT by engine_id with carryover state (Chandler 1970 PMID 5470225).
    inputs: proptosis, age, temperature, sbp
    advance: disposition documented; oral-OPD vs IV/admit decided; route-outs executed for any orbital/necrotizing/sepsis flag
11. 11MONITORING
    Re-examine for the orbital cluster (acuity, colour, pupils/RAPD, motility, proptosis, chemosis) at the 24-48 h review — the critical question is "has it crossed the septum?" Expect periorbital erythema to settle on correct oral therapy; failure to improve, new orbital sign, rising CRP, or spreading erythema at 24-48 h mandates contrast CT + escalation to ophtho.orbital-cellulitis.core.v1, NOT silent oral continuation (Murphy J Paediatr Child Health 2020 PMID 32987452 — rising CRP → post-septal/surgery; Šuchaň Cesk Slov Oftalmol 2014 PMID 25640234 — 24-48 h non-improvement → escalate).
    inputs: crp, wbc, visual_acuity_and_colour_vision
    actions: panel.inflammation
    advance: objective improvement with negative orbital re-exam by 24-48 h, OR CT + orbital-engine escalation triggered
12. 12FOLLOWUP
    Complete the oral course (typically 7-10 d guided by source and response); treat and follow the SOURCE — definitive lacrimal management for recurrent dacryocystitis (anatomic cause; route to ENT/oculoplastics), ENT source-sinus management routed to ent.acute-sinusitis.core.v1, hordeolum/blepharitis lid hygiene, conjunctivitis treatment. Counsel return precautions: any vision change, double vision, eye-movement pain, the eye pushing forward (proptosis), increasing swelling, or fever → emergency return for orbital reassessment (the preseptal→orbital progression risk — Kornelsen Cochrane 2021 PMID 33908631). Recurrent preseptal disease → reconsider an anatomic lacrimal cause.
    inputs: source_of_infection
    advance: oral course + source-directed follow-up + orbital-progression return precautions documented