Pr Eric E. GabisonOphthalmology · Cornea & refractive · Paris
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Home › Pro area › Fuchs dystrophy › Diagnosis & imaging
Course contents ▾
  1. Definition & framework
  2. Pathophysiology
  3. Genetics
  4. Diagnosis & imaging
  5. Differential diagnosis
  6. Medical & osmotic therapy
  7. DSO & ROCK inhibitors
  8. Endothelial keratoplasty
  9. Cell therapy & engineering
  10. Aggravating factors & cataract
  11. Slowing progression
  12. Decision synthesis
  13. Publications & sources
Chapter 04

Diagnosis & endothelial imaging

Diagnosis is clinical, supported by endothelial imaging and edema measurement. The history is suggestive: morning blur that improves through the day reflects overnight edema (lids closed), cleared by evaporation on eye opening. In advanced stages: halos, permanent visual loss, then the pain of ruptured epithelial bullae.

4.1 Examination & grading

At the slit lamp, guttae give a beaten-metal appearance of the posterior surface; density is graded on the Krachmer scale (grade 1: < 12 scattered central guttae → grade 5–6: confluent area > 5 mm with edema). Endothelial pigment and Descemet thickening complete the picture.

4.2 Quantitative imaging

Specular microscopy
Quantifies endothelial cell density, polymegathism (size variation) and pleomorphism (loss of hexagonality); guttae appear as dark voids — density may be underestimated with confluent guttae.
Confocal microscopy
Fine cellular analysis, useful when specular fails (edema, confluent guttae).
Pachymetry / OCT
Measure edema; CCT > 640 µm and especially early tomographic markers guide timing.
Tomographic markers (Scheimpflug/OCT)

Three signs precede clinical edema and predict decompensation (useful before cataract surgery): (1) loss of normal central thinning (loss of regular isopachs); (2) displacement of the thinnest point; (3) focal posterior surface depression. Corneal backscatter/densitometry reveals early stromal edema.

Pachymetric harmony — detecting subclinical edema (Gabison et al., AJO 2023)

Normally the cornea thickens regularly from centre to periphery: this is pachymetric harmony. Subclinical FECD edema flattens this gradient (relative central thickening). On OCT thickness mapping, the disruption is quantified by differences (Δ) and ratios (R) of thickness between periphery (5, 7, 9 mm) and centre (2 mm), per quadrant — most discriminant supra-nasally (SN) — indices that are independent of absolute CCT (removing inter-individual variability). Non-edematous vs edema (triple procedure): Δ5-2 mm SN 38 vs 17 µm; R5/2 mm SN 1.07 vs 1.03; R7/2 mm SN 1.15 vs 1.09 (P < .001). Thresholds (90% specificity): Δ5-2 mm SN < 27 µm → edema probability ×7; R5/2 mm SN < 1.045 → ×9.4; R7/2 mm SN < 1.118 → ×7.4. Use: detect preclinical edema and decide between cataract alone and a combined (triple) procedure.

Chapter 05

Differential diagnosis

Several entities share either the endothelial appearance or corneal edema and must be distinguished from FECD.

Table 2 — Differentiating FECD
EntityDistinguishing feature
Posterior polymorphous dystrophy (PPCD)Vesicular / band lesions, often asymptomatic, ZEB1; endothelium with epithelial behaviour
Congenital hereditary endothelial dystrophy (CHED)Edema from birth/childhood, SLC4A11, bilateral cloudy cornea
Iridocorneal endothelial (ICE) syndromeUnilateral, young woman, iris anomalies, synechiae, glaucoma; "metaplastic" endothelium
Pseudophakic bullous keratopathyEdema after lens surgery, without bilateral dystrophic guttae
Secondary / isolated guttataInflammatory or toxic context; guttae without progressive dystrophy
Pitfall

ICE is unilateral with iris anomalies/glaucoma — opposite to bilateral FECD. PPCD can mimic guttae but is often asymptomatic and shares ZEB1 with some FECD.