Specular Microscopy Reference Card: Cell Density, CV and Hexagonality
Last updated: October 2026
Specular microscopy tells you how much endothelial reserve a cornea has. Check it before cataract surgery in Fuchs dystrophy, after trauma or previous surgery, before phakic IOLs, and when grading donor corneas.
The three numbers
| Parameter | Normal | Abnormal or worrying | Meaning |
|---|---|---|---|
| Cell density (ECD) | About 2,000–3,000 cells/mm² in adults (higher in children) | Under 1,500: limited reserve. Under 1,000: high risk of decompensation after intraocular surgery. Under about 500: corneal oedema. | How many pump cells are left |
| Coefficient of variation (CV, polymegethism) | Under 0.30 (30%) | Over 0.40 | Variation in cell size: a stressed endothelium |
| Hexagonality (pleomorphism) | Over 60% hexagonal cells | Under 50% | Loss of regular shape: an unstable endothelium |
Cell density falls with age, by roughly 0.5–0.6% a year in adults. Cataract surgery typically costs about 5–10% of cells, more with hard nuclei, long phaco time or shallow chambers.
Typical density by age (approximate)
| Age | Approximate ECD (cells/mm²) |
|---|---|
| Infancy | 4,000–5,000 or more |
| 20–30 years | About 3,000–3,500 |
| 40–60 years | About 2,600–3,000 |
| Over 70 years | About 2,300–2,600 |
Population values vary; Indian and East Asian series report similar or slightly higher densities. Use the fellow eye and previous counts for comparison.
What to do with the result
| Situation | Action |
|---|---|
| Cataract with ECD over about 1,500 and normal CV and hexagonality | Routine surgery with good endothelial protection (dispersive viscoelastic, low phaco energy) |
| Cataract with ECD 1,000–1,500, or guttae | Counsel about slower recovery and possible oedema. Use soft-shell technique and chop to reduce energy; consider DMEK later if needed. |
| Fuchs dystrophy with morning blur, CCT over about 620–640 µm, or epithelial bullae | Consider combined or staged cataract surgery and endothelial keratoplasty (DMEK or DSAEK) |
| Phakic IOL (anterior chamber or iris-fixated) | Check ECD before and yearly after. Explant if it falls below the safe limit for age or drops fast. |
| Donor cornea for keratoplasty | Most eye banks require about 2,000 cells/mm² or more for penetrating keratoplasty, and often more (about 2,300–2,500) for DMEK |
Reading the image: the automatic count is only as good as the image. Check that at least about 50–100 cells were counted, that the analysed area is in focus, and that guttae (dark spots) have not been counted as cells. In advanced guttae the device may give a falsely high or "unmeasurable" count; confocal microscopy or clinical judgement then takes over.
Red flags: ECD under 1,000 cells/mm², a fall of more than about 10% in a year, CV over 0.40 with hexagonality under 50%, or guttae with central corneal thickening. Plan endothelial protection or keratoplasty rather than routine surgery.
Related: Fuchs endothelial dystrophy, keratoplasty types, the cataract pre-op risk checklist and normal values.
Key sources
- Bourne WM, Nelson LR, Hodge DO. Central corneal endothelial cell changes over a ten-year period. Invest Ophthalmol Vis Sci 1997;38:779–82
- McCarey BE, Edelhauser HF, Lynn MJ. Review of corneal endothelial specular microscopy for FDA clinical trials of refractive procedures, surgical devices and new intraocular drugs and solutions. Cornea 2008;27:1–16
- Eye Bank Association of India and Eye Bank Association of America medical standards (current editions)
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