This patient-education article is written by the cornea service at Suraj Eye Institute, Nagpur.

What is Specular Microscopy?

Specular microscopy is a non-contact, non-invasive photograph of the corneal endothelium — the single layer of pump-cells on the inside of the cornea that keep the tissue clear by actively pumping fluid out of it. Endothelial cells do not regenerate in human eyes. They are lost slowly through life and faster after intraocular surgery, trauma, contact lens wear or in diseases such as Fuchs endothelial dystrophy. Knowing how many endothelial cells the cornea still has — and how healthy they look — is essential before planning any intraocular operation.

Specular Microscopy — Image and Report

Specular Microscopy — What the Report Shows

SPECULAR IMAGE (normal)

QUANTITATIVE REPORT

ECD Endothelial Cell Density 2780 cells/mm²

HEX % % hexagonal cells (pleomorphism) 68 %

CV Coefficient of variation (polymegathism) 0.32

Normal young adult: 2500–3000 cells/mm² (REVIEW) Age-related: −0.6 % per year (REVIEW) ⚑ < 1000 cells/mm² → high risk of decompensation

Each hexagonal cell ≈ 20 µm wide (viewing about 0.1 mm² of cornea)

Figure 1. A typical specular microscopy report. The instrument captures a magnified image of the endothelial mosaic (left). Each cell is approximately 20 µm wide; the image typically shows about 0.1 mm² of cornea. Software then counts the cells and reports endothelial cell density (ECD, in cells/mm²), the proportion of regular hexagonal cells (HEX %) and the coefficient of variation in cell size (CV). Cell density below approximately 1000 cells/mm² substantially raises the risk of corneal decompensation after intraocular surgery; in practice the warning signs are corneal thickening (oedema), other clinical changes in the cornea and a fall in vision.

What Specular Microscopy Tells Us

The report has three key numbers:

  • Endothelial cell density (ECD) — the number of cells per square millimetre. A healthy young adult has 2500–3000 cells/mm². ECD falls slowly with age (approximately 0.6 % per year) and faster after trauma, surgery or in disease.
  • Hexagonality (HEX %) — the percentage of cells that retain the normal hexagonal shape. Stress (age, surgery, disease) makes cells lose their hexagonal shape and become irregular — pleomorphism.
  • Coefficient of variation (CV) — the variation in cell size. Stressed endothelium shows increasingly variable cell sizes — polymegathism.

What Specular Microscopy Is Used For

  • Pre-cataract assessment in eyes with Fuchs dystrophy, advanced age, prior intraocular surgery or dense cataracts — to plan endothelial protection
  • Diagnosis and staging of Fuchs dystrophy
  • Pre-operative assessment in pseudophakic bullous keratopathy to confirm low cell counts before DSAEK / DMEK
  • Post-keratoplasty follow-up to detect early endothelial rejection or attrition
  • Long-term contact lens wearers with morphological changes

What to Expect

The scan is non-contact, painless and takes a few seconds per eye. No drops are needed. The patient sits at the instrument, fixates on a target, and the image is captured automatically. A printed report is generated at the same visit.

✔ Endothelial Assessment at Suraj Eye Institute

Specular microscopy is currently arranged through partner laboratories for our patients with Fuchs dystrophy, before complex cataract surgery in high-risk eyes, and during follow-up after endothelial keratoplasty. The report — endothelial cell density, percentage of hexagonal cells and coefficient of variation — guides decisions on cataract surgery technique, timing of endothelial transplant and post-graft follow-up at SEI.

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Frequently Asked Questions

Why do I need this if my eyes feel fine?
The corneal endothelium has reserve — it can lose half its cells and still keep the cornea clear. Symptoms appear only when the reserve is exhausted. Specular microscopy detects the silent loss before it becomes symptomatic, which matters most when you are about to have intraocular surgery.

Is the test the same as the Anterion?
No. The Anterion maps the curvature and thickness of the cornea (its shape); specular microscopy images the endothelial cell mosaic on the inside of the cornea (its inner lining). They answer different questions and are often done at the same visit.

Can I have cataract surgery if my cell count is low?
Usually yes, but with extra care. We use viscoelastic protection of the endothelium throughout surgery, gentle phacoemulsification settings, and sometimes plan a combined cataract / endothelial transplant procedure if the count is very low or there is overt corneal oedema.

My report says polymegathism — is that serious?
Polymegathism is variation in cell size and shows the endothelium has been stressed. It is common with age and after long-term contact lens wear and is usually monitored rather than treated, unless the cell density is also low or there are signs of corneal swelling.

How often should the test be repeated?
For monitoring Fuchs dystrophy, typically every 12 months; more often if there are symptoms or planned surgery. After endothelial keratoplasty, the scan is typically repeated at 6 months and 12 months, then annually.

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