Why the endothelium matters
The cornea is kept transparent by the endothelium constantly pumping fluid out of it. Cell density is about 3,500 per square millimeter at birth and falls slowly through life to around 2,500 in later adulthood, with the remaining cells enlarging to fill the gaps. Disease, surgery and injury accelerate the loss. Below roughly 500 cells per square millimeter, the pump fails, the cornea swells and vision clouds. Because the cells cannot be replaced, every decision that stresses the endothelium is made with the count in mind.
How the count is done
A specular microscope reflects light off the endothelium and photographs the mosaic of cells at high magnification, without touching the eye, in a few seconds. Software counts the cells in the image and measures the variation in cell size and the proportion of hexagonal cells, both of which fall as the layer becomes stressed. In Fuchs dystrophy the image also shows guttae, the bumps that mark the disease.
When it is ordered
- Fuchs endothelial dystrophy: diagnosis, staging and timing of DMEK
- Before cataract surgery in any patient with corneal guttae, a low count or previous corneal surgery, to plan a gentle technique or combined transplantation
- Before and after EVO ICL implantation, where a healthy count is a requirement and yearly monitoring is standard
- After corneal transplantation, to monitor graft health
- Long term contact lens wearers with a hazy or swollen cornea
- After eye injury or intraocular surgery with unexpected corneal swelling
What a low count means
A low count does not mean the cornea will fail; it means it has less reserve. Cataract surgery is generally still possible, using techniques that protect the endothelium, such as laser fragmentation to reduce ultrasound, protective viscoelastics and careful fluid management, and sometimes with a DMEK transplant combined or staged. The ICL is not implanted below the manufacturer's threshold for age. A falling count over years prompts a change in management before the cornea decompensates.
Is this right for your eyes?
Nothing on this page is a diagnosis. Whether this is the right choice for you is decided by a full examination at one of our 4 offices: Pasadena, Huntington Beach, Woodland Hills and Beverly Hills.
About this content: This page was written with the assistance of AI tools and reviewed for medical accuracy by Dr. Bavand Youssefzadeh, DO. It is general information, not medical advice, and does not replace an eye examination. Individual results vary. Read our medical disclaimer.
