Amniotic Membrane in Eye Surgery: Which Side Is Up, Dry vs Wet Membrane, Inlay, Onlay and Fixation
Last updated: November 2026
Amniotic membrane (AM) is the innermost layer of the placenta. It promotes epithelial healing, reduces inflammation and scarring, and acts as a scaffold or a biological bandage. Getting the orientation and technique right decides whether it works as a graft that becomes part of the surface or as a temporary patch.
Uses
- Persistent epithelial defects and neurotrophic ulcers.
- Acute chemical burns and Stevens-Johnson syndrome (early, to reduce scarring).
- Pterygium and conjunctival reconstruction when autograft is not possible (e.g. future glaucoma surgery, double pterygium).
- Conjunctival tumour excision, symblepharon release, fornix reconstruction.
- Bullous keratopathy (pain relief), small corneal perforations (multilayer, with glue).
Types of membrane
| Type | Storage | Preparation | Notes |
|---|---|---|---|
| Cryopreserved (wet) | −80°C in glycerol medium (eye bank or commercial) | Thaw at room temperature; rinse in BSS 2–3 times to remove glycerol | Preserves more growth factors; needs cold chain |
| Dried / lyophilised / dehydrated | Room temperature | Rehydrate with BSS on the eye or in a dish as instructed | Easy storage and transport; often sterilised by irradiation |
| Self-retaining ring device (e.g. Prokera-type) | As per product | Inserted like a large contact lens | Sutureless office use for acute burns and defects |
Which side is which
| Side | Feel and appearance | How to check |
|---|---|---|
| Epithelial / basement membrane side | Smooth, shiny, not sticky | A dry cellulose sponge does not stick |
| Stromal side | Dull, slightly sticky, may have spongy tissue | A sponge sticks and lifts small strands |
Many commercial membranes come mounted on paper or nitrocellulose with the epithelial side up (stromal side against the backing), and are often marked by a notch or an asymmetric cut. Read the product insert: conventions differ between suppliers.
Techniques
| Technique | Orientation | Purpose |
|---|---|---|
| Inlay (graft) | Epithelial side up, stroma down onto the bed, cut to the size of the defect | Becomes incorporated as a basement membrane for epithelium to grow over |
| Onlay (patch / overlay) | Larger than the defect, covering it and the surrounding area; many surgeons place it epithelial side down (stromal side up), others stromal side down | Temporary biological bandage; falls off or is removed in 1–2 weeks |
| Sandwich | Inlay plus onlay | Deep ulcers; inner layers act as graft, outer as patch |
| Multilayer | Several inlays to fill a deep defect, then a patch | Deep ulcers, descemetocele, small perforations with glue |
Fixation
- Fibrin glue: fast and comfortable; see fibrin glue.
- Sutures: 10-0 nylon on the cornea (bury the knots), 8-0 or 10-0 absorbable on the conjunctiva.
- Ring devices: sutureless for acute surface disease.
- Add a bandage contact lens after many procedures to protect the membrane.
Problems
- Early dissolution or displacement (infection, inflammation, wrong orientation).
- Haematoma under the membrane.
- Theoretical infection transmission: use screened tissue from an eye bank or licensed supplier.
Pearls
- The sponge test: the stromal side is sticky, the epithelial side is not.
- Inlay: epithelium up, cut to fit. Onlay: bigger than the defect.
- Rinse glycerol out of cryopreserved membrane before use.
Common mistakes
- Placing an inlay upside down, so it dissolves instead of epithelialising.
- Cutting an onlay too small to cover the defect edges.
- Using unscreened tissue.
Test yourself: flip cards
Quick quiz
Related: Pterygium for Residents: Grading, Surgery and Preventing Recurrence, Fibrin Glue for Pterygium Autograft: Reliseal, Fibroseal and Tisseel Compared, Preparation and Technique, Keratoplasty Types: PK vs DALK vs DSAEK vs DMEK, Cornea, Bandage Contact Lenses and Punctal Plugs: Indications, Choosing the Size and Type, Fitting and Follow-Up.
Key sources
- Dua HS, Gomes JAP, King AJ, Maharajan VS. The amniotic membrane in ophthalmology. Surv Ophthalmol. 2004;49:51-77
- Malhotra C, Jain AK. Human amniotic membrane transplantation: different modalities of its use in ophthalmology. World J Transplant. 2014;4:111-121
- Tseng SCG. Amniotic membrane transplantation for ocular surface reconstruction. Biosci Rep. 2001;21:481-489
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