Macular Hole Staging: Gass vs IVTS Classification
Last updated: October 2026
Short answer: macular holes are classified by the older Gass clinical stages (1 to 4) or the OCT-based International Vitreomacular Traction Study (IVTS) system. IVTS describes full-thickness holes as small (≤250 µm), medium (>250–400 µm) or large (>400 µm) by their minimum linear diameter, and notes whether vitreomacular traction is present. Size strongly predicts surgical success.
Gass staging (clinical)
| Stage | Description |
|---|---|
| 1A | Impending hole: foveolar detachment, a yellow spot at the fovea |
| 1B | Impending hole: foveal detachment, a yellow ring |
| 2 | Small full-thickness hole (<400 µm) |
| 3 | Full-thickness hole ≥400 µm, vitreous still attached to the optic disc |
| 4 | Full-thickness hole with complete posterior vitreous detachment (Weiss ring) |
IVTS classification (OCT-based)
- Vitreomacular adhesion (VMA): vitreous attached at the fovea without retinal distortion.
- Vitreomacular traction (VMT): attachment with distortion of the foveal surface or architecture.
- Full-thickness macular hole (FTMH), described by:
- Size (minimum linear diameter at the narrowest point): small ≤250 µm, medium >250–400 µm, large >400 µm
- VMT status: with or without traction
- Cause: primary (idiopathic, from vitreous traction) or secondary (for example, trauma or high myopia)
- A lamellar hole is a partial-thickness defect; an ERM pseudohole has no tissue loss. See OCT reading tips.
Measuring the hole on OCT
- Measure the minimum linear diameter: the narrowest point of the hole, measured roughly parallel to the RPE.
- The base diameter (at the RPE) is larger and is used in some prognostic indices.
- Check the whole cube, not one line, to find the true narrowest point.
Management overview
- Standard surgery: pars plana vitrectomy, internal limiting membrane (ILM) peeling and gas tamponade.
- Small holes have the highest closure rates; small holes with VMT may close after vitreous release (pharmacological or pneumatic) in selected cases.
- Large holes benefit from techniques such as the inverted ILM flap.
- Duration matters: chronic holes close less reliably and recover less vision.
- Post-operative face-down positioning is used by many surgeons, although its necessity for smaller holes is debated.
Clinical test
Watzke-Allen test: a thin slit beam is shone across the fovea. A patient with a full-thickness hole sees a break in the line; a pseudohole usually shows only thinning or distortion.
2026 update: large and chronic holes
| Technique | When it is used |
|---|---|
| Inverted ILM flap | Large holes (over about 400 µm), myopic and chronic holes: a flap of ILM is folded over the hole and raises closure rates from about 60–70% to over 90% |
| Autologous ILM transplant, lens capsule or amniotic membrane plugs | Persistent or recurrent holes after a previous peel |
| Face-down positioning | Shorter or no positioning works for small holes; still advised for large holes |
| Ocriplasmin | Small holes with vitreomacular traction: largely abandoned because of modest results and side effects |
Sources for this update: Michalewska Z, et al. Inverted internal limiting membrane flap technique for large macular holes. Ophthalmology. 2010;117:2018-2025.
Frequently asked questions
What is a large macular hole?
In the IVTS classification, a full-thickness hole with a minimum linear diameter above 400 µm. Large holes have lower closure rates and often need techniques such as an inverted ILM flap.
What is the difference between Gass and IVTS staging?
Gass staging is clinical and based on fundus appearance and vitreous status. IVTS is OCT-based and classifies holes by size, VMT and cause, which better predicts surgical outcome.
How is a macular hole different from a lamellar hole?
A full-thickness hole extends through all retinal layers down to the RPE. A lamellar hole is a partial-thickness defect with the outer retina intact.
Related: macular hole retinal detachment, OCT reading tips and retina notes.
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