Iris retraction syndrome (IRS) is a rare condition characterized by posterior bowing of the peripheral iris and adhesion of the iris body to the anterior lens surface, presenting distinctive anterior segment findings.
This condition is the opposite of iris bombé. Unlike iris bombé, where posterior chamber pressure exceeds anterior chamber pressure, in iris retraction syndrome, the anterior chamber pressure exceeds posterior chamber pressure, pulling the iris posteriorly and causing marked deepening of the anterior chamber.
For most of the 20th century, it was called “vitreous retraction syndrome,” but in 1984, Campbell published a case series of 9 patients and established the current name “iris retraction syndrome.”
Iris retraction syndrome is usually associated with rhegmatogenous retinal detachment (RRD), posterior open-globe injury, or hypotony. Postoperative cases have also been reported, including after cataract surgery (with posterior chamber intraocular lens implantation) and after vitrectomy. Many of these postoperative cases have underlying rhegmatogenous retinal detachment, and the iris morphology returns to normal after retinal detachment repair.
Iris bombe is a condition in which the posterior chamber pressure exceeds the anterior chamber pressure, causing the iris to bulge forward in an arcuate shape. In contrast, iris retraction syndrome is the opposite: the anterior chamber pressure exceeds the posterior chamber pressure, causing the iris to curve backward and adhere to the anterior lens surface, deepening the anterior chamber. These two conditions have completely opposite pathologies, and correct differentiation is important for determining treatment strategy.
In iris retraction syndrome secondary to rhegmatogenous retinal detachment, the most common chief complaint is painless visual loss. The following symptoms may be observed.
The following are characteristic on slit-lamp examination:
Anterior Segment Findings
Deepening of the anterior chamber: The peripheral iris is displaced posteriorly, causing marked deepening of the anterior chamber (reverse of iris bombé).
Posterior synechiae: Posterior synechiae are observed almost circumferentially (360 degrees).
Iris-lens contact: The iris body adheres to the anterior lens surface, and the posterior chamber disappears.
Corneal findings: Mild to moderate inflammation may present as microcystic edema or Descemet’s membrane folds.
Angle and fundus findings
Wide open angle: Gonioscopy reveals a wide open angle due to posterior displacement of the peripheral iris.
Retinal detachment: Fundus examination and B-mode ultrasound confirm rhegmatogenous retinal detachment and choroidal detachment.
Hypotony: Low intraocular pressure is usually observed, but the pressure may be normal in some cases.
Findings of proliferative vitreoretinopathy: In chronic cases, findings of proliferative vitreoretinopathy (PVR) are added.
Pupillary examination reveals a pupil with extremely weak light reflex due to almost circumferential posterior synechiae and central iris-lens contact. Ultrasound biomicroscopy (UBM) is useful for detailed evaluation of anterior segment tissues.
The most important risk factor for iris retraction syndrome is the presence of retinal detachment as an underlying disease.
Diagnosis is made by combining the following examinations.
| Disease | Difference from Iridociliary Retraction Syndrome |
|---|---|
| Uveitis | Often not accompanied by deepening of the anterior chamber. |
| Inflammatory glaucoma | Associated with elevated intraocular pressure |
| Pigment dispersion syndrome | Peripheral iris posterior bowing but wide open angle with pigment dispersion |
| Fuchs heterochromic iridocyclitis | Iris heterochromia may also be seen in iris retraction syndrome |
| Deepening of the anterior chamber after surgery | Differentiated by medical history and ultrasound biomicroscopy |
In iris retraction syndrome, the fundus is often not directly observable due to anterior segment opacity and inflammation. B-mode ultrasonography allows noninvasive assessment of the presence and extent of retinal detachment or choroidal detachment, and is essential for determining treatment strategy.
The goal of treatment is to resolve iris retraction and repair the underlying rhegmatogenous retinal detachment.
Pharmacological mydriasis is attempted to release central posterior synechiae. Reformation of the posterior chamber and anterior movement of the iris from the lens surface may resolve the iris retraction. However, long-standing permanent adhesions may not respond. Cases have been reported where iris retraction syndrome resolved with anti-inflammatory therapy and aggressive mydriasis, even without treating the underlying rhegmatogenous retinal detachment.
Visual prognosis depends on the duration and extent of the rhegmatogenous retinal detachment that caused iris retraction syndrome. The shorter the time from onset of rhegmatogenous retinal detachment to surgical repair, the better the prognosis. Long-standing rhegmatogenous retinal detachment with proliferative vitreoretinopathy tends to have a poor prognosis.
The potential for vision recovery largely depends on the extent, duration, and presence of proliferative vitreoretinopathy in rhegmatogenous retinal detachment. If repaired early, there is room for recovery, but in severe cases with long-standing detachment or proliferative vitreoretinopathy, vision may not significantly improve even if the eye is preserved surgically. Thorough consultation with the attending physician is necessary.
Two main theories have been proposed regarding the mechanism of iris retraction syndrome.
When rhegmatogenous retinal detachment occurs, the retinal pigment epithelium acts as a subretinal pump, draining fluid at a rate exceeding aqueous humor production. This leads to low intraocular pressure, secondary inflammation, ciliochoroidal detachment, and influx of proteins and cells into the vitreous cavity. The suction effect behind the iris causes pupillary block and posterior bowing of the iris, potentially leading to proliferative vitreoretinopathy.
As evidence for this theory, cases have been reported in which patients with rhegmatogenous retinal detachment repeatedly alternated between iris bombe and iris retraction syndrome with the use and discontinuation of aqueous humor suppressants. When aqueous suppression shifts the hydrodynamic balance toward outflow via the “subretinal pump,” the iris is pulled posteriorly.
Arguments against the hydrodynamic pressure gradient theory have also been proposed based on reports of iris retraction syndrome associated with non-rhegmatogenous exudative retinal detachment. In these two cases, the iris retraction syndrome resolved several months before retinal reattachment, with mydriasis and synechiolysis.
The authors speculated that chronic intraocular inflammation causes decreased aqueous humor production by the ciliary body and increased leakage from iris vessels. Combined with retrograde flow through the trabecular meshwork under low intraocular pressure, anterior chamber pressure exceeds posterior chamber pressure, leading to posterior bowing of the iris. They also proposed that chronic inflammation causes irido-zonular and irido-ciliary adhesions, fixing the iris to the anterior lens surface and inducing pupillary block.
In anterior proliferative vitreoretinopathy, fibrous proliferative membranes form at the vitreous base after vitrectomy. When these membranes cover the ciliary processes, marked hypotony occurs, the iris is pulled posteriorly, and the retina is pulled anteriorly, potentially leading to phthisis bulbi.
The two mechanisms, the Campbell theory and the Geyer theory, are still under debate. Although most cases occur in association with rhegmatogenous retinal detachment, the existence of cases associated with non-rhegmatogenous exudative retinal detachment suggests aspects that cannot be explained by the “subretinal pump” alone. Prospective studies that analyze inflammatory cytokines and aqueous humor dynamics in detail are needed.
With the increase in cataract and vitreous surgeries, cases of postoperative iridoschisis have been observed. Atypical findings such as deep anterior chamber and wide open angle postoperatively may suggest iridoschisis, and care must be taken not to overlook underlying rhegmatogenous retinal detachment after surgery.
