UGH syndrome (Uveitis-Glaucoma-Hyphema syndrome) is a complication caused by mechanical abrasion of the iris or angle vascular tissue by an intraocular lens (IOL). It presents with the triad of uveitis, glaucoma, and hyphema, but incomplete forms also exist. It was first named by Ellingson in 1978.
The initially reported typical mechanism was distortion of the footplate of an anterior chamber IOL causing lens movement and irritation of adjacent anterior chamber angle tissue. The incidence has decreased dramatically due to improvements in IOL design, materials, manufacturing, surgical techniques, and the widespread use of posterior chamber lenses. The annual incidence of UGH syndrome is reported to have decreased from 2.2–3% to 0.4–1.2% depending on lens type.
Reports continue, particularly associated with modern single-piece acrylic IOLs 2), and it is more likely to occur with single-piece IOLs placed outside the capsule or IOLs inserted in the ciliary sulcus. It is more common in the elderly but can occur at any age in patients with IOLs.
Onset ranges from several weeks to several years after surgery. It often follows a subacute or chronic course, and early postoperative onset is most common with anterior chamber IOLs. Onset is rare with in-the-bag fixation of posterior chamber IOLs.
Symptoms of UGH syndrome often appear intermittently.
The following findings are confirmed by slit-lamp microscopy and gonioscopy.
Anterior Segment Findings
Elevated intraocular pressure: Caused by obstruction of the trabecular meshwork.
Microhyphema / hyphema: Caused by abrasion of iris blood vessels.
Intraocular inflammation: Cells, flare, and hypopyon are observed.
Iris transillumination defects: Correspond to the contact area with the IOL.
Pigment dispersion: Iris pigment deposits on the trabecular meshwork.
IOL-related findings
IOL dislocation/malposition: Including misplacement of the haptics.
Contact between iris and IOL: Contact around the pupil is observed.
Iris neovascularization: Secondary to chronic inflammation.
Cystoid macular edema (CME): Observed in chronic cases.
Vitreous hemorrhage: May occur in cases with posterior capsule rupture.
Gonioscopy reveals blood in the angle, increased pigmentation of the trabecular meshwork, and signs of mechanical erosion. It is also useful for locating the IOL haptics.
The essence of UGH syndrome is mechanical stimulation of anterior segment tissues by the IOL.
Repeated mechanical trauma to the iris due to IOL malposition or subluxation is the main mechanism1). In addition, pseudophacodonesis has been reported as a risk factor2). Zonular laxity due to pseudoexfoliation syndrome, plateau iris configuration, and contact due to capsular fibrosis around the optic are also causes1).
When the IOL is in extracapsular or asymmetric fixation, the haptics directly contact the iris and surrounding tissues. Iris pigment released by abrasion clogs the trabecular meshwork, causing pigmentary glaucoma. Severe iris damage may be accompanied by iridocyclitis and hyphema.
Bleeding is more likely in patients using anticoagulants.
The diagnosis of UGH syndrome is a clinical diagnosis based on medical history and physical examination, with imaging tests used as adjuncts. This syndrome should be suspected in patients with a history of cataract surgery who present with recurrent uveitis, elevated intraocular pressure, and hyphema.
Check for anterior chamber inflammation (cells and flare), hyphema, iris transillumination defects, IOL malposition, and pigment deposition on the corneal endothelium.
Search for blood in the angle, increased pigmentation of the trabecular meshwork, and signs of mechanical erosion by the IOL haptic. This also helps identify the location of the haptic causing the erosion.
| Examination method | Main use |
|---|---|
| Ultrasound biomicroscopy (UBM) | Visualization of IOL-iris contact |
| Anterior segment OCT | Relationship between iris atrophy site and IOL position |
| Optical coherence tomography (OCT) | Evaluation of CME |
Ultrasound biomicroscopy can provide detailed visualization of the position of the IOL haptic and optic and their relationship with surrounding tissues, and is useful for confirming clinical suspicion and determining treatment strategy. Anterior segment OCT can confirm the correspondence between the area of iris atrophy and the site of IOL contact1).
UGH syndrome tends to be repeatedly underdiagnosed1). Differentiation from the following diseases is necessary.
Slit-lamp microscopy and gonioscopy are fundamental; iris transillumination defects and contact with the IOL are confirmed. Ultrasound biomicroscopy can directly visualize the contact between the haptic and the iris, which is useful for definitive diagnosis 2).
The curative treatment for UGH syndrome is surgical intervention for the IOL, but until surgery, symptoms are controlled with medication.
Administered as symptomatic therapy until definitive surgery is performed.
However, because the cause is mechanical invasion of the iris, the long-term effect of eye drops is low. Once a definitive diagnosis is made, surgical treatment becomes the first choice.
Repositioning, removal, and/or exchange of the IOL usually resolves recurrent hyphema and uveitis.
Hermoso-Fernandez et al. (2021) reported a case of a 56-year-old man with recurrent hypertensive uveitis 8 months after cataract surgery 1). Due to repeated intraocular pressure elevation, the optic disc cupping progressed from 0.3 to 0.9. After YAG laser posterior capsulotomy, vitreous hemorrhage and inferior retinal detachment developed. Vitrectomy combined with scleral buckling resolved the posterior displacement of the IOL and eliminated contact with the iris, leading to resolution of hypertensive uveitis attacks.
The fundamental pathology of UGH syndrome is repeated mechanical trauma to uveal tissue caused by the IOL.
The optic or haptic part of the IOL rubs against the iris, ciliary body, and anterior chamber angle tissues including the trabecular meshwork. Erosion due to footplate distortion or edge imperfections also contributes. This abrasion disrupts the blood-aqueous barrier, releasing pigment, red blood cells, proteins, and white blood cells into the anterior chamber.
Intraocular pressure elevation occurs through multiple mechanisms3)4).
Electron microscopy of explanted IOLs sometimes reveals melanosomes on the IOL surface, thought to originate from damaged iris pigment epithelial cells.
The square-edged haptics of a single-piece acrylic IOL placed in the ciliary sulcus can cause pigment dispersion, iris transillumination defects, elevated intraocular pressure, and recurrent inflammation 2). Even in in-the-bag fixation cases, the following mechanisms may lead to onset 1).
In chronic cases, the pathology may extend to the posterior pole, potentially causing vitreous hemorrhage or cystoid macular edema 1). Repeated elevation of intraocular pressure can lead to progression of glaucomatous optic neuropathy, resulting in irreversible visual field damage.
In the case reported by Hermoso-Fernandez et al. (2021), recurrent hypertensive uveitis caused the optic disc cupping to progress from 3/10 to 9/10, leading to concentric visual field constriction with only the central 10 degrees remaining 1). In such cases, the use of alpha-2 agonists may also be considered. Neuroprotective effects on retinal ganglion cells via direct inhibition of NMDA receptors have been reported.
Continuous improvements in IOL design are underway. Due to the problem of iris chafing caused by square-edged haptics, round-edge designs and surface treatment improvements of IOL materials are being considered 2). For eyes with uveitis, reports indicate that acrylic IOLs and heparin surface-modified (HSM) polymethyl methacrylate IOLs have shown good outcomes 2).
Research on appropriate size selection for ACIOL is progressing, and a common guideline is to add 1 mm to the horizontal corneal diameter (white-to-white distance). An improperly sized ACIOL can cause UGH through tilt or haptic chafing 2). Improved preoperative measurement accuracy using anterior segment OCT or ultrasound biomicroscopy is expected.
