Ultrasound cycloplasty (UCP) is a ciliary body coagulation procedure that utilizes high-intensity focused ultrasound (HIFU)1). It is classified as a cyclo-ablative procedure and is indicated for cases where filtration surgery or tube shunt surgery is difficult or unsuccessful1)2).
| Item | UCP | Transscleral Cyclophotocoagulation (TS-CPC) |
|---|---|---|
| Energy Source | High-Intensity Focused Ultrasound | Diode Laser |
| Irradiation Method | Ring-shaped probe, 6 points simultaneously | G-probe, one point at a time |
| Postoperative pain | Relatively mild | Severe |
Conventional transscleral cyclophotocoagulation (TS-CPC) lacks quantifiability and carries the risk of phthisis bulbi due to excessive ciliary body destruction. UCP precisely focuses ultrasound energy on the ciliary body, minimizing damage to surrounding tissues.
Conventional transscleral cyclophotocoagulation (TS-CPC) uses a diode laser applied transsclerally to extensively destroy the ciliary body 1). The degree of destruction is poorly quantifiable; insufficient treatment fails to lower intraocular pressure, while excessive treatment risks phthisis bulbi. In contrast, UCP uses HIFU to precisely focus ultrasound on the ciliary body, causing less damage to surrounding tissues. Postoperative pain is also reported to be relatively mild. Additionally, UCP results in coagulative necrosis of only the ciliary epithelium, whereas cyclocryotherapy completely destroys the ciliary body.
Main Indications
Refractory glaucoma: Cases with poor intraocular pressure control despite medical therapy or filtration surgery 1)
Failed filtration surgery: Cases where filtration surgery or tube shunt surgery has failed or is difficult to perform 1)2)
Acute management of aqueous misdirection: Emergency treatment for malignant glaucoma 1)
Contraindications / Precautions
Risk of phthisis bulbi: Appropriate treatment parameters must be set to avoid excessive ciliary body destruction
Active intraocular inflammation: Avoid the procedure if inflammation is significant
Neovascular glaucoma: Reported to have a low success rate
The UCP device features a ring-shaped probe containing six piezoelectric transducers. Each transducer delivers ultrasound energy to six locations on the ciliary body at different timings. A coupling cone is placed on the eye and secured with low-pressure suction.
Peribulbar anesthesia is administered1)2). The anterior edge of the ciliary body is identified using transscleral illumination1).
The coupling cone is placed on the patient’s eye and secured with low-pressure suction to prevent rotation. The ultrasound probe is inserted into the coupling cone. The space between the probe, coupling cone, and eye is filled with ophthalmic irrigation solution (BSS) to ensure ultrasound conduction. Each transducer is activated sequentially to deliver ultrasound energy.
Topical antibiotics and anti-inflammatory drugs are used postoperatively. Conjunctival hyperemia and anterior chamber inflammation are usually transient and improve with observation.
| Complication | Frequency | Notes |
|---|---|---|
| Conjunctival hyperemia | Frequent | Usually transient |
| Intraocular inflammation | Frequent | Resolves in days to weeks |
| Cataract progression | Reported | Confirmed on long-term follow-up |
Scleral ring hyperemia is rarely observed. Postoperative day 1 pain has been reported to be significantly milder compared to transscleral cyclophotocoagulation (TS-CPC).
Hypotony or phthisis bulbi have not been reported in multiple clinical studies. A feature of UCP is the low risk of phthisis bulbi, which is a concern with conventional cyclodestructive procedures.
In multiple clinical studies, no cases of hypotony or phthisis bulbi have been reported after UCP. Conventional transscleral cyclophotocoagulation carries a risk of phthisis bulbi if the ciliary body is excessively destroyed, but UCP precisely focuses ultrasound on the ciliary body, causing less damage to surrounding tissues and resulting in coagulative necrosis limited to the ciliary epithelium. This selective action is thought to contribute to improved safety.
UCP delivers high-intensity focused ultrasound to the ciliary body, inducing thermal coagulation. It causes structural changes in the ciliary processes and vasculature, reducing aqueous humor production. Selective coagulative necrosis of the ciliary body is possible without damaging adjacent tissues.
The ciliary body is the tissue that produces aqueous humor, supplying it to the anterior chamber via active transport, ultrafiltration, and diffusion from the ciliary epithelium. Coagulative necrosis of the ciliary epithelium by UCP reduces this aqueous humor production capacity.
UCP is thought to expand the outflow spaces within the sclera and increase aqueous humor drainage through the uveoscleral outflow pathway. This pathway runs from the intercellular spaces at the anterior ciliary body, through the ciliary stroma, to the connective tissue of the suprachoroid, and then exits the eye via the connective tissue around blood vessels and nerves that penetrate the sclera.
However, some reports indicate that the intraocular pressure-lowering effect of UCP is mainly due to a reduction in aqueous humor production rate. One study found that aqueous humor flow decreased by 15% at 3 months after treatment, while no significant change was observed in uveoscleral outflow.
While cyclocryotherapy completely destroys the ciliary body, coagulative necrosis after UCP is shown to be limited to the ciliary epithelium. This selective action is presumed to contribute to reducing the risk of serious complications such as phthisis bulbi.
A multicenter prospective study on primary open-angle glaucoma reported a success rate of 74% (defined as no vision-threatening complications, no additional treatment needed, and ≥20% IOP reduction). A long-term study of 104 eyes with refractory glaucoma showed a decrease from preoperative 27.6 mmHg (on 3 medications) to 15.6 mmHg (on 2.8 medications) at 3 years, with a success rate of 55%.
A large retrospective study of 182 eyes showed a decrease from preoperative 23.46 mmHg to postoperative 16.24 mmHg, with a success rate of 85.6% at 24 months.
A randomized controlled trial in patients with concurrent cataract and open-angle glaucoma showed that the combined phacoemulsification + UCP group had significantly greater IOP reduction (median 7 mmHg vs 2 mmHg) and success rate (67.7% vs 16.7%) compared to phacoemulsification alone.
The effectiveness of a second UCP procedure in cases where intraocular pressure (IOP) rises again after the first UCP has also been studied. Success rates of 52.6% in the early elevation group (within 6 months postoperatively) and 55.5% in the late elevation group (after 6 months) have been reported, suggesting the efficacy of repeat procedures for patients who did not achieve sufficient effect from the initial treatment.
Future Challenges:
In a retrospective study of 31 eyes with IOP re-elevation after the first UCP, a second UCP achieved success rates of 52.6% in the early elevation group and 55.5% in the late elevation group. Even in cases where the initial procedure did not provide sufficient effect, additional IOP reduction can be expected from repeat procedures. However, long-term evaluation of cumulative ciliary body damage due to repeated procedures is necessary.
- European Glaucoma Society. Terminology and Guidelines for Glaucoma, 6th Edition. Br J Ophthalmol. 2025.
- European Glaucoma Society. Terminology and Guidelines for Glaucoma, 5th Edition. 2020.
