Cyclodestruction is an effective method for ophthalmologists to reduce intraocular pressure in glaucoma patients. Recently, ultrasound cycloplasty has been proved to be an effective and safe method for the treatment of glaucoma [11, 12]. UCP generates high-intensity focused ultrasound through micro transducers, inducing ciliary body coagulation so as to treat glaucoma. The present study aimed to evaluate the efficacy of a single UCP procedure in patients with primary open-angle glaucoma, angle-closure glaucoma, secondary glaucoma, or neovascular glaucoma. Results showed that the IOP after UCP treatment at each follow-up time point was significantly lower than those before treatment. The average IOP reduced from 37.35 ± 13.79 mmHg to 24.91 ± 9.95 mmHg at day 1 and fluctuated to 19.25 ± 11.78 mmHg after 6 months. Moreover, the number of anti-glaucoma agents decreased from 3.35 ± 1.23 before treatment to 1.65 ± 1.40 (Day-1) and 1.60 ± 1.64 (Month-6).
These findings are consistent with previous reports. Chen and Guo treated 61 eyes (7 POAG, 17 PACG, 26 NVG, 11 secondary glaucoma) with UCP and followed up for 18 months and found that IOP reduction was more than 60% at 1 month after UCP, and more than 30% 18 months after UCP, with a success rate of 94. 55% at 7 days after UCP, and more than 60% 18 months after UCP [13]. We did a correlation analysis and found that that there was a significant linear correlation between the decrease in postoperative intraocular pressure and preoperative intraocular pressure. It is considered to be that the higher the patient's IOP, the larger the range of ciliary body rupture set by UCP treatment parameters, resulting in a greater decrease in IOP. This indicates that UCP treatment for glaucoma can significantly reduce intraocular pressure and the number of anti-glaucoma agents.
The classical treatment method for cyclodestructive therapy is cyclocryotherapy. However, this method causes significant damage to eye tissue and have many complications, as well as significant pain for patients, which limits its application in clinical practice[14].As a new type of cyclodestructive therapy,UCP has less pain after treatment.In particular, we evaluated the eye pain score in this study. We used the Numeric Rating Scale (NRS) to quantify eye pain.UCP brought significant postoperative relief of the painfulness due to reduction of IOP. The patient's eye pain score continued to decrease within 7 days after treatment, which may be related to the use of an eye speculum and tear film damage during the treatment.
UCP has many advantages such as target organ selectivity and controllable thermal effects, which can focus on the ciliary tissue through the conjunctiva and sclera, producing a single point like injury with a dose-response relationship and no damage to adjacent structures. During the UCP treatment, retrobulbar anesthesia was used, and no serious complications occurred (e. g. eye atrophy and vision loss over two lines). Therefore, UCP can smoothly control intraocular pressure, and effectively reduce the complications and ciliary body damage caused by traditional treatments [15].
UCP treatment still has some complications, although not severe. The most common complications in our study were conjunctival hyperemia (47.83%), scleral imprint (39. 13%) after treatment, and mild to moderate pain (21.74%) during the treatment. Conjunctival hyperemia and induced astigmatism disappeared within one month spontaneously or after medication. Some patients experienced varying degrees of pain during the treatment, possibly due to factors such as different pain thresholds and ocular inflammation preoperatively.
Scleral imprint is a relatively rare complication for UCP treatment in some studies [16], but it is common in this study.Some researchers suggested that scleral imprint was a sign of scleral thinning [17]. But in this study, all patients with scleral imprints did not show any other signs of scleral thinning, such as staphyloma until the end of follow-up.Also in Bartłomiej’s study,he treated 78 patients with primary and secondary refractory glaucoma with UCP, and found that scleral thickness in superior scleral mark increased after UCP and reduced to its initial value without significant difference after the procedure [18]. A underwent UBM examination on the scleral imprint found that sclera is not obviously thinner but interlayer structure is sparse[19].Rodolfo Mastropasqua found formation of new (or the enlargement of preexisting) intrascleral hyporeflective spaces after UCP through anterior segment optical coherence tomography[20].We suggest there may be a histological rearrangement, which may explain the gray appearance found under slit lamp.It deserves our attention and long-term observation.
The UCP affects corneal parameters immediately after the procedure, but this change may be temporary, since all parameters returned to their initial values at 1 month after treatment, which is considered to be acceptable clinically. Similarly, Bolek’s study enrolled 78 patients with glaucoma and found that there was a significant difference in the anterior keratometry after UCP, which disappeared 3 months postoperatively [19]. Furthermore,a study conduted by Deb-Joardar[17] mentioned that the surgically induce astigmatism after UCP was transient.In clinical practice, these changes after UCP treatment may be caused by sclera [18]. We also found scleral imprints after UCP, but the scleral imprints did not disappear throughout the follow-up.Thus we speculated that changes in anterior keratometry may be related to cases where the ultrasound probe was too close to the limbus, rather than changes in the sclera. This also indicates that the cornea has recoverable biological characteristics.Of course, further clinical research is required.
The limitations of this study include: (1) The follow-up time was short and some patients were lost to followed up,so the long-term effect is still uncertain; (2) The sample size is relatively small; (3) We did not compare the efficacy with other ciliary body destructive surgeries or glaucoma surgeries; (4) Heterogeneity in glaucoma types and baseline IOP levels. Further research is in progress to investigate IOP control with long term follow-up.