Treatment of glaucoma with high-intensity focused ultrasound

Iris neovascularization and neurotrophic keratopathy following ultrasound cycloplasty in refractory glaucoma: case series

BACKGROUND

Ultrasound cycloplasty is a noninvasive surgery used to reduce intraocular pressure in patients with glaucoma, with fewer severe complications. This report presents several cases of iris neovascularization and neurotrophic keratopathy following ultrasound cycloplasty.

CASE PRESENTATION

Six patients diagnosed with refractory glaucoma underwent ultrasound cycloplasty at our clinic. Three cases developed iris neovascularization at postoperative day 3, week 2 and week 4 respectively, with intraocular pressure ranging from 12 to 24 mmHg. The other three cases developed neurotrophic keratopathy at postoperative week 3, week 6 and week 8 which completely healed within 60 days.

CONCLUSIONS

Iris neovascularization and neurotrophic keratopathy can be triggered after ultrasound cycloplasty, which are uncommon and self-limited but potentially vision-threatening. Preoperative risk assessment and regular postoperative follow-up are recommended to manage complications effectively.

Development of Moderate Intensity Focused Ultrasound (MIFU) for Ocular Drug Delivery

The purpose of this study is to develop a method for delivering antiinflammatory agents of high molecular weight (e.g., Avastin) into the posterior segment that does not require injections into the eye (i.e., intravitreal injections; IVT). Diseases affecting the posterior segment of the eye are currently treated with monthly to bimonthly intravitreal injections, which can predispose patients to severe albeit rare complications like endophthalmitis, retinal detachment, traumatic cataract, and/or increased intraocular. In this study, we show that one time moderate intensity focused ultrasound (MIFU) treatment can facilitate the penetration of large molecules across the scleral barrier, showing promising evidence that this is a viable method to deliver high molecular weight medications not invasively. To validate the efficacy of the drug delivery system, IVT injections of vascular endothelial growth factor (VEGF) were used to create an animal model of retinopathy. The creation of this model allowed us to test anti-VEGF medications and evaluate the efficacy of the treatment. In vivo testing showed that animals treated with our MIFU device improved on the retinal tortuosity and clinical dilation compared to the control group while evaluating fluorescein angiogram (FA) Images.

Micropulse vs. continuous wave transscleral cyclophotocoagulation in neovascular glaucoma

Neovascular glaucoma (NVG) is a refractory form of glaucoma, associated with important morbidity, for which no consensus exists regarding the optimal choice of therapy. The primary aim of our study was to compare the performances of micropulse transscleral cyclophotocoagulation (MP-TSCPC) and continuous wave transscleral cyclophotocoagulation (CW-TSCPC) in the treatment of neovascular glaucoma (NVG). A total of 24 eyes for MP-TSCPC and 22 eyes for CW-TSCPC, all with NVG were included. The procedures were performed using either the Iridex Cyclo G6 (IRIDEX Laser System), the MP3, or the G-Probe devices. Intraocular pressure (IOP), visual acuity (VA), the mean number of antiglaucoma medications, and postoperative complications were monitored. The minimum follow-up was 12 months. The success rate at 12 months was 54.5% in the CW-TSCPC group and 33.3% in the MP-TSCPC group. The mean IOP at baseline was 35.82 mm Hg for CW-TSCPC and 34.71 mm Hg for MP-TSCPC. The change from baseline in IOP at 12 months was 11.95 mm Hg in the CW-TSCPC group and -8.04 mm Hg in the MP-TSCPC group. There was a significant difference in the occurrence of serious complications (worsening of VA, hypotony, and phthisis bulbi) between the two methods, with CW-TSCPC associated with more important adverse effects (P=0.045). There was a decrease in the number of topical antiglaucoma medications in both groups: in the MP-TSCPC group from a mean number of 2.6 at baseline, to 1.7 at 3 months, followed by a slight increase to 2.1 at 12 months and in the CW-TSCPC group from 2.8 at baseline, to 1.4 at 3 months and 1.9 at 12 months. Our study concluded that both MP-TSCPC and CW-TSCPC could manage NVG, but, while CW-TSCPC revealed higher IOP control in the long term (which did not reach statistical significance), it also had a significantly lower safety profile.

Ultrasound Cyclo Plasty for Treatment of Surgery-Naïve Open-Angle Glaucoma Patients: A Prospective, Multicenter, 2-Year Follow-Up Trial

Background: The purpose of this prospective study was to evaluate the efficacy and safety of the Ultrasound Cyclo Plasty (UCP) procedure using high-intensity focused ultrasound in surgery-naïve open-angle glaucoma patients. Methods: prospective, non-randomized, single-arm, multicenter clinical trial. Sixty-six eyes with primary open-angle glaucoma, intraocular pressure (IOP) ≥21 mmHg and with no history of filtering surgery were enrolled. Patients were treated by UCP with a therapy probe comprising six piezoelectric transducers, consecutively activated for 8 s each. Complete ophthalmic examination was performed before the procedure, 1 day after the procedure, and 1, 3, 6, 12, 18 and 24 months after the procedure. Primary outcomes were complete success (defined as IOP lowering from baseline ≥20% without additional glaucoma medications) and vision-threatening complications. Secondary outcomes were the presence of complications and the reduction of the number of medications used. Results: IOP was significantly reduced after one procedure (p < 0.05), from a mean pre-operative value of 24.3 ± 2.9 mmHg (n = 2.3 hypotensive medications) to a mean value of 15.9 ± 3.6 mmHg (n = 2.2 hypotensive medications) at 2 years (mean IOP lowering of 33%). Surgical success was achieved in 74% of eyes. Notwithstanding side effects such as transient anterior chamber inflammation, refractive error changes, transient hypotony and macular edema, no major intra or post-operative complications such as phthisis, induced cataract, neovascularization or significant vision loss were observed. Conclusions: Ultrasound Cyclo Plasty is a valuable, effective and well-tolerated procedure to lower IOP in patients with open-angle glaucoma without previous filtering surgery.

Efficacy and safety of high-dose ultrasound cyclo-plasty procedure in refractory glaucoma

AIM

To evaluate the efficacy and safety of high-dose ultrasound cyclo-plasty (UCP) for the treatment of refractory glaucoma in Chinese patients.

METHODS

In this 6-month retrospective study, 37 eyes of 37 patients suffering from severe glaucoma with uncontrolled intraocular pressure (IOP) of ≥21 mm Hg underwent 8-s ultrasonic cyclocoagulation with ten active piezoelectric elements. A complete ophthalmic examination was performed before and at 1d, 1, 3, 6mo after UCP. Therapeutic success was defined as IOP reduction from baseline ≥20% and IOP ≥5 mm Hg without adding new glaucoma medication compare to baseline at the 6-month follow-up visit. In addition to mean IOP at each follow-up visit, medications used and complications were also detected and compared to baseline.

RESULTS

After UCP procedure, the mean IOP was significantly reduced (P<0.01) from the preoperative 44.1±11.9 mm Hg to postoperative 26.7±11.8 mm Hg at 3mo, and 30.4±14.5 mm Hg at 6mo. The overall mean IOP reductions achieved at 3 and 6mo were 39% and 31% compared to baseline IOP. Sixty-one percent of patients responded well to UCP treatment with a mean IOP reduction of 48% at 3mo and 42% at 6mo. Ocular pain in most of patients were alleviated. No serious intraoperative or postoperative complications occurred.

CONCLUSION

High-dose UCP treatment is an effective and safe procedure to reduce IOP in Chinese patients with severe glaucoma.

The Effect of High-Intensity Focused Ultrasound on Aqueous Humor Dynamics in Patients with Glaucoma

PURPOSE

To investigate the effects of high-intensity focused ultrasound (HiFU) on aqueous humor dynamics in patients with glaucoma.

DESIGN

Comparative, nonrandomized, interventional study.

PARTICIPANTS

Adult patients with a diagnosis of open-angle glaucoma or ocular hypertension with suboptimal intraocular pressure (IOP) control despite maximum medical treatment who required further IOP optimization.

METHODS

All patients underwent comprehensive ophthalmic examination before aqueous humor dynamics study measurements, including fluorophotometry and digital Schiøtz tonography. All patients received 6 seconds of HiFU therapy. Aqueous humor dynamics studies were repeated 3 months after the treatment (patients had 4-week washout from their glaucoma medication before their aqueous humor dynamics study measurements at baseline and the 3-month visit).

MAIN OUTCOME MEASURES

Intraocular pressure, facility of topographic outflow, aqueous flow rate, and uveoscleral outflow.

RESULTS

Thirty eyes of 30 patients were included in the study. At the 3-month postoperative visit, the mean postwashout IOP was reduced by 16% (31.7±5.3 vs. 26.6±4.8 mmHg, P = 0.004), and aqueous flow rate was decreased by 15% (2.07±0.73 vs. 1.77±0.55 μl/min, P = 0.05) from baseline. Neither the tonographic outflow facility nor the uveoscleral outflow was significantly different from baseline. There is a 20% risk of treatment failure (those who needed further glaucoma surgical intervention) within 1 month after a single HiFU treatment (n = 6). Only 25 patients (80%) were able to undergo post-treatment washout measurements, and in these eyes, only 26.6% of eyes achieved >20% IOP reduction at 3 months compared with baseline.

CONCLUSIONS

We investigated the aqueous humor dynamics effects of a cyclodestructive procedure and specifically HiFU in patients with uncontrolled open-angle glaucoma on maximum tolerated medical therapy. High-intensity focused ultrasound reduced IOP 3 months postoperatively by 16% and aqueous flow decreased by 15% without any significant effect on tonographic outflow facility and uveoscleral outflow.

Efficacy and safety of ultrasonic circular cyclocoagulation with second-generation probe in glaucoma: A retrospective study

Background

To assess the efficacy and safety of the second-generation probe of ultrasonic circular cyclocoagulation (UC3) in naive or refractory glaucoma, with a 6-month follow-up.

Methods

A retrospective consecutive case-series study included patients having a UC3 procedure with the second-generation probe of the EyeOP1 device, intraocular pressure (IOP) ≥ 21 mmHg and under maximum tolerated medical treatment, with or without previous glaucoma surgery. Surgical success was defined at the 6-month post-operative visit as IOP > 5 and ≤ 21 mmHg with IOP reduction ≥ 20% from baseline, without any reoperation, and visual acuity better than negative light perception.

Results

100 patients were included and 97 (97.0%; 97 eyes) attended the 6-month follow-up. At 6 months, surgical success was obtained in 48 eyes (49.5%). Intraocular pressure was reduced from a mean ± SD preoperative value of 28.0 ± 5.6 mmHg to 19.3 ± 7.1 mmHg at 6 months (p<0.0001). The proportion of eyes requiring oral acetazolamide decreased from 57.0% to 30.0% between baseline and 6 months after surgery (p = 0.0007). We observed 15 (15.0%) cases of postsurgical macular edema, 8 (8.0%) of hypotony, and 20 (20.0%) of visual acuity loss > 2 Snellen lines. Postsurgical macular edema was associated with a history of epiretinal membranes, uveitis or retinal detachment. Risk factors for hypotony were a history of diabetes or trabeculectomy.

Conclusions

The second-generation UC3 probe significantly reduced IOP in eyes with naive and refractory glaucoma but severe post-operative complications were often observed. Further studies are needed to better identify responders and decrease the high risk for complications associated with the procedure.

Ultrasonic Generation of Pulsatile and Sequential Therapeutic Delivery Profiles from Calcium-Crosslinked Alginate Hydrogels

Control over of biological processes can potentially be therapeutically regulated through localized biomolecular deliveries. While implantable hydrogels can provide localized therapeutic deliveries, they do not traditionally provide the temporally complex therapeutic delivery profiles required to regulate complex biological processes. Ionically crosslinked alginate hydrogels have been shown to release encapsulated payloads in response to a remotely applied ultrasonic stimulus, thus potentially enabling more temporally complex therapeutic delivery profiles. However, thorough characterizations of how different types of therapeutic payloads are retained and ultrasonically released need to be performed. Additionally, the impact of potentially disruptive ultrasonic stimulations on hydrogel structure and temperature need to be characterized to better understand what range of ultrasonic signals can be used to trigger release. To perform these characterizations, calcium-crosslinked alginate hydrogels were loaded with various model macromolecules (dextrans), chemotherapeutics, and protein signaling factors and exposed to a variety of single-pulse and multi-pulse ultrasonic signals at various amplitudes and durations. In response to single-pulsed ultrasonic exposures, quantifications of molecular release, degree of gel erosion, and increase in hydrogel temperature revealed that the ultrasonic stimulations required for statistically significant therapeutic deliveries often eroded and heated the gels to unacceptable levels. However, multi-pulse ultrasonic exposures were shown to achieve significant amounts of therapeutic release while keeping gel erosion and temperature increase at modest levels. Finally, experiments were performed demonstrating that ultrasonic stimulation could be used to generate drug release profiles shown to have potential therapeutic benefits (e.g., pulsatile and sequential anticancer delivery profiles). This work underscores the potential of using ultrasonically responsive polymeric hydrogels for providing on-demand control over more complex therapeutic deliver profiles and enhancing drug delivery strategies in cancer therapies and beyond.

A review on the use of magnetic fields and ultrasound for non-invasive cancer treatment

Current popular cancer treatment options, include tumor surgery, chemotherapy, and hormonal treatment. These treatments are often associated with some inherent limitations. For instances, tumor surgery is not effective in mitigating metastases; the anticancer drugs used for chemotherapy can quickly spread throughout the body and is ineffective in killing metastatic cancer cells. Therefore, several drug delivery systems (DDS) have been developed to target tumor cells, and release active biomolecule at specific site to eliminate the side effects of anticancer drugs. However, common challenges of DDS used for cancer treatment, include poor site-specific accumulation, difficulties in entering the tumor microenvironment, poor metastases and treatment efficiency. In this context, non-invasive cancer treatment approaches, with or without DDS, involving the use of light, heat, magnetic field, electrical field and ultrasound appears to be very attractive. These approaches can potentially improve treatment efficiency, reduce recovery time, eliminate infections and scar formation. In this review we focus on the effects of magnetic fields and ultrasound on cancer cells and their application for cancer treatment in the presence of drugs or DDS.

Transscleral Diode Laser Cyclophotocoagulation: A Comparison of Slow Coagulation and Standard Coagulation Techniques

PURPOSE

To compare the outcomes of standard pop-titrated transscleral cyclophotocoagulation (TSCPC) and slow-coagulation TSCPC in the treatment of glaucoma.

DESIGN

Retrospective case series.

SUBJECTS

This study included 78 eyes with glaucoma of any type or stage that underwent TSCPC as part of their treatment course.

METHODS

This study compared 52 eyes treated with slow coagulation TSCPC to 26 eyes treated with standard pop-titrated TSCPC. Patient demographics, treatment course, surgical techniques, settings and outcomes were assessed.

MAIN OUTCOME MEASURES

The main outcome measures were visual acuity (VA), intraocular pressure (IOP) and post-surgical complications.

RESULTS

The initial LogMAR VA was 1.94 (0.73) [mean (SD)] in the slow coagulation TSCPC group and 1.71 (0.90) in the standard TSCPC group (p=0.507). Initial IOP was 37 (13) mm Hg in the slow coagulation group and 39 (13) mm Hg in the standard group (p=0.297). The follow-up periods were 16.36 months and 24.68 months for the slow coagulation and standard groups (p=0.124). VA remained better than light-perception in 71.1% of slow coagulation treated patients and 65.0% of standard TSCPC treated patients (p=0.599). IOP remained below 20 mm Hg in 46% of slow coagulation treated patients and 44% of standard TSCPC treated patients (p=0.870). The mean number of complications was higher in the standard group [1.46 (1.24)] versus the slow coagulation group [0.62 (0.75)] (p=0.002). The incidence of the need for a second procedure (slow coagulation- 28.8%, standard- 23.1%, p=0.588) and maximum number of medications needed to control IOP postoperatively (p=0.771) were similar between the two groups.

CONCLUSIONS

In this case series, slow coagulation TSCPC and standard pop-titrated TSCPC resulted in similar VA and IOP outcomes in the treatment of glaucomatous eyes. The complication profiles of the techniques were also comparable, although standard TSCPC had a higher incidence of prolonged inflammation postoperatively. This study suggests that slow coagulation TSCPC may achieve equivalent control of IOP while reducing the incidence of prolonged post-operative inflammation-a feared complication of TSCPC-when compared to standard "pop-titrated" TSCPC.

High intensity focused ultrasound cyclocoagulation in dogs with primary glaucoma: a preliminary study

The objective was to assess the effect of high intensity focused ultrasound (HIFU) on intraocular pressure (IOP) in dogs with primary glaucoma (PG). Seven dogs (13 eyes) presenting with PG as diagnosed by a raised IOP (> 20 mm Hg) associated with consistent gonioscopy and ultrasound biomicroscopy of the ciliary cleft, with no other ocular disease. Patients were divided into 3 groups, corresponding to their pre-operative IOP (group 1 ranging from 21 to 30 mm Hg, group 2 from 31 to 40 and group 3 for 40 and above). Ciliary process sonication was achieved with a probe containing one high-frequency transducer operating at 21 MHz during 5 seconds. Six sites were treated in patients from group 1, 8 in group 2, 10 in group 3, under general anesthesia. Post-operative treatment consisted of systemic meloxicam and topical carbonic anhydrase inhibitors, beta-blockers and prostaglandins analogues. No intraoperative complications were observed. Conjunctival hyperaemia occurred in eyes from group 2 (66%) and 3 (100%). Conjunctival burns were visible in 2 patients from group 3. One patient from group 3 experienced a hypertensive spike during the first hours post-op with associated pain. The hypotensive effect of HIFU was observed in all groups. Normotensive IOP (≤20 mm Hg) was reached in all patients until the last recheck at 6 months post op. Despite the small number of patients included in the study, HIFU appears to be a promising option for the management of PG in dogs.

Application of high intensity focused ultrasound for treatment of open-angle glaucoma in Indian patients

Purpose:

The aim of this study is to assess the efficacy of ultrasound cycloplasty (UCP) in Indian patients with open angle glaucoma (OAG).

Methods:

A prospective interventional study was designed to treat 73 eyes of 73 patients with OAG with the EyeOP1 device equipped with six miniaturized cylindrical piezoelectric transducers. Two treatment protocols of ultrasound delivery depending on exposure time (8 s and 10 s of shot per transducer) were used. Complete ophthalmic examination, ocular biometry and anterior segment optical coherence tomography were performed preoperatively and patients were followed up at day 1, day 7 and months 1, 2, 3, 6, and 12. The primary outcome measure was “successful” intraocular pressure (IOP) control defined as IOP reduction ≥20% from baseline and IOP value >5 mm Hg at the last follow-up visit. Secondary outcomes were the occurrence of complications and mean IOP during the follow-up period.

Results:

In all patients, the mean IOP reduced from 23.5 ± 3.0 mmHg before treatment to 15.7 ± 5.4 mmHg at 12 months (P < 0.05). Successful IOP control after a single procedure was 78.3% (79% and 78% in the 8 s and 10 s groups, respectively) at 12 months. Overall, the mean IOP reduction achieved in responding patients was 41% (standard deviation = 12%). Notwithstanding minor side effects such as transient pain, anterior chamber reaction, and refractive error changes, no major intraoperative or postoperative complications (severe hypotony or phthisis) were observed during the follow-up.

Conclusion:

Our short-term results reveal that UCP is a simple, safe, and noninvasive procedure which enables to significantly reduce the IOP in patients with OAG. The study results in Indian eyes corroborate findings in earlier studies on Caucasian eyes.

Ultrasound Cyclo Plasty in Eyes with Glaucoma

Glaucoma is a chronic disease caused by the progressive degeneration of the optical nerve fibers, resulting in decreased visual field that can lead to severe visual impairment, and eventually blindness. This manuscript describes a simple, surgeon-friendly, non-incisional technique, named Ultrasound Cyclo Plasty (UCP), for reducing intraocular pressure (IOP) in glaucoma patients. The technique determines a selective coagulation necrosis of the ciliary body; in addition, the stimulation of supra-choroidal and trans-scleral portions of the uveo-scleral outflow pathway has been recently proposed. UCP shows several technical improvements in ultrasound technology compared to previous techniques, providing more precise focusing on the target zone. The procedure is performed in the operating room under peribulbar anesthesia. Briefly, the coupling cone is put in contact with the eye and the ring probe, that contains six piezoelectric transducers which produce the ultrasound beams, is inserted inside it. Their proper centering over the ocular surface represents a crucial step for the correct targeting of the ciliary body. Sterile balanced salt solution is used to fill the empty spaces to ensure ultrasound acoustic propagation. Surgical treatment consists in the sequential automatic activation of each of the six transducers, for a total duration of less than 3 min. The patient leaves the hospital 1 h after the procedure with the treated eye patched. In the present study, 10 patients with open-angle glaucoma were followed-up during at least 12 months after the procedure. IOP was reduced at each interval compared to pre-operative, as well as the number of hypotensive medications. Twenty percent of patients did not respond to the treatment, and needed subsequent surgery to better control IOP. Treatment tolerability was good, with no cases of hypotony or phthisis. The UCP procedure is simpler, faster, safer, and less invasive than traditional cyclodestructive procedures with similar results in reducing IOP.

Evolution of Cyclophotocoagulation

Cyclodestructive techniques have been a treatment option for refractory glaucoma since its first use in the 1930s. Over the past nine decades, cyclodestruction has advanced from the initial cyclodiathermy to micropulse transscleral cyclophotocoagulation (MP-TSCPC) which is the current treatment available. Complications associated with cyclodestruction including pain, hyphema, vision loss, hypotony and phthisis have led ophthalmologists to shy away from these techniques when other glaucoma treatment options are available. Recent studies have shown encouraging clinical results with fewer complications following cyclophotocoagulation, contributing greatly to the current increase in the use of cyclophotocoagulation as primary treatment for glaucoma. We performed our literature search on Google Scholar Database, Pubmed, Web of Sciences and Cochrane Library databases published prior to September 2017 using keywords relevant to cyclodestruction, cyclophotocoagulation and treatment of refractory glaucoma.

High-Intensity Focused Ultrasound Circular Cyclocoagulation in Glaucoma: A Step Forward for Cyclodestruction?

The ciliary body ablation is still considered as a last resort treatment to reduce the intraocular pressure (IOP) in uncontrolled glaucoma. Several ablation techniques have been proposed over the years, all presenting a high rate of complications, nonselectivity for the target organ, and unpredictable dose-effect relationship. These drawbacks limited the application of cyclodestructive procedures almost exclusively to refractory glaucoma. High-intensity focused ultrasound (HIFU), proposed in the early 1980s and later abandoned because of the complexity and side effects of the procedure, was recently reconsidered in a new approach to destroy the ciliary body. Ultrasound circular cyclocoagulation (UC³), by using miniaturized transducers embedded in a dedicated circular-shaped device, permits to selectively treat the ciliary body in a one-step, computer-assisted, and non-operator-dependent procedure. UC³ shows a high level of safety along with a predictable and sustained IOP reduction in patients with refractory glaucoma. Because of this, the indication of UC³ was recently extended also to naïve-to-surgery patients, thus reconsidering the role and timing of ciliary body ablation in the surgical management of glaucoma. This article provides a review of the most used cycloablative techniques with particular attention to UC³, summarizing the current knowledge about this procedure and future possible developments.

Focused ultrasound in ophthalmology

The use of focused ultrasound to obtain diagnostically significant information about the eye goes back to the 1950s. This review describes the historical and technological development of ophthalmic ultrasound and its clinical application and impact. Ultrasound, like light, can be focused, which is crucial for formation of high-resolution, diagnostically useful images. Focused, single-element, mechanically scanned transducers are most common in ophthalmology. Specially designed transducers have been used to generate focused, high-intensity ultrasound that through thermal effects has been used to treat glaucoma (via ciliodestruction), tumors, and other pathologies. Linear and annular transducer arrays offer synthetic focusing in which precise timing of the excitation of independently addressable array elements allows formation of a converging wavefront to create a focus at one or more programmable depths. Most recently, linear array-based plane-wave ultrasound, in which the array emits an unfocused wavefront and focusing is performed solely on received data, has been demonstrated for imaging ocular anatomy and blood flow. While the history of ophthalmic ultrasound extends back over half-a-century, new and powerful technologic advances continue to be made, offering the prospect of novel diagnostic capabilities.

Multicenter clinical trial of high-intensity focused ultrasound treatment in glaucoma patients without previous filtering surgery

PURPOSE

To evaluate the efficacy and safety of the ultrasonic circular cyclocoagulation procedure in patients with open-angle glaucoma naïve of previous filtering surgery.

METHODS

Prospective non-comparative interventional clinical study conducted in five French University Hospitals. Thirty eyes of 30 patients with open-angle glaucoma, intra-ocular pressure (IOP) > 21 mmHg and with no previous filtering glaucoma surgeries were sonicated with a probe comprising six piezoelectric transducers. The six transducers were activated with a 6-s exposure time. Complete ophthalmic examinations were performed before the procedure and at 1 day, 1 week, 1, 2, 3, 6 and 12 months after the procedure. Primary outcomes were qualified surgical success (defined as IOP reduction from baseline ≥20% and IOP > 5 mmHg with possible re-intervention and without hypotensive medication adjunction) and complete surgical success (defined as IOP reduction from baseline ≥20%, IOP > 5 mmHg and IOP < 21 mmHg with possible re-intervention and without hypotensive medication adjunction) at the last follow-up visit and vision-threatening complications. Secondary outcomes were mean IOP at each follow-up visit compared with baseline, medication use, complications and re-interventions.

RESULTS

Intra-ocular pressure was significantly reduced (p < 0.05) from a mean pre-operative value of 28.2 ± 7.2 mmHg (n = 3.6 hypotensive medications) to 19.6 ± 7.9 mmHg at 12 months (n = 3.1 hypotensive medications and n = 1.1 procedures) (mean IOP reduction of 30%). Qualified success was achieved in 63% of eyes (19/30) (mean IOP reduction of 37% in these eyes) and complete success in 46.7% of eyes (14/30) (mean IOP reduction of 37% in these eyes) at the last follow-up. No major intra- or post-operative complications occurred.

CONCLUSIONS

The UC(3) procedure seems to be an effective and well-tolerated method to reduce IOP in patients with open-angle glaucoma without previous filtering surgery.

Uveo-scleral outflow pathways after ultrasonic cyclocoagulation in refractory glaucoma: an anterior segment optical coherence tomography and in vivo confocal study

AIMS

To evaluate, using anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM), the uveo-scleral aqueous humour (AH) outflow pathways after ultrasonic circular cyclocoagulation (UCCC).

METHODS

Forty-four patients with refractory glaucoma underwent 4 or 6 s UCCC (group 1, 24 eyes; group 2, 20 eyes). UCCC was successful when the preoperative intraocular pressure (IOP) reduced by one-third. AS-OCT and IVCM were performed at baseline and at month 1 to evaluate the sclera and conjunctiva. The main outcomes were mean intra-scleral hyporeflective spaces area (MIHSA: mm²) at AS-OCT, mean density and area of conjunctival microcysts (MMD: cysts/mm²; MMA: µm²) at IVCM. The relations between MIHSA, MMA and MMD with IOP were analysed.

RESULTS

Mean baseline IOP was 26.9±2.8 mm Hg in group 1 and 27.5±4.0 in group 2. Intra-scleral hyporeflective spaces and microcysts were observed in both groups, without significant differences in MIHSA, MMA and MMD. At month 1, UCCC was successful in 63.6% of patients (41.6% in group 1, 80% in group 2), and IOP reduced to 18.8±3.2 (30.1%) and 17.1±2.7 mm Hg (38.7%), respectively (p<0.001). MIHSA showed a twofold and threefold increase in group 1 and 2 (p<0.05), with a significant difference between groups (p<0.05). MMA and MMD increased in both groups (p<0.05), with values higher in group 2 (p<0.05). Significant relations were found between MIHSA and IOP in both groups (p<0.01).

CONCLUSIONS

UCCC induced anatomical modifications of sclera and conjunctiva, which suggested that the trans-scleral AH outflow enhancement is one of the possible mechanisms exploited by ultrasounds to reduce IOP.

High-intensity focused ultrasound treatment in refractory glaucoma patients: results at 1 year of prospective clinical study

PURPOSE

To evaluate the safety and efficacy of the ultrasonic circular cyclo-coagulation procedure using high-intensity focused ultrasound by a miniaturized annular device containing 6 piezoceramic transducers in patients with refractory glaucoma.

METHODS

This was a prospective interventional noncomparative study of 20 eyes of 20 patients with refractory glaucoma. All eyes were treated with 6 activated transducers operating at 21 MHz. Ultrasound biomicroscopy and a complete ophthalmic examination were performed before the procedure and at 1 day, 1 week, and 1, 3, 6, and 12 months after the procedure. Primary outcomes were surgical success (defined as intraocular pressure (IOP) reduction from baseline ≥20% and IOP &gt;5 mm Hg) at the last follow-up visit. Secondary outcomes were mean IOP at each follow-up visit compared to baseline, medication use, complications, and re-interventions.

RESULTS

Intraocular pressure was significantly reduced (p&lt;0.01) from a mean preoperative value of 36.4 ± 5.7 mm Hg to a mean postoperative value of 22.5 ± 10.3 mm Hg at 12 months. Four patients needed to be re-treated. The mean IOP reduction achieved was 38%. Surgical success was achieved in 13 of 20 eyes (65%). No major intraoperative or postoperative complications occurred.

CONCLUSIONS

Ultrasonic circular cyclo-coagulation using high-intensity focused ultrasound delivered by a circular miniaturized device containing 6 piezoceramic transducers is an effective and well-tolerated method to reduce IOP in patients with refractory glaucoma.

Noninvasive glaucoma procedures: current options and future innovations

Noninvasive glaucoma procedures (NIGPs) represent a new dawn in the management of glaucoma. They try to fill the gap between the shortcoming of invasive glaucoma surgeries and antiglaucoma medications. NIGPs were introduced as an adjunct or alternative treatments for glaucoma. Some of these procedures have shown good efficacy with few serious complications. Hence, they are now used as both primary and adjunctive therapy for glaucoma. The most common NIGPS involve laser and ultrasound technologies. Currently, the portfolio of NIGPs includes argon laser trabeculoplasty, selective laser trabeculoplasty, and micropulse diode laser trabeculoplasty. More recent innovations include therapeutic ultrasound for glaucoma, ultrasonic circular cyclocoagulation, and deep wave trabeculoplasty.

Contribution of inertial cavitation in the enhancement of in vitro transscleral drug delivery

In ocular drug delivery, the sclera is a promising pathway for administering drugs to both the anterior and posterior segments of the eye. Due to the low permeability of the sclera, however, efficient drug delivery is challenging. In this study, pulsed ultrasound (US) was investigated as a potential method for enhancing drug delivery to the eye through the sclera. The permeability of rabbit scleral tissue to a model drug compound, sodium fluorescein, was measured after US-irradiation at 1.1 MHz using time-averaged acoustic powers of 0.5-5.4 W (6.8-12.8 MPa peak negative pressure), with a fixed duty cycle of 2.5% for two different pulse repetition frequencies of 100 and 1000 Hz. Acoustic cavitation activity was measured during exposures using a passive cavitation detector and was used to quantify the level of bubble activity. A correlation between the amount of cavitation activity and the enhancement of scleral permeability was demonstrated with a significant enhancement in permeability of US exposed samples compared to controls. Transmission electron microscopy showed no evidence of significant alteration in viability of tissue exposed to US exposures. A pulsed US protocol designed to maximum cavitation activity may therefore be a viable method for enhancing drug delivery to the eye.

Focused ultrasound development and clinical adoption: 2013 update on the growth of the field

The field of therapeutic focused ultrasound, which first emerged in the 1940s, has seen significant growth, particularly over the past decade. The eventual widespread clinical adoption of this non-invasive therapeutic modality require continued progress, in a multitude of activities including technical, pre-clinical, and clinical research, regulatory approval and reimbursement, manufacturer growth, and other commercial and public sector investments into the field, all within a multi-stakeholder environment. We present here a snapshot of the field of focused ultrasound and describe how it has progressed over the past several decades. It is assessed using metrics which include quantity and breadth of academic work (presentations, publications), funding trends, manufacturer presence in the field, number of treated patients, number of indications reaching first-in-human status, and quantity and breadth of clinical indications.

Therapeutic applications of ultrasound in ophthalmology

Therapeutic ultrasound, although less well known than ultrasound for diagnostic imaging, has become a topic of growing interest in ophthalmology. High intensity focused ultrasound (HIFU) for the treatment of glaucoma and ultrasonic drug delivery are the two main areas of research and potential clinical applications. For the treatment of glaucoma, the specific advantage of HIFU, particularly when compared to the laser, is that the energy can be focused through optically opaque media, especially through the sclera which is a strongly light-scattering medium. HIFU is therefore a possible method for partial coagulation of the ciliary body (an anatomical structure responsible for the production of the liquid filling the eye) and, hence, reducing intraocular pressure and the risk of glaucoma. Ocular drug bioavailability also remains a challenge, being limited by multiple barriers to drug entry and lacrimal drainage, and making it difficult to achieve a sufficient drug concentration for numerous diseases of the front and back of the eye. As the front wall of the eye (cornea and anterior sclera) is a pathway for topically applied drugs, locally applied ultrasound has been proposed as a way of enhancing the delivery and activity of drugs and genes. Despite the fact that experimental studies seem to confirm the potential benefit of ultrasound ocular drug delivery, there is still a lack of clinical evidence. The aim of this contribution is to provide an update on recent advances in the field of therapeutic ultrasound in ophthalmology.

Targeted and reversible blood-retinal barrier disruption via focused ultrasound and microbubbles

The blood-retinal barrier (BRB) prevents most systemically-administered drugs from reaching the retina. This study investigated whether burst ultrasound applied with a circulating microbubble agent can disrupt the BRB, providing a noninvasive method for the targeted delivery of systemically administered drugs to the retina. To demonstrate the efficacy and reversibility of such a procedure, five overlapping targets around the optic nerve head were sonicated through the cornea and lens in 20 healthy male Sprague-Dawley rats using a 690 kHz focused ultrasound transducer. For BRB disruption, 10 ms bursts were applied at 1 Hz for 60 s with different peak rarefactional pressure amplitudes (0.81, 0.88 and 1.1 MPa). Each sonication was combined with an IV injection of a microbubble ultrasound contrast agent (Definity). To evaluate BRB disruption, an MRI contrast agent (Magnevist) was injected IV immediately after the last sonication, and serial T1-weighted MR images were acquired up to 30 minutes. MRI contrast enhancement into the vitreous humor near targeted area was observed for all tested pressure amplitudes, with more signal enhancement evident at the highest pressure amplitude. At 0.81 MPa, BRB disruption was not detected 3 h post sonication, after an additional MRI contrast injection. A day after sonication, the eyes were processed for histology of the retina. At the two lower exposure levels (0.81 and 0.88 MPa), most of the sonicated regions were indistinguishable from the control eyes, although a few tiny clusters of extravasated erythrocytes (petechaie) were observed. More severe retinal damage was observed at 1.1 MPa. These results demonstrate that focused ultrasound and microbubbles can offer a noninvasive and targeted means to transiently disrupt the BRB for ocular drug delivery.

Overview of therapeutic ultrasound applications and safety considerations

Applications of ultrasound in medicine for therapeutic purposes have been accepted and beneficial uses of ultrasonic biological effects for many years. Low-power ultrasound of about 1 MHz has been widely applied since the 1950s for physical therapy in conditions such as tendinitis and bursitis. In the 1980s, high-pressure-amplitude shock waves came into use for mechanically resolving kidney stones, and "lithotripsy" rapidly replaced surgery as the most frequent treatment choice. The use of ultrasonic energy for therapy continues to expand, and approved applications now include uterine fibroid ablation, cataract removal (phacoemulsification), surgical tissue cutting and hemostasis, transdermal drug delivery, and bone fracture healing, among others. Undesirable bioeffects can occur, including burns from thermal-based therapies and severe hemorrhage from mechanical-based therapies (eg, lithotripsy). In all of these therapeutic applications of ultrasound bioeffects, standardization, ultrasound dosimetry, benefits assurance, and side-effect risk minimization must be carefully considered to ensure an optimal benefit to risk ratio for the patient. Therapeutic ultrasound typically has well-defined benefits and risks and therefore presents a manageable safety problem to the clinician. However, safety information can be scattered, confusing, or subject to commercial conflicts of interest. Of paramount importance for managing this problem is the communication of practical safety information by authoritative groups, such as the American Institute of Ultrasound in Medicine, to the medical ultrasound community. In this overview, the Bioeffects Committee of the American Institute of Ultrasound in Medicine outlines the wide range of therapeutic ultrasound methods, which are in clinical use or under study, and provides general guidance for ensuring therapeutic ultrasound safety.

Thermal ablation of uterine fibroids using MR-guided focused ultrasound-a truly non-invasive treatment modality

Uterine fibroids are a significant source of morbidity for women of reproductive age. Definitive treatment has traditionally been a hysterectomy, but increasingly women are not prepared to undergo such an invasive procedure for a benign and usually self-limiting condition. Although a number of minimally invasive techniques are now available, focused ultrasound has a considerable advantage over them as it is completely non-invasive and does not require an anaesthetic. Improvements in imaging techniques, particularly magnetic resonance imaging (MRI), have enabled the accurate planning, targeting and monitoring of treatments. We review the early experience of focused ultrasound surgery for the treatment of fibroids, and, in particular, the results of the recent phase I, II and III multi-centre clinical trials. These trials and other studies which demonstrate that MR-guided focused ultrasound ablation is feasible, safe and appears to have an efficacy that is comparable with other treatment modalities are described. This technique has the advantages of being non-invasive and being deliverable as an out-patient procedure.

Improved visualization of high-intensity focused ultrasound lesions

Spectral parameter imaging in both the fundamental and harmonic of backscattered radio-frequency (RF) data were used for immediate visualization of high-intensity focused ultrasound (HIFU) lesion sites. A focused 5-MHz HIFU transducer with a coaxial 9-MHz focused single-element diagnostic transducer was used to create and scan lesions in chicken breast and freshly excised rabbit liver. B-mode images derived from the backscattered RF signal envelope were compared with midband fit (MBF) spectral parameter images in the fundamental (9-MHz) and harmonic (18-MHz) bands of the diagnostic probe. Images of HIFU-induced lesions derived from the MBF to the calibrated spectrum showed improved contrast (approximately 3 dB) of tumor margins versus surround compared with images produced from the conventional signal envelope. MBF parameter images produced from the harmonic band showed higher contrast in attenuated structures (core, shadow) compared with either the conventional envelope (3.3 dB core; 11.6 dB shadow) or MBF images of the fundamental band (4.4 dB core; 7.4 dB shadow). The gradient between the lesion and surround was 3.4 dB/mm, 6.9 dB/mm and 17.2 dB/mm for B-mode, MBF-fundamental mode and MBF-harmonic mode, respectively. Images of threshold and "popcorn" lesions produced in freshly excised rabbit liver were most easily visualized and boundaries best-defined using MBF-harmonic mode.

Intraluminal high intensity ultrasound treatment in the esophagus under fast MR temperature mapping: in vivo studies

New curative and palliative treatments are needed to respond to the poor prognosis of esophageal cancer. The purpose of this study was to determine whether magnetic resonance imaging (MRI) and MR thermometry can be used to monitor the thermal ablation induced by an intraluminal high-intensity ultrasound applicator positioned in the esophagus. Experiments were performed in vivo in 2 pig esophagi (25 thermal lesions per pig). Respiratory gated or cardiac gated MR thermometry was performed with segmented echo-planar imaging gradient echo sequences. All MR acquisitions were performed without susceptibility artifacts or radiofrequency interference with the ultrasound device. The experimental procedure proposed for accurate measurement of temperature in the esophagus was found to achieve an SD of +/- 1.5 degrees C for respiratory gating and +/- 3.1 degrees C for cardiac gating. Gd-enhanced T(1)-weighted images were used to depict coagulation necrosis. Autopsy was performed immediately after the treatment. Ultrasound effects were inspected visually, and the dimensions of the lesions in the liver neighboring the esophagus were compared with those determined on the MRI images. The visually assessed thermal lesions showed good correlation with the MRI data (10% mean volume difference). The feasibility of esophageal thermal ablation using intraluminal high-intensity ultrasound and of on-line MR temperature monitoring was demonstrated.

Closed-form solution for the thermal dose delivered during single pulse thermal therapies

This study provides a closed form, analytical expression for the thermal dose delivered by a single heating pulse. The solution is derived using the effective cooling method and the non-linear Sapareto-Dewey equation to determine the thermal dose delivered by the time-temperature history of a treatment. The analytical solutions are used to determine the optimal treatment conditions, i.e. those that exactly deliver the desired thermal dose at a specified time. For purposes of illustration, this study focuses on a 'conservative' clinical approach in which the desired thermal dose is delivered at the end of the 'cool down' period. The analytical results show that, after a clinical strategy has been chosen (e.g. conservative, aggressive or intermediate), the user can only specify two free variables for such an optimal treatment. Results are presented which suggest that a practical approach would be to specify both (1) the desired thermal dose to be delivered to the target (the clinically relevant outcome) and (2) the peak temperature to be reached (a measurable, clinically useful, patient dependent response variable that can be employed in feedback control systems); and then determine the associated, optimal heating magnitude and duration that need to be used to reach that dose and temperature. The results also reveal that, with a given patient condition and power deposition distribution (together specifying an effective cooling time constant for the treatment) and a specified thermal dose, there is a maximum allowable peak temperature that, if exceeded, will result in 'over-dosing' the heated tissue. The results also show that avoiding such non-optimal 'over-dosing' will be difficult in most high temperature therapies since, when high temperatures are produced in tissues, the temperature decay must be very fast in order to avoid over-dosing during the cooling period. Such rapid cooling can only occur if short effective cooling time constants are present-either as a result of large tissue blood flows in the patient or due to large conduction effects induced by the use of highly localized power deposition sources.

Blood perfusion and thermal conduction effects in Gaussian beam, minimum time single-pulse thermal therapies

A previous analytical study has shown that the minimum obtainable treatment time for a single pulse that delivers a given thermal dose to a specified point at a specified time occurs when the temperature at that point is rapidly raised to its maximum allowable value. The present study extends that result by investigating the spatial distribution of thermal effects of a single Gaussian shaped focal zone pulse that reaches that maximum allowable temperature at the center point of the focal zone. Analytical solutions are obtained that separately include the effects of perfusion and conduction. This situation is analyzed for a conservative treatment strategy in which the desired thermal dose is delivered when the tumor cools down to basal conditions. The results show that for a specified thermal dose delivered by a spherical Gaussian beam with focal widths below approximately 4 mm, the maximum allowable temperature, the minimum obtainable treatment time, and the size of the treatment zone (as a percentage of the size of the Gaussian beam) are all independent of the tissue blood perfusion, and are only functions of the focal zone size. Conversely, for focal widths above approximately 20 cm, these results are independent of the focal width and are only functions of blood perfusion. Between these two sizes (where most practical treatments will occur, since single pulses with widths of <4 mm and >20 cm will be uncommon in practice) a transition zone exists in which both perfusion and conduction effects are important. Thus while it is possible to implement a truly perfusion-independent, single pulse thermal treatment by using focal widths of <4 mm, in practice many such pulses will be needed to treat most tumors. This is especially true since the nonlinear temperature/thermal dose relationship causes the width of the delivered dose distribution to be only approximately 25%-30% of the width of the focal zone. However, shorter overall treatment times can be obtained when multiple pulses are linked together by using larger focal zone sizes, but this gain in treatment time is accompanied by increased effects of perfusion, illustrating the conflict between attaining both perfusion-independence and minimal treatment time for multiple-pulse thermal treatments.

Intraluminal ultrasound applicator compatible with magnetic resonance imaging "real-time" temperature mapping for the treatment of oesophageal tumours: an ex vivo study

High intensity ultrasound has shown considerable ability to produce precise and deep thermal coagulation necrosis. Focused, cylindrical, spherical or plane transducers have been used to induce high temperatures in tissues to coagulate proteins and kill cells. Recently magnetic resonance imaging (MRI) has been used, with extracorporeal or intracavitary focused transducers and cylindrical interstitial applicators, to monitor temperature distribution and provide feedback during heating procedures. If intraluminal applicators are used, the active part is in contact with the region of interest and it is essential to provide an accurate view of heat deposition and the extent of coagulation necrosis close to the transducer. The purpose of this study was to develop a 10 mm diameter intraluminal ultrasound applicator, designed to treat oesophageal cancers and compatible with MRI "real-time" temperature mapping. The active part of the ultrasound applicator, covered by a latex balloon, is a 15 X 8 mm2 plane transducer, which is in contact with the tumours during treatment. Each ultrasound exposure generates coagulation necrosis, in an area with the approximate shape of a rectangular parallelepiped up to 10 mm deep. When the exposures were repeated by rotating the applicator on its axis, sector-based or cylindrical volumes of necrosis could be produced, matching the shape of oesophageal cancers. Ex vivo trials were performed to demonstrate the applicator's compatibility with a clinical MRI scanner (1.5 T). MRI signals were acquired without any magnetic susceptibility distortion, even close to the applicator. Fast (0.72 images per second) 2D temperature mapping was performed during ultrasound exposure, using temperature-related proton resonance frequency shift at a resolution of 0.5 degrees C. Coagulation necrosis viewed with inversion recovery sequences, were in good agreement with the qualitative macroscopic observations made for the few cases tested in this study.

Transoesophageal ultrasound applicator for sector-based thermal ablation: first in vivo experiments

New curative and palliative treatments must be proposed to respond to the bad long-term prognosis of oesophageal cancers. It has been demonstrated that high intensity ultrasound (US) can induce rapid, complete and well-defined coagulation necrosis. For the treatment of this cancer, we designed an applicator that uses an intraductal approach. The active part is an air-backed plane transducer. It has an external water-cooling system and operates at 10 MHz. Ex vivo experiments conducted on pig liver demonstrated the ability of this applicator to generate, by rotating the transducer, circular or sector-based coagulation necroses at predetermined depths up to 13 mm, with an excellent angular precision. The treatment of sector-based oesophageal tumours may be critical, where both malignant and healthy tissues are covered by the US beam. Thus, in vivo trials were conducted on five healthy pig oesophaguses to determine the maximal thermal dose that will not induce a perforation of the oesophagus or surrounding tissues. From the results of previous studies, this dose is high enough to treat pathological tissues. These promising results indicate that this US system represents a safe and effective tool for the clinical treatment of oesophageal tumours.

A multiple focused probe approach for high intensity focused ultrasound based surgery

To produce deep-seated surgical lesions using ultrasound requires high power and intensity levels at the target sites. Conventionally, large transducers are used which require big apertures and so are generally suitable only for extra-corporeal access. Such transducers also result in strong off-focus maxima, where the resulting hot spots can destroy normal tissue whilst deep-seated large tissue volumes are being ablated. This paper describes a new approach in which it is proposed that multiple probes are used simultaneously, each at a relatively low power, to result in an overlapping focused region of high temperature without strong off-focus hot spots. Robotic techniques could be used to move the individual probes in coordination to sweep out the desired region of tissue ablation. Simulation and planning are the key to quality prediction for high intensity focused ultrasound (HIFU). Simplified two-dimensional and three-dimensional models of HIFU probes have been developed to study the characteristics of various multi-probe configurations. Preliminary simulation results show that the multi-probe system can be arranged successfully to minimise off-focus hot spots. Experimental results are presented which validate the modality and confirm this positive finding. Further prediction studies and planning will be necessary to achieve the most appropriate desired treatment, by varying the pulse duration and spacing.

Preclinical development of noninvasive vascular occlusion with focused ultrasonic surgery for fetal therapy

OBJECTIVE

This study was undertaken to investigate the ability of focused ultrasonic surgery to occlude blood flow in vivo.

STUDY DESIGN

A 5-mm linear track exposure of 1.7-MHz focused ultrasound was applied across the femoral vessels for 5 seconds. Free field spatial peak intensities in the range of 1,000 to 4,660 W x cm(-2) were used. Vascular occlusion was confirmed after demonstration of an absent distal arterial pulse and an absent flow signal on magnetic resonance angiography and subtracted (after minus before) contrast-enhanced dual-echo steady-state sequences.

RESULTS

The minimum intensity for consistent vascular occlusion was 1,690 W x cm(-2) at a focal depth of 5 mm when the transducer was moved at 1 mm x s(-1) orthogonal to the direction of blood flow.

CONCLUSIONS

This study demonstrates that focused ultrasonic surgery can achieve reproducible vascular occlusion in vivo. Potential obstetric applications include noninvasive ultrasonographically guided occlusion of placental vessels mediating interfetal transfusion in monochorionic twins.

Vascular occlusion using focused ultrasound surgery for use in fetal medicine

OBJECTIVE

Focused ultrasound surgery (FUS) is being developed clinically for the non-invasive treatment of soft tissue tumours of the prostate, bladder, liver, kidney, muscle and breast. In the work described in this paper, the application of FUS is extended to investigate the potential to induce vascular occlusion, with the aim of applying the technique to problems in fetal medicine and oncology.

METHODS

In this feasibility study the occlusion of femoral blood flow in vivo is demonstrated using an array of multiple single exposures of 1.7 MHz focused ultrasound. These were placed in two rows of four lesions at a focal depth of 5 mm. The 4660-W cm-2 (free field spatial peak intensity) 2-s exposures were placed 2 mm apart. Vascular patency was assessed using a Siemens Vision (1.5T) magnetic resonance (MR) imaging scanner with an extremity coil, and intravenous gadolinium contrast agent. FLASH and FISP MR sequences were used to obtain full 3D data sets providing information on soft tissue damage and perfusion.

RESULTS AND CONCLUSION

Total vascular occlusion was achieved in four of nine cases and significant vascular disruption in five of nine cases. Refinement of the FUS technique and long-term studies are now indicated prior to initial clinical application in fetal medicine.

Ciliary body ablation: where are we and how did we get here?

Management of intraocular pressure remains the cornerstone of glaucoma treatment. Related medical and surgical practices involve increasing aqueous outflow or decreasing aqueous production. Filtration procedures that increase aqueous outflow are the first-line surgical defense in glaucoma. However, some cases of glaucoma are resistant to such treatment. In these cases, ciliary body ablation by various methods has had substantial success. Surgical manipulation of aqueous production has been used in glaucoma management since the turn of the century. Techniques have progressed markedly as technology has produced more discrete therapies designed to decrease aqueous production by destroying ciliary body epithelium. Over the past 90 years success has been achieved with a wide range of techniques, from surgical disinsertion of the ciliary body to recent laser and ultrasound techniques. With the development of more precise contact lasers and endoscopic visualization, side effects have been reduced and clinical success rates increased.

Postsurgical hypotony: relationship to fistulization, inflammation, chorioretinal lesions, and the vitreous

Hypotony is a natural occurrence, symptom, and complication of surgical treatment. With more sophisticated and aggressive techniques, postsurgical hypotony recently has been given increased attention as an obstacle to success of surgery for glaucoma and retinal detachment. Whereas two standard deviations below normal pressure (15.9-5.8 = 10.1 mm Hg) can be called hypotonous, most eyes, depending on scleral rigidity, lid pressure, eye rubbing, or corneal or retinal edema, will be symptomatic at < 5 mm Hg. Hypotony can be defined as the low pressure (whether acute, transient, chronic or permanent) which, in an individual eye, leads to functional changes (whether asymptomatic or symptomatic) and structural changes (whether reversible or irreversible). Depending on its duration and degree, postsurgical hypotony produces characteristic tissue changes that often are modified by, but separate from, the tissue changes caused by an underlying disease or its surgical treatment. This review summarizes the situations, variably associated with hypotony, that occur after such interventions as cataract extraction, filtering surgery, cyclodialysis, cyclodestruction, and vitreoretinal surgery, in addition to the reported pathomechanisms of hypotony and its proposed treatments.

Ultrasound biomicroscopic imaging of the effects of YAG laser cycloablation in postmortem eyes and living patients

PURPOSE

The authors performed a series of experiments designed to determine if early effects of YAG laser cycloablation could be detected by ultrasound biomicroscopy in postmortem eyes and living patients. They also designed an apparatus that allowed simultaneous ultrasound biomicroscopic imaging of YAG laser cycloablation.

METHODS

Treated and untreated regions of postmortem eyes treated with YAG cycloablation were imaged and compared. Treatment was placed at varying distances from the limbus in postmortem eyes and the resulting effects imaged. Histologic examinations were performed after imaging. Six living patients had ultrasound biomicroscopy before and after YAG cycloablation. An apparatus combining contact YAG laser and ultrasound biomicroscopy was used in postmortem eyes.

RESULTS

Early treatment effects imaged included ciliary epithelial disruption, ciliary epithelial separation, and bubble formation. Ultrasound biomicroscopic findings varied with the distance of treatment from the limbus and were maximal below the treatment site. Results of histologic examination showed close correlation to the ultrasound biomicroscopic images. Similar findings to those found in postmortem eyes were found in living patients after treatment. The apparatus combining contact YAG and ultrasound biomicroscopy allowed realtime imaging of effects of YAG laser cycloablation.

CONCLUSIONS

The ability of ultrasound biomicroscopy to detect changes associated with cyclodestructive procedures potentially could provide us with a method of improving treatment precision and correlating treatment effect with clinical response.

The effect of high-intensity focused ultrasound on intraocular pressure in therapy-resistant glaucoma 3-4 months and 1 year after treatment

The effect of therapeutic ultrasound for the treatment of refractory glaucoma was evaluated in 44 patients by comparing average IOP curves measured before and 3-4 months after treatment. The insonification regime was standardized and the glaucoma medication in each individual patient was unchanged during IOP curve measurements. The average IOP decrease 3-4 months after insonification was 42.2% +/- SD 31.9. In 23 patients who were followed for at least one year the average IOP 3-4 months after treatment was compared with the average IOP 1 year after treatment. In this group average IOP 3-4 months after treatment was 25.3 mmHg +/- SD 16.4 and average IOP 1 year after treatment was 24.1 mmHg +/- SD 15.9. The correlation coefficient between IOP 3-4 months after treatment and IOP 1 year after treatment was 0.79 (P < 0.0001).

Noncontact thermal mode Nd:YAG laser transscleral cyclocoagulation in the treatment of glaucoma. Intermediate follow-up

Noncontact transscleral Nd:YAG laser thermal mode cyclocoagulation is known to reduce intraocular pressure (IOP). Thirty-five eyes were treated at a mean of 2.5 Joules and followed for a mean of 28 months. The mean preoperative IOP of 39.8 mmHg (standard deviation, 11.7) was consistently decreased by 45% to 55% over the follow-up period (standard deviation, 19.9 to 30.8), along with a significant reduction of medical therapy. This effect is comparable with that obtained by investigators using much higher energy levels. Successful control was defined as IOP between 5 and 21 mmHg for eyes with visual acuity of counting fingers or better, between 5 and 25 mmHg for eyes with hand motions to light perception, and as control of ocular pain for eyes with no light perception; 71% to 75% of the eyes were successfully controlled for up to 3 years. The use of lower energy levels appears to be associated with a lower incidence of vision loss and, therefore, merits further controlled investigation.

The glaucomas in aphakia and pseudophakia

Intraocular pressure may become temporarily or permanently elevated at various intervals following cataract surgery. There are several mechanisms by which glaucoma develops as a complication of the cataract extraction itself. The presence of a pseudophakos may or may not contribute to the pathogenesis. Important diagnostic clues include the anterior chamber depth, the presence or absence of an iridectomy, gonioscopic findings, and the appearance of the optic nerve head. Life-long medical treatment is frequently justified, as alternative laser or surgical modalities may not be successful. The exact causes for high failure of filtration surgery in aphakic eyes is not clearly understood; scarring of the conjunctiva, the vitreous, and altered characteristics of the aqueous humor have all been incriminated. Current research to improve surgical success includes the development of effective artificial drainage implants or the use of pharmacologic modulators of wound healing, which promote filtration by preventing scar formation.