ULTRASOUND CYCLOPLASTY IN EYES WITH GLAUCOMA

Guest author

Malik Nuzhat

Ajmal Khan Tibbiya College

Aligarh, India

INTRODUCTION

Over the last few years a new device named "Ultrasound Cycloplasty" (UCP) has been developed. This device uses high-intensity focused ultrasound (HIFU).

The main purpose of this device is to overcome the limitations of traditional cyclodestructive technique by achieving a more selective coagulation of the ciliary body and avoiding possible damage to the adjacent Ocular structures.

In addition the stimulation of supra-choroidal and trans-scleral portions of the uveoscleral outflow pathway has recently been proposed as possible adjunctive mechanisms in reducing intra-ocular pressure (IOP).

PREOPERATIVE PROCEDURE AND OPHTHALMOLOGICAL EXAMINATION

A.

1. Test distance and near best corrected visual acuity.

2. Evaluate the Anterior segment of the eye using a slit-lamp biomicroscope.

3. Examine the anterior chamber angle using a goniolens.

4. Evaluate the fundus by slit-lamp indirect ophthalmoscopy with the use of a non-contact fundus lens.

5. Measure the IOP using Goldmann applanation tonometry.

Measure the ocular anatomical parameters by means of a non-contact optical biometer.

B. Pre-surgical procedures

1. Place the patient in a supine position on the surgical bed.

2. Administer local anesthesia by performing one peri-bulbar infiltration with 10 ml of local anesthetic (mepivacaine plus ropivacaine), 30 minutes prior to surgery.

3. Perform the injection infero-temporally at the junction of outer 1/3rd and inner 2/3rd of the lower orbital rim or supero-nasally beneath the superior orbital notch using a 27- gauge needle.

C. Preparation of the treatment device

1. Enter data about the surgeon and patient using the control unit touch screen, and then select the eye to treat.

2. Open the sterile single-use device pack containing the coupling cone and the treatment probe and connect their cables to the control unit.

D. UCP procedure

1. Disinfect the palpebral and periorbital skin with 10% povidone iodine 3 times.

2. Wipe the disinfected skin with sterile guaze.

3. Put a sterile surgical drape over the face of the patient with a central hole centered over the eye.

4. Place the patients head lying slightly backwards in order to put the ocular surface horizontal. This allows easy placement of the cone (of the device).

5. Open the eye without using the speculum.

6. Put the coupling cone over the ocular surface with tubing on the temporal side and gently move to correctly position and center it.

7. Push the aspiration button on the foot switch to start a low-level suction from the peripheral ring of the coupling cone until the vertical bar on the screen becomes green. This allows the maintenance of the coupling cone in direct contact with the patients eye throughout the entire procedure.

8. Insert the treatment probe inside the coupling cone, with the cable in nasal position.

9. Fill the empty space delimited by the eye, cone and probe with sterile balanced salt solution (BSS) at room temperature.

10. Ask the patient to hold the position and keep the head perfectly still.

11. Push the start button on the foot switch to start the treatment and hold the pressure during the procedure.

12. Maintain firmly in the optimal position the probe and the coupling cone during the entire procedure. Avoid moving, rotating or pushing the probe.

13. At the end of the procedure deactivate the suction system by pushing the aspiration button on the foot switch.

14. Tilt the cone slightly until BSS is removed through the tube.

E. Post-surgical procedure

1. Instill antibiotic-steroid eyedrops in the treated eye and patch the eye for 24 hours.

2. Remove the eye patch next day and measure the IOP.

3. Prescribe the patient antibiotic-steroid eyedrops, 4 times per day for a month.

4. Examine the treated eye and measure the IOP at day 1, 7 and 14; 1,3 and 6 months; and  after 1 year.

F. Results

In a study 8 patients successfully underwent follow-up for 1 year without need for oral hypotensive agents. 2 patients required incisional surgery for better IOP control.

No major complications were reported in the study, except for 1 case of fixed and dilated pupil with accommodation deficit, which spontaneously resolved 3 months after the UCP procedure.

G. Discussion

1. UCP is a new non-incisional cyclodestructive technique that can lower IOP, acting in 2 different ways.

2. It reduces aqueous humor inflow determining the selective necrosis of secretory epithelium of the ciliary body.

3. It increases aqueous humor outflow through the uveoscleral tract, stimulating the trans-scleral and supra-choroidal pathways.

4. The technique is fast, easy, safe and surgeon friendly.

5. Several technical improvements have been made in UCP technology compared to the previous techniques, providing more precise focusing on the target zone.

6. In particular the probe is placed in direct contact with the eye and the treatment is conducted using the same setting throughout the entire procedure.

7. The higher operating frequency (21 MHz) compared to previous systems (5 MHz) allows centring the target zone while sparing the adjacent tissues.

8. The UCP device is composed of a sterile single-use treatment pack, which comprises a polymer made coupling cone and a treatment probe.

9. The coupling cone and the probe cone are connected by cables to a portable control unit (36x32x26 cm).

10. It permits setting of the treatment parameters and controls the procedure by means of a touch screen.

11. The probe is a ring of 30 mm diameter and 15 mm height. It contains 6 piezoelectric transducers.

12. Each transducer is approximately a cylinder segment of 7.0 mm length, 4.5 mm width and 10.2 mm radius. The total surface area is 35 mm2. 

13. Depending upon the diameter the 6 piezoelectric elements are centred on 11 mm, 12 mm or 13 mm diameter circle over the circumference of the eye. The ultrasound beams are focused 2 mm deep to the sclera.

14. The 6 transducers deliver Ultrasound operating at a frequency of 21 MHz with an acoustic power of 2 W, determining the rapid increase of local temperature of the ciliary body upto 90'C.