Operating microscope offers 'lightless cataract surgery'

London-A new operating microscope for cataract surgery that uses near-infrared light to illuminate the surgical field offers several advantages compared with the conventional microscope, including possible faster visual recovery and the potential to avoid phototoxic retinopathy.

Bong-Hyun Kim, MD, affiliated with Hen-Am Kim Eye Center, Jeon-Nam, South Korea, described the new near-infrared operation microscope (NIOM) that he developed and reported on the clinical results of 70 eyes treated with this device. He spoke at the XXIV Congress of the European Society of Cataract and Refractive Surgeons in London.

By utilizing near-infrared light with a wavelength range from 850 to 1,300 nm, cataract surgeons can avoid bleaching the retina with visible light. This can lead to greater patient satisfaction with faster visual recovery postoperatively and potential prevention of phototoxic retinopathy, Dr. Kim explained.

The NIOM system has numerous components: an operation microscope, a filter mount, a camera mount, video distribution amplifiers, head-mounted displays, and a recording system. The energy from a regular 100-W halogen lamp is filtered to the near-infrared wavelength greater than 850 nm to illuminate the surgical field. Then an image of the patient's eye is converted to electrical signals in the stereoscopic camera mount. Both right and left image signals are sent to the video distribution amplifiers, which send the stereoscopic images to the head-mounted displays, Dr. Kim noted.

He demonstrated what the eye looks like using the NIOM system under fluorescent ambient lighting. A brown iris will appear to be bluish purple, a yellow cataract will be transparent blue, and the red reflex is blue.

Lightless cataract surgery

"With the NIOM system, I can do cataract surgery without any illumination, so I refer to this technique as 'lightless cataract surgery.' I even can perform cataract surgery with the fluorescent ambient lighting in the OR turned off," Dr. Kim said. "The color image resolution of the SVGA 800 2 600 is 1.44 million pixels, which is sufficient to perform all steps during cataract surgery."

In a study of 70 eyes that underwent cataract surgery with this new device, Dr. Kim reported on the main outcome mea- sures: uncorrected visual acuity (UCVA) at different time points postoperatively, duration of the operation, phaco time, fundus examination findings, and complications. There were 24 men and 46 women, with a mean age of 69.4 ± 6.2 years.

The UCVA improved from nine patients (13%) seeing between 20/20 and 20/40 preoperatively to 22 patients (31%) in this range immediately postoperatively. At 1 hour postoperatively, 26 patients (37%) could see in that range. "Mean UCVA improved from 0.7 logMAR preoperatively to 0.4 logMAR at 1 hour postoperatively," he said.

The mean operating time was 11.4 ± 2.0 min and the mean phaco time was 22.9 ± 13.9 sec. As far as complications, there was one posterior capsule rupture (1.4%) and two eyes had iris damage (2.9%). There was no apparent phototoxic retinopathy, he said.