July 01, 2004
4 min read

New NAVEX software used to treat highly aberrated eyes

LASIK system combines aberrometry, topography, autorefraction with single measurement.

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Software upgrades on the Nidek Advanced Vision Excimer laser system will allow surgeons to treat both corneal and internal aberrations, making it ideal for highly aberrated eyes, according to a surgeon who has worked with the technology outside the United States.

The Nidek Advanced Vision Excimer (NAVEX) system is the first platform to calculate aberrometry, topography and autorefraction with a single exam, according to Nidek, and uses these three measurements to create a customized power map and treatment.

According to Paul J. Dougherty, MD, Nidek plans to submit the customized ablation system for Food and Drug Administration approval in the near future; it is currently available in Asia, Europe, South America, Canada and Mexico.

The NAVEX system combines three integrated components: the Optical Path Difference (OPD) Scan, the Final Fit software and the Nidek EC-5000 CX2 laser.

Unique software

Unlike other refractive diagnostic systems, the OPD-Scan uses time-based aberrometry to send 1,440 points of infrared light into the eye and measures the length of time until they return, according to Dr. Dougherty. Traditional Shack-Hartmann aberrometry tracks the positional displacement of only 200 points of visible light sent into the eye.

Currently available modalities, therefore, “have a lot of difficulty with highly aberrated eyes, or getting any scan with highly aberrated eyes,” Dr. Dougherty said. “[The NAVEX system provides] better data because we’re not only treating aberrometry, we’re also treating topography.”

The Final Fit software interfaces with both the OPD-Scan and the laser to analyze the power and wavefront map and creates a custom treatment algorithm for each patient.

“Final Fit breaks the treatment down into a spherical component, a cylinder component and an irregularity component,” Dr. Dougherty said. “And with the Final Fit software you can specify … that it treat only the irregularity component, because in highly aberrated eyes, often any refractive error you find is directly related to irregularity as opposed to true sphere and cylinder.”

Change in wavefront RMS values preop to postop

Source: Dougherty PJ and Nidek

Several options

Surgeons can select one of three software options with the NAVEX system. For primary eyes and enhancements, OATz (Optimized Aspheric Treatment Zone) is a topography-based treatment that maintains corneal asphericity and allows for large optical zones. Dr. Dougherty described the OATz mode as an ablation profile that decreases aberrations at the level of the transition zone.

Highly aberrated eyes, meanwhile, might benefit from CATz (Customized Aspheric Treatment Zone) mode or OPDCAT mode, the newest software option, he said.

While CATz treats corneal aberrations, OPDCAT treats both corneal and internal higher-order aberrations, according to Dr. Dougherty. “It gives a true aspheric optical zone and transition zone, and ultimately this software will be able to treat both primary and highly aberrated eyes,” he said.

Case study

Dr. Dougherty recalled the case of a male patient in his 50s who had a deep keratectomy due to a previous keratome malfunction. The incision required suturing two times.

The patient had undergone two PRKs with mitomycin but was left with significant astigmatism and best corrected visual acuity of 20/40. He also had significant horizontal coma in the area of the keratectomy, Dr. Dougherty said.

“The current aberrometry-based treatments I don’t think would have given me the results that I wanted,” he said. He instead referred the patient out of the country for treatment with the NAVEX system.

One month after undergoing CATz PRK with mitomycin, the patient had improved to 20/25 uncorrected vision with significantly improved topography, Dr. Dougherty reported.

“One of the great things about the Nidek laser – and I kind of look at the Nidek laser as a Ferrari as opposed to a Chevrolet – is that you can adjust so many of the treatment parameters for the patient,” he said. “So with the Final Fit software, you can specifically change optical zones and transition zones.”

Nidek’s Final Fit software shows the preoperative and expected NAVEX CATz postoperative topographies of the deep keratectomy patient (top), as well as the planned CATz irregularity treatment of the same patient (bottom).

All images courtesy of Paul J. Dougherty, MD.

Ease of use

The laser itself is also easy to use, Dr. Dougherty said.

The EC-5000 CX2 has a 200 Hz video-based active and passive tracker with a cyclotorsion module to detect torsion errors, he said. “One of the great things about this tracker is that there’s no dilation required, and you can basically move instruments through the field without having to reset the tracker.”

Study results

In a study of 132 eyes in Mexico and Canada, 99% of patients achieved within 1 D of intended refraction, and 92% within 0.5 D, he said.

“What’s great about this study, unlike some of the other FDA studies, is that there’s been no preselection of patients,” Dr. Dougherty said. “So this study is more indicative of what LASIK would be in a typical refractive center.”

Patients were treated for up to –8.25 D of sphere and 3 D of cylinder. All patients achieved at least 20/40 vision within 1 month, and 85% achieved at least 20/20. In addition, 27% of patients had visual acuity of 20/15 or better at month 1.

In terms of BCVA, 37% of patients gained one or more lines and no patients lost more than one line. Dr. Dougherty noted that 8.5% of patients lost one line of vision, but there were no other significant complications.

Higher spherical, coma and trefoil aberrations also decreased on average, he said.

Preop PRK Orbscan of the same NAVEX CATz patient.

PRK Orbscan 1 month postop.

For Your Information:
  • Paul J. Dougherty, MD, can be reached at 1821 Daily Drive, Camarillo, CA 93010; (805) 987-5300; fax: (805) 987-5330; e-mail: info@doughertylaservision.com. Dr. Dougherty is a paid consultant for Nidek Technologies, Ltd.
  • Nidek, manufacturers of the NAVEX laser system, can be reached at 47651 Westinghouse Dr., Fremont, CA 94539-7474; e-mail: contact@nidek.co.jp; Web site: www.nidek.com.