Innovations in visual field technology aim for speed, convenience, accuracy

Although perimetry has not undergone dramatic changes in the past year, manufacturers have been striving to enhance existing instruments. The latest refinements to visual field testing software are aimed at shortening test time and interpreting results.

“It’s easy to do something quickly and badly,” said Vincent Michael Patella, OD, vice president of clinical affairs for the Humphrey division of Carl Zeiss Ophthalmic Instrument Systems Inc. “The trick is to do something quickly and well.”

As manufacturers seek to improve upon the pacing and convenience of visual field testing, they also must maintain the quality and accuracy of traditional testing.

A new Octopus perimeter

---Haag-Streit: A 170° rotatable headrest allows the Octopus 301 to position itself in such a way that a technician is not needed on both sides of it. The unit also features a touch screen monitor to establish the settings and test parameters, which also is used for data input.

Haag-Streit USA launched a new perimeter this year: the Octopus 301 went on the market at the beginning of August.

According to national sales manager Irwin Kronenberg, the Octopus 301 is a new, improved version of the Octopus 1-2-3, which has been on the market for 12 years. “The 301 is the new, reinvented, redesigned version of our 1-2-3,” Mr. Kronenberg said. “Technology-wise, it is upgraded from the 1-2-3, with a few advances in the technology side, the computerization and the storage of tests.”

A major difference between the two perimeters is in the design and aesthetics, Mr. Kronenberg said. “The design has dramatically changed,” he said. “The functions and features of aligning the patient are all new. Just the look of it alone has really made the phones ring.”

Among the changes in design is a 170° rotatable headrest, which allows the unit to position itself in such a way that a technician is not needed on both sides of it. Also, the Octopus 301 features a touch screen monitor to establish the settings and test parameters. The touch screen also is used for data input, Mr. Kronenberg said.

Compared to the Octopus 1-2-3, the Octopus 301 has a larger capacity for test storage, and the computer components will be expandable in the future for additional capability.

“We have the Octopus 311 coming out right behind it,” Mr. Kronenberg said. “That will probably be introduced during the fourth quarter of the year. The 311 will allow us to do blue-yellow color testing.”

The Octopus 301 will also feature a motorized fixation adjustment, with internal motors that adjust the patient automatically. The instrument is also more lightweight, Mr. Kronenberg added. “It’s more user-friendly,” he said. “The way the patient is aligned and monitored and the way the data are entered makes it easier to use. It’s also more comfortable for the patient.”

Welch Allyn’s Test Enhancement Package

---Welch Allyn/Zeiss Humphrey: The Frequency Doubling Device has 17 10° square targets, which go out 20° in the visual field. The new N-30 screening feature in the Test Enhancement Package provides an additional 10° in the nasal step.

Welch Allyn Inc., the company that commercialized the patented Frequency Doubling Technology, has now developed a Test Enhancement Package to improve the current instrument. Launched more than 3 years ago, the Frequency Doubling Device is sold through Zeiss Humphrey as the Humphrey FDT Visual Field Instrument.

“It’s still a fairly new device, and it is probably the most recent new technology in visual field testing in decades,” said Rick Farchione, senior product manager for Ophthalmic Products at Welch Allyn. “It is an ideal screening instrument, although it does offer thresholding capabilities as well.”

Mr. Farchione said the frequency doubling technology isolates a subset of retinal ganglion cell mechanisms in the magnocellular (M-cell) pathway, specifically the M_y cells. “Because it is a subset of the overall retinal ganglion cells, there are fewer of them to compensate for damaged cells,” he said. “In addition, it is theorized that these are the first cells damaged in the early stages of glaucoma.”

Mr. Farchione said the Test Enhancement Package will enable the current instrument to run the test 30% faster, with a 35-second screening time. The updated software package will also provide an N-30 screening test, which previously was not available.

Mr. Farchione explained that the Frequently Doubling Device has 17 10° square targets, which go out 20° in the visual field. The new N-30 screening feature provides an additional 10° in the nasal step.

The new Test Enhancement Package will also provide a pattern deviation probability plot on the printout of the results. “This provides a statistical analysis that corrects for generalized or diffuse loss and is displayed in a graph format for easy visualization of potential localized loss,” Mr. Farchione said. “That is another new feature.”

Mr. Farchione said there are thousands of instruments currently being used that could be equipped with the Test Enhancement Package. “There are doctors out there who would love to increase their speed, provide an additional 30° screening test and provide a pattern deviation plot of the printout,” Mr. Farchione said. “It is also exceptionally easy to use.”

Paradigm/Dicon’s Hybrid Threshold test

---Paradigm/Dicon: Advanced FieldView’s automated, multiple field display with change analysis.

The latest development in perimetry for Paradigm/Dicon is the Hybrid Threshold (HT) test, which was introduced 2 years ago and has steadily gained acceptance as a follow-up glaucoma test. According to senior product manager Ron Banfiel, the 54-point exam provides 33% better coverage in the arcuate area of the field, where early field loss occurs.

“The HT test arranges the points somewhat differently than a 24-2, which is also a 54-point field,” Mr. Banfiel said. “It is designed to be a shorter exam.”

Mr. Banfiel said the HT test is intended for the follow-up of glaucoma patients. “Obviously, these patients go through these exams over and over again,” Mr. Banfiel said. “So having a shorter alternative is nice for the patients.”

Another new exam that is now standard on the Paradigm/Dicon instrument is Exam #7. “This is a radial pattern, as opposed to a grid like the 30-2, which we also have on our instrument,” Mr. Banfiel said. “It has 50% better coverage in the arcuate area where field loss is most likely to occur in glaucoma.”

Mr. Banfiel said, in Exam #7, the points are arranged in a radial pattern and have an appearance similar to concentric rings.

“Of course, that follows the structure of the nerve fiber in the eye, which is arc-shaped,” he said. “And instead of doing the uniform grid where every point is arranged in boxes, we are able to put denser point patterns in critical areas and spread them out a little further in areas that aren’t quite as important.”

In addition, Paradigm/Dicon also has an update in visual field analysis, called the Advanced Field View. The Windows-based field view emphasizes analysis of changes in fields over time, Mr. Banfiel said.

“You simply open the patient record, and all of the fields are displayed automatically, with a summary display showing the change in those fields over time,” Mr. Banfiel said. “We’ve built into the software the ability to handle large numbers of fields, and not just show them to you in series, but actually show you numerically.”

The Advanced Field View can also be printed out as a color report, Mr. Banfiel said. “That’s another nice feature – it supports color reports, so the doctor can have that for the chart record,” he said. “It saves time in terms of reanalyzing each time you do a new field on a patient.”

The HT test and Exam #7 both boot off of a floppy disk, Mr. Banfiel said. Customers receive this update in the form of a floppy disk through the mail.

“In glaucoma testing right now, there is an emphasis on earlier detection and methodology,” Mr. Banfiel said. “We’re dealing with these issues by focusing on discovering problems and monitoring them long-term.”

Synemed’s Combination Test Strategy

---Synemed: The Combination Test Strategy software is available on all of Synemed's current EP-900 Series of perimeters. The EP-900 has the capacity to screen in less than 1 minute and threshold in less than 2 minutes.

Within the past year, Synemed has introduced a combination screening and threshold testing program, the Combination Test Strategy.

“This enables doctors to get information on both what’s going on in the central 30°, where the threshold is most effective, and in the periphery, where screening is typically the most effective,” said Steve Dault, sales manager for Synemed. “It saves a lot of time by combining those two into one simple test.”

The Combination Test Strategy software is available on all of Synemed’s current EP-900 Series of perimeters.

The EP-900 has the capacity to screen in less than 1 minute and threshold in less than 2 minutes. “Most of the instruments today do both screening tests and threshold tests, but they are different programs,” Mr. Dault said. “This is a strategy that does both screening and threshold at once.”

Synemed also has a new development that links its perimetry and digital imaging systems, Mr. Dault said. “It interfaces with our EyeScape digital imaging software,” Mr. Dault said. “We can pull over the results from the visual field instrument and store them with retinal photos and slit lamp photos that have been taken with our imaging system.”

This tool, which was launched roughly 1 month ago, can be used with “any device that is going to give you some type of visual image on the computer screen,” Mr. Dault said.

“It provides serial analysis and a centralized database,” Mr. Dault said. “It’s a very useful tool.”

SITA: an ongoing transition

Zeiss Humphrey began equipping its perimeters with Swedish Interactive Testing Algorithm (SITA) several years ago, and its large installed base of customers continue to make the transition from the old technology to the new.

“The next thing that’s new is making it easy for the world to shift from the old Humphrey way of doing things to the quicker way,” Dr. Patella said. “We are helping doctors manage patients while they are making that transition, and we are giving them tools for easing that process.”

One crucial part of the transitional process, Dr. Patella said, is comparing data from the old system to the new.

“The range of normal with SITA is different from the old strategy,” Dr. Patella said. “Variability has gotten smaller and the range of normal has become tighter. Doctors need to realize that they should not compare the old data with the new data simply by looking at raw measurements.”

Dr. Patella said Humphrey is in the process of producing a tool that formalizes the data comparison. The product is currently in clinical trials in Europe, he said. “It actually quantifies and compares the old data with the new,” he said. “It provides a tool for switching over.”

The Oculus Easyfield

---Oculus: The radius bowl is adjustable to the height of the patient. In addition, the Easyfield has a 7-inch console, which stores 40,000 exams.

Oculus Inc. USA (Woodinville, Wash.) introduced its newest perimeter, the Easyfield, in July 2000. The instrument, which weighs less than 12 pounds, incorporates a variety of new features.

“For a small perimeter, it has many features,” said Tom Weatherby, president of Oculus Inc. USA. Mr. Weatherby said the Easyfield provides the popular grids of 30-2, 24-2 and 10-2. He said it has a 30-centimeter radius bowl and 10-candela background luminous, both of which are Goldmann standards. Rather than having a rear projection arm with light bulbs, the Easyfield uses diodes.

“This means there are no moving parts and no light bulbs to change,” he said. “Another advantage is that the patient doesn’t hear the sound of the arm moving.”

The radius bowl is adjustable to the height of the patient, Mr. Weatherby said. In addition, the Easyfield has a 7-inch console, which stores 40,000 exams. It also features an LCD color screen, as well as a CCD camera in the bowl.

“So, during the exam, one can look at the control box, see the patient’s eye and provide instructions on adjusting his or her gaze,” he said.

The Easyfield also has a statistics package, through which practitioners can compare the patient’s results with a ‘normal’ group of patients, or with their own previous exams.

The perimeter has standard display, relative display, 3-D display and gray scale display as well as a probability display, Mr. Weatherby said. It also features Standard Pattern Deviation and Reliability Factor. “Reliability Factor combines the results of the fixation monitoring and the patient’s false positive responses,” Mr. Weatherby said. “It determines whether the test results were favorable or not.”

Refining existing products

Overall, 2001 has not seen many major developments in perimetry, manufacturers said. “There’s not a whole lot new and exciting in perimetry,” Mr. Dault said. “Primarily, we have been updating software and making the tests more convenient.”

Dr. Patella agreed that major changes in perimetry are often a long time in the making. “The most important changes for us have not been in the past year,” he said. “Often, it takes years for an idea to penetrate.”

For Your Information:

• Vincent Michael Patella, OD, is vice president of clinical affairs for the Humphrey division of Carl Zeiss Ophthalmic Instrument Systems Inc. He can be reached at 5160 Hacienda Dr., Dublin, CA 94568; (925) 557-4544; fax: (925) 557-4182.
• Irwin Kronenberg is national sales manager for Haag-Streit USA. He can be reached at 3535 Kings Mills Rd., Mason, OH 45040; (800) 735-0357; fax: (513) 336-7260.
• Rick Farchione is senior product manager for Ophthalmic Products for Welch Allyn Inc. He can be reached at 4341 State Street Rd., Skaneateles Falls, NY 13153; (315) 685-4429; fax: (315) 685-2546.
• Ron Banfiel is senior product manager for Paradigm/Dicon. He can be reached at 10373 Roselle St., San Diego, CA 92121; (520) 214-0785; fax: (520) 214-0787.
• Steve Dault is sales manager for Synemed. He can be reached at 4562 E. Second St., Benicia, CA 94510; (707) 745-8386 or (800) 777-0650; fax: (972) 422-4430; Web site: www.synemed.com.
• Tom Weatherby is President of Oculus Inc., USA. He can be reached at PO Box 1007; Woodinville, WA 98072-1007; (888) 284.8004; fax: (425) 867-1881.