On Demand Perimetry

In a busy clinic, success largely depends on maintaining an efficient workflow. The more efficient we can be, the more patients we can help and the better experience we can provide to those patients. One of the keys to our successful workflow is how we integrate state-of-the-art diagnostic technologies that not only help us to detect disease but that also do so quickly enough to minimize or completely avoid patient bottlenecks.

One of those technologies is the Smartfield (Oculus, Figure 1), a compact visual field device used to detect and monitor functional impairment in glaucoma. Specifically, the Smartfield can be used to perform standard automated perimetry of the central visual field and beyond. It has been a comprehensive clinical solution for visual field testing in our practice.

DEVICE DESIGN AND PATIENT COMFORT

Patient comfort is extremely important to us. The Oculus Smartfield is designed for the patient to lean in and rest up against a head rest (Figure 2). Compared with the Humphrey Visual Field Analyzer (Carl Zeiss Meditec), another perimeter we use at our clinic, patients are more comfortable positioned at the Smartfield. In a recent comparison of these two devices with 20 of our patients, 100% preferred the comfort of the Smartfield.

Not only was it more comfortable for them, but it was faster for us. The Smartfield has a unique distance target from the majority of perimeters that test with a near target. In our practice, we found that 33% fewer patients needed a trial lens during testing compared to the Humphrey visual field. The device has a height-adjustable double chin rest and measuring head, helping us to better position patients in a short amount of time. Further, the Oculus Smartfield’s translucent lateral eye shields mean that our patients no longer need to use an eye patch during the examination. This is another time-saver in the clinic.

The Smartfield’s lenses are also very stable. When they are hooked in, they do not move and they do not touch the patient. With other systems, patients often will move away from or bump the lenses, causing a ring scotoma. This can produce inaccurate results, often leading us to ask the patient to return another day for repeat testing.

The wide fixation spot on the Smartfield is also helpful, again avoiding the need for any unwanted repeats of the test. The device can truly capture the visual field measurements unless the patient is looking away. A patented fixation control algorithm and a high-resolution video camera monitor the eye, and measurement results are summarized in a standard printout. Because it is connected to an external computer on our clinic’s data network, we can also access examination data from any computer within the clinic.

FUNCTIONS

As mentioned previously, the Oculus Smartfield is used for visual field testing and includes the following set of predefined programs: SPARK, Glaucoma Staging System 2 (GSS-2), Glaucoma Staging Program (GSP), Threshold Noiseless Trend (TNT), and Predicting Anatomy from Thresholds (PATH).

SPARK. Based on data from more than 90,000 perimetric findings, SPARK allows us to quickly and precisely measure thresholds in the central visual field. In our practice, this translates to faster and more stable threshold measurements in glaucoma patients. We use the 30 x 24 grid for the central visual field; other commonly used patterns are 24-2 and 10-2, and custom patterns can also be created if desired.

Glaucoma Staging System 2. Visual field defects are classified based on the mean deviation and the pattern standard deviation of the perimetric values. The GSS2 chart displays defined areas for the different stages (0–5) of glaucomatous disease and separates generalized, localized, and mixed defects.

Glaucoma Staging Program. The GSP, based on pattern recognition, is helpful for the early detection of glaucoma, and the color-coded results are easy to follow and read. It places examination findings into visual field classes based on their appearance (normal, glaucomatous, artifactual, and neuro) and classifies them into normal, suspect, pre-perimetric, early stage, moderate, and severe using an intuitive green, yellow, and red color-coding system.

The GSP detects subtle changes in a patient’s visual field that are associated with early-stage glaucoma, but its greatest benefit to us lies in its capacity to detect suspect and pre-perimetric glaucoma, which are often not easily seen by the examiner. The Glaucoma Likelihood Index summarizes the results of the GSP classification into a single parameter presenting a value between 0 (normal) and 5 (severe glaucoma).

Threshold Noiseless Trend. The TNT progression analysis provides us with a greater sensitivity in detecting glaucoma progression in the early stages of the disease. It uses all visual field results taken over a patient’s history to create a concise progression analysis report. It also helps us to differentiate between diffuse and focal glaucomatous progression.

Predicting Anatomy from Thresholds. PATH’s estimate of the retinal nerve fiber layer thickness around the optic nerve head and the relative area of the neuroretinal rim is based on SPARK’s visual field measurements.

CASE EXAMPLE

In a clinic setting, a few minutes makes a big difference in workflow. What we like most about the Oculus Smartfield is that it gives us the ability to perform “on demand” testing of our glaucoma, glaucoma-suspect, or neurological field loss patients. Compared with the Humphrey Visual Field Analyzer, the Smartfield takes less than half the time in most cases. In younger patients (20–40 years of age), there is about a 1- to 2-minute difference between the devices, and in older patients or harder cases, that time difference is more like 4 to 5 minutes.

As an example, recently a new patient presented as a strong glaucoma suspect. Because he reported having a visual field test performed by another provider in the past, we ordered a 24-2 visual field on the Humphrey Visual Field Analyzer. The visual field setup and patient instruction set took about 5 minutes. On the patient’s right eye, the test took 4 minutes and 31 seconds; on his left eye, it took 8 minutes and 23 seconds. Based on mediocre reliability, we repeated the measurement in the patient’s left eye, which took an additional 6 minutes and 35 seconds to perform. The total time with the Humphrey was about 24 minutes. Because the test results were questionable, we performed the same test with the Oculus Smartfield. Setup and explanation took 2 minutes, and measurements in each eye took 3 minutes. The total time devoted to the Smartfield test was less than 10 minutes.

The 14-minute test time differential between the Humphrey Field Analyzer and the Oculus Smartfield, paired with the added ease of test-taking for the patient, represents exactly why we’ve made the Smartfield our go-to instrument when evaluating visual field loss.

CONCLUSION

The time required of each visual field testing device is significantly different, and the fact that we can perform a visual field so efficiently and so quickly with the Oculus Smartfield is a game-changer. Before the Smartfield, we scheduled patients to come back another day to review the results and discuss future treatment. With the Smartfield, now we can do on demand, same-day visual field and analysis, which has improved not only our workflow but also our patients’ experience.