Article Date: 2/1/2007

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The Foresight of Foresee PHP
This device enables you to detect early wet AMD.

Age-related macular degeneration (AMD) affects more than 1.75 million people in the United States, and this number will increase to almost three million by 2020, due to the rapid aging of the U.S. population.1 But, if you detect wet, or subfoveal exudative AMD early, you can prevent irreversible vision loss in these patients. This is the purpose of the Foresee PHP (Preferential Hyperacuity Perimeter), from Notal Vision and MSS.

This clinically validated diagnostic device has FDA clearance for monitoring the progression of AMD and detecting the conversion from "dry" to "wet" AMD signaled by the onset of CNV. It's a second-generation device that offers a number of improvements to the first-generation Preview PHP, that the company says makes AMD monitoring and report interpretation quicker and easier.

PHP perlustration

The device generates a non-invasive eye exam that allows you to identify elevations in the patient's retinal pigment epithelium (RPE) and the bowing of the photoreceptor layer — both consistent with conversion from an intermediate to an advanced AMD stage, or "wet" AMD.

This eye exam is based on Vernier acuity, also known as hyperacuity, or the ability to perceive small differences in the spatial relationships of two objects. Vernier acuity is ten times more sensitive than standard visual acuity.2 Through its use of hyperacuity, the Foresee PHP can overcome the brain's ability to compensate for small visual field defects and may identify CNV lesions prior to the patient experiencing any significant vision loss.

PHP on patients

To use the Foresee PHP, place the patient in front of the device's monitor, and hand him the instrument's stylus pen. Now, tell the patient to touch the screen with the pen on dots that appear "out of place" in a series of dotted lines that will flash quickly on the screen.

The fast flash time and use of vernier acuity allow the device to overcome brain compensation mechanisms to better capture visual defects. By analyzing the patient's responses to the "dot devi- ation signals," the Foresee PHP detects CNV-related distortions within the patient's central 14° visual field.

The device can determine abnormalities that may indicate photoreceptor layer and RPE elevation by using a phe

nomenon called "preferential looking," in which the patient's attention is always drawn to the largest distortion he sees. So, if a visual defect causes the patient to see a bend in the line that appears greater than the one presented by the test instrument, the patient selects the larger physiological distortion. The dot deviation signals show differing magnitudes and locations of distortions to measure the extent and location of CNV lesions.

Foresee features

The Foresee PHP generates an advanced report based on a normative database. This database features reliability indices and a visual field map to indicate the relative location of abnormalities in the patient's macular area.

Also, the device now contains a chin rest as well as a resting pad for the patient's hand. This pad also acts as the driver of the test, which is now patient-operated. So, each time the patient touches a dot on the screen, he brings his hand back to rest on the pad, which cues the device to continue with the next dotted-line flash. Efficiency comes in the form of technician time saved due to patient self-operation of the test; additionally, the test time has been reduced, meaning less demand on the patient.

I've used this device to detect CNV on suspected wet AMD patients who currently have intermediate AMD, and I've been involved in several clinical cases in which it successfully predicted a patient's conversion from dry to wet AMD. The bottom line: By having the patient use the Foresee PHP, you have an excellent chance of catching CNV early in its development, allowing for early intervention and therefore, the preservation of the patient's vision — a very useful weapon in our fight against this devastating disease.

1. Friedman DS, O'Colmain BJ, Munoz B, et al. Prevalence of age-related macular degeneration in the United States. Arch Ophthalmol. 2004 Apr;122(4):564-72.
2. Enoch JM, Williams RA, Essock EA, Barricks M. Hyperacuity perimetry. assessment of macular function through ocular opacities. Arch Ophthalmol. 1984 Aug;102(8):1164-8.

Optometric Management, Issue: February 2007