HP provides advantage in management of AMD

Preferential hyperacuity perimetry (PHP; Foresee PHP, Notal Vision/ MSS) is innovative diagnostic technology uniquely able to detect the progression of age-related macular degeneration (AMD) from the intermediate stage to neovascular disease, according to Michael Elman, MD.

"For years we have been looking for tests to identify patients at high risk of vision loss from AMD, and with PHP we have found the 'Holy Grail.' It has been validated in multicenter clinical trials and shown to surpass the Amsler grid by far in its specificity and sensitivity for detecting early progression to neovascular AMD," said Dr. Elman, a retinal specialist in Baltimore.

"The ability to make that diagnosis early, even before the patient becomes symptomatic, has important benefits for identifying individuals who require more careful follow-up and who may be excellent candidates for anti-VEGF therapy," Dr. Elman said. "Considering that the new pharmacologic options for treating neovascular AMD are most beneficial when administered early, while vision is still good and lesions are small, PHP has particular value for improving our chances of minimizing AMD-related vision loss and restoring excellent vision."

PHP is a form of macular perimetry based on hyperacuity (Vernier acuity), which is the ability to detect visually the misalignment of objects relative to others in space. To perform the test, the patient sits in front of a monitor where a series of "dot deviation signals" appears on the screen. Each signal is displayed for 160 milliseconds and is made up of several closely spaced dots arranged in a straight line with the exception of one dot that is out of alignment. Patients use a stylus to touch the screen at the site they perceive to be the most prominent distortion in the line. Patients with AMD who have developed a retinal pigment epithelium elevation will perceive distortions incorrectly and preferentially touch the stylus to that location.

"The test procedure is like playing a video game and has good patient acceptance because it is relatively short and easy to perform," Dr. Elman said.

During a 3- to 5-minute test, 500 retinal data points are measured covering the central 14° of the visual field. When a patient's response identifies a distortion that is not present on the screen, the software adjusts the presentation of the dot deviation signals to gather more information about the relevant area of the visual field. The diagnosis of neovascular AMD is based on analysis of the patient's visual field defect intensity relative to the normative database. The report that is generated indicates the relative location of the defects in the macular area.

Dr. Elman suggested that ideally, patients with non-exudative AMD might undergo quarterly PHP testing. Unfortunately, payers, including Medicare, do not uniformly pay for the examination, he noted.

"As with many other new technologies, payers have been slow to embrace PHP," Dr. Elman said, providing his perspective on reimbursement for PHP in his area. "In Maryland, PHP is not covered by Medicare. I hope this situation will change as a result of ongoing efforts to educate Medicare and other payers about the utility of PHP for identifying high-risk patients and its potential for saving costs and restoring vision over the longer term."

"Technology generally precedes the payment policies of Medicare and other third-party payers," said Kevin Corcoran, president of Corcoran Consulting Group, and a nationally recognized expert on reimbursement in ophthalmology. "Medicare carriers differ on coverage policy of perimetry for dry AMD. In one-third of the states, repeated testing with PHP is fully reimbursed. In one-third of the states, PHP is not covered at all. The remaining states cover initial testing with PHP but restrict coverage for repeated testing." Corcoran opined that the trend is favorable, and he expects more payers to recognize the value of this test for early recognition of conversion from dry AMD to wet AMD.