HEP could be important in diagnosis and monitoring of glaucoma

Heidelberg edge perimetry (HEP) may have role in the early detection and assessment of functional damage cause by glaucoma, according to the authors of a case report presented on-line at PubMed via Case Reports in Ophthalmology. Further, HEP testing may potentially have advantages over standard automated perimetry (SAP), currently the gold standard for visual function testing.

This case report is of a 46-year-old male who presents with raised IOP 27 mmHg (OD) and 24 mmHg (OS), but healthy optic discs and normal standard automated perimetry (SAP). Sixteen years after a diagnosis of ocular hypertension, he has developed glaucomatous changes to the right optic disc and inferior retinal nerve fibre layer (RNFL) thinning. IOPs increased to 40 mmHg OD and 30 mmHg OS. Structural abnormality of his right eye was found with spectral-domain optical coherence tomography (SD-OCT).

Functional testing with SAP repeatedly came up normal, despite the evidence of progressive structural damage. HEP testing, however, showed extensive superior visual field damage corresponding to the structural changes, and the HEP indices of Glaucoma Hemifield Test-in sharp contrast to those of the SAP-were all outside normal limits. In addition, HEP revealed an extensive defect, with a marked nasal and superior paracentral scotoma, that had excellent spatial correlation with the defect observed on optic disc photographs and SD-OCT.

HEP uses a flicker-defined form (FDF) stimulus with the goal of detecting glaucomatous functional damage earlier. Using a temporally driven illusion of an array of randomly positioned black and white dots that flicker at high temporal frequency in counterphase and reverse polarity without changing position, FDF perimetry creates an illusory circular edge contour thought to stimulate the magnocellular pathway. In turn, the magnocellular pathway is thought to sustain damage in the early stages of glaucoma.

"HEP may have the potential to become an important component of our armamentarium for the diagnosis and monitoring of glaucoma; however, prospective longitudinal studies are required to fully validate this technology," concluded the authors.

To view this case report, click here.