Structure and Function in Normal versus High Tension Glaucoma

Abstract

Abstract: : Purpose: To compare the optic disc topography and visual field results obtained from patients with either normal tension glaucoma (NTG) or high tension glaucoma (HTG) using multifocal visual evoked potentials (mfVEP), achromatic automated perimetry (AAP), and confocal scanning laser ophthalmoscopy. Methods: Nineteen patients with NTG and 16 with HTG were studied. All patients had reliable Humphrey visual fields (HVF) with a mean deviation equal to or better than 10 dB in both eyes, and glaucomatous damage in at least one eye, as defined by a glaucomatous optic disc and an abnormal HVF (PSD and/or GHT). Monocular mfVEPs were obtained from each eye using a pattern–reversal dartboard array. The mfVEPs were obtained using VERIS (EDI), three channels of recording, the responses were analyzed with custom software and monocular probability plots were derived [1–3]. If both eyes qualified, one eye was selected at random. Both hemifields were separated into a central 10 degree (radius) area and an outer arcuate area. The mfVEP and HVF probability plots within each area were defined as abnormal based on cluster criteria [2]. Optic nerve head images were obtained with the confocal scanning laser ophthalmoscope and divided into 6 sectors. Sectors were defined as abnormal compared to a normative database using Moorfields regression analysis. Results: Except for the central superior hemifield, there was no significant difference between the NTG and HTG groups on the mfVEP and HVF plots. In the central superior hemifield, 14 (74%) NTG eyes vs. 6 (38%) HTG eyes had abnormal clusters on mfVEP plots, and 12 (63%) NTG eyes vs. 3 (19%) HTG eyes had abnormal clusters on HVF plots. These differences were both statistically significant. There was no significant difference in the optic nerve head images in the sectors that corresponded to the central superior hemifield. Conclusions: The pattern of visual field damage differs in NTG and HTG in the central superior hemifield on mfVEP and HVF. In agreement with prior studies [4], confocal scanning laser ophthalmoscopy does not show a structural difference between NTG and HTG in the optic nerve head. 1.Hood et al (2002) AO. 2. Hood and Greenstein (2003) Prog Ret Eye Res. 3. Fortune et al (2005) DOOP 4. Nakatsue et al (2004) J. Glaucoma.

Keywords: electrophysiology: clinical