Electrophysiological evidence of early functional damage in glaucoma and ocular hypertension.

Purpose: The quantification of early retinal ganglion cell damage in ocular hypertension and glaucoma.

Methods: Thirty subjects under treatment for open-angle glaucoma, 23 subjects with ocular hypertension, and 28 healthy subjects in a control group were investigated by monocular pattern electroretinogram (ERG), L&M (long and medium wavelength) cone ERG, and S (short wavelength)-cone ERG. The diagnosis of glaucoma was based on masked assessment of digital stereoscopic optic nerve head images by three glaucoma specialists.

Ganglion cell loss and dysfunction: relationship to perimetric sensitivity.

Purpose: To describe two methods of neural damage quantification from perimetric data, and to discuss their theoretical implications.

Methods: A recently published model of retinal ganglion cell (GC) receptive field density is used to obtain best estimates of the receptive fields per solid degree at each stimulus point in the 24-2 test pattern array. A method of age related change compensation is proposed and a functional relationship between perimetric sensitivity and GC survival is used for loss quantification.

Can pulsatile ocular blood flow distinguish between patients with and without diabetic retinopathy?

Purpose: Our aim was to determine if pulsatile ocular blood flow (POBF) measurements could distinguish between type 2 diabetes mellitus (DM) subjects with and without diabetic retinopathy (DR).

Methods: Ninety-eight DM subjects were recruited. POBF was measured using an Ocular Blood Flow tonometer and retinopathy was assessed using retinal digital photography.

The length of Henle fibers in the human retina and a model of ganglion receptive field density in the visual field.

An experimental study of lateral displacement of ganglion cells (GCs) from foveal cones in six human retinas is reported. At 406-675 microm in length, as measured in radially oriented cross-sections, Henle fibers are substantially longer than previously reported. However, a new theoretical model indicates that the discrepancies in these reports are mainly due to meridional differences.

Silent substitution S-cone electroretinogram in subjects with diabetes mellitus.

A defect in the blue sensitive mechanism has been reported in certain ocular and systemic diseases. For example, tritanopic colour vision defects and changes to the S-cone electroretinogram (ERG) have been demonstrated in glaucoma and diabetes mellitus. Electrophysiological methods of eliciting the S-cone ERG, however, often result in considerable L- and M-cone intrusion.

The effect of post prandial glucose changes on oscillatory potentials in subjects with type 2 diabetes mellitus.

Purpose: To investigate the effect of elevated plasma glucose levels on oscillatory potentials (OPs) in patients with diabetes mellitus.

Method: 15 patients with type 2 diabetes mellitus, with no ophthalmoscopically visible signs of diabetic retinopathy (NDR), were recruited, mean (SD) age 65.1 (10.

S-cone, L + M-cone, and pattern, electroretinograms in ocular hypertension and glaucoma.

Silent substitution and selective adaptation techniques were used to obtain full field S-cone and L + M-cone electroretinograms from 18 patients with ocular hypertension (OHT), 9 with normotensive glaucoma (NTG), 18 with early primary open angle glaucoma (POAG) and 19 normal controls. Pattern electroretinograms were also recorded, using a reduced check size to increase the contribution of retinal ganglion cells. In the OHT and POAG groups, statistically significant reductions (P = 0.

The S-cone electroretinogram: a comparison of techniques, normative data and age-related variation.

The blue sensitive mechanism in human colour vision is highly susceptible to damage in ocular disease. There is a need for objective methods to assess this and several methods of recording the blue cone (S-cone) electroretinogram (ERG) have been described. We therefore compared a silent substitution technique (SST) and a selective adaptation technique (SAT) using a novel combination of optical filters, on 24 normal subjects.

The construction of a model eye for investigation of laser-tissue interactions in scanning laser ophthalmoscopy.

Purpose: To develop a model eye to study laser-tissue interactions during retinal imaging with scanning ophthalmoscopy.

Methods: A model eye was designed to match the optical properties of the human eye based on the Bennett and Rabbetts schematic eye.

Results: Alterations in axial length resulted in changes in refractive error similar to those in the human eye (3.

Cortical OFF-potentials from the S-cone pathway reveal neural damage in early glaucoma.

We used background adaptation and silent substitution techniques to record full-field ON and OFF-visually evoked cortical potentials (VECPs) selectively from the S-cone and L- and M-cone pathways in 15 patients with primary open angle glaucoma (POAG), and 15 normal controls. The most statistically significant (P=0.01) VECP test for POAG was a voltage change in the S-cone pathway cortical OFF-response.

Ocular optics, electroretinography and primary open angle glaucoma.

Advancing the knowledge of ocular image quality is important in the development of new tests for the earlier detection of primary open angle glaucoma (POAG). Loss of blue sensitivity is an important feature of POAG; however, it is difficult to separate this loss from the effects of wavelength related intraocular light scatter and media absorption. A technique for recording the S-cone electroretinogram is described which may solve these problems.