Aspects in the development of Dynamic Noise Perimetry

Alshaghroud, Kholoud 2014. Aspects in the development of Dynamic Noise Perimetry. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The purpose of this thesis was to develop further the concept of Dynamic Noise Perimetry (DNP). The influence of 4 different strengths of Gaussian filter on the DNP stimulus edge, without and with a noise mask, was separately investigated in 15 normal individuals at three eccentricities. The DNP threshold was not affected by the filtering. The critical check size of the noise mask was investigated in 11 normal individuals at three eccentricities for 8 different checks per cycle. The critical check size at the fovea was 4 checks per cycle and in the periphery between 2 and 4 checks per cycle. The influence of optical defocus was investigated in 11 normal individuals at three eccentricities. For a defocus of +4.00DS, sensitivity without the noise mask declined by approximately 1dB; with the noise mask sensitivity increased by 1dB. The original ‘Proof of Concept’ threshold algorithm, which enabled the estimation of threshold at one location in approximately 3 minutes, underwent numerous modifications. The final iteration permitted threshold estimation at 45 locations in approximately 7 minutes. Five of the ten individuals with open angle glaucoma who had undergone DNP and standard automated perimetry (SAP) in 2007 were re-examined, using an identical protocol, after a follow-up of four years. The abnormality with DNP at baseline was present at the follow-up in all five individuals and was more severe in 3 individuals. Only 2 individuals exhibited abnormality by SAP. The influence of the learning effect on the outcome of DNP was evaluated, in one designated eye at each of the five weekly visits, for 10 ‘young’ and 8 ‘elderly’ normal individuals naïve to perimetry. Optimum performance was essentially achieved at the third visit without and with the noise mask.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Uncontrolled Keywords:	Dynamic Noise Perimetry, visual field, threshold algorithm, glaucoma.
Date of First Compliant Deposit:	30 March 2016
Last Modified:	22 Dec 2023 13:22
URI:	https://orca.cardiff.ac.uk/id/eprint/66298

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