Campimetry with Offset Stimulus and Dynamic Fixation

Mutlukan, Erkan (1995) Campimetry with Offset Stimulus and Dynamic Fixation. PhD thesis, University of Glasgow.

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The dark-on-bright (negative contrast, light decremental, light offset) stimulus and dynamic fixation target are non-conventional and their usefulness in visual field examination has not been fully documented before. The utility of light offsets (i.e. offset stimuli) and dynamic fixation was investigated for kinetic and static perimetry on a tangent screen without or with automation and the results were compared to those from conventional bright-on-dark (positive contrast, light incremental, light onset) stimuli and static fixation. The disappearance eccentricities of offset and onset stimuli of equal size were determined in eight normal eyes, using dynamic fixation technique at two different levels of surrounding illumination. Kinetic' offset stimulus has a smaller "isoptre" than onset stimulus and, the variation of ambient illumination has less effect on the visibility of offset stimulus. The Oculokinetic Campimetry (OKC) with a constantly exposed offset stimulus was performed in 366 glaucomatous eyes and 217 normal eyes. When a 1.5 mm stimulus was used, a true positive OKC result was obtained in 45% of eyes with relative scotomas and 81% of eyes with small absolute scotomas. A false positive result was obtained in 9% of patients aged 60-70 yrs and 13% of patients older than 70 yrs. When a 3 mm stimulus was used in the glaucomatous patients above the age of 60 yrs, the OKC test was positive in 33% of eyes with relative scotomas and 56% of eyes with small absolute scotomas while none of the control subjects produced a positive result. In 63% of the eyes, abnormal OKC results reflected smaller scotomas than those to the conventional visual field tests, suggesting underestimation of the topographical extent of the scotomas. Inside the absolute scotomas, constantly exposed offset stimulus was still detectable with 19% - 67% frequency between 5

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Bertil E Damato
Keywords: Ophthalmology
Date of Award: 1995
Depositing User: Enlighten Team
Unique ID: glathesis:1995-75376
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 20:22
Last Modified: 19 Nov 2019 20:22

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