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Simulation of a central scotoma using contact lenses with an opaque centre
- Source :
- Ophthalmic and Physiological Optics. 38:76-87
- Publication Year :
- 2017
- Publisher :
- Wiley, 2017.
-
Abstract
- Purpose This study evaluated the feasibility of using soft contact lenses (CLs) with an opaque centre to induce absolute central scotomas that move with the eye. We examined the geometrical optics prediction that scotoma size will vary with the size of the CL's opaque centre and with ocular pupil size. We also tested the hypothesis that high environmental light levels will ensure that the ocular pupil will remain small enough, even with opaque centre CLs, to generate absolute scotomas representative of those experienced by patients with age-related macular disease. Methods Using an Octopus 900 Perimeter ( www.Haag-Streit.com), kinetic visual fields (VFs) were measured in five normally-sighted subjects using a V4e Goldmann target with CLs that had central opaque areas with diameters of 2.8, 3.0, and 3.2 mm. To control pupil size, VFs were measured with background perimeter bowl luminances of 10, 585, and 1155 cd m-2 . Subjects attempted to (i) fixate the bowl centre; and (ii) place the scotoma edge at the bowl fixation target (eccentric viewing). Results As predicted, there was a direct relationship between scotoma size and both luminance level and diameter of the opacity. Mean scotoma diameters were 0°, 17.6° and 22°, for the low, medium and high bowl luminances, respectively. Scotoma size was determined primarily by the difference between the diameters of CL opacity and the entrance pupil of the eye and the axial separation between them, and between-subject differences in pupil diameters contributed most to the between-subject variability in scotoma diameter at each light level (SD: 6.01°). Scotoma displacement during eccentric fixation confirmed the gaze-contingent characteristics of this experimental model. Conclusion It is possible to induce a gaze-contingent absolute scotoma and hence mimic central vision loss using centrally-opaque CLs provided that the CL opacity is larger than the entrance pupil of the eye. This simulation tool will, therefore, be ineffective at low environmental light levels (as shown previously) if the entrance pupil of the eye is larger than the CL opacity.
- Subjects :
- medicine.medical_specialty
genetic structures
Opacity
Visual Acuity
Luminance
Article
Pupil
Perimeter
Entrance pupil
03 medical and health sciences
0302 clinical medicine
Ophthalmology
medicine
Humans
Computer Simulation
Scotoma
Central scotoma
Physics
Blind spot
Contact Lenses, Hydrophilic
eye diseases
Sensory Systems
Fixation (visual)
030221 ophthalmology & optometry
Visual Field Tests
sense organs
Visual Fields
030217 neurology & neurosurgery
Optometry
Subjects
Details
- ISSN :
- 14751313 and 02755408
- Volume :
- 38
- Database :
- OpenAIRE
- Journal :
- Ophthalmic and Physiological Optics
- Accession number :
- edsair.doi.dedup.....3c43004af5a5648b12a23667c3d3c700