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| DC Field | Value | Language |
|---|---|---|
| dc.contributor.advisor | Izzuddin Hairol, Dr. | |
| dc.contributor.author | Qazi Muhammad Omair (P70221) | |
| dc.date.accessioned | 2023-09-14T08:02:19Z | - |
| dc.date.available | 2023-09-14T08:02:19Z | - |
| dc.date.issued | 2016-06-07 | |
| dc.identifier.other | ukmvital:84755 | |
| dc.identifier.uri | https://ptsldigital.ukm.my/jspui/handle/123456789/460419 | - |
| dc.description | When a letter at size threshold is surrounded by flankers, confusion ensues and our ability to recognise the letter reduces, compared to when recognising it when it is presented in isolation. This is known as the crowding phenomenon. The objective of this study was to investigate the effects of different types, numbers and orientation of flankers on the recognition of foveally fixated letters at resolution limits. First, single Sheridan Gardiner letters were presented to the participants using a computer monitor. The viewing distance was chosen such that the participants' correct response rate ranged between 75% to 80%. Next, the target letter was presented together with different types of flankers, i.e., other letters, flanking bars or a surrounding box. The flankers were arranged either horizontally, vertically, or on all four sides of the target letter. The separation between the target letter and flankers were randomised systematically. The performance of the participants to recognise the target letter was measured across these separations. When the target letter was flanked by letter flankers, greater crowding was observed with vertically arranged letter flankers than with horizontally arranged letter flankers. One-way repeated measures ANOVA showed that flanker orientation had significant effects on crowding magnitude [F(2, 14) = 10.54, p = 0.002]. The effect of target-flanker separation on crowding was highly significant [F(5, 35) = 62.54 , p < 0.0001]. There was also a significant interaction between flanker orientation and flanker-target distance [F(10, 70) = 6.540, p< 0.0001]. When the target letter was flanked by bars, vertically arranged bar flankers show more crowding than horizontally arranged bar flankers. Repeated measures ANOVA showed that there were significant effects of bar orientation [F(2, 14) = 9.43, p = 0.003] and separation [F(10, 70)= 3.95, p < 0.001] on crowding magnitude. Crowding also occurred when the target letter was surrounded with a box. The effects of separation between target and letter and the surrounding box was significant [F (1, 7) = 56.43, p <0.001]. For all flanker types, maximum crowding was observed when the target letter abutted the flankers. There was no significant effects of flanker type on crowding magnitude [F(2, 14) = 1.52, p = 0.25]. However, crowding magnitude elicited by the different flanker types was significantly different depending on the distance between the target letter and the flankers [F(10,70) = 3.90, p < 0.0001]. Significant crowding was observed with all three types of flankers when they were abutting the target. It is concluded from the study that type and orientation of the flankers have significant effects on crowding magnitude for letters at size threshold presented at the fovea. The results from this study could be helpful in designing a new vision chart that can elicit better crowding effect than commercially available charts.,Master Of Health Sciences (Optometry) | |
| dc.language.iso | eng | |
| dc.publisher | UKM, Kuala Lumpur | |
| dc.relation | Faculty of Health Sciences / Fakulti Sains Kesihatan | |
| dc.rights | UKM | |
| dc.subject | Crowding | |
| dc.subject | Foveal | |
| dc.subject | Vision Tests | |
| dc.subject | Optometry | |
| dc.subject | Universiti Kebangsaan Malaysia -- Dissertations | |
| dc.title | Spatial characteristics of foveal letter crowding | |
| dc.type | theses | |
| dc.format.pages | 100 | |
| dc.identifier.callno | WW20.O54s 2016 9 Tesis | |
| Appears in Collections: | Faculty of Health Sciences / Fakulti Sains Kesihatan | |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| ukmvital_84755+Source01+Source010.PDF Restricted Access | 246.01 kB | Adobe PDF |  View/Open |
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