COMPARISON OF EYELID ANGLE MEASURED USING MANUAL AND DIGITAL IMAGE ANALYSIS METHOD

Aim: To compare the eyelid angle measured by using a manual method (Using protractor) and digital image analysis method (Using ImageJ software) at different distances of eye gaze. Methodology: This prospective cross-sectional study was conducted in the preclinical lab at Manipal College of Health Professions. Subjects with no eyelid abnormalities were included in the study and they were asked to fixate at different distances a) at 3 metre (Distance gaze) b) at 70 cm (Intermediategaze) and c) at 40 cm(Near gaze). Using a protractor, the eyelid angle measurements were repeated at various distances which comprised the manual measurement. In the image analysis method, images were captured during distance, intermediate and near gaze using smartphone placed on theside of the face. These images were then analysed using ImageJ software for determining eyelid angle using image analysis method. Palpebral fissure height, Palpebral fissure width, Interpupillary distance, Intercanthal width, Binocular width, Height of open upper lid were some additional anthropometry measurements that were done using meter scale and PD ruler. Results: The mean age of the participants was 20±0.5 years. Anthropometry measurements of the eyelid and Palpebral fissure were done using meter scaleand PD ruler. The mean and standard deviation of the measured parametersare as follows Interpupillary distance: 60.95±2.37 mm, Endo Inter canthal distance: 32.20±2.39 mm, Exo Inter cantal distance: 95.50±3.80 mm, Palpebralfissure height_OD: 12.11±1.32 mm, Palpebral fissure height_OS:12.16±1.46mm, PFW_OD: 32.00±1.10 mm, PFW_OS: 32.11±1.24 mm, Height of upper eyelids_OD: 10.26±1.66 mm and Height of upper eyelids_OS:10.42±1.83 mm. In the right eye, there was no statistically significant difference (p>0.05) between manual protractor method and digital image analysismethod at distance but there was a statistically significant difference (p<0.05)between manual protractor method and digital image analysis method atIntermediate and near. In left eye, there was statistically significant difference(p<0.05) between manual protractor method and digital image analysis method at all three distances. Conclusion: There is a significant difference in eyelid angle measured using manual protractor method and digital image analysis method. The measurement of eyelid angle serves as a critical reference point during cosmetic and reconstructive surgical interventions of the eyelid and accurate measurements are essential for preoperative assessment, surgical planning and postoperative evaluation. Hence more studies on the validation of the anthropometry measurements and eyelid angle using digital image analysis areessential to use digital image analysis in routine eye care practice.

TeleParallax: Low-Motion-Blur Stereoscopic System With Correct Interpupillary Distance for 3D Head Rotations

Binocular parallax provides cues for depth information when a scene is viewed with both eyes. In visual telepresence systems, stereo cameras are commonly used to simulate human eyes. However, motion blur occurs when these cameras are rotated quickly. The use of omnidirectional cameras can reduce the motion blur, but does not provide the correct interpupillary distance (IPD) when viewers tilt or turn their heads sideways. We propose a method called TeleParallax, in which two omnidirectional cameras are separated by the IPD and the direction of the lenses are kept constant in world coordinates by robotic arms during three-dimensional head rotations. TeleParallax can suppress the increase in image buffering during head rotations because each camera can capture an omnidirectional image with the lens direction fixed. We conducted three user studies to evaluate the perceptual effect of head tilt, eye asynchrony, and delays in IPD correction for a particular rotation. The results indicate that TeleParallax can provide depth perception that is independent of the head movement with less visual discomfort. Although the results show that the users were sensitive to the asynchrony between their eyes and to camera motion during IPDs, they retained the feeling of depth perception within interocular delays of 70 ms and motion velocity of 75°/s. These results imply that TeleParallax has remarkable potential for visual telepresence systems.

On the number of viewing zones required for head-tracked autostereoscopic display

A head-tracked display could be made from a two-view autostereoscopic display where head-tracking allows the display to swap the two views when the eyes move from viewing zone to viewing zone. Variations in human interpupillary distance mean that this basic two-view version will not work well for the significant minority of the population who have interpupillary distance significantly different from the average. Woodgate et al. proposed, in 1997, that a three-view system would work well. Analysis of an ideal version of their proposal shows that it does work well for the vast majority of the population. However, most multi-view, multi-lobe autostereoscopic displays have drawbacks which mean that, in practice, such a system would be unacceptable because of the inter-view dark zones generated by the inter-pixel dark zones on the underlying display technology. Variations of such displays have been developed which remove the inter-view dark zones by allowing adjacent views to overlap with one another: the views appear to smoothly blend from one to the next at the expense of a little blurring. Such displays need at least five viewing zones to accommodate the majority of the adult population with head-tracking and at least six viewing zones to accommodate everyone. © 2006 SPIE-IS&T.

Variation and extrema of human interpupillary distance

No description supplied

On the number of viewing zones required for head-tracked autostereoscopic display

A head-tracked display could be made from a two-view autostereoscopic display where head-tracking allows the display to swap the two views when the eyes move from viewing zone to viewing zone. Variations in human interpupillary distance mean that this basic two-view version will not work well for the significant minority of the population who have interpupillary distance significantly different from the average. Woodgate et al. proposed, in 1997, that a three-view system would work well. Analysis of an ideal version of their proposal shows that it does work well for the vast majority of the population. However, most multi-view, multi-lobe autostereoscopic displays have drawbacks which mean that, in practice, such a system would be unacceptable because of the inter-view dark zones generated by the inter-pixel dark zones on the underlying display technology. Variations of such displays have been developed which remove the inter-view dark zones by allowing adjacent views to overlap with one another: the views appear to smoothly blend from one to the next at the expense of a little blurring. Such displays need at least five viewing zones to accommodate the majority of the adult population with head-tracking and at least six viewing zones to accommodate everyone. © 2006 SPIE-IS&T.

Variation and extrema of human interpupillary distance

No description supplied

Ophthalmic Anthropometry among Rural Dwellers in Mashonaland Central Province, Zimbabwe

Introduction The measures of ophthalmic anthropometric parameters may vary among races and ethnic groups but are of immense importance in clinical diagnosis and management of oculo-visual defects. There is paucity of data on these measures among the Zimbabwean population. Purpose The aim was to determine ophthalmic anthropometric parameters among rural dwellers in Zimbabwe. Methods Six ophthalmic anthropometric parameters including interpupillary distance (IPD), head width (HW), temple width (TW), length to bend (LTB), and apical radius were measured using a pupillometer, PD rule, Head width calipers, Fairbank facial gauge, and ABDO frame rule. Results A total of 471 participants aged 18 to 100 years (mean age = 55.13; SD± 17.33 years). Of the 471 participants, 206 (43.7%) were males and 265 (56.3%) were females. A mean interpupillary distance at far was 65.57 ± 4.80 mm, mean temple width of 12.49 ± 1.53 cm, mean head width of 13.61 ± 1.39 cm and a side length to bend of 10.24 ± 1.20 cm and the apical radius was 9.94 ± 1.37. There was a significant (P < 0.05) difference between the ophthalmic anthropometric parameters of males and females except for temple width and apical radius. Conclusion A narrower interpupillary distance but a wider temple width was observed among adult Zimbabweans. A significant difference in ophthalmic anthropometric parameters between males and females were observed except for temple width and apical radius. This should inform eyewear manufacturers and importers of frames on the facial and ocular parameters of Zimbabweans to improve the aesthetics and ensure a comfortable vision for wearers of already-made near vision spectacles for presbyopes. Rwanda J Med Health Sci 2021;4(1):99-111