Depth and Distance Perception of Dentists and Dental Students
The quality of work carried out by dentists is dependent, among other things, on experience, training, and manual dexterity. Historical focus on the latter as a predictor of dental performance has failed to recognize that dental competence also requires good perceptual and visual skills, not only for gathering information but also for judging positions, distances, and the size of objects and shapes. Most predictive tests ignore visual and interpretative deficiencies that could make individual acquisition of skills and interpretation of instructions difficult. Ability to estimate depth and distance, the manner in which students learn this ability, whether and how it can be taught, or whether there is an association among ability, stereopsis, and dental performance has not been thoroughly examined; nor has the perception that dental students fully understand verbal and written instruction relating to depth and distance. This study investigated the ability of dentists and dental students to estimate and reproduce small depths and distances and the relationship of this ability to stereopsis, dental experience, and student performance. A total of 163 undergraduate dental students from three year groups and 20 experienced dentists and specialists performed three tasks. A depth-perception task involved estimation of the depth of two sets (2-mm or 4-mm wide) of nine computer milled slots ranging in depth from 0.5 to 4.0 mm. A distance task involved estimation of the width of specially prepared printed square blocks. In a writing task, participants recorded distances across a printed line on separate sheets of paper. All tasks were conducted at set positions in custom-made transportable light boxes. Stereopsis and visual acuity were also measured. Ability to perform perceptual tasks varied enormously, with the level of accuracy dependent on the type of task and dental experience. Many students had considerable difficulty in estimating depth. Inexperienced students performed poorly. Most participants overestimated depth and distance estimation tasks, but underestimated when required to draw distances. Smaller depths and distances were easier to estimate than larger ones. All groups overestimated depth more in 4-mm-wide blocks than in 2-mm-wide blocks. There was no correlation found between depth and distance estimation and stereopsis scores or with the overall grades tested. This study highlights that some dentists and many dental students, particularly early in their course, have great difficulty in accurately gauging depths and distances. It is proposed that that this could impact significantly on a student's ability to interpret verbal and written preclinical instruction and could make the acquisition of manual skills and interpretation of clinical instruction difficult. Routine testing of all undergraduate dental students for perceptual and visual difficulties is recommended, so that those with difficulties can be identified and problems remedied, if possible, early in their course.SUMMARY
INTRODUCTION
The quality of the work carried out by a dentist is dependent, among other things, on experience, training, and manual dexterity.1,2 Consequently, there has been a strong focus on manual dexterity as a predictor for successful dental performance.2-6 However, such research fails to recognize that competency within dentistry also requires good perceptual and visual skills, not only for gathering information, but more specifically for judging positions, distances, and the size of objects.7,8 What is ignored by most predictive tests is that prospective dental students may have visual or interpretative defects that would make acquisition of manual skills and interpretation of instruction difficult. This could significantly affect their performance and contribute to procedural errors.1,7,8,10,11 Although it is acknowledged that manual dexterity is an essential and highly desirable quality for a dental student to possess, and studies have examined vision in dental populations, the number of studies that have examined interactions between manual dexterity and vision are few.5,9,10
Good eyesight is essential to providing the best dental care for patients.7,11 It is interesting that dentists and dental students as a group have been found to be recalcitrant regarding frequency of eye examinations.7,8,11 Rawlinson12 reported that some dental students had undetected visual defects that could potentially have influenced the performance of precise practical tasks and suggested that prospective dental students undertake visual screening tests prior to their acceptance into dental schools.12,13
Good depth perception is also a necessary requirement for the practice of dentistry.1,7,14,15 It is necessary, however, not only to perceive that surfaces are at different depths (stereopsis) but also to accurately estimate (measure) depth within a three-dimensional object. Depth estimation has often been mistaken as stereopsis, which is only part of a complex interaction of neurological, physiological, and visual attributes that lead to depth appreciation.12,13,16 Stereopsis is the measurable ability to perceive depth.16-18 It relates to the capacity to fuse separate retinal images from each eye into a single image, thus creating the perception of depth.16,17 Traditional studies have often relied solely on the assessment of stereopsis rather than examining the true depth judgment.19 A small body of literature has reported on the prevalence of stereopsis in the dental population and its relationship to student results, and the general consensus is that it is not vital to dental performance.8,11-13,17 Notwithstanding this, the practice of dentistry still requires practitioners to accurately assess depth. The ability of the dental community to estimate depth has not yet been thoroughly examined; nor has the manner in which students learn this ability, whether and how it can be taught, or whether there is an association among this ability, stereopsis, and overall dental performance.
The capacity to accurately estimate small linear distances is also another important consideration. Dunne1 demonstrated that 70% of students and dental practitioners underestimated the test sizes needed to achieve accurate vernier caliper adjustments.1 Likewise, Mancini and Jedynakiewicz20 demonstrated that on average, dental students undersized linear measurements of stylized cavity preparations by 46%. Although there has been no correlation found between accuracy of distance estimation and manual dexterity scores, Dunne1 concluded that there was a difference between a “real” and a “dental” millimeter, with the dental millimeter being the smaller of the two.
There is undoubtedly an assumption among dental educators that students understand verbal and written instruction relating to depth and distance. Whether this perception is true has not been tested thoroughly. There is also a need for an investigation into the educational importance of a dental student's ability to estimate depth and distance, whether and how quickly these abilities are learned, the relationship of these abilities to experience and stereopsis, and whether variations in ability affect student grades during their dental course. This study aimed to investigate some of these issues.
The primary goal of this research was to study the ability of dental students and dentists to accurately assess depths and estimate distances. Secondarily, it aimed to examine the relationship of these perceptual abilities to stereopsis, dental experience, and preclinical or clinical performance.
METHODS AND MATERIALS
A total of 163 undergraduate students from three different student-year groups at the School of Dentistry, University of Queensland, and 20 experienced practitioners, predominantly endodontists and prosthodontists, took part in this study. The project was approved by the School of Dentistry Dental Science Ethics Committee, and prior to any research written consent was obtained from all participants, all of whom volunteered to take part in the project. Three different student-year groups were chosen. These represented students who had no experience in preclinical operative dentistry (Bachelor of Dental Science and Bachelor of Oral Health students) (group 1, n = 68); students who had almost 12 months' preclinical experience (Bachelor of Dental Science) (group 2, n = 49); and fourth-year students who had extensive clinical experience (Bachelor of Dental Science) (group 3, n = 46). The 20 specialists made up group 4.
Participants were required to undertake three different perception tasks designed to evaluate their ability to accurately gauge depth and distance. To ensure standardization of distance and illumination, all tasks were conducted at set positions in custom-made transportable light boxes. A light meter was used at each session to ensure consistency of the light intensity (illuminance). Each task was conducted individually in a separate light box.
Depth Perception Task
In this task, participants were requested to assess the depths of each of the 18 computer-milled preparations (Weir Services Pty Ltd Sale, Victoria, Australia) made in 20 × 10 × 10 mm aluminum blocks. Preparations were 8 mm long. Nine were 2 mm in width, and nine were 4 mm wide (Figure 1a). Milled depths were 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, and 4.0 mm. The blocks were arranged randomly, but each participant viewed the blocks in the light box in the same order. Participants were asked to estimate the depths of preparations to the nearest tenth of a millimeter and to record these on preprinted forms that allowed them to choose a depth between 0 and 9.9 mm. The only auxiliary instrumentation was a dental mirror, which the participants were allowed to use to aid their judgment.
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Distance Estimation Task
In this task, participants were required to estimate the width of 20 printed square blocks. The blocks comprised two vertical black rectangles separated by a white space (Figure 1b). The distance between the two rectangles was the same as the width of each rectangle. The distances between the rectangles were 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 mm. Each distance was represented twice, making a total of 20 blocks to be tested. Participants were asked to estimate the distance between the solid rectangles to the nearest tenth of a millimeter and to record these on preprinted forms that allowed them to choose a distance between 0 and 9.9 mm. Distances were ordered randomly, but each participant performed the task in the same order.
Writing Task
In this task, participants were required to mark 10 specific distances on separate sheets of paper across a printed line with a sharp pencil. The required distances were 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 4.0, and 5.0 mm. Distances were ordered randomly, but each participant performed the task in the same order. The distances between the two lines were later measured under 12× magnification over a light box using an electronic digital caliper (DSE, Taipai, Taiwan) with an accuracy of 0.01 mm.
Stereopsis
The Lameris TNO test was used to assess stereopsis. Participants wore red and green glasses that allowed them to locate superimposed or “hidden” three-dimensional images on standard plates (stereograms). The degree of stereoscopic acuity was quantified by measuring the number of plates correctly identified by the participant. The sensitivity of the plates ranged from 15 to 480 seconds of arc; the higher the value, the poorer the stereoscopic vision.
Visual Acuity
The visual acuity of each eye was tested monocularly and binocularly using a high contrast logarithm of the minimum angle of resolution (logMAR) (Snellen) chart at a distance of six meters under standard high luminance conditions. Participants were required to wear any current personal corrective eyewear eyeglasses or contact lenses) for this test. They were required to progressively read through the letters (from largest to smallest) until they could no longer identify letters.
Correlation With Student Grades
The relationship between the ability of the dental students' performance on the three tasks were compared with their results obtained for a cutting exercise on color-coded blocks (group 1) and results in clinical operative dentistry (group 3).
Statistical Analysis
Statistical analyses were used to detect any significant differences between student-year groups in relation to task results and to test the relationship among stereopsis, grades, and group results. The average error in each group for each task was first calculated, recorded, and plotted. For statistical analysis, the absolute average error value was used, this being the difference between the correct answer and the estimated answer, not taking into account whether estimations were greater or lesser than the correct answer. Comparisons between the results of the tasks for each group were carried out with analysis of variance using the STATA 10.0 statistical package (StataCorp, College Station, TX, USA). Data that were skewed were transformed using logarithmic transformations prior to analysis. Regression analysis was used to evaluate the relationship among absolute average errors, grades, and stereopsis scores. Chi-square tests were used to compare the proportion of participants within each level of experience whose average answers were more than 0.5 and 1.0 mm away from the true values.
Reliability of Results
Assessing the writing task required the recorder to measure the drawn distances under magnification. To assess intraexaminer variability, 25% of the measurements were remeasured and the two sets of data compared.
RESULTS
The ability of students and dentists to perform the perceptual tasks varied enormously, with the level of accuracy dependent on the tasks performed and the clinical experience of participants. The means of error and absolute error for each group for each task are presented in Tables 1 and 2. Participants who thought that a given depth or distance was greater than the actual measurement were said to have overestimated. Participants who thought the given depth or distance was less than the actual measurement were said to have underestimated.
As is evident in Figures 2 and 3, most participants overestimated in depth and distance tasks. However, as can be seen in Figure 4, most participants underestimated distances in the writing task. Students in group 1, those with no practical preclinical experience, performed significantly poorer on all tasks. Student groups exhibited greater range in average error than did the specialist group. However, all groups had an inherent degree of inaccuracy in the estimation of physical dimensions without an objective guide.
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Depth Perception
Many students, particularly those in early years of study, had considerable difficulty in estimating depth, as highlighted in the scatterplot (Figure 2). Many students overestimated depth by an average of 1 mm or more. Some participants were identified whose average error in depth estimation exceeded 2 mm with a maximum average error of 3.5 mm, all in the less experienced groups (1 and 2). Ability to estimate depth appeared to improve with the initiation of preclinical and clinical experience. Depth was overestimated by 73% of participants, with a 95% confidence interval (66,79), which shows significantly more people overestimated than underestimated depth. The ability to perform this task was also affected by the width of the block. Participants in all groups tended to overestimate depth more in wider blocks than in narrower blocks.
In Figure 5 the average absolute error for depth perception is shown. There was a considerable range among the participants in their ability to consistently estimate depth. The level of accuracy appears to improve with clinical experience. In particular, the scatter of results was less evident in the more experienced groups. When the average absolute error in the participants' estimated depths was compared across the four groups, it was found that the means of the four groups were different (ANOVA, p = 0.0002). Bonferroni multiple comparisons showed a significant difference between the mean absolute error of group 1 (those with no preclinical experience) and the three other groups (group 2, p = 0.003; group 3, p = 0.01; group 4, p = 0.006; see Table 2). That is, students in group 1 performed significantly worse as a group and with a higher level of variability in average error than all other groups. There was no significant difference among the other groups.
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
The percentage of participants whose ability to accurately gauge depth to within 0.5 mm of the actual depth is shown in Figure 6. For depth perception, less than half of the participants had absolute average errors within this range. There was also evidence (χ2, p = 0.017) of a difference between groups, with logistic regression showing that the proportion of participants whose average absolute error was less than 0.5 mm in group 1 was significantly higher than the other three groups (group 2, p = 0.002; group 3, p = 0.031; group 4, p = 0.022).
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Distance Estimation
The ability of participants to estimate distances also varied considerably, with most participants overestimating distances. Figure 3 illustrates the average error in distance estimation. Seventy-one percent overestimated distance with a 95% confidence interval (64,78), which showed that significantly more participants overestimated distance than underestimated it. When the average absolute error for distance estimation was compared across the four groups, evidence was found that the means of the four groups were not the same (ANOVA, p = 0.0228) (Figure 7). The inexperienced group (group 1) performed worse than all the other groups. No significant difference was found among the other groups.
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Ability to estimate distance to within 0.5 mm of the actual distance is illustrated in Figure 6. Less than half of the participants had average absolute errors in this range. As with depth perception, group 1 (inexperienced students) did not perform as well as the other three groups. Logistic regression showed that the proportion of participants whose average absolute error was more than 0.5 mm was significantly greater in group 1 than the other three groups (group 2, p = 0.001; group 3, p = 0.002; group 4, p = 0.001).
Writing Task
The average error in the writing task is illustrated in Figure 4, and the absolute error is illustrated in Figure 8. Most participants underestimated distance in the writing task, which required participants to physically draw lines at specific distance intervals. This contrasts with the results in the distance and depth estimation tasks. Seventy-nine percent underestimated distance, with a 95% confidence interval (73,85), which showed that significantly more participants underestimated distances in the writing test than overestimated them. When the average absolute error in the writing task was compared across the four groups, no evidence (p = 0.0928) was found of a difference in the means between the four groups. Experienced practitioners demonstrated a smaller range of error, although this was not statistically significant. When the proportion of participants whose average absolute error was less than or equal to 0.5 mm was compared, logistic regression showed evidence that group 1 was significantly worse than groups 2 and 4 (group 2, p = 0.044; group 3, p = 0.648; group 4, p = 0.026).
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Reliability of Results
When the original writing task measurements were remeasured to assess intraexaminer reliability, the maximum difference between the two measurements for the average error was 0.04 mm with a maximum difference of 0.09 mm for a single task. These values were considered small enough to be insignificant in a practical sense.
Impact of Size of Task
A comparison of participants' average absolute error specifically for the 1 to 2 mm and the 4 to 5 mm depths and distances showed evidence (t-test, p < 0.001) of a difference between the tasks, with participants estimating or drawing the smaller distances with greater accuracy.
Stereopsis and Visual Acuity
The levels of binocular visual acuity of the participants are presented in Figure 9. The majority of participants had good visual acuity of 0 logMAR (equivalent to Snellen 6/6) or better. One student, however, performed very poorly, showing a visual acuity as low as 0.6 logMAR (equivalent to Snellen 6/24). It is interesting that this student also performed poorly on the cutting exercise. Most participants achieved satisfactory levels of stereopsis; Figure 10 demonstrates the distribution. Regression analysis showed that there was no evidence (p = 0.863) of a relationship between a participant's stereopsis score and their average absolute error in depth estimation.
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Citation: Operative Dentistry 36, 5; 10.2341/10-290-L
Grades and Depth
Regression analysis showed that there was no evidence of a relationship between a participant's average absolute error in depth and distance estimation and their resulting grade for either the first or fourth-year students (first year, p = 0.258; fourth year, p = 0.733).
Summary of the Results
Many students and some dentists had difficulties performing all three tasks. The average range of error was as high as 3.5 mm for depth perception and 2.5 mm for distance perception for some individuals. Most participants overestimated when asked to interpret depth and distance but underestimated when asked to draw distances. Inexperienced students performed significantly worse in estimational tasks than all other groups. However, experienced dental practitioners were not significantly better in their ability to gauge small measurements.
Less than half of all participants in all groups were able to estimate depth or distance to within half a millimeter. Of the inexperienced students (group 1) only 10% estimated depths accurately within 0.5 mm and only 24% estimated distances to within 0.5mm. Smaller depths and distances (1 and 2 mm) were easier to estimate than larger ones (4 and 5 mm). Width of preparation affected depth perception. Most students had good levels of visual acuity and stereoacuity. There was no correlation among depth estimation, stereopsis scores, and results obtained from a preclinical cutting exercise or clinical grades.
DISCUSSION
This study identified that many students, particularly in the early years of dental education, have difficulty accurately gauging small depths and distances. Verbal and written instructions such as “make that a millimeter wide” or “take that down another half a millimeter” require interpretation. Students who do not have a proper concept of depth and distance would presumably have difficulty undertaking such instructions, and it would seem logical to assume that such large discrepancies may impact clinical and preclinical performance. The significance of these issues, however, is hard to determine because performance and assessment of it is based on a complex interaction among different skill sets.
That most students overestimated depths and distance when asked to visually interpret them but underestimated distance when asked to reproduce it is consistent with Dunne's conclusion that a real millimeter and a dental millimeter are not the same.1,20 However, by limiting the data assessment to averages, previous studies have failed to emphasize the large scatter in performance that can be clearly seen in our data (eg, Figures 2-4). Although it is not clear what level of error is acceptable for clinical practice, or which of these discrepancies is the most undesirable, it is conceivable that participants who inaccurately estimate depths and distances are likely to produce shapes that are in excess of what is required and that the level of error in perception will compound this. Of note is that experienced practitioners showed more consistent results, with fewer outliers.
It is clear that in the cohort of students tested there was no significant correlation between task result and clinical grades achieved; however, this neither proves nor disproves a relationship between depth and distance perception and practical skill. The lack of a relationship is likely to have more to do with the method of assessment, rather than with a lack of an association with the tasks. Other researchers have also experienced problems trying to relate other specific abilities to student performance.2-4,6,10,17,21,22
Grades for the preclinical technical exercise assessed in the study (where students had to prepare cavity shapes in color-coded blocks) were not a comprehensive measure of interpretative ability because manual dexterity was a key determinant of performance in this task. Student clinical grades are also influenced by other subjective variables such as inconsistencies of assessors, variance in tasks required, patient difficulty, and patient management. Thus, the impact of a single factor such as perceptual skills on overall clinical grades cannot be easily quantified. Additionally, students with poor interpretive skills but good memory and manual dexterity may be able to copy (memorize) demonstration models accurately although their ability to “know” (perceive) what a millimeter is may be compromised. As such, this is an argument for the preparation of three-dimensional models as well as visual and written instructional material in dental practical courses to cater to students with differing abilities.
This study only looked at a snapshot of four groups of the dental population at a specific point in time. Although statistical evidence did not support the inference that there was a steady increase in the ability to perceive depth and distance with respect to experience, nevertheless there was a reduction in the absolute error with greater clinical experience, the most significant improvement appearing to coincide with the initiation of practical training. A way in which a pattern could more accurately be established would be to initially test an entire cohort of first-year students and then follow and retest them at regular intervals throughout their course of study. The authors believe this would be a valuable exercise that could be supplemented by assessing the impact of remedial training on test outcomes with or without comparison with control groups who are not given remediation during their course.
Sound oculomotor capabilities are important factors in dentistry, especially considering that the quality of tasks and preparations are largely and subjectively assessed by simple visual examinations.1,7,8,12,13 The distribution of visual acuity in this study is similar to that reported by Rawlinson12,13 and to that generally reported in the literature regarding visual acuity in the dental population.8,12 The majority of the participants had good distance visual acuity in the range from −0.2 (6/4) to 0.1 (6/7.5) logMAR (Snellen); however, some myopic participants had poor visual acuity up to 0.5 (6/24). In these cases of myopia, the participant may still attain reasonable levels of visual acuity at shorter distances. A number of participants, however, were unaware of their reduced levels of visual acuity and stereoacuity, which may support the case for routine screening of vision in this population.
Although it was anticipated that there would be a correlation between stereopsis and depth perception abilities, considering that stereopsis is a major determinant of the latter, this was not demonstrated. The judgment of depth is a complex process involving both binocular and monocular cues, so that even when binocular cues are removed (no stereopsis) the viewer still has a sense of depth due to the presence of monocular cues.23 Failure to detect any significant correlations may be because the participants were able to make supplementary use of monocular cues during the depth estimation task, such as aerial perspective, shadows, and motion parallax as they freely moved their heads.12,17,24 In the clinical setting, dentists can use these same cues to enhance depth perception.12,13,16,24 Failure to do so may make the acquisition of clinical skill increasingly difficult.12,13 Although stereopsis may not be essential to the practice of dentistry, it is obvious that depth judgment as an entity should be.
That there was no correlation between stereopsis and student grades is similar to the findings of a previous study, which concluded that there are no advantages in using stereopsis as a visual predictor of clinical performance.17 It has, therefore, been postulated that stereopsis may not be clinically essential if compensatory mechanisms are developed.12,13,17,22 However, even with perfect stereopsis, a high standard of clinical performance is not guaranteed because there are many neurological and psychological factors that influence hand-eye coordination.12,16,23
Apart from the problems already identified in matching test results with student performance, there are some limitations that the authors would address in future studies. In assessing depth and distance, participants filled in preprinted forms that allowed them to choose a measurement from and including 0 and 9.9 mm. It was assumed that given the maximum depth or distance tested was 5 mm, this range would be sufficient. However, for some students this was not so. It is probable that for these few students the average error would have been even greater had they been allowed to use a larger scale. Students who participated in this study did so as volunteers. Thus not every student in every year group was assessed. Whether this influenced the results is not known, but it is possible that students who knew they had problems of this nature, despite assurances of anonymity, may have elected not to take part. Further studies involving greater numbers of students and all students in a year group may show more statistically significant results. This is particularly the case in the specialist group where numbers were lower and where greater numbers of statistically significant differences might have been evident if specialist numbers had been higher.
Many past studies have tried to match predictive tests with student grades and clinical performance and found no clear correlations.2,3,5,9,22 Rather than attempting to design another predictive test, the primary aim of this study was to establish whether dentists and dental students have problems with the interpretation of depth and distance. It is obvious that many did have significant problems. Despite any demonstrated positive correlation between perceptual problems and grades, it is suggested that instructors who teach procedures need to be made aware that there are significant differences in the perceptual abilities of students. This awareness should assist in instruction not only in clinical dentistry but in other task-oriented disciplines. It is also suggested that due to the intractable error with subjective judgment of physical dimensions that the use of objective measurements such as periodontal probes, burs of known diameter, or other length-determining objects are used in clinical situations. It is proposed that routine testing of all dental students should be undertaken so that individuals identified with perceptual problems can be informed and, if possible, appropriate steps may be taken to remedy these concerns. It is beyond the scope of the current study to suggest what form this intervention could take. Nevertheless, a protocol similar to that developed in this study could be used for the identification of difficulties. Further work needs to be undertaken to develop and test the efficacy of any intervention program.
CONCLUSION
This study assessed the depth and distance perception abilities of dentists and three different year groups of students. Students in the first year of their course performed worse than dentists and all other year groups. In all student groups, individuals were identified with perceptual problems and who exhibited a large average error for all assessments. Most participants overestimated depth and distance. No relationship was demonstrated between stereopsis testing and depth and distance assessment. Although no correlation was found between depth and distance assessment capabilities and student grades, it would seem logical that students with problems in this area should be alerted and, if possible, steps developed to correct these issues. Therefore, routine testing of all undergraduate dental students for perceptual and visual difficulties is recommended.
(a): Two of the milled blocks used for depth estimation. Preparations were of variable known depth, 8 mm long and either 2 or 4 mm wide. (b): Diagrammatic representation of a printed block used for distance estimation task.
Comparison of the average error in depth estimation between groups. Wide variation in abilities in all groups, with group 1 performing significantly worse than the other groups (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of the average error in distance estimation between groups. There was a wide variation in abilities within all groups, with most overestimating distance (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of the average error in the writing task between groups. No significant difference existing between groups (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of the absolute error in depth estimation across all groups. There was a large error range with group 1 (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of participants, expressed as a percentage, whose average absolute error was correct within 0.5 mm for each of the tasks (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of the absolute error in distance estimation across all groups (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Comparison of the absolute error in the writing exercise across all groups. No significant difference was found between groups (group 1, students, no experience; group 2, students, preclinical experience; group 3, students, clinical experience; group 4, experienced dentists).
Distribution of binocular visual acuity logMAR in the participants. LogMAR is the logarithm of the minimum angle of resolution, or the smallest gap (such as the gap between the limbs in a letter E) that the eye can discriminate at a known distance. Each 0.1 logMAR step is equivalent to one line on the letter chart. A logMAR score of 0 is equivalent to 20/20 or 6/6 Snellen acuity. The majority of participants had good visual acuity.
Stereopsis followed a normal Gaussian distribution. The stereoacuity level (in seconds of arc) represents the smallest distance that can be discriminated in depth in the direction toward/away from the eyes. The fewer the seconds of arc the better the level of stereopsis. The vast majority of participants had a good level of stereopsis.
Contributor Notes
Teodora Dimitrijevic, BDSc (Hons), Brisbane, Australia
Bill Kahler, DClinDent, PhD, University of Queensland, Dentistry, Brisbane, Australia
Gareth Evans, BSc (Hons), PhD, University of Queensland, St Lucia, Australia
Michael Collins, Dip App Sc (Optom), MAppSc, PhD, Queensland University of Technology, Brisbane, Australia
Alex Moule, BDSc(Hons), PhD, University of Queensland, Brisbane, Australia