Randomised cross-over trial assessing the impact of angle, area, distance, curvature, volume, spatial coordinates, and effect of eye exercises in surgical task performance
: 2D vs 3D laparoscopic vision

  • Gobinath Ramakrishnan

Student thesis: Master's ThesisMaster of Science


Background: There is a good body of evidence to suggest that 3 dimensional imaging improves surgical task performance during laparoscopic surgery. This improved performance in surgical task, however comes at a price of increased eye strain for a subgroup of surgeon. This often causes headache and even nausea. However to date, no study has been reported in explaining the underlying scientific reasons for the apparent improvement in 3D surgical task performance nor the causes for the eye strain and possible ways to minimize this squeal.

Objective: This study was aimed to investigate the effect of angle, area, distance, volume, curvature and spatial coordinates in 3D versus conventional 2D imaging in laparoscopic surgery. Furthermore, the rate of visual symptoms seen in 3D laparoscopic surgery and any possible intervention to alleviate this problem need to be addressed.

Hypothesis: The volume and spatial coordinates will be significantly affected in 3D imaging compared with other components of angle, area, distance and curvature. The 3D visual symptoms will be significantly influenced by introduction of simple eye exercises before the 3D task.

Study design: A prospective, cross-over and randomized study in a purpose built, state of the art laboratory setting based at the Cuschieri Skills Centre (CSC).

Methods and materials: A full research protocol was submitted for ethical approval. Consented students with no previous laparoscopic surgical experience were chosen among medical students at the University of Dundee. The standardized surgical tasks were set up in a purpose built body trainer with laparoscopic ports inserted for the introduction of either a thirty degree 2D or 3D camera scope. 24 students were recruited for the study.

The students were required to undergo a visual acuity test (Snellen chart) and eye deviation test (with Maddox Wing). They were then asked to grade on visual analogue scale symptoms before and after the 2D and 3D laparoscopic tasks. Those who underwent 3D laparoscopic tasks were randomized into two group; one arm, who received eye exercises and the other arm without any eye exercises before the laparoscopic 3D tasks. A battery of specific isolated laparoscopic tasks was developed to test their ability to detect changes in 2D and 3D environments separately. The six endpoints were the accuracy in detecting changes in the following components: 1) angle, 2) area, 3) distance, 4) volume 5) curvature and 6) spatial coordinates. All the components except the spatial coordinates were assessed in three different methods: creation, measurement and comparison. The results were analysed with paired and independent t test using IBM SPSS version 22.0. Spatial coordinate tests were video recorded and subjected for Human Reliability Analysis (HRA).

Results: There was no statistical difference in angle, distance and curvature in 2D versus 3D imaging but there was a statistical difference for square measurement at 7cm, volume measurement at 3ml and volume comparisons which showed significance in 3D imaging. The most accurate level for distance creation is 2cm and for distance measurement is 4cm and for circle measurement is 4cm. For angle, the most accurate degree for creation is 5 and for measurement is 35 in both imaging. And for volume assessment, 3ml was noted to be most accurate volume for both volume creation and measurement in 2D and 3D imaging. The spatial coordinates produced statistical significance results in 3D imaging and we could safely conclude that spatial coordinates was the pivotal for the enhanced 3D imaging. Error probability calculation revealed that a 10 percent higher probability of committing errors in 2D compared to 3D. For type of errors, pastpointing and touching wrong objects were higher in 2D and statistically significant (p=0.001, p=0.038). For visual symptoms, eye strain was significant in 2D with p= 0.022 and difficulty in refocusing from one distance to another was significant in 3D with p =0.035. For visual symptom between the 2D and 3D imaging, difficulty in refocusing from one distance to another was significant in 3D (p=0.027). Performing simple eye exercises before 3D imaging had no effect on relieving visual symptoms.

Conclusion: Spatial coordinates was the underlying reason for the better task performance in 3D surgical imaging. Eye strain was prominent in 2D imaging and difficulty in refocusing from one distance to another was annoying in 3D. Besides, eye exercises before the 3D laparoscopic tasks as a possible solution for 3D visual symptoms did not bring any significant results.
Date of Award2021
Original languageEnglish
SupervisorAfshin Alijani (Supervisor) & Vanessa Kay (Supervisor)


  • 2D vs 3D laparoscopic vision. Eye symptoms in laparoscopic surgery

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