An evaluation of stereoacuity (3D vision) in practising surgeons across a range of surgical specialities
Introduction
Surgery is a visually-demanding occupation requiring fine judgements of distances and depth. The brain can use several mechanisms to judge depth, one of which is stereopsis.1 Stereopsis is the ability to fuse two images of an object which differ slightly due to the different perspective of each eye, in order to form a single three-dimensional (3D) percept. Stereopsis is easily testable in the clinic and has often been used as the stand-alone measure of depth perception. Stereopsis is quantified as stereoacuity. It has been argued that good vision and in particular good stereoacuity ought to be a requirement for practising as a surgeon and therefore for embarking on a surgical career.2, 3 However, opinion remains divided on the matter.
Although relevant to all surgical specialities, the topic has received greatest attention among ophthalmic surgeons. A survey of UK ophthalmologists found that 80% of respondents felt that there should be a visual standard for ophthalmologists and of these, 94% felt that it should include stereoacuity.3 However, less than 10% of countries have a visual standard for ophthalmologists3 and it is estimated that only around 20% of ophthalmology residency programmes in the USA test trainees' stereoacuity.4
A literature review in 2008 concluded that there was no evidence to conclude that stereopsis was necessary for satisfactory performance in ophthalmic surgery.5
Several studies have approached this topic using surgical simulators to examine the relationship between stereoacuity and performance on generic surgical skills,6 intraocular techniques7, 8, 9, 10 and laproscopic dexterity.11 These have tended to show inferior performance for subjects with deficient stereopsis, however the subjects were generally surgery-naïve and the tasks were therefore unfamiliar. It is not clear what relevance these findings have to experienced surgeons who have performed surgical tasks for years, or for trainees who can develop their skills over a long period. It is possible that, with experience, surgeons with deficient stereopsis may utilise alternative strategies (eg motion parallax)4 to compensate.
There therefore remains a lack of evidence about whether stereopsis is necessary for a surgical career. As a first step to explore this, our aim in this study was to determine the range of stereoacuities in a cross-section of currently-practising surgeons in the NHS, across the breadth of surgical specialities. Although unable to examine the relationship between stereoacuity and surgical competency, such an evaluation would provide a context for any proposed recommendations for visual requirements for entering into a surgical career.
Section snippets
Materials and methods
We certify that all applicable institutional and government regulations concerning the ethical use of human volunteers were followed during this research. Ethical approval for the study was obtained from the London Local Allocation Service of the National Research Ethics Service and institutional approval from the Research Department of St George's University. Written informed consent was obtained from all participants.
The investigators were two final year medical students (MB and SH) who
Results
In total 69 surgeons were approached, of whom three refused to participate, giving a 96% participation rate. Of the 66 surgeons tested, 36 were Trainees and 30 were Consultants (including one Associate Specialist). The breakdown of surgeons by specialism is shown in Table 1.
All 66 surgeons achieved a measurable stereoacuity value on the Frisby test. Four (6%) did not achieve any recordable stereoacuity on TNO, and one (1.5%) of these also was unrecordable on Titmus. Three of these four were
Discussion
This is the first study that has evaluated stereopsis in practising surgeons. Our principal finding was that most surgeons have high-grade stereoacuity, however around 20% do not, and a significant proportion have reduced stereoacuity on two of the three stereotests. On the purest test of stereopsis out of the three, the TNO, 15% had reduced stereoacuity and 6% had unrecordable stereoacuity. This suggests that, for some individuals at least, it is possible to be a practising surgeon even with
Conclusion
While we found that most surgeons in current NHS practice have high-grade stereoacuity, there are also surgeons with reduced stereopsis and some with no stereopsis. The findings do not therefore support the assertion that high-grade stereopsis is a universal requirement for a career in surgery. It would be difficult to justify setting a stereoacuity criterion for entrance into a surgical training programme, although stereotesting may yet have a role as perhaps one item in a varied panel of
Acknowledgements
We acknowledge the help of Emma Hrynaszkiewicz in training and Louise Garnham in assessing the investigators in the use of the stereotests, and the co-operation of the surgical staff of St George's hospital.
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These authors are joint first authors.