This cross-sectional study was conducted at ophthalmology operating room (OR) of our tertiary care centre, which is equipped with 3D-HUS monitor and a 3-D compatible viewing microscope (Fig. 1). No patients were involved in the study. This study was assessed as minimal risk and, as such, was exempt from institutional review board review.
2.1 Technical specifications of 3D-HUS: ARTEVO 800 (Carl Zeiss Meditec) surgical microscope and visualization systems were used. Zeiss intraoperative OCT (Rescan 700, Carl Zeiss Meditec) was, wherever intraoperative scanning was required. A 3D video monitor measuring 55’’ mounted on a movable cart, allowing adjustments in the total height of the monitor (floor to topmost point of the display) in the range of 67–72 inches, was used.
2.2 Measurements taken in OR: A single surgeon was observed for surgical position (adjusted as per the convenient ergonomics) during consecutive cataract surgeries performed on ARTEVO system under peribulbar anesthesia. Surgeon position was superior (90 degrees) in all cases. The measurements taken were: monitor height (MH, i.e. the vertical distance of the center of the monitor from the floor), surgeon eye to floor distance (ETFD, i.e. the vertical distance of surgeon eye level from the floor) surgeon eye to monitor distance (ETMD, i.e. the horizontal distance between the surgeon’s eyes and the monitor) (Fig. 1a), viewing tilt (VT, i.e. the angle subtended between the ETMD and an imaginary line connecting the eyepiece of the microscope and the surgeon’s back of the head) (Fig. 1b) and surgeon gaze height (Fig. 1c). The laterality of the operated eye was also recorded.
2.3 Eye and neck strain: Before and after each surgery, the surgeon and assistant rated their eye and neck strain as per Borg’s CR-10 scale.[7, 8] Three questions that were asked were: “To what extent do your eye ache or feel strained?”, “To what extent do you have a burning or smarting sensation in your eyes?” and “To what extent do you feel pain or discomfort in your neck and/or shoulders” to rate the internal symptoms (related to accommodation or vergence stress), external symptoms (related to dry eye disorders) and neck strain, respectively. The surgeon ensured a zero screen time (mobile devices, television screen, etc) at least two hours prior to surgeries, to reduce digital eye strain due to device use.
2.4 Eye Centration: Different ophthalmology residents observed the eye centration on the 3D screen during the surgery, using 3D goggles. They judged the quality of 3D display during the entire surgery, while viewing the monitor sitting in the viewing plane of the surgeon.
2.5 Data Analysis: All data was managed in a Microsoft Excel spreadsheet. Statistical analysis was performed using Statistical Package for the Social Sciences software (SPSS) version 17.0 (SPSS Inc. Chicago, IL, USA). Descriptive statistics were obtained for all parameters and data was expressed as mean ± standard deviation (SD). Mean values for ETFD, ETMD and VT were evaluated for all surgeries by one-way repeated measures analysis of variance (ANOVA). Post hoc analysis was done to compare between different groups of data. A p-value < 0.05 was considered to be statistically significant. All categorical data was analyzed using Pearson Χ2 or Fisher’s exact test.