Ergonomic Innovation In Slit Lamp Microscopy: A Proof Of Value Study

Performing slit lamp examinations is associated with cervical spine discomfort in ophthalmologists. In a survey of 1,807 ophthalmologists, 81% reported work-related musculoskeletal symptoms associated with slit lamp use. The purpose of our study was to determine:

1) the efficacy of adjustable slit lamp oculars versus fixed oculars in reducing musculoskeletal neck strain in ophthalmologists. This was achieved by measuring joint angles in the c-spine of ophthalmologists during slit lamp examinations using a slit lamp with conventional fixed oculars vs a slit lamp with adjustable oculars

2) to determine potential gains in work productivity associated with improved working posture, comfort and reduced fatigue

Participants were staff ophthalmologists and trainees at the Ivey Eye Institute, Department of Ophthalmology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada. Written, informed consent was obtained from all participants. Eighteen participants, including 8 females and 10 males, were enrolled in this study.

The study involved three sessions for each participant, conducted in three examination lanes. Participants were randomized to complete each simulated slit lamp examination session on non-consecutive days to minimize carryover effects. Before each assessment participants completed a validated worker discomfort survey.

Each session involved the use of one of the three slit lamp configurations: 

1. Conventional fixed oculars  

2.  20 degree fixed inclined oculars 

3.  Adjustable oculars 

During each session, high-resolution photographs were taken of participants in profile to capture postural data to estimate joint angles, positions and biomechanical demands. Validated usability surveys were used to assess perceived comfort of participants.

Mean discomfort rating: 2.33 for conventional slit lamp configuration; 2.17 for inclined oculars;  0.15 for adjustable oculars. 

Cervical Flexion: adjustable oculars vs. inclined oculars ( 7.82° ± 6.59°  vs.16.69° ± 6.03°, p < 0.0001), vs. standard configuration (17.34° ± 7.26°, p < 0.0001). No statistical improvement with inclined oculars vs. standard configuration (p = 0.67). 

Head Tilt Position: mean upper head angle was -9.56° ± 6.06° with conventional oculars vs inclined oculars -0.63° ± 4.89° (p < 0.001) vs adjustable oculars1.02° ± 4.86° ( p < 0.0001). 

Biomechanical demand: adjustable oculars reduced demand (1.25 Nm ± 1.10 Nm, p < 0.0001) vs. conventional oculars (2.57 Nm ± 1.25 Nm) vs. inclined oculars (2.45 Nm ± 1.15 Nm)

Our results indicate significant differences in the ergonomics of the three slit lamp configurations. The adjustable oculars promote better working postures, reduced neck strain and improved user comfort. The biomechanical data demonstrates that the adjustable oculars produce almost half the muscular demand compared to the conventional oculars, which has a calculated increase in work productivity of 24%. The postural improvements measured with the adjustable oculars highlight the potential to decrease physical strain, reduce fatigue and increase work productivity. This proof of value study is the first study in the ophthalmology literature to demonstrate the potential gains associated with improving equipment ergonomics.