Tired Eyes from Microsurgery—It's Blinking Obvious!

I have been plagued with the tired, dry eye after concentrating on a microsurgical anastomosis and I appear not to be alone. Looking into the cause, it's actually very simple, because the brain is the organ at fault. The spontaneous eye-blink rate (SEBR) has a normal complete blink rate of 17 (mean) blinks per minute sitting quietly, and this increases to 26 per min during conversation. Females have a higher blink rate compared with men during reading, but there is no differences related to age, eye color, or wearing glasses. Cognitive processes with marked visual attention influence blink rate, hence while reading, the blink rate drops to 4.5 per min.[1] Distinct blinking patterns have been studied when concentrating at a video display terminal (SEBR reduces to 5 to 6.6 per min[2] [3]) or playing computer games,[4] producing the dry eye pattern and increased tear film break-up.

The blink rate, amplitude, and tear film stability are compromised during dynamic visual display unit terminal tasks; blink rate decreases dramatically during presentation of highly demanding visual information, cognitive challenges, and the need for visual information input to the visual cortex.

Spontaneous eye blinking serves a critical function but also interrupts incoming visual information. The inhibition of eye blinks may constitute an adaptive reaction to minimize the loss of visual information. The average adult will spend 44 minutes with his or her eyes closed during a normal waking day. Experimental conditions have revealed that blink inhibition is an autonomic reactivity intrinsic to the visual system.[5]

To relate this to microsurgery, six microsurgeons blinded to this experiment were observed performing microvascular anastomosis using the microscope in a laminar flow operating theater, with ambient temperature of 19 to 21°C (66 to 70°F) and relative humidity between 45 and 55%. A set of six observations was recorded per surgeon on how many complete blinks were performed in 1 minute while undertaking this cognitive task. The control was a similarly matched theater staff member performing passive tasks in the same environment.

• References

• 1 Bentivoglio AR, Bressman SB, Cassetta E, Carretta D, Tonali P, Albanese A. Analysis of blink rate patterns in normal subjects. Mov Disord 1997; 12: 1028-1034
• 2 Skotte JH, Nøjgaard JK, Jørgensen LV, Christensen KB, Sjøgaard G. Eye blink frequency during different computer tasks quantified by electrooculography. Eur J Appl Physiol 2007; 99: 113-119
• 3 Schlote T, Kadner G, Freudenthaler N. Marked reduction and distinct patterns of eye blinking in patients with moderately dry eyes during video display terminal use. Graefes Arch Clin Exp Ophthalmol 2004; 242: 306-312
• 4 Himebaugh NL, Begley CG, Bradley A, Wilkinson JA. Blinking and tear break-up during four visual tasks. Optom Vis Sci 2009; 86: 106-114
• 5 Shultz S, Klin A, Jones W. Inhibition of eye blinking reveals subjective perceptions of stimulus salience. Proc Natl Acad Sci U S A 2011; 108: 21270-21275