Extended periods using digital devices (computers, smartphones, tablets, etc.) are associated with ocular symptoms and physical discomfort.1-3 As many as 90% of digital device users experience symptoms of digital eye strain (DES) or asthenopia.1
A recipe for asthenopia at any age
A consequence of extended device use is accommodative micro-fluctuations (AMFs) that occur at near viewing. AMF is the temporal ocular instability caused by spasms of the ciliary muscle when viewing a near target.4
There are two components to AMF4:
- Low frequency of less than 0.6Hz that is of neurological origin
- High frequency of 1.0-2.3Hz that is related to arterial pulse frequency
Overworked, tired ciliary muscles are not responsive to slight increases in accommodative load, causing the high-frequency component of AMF to rise.4
In addition, physical changes to the ciliary muscle are observed during the accommodation process. The ciliary muscle exhibits an increase in anterior length thickness and maximum thickness. During accommodation on a near image at 20 cm, ciliary muscle anterior length thickness increased 23%, and maximum thickness increased 34%.5
The stress caused by the accommodative response, along with a dry, irritated ocular surface, is a recipe for asthenopia (eye fatigue and eye strain).
A study to compare contact lens designs6**
A recent paper presented at BCLA 2021 sought to determine if wearing spherical or aspherical lens designs impacted AMF and patient-reported symptoms of eye fatigue or strain related to digital device use. This prospective, cross-over, subject-masked evaluation included 24 individuals aged 20 to 35 who used digital devices for four or more hours per day and currently wore soft contact lenses with sphere range +3.00 to -6.00DS; <0.75DC. This was a cross-over study where participants were assigned to two equal groups, then fitted with either Biofinity or Energys for two weeks, followed by a switch to the other lens for two weeks. Evaluations included baseline measures of accommodative functions, the performance of both contact lenses on the last day of wear, and patient-reported changes in symptoms of digital eye strain.
Contact lenses compared had the same material, water content, diameter, and base curve. The only difference between lenses was the front-surface optical design. Biofinity Energys has a multiple aspheric curve, which introduces greater positive power at the center of the curve. In contrast, Biofinity Sphere is aspherical, which reduces the spherical aberration introduced by the lens power.
Aspherical lens design can improve AMF response6*
Findings from the study showed that subjects wearing an aspherical lens (Biofinity® Energys) experienced significantly lowered AMF compared to a spherical lens (Biofinity® Sphere). The study also showed that visual acuity levels are very good with Biofinity Energys, and there was no significant difference in acuity in those fitted with Biofinity.
Aspherical lens design reduces patient-reported eye tiredness6*
At the end of every two weeks of contact lens wear, investigators administered the Italian version of the standardized Computer-Vision Symptom Scale questionnaire (CVSS17) to evaluate changes in self-reported symptoms.
Biofinity Energys® wearers were significantly less likely than Biofinity® sphere wearers to say:
- Their eyes felt tired during or after working with a computer
- They had to strain to see well after some time working with a computer
- Their eyes hurt when working with a computer
- They had to blink a lot while using the computer at work
- They had heavy eyes at the en d of a working day
- When all other features are identical, aspherical lens design reduces accommodative microfluctuations compared to a spherical lens
- Several patient-reported symptoms of digital eye strain significantly improved with aspherical lens vs. spherical lens
- Aspherical contact lenses (Biofinity Energys®) help reduce subjective symptoms of eye strain in young adults*
* Baseline 56.67 ± 2.28 high frequency components; after 2 weeks of daily wear Biofinity 59.38 ± 2.61 HFC and Biofinity Energys 55.47 ± 1.79 HFC; p=0.002)
**After 2 weeks of daily wear Biofinity 4,5 ± 1,4 and Biofinity Energys 3,1 ± 1,5; p<0.05.
Coles-Brennan C, Sulley A, Young G. Management of digital eye strain. Clin Exp Optom. 2019;102(1):18-29. doi:10.1111/cxo.12798
Sheppard AL, Wolffsohn JS. Digital eye strain: prevalence, measurement and amelioration. BMJ Open Ophthalmol. 2018;3(1):e000146. doi:10.1136/bmjophth-2018-000146
Contact Lens Spectrum. Continuing education: keeping up with ocular fatigue in the digital era. 2016;31:3-10. Accessed January 3, 2022. https://www.clspectrum.com/supplements/2016/june-2016/continuing-education-keeping-up-with-ocular-fatig/continuing-education-keeping-up-with-ocular-fatig
Kajita M, Muraoka T, Orsborn G. Changes in accommodative micro-fluctuations after wearing contact lenses of different optical designs. Cont Lens Anterior Eye. 2020;S1367-0484(20)30046-1. doi:10.1016/j.clae.2020.03.003
Data on file. Prospective, multi-center (9 sites), subject-masked, bilateral wear, cross-over, non-dispensing study comparing the difference of the change in AMF frequency measured by the Accommodative Function Analyzer instrument (AFA). CooperVision; 2018.
Montani G, Treso F, Martena M. et al. Effects of different contact lens design on accommodative function and eyestrain symptoms of young adult subjects after VDT use. Presented at: 2021 BCLA Virtual Clinical Conference and Exhibition; June 13-14, 2021.