Dry Eye-Associated Visual Disturbance

A middle-aged female presented to our practice with complaints of intermittent blurring, especially when reading or after blinking. Her best-corrected visual acuity was 20/20 OU, but at times, particularly after blinking, it was 20/30. Her tear meniscus was 0.5mm, and fluorescein staining revealed scattered punctate keratitis and very rapid breakup of the tear film. We noted significant meibomian gland disease, with dropout in both the upper and lower lids. Our diagnosis was intermittent visual disturbance secondary to dry eye stemming from aqueous deficiency and meibomian gland dysfunction.

Dry eye is a common, and often unrecognized, cause of visual disturbance.¹ Patients who have dry eye may present with a spectrum of complaints including blurred vision, eye fatigue, fluctuating vision with blinking, fatigue, and glare. Underlying mechanisms that often contribute to these symptoms are an unstable tear film and a compromised ocular surface.¹ Inflammation has also been identified as a significant contributor to the development of dry eye.²

Xi at al evaluated tear quality in dry eye subjects compared to control (non-dry eye) subjects.³ Subjects were evaluated with Objective Scatter Index (OSI), modulation transfer function (MTF), and Strehl ratio, which measure the quality of optical image formation. Subjects’ tears were evaluated for 20 seconds, during which they blinked freely, followed by 10 seconds of nonblinking. The OSI index in dry eye patients was evaluated after five seconds of blinking and from five to 10 seconds of blinking. The OSI from zero to five seconds and from five to 10 seconds was significantly higher in dry eye subjects compared to control subjects. Their findings demonstrate the negative impact on image quality in individuals who have dry eye. The authors concluded that it is essential to improve tear film stability to optimize optical quality.³

One issue associated with analysis of dry eye-related visual instabilities is the inability of most clinicians to detect visual or optical changes using standard visual acuity testing. These include fluctuating vision with blinking, blurred vision, glare, and eye fatigue.¹ Koh noted that tear film instability and resultant ocular surface damage in the central corneal region is associated with post-blink higher-order aberrations.¹

An extensive discussion of the treatment of dry eye-induced visual disturbances is beyond the scope of this article. Using double-pass aberrometry, Vandemeer et al compared fluctuations in objective quality of vision in patients who had moderate dry eye.⁴ Subjects were treated with normal saline eye drops or with carmellose 0.5% and hyaluronic acid 0.1% (Optive Fusion, Allergan) (OF). Two hours after instillation of the drops, there was no change in the optical scattering index of the eye treated with saline, but there was significant improvement in eyes treated with OF.⁴ This study demonstrates the potential for improving quality of vision in individuals suffering from dry eye who experience unstable or fluctuating vision.

Meibomian gland dysfunction (MGD) is widely recognized as a significant contributing factor in dry eye disease.⁵ It may lead to increased tear film evaporation and blurring of vision.⁵ Arita et al reported the beneficial effects of treating MGD with five different lid warming devices, three of which used moist heat and two others that used non-moist heat.⁶ They found that the single application of all warming devices improved the visual analog scale (VAS) score, tear film breakup time (TFBUT), and meibum grade. This study supports the concept that therapy directed at MGD improves tear film stability and quality of vision.⁶

In the case of our patient, a multi-armed treatment protocol including in-office and home therapy improved patient comfort and visual performance. The lesson to be learned from this case is that when patients present with fluctuating vision and signs of tear film instability, it is incumbent on practitioners to consider dry eye as the primary underlying cause.

References

1. Koh S. Mechanisms of Visual Disturbance in Dry Eye. Cornea. 2016 Nov;35 Suppl 1:S83-S88.
2. Wang S, Zhang H. Upregulation of the IL-33/ST2 Pathway in Dry Eye. Mol Vis. 2019 Oct 6;25:583-592.
3. Xi L, Qin J, Bao Y. Assessment of Tear Film Optical Quality in a Young Short Tear Break-Up Time Dry Eye: Case Control. Medicine (Baltimore). 2019 Oct;98:e17255.
4. Vandermeer G, Chamy Y, Pisella P-J. Comparison of Objective Optical Quality Measured by Double-Pass Aberrometry in Patients With Moderate Dry Eye: Normal Saline vs. Artificial Tears: A Pilot Study. J Fr Ophtalmol. 2018 Feb;41:e51-e57.
5. Chhadva P, Goldhardt R, Galor A. Meibomian Gland Disease: The Role of Gland Dysfunction in Dry Eye Disease. Ophthalmology. 2017 Nov;124(11 Suppl):S20-S26.
6. Arita R, Morishige N, Shirakawa R, Sato Y, Amano S. Effects of Eyelid Warming Devices on Tear Film Parameters in Normal Subjects and Patients With Meibomian Gland Dysfunction. Ocul Surf. 2015 Oct;13:321-330.