PLOS ONE · 6 authors, 4 centres
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This large cohort study of 6078 outpatients found that short tear break-up time (TBUT) and superficial punctate keratitis (SPK) are significant risk factors for eye strain, blurred vision, and photophobia. Thicker ganglion cell complex (GCC) was a risk factor for eye strain, while thinner GCC was a risk factor for blurred vision. These findings support the role of dry eye and intrinsically photosensitive retinal ganglion cells in common visual symptoms and may guide clinical management.
**Background:** Eye strain is a common ocular symptom, especially with increased screen time, but few studies have linked it to objective examination findings. This study aimed to investigate associations between dry eye signs, retinal thickness, and three common visual symptoms (eye strain, blurred vision, photophobia) in a large outpatient cohort.
**Methods:** This hospital-based cross-sectional cohort study enrolled consecutive first-visit outpatients from two Japanese clinics (April 2015–March 2020). Inclusion criteria: best-corrected visual acuity better than 20/30 in both eyes. Exclusion criteria: history of intra-ocular lens implantation, glaucoma medication, or acute eye disease within one week. A total of 6078 patients (3920 women, mean age 49.0 ± 20.4 years) were analyzed. Patients were interviewed for presence/absence of eye strain, blurred vision, and photophobia. Examinations included tear break-up time (TBUT), Schirmer test with anesthesia, vital corneal staining for superficial punctate keratitis (SPK), and spectral-domain OCT for macular ganglion cell complex (GCC) thickness, peripapillary retinal nerve fiber layer (NFL) thickness, and full macular thickness. Logistic regression calculated odds ratios (OR) and 95% confidence intervals for each symptom, adjusted for age and sex.
**Key Results:** Prevalence of symptoms: eye strain 31.8%, blurred vision 22.5%, photophobia 16.0%. Abnormal examination findings: short TBUT (≤5 s) 53.0%, SPK 23.5%, low Schirmer (≤5 mm) 28.8%. All symptoms were more prevalent in women. Short TBUT was significantly associated with all three symptoms: eye strain (OR 1.88), blurred vision (OR 1.85), photophobia (OR 1.77). SPK was also a significant risk factor: eye strain (OR 1.44), blurred vision (OR 1.24), photophobia (OR 1.32). GCC thickness showed opposite associations: thicker GCC was a risk factor for eye strain (OR 1.30), while thinner GCC was a risk factor for blurred vision (OR 0.59). Schirmer test, peripapillary NFL thickness, and full macular thickness were not significantly associated with any symptom. Age was significantly higher in patients with blurred vision and photophobia.
**Clinical Implications:** This study provides objective evidence linking dry eye signs (short TBUT, SPK) to common visual symptoms, supporting the use of tear film stabilizers and anti-inflammatory treatments. The differential association of GCC thickness—thicker GCC with eye strain and thinner GCC with blurred vision—suggests a role for intrinsically photosensitive retinal ganglion cells (ipRGCs) in eye strain and highlights the need for further investigation of retinal structure in symptomatic patients. Female gender was a consistent risk factor, emphasizing the importance of gender-sensitive management. The findings support symptom-oriented clinical reasoning and may guide interventions such as dry eye therapy and blue-light filtering for eye strain, while thin GCC warrants evaluation for glaucoma or other optic neuropathies. Limitations include lack of functional visual acuity, contrast sensitivity, and accommodation testing, and the clinic-based design may introduce selection bias.