Purpose: To estimate informal caregiver (ICG) strain in people from a glaucoma clinic.; Methods: Patients with glaucoma were consecutively identified from a single clinic in England for a cross-sectional postal survey. The sample was deliberately enriched with a number of patients designated as having advanced glaucoma (visual field [VF] mean deviation worse than -12 dB in both eyes). Patients were asked to identify an ICG who recorded a Modified Caregiver Strain Index (MCSI), a validated 13 item instrument scored on a scale of 0-26. Previous research has indicated mean MCSI to be >10 in multiple sclerosis and Parkinson's disease. All participants gave a self-reported measure of general health (EQ5D).; Results: Responses from 105 patients (43% of those invited) were analysed; only 38 of the 105 named an ICG. Mean (95% confidence interval [CI]) MCSI was 2.4 (1.3, 3.6) and only three ICGs recorded a MCSI > 7. The percentage of patients with an ICG was much higher in patients with advanced VF loss (82%; 9/11) when compared with those with non-advanced VF loss (31%; 29/94; p = 0.001). Mean (standard deviation) MCSI was considerably inflated in the advanced patients (5.6 [4.9] vs 1.5 [2.2] for non-advanced; p = 0.040). Worsening VF and poorer self-reported general health (EQ5D) of the patient were associated with worsening MCSI.; Conclusion: ICG strain, as measured by MCSI, for patients with non-advanced glaucoma is negligible, compared with other chronic disease. ICG strain increases moderately with worsening VFs but this could be partly explained by worse general health in our sample of patients.