Although measurements of glaucomatous structural damage using optical coherence tomography (OCT) are widely used to aid glaucoma diagnosis and assess rates of progression, the relationship between structural changes and vision-related quality of life (VRQoL) remains poorly understood. It is important to characterize this relationship to determine whether OCT measurements are related to visual disability and are valid surrogates of outcomes directly relevant to patients.
Recently, it has been shown that faster rates of retinal nerve fiber layer (RNFL) thinning, are associated with faster rates of decline in VRQoL, with loss of RNFL associated with worsening quality of life, even after adjusting for changes on visual field.1 These findings provide evidence that measuring rates of change in RNFL is a valid marker of glaucoma-related disability.1 In the current study, Prager and colleagues examined the relationship between macular structural changes and VRQoL. A growing body of evidence has shown the importance of damage to the macula in glaucoma, even at early stages2, and one would expect changes in the macula to be associated with change in VRQoL. A cross-sectional study was conducted including 107 patients. Quality of life was assessed using the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25), with OCT used to measure macular retinal ganglion cell and inner plexiform layer (RGC+IPL) thickness, and visual fields assessed using the 10-2 strategy. As both eyes of an individual are likely to contribute to VRQoL, binocular field sensitivities were calculated and an integrated maximum (and minimum) binocular RGC+IPL thickness derived by averaging the highest (or lowest) RGC+IPL thickness measurements from each of 6 sectors of each eye.
Surprisingly, there was no association between RGC+IPL thickness and VRQoL, which was unexpected given the importance of the macula for central visual function. It is also contrary to evidence that patients with worse central visual field report worse quality of life.3 The negative result may be due to patients having similar average RGC+IPL thickness but differences in VRQoL due to different patterns of macular RGC+IPL loss. Lack of association may also be due to the complexity of quality of life assessment or to the cross-sectional study design. Contributors to quality of life such as socioeconomic status or comorbidities were not examined, and previous investigations into RNFL thickness and VRQoL showed a relationship in longitudinal but not cross-sectional analyses.1,4 To reduce the effect of inter-individual variation in perceptions of VRQoL, and to more fully elucidate the relationship between macular structural changes and quality of life, it is important the study is repeated using a longitudinal design.
Surprisingly, there was no association between RGC+IPL thickness and VRQoL
Despite the overall lack of association between GCL+IPL thickness and VRQoL, patients with widespread macular thinning were found to have worse VRQoL than those with focal damage. This suggests that glaucoma may have a greater impact on daily living in patients with diffuse compared to focal macular damage, however the reasons for this remain unclear. The authors should be commended for drawing attention to the need for studies to validate measurements obtained from imaging devices by elucidating their relationship to patient reported outcome measures.