Validation of a vision-related activity scale for patients with retinitis pigmentosa

Abstract

Purpose: There have been few systematic reports of vision-related activity limitations of people with retinitis pigmentosa (RP). We report a merging of data from the National Eye Institute Visual Function Questionnaire (NEI-VFQ) obtained in five previous studies. We asked whether the Vision Function Scale (VFS; Pesudovs et al., 2010) which was developed for cataract patients would apply in this new population (condition). Methods: Five hundred ninety-four individuals completed a total of 1753 questionnaires, with 209 participants providing responses over at least 4 years. Rasch analysis showed that the 15-item VFS was poorly targeted. A new instrument created by adding four driving-related items to the VFS had better targeting. As an indirect validation, VFS-plus person scores were compared to visual field area measured using a Goldmann perimeter, to the summed score for the combined 30-2 and 30/60-1 Humphrey Field Analyzer programs (HFA), to 30-Hz full-field cone electroretinogram (ERG) amplitude, and to ETDRS visual acuity. Changes in VFS-plus person scores with age and between four common heredity groups were also examined. Results: The Rasch model of responses to the 19 VFS-plus items had person and item separation of 2.66 and 24.43 respectively. The VFS-plus person scores were related to each vision measure (p < 0.001). Over a five-year period, there was a reduction in person scores of 0.5 logits (p < 0.001). Person scores fell by an average of 0.34 logits per decade (p < 0.0001). Participants with an X-linked hereditary pattern had, on average, lower person scores (p < 0.001). Conclusions: The VFS-plus instrument quantified a highly-significant annual reduction in perceived vision-related ability over a five-year period. The outcome was consistent with clinical measures of vision, and detected lower perceived vision-related ability in participants with X-linked disease. It may be of use in future studies, but this needs to be tested in a representative population sample.

The Burden of X-Linked Retinitis Pigmentosa on Patients and Society: A Narrative Literature Review

“…One study observed that, compared with the wider RP population, people with XLRP had lower perceived vision-related ability (as assessed with a modified version of the Vision Function Scale). 38 The correlation between reducing visual function and increasing levels of depression in RP supports the hypothesis that humanistic burden can reasonably be expected to be greater for XLRP than for other forms of RP. 29 An increase in patient burden with increasing severity of the condition has been observed in RP more generally: a study that stratified patients with RP by visual field and visual acuity found that HRQL and emotional state worsened as patients approached legal blindness (residual visual field diameter below 20° and a visual acuity less than 0.3 [0.5 log minimum angle of resolution]).…”

Clinical/Demographic Functional Testing and Multimodal Imaging Differences between Genetically Solved and Unsolved Retinitis Pigmentosa

“…This cannot be captured by BCVA testing alone. In fact, among different measures of visual function, VF size has been shown to be the best predictor of poor mobility in patients with RP [31]. We found that more advanced VF patterns were more frequently seen in genetically solved cases and identified a VFI <53.50% as the optimal cutoff to differentiate solved from unsolved cases (75% sensitivity; 63% specificity).…”

Functional evaluation in inherited retinal disease

“…118,119 The Vision Function Scale-plus (19 items) survey, initially developed for cataract, has also provided promising results in RCD. 120 Recently, the Michigan Retinal Degeneration Questionnaire was also validated as a PRO for patients with IRD, employing 59 items in 7 domains. 121 Whilst there remains no consensus on the most appropriate PRO tools in IRD and whether they need to be disease/genotype specific given the extreme clinical heterogeneity of IRD, they provide clinically meaningful information for both patients and researchers and are an integral assessment to fully evaluate treatment efficacy and calculate costeffectiveness.…”