Authors: Prima Moinul, Joshua Barbosa, Bryon McKay, Anne Beattie, Nina Ahuja, Mark Fava, Mei Lin Chen, Enitan Sogbesan, Forough Farrokhyar, Varun Chaudhary

Purpose: Minimally important difference (MID) is the threshold change in functional vision that patients perceive to be beneficial, such that they are willing to undertake the risks associated with treatment. Our objective is to determine the MID for functional vision after cataract surgery using Catquest 9SF in a Canadian population. 

Study Design: Single-centered, prospective cohort study 

Methods: Adult patients undergoing elective cataract surgery completed the Catquest 9SF and VF-14 visual disability questionnaires two weeks prior to and three months following their cataract surgeries. Patient demographics, pre- and post-operative best-corrected visual acuities (BCVA), contrast sensitivity using the Pelli-Robson chart, and wait-times to surgery were assessed. MID scores on the Catquest 9SF questionnaire were calculated using regression analysis, anchor-based longitudinal approach and distribution-based methods with a 95% confidence intervals on SPSS software V23. 

Results: In total, 83 patients (71.6±10.8 years old, 59.0% female) were enrolled in the study. BCVA, contrast sensitivity and VF-14 scores improved pre-to-post operatively in all patients (77.1±11.4 to 83.0±9.5 (p<0.001); 1.07±0.42 to 1.55±0.19 (p<0.001); and 77.1±15.9 to 94.0±10.9 (p<0.001), respectively). Seventy patients (87.4%) self-reported a great deal of improvement in vision post-operatively. All patients experienced a significant decrease in mean Catquest Rasch score from -0.60±1.59 pre-operatively to -3.20±1.9 post-operatively (p<0.001) corresponding to improved functional vision. The Catquest anchor-based MID scores were -2.49, -2.52, -2.56 and approximately -2.5 using BCVA, contrast sensitivity, VF14 and wait-time as anchors, respectively. The mean wait time to surgery was 25.8±20.2 weeks. 

Conclusions: This is the first Canadian study to provide an evidence-based approach to wait-time target for cataract surgery referrals while maximizing a patient’s ability to achieve MID and improvements in quality of life including improvements in BCVA, contrast sensitivity, and functional vision.