Self-assessed visual function in cataract surgery using Catquest-9SF

Abstract

The cataract disease is the leading cause of preventable blindness in high-income countries alone as well as globally despite the groundbreaking technological advancements in recent years and steadily increasing number of cataract operations. Even when the clouded lens of the eye has been successfully removed during cataract surgery and been replaced by a plastic intra-ocular lens (IOL) a significant number of patients experience no benefit from cataract surgery. There is an ongoing quest to find factors that affect the result and to monitor and ensure high-quality cataract surgery. The Swedish National Cataract Register (NCR) collection of data on more than 2 million cataract surgeries is a great aid in this challenge. In 2009 the NCR introduced Catquest- 9SF, recently proven to be a state-of-the-art questionnaire. We used Catquest-9SF to investigate factors that might affect the outcome of cataract surgery using the patient self-assessed visual function perspective. We also studied the reliability of Catquest- 9SF and the minimum important difference (MID) of the results.

In Paper I we investigated how other simultaneous diseases of the eye in addition to cataract affect the patient self-assessed outcome of cataract surgery using the Catquest-9SF in a prospective nationwide, multicenter study including more than 10,000 patients. This comorbidity study showed that several other ocular diseases at the time of cataract surgery affect the patient´s self-assessed visual function after cataract surgery despite inclusion of the preoperative corrected distance visual acuity (CDVA) and postoperative CDVA in the analyses.

Paper II assessed how challenging characteristics of the eye and difficulties during surgery as well as the feared complication of posterior capsular tear affect the outcome of cataract surgery in a prospective study including almost 11,000 patients from 42 Swedish surgical ophthalmology units. Several of the studied intraoperative difficulties and complications were significantly associated to the patient-reported outcome in cataract surgery. Including the preoperative CDVA and postoperative CDVA in the analyses reduced the impact of the intraoperative difficulties.

In Paper III our aim was to estimate the reliability of the Catquest-9SF questionnaire. In patient reported outcome measurement (PROM) it is fundamental that the patients’ answers are repeatable, that they do not depend on chance, that the reliability is high. This test-retest study of the reliability of the Catquest-9SF, including 144 patients, showed an intraclass correlation of 0.93, thus we can conclude that the reliability of the Swedish Catquest-9SF is very high. Together with previous knowledge, our findings support continued use of the Catquest-9SF in assessing the quality and outcome in cataract surgery.

Our most recent study was reported in Paper IV in which we assessed the minimum important difference (MID) of Catquest-9SF. The large set of data in the NCR has a statistical power large enough to find even rather small significant associations. Our purpose was to assess how large the change measured in logit has to be to be significant to the patient, that is the MID. The assessment of MID of Catquest-9SF in this study adds detailed knowledge of MID and shows that MID differs depending on the baseline visual function. The findings enable even more precise high-quality evaluation of the outcome and benefit of cataract surgery.