Measuring outcomes of cataract surgery using the Visual Function Index-14


PURPOSE: To determine which version of the Visual Function Index-14 (VF-14) most precisely measured cataract surgery outcomes, rescale the VF-14 using Rasch analysis, and create a short-form version for comparison.

SETTING: Flinders Medical Centre, Adelaide, South Australia, Australia.

METHODS: In this cohort study incorporating questionnaire development, participants were drawn from the cataract surgery waiting list at Flinders Medical Centre. There were 2 cohorts: a preoperative cohort used for questionnaire development and an outcomes cohort. All patients had cataract surgery by phacoemulsification with intraocular lens implantation. Rasch analysis was used to refine the VF-14 into valid long-form (VF-11R) and short-form (VF-8R) versions. The ability of 8 versions (original; 2 proposed versions; 5 previously proposed versions) of the VF-14 to discriminate cataract surgery outcomes was compared with that of the standard VF-14 using the relative precision method.

RESULTS: The preoperative cohort comprised 210 patients and the outcomes cohort, 51 patients. Large gains in visual functioning occurred with cataract surgery, and these were detectable with all versions of the VF-14. The largest gain in precision, 125% (relative precision. 2.25), occurred for VF-8R. Short forms that were not Rasch scaled showed gains in precision, from 23% to 80%. The VF-8R also showed the largest gains in precision in 2 subgroups: with ocular comorbidity (relative precision, 2.14) and without ocular comorbidity (relative precision, 2.48).

CONCLUSIONS: Results show an unequivocal advantage to using Rasch-scaled scores for assessing cataract surgery outcomes. The 8-item, Rasch-scaled VF-8R appears ideally suited for measuring cataract surgery outcomes given its high precision and short test time.

J Cataract Refract Surg July 2010; 36:11811188
Submitted: 23 November 2009. Final revision submitted: 2January 2010. Accepted: 21 January 2010.

Vijaya K Gothwal1,2, Thomas A Wright1, Ecosse L. Lamoureux3,4,5 and Konrad Pesudovs1
1NH&MRC Centre for Clinical Eye Research, Department of Ophthalmology, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, South Australia, Australia
2Meera and L B Deshpande Centre for Sight Enhancement, Vision Rehabilitation Centres, L V Prasad Eye Institute, Hyderabad, India
3Centre for Eye Research Australia, Department of Ophthalmology, University of Melbourne, Victoria, 8002, Australia
4Vision CRC, Sydney, New South Wales, Australia
5Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.

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