Abstract
Purpose: :
To analyse straylight data from cataract surgery patients, with the view to better assess the development of functional deficits when cataract develops. Straylight is a functional term that denotes scattered light falling on the retina as perceived by the patient. It is relative to forward light scatter and the internationally acknowledged definition of disability glare.
Methods: :
A population of 217 patients for cataract surgery was studied of mean age 72 ± 9 years (mean ±SD; range, 29-90 years). Before and after cataract extraction best corrected distance visual acuity (CDVA) according the ETDRS system, and straylight using the C-Quant from Oculus were recorded for all patients. Subjective complaints were also documented before and after surgery by the 39-item National Eye Institute Visual Function Questionnaire (NEI VFQ-39) and a home made straylight questionnaire. Data are compared to a 5000 eye database from a driver study (Am J Ophthalmol 2007;144:358-363).
Results: :
Mean pre-operative straylight was 1.55 ± 0.29 log(s) and mean CDVA was 0.28 ± 0.21 logMAR. VA and straylight show very little correlation (R² = 0.08), corresponding the driver study. Mean post-operative improvement of CDVA is 0.26 ± 0.20 log units (range, -0.12 - 1.12) and of straylight is 0.31 ± 0.32 log units (range, -0.50 -1.27). The pre-operative breakeven point for CDVA (50% chance of post-operative improvement) is at 0.06 logMAR and for straylight at 1.29 log(s). Before and after cataract extraction, questionnaires show straylight to have almost the same influence on subjective quality of vision as CDVA, as show by correlation analysis. If straylight would be included as criterion for surgery at a level of 0.5 log increase (factor 3x) an extra 99 eyes would be eligible, compared to 30 eyes with CDVA above 0.3 logMAR. If "overall vision" is defined as logMAR+log(s) an improvement of 0.3 log units is obtained if 1.5 is used as criterion value.
Conclusions: :
Implications for the clinician include a shift in targeting of patient care. On the basis of straylight elevation treatment can be offered in cases where visual acuity is good. In the case of optical malfunction of the eye, as simple model for functional severity of the condition, the sum of visual acuity in logMAR and straylight in log(s) is proposed. Data from population study on >5000 eyes show significant retargeting of cataract surgery. Straylight and VA measure different aspects of quality of vision and influence subjective visual quality almost equally. When straylight is added to pre-operative considerations of cataract extraction post-operative results are better predictable.
Clinical Trial: :
www.VCMO.nl, R-09.08O
Keywords: cataract • optical properties • quality of life