Objective and subjective evaluation of dysphotopsia in normal and post-operative eyes

Abstract

The principle theme of this thesis is the measurement of dysphotopsia, a common complaint in both the ageing population and after cataract or refractive surgery. Despite the availability of multiple objective and subjective methods to measure dysphotopsia, no single method is in common use, nor are photic effects commonly measured prior to cataract or refractives urgery. In this thesis, objective measures are taken using the Aston halometer and C-Quant, whilst subjective complaints are graded using simulated images. Whilst many previously published studies have reported monocular halometry results, an early study in the thesis found monocular halo areas to be approximately 30 % larger (P < 0.001) than the binocular area, indicating the effect of binocular summation on objective measures of halo area. The thesis investigates the link between objective measures and subjective complaints of dysphotopsia. Subjective complaints were not linked to binocular halo area (P = 0.478), monocular halo area (P = 0.896) or C-Quant straylight values(P = 0.128). Halometry and C-Quant also showed no relationship (P = 0.229). The results highlight the difficulties in being able to predict the potential subjective complaints a patient may experience from objective measures alone. However, a weak correlation was found between binocular halo area and subjective night halo complaints (rs = 0.330, rs2 = 0.109, P < 0.001), which may be due to the fact that halo area assessed would relate directly to the night halo image on the photographic images of photic phenomena (PIPP) plates. Binocular and monocular halo areas both increased with age (rs = 0.449, rs2 = 0.202, P < 0.001 and rs = 0.403, rs2 = 0.162, P < 0.001, respectively) in healthy eyes (n = 141, age range 18 – 82 years). Retinal straylight values also increased significantly with age (rs = 0.457, rs2 = 0.209, P < 0.001), as did subjective grading (rs = 0.314, rs2 = 0.099, P < 0.001). The results indicate a significant age-related increase in dysphotopsia, even in healthy eyes, which is attributed to media changes over time. Due to the effects of a bright light source on the pupil size, and the issue of senile miosis, this programme of research considered, for the first time, whether pupil size had an effect on the size of the halo area measured with halometry. No significant difference in halo area with various simulated pupil sizes (4.5, 6.0 and 7.5 mm) was detected (χ2(3) = 7.56, P = 0.056). The Aston halometer is therefore a robust way to evaluate dysphotopsia without measuring or controlling pupil size. A longitudinal study tracked photic effects in individuals for a year after laser-assisted in situ keratomileusis, and another measured dysphotopsia pre- and up to a year post-cataract surgery. Subjective complaints resolved by 3 months post-refractive surgery, objective halo area took 6 months to resolve post cataract surgery and up to 12 months post-corneal refractive surgery. A glare effect ratio was calculated for binocular halometry (median = 1.28; IQR 0.75 – 2.15) and retinal straylight (median = 5.63; IQR 2.72 – 7.97). The glare effect ratio is independent of age, and it is suggested that the glare effect ratio could be used to identify individuals most at risk of significant subjective complaints of dysphotopsia following procedures such as corneal refractive surgery.