To compare intraocular straylight in normal and cataractous eyes as the morphology and to compare straylight as the result of subjective symptoms in early cataract cases using the C-quant straylight meter, the only tool to measure light scattering in media.

Straylight values were measured in 217 normal eyes and 138 cataractous eyes. Cataractous eyes were classified into posterior subcapsular opacity, anterior subcapsular opacity and nucleosclerosis. Straylight values of each group were measured. The 56 early cataractous eyes were categorized into two groups, depending on the presence of subjective symptoms, and each straylight value was measured. The preoperative and postoperative straylight values of early cataracts were also compared.

The mean straylight values of normal and cataractous eyes were 1.34 and 2.46, respectively. The value of posterior subcapsular opacity (2.81) was significantly higher than that of anterior subcapsular opacity (2.33) and nucleosclerosis (1.99). The straylight values of early cataracts were significantly higher in the group with subjective symptoms (2.02) than in the group without subjective symptoms (1.56). The postoperative straylight value decreased to 1.42.

The posterior subcapsular cataract showed significantly high intraocular straylight, indicating that light scattering occurred to a greater extent in this group. Light scattering occurred more in early cataractous eyes with subjective symptoms than in eyes without symptoms, and light scattering was reduced after surgery. The C-quant straylight meter, which measures the light scattering in media, can be a useful tool to determine the time of cataract surgery and to evaluate the quality of vision.