Corneal Scatter After Cataract Surgery

After cataract surgery, corneal oedema develops to some extent in all eyes. It is of clinical importance as it increases the amount of light that is scattered by the eye. The light that is scattered backwards is what an ophthalmologist sees at the slit lamp. The light that is scattered forward is what the patient experiences as straylight. And this may limit the quality of vision for the patient. The purpose of this study was to determine changes in corneal backward scattered light after cataract surgery and assess its relationship with (total ocular) straylight.

A prospective, single-centre (Amphia, Breda, the Netherlands), single-surgeon study. This study is part of an ongoing study on the clarity characteristics of the Clareon CNA0T0 and Vivinex XY1 IOLs and investigate which parameters may affect any remaining straylight after cataract surgery. One eye is randomly selected to be implanted with a Clareon IOL; the fellow eye receives a Vivinex XY1 IOL.

We included 21 patients aged 72 ± 6 years. All patients underwent uncomplicated cataract surgery in both eyes, 2 weeks apart. Corneal densitometry was determined with the Pentacam in the central 2 mm zone and in the 2-6 mm zone. Straylight was measured with the C-Quant. Measurements were performed preoperatively, and 1 day (1D), 1 week (1W), 1 month (1M), and 3 months (3M) postoperatively. The relationship between corneal densitometry and straylight was evaluated with linear regression analysis. One eye of 1 patient was excluded from the 3M analysis because of the development of cystoid macular oedema.

Corneal densitometry (mean ± SD) in the central 2 mm zone was 20.1% ± 1.5% preop, 24.5% ± 5.6% at 1D, 20.6% ± 2.1% at 1W, 20.8% ± 2.3% at 1M, and 19.6% ± 1.3% at 3M. Corneal densitometry in the 2-6 mm zone was 21.0% ± 3.0% preop, 22.8% ± 3.6% at 1D, 21.4% ± 3.3% at 1W, 21.6% ± 3.5% at 1M, and 20.1% ± 2.3% at 3M. Straylight values (log[s]) were 1.49 ± 0.23 preop, 1.29 ± 0.23 at 1D, 1.08 ± 0.20 at 1W, 1.11 ± 0.24 at 1M, and 1.11 ± 0.22 at 3M. At 1D and at 3M, the relationship between corneal densitometry in both the 2 mm zone and the 2-6 mm zone were statistically significantly correlated with straylight measurements. The R² values were 0.31 (P 0.0001) and 0.17 (P 0.007) at 1D, and 0.17 (P 0.02) and 0.14 (P 0.04) at 3M, respectively.

After uneventful cataract surgery, both corneal backscatter in the central 2 mm zone and straylight was elevated 1 day postop and normalised at 1 week. Backscatter in the more peripheral 2-6 mm zone did not increase as much as in the 2 mm zone and normalised more gradually. The statistically significant relationship between backscattered light and forward scattered straylight at 1 day after cataract surgery may be due to swelling of the corneal stroma. Their statistically significant relationship at 3 months may exemplify a normal relationship between corneal backward and forward scatter. Efforts to reduce corneal oedema after cataract surgery may thus improve the experienced visual quality of patients in the early postoperative period.