Ocular Forward Light Scattering and Corneal Backward Light Scattering in Patients With Dry Eye

PURPOSE. To evaluate ocular forward light scattering and corneal backward light scattering in patients with dry eye. METHODS. Thirty-five eyes in 35 patients with dry eye and 20 eyes of 20 healthy control subjects were enrolled. The 35 dry eyes were classified into two groups according to whether superficial punctate keratopathy in the central 6-mm corneal zone (cSPK) was present or not. Ocular forward light scattering was quantified with a straylight meter. Corneal backward light scattering from the anterior, middle, and posterior corneal parts was assessed with a corneal densitometry program using the Scheimpflug imaging system. RESULTS. Both dry eye groups had significantly higher intraocular forward light scattering than the control group (both P < 0.05). The dry eye group with cSPK had significantly higher values in anterior and total corneal backward light scattering than the other two groups. Moderate positive correlations were observed between the cSPK score and corneal backward light scattering from the anterior cornea (R = 0.60, P < 0.001) and corneal backward light scattering from the total cornea (R = 0.54, P < 0.001); however, no correlation was found between cSPK score and ocular forward light scattering (R = 0.01, P = 0.932). CONCLUSIONS. Ocular forward light scattering and corneal backward light scattering from the anterior cornea were greater in dry eyes than in normal eyes. Increased corneal backward light scattering in dry eye at least partially results from cSPK overlying the optical zone.