Optical Quality and Levels of Tear Protein Lacritin After PRK
Narrative Responses:
Purpose
To determine whether tear protein lacritin affects optical quality following photorefractive keratectomy (PRK).
Methods
This is a prospective study of 52 myopic patients undergoing PRK. After epithelial debridement, photoablation was performed with the Wavelight Allegretto Wave EyeQ excimer laser (Alcon Surgical). Visual acuity, manifest refraction and TMS-4 (Tomey) surface regularity index (SRI), surface asymmetry index (SAI), and irregular astigmatism index (IAI) were determined preoperatively and postoperatively. Tear samples were collected preoperatively and day 1, week 1, months (M) 1 and 3 postoperatively. Lacritin concentration was determined using enzyme linked immunosorbent assay (ELISA). Multivariate analysis of variance was performed to determine if lacritin had any significant effect on optical quality indices after PRK.
Results
Mean manifest spherical equivalent was -2.86±1.70 diopters and mean ablation depth was 46.2±21.6µm. Lacritin concentration decreased significantly from preop (12.1±2.6 average %) at day 1 postop (10.4±4.4 ave. %, p=0.03) then increased significantly from day 1 to week 1 postop (12.7±2.6 ave. %, p<0.01). Ablation depth was associated with lacritin concentration at 1M postop (B coefficient = 0.23, p=0.04). Postoperative SAI and IAI changed significantly over time (p<0.01) while SRI did not (p=0.76). Lacritin did not have any significant affect on TMS indices at preop (p=0.20) or at 1M (p=0.70) and 3M postop (p=0.78).
Conclusion
Initial results showed lacritin levels did not affect optical quality, as measured by TMS indices.