DE is characterized by symptoms of ocular dryness and discomfort, which can affect the visual performance. We conducted the present study to assess changes of wavefront aberrations and corneal surface regularity in DE patients measured with OPD Scan III. The comparisons between DE patients and normal subjects were performed and we also investigated the correlations between wavefront aberration parameters, corneal surface regularity parameters and ocular surface parameters respectively.
Visual disturbance is a main symptom of DE patients and common visual complaints associated with DE include fluctuating vision with blinking, blurred vision, glare and eye fatigue[6, 19]. In our study, logMAR BCVA was significantly higher in DE group than normal group. Besides, the logMAR BCVA positive correlated to all the wavefront aberration parameters and corneal surface regularity parameters which confirmed that the main courses of visual disturbance in DE patients could be tear film instability and ocular surface damage.
The stability of tear film plays an important role in the condition of visual performance. Change in optical aberrations created by tear-film breakup contributes to the reduction in retinal image quality. This alteration in the visual performance is directly related to increased optical HOA and a direct link has been demonstrated between severity of the dry eye and the level of HOA. TBUT is represented the tear film stability and previous study showed changes in some Zernike aberrations such as vertical coma and SA after blinking are associated with the changes in tear menisci and TBUT. In our study, the wavefront aberrations parameters measured with OPD Scan III including total corneal aberrations, HOAs, coma, trefoil and SA in DE group were all significantly higher than in normal group. Besides TBUT had a strong negative correlation with SA and moderate negative correlations with total corneal aberrations and coma.
The SRI and SAI measured by corneal topography have been shown to be significantly worse in patients with DE than in normal subjects. The results of our study were consistent with previous study. Besides, it showed that the CFS scores as well as central CFS scores did not correlate with wavefront aberration parameters while they are correlated well with SRI and SAI. In clinical practice, fluorescein dye is frequently used for ocular staining, and dry eye commonly appears as positive corneal fluorescein staining which showed corneal surface irregularity in these areas and associated with SRI and SAI.
According to the study, tear film instability and ocular surface damage are thought to be main courses of visual disturbance which resulted in the increased wavefront aberrations and corneal surface irregularity. However, few study focused on evaluating both wavefront aberrations and corneal surface irregularity in DE patients. OPD Scan III is a multifunctional device that measures the shape and curvature of the cornea and wavefront aberrations which could provide more comprehensive evaluations for DE patients and might have potential to evaluate the severity of DE or monitor the treatment of DE.
There are some limitations in current study. The sample size is small and further larger sample study is still needed in the future. There are lots of parameters from OPD Scan III examinations and we only evaluated the wavefront aberrations and corneal surface regularity parameters and others might need be further investigated.
In conclusion, the wavefront aberrations and corneal surface irregularity are increased in DE patients. The OPD Scan III might have potential to be a new instrument to evaluate the severity of DE and monitor the treatment of DE in clinical.