2.1. Study design and ethical issues
This study was a prospective, single-center, parallel-group, randomized controlled trial. The study protocol was approved by the institutional review board of the University of Keio. Written informed consent was obtained from each patient participating in the study. In accordance with the provisions of the Declaration of Helsinki (1995), approval was obtained from the Ethics Committee of the Keio University School of Medicine (approved on 8 July 2020, reference 20190131).
The trial was registered as a randomized controlled trial titled “The eyelid hygiene after cataract surgery” with the University hospital Medical Information Network (UMIN) registration number UMIN 000038320.
2.4. Ophthalmic examinations
All examinations were performed by masked examiners. At the initial visit before the surgery, background information, such as age, sex, underlying disease and history of ophthalmic disease, was collected. At both the pre-operation visit and post-operation visit a month after the surgery, all participants were assessed for visual acuity, FVA, meibomian gland findings, lid margin signs, corneal staining with fluorescein, central corneal thickness, axial length of their eyes and HOA. The size and location of the incision was also recorded. In addition to the preoperative and postoperative measurements, changes before and after the surgery were calculated.
Five meter best corrected visual acuity was measured and then converted to logMAR (logarithm of the minimum angle of resolution). We also performed FVA testing [AS-28, Kowa Company, Ltd., Aichi, Japan], and recorded FVA (the mean timewise change in visual acuity), maximal and minimal visual acuity during the examination, the visual maintenance ratio (the ratio of the starting visual acuity logMAR to the FVA logMAR) and average response time.
Meibomian glands were evaluated for morphological changes on the upper and lower lids with the use of a noncontact meibography system. Changes included flexion, dilatation, contraction and dropout and were expressed as a binary output: 0, absent; 1, present. The quality of expressed meibum and the degree of ease of expressing meibum was graded as: grade 0, clear fluid easily expressed; grade 1, cloudy meibum expressed with mild pressure; grade 2, cloudy meibum expressed with intermediate pressure; and grade 3, meibum could not be expressed. The dropout of meibomian glands was scored on a scale of 0 to 3 according to the area of the dropout: 0, no dropout; 1, dropout area less than one third of area; 2, between one third and two thirds of area; 3, more than two thirds of area.
Lid margin findings were also obtained using a slit-lamp microscope. Telangiectasia, irregularity, plugging and foaming was assessed on a scale from 0 to 3: 0, no findings; 1, mild findings; 2, moderate findings; and 3, severe findings. The location of the mucocutaneous junction was assessed on a scale from 0 to 3: 0, Marx line runs on the ocular side from the meibomian gland orifice; 1, Marx line partially overhanging the meibomian gland orifice; 2, Marx line runs along the meibomian orifice line; and 3, Marx line runs along the eyelid margin side of the meibomian orifice line.
After fluorescein staining of each eye, a standardized grading system of 0 to 3 was used for the auricular conjunctiva, cornea and nasal conjunctiva, and then scores were combined for a 9-point scale defined as the superficial punctate keratopathy (SPK) score. In addition to evaluation of the tear meniscus, BUT was also measured three times in each eye, and the average of the three measurements was used as the BUT.
Corneal wavefront aberrations were measured using Zernike polynomials from the topography map (OPD-Scan II, Nidek Co., Ltd., Gamagori, Japan) over a 4 mm diameter zone centered on the corneal vertex. The Zernike coefficients for corneal surface aberrations parameters from the 3rd to the 6th order were studied, and the root mean square value for the 3rd, 4th, 3rd plus 5th, 4th plus 6th, and the total HOA from the 3rd to 4th, and from 3rd to 6th were calculated.