|
nif:isString
|
-
This prospective main study, as well as the complementary prestudy, was carried out at the University of Tuebingen. The study protocols followed the Declaration of Helsinki 1964 and following amendments, as well as the data protection regulations. The study was approved by the ethics committee of the Faculty of Medicine of the University Tuebingen. Written informed consent was obtained from all subjects prior to the measurements. Participants between 18 and 35 years of age were included, with a spherical equivalent refraction (SE) between 1.00 D and 6.00 D, maximal cylindrical power of (+ or -) 1.00 D and visual acuity of 0.1 logMAR or better, when corrected with the SE only. Furthermore, Bruch’s membrane and the choroidal-scleral interface in the optical coherence tomography (OCT) scan had to be sufficiently detectable to ensure a correct analysis of the choroidal thickness (ChT) of the OCT scan by the automated choroid segmentation. Hereby, the intrasubject repeatability of the measurements had to be 15 μm or better as an additional inclusion criterion, since this was the limit for qualitative good choroid segmentation, as observed in the small subset of the first complementary study.
Table 1 lists the types and parameters of the applied contact lenses. The defocus power and multifocal addition were each +2.50 D based on the subject’s individual refraction. The Proclear Multifocal ‘D’ (MFD) lens has a center-distance design with a 2.3 mm diameter zone of distance correction. In the progressive zone, up to 8.5 mm diameter, the power slowly increases until it reaches the full addition power. The outermost ring has no optical effect because it lies outside the pupil [7, 17]. In contrast, the Proclear Multifocal ‘N’ (MFN) lens is structured oppositely with a central ring that consists of the maximum addition power and a progressive power decrease to the distance correction within the transition zone [17]. Both monofocal contact lenses, one with distance correction (SVDC) and one with a full-field undercorrection (SVDF), were used as a comparison to the multifocal contact lenses.
Table data removed from full text. Table identifier and caption: 10.1371/journal.pone.0207637.t001 Applied contact lenses with parameters. Abbreviations of the contact lenses in brackets in the first row are used hereinafter in the text.
The protocol of the main study consisted of OCT scans (CIRRUS HD-OCT 5000, Carl Zeiss Meditec Inc., Dublin, CA, USA) and biometry measurements (IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany) before and after 30 min of wearing each of the four different contact lenses. In addition, peripheral refraction profiles in primary gaze were obtained using photorefraction. The refractor used a moving mirror to measure refractive errors of both vertical and horizontal meridians out to an eccentricity of ±50° nasally and temporally as described previously [18]. The fixation target for peripheral refraction was mounted at a distance of 3.50 m. The lenses were worn in the right eye, while the left eye was fully corrected for distance with a trial frame and served as the control eye. After each contact lens was worn for 30 min, OCT and biometry scans were performed three times on both eyes, whereas peripheral refraction was performed six times on the right eye only. A 15 min wash-out period with trial frame correction on both eyes was executed between the single contact lenses. The study procedure is shown in Fig 1. During each round of contact lens wear, subjects watched a movie at a distance of 4.50 m (diagonal screen size 55”) in a room illuminated with 25 lux, to ensure a pupil size of at least 5 mm. The order of contact lenses, as well as the order of the devices used for the described measurements, were randomized. The anterior segment picture of the IOLMaster 700 was used for the control of the contact lens centration on the eye. All participants were scheduled between 1 pm and 3 pm, to diminish intersubject differences in ChT changes due to the diurnal choroidal rhythm [19, 20].
Figure data removed from full text. Figure identifier and caption: 10.1371/journal.pone.0207637.g001 Study procedure of the main study.Subjects underwent OCT and biometry measurements before and after 30 min of contact lens wear. This was followed by a 15 min wash-out period with trial frame correction. The procedure was repeated for each of the four contact lenses. The left eye was constantly wearing trial frame correction while undergoing the same measurements at the same time points as the right eye.
Choroidal segmentation and thickness analyses were performed automatically with custom MATLAB (MATLAB 2017b, The MathWorks, Inc., Natick, MA, USA) software for choroid segmentation [21]. The obtained 6x6 mm2 Macular Cube OCT scan was presented as a squared 2D-matrix, which consisted of single values representing the choroidal thickness of every pixel location in the cubic scan. This map of three averaged measurements was used for the choroidal thickness analysis and was further sectioned into the nine ETDRS fields within MATLAB. The foveola, with its corresponding subfoveal thickness values, was therefore set into the center of the 6x6 mm2 OCT scan, as well as in the corresponding segmentation matrix. The OCT scan area covered a retinal angle of 20° for an axial length of 24 mm. In addition to the built-in eye tracking software, the pixel values around the foveola were averaged with the size of a regular microsaccade [22] for the calculation of subfoveal choroidal thickness. To obtain the difference in choroidal thickness from the corresponding baseline measurement (three averaged measurements each), the values before contact lens wear were subtracted from the values after contact lens wear. Positive numeric values indicate an increase in ChT, whereas negative values indicate a decrease. For each subject, the differences in choroidal thickness of one ETDRS region in the right eye were compared to the corresponding values of the same region in the left eye (control eye). Statistical analysis in MATLAB consisted of the Kruskal-Wallis test, which represents the nonparametric version of the one-way ANOVA. Vitreous chamber depth was calculated in Excel (Microsoft Excel 2013, Microsoft Corporation, Redmond, WA, USA) by subtracting the corneal thickness, anterior chamber depth and lens thickness from the axial length. The normally distributed differences between treated and control eyes were compared with one-way ANOVA. For the analysis of peripheral refraction, the mean of the dioptric values in the horizontal and vertical meridian were taken as SE at each angle point in steps of 0.71° for ± 50° from the fovea. The corresponding values of at least six scans were averaged, to obtain the refractive profile of the uncorrected eye. The adjustment of the critical p-value for all analyses was performed with the Benjamini & Hochberg / Yekutieli familywise error posthoc correction [23].
Within a small subset of n = 3 subjects, a complementary prestudy was conducted. Materials, measurement devices and data analysis modalities were the same as described in the main protocol, except for the ETDRS grid, since only the 1 mm central field was evaluated in this study. Subjects’ choroidal thickness of both eyes was measured on three separate days in 2 h intervals between 9 am and 5 pm while wearing regular spectacle distance correction lenses during the day. The purpose was to define the time of the day when the choroid thins in its diurnal rhythm for the scheduling of the participants. On two additional days, the subset wore each of the multifocal contact lenses on both eyes to estimate the maximal effect size of choroidal thickness change with multifocal contact lenses after day-long wear compared to a shorter 30 min exposure in the main study protocol.
|
![[This page as RDF]](http://data.gesis.org/somesci/static/rdf-icon.gif){kind=icon}