The Study Of The Changes In Optical Quality And The Intraocular Scattering In Myopic Children After Orthokeratology

PurposeTo evaluatethe repeatability of OQAS II(optical quality analysis system) in optical quality measurements of myopic children; To objectively evaluate the changes of optical quality and intraocular scattering in myopic children aged 8 to 16 years after orthokeratology with a double-pass instrument(OQAS II). MethodsThis prospective study randomly recruited 32 myopia children(57 eyes, 32 right eyes, 25 left eyes, 16 men, 16 women) with spherical equivalent of range from-1.00 to-5.75 diopters(-3.77±1.78 D) and less than-1.50 astigmatism(-0.45±0.57 D) with orthokeratology. Before orthokeratology, using OQAS, all patients need to be measured thriceby the same experienced operator. And the interval time was 5 minutes between each measurement. The patients were also measured on 7 days, 1 month and 3 months after the orthokeratology. We quantitatively assessed the values of MTF cutoff frequency, objective scattering index(OSI), and OQAS values(OVs), using an Optical Quality Analysis System for a 4 mm pupil.The statistics analysis used SPSS 22.0(IBM,USA). The data of 32 right eyes was analyzed for the repeatability of OQASII(optical quality analysis system) in optical quality measurements of myopic children. Three repeated consecutive measurements were completed by the same examiner. The parameters, includingthe within-subject standard deviations(Sw), the within-subject coefficient of variation(CVw), the intraclass correlation coefficient(ICC), the coefficient of reproducibility(CR), the relative repeatability(RR), were used to analyze the repeatability. The ICC was determined on the basis of analysis of variance for two-way mixed-effects model with an absolute agreement for consistency of individual measurements. The data of 57 right eyes with orthokeratology was analyzed to objectively evaluate the changes in optical quality and the intraocular scattering in myopic children. The paired t-test was used for the change of optical quality between pre-orthokeratology and post-orthokeratology. The Pearson correlation analysis was used for the correlation between MTF cutoff frequency and axial length, MTF cutoff frequency and axial length,OSIand axial length, OSI and axial length,MTF cutoff frequency and OSI,respectively.The P<0.05 means statistical significance. Results1. Using OQAS,Mean values for parameters of the optical quality and the intraocular scattering in myopia children( age: 8-16 years) : MTF cutoff :30.97±12.49 cpd, OSI : 0.80±0.82, OV100% : 1.03±0.30, OV20% :1.04±0.33,OV9%:1.11±0.36.The following are the parameters of repeatability:the intraclass correlation coefficients(MTF cutoff:0.96,OSI:0.97,OV100%:0.94, OV20% : 0.94, OV9% : 0.93), the within-subject coefficient of variation(MTF cutoff : 0.08, OSI : 0.18, OV100% : 0.08, OV20% : 0.08,OV9%:0.09);the coefficient of reproducibility(MTF cutoff:6.83,OSI:0.39,OV100%:0.21,OV20%:0.23,OV9%:0.26),the relative repeatability(MTF cutoff:0.22,OSI:0.49,OV100%:0.21,OV20%:0.22,OV9%:0.24).2. Compared to the pre-treatment, MTF cutoff frequency(pre-orthokeratology 30.13±11.45 cpd, post-orthokeratology 7 days 23.33±6.58 cpd, post-orthokeratology onemonth 22.52±7.11cpd) and OV100%(pre-orthokeratology 1.01±0.29, postorthokeratology 7 days 0.81±0.21,post-orthokeratology onemonth 0.85±0.18), OV20%(pre-orthokeratology 1.06±0.33, post-orthokeratology 7 days 0.87±0.22, post-orthokeratology one month 0.89±0.20), OV9%(pre-orthokeratology 1.14±0.37, post-orthokeratology 7 days 0.88±0.23, post-orthokeratology onemonth 0.92±0.22), OVave(pre-orthokeratology 1.07±0.32, post-orthokeratology 7 days 0.85±0.21, post-orthokeratology onemonth 0.89±0.21) decreased and OSI(preorthokeratology 0.84±0.85, post-orthokeratology 7 days 1.25±0.75, postorthokeratology onemonth 1.26±0.90) increased after orthokeratology 7 days and 1 month(p<0.01). However, there was no significant difference between preorthokeratology and post-orthokeratology 3 months(post-orthokeratology threemonths MTF 30.59±5.23 cpd, OV100% 0.98±0.24, OV20% 1.04±0.27, OV9% 1.10±0.32, OVave 1.04±0.27, OSI 0.71±0.36, p>0.05).We found a significant negative correlation between MTF cutoff frequency of the pre-treatment and OSI(r=-0.660,p<0.001), but no significant correlationbetween MTF cutoff frequency of the pre-treatment and axial length(r=-0.257, p=0.054), as well as MTF cutoff frequency of the pre-treatment and pupil size(r=-0.061, p=0.65).Furthermore, we found a significant positive correlation between OSI of the pre-treatmentand axial length(r=0.298,p=0.024), but no significant correlation between OSI of the pretreatment and pupil size(r=0.052, p=0.703). ConclusionOQAS-II demonstrated good repeatability of the optical quality measurement in myopia children. There is a decrease in optical quality in orthokeratology patients at early period of treatment of 7 days and 1 month. However, there was no significant difference between pre-treatment and post-treatment at 3 months.