Xiaomei Qu

Incidence of Myopia in High School Students with and without Red-Green Color Vision Deficiency

PURPOSE To investigate the influence of color vision on myopia development by testing refraction error and axial length of the eye for high school students with and without color vision deficiency (CVD). METHODS A school-based cross-sectional, cluster sample study was conducted to test the color vision and refractive error of 16,539 high school students. Students were screened for CVD using a pseudoisochromatic plate. CVD was confirmed in students failing the test using a Farnsworth-Munsell 100-Hue Test which also served to classify the subtype (protan or deutan). Three classmates of each CVD subject, matched in five myopia risk factors, were chosen to form the normal color vision (CN) control group. Ophthalmic examinations were performed to determine refractive status and axial length. RESULTS Of the students, 309 were found to have red-green CVD and 927 were selected as the CN control group. The prevalence of myopia in the CVD group (45.6%) was significantly lower than that of the CN group (65.8%; P<0.001). The CVD group was also less myopic in refraction (P<0.001) than CN, and protan subjects had shorter axial lengths than those in the control group (P=0.007). CONCLUSIONS Color vision deficiencies appear to influence the development of myopia. The observed lower incidence of myopia in people with CVD may be linked to the reduced functionality of the L/M chromatic mechanism.

Impact of pupil diameter on axial growth in orthokeratology.

Purpose. To compare axial elongation between myopic orthokeratology (OK) contact lens and spectacle wearers, and to investigate the impact of pupil diameter on axial growth in myopic children after OK treatment. Methods. Fifty-two Chinese children aged 9 to 14 years were enrolled in this study, 27 for the OK group and 25 for the single vision spectacle lenses (SVL) group. Subjects in each group were further divided into two subcategories according to their baseline scotopic pupil diameters. Axial length (AL) was measured at baseline and at every 6-month visit through to 24 months. Linear mixed-effect model was used to determine myopia progression (AL changes from baseline). In this model, repeated visits were taken as within-subject effect, and treatment group as well as pupil size were taken as between-subject effects. The interaction of treatment group*pupil size was analyzed. Relationships between axial growth at 24 months and baseline pupil area were analyzed in both lens groups. Results. Twenty-five subjects in the OK group and 22 subjects in the SVL group completed the 24-month study. AL increased significantly throughout the observed 24-month period (F = 32.09, p < 0.001). Pupil size significantly affected axial growth (F = 15.95, p < 0.001) and different treatment modalities (OK vs. SVL) interacted with the effect of pupil size on axial growth (F = 24.66, p < 0.001). To be more specific, axial growth was significantly slower in subjects with above average pupil sizes than those with below average pupil sizes in the OK group (F = 25.04, p < 0.001). Contrarily, pupil size did not affect axial growth in the SVL group (F = 0.46, p = 0.50). Baseline scotopic pupil area was significantly correlated to axial growth in the OK group (r2 = 0.405, p < 0.001) but not in the SVL group (r2 = 0.171, p = 0.056). Conclusions. Large pupil diameters facilitate the effect of OK to slow axial growth in myopia. We speculate that this is because of enhancement of the myopic shift in the peripheral retina.

Comparison of the change in posterior corneal elevation and corneal biomechanical parameters after small incision lenticule extraction and femtosecond laser-assisted LASIK for high myopia correction

PURPOSE To compare posterior corneal elevation (PCE) changes and corneal biomechanical changes post fematosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE) procedures using the Pentacam system and the Ocular Response Analyzer (ORA). DESIGN Retrospective observational case series study. METHOD 106 patients with bilateral myopia who underwent either FS-LASIK (56 patients) or SMILE (50 patients) were reviewed, only the right eye was used in the analysis. Inclusion criteria include a spherical equivalent of -6.00DS and completion of 12 months follow up. The main outcome evaluated was change in PCE at 3 months, 6 months and 12 months post-operation using the Pentacam system. Corneal biomechanical parameters were evaluated at 6 and 12 months with the ORA. RESULTS PCE change at 3 and 6 months were not significantly different between the two procedures (p=0.064, p=0.109 respectively). At 12 months, PCE change was greater in FS-LASIK than SMILE (p=0.048). One-way ANOVA showed that for either procedure, the change in PCE did not differ at 3, 6 or 12 months post operation. CH and CRF values were reduced after both procedures, with FS-LASIK demonstrating a greater reduction in CRF than SMILE at 6 and 12 months (p=0.037 and p=0.001). Both CH and CRF reduction correlated with PCE increase at 6 and 12 months. CONCLUSION FS-LASIK demonstrated a greater increase in PCE than SMILE only at 12 months, as well as a greater reduction of CRF than SMILE. There were no significant differences in PCE change over time within either group.

Dry Eye Disease following Refractive Surgery: A 12-Month Follow-Up of SMILE versus FS-LASIK in High Myopia

Purpose. To compare dry eye disease following SMILE versus FS-LASIK. Design. Prospective, nonrandomised, observational study. Patients. 90 patients undergoing refractive surgery for myopia were included. 47 eyes underwent SMILE and 43 eyes underwent FS-LASIK. Methods. Evaluation of dry eye disease was conducted preoperatively and at 1, 3, 6, and 12 months postoperatively, using the Salisbury Eye Evaluation Questionnaire (SEEQ) and TBUT. Results. TBUT reduced following SMILE at 1 and 3 months (p < 0.001) and at 1, 3, and 6 months following FS-LASIK (p < 0.001). TBUT was greater following SMILE than FS-LASIK at 3, 6, and 12 months (p < 0.001, p < 0.001, and p = 0.009, resp.). SEEQ scores increased (greater symptoms) following SMILE at 1 month (p < 0.001) and 3 months (p = 0.003) and at 1, 3, and 6 months following FS-LASIK (p < 0.001). SMILE produced lower SEEQ scores (fewer symptoms) than FS-LASIK at 1, 3, and 6 months (p < 0.001). Conclusion. SMILE produces less dry eye disease than FS-LASIK at 6 months postoperatively but demonstrates similar degrees of dry eye disease at 12 months.

The effects of monochromatic illumination on early eye development in rhesus monkeys.

PURPOSE Influence of longitudinal chromatic aberration (LCA) on emmetropization during early eye development has not been studied in primates. We investigated the effects of quasi-monochromatic lighting on refractive development and eye growth in rhesus monkeys. METHODS Infant rhesus monkeys were raised under one of three lighting conditions for 51 weeks: quasi-monochromatic blue light (peak 455 nm), red light (peak 610 nm), and white light (color temperature 5000 K). All animals underwent biometric measurements using cycloplegic streak retinoscope, keratometry, and A-scan ultrasonography for refraction, corneal power, and axial components, respectively, at designated time points. RESULTS At the 51st week, the mean difference in refraction of the white light and blue light groups, compared with that of the red light group, reached 1.71 diopters (D) and 1.43 D, respectively (both P < 0.001). Two monkeys in the red light group developed myopia at the 16th week, whereas the other seven remained hyperopic throughout the experiment. No significant difference in mean refraction was observed between the blue light group and white light group. CONCLUSIONS Illumination from long-wavelength light during early life could be a risk factor for the development of myopia in a small proportion of rhesus monkeys that are sensitive to L-cone stimulation.

Myopia screening: combining visual acuity and noncycloplegic autorefraction.

Purpose To explore the effectiveness of combining uncorrected visual acuity (UCVA) and noncycloplegic autorefraction (NCAR) for large-scale myopia screening in schoolchildren with a high prevalence of myopia. Methods A total of 1687 children aged between 6 and 12 years, from five primary schools in the Baoshan district of Shanghai participated in the study. We measured UCVA and autorefraction before and after cycloplegia by a Topcon KR-8800. We drew receiver operating characteristic curves to achieve the best cutoff points and their corresponding sensitivities and specificities for the UCVA and NCAR, respectively. We then combined the UCVA and NCAR in serial order to explore the optimal criterion and its effectiveness. A specificity of 90% was set to compare the sensitivities among the three tests. The children were divided into three age groups (aged 6 to 7, 8 to 10, 11 to 12 years) to further examine this new method. Results A total of 1639 children with an average age of 9.35 (SD, 1.6) years were finally included, among which 428 (26.11%) children were diagnosed as being myopic (spherical equivalent refraction (SER) less than or equal to −0.5 diopters [D]). For the UCVA, the cutoff point is 0.2 logarithm of the minimum angle of resolution (20/32), with a sensitivity and specificity of 63.6% and 94.0%, respectively. For NCAR, the cutoff point is SER less than or equal to −0.75 D, with a sensitivity and specificity of 88.6% and 86.1%, respectively. When UCVA is combined with NCAR, the best cutoff point is UCVA less than or equal to 0 logarithm of the minimum angle of resolution (20/20) and SER less than or equal to −0.75 D, with a sensitivity and specificity of 84.4% and 90.5%, respectively. At a specificity of 90%, the sensitivities are 63.55%, 78.50%, and 84.35%, respectively, for UCVA, NCAR, and the combination test. In all age groups, the combination test had the highest sensitivities among the three tests. Conclusions In a population with a high prevalence of myopia, combining the UCVA and NCAR in serial order achieved higher sensitivity than either of the two tests alone, when specificity was set at 90%.

Near Work Related Behaviors Associated with Myopic Shifts among Primary School Students in the Jiading District of Shanghai: A School-Based One-Year Cohort Study

Purpose To investigate the characteristics of various near work related behaviors among primary students and their associations with changes in myopia related ocular biometric parameters during one-year of follow up. Methods A school-based sample of 4,814 primary 1st to 4th grade students aged 6–10 years old were selected by cluster randomization based on probability proportion to size in 2013. At baseline, students together with their parents filled in a self-administered questionnaire on 9 aspects of near work related behaviors and some important covariants of myopia. A comprehensive set of eye examinations including axial length (AL) and cycloplegic refraction was conducted both at baseline and one year later. Results With the grade level increase, students did increasingly better at finding various ways to have an eye break, but they were increasingly likely to continuously do long-time near work without an eye break. Keeping a reasonable eye distance and correct hand posture for reading, writing, or watching TV became worse for the first time before grade 2, but then became better at grade 3. In contrast, selecting appropriate lighting environments or situations and keeping a balanced diet became better for the first time before grade 2, but then became worse at grade 3. At one-year follow up, the mean AL increased by 0.32 ± 0.35 mm, the ratio of AL divided by the mean corneal radius of curvature (AL/CR ratio) increased by 0.032 ± 0.054, the myopic spherical equivalent (SE) increased by -0.51 ± 0.51 diopters and the incidence of myopia was 16.0% (237/1,477). After controlling for the confounding effects of parental myopia, student’s age, gender, height, daily near work time, daily outdoor activity time and all of the other near work related behaviors, keeping a reasonable distance when reading, writing and watching TV was associated with elongation of the AL [standard coefficient beta = -0.062, P = 0.004], a change in SE [beta = -0.072, P = 0.020] and incident myopia [adjusted odds ratio (aOR) = 0.90, 95% confidence interval (CI): 0.84–0.96]. Selecting an environment with adequate light for visual comfort to read and write was related to elongation of the AL [beta = -0.039, P = 0.034] and increase of AL/CR ratio [beta = -0.030, P = 0.048]. Also, not continuing to do near work for more than 30–40 minutes without an eye break was related to increase of the AL/CR ratio [beta = -0.028, P = 0.044] and a change in SE [beta = -0.064, P = 0.023]. Conclusion Various near work related behaviors changed according to grade level in primary school students. Independent of hereditary factors, daily near work load and outdoor activity, near work related behaviors such as keeping an inappropriate eye distance for near work, selecting inadequate lighting environments, and continuing to do near work without an eye break were risk factors for myopic shifts.

Effects of Orthokeratology on Choroidal Thickness and Axial Length.

Purpose To investigate the effect of orthokeratology (ortho-k) treatment on choroidal thickness and its relationship with axial length change. Methods Seventy-seven myopic subjects aged between 7 and 17 years were treated with ortho-k lenses (n = 39) or single-vision spectacle lenses (SVL, n = 38). Choroidal thickness and axial length measurements were taken at baseline and repeated 1 week and 3 weeks after lens wear for the ortho-k group and at 3 weeks for the SVL group. Parafoveal choroidal thickness was assessed using optical coherence tomography and segmented into nine regions according to the Early Treatment Diabetic Retinopathy Study (ETDRS) within a 6 × 6 mm circular zone centered on the fovea. Axial length was measured using partial coherence interferometry. The changes in subfoveal choroidal thickness were compared to the changes in axial length in both study groups. Results The change in axial length was significantly correlated with the change in choroidal thickness in both groups at 3 weeks (ortho-k, r = −0.351, p = 0.028 vs. SVL, r = −0.408, p = 0.011). Parafoveal choroidal thickness increased after 3 weeks of lens wear in the ortho-k group (mean, 21.8 ± 25.2 &mgr;m) but did not change in the SVL group (mean, 0.1 ± 19.7 &mgr;m). Choroidal thickness significantly varied across the posterior retinal regions (F = 82.14, p < 0.001), with the temporal regions being thickest and nasal regions being thinnest. After 3 weeks of ortho-k treatment, the magnitude of change (range, 14.1–27.6 &mgr;m) in choroidal thickness of the nine ETDRS regions was proportional to the baseline choroidal thickness in those regions (r = 0.88, p = 0.002). Axial length did not significantly change over time (F = 0.001, p = 0.975) and did not differ between the two treatment modalities (F = 0.305, p = 0.582). Conclusions Choroidal thickness increases after short-term ortho-k treatment. Regional choroidal thickening after ortho-k treatment may be attributable to the altered retinal defocus profile associated with ortho-k lens wear.

Regional Macular Light Sensitivity Changes in Myopic Chinese Adults: An MP1 Study

PURPOSE To investigate the variation of macular light sensitivity (MLS) in myopic Chinese adults by using microperimetry. METHODS MLS was recorded with the MP1 microperimeter (Nidek Technologies, Padova, Italy) in eyes affected by various degrees of myopia. Subjects were divided into group A (18-30 years) and group B (31-60 years). Subjects in both age groups were further divided based on refractive status: (1) high myopia (spherical equivalent, SE<-6.00 D); (2) low to moderate myopia (-6.00 D<or=SE<or=-1.00 D); and (3) no myopia (-1.00 D<SE<or=+0.50). All patients had corrected visual acuity greater than 20/20. The macular area covered by the MP1 grid contains nine areas. MLS was quantified in each part and correlated with the refractive data. RESULTS MLS correlated significantly with SE or axial length (AL). Average MLS of the outer ring, total macula, and superior quadrant significantly decreased in the high and the low to moderate myopia eyes (both P<0.05) in both age groups. MLS in the temporal, inferior, and nasal quadrants decreased in the high myopia eyes, but not in the low to moderate myopia eyes, except in the temporal quadrant in group A and in the nasal quadrant in group B. CONCLUSIONS Axial myopia was associated with reduced total and quadrant-specific MLS, particularly in the superior quadrant. These findings emphasize functional differences in the macula between high, low to moderate, and no myopia. Any evaluation of MLS by MP1 microperimetry in the macula should be interpreted in the context of the degree of refractive error and the region of measurement.

Pachymetry Map of Corneal Epithelium in Children Wearing Orthokeratology Contact Lenses

Abstract Purpose: To study the pachymetry map of the corneal epithelium in children wearing orthokeratology lenses automatically generated by a Fourier-domain optical coherence tomography. Materials and Method: The study was conducted on 60 children who had been fitted with myopic orthokeratology lenses. Patients were divided into two groups according to the duration of OK lens treatment (group 1: ≤14 days, n = 28; group 2: >14 days, n = 32). The control group consisted of 44 children. An FD-OCT device with a pachymetry module was used to map the central 6-mm corneal epithelial thickness. An epithelial thickness map was automatically generated and divided into three zones: central 2 mm, paracentral 2 to 5 mm (P1) and mid-peripheral 5 to 6 mm (P2). The average epithelial thickness of central (C), the temporal (T1), nasal (N1), superior (S1) and inferior (I1) sectors of P1, and the temporal (T2), nasal (N2), superior (S2) and inferior (I2) sectors of P2 were recorded and compared. The minimum and maximum points of epithelial thickness across the map were also recorded. Munnerlyn’s formula was used to model the expected change in refractive error based on Δ(Max-Min) (Δ(Max-Min) = (Max-Min)study-(Max-Min) mean of control). Results: The central epithelial thickness was significantly different between individual groups and a significant difference from the control (Group 0) was seen in each treatment group. Both the epithelial thickness measurements of T1 and I1 were thinnest in Group 1. Both the epithelial thickness measurements of S2 and I2 were thickest in Group 2. The difference between maximum and minimum thickness was significantly different between groups with the largest effect in Group 2. The refractive changes predicted by Munnerlyn’s formula were less than the actual refractive changes measured in both study groups. Conclusions: The epithelial thickness map automatically generated by FD-OCT can provide regional information about corneal epithelium thickness following overnight wearing of OK lenses.