Long-Term Natural Course of Pathologic Myopia in Chinese Patients.

PURPOSE: To investigate the natural progression in Chinese patients with pathological myopia (PM) and its associated factors. METHODS: The medical records of 28 patients with PM (worse than -6 diopter), including 31 eyes of 21 children and 12 eyes of 7 adults, were studied. All of the patients underwent a complete ophthalmologic examination at least twice over 3-year period, including the measurement of refractive error (shown as spherical equivalent, SE), axial length (AL), intraocular pressure, visual acuity (uncorrected visual acuity, UCVA, and best-corrected visual acuity, BCVA), and dilated fundus examination. RESULTS: The median AL of adults increased significantly from 29.8 mm to 31.43 mm over 5.4 years follow-up (P=0.0037), accompanied with the median SE progressing significantly from -16.4 D to -18.94 D (P=0.0005). Similarly, the median AL of children increased significantly from 26.13 mm to 27.81 mm over 3.9 years (P=0.0001). However, the improvements of UCVA and BCVA in children were significant (P=0.0304, 0.0001), and they had a negative correlation with age (P=0.0010, 0.0005). Also, UCVA and BCVA in children with bilateral PM were significantly better than those with unilateral PM (P=0.0385, 0.0210). CONCLUSIONS: Fundus degenerations in children with pathological myopia may lead its way since the age of 10 years. Besides, children with bilateral pathological myopia can have parallel development in visual acuity.

Scleral ultrastructure and biomechanical changes in rabbits after negative lens application.

AIM: To address the microstructure and biomechanical changes of the sclera of rabbits after negative lens application by spectacle frame apparatus. METHODS: Five New Zealand rabbits of seven weeks post-natal were treated with -8 D lens monocularly over the course of two weeks. Refractive errors and axial length (AXL) were measured at the 1st, 7th and 14th days of the induction period. Ultrastructure of sclera was determined with electron microscopy. Biomechanical properties were tested by an Instron 5565 universal testing machine. RESULTS: Lens-induced (LI) eyes elongated more rapidly compared with fellow eyes with AXL values of 15.56±0.14 and 15.21±0.14 mm (P<0.01). Fibril diameter was significantly smaller in the LI eyes compared with control ones in the inner, middle, and outer layers (inner layer, 63.533 vs 76.467 nm; middle layer, 92.647 vs 123.984 nm; outer layer, 86.999 vs 134.257 nm, P<0.01, respectively). In comparison with control eyes, macrophage-like cells that engulfed fibroblasts, dilated endoplasmic reticulum, and vacuoles in fibroblasts were observed in the inner and middle stroma in the LI eyes. Ultimate stress and Young's modulus were lower in the LI eyes compared with those in the control eyes. CONCLUSION: Negative lens application alters eye growth, and results in axial elongation with changes in scleral ultrastructural and mechanical properties.

[Difficulties in lenticule extraction during small incision lenticule extraction with the continuous curvilinear lenticulerrhexis technique].

OBJECTIVE: To investigate the incidence rate, classification, and management of difficulties in lenticule extraction during small incision lenticule extraction (SMILE) with the continuous curvilinear lenticulerrhexis (CCL) technique, and surgical safety and efficacy. METHODS: Retrospective study. A total of 342 continuous subjects (680 eyes) received surgical treatment by the same surgeon using the SMILE-CCL technique. The separation was performed only between the cap and anterior surface of the lenticule (8 to 2 o'clock) and at the edge between the cap and posterior surface of the lenticule (1 o'clock). The lenticule was then extracted in a clockwise motion using the CCL technique. Cases with lenticule extraction difficulties were observed through surgery videos. Classification and management of the difficulties were recorded. The rate of intact lenticule extraction was calculated. RESULTS: Twenty-two subjects (22 eyes) had lenticule extraction difficulties. The rate was 3.24%. No difficulty was found in side cut lifting. The microforceps grip loss occurred more than once in five eyes. It was difficult to separate the cap and anterior surface in 12 eyes. One eye had a microdefect in the margin of the lenticule. Five eyes were observed to have single side tearing of side cut. No eyes had double sides tearing of side cut. The microforceps were changed when grip loss occurred more than once. When there were separation difficulties, the pace of lenticule extraction was slowed down, with tearing through the tangential direction of the circle (clockwise). The conventional technique was used in three cases with severe difficulties. All lenticules were successfully extracted from the 22 eyes (100%). Uncorrected visual acuity was ≥1.0 in all eyes at 1 day after surgery. The safety index (the ratio between best corrected visual acuity at 1 month and preoperatively) was 1.11. The efficacy index (the ratio between uncorrected visual acuity at 1 month and preoperative best corrected visual acuity) was 1.04. CONCLUSIONS: Difficulties in lenticule extraction occur during SMILE-CCL with a low incidence. Various difficulties can be managed with different techniques. There are no extra effects on surgical safety and efficacy. It is safe and effective to switch back to the conventional technique when severe lenticule extraction difficulties occur.

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.

Femtosecond Laser-Assisted Corneal Small Incision Allogenic Intrastromal Lenticule Implantation in Monkeys: A Pilot Study.

PURPOSE: Lenticule implantation can be used to correct vision problems. However, it is significantly restrained by the sources of autologous lenticules. The aim of the present study was to investigate the feasibility and effects of femtosecond laser-assisted corneal small incision allogenic intrastromal lenticule implantation (AILI) in monkeys. METHODS: Six healthy adult monkeys were included in this study. Femtosecond lenticule extraction (-4.0 diopter [D] correction, 5.0-mm optical zone) was performed in one eye of two monkeys and both eyes of one monkey. Each extracted refractive lenticule was allogenically transplanted into a femtosecond laser-created corneal stromal pocket in one eye of the other two monkeys and one monkey's both eyes. Pre- and postoperative (1 or 3 days, 1 month, and 6 months) slit lamp microscopy, corneal topography, anterior segment optical coherence tomography, and in vivo confocal microscopy were performed. RESULTS: Corneal edema occurred in the early postoperative days with a large number of hyperreflective particles around the borders. Corneal tissue edema gradually decreased. Nerve fiber regeneration could be detected in the lenticule layer at 6 months. Overall, 3.27 ± 1.2 D corneal power was increased at 6 months, accounting for 82% of the intended correction. At the same time point, corneal stroma was 69 ± 11 µm thicker than preoperative ones and was roughly equal to the maximum thickness of implanted lenticules. No significant complications were observed. CONCLUSIONS: The AILI technique seems to be feasible and safe for increasing corneal stromal thickness and changing corneal refractive power, which may provide a useful method for treatment of keratoectasia, presbyopia, and hyperopia.

Influence of intraocular astigmatism on the correction of myopic astigmatism by femtosecond laser small-incision lenticule extraction.

PURPOSE: To evaluate the influence of the origin of astigmatism on the correction of myopia or myopic astigmatism by femtosecond laser small-incision lenticule extraction (SMILE). SETTING: Ophthalmology Department, Eye and ENT Hospital, Shanghai, China. DESIGN: Prospective case series. METHODS: Small-incision lenticule extraction was performed to correct myopia or myopic astigmatism. Ocular residual astigmatism (ORA) was determined by vector analysis using manifest refraction and Scheimpflug camera imaging of the anterior cornea. Patients were divided into 2 groups according to ORA (high >1.0 diopter [D]; low ≤1.0 D), and procedural efficacy was compared. Patients were examined preoperatively and 1, 3, and 6 months postoperatively. RESULTS: This study comprised 122 right eyes of 122 patients. No significant difference was found in the preoperative manifest astigmatism (target-induced astigmatism [TIA]) between the low ORA group (n = 67) and high ORA group (n = 55). The mean postoperative manifest astigmatism was higher in the high ORA group at all postoperative timepoints (1 month: t = 2.182, P=.031; 3 months: t = 2.30, P=.023; 6 months: t = 2.193, P=.03). The mean index of success (postoperative astigmatism/TIA) was 0.68 in the high ORA group and 0.34 in the low ORA group 1 month postoperatively (t = 2.531, P=.013); 0.73 and 0.39, respectively, at 3 months (t = 2.689, P=.008); and 0.77 and 0.46, respectively, at 6 months (t = 2.105, P=.037). CONCLUSION: Small-incision lenticule extraction was effective in correcting astigmatism but may be less effective in correcting ORA.

[Accommodation to monochromatic targets in people with different color vision statuses].

OBJECTIVE: To compare the accommodation response (AR) to monochromatic targets in subjects with different color vision statuses, and to investigate the role of color vision in the control of accommodation and emmetropization. METHODS: It was a case-control study. Accommodation was measured with a dynamic infrared optometer while subjects [17 protans, 47 deutans, and 23 normals; mean age: (20.0 ± 4.4) years] viewed a (1) red on black or (2) green on black vertical square-wave gratings of iso-luminance (3 cycles/deg; 0.9 contrast) in a Badal optic system. The grating stepped 1.00 D towards the eye from an initial position of 0 D until 5.00 D. RESULTS: With red-black targets, the AR in the protans (AR = 1.98 D) was worse than that in the normals (AR = 2.55 D) when the accommodation stimulus (AS) was 4.00 D (LSD, P = 0.031). The AR in the deutans were worse than that in the normals when the AS was 3.00, 4.00, and 5.00 D (3.00 D: 1.23 D vs. 1.69 D, P = 0.002; 4.00 D: 1.89 D vs. 2.55 D, P = 0.002; 5.00 D: 2.40 D vs. 3.17 D, P = 0.003). With green-black targets, the AR in the protans were worse than that in the normals when the AS was 3.00 and 4.00 D (3.00 D: 1.13 D vs. 1.61 D, P = 0.004; 4.00 D: 1.80 D vs. 2.34 D, P = 0.021). In the deutans, the AR was worse with stimuli of 3.00, 4.00, and 5.00 D (3.00 D: 1.21 D vs. 1.61 D, P = 0.003; 4.00 D: 1.65 D vs. 2.34 D, P < 0.001; 5.00 D: 2.36 D vs. 2.93 D, P = 0.007). No significant differences between the protans and deutans were found for all the stimulus conditions. In the protans, accommodation to red-black targets was better than that to green-black targets when the stimulus was 2.00, 3.00, and 5.00 D (2.00 D: t = -2.81, P = 0.013; 3.00 D: t = -4.55, P < 0.001; 5.00 D: t = -3.15, P = 0.006). In the deutans, accommodation to red-black targets was better than that to green-black targets when the stimulus was 4.00 D (t = -2.19, P = 0.034). In the normals, accommodation to red-black targets were better than that to green-black targets when the stimulus was 2.00, 4.00, and 5.00 D (2.00 D: t = -2.57, P = 0.017; 4.00 D, t = -2.67, P = 0.014; 5.00 D: t = -2.15, P = 0.043). CONCLUSIONS: Individuals with a color vision deficiency tend to have a larger accommodative lag than normals. Red targets tend to induce better accommodation response than green ones. Color vision may play a role in the control of accommodation and emmetropization.

Posterior scleral reinforcement combined with patching therapy for pre-school children with unilateral high myopia.

PURPOSE: Our purpose was to investigate the effect of posterior scleral reinforcement (PSR) combined with patching therapy for pre-school children with unilateral high myopia. METHODS: A total of 32 pre-school children with unilateral high myopia were recruited. They were randomly divided into the PSR and control group, each of which had 16 patients. The patients in the PSR group underwent the simplified PSR surgery followed by rigid gas permeable contact lens wear and traditional patching therapy, while the patients in the control group were only prescribed contact lens wear and patching. Patients were reviewed and the axial length, refraction, best-corrected visual acuity, and stereoscopic vision were respectively examined postoperatively at yearly intervals for three years. RESULTS: The best-corrected visual acuity was significantly higher in the PSR group than that in the control group at any study visit. A statistically significant difference in axial length was found between the PSR group (27.38 ± 1.30 mm) and the control group (28.29 ± 0.74 mm) at the postoperative three-year (p = 0.03) time point. There was a statistical difference in refractive error between the PSR group (-13.13 ± 2.55 D) and the control group (-15.42 ± 1.83 D) at 3-year follow-up. No significant difference was found between the two groups with respect to the stereoscopic vision by the end of follow-up at 3 years (p =0.103). CONCLUSIONS: PSR combined with the patching therapy has the potential to arrest the progression of high myopia and to help the treatment for amblyopia.

Evaluating the association between pathological myopia and SNPs in RASGRF1. ACTC1 and GJD2 genes at chromosome 15q14 and 15q25 in a Chinese population.

BACKGROUND: This study investigated the association of the 27 SNPs located in RASGRF1. GJD2, and ACTC1 genes with pathological myopia in a Chinese Han population. METHODS: Myopia patients were stratified according to whether they did (n = 274) or did not (n = 131) have myopic macular degeneration (MMD). The SNPbrowser software was used to identify specific SNPs for analysis and minimal allele frequency of >20%, and a pairwise r(2) < 0.85 were genotyped using MALDI-TOF mass spectrometry. RESULTS: Before controlling for false discovery rate, the frequency of the rs1867315 C/C genotype compared with healthy controls was lower in the myopia group (p = 0.006) and in myopia patients without macular degeneration (p = 0.019). The frequency of the rs670957A/A genotype was also lower in patients without MMD compared with controls (p = 0.045). For rs2070664, the frequency of the A allele was higher in the patients with MMD compared to those without MMD (p = 0.032). After controlling for a false discovery rate of 5%, there was no significant difference in genotype and allele frequencies between these groups. CONCLUSION: In this study, there was no association of the analyzed SNPs located in RASGRF1. GJD2, and ACTC1 with pathological myopia, suggesting that SNPs included in our study have no or a limited role in causing pathologic myopia in this Chinese Han population.

[Corneal thickness distribution and its relationship with corneal topography in ametropic population].

OBJECTIVE: To explore the distribution of relational corneal thickness parameters including central corneal thickness (CCT), thinnest pachymetry (TP), cornea thickness spatial profile (CTSP), percentage thickness increase (PTI), pachymetric progression index (PPI) and Ambrósio's relational thickness (ART) in the normal population, and their relationships with corneal astigmatism and curvature. METHODS: A total of 1 203 eyes from 1 203 normal outpatients were enrolled in this cross-sectional study. The data information of CCT, TP, CTSP, PTI, PPI-max, PPI-min, PPI-ave, axes of PPI-max and PPI-min, ART-max and ART-ave was collected from Pentacam HR for the subsequent analysis of their distribution. Astigmatism, astigmatism axis (AA), and keratometry (K) including Km and Kmax were also collected to explore their relationships with relational thickness parameters. RESULTS: The mean values for CCT and TP were (547.20 ± 31.441) µm and (543.26 ± 31.271) µm, respectively. The mean values for CTSP-2, CTSP-4, CTSP-6 and CTSP-8 were (552.11 ± 31.654) µm, (580.72 ± 32.919) µm, (632.11 ± 34.738) µm and (711.80 ± 37.880) µm, respectively. PTI-2, PTI-4, PTI-6 and PTI-8 were (1.67 ± 0.471)%, (6.89 ± 0.945)%, (16.37 ± 1.996)% and (31.10 ± 3.652)%. PPI-max, PPI-min and PPI-ave were 1.222 ± 0.175, 0.733 ± 0.138 and 0.994 ± 0.123. The axes of PPI-max and PPI-min were 230.74 ± 104.862 and 159.81 ± 62.292. ART-max and ART-ave were (454.940 ± 78.506)µm and (556.140 ± 86.492)µm. CCT, TP, PPI and ART were found to have a weak but significant correlation with Kmax-front, Km-front and Km-back. PPI and ART were also found to weakly correlate with Astig-back. The converted astigmatism axis was found to correlate with the axes of PPI-max (rs = -0.125, P = 0.000) and PPI-min (rs = 0.613, P = 0.000). CONCLUSIONS: The front and back curvatures and the back astigmatism correlate with the distribution of corneal thickness, while the front astigmatism does not correlate with it. The front astigmatism axis tends to distribute coincidently with PPI-min axis.

Upregulation of regulator of G-protein signaling 2 in the sclera of a form deprivation myopic animal model.

PURPOSE: Scleral remodeling is an important mechanism underlying the development of myopia. Atropine, an antagonist of G protein-coupled muscarinic receptors, is currently used as an off-label treatment for myopia. Regulator of G-protein signaling 2 (RGS2) functions as an intracellular selective inhibitor of muscarinic receptors. In this study we measured scleral RGS2 expression and scleral remodeling in an animal model of myopia in the presence or absence of atropine treatment. METHODS: GUINEA PIGS WERE ASSIGNED TO FOUR GROUPS: normal (free of form deprivation), form deprivation myopia (FDM) for 4 weeks, FDM treated with saline, and FDM treated with atropine. Biometric measurements were then performed. RGS2 expression levels and scleral remodeling, including scleral thickness and collagen type I expression, were compared among the four groups. RESULTS: Compared with normal eyes and contralateral control eyes, the FDM eyes had the most prominent changes in refraction, axial length, and scleral remodeling, indicating myopia. There was no significant difference between control and normal eyes. Hematoxylin and eosin staining showed that the scleral thickness was significantly thinner in the posterior pole region of FDM eyes compared to normal eyes. Real-time PCR and western blot analysis showed a significant decrease in posterior scleral collagen type I mRNA and protein expression in the FDM eyes compared to the normal eyes. The FDM eyes also had increased levels of RGS2 mRNA and protein expression in the sclera. Atropine treatment attenuated the FDM-induced changes in refraction, axial length, and scleral remodeling. Interestingly, atropine treatment significantly increased collagen type I mRNA expression but decreased RGS2 mRNA and protein expression in the sclera of the FDM eyes. CONCLUSIONS: We identified a significant RGS2 upregulation and collagen type I downregulation in the sclera of FDM eyes, which could be partially attenuated by atropine treatment. Our data suggest that targeting dysregulated RGS2 may provide a novel strategy for development of therapeutic agents to suppress myopia progression.

The sonic hedgehog signaling pathway induces myopic development by activating matrix metalloproteinase (MMP)-2 in Guinea pigs.

PURPOSE: To investigate whether the Sonic hedgehog (Shh) signaling induces myopic development by increasing the expression of matrix metalloproteinase (MMP)-2 in guinea pigs. METHODS: A translucent diffuser was glued onto the right eye to induce form-deprivation myopia (FDM) in 10 guinea pigs. Four guinea pigs were served as a control group. The other 100 guinea pigs were subdivided into 5 groups (20 per group) and received a 10 µl intravitreal injection every 2 days for 4 times. Two groups were injected with 20 or 50 µg/ml Shh amino-terminal peptide (Shh-N) into the right eye and 0.1% bovine serum albumin into the other. FDM was induced in the right eyes of the three cyclopamine-treated groups and both eyes were injected with 50, 100, or 200 µg/ml cyclopamine. Retinoscopic refraction and eye dimensions were assessed on Day 14 of treatment. MMP-2 protein expression was determined in both scleras by western blotting. RESULTS: Both concentrations of Shh-N stimulated myopic development and axial growth as compared with control eyes. Myopia and axial elongation were significantly greater in the 50 µg/ml than in the 20 µg/ml Shh-N group (P<0.001 and P = 0.0019, respectively). All three doses of cyclopamine significantly attenuated myopic development compared with the FDM group (P<0.0001). Cyclopamine at 100 or 200 µg/ml significantly reduced axial elongation compared with the FDM group (P = 0.044 and P = 0.001, respectively). FDM-induced myopia and axial elongation were significantly greater in the 50 µg/ml than in the 200 µg/ml cyclopamine group (P<0.0001 and P = 0.008, respectively). MMP-2 expression was significantly greater in Shh-N-treated eyes than in the control eyes, and was lower in the cyclopamine plus FDM groups than in the FDM group. CONCLUSIONS: The Shh signaling pathway induces myopic development by activating MMP-2 in guinea pigs.

[The key points of Chinese children myopia prevention and control].

With the development of information technology and urbanization, the prevalence of myopia in Chinese children is rising each year, meanwhile, there appears to be some cognitive and behavioral misunderstanding about the prevention and treatment of myopia now. To control the development of myopia, we should make efforts to focus on prevention of myopia, promote scientific ways of diagnosis and treatment, as well as implement integrated project.

Influence of intraocular astigmatism on the correction of myopic astigmatism by laser-assisted subepithelial keratectomy.

PURPOSE: To assess the influence of the origin of astigmatism on the correction of myopic astigmatism by laser-assisted subepithelial keratectomy (LASEK). SETTING: Ophthalmology Department, Eye and ENT Hospital, Shanghai, China. DESIGN: Prospective study. METHODS: Patients having LASEK to correct myopia or myopic astigmatism were divided into 2 groups according to their ocular residual astigmatism (ORA). Patients were examined preoperatively and 1 and 3 months postoperatively. The efficacy of LASEK was compared between those with and those without a significant amount of intraocular astigmatism. RESULTS: The study comprised 54 eyes of 54 patients. The mean index of success (ratio of magnitude of remaining uncorrected astigmatism to that of initial preoperative astigmatism) in the high ORA group (n=21) and low ORA group (n=33) was 0.85 and 0.48, respectively, 1 month after surgery (t=2.17, P=.04) and 0.88 and 0.32, respectively, 3 months after surgery (t=2.18, P=.04). The Zernike coefficient of horizontal coma, Z(3,+1), increased more after surgery in the high ORA group than in the low ORA group (1 month versus preoperative, t=2.32, P=.024; 3 months versus preoperative, t=2.07, P=.048). CONCLUSIONS: Nine percent and 2% of the eyes had minimal corneal haze at 1 month and 3 months, respectively. Laser-assisted subepithelial keratectomy was less effective in correcting myopic astigmatism when astigmatism was mainly located at the internal optics. Horizontal coma increased more after LASEK in patients with higher ORA. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

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.

Refractive change in the adult rabbit eye after corneal relaxation with the femtosecond laser.

BACKGROUND: A new procedure to correct myopia that does not disturb the cornea in the optical zone and avoids injuring the corneal epithelium could be a key advance in corneal refractive surgery. The aim of this study is to observe the refractive change in the adult rabbits undergoing femtosecond laser-assisted multilayer intrastromal ablation in the mid-periphery of the cornea without injury of epithelium. METHOD: The right eyes of 8 New Zealand White adult rabbits were used for the experiments. A 60-kHz femtosecond laser delivery system was used, and three lamellar layers of laser pulses were focused starting at a corneal depth of 180 µm and ending at 90 µm from the surface, with each successive layer placed 45 µm anterior to the previous layer. In the interface of the applanation contact lens cone, a 6-mm diameter aluminum circle was placed at the center to block the laser, limiting ablation to the mid-periphery of the cornea. The laser settings were as follows: spot/line separation, 10 µm; diameter, 8.0 mm; energy for ablating the stroma, 1.3 µJ. An authorefractor was used to assess the manifest refraction. RESULTS: Mean spherical equivalent (SE) (mean ± SD, SD: standard deviation) was significantly increased at postoperative week 1 (1.67 ± 0.26 D, p < 0.0001), month 1 (1.65 ± 0.23 D, p < 0.0001), and month 3 (1.60 ± 0.22 D, p < 0.0001) compared to baseline (0.68 ± 0.27 D). Mean spherical equivalent showed no significant change between postoperative week 1 and month 3 (p = 0.1168). CONCLUSION: Femtosecond laser-assisted multilayer corneal intrastromal ablation in the mid-periphery may cause a consequent hyperopic shift with no refractive regression.

The effect of various levels of stroboscopic illumination on the growth of guinea pig eyes.

BACKGROUND: The aim was to investigate various levels of stroboscopic illumination effect on the growth of guinea pig eyes. METHODS: Thirty-six two-week-old guinea pigs were randomised to one of three treatment groups (n = 12 for each). Two stroboscopic-reared groups were raised with a duty diurnal cycle of 50 per cent at a flash rate of 0.5 Hz. Illumination intensity varied between zero-to-250 lux or zero-to-500 lux during each cycle in each group, respectively. The third control group was exposed to 250 lux illumination. Refraction and biometric measurements were taken for each animal prior to and after two, four, six and eight weeks of treatment. Finally, retinal microstructure was examined. RESULTS: There was significant correlation between refractive errors and axial elongation. After eight weeks of treatment, illumination with flickering light 0-250 lux caused a larger myopic shift with increased axial length than illumination of continuous 250 lux. Stroboscopic illumination with zero-to-500 lux caused a further myopic shift and longer axial length than stroboscopic illumination with zero-to-250 lux. In animals raised in flickering light of zero-to-250 lux or zero-to-500 lux for eight weeks, the outer segment disc membranes in photoreceptor layers were found deformed and detached. CONCLUSION: Chronic exposure to low-frequency temporally modulated illumination-induced histological damage in the retina and induced exaggerated axial length elongation.

Transfer from blue light or green light to white light partially reverses changes in ocular refraction and anatomy of developing guinea pigs.

Relative to the broadband white light (BL), postnatal guinea pigs develop myopia in a monochromic middle-wavelength light (ML, 530 nm) environment and develop hyperopia in a monochromic short-wavelength light (SL, 430 nm) environment. We investigated whether transfer from SL or ML to BL leads to recuperation of ocular refraction and anatomy of developing guinea pigs. Two-week-old guinea pigs were given (a) SL for 20 weeks, (b) SL recuperation (SLR, SL for 10 weeks then BL for 10 weeks), (c) ML for 20 weeks, (d) ML recuperation (MLR, ML for 10 weeks then BL for 10 weeks), or (e) BL for 20 weeks. Two weeks after transfer from ML to BL (MLR group), ocular refraction increased from 1.95 ± 0.35 D to 2.58 ± 0.24 D, and vitreous length decreased from 3.48 ± 0.06 mm to 3.41 ± 0.06 mm. Two weeks after transfer from SL to BL (SLR group), ocular refraction decreased from 5.65 ± 0.61 D to 4.33 ± 0.49 D, and vitreous length increased from 3.18 ± 0.07 mm to 3.26 ± 0.11 mm. The MLR and SLR groups had final ocular refractions that were significantly different from those of the ML and SL groups at 20 weeks (ML vs. MLR: p < 0.0001; SL vs. SLR: p < 0.0001) but were still significantly different from the BL group (BL vs. MLR: p = 0.0120; BL vs. SLR: p = 0.0010). These results suggest that recuperation was not complete after return to BL for 10 weeks.

The efficacy and safety of modified Snyder-Thompson posterior scleral reinforcement in extensive high myopia of Chinese children.

BACKGROUND: To observe the efficacy and safety of modified Snyder-Thompson posterior scleral reinforcement in extensive high myopia of Chinese children. We had a retrospective design, and included a control group of children with natural progression of high myopia. METHODS: This study included 64 eyes in 41 Chinese children with extensive high myopia who underwent modified Snyder-Thompson posterior scleral reinforcement surgery (PSR group), and 17 eyes in 11 age- and myopia-matched children who wore spectacles (control group). The mean follow-up was 4.99 ± 1.3 years in the PSR group and 4.48 ± 1.3 years in the control group. Axial length, spherical equivalent (SE), uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) and fundus examinations were recorded before and after treatment, and complications were noted. RESULTS: The mean change in SE at the end of the follow-up period was 1.5 ± 1.44 diopters (D) and 3.02 ± 1.57D in the PSR and control groups respectively. These changes were equivalent to an increase in axial length of 1.27 ± 0.54 mm and 2.05 ± 0.91 mm respectively. The PSR group showed less myopic progression and less eye elongation (p < 0.001). A notable increase in UCVA was only found in the PSR group (p = 0.0001). The improvement in BCVA was significantly greater in the PSR group (p = 0.0354). There were no serious complications of PSR surgery. CONCLUSION: The modified Snyder-Thompson PSR surgery was effective and safe in controlling extensive high myopia of Chinese children.