Co-option of the limb patterning program in cephalopod eye development

Background Across the Metazoa, similar genetic programs are found in the development of analogous, independently evolved, morphological features. The functional significance of this reuse and the underlying mechanisms of co-option remain unclear. Cephalopods have evolved a highly acute visual system with a cup-shaped retina and a novel refractive lens in the anterior, important for a number of sophisticated behaviors including predation, mating, and camouflage. Almost nothing is known about the molecular-genetics of lens development in the cephalopod. Results Here we identify the co-option of the canonical bilaterian limb patterning program during cephalopod lens development, a functionally unrelated structure. We show radial expression of transcription factors SP6-9/sp1, Dlx/dll, Pbx/exd, Meis/hth, and a Prdl homolog in the squid Doryteuthis pealeii, similar to expression required in Drosophila limb development. We assess the role of Wnt signaling in the cephalopod lens, a positive regulator in the developing Drosophila limb, and find the regulatory relationship reversed, with ectopic Wnt signaling leading to lens loss. Conclusion This regulatory divergence suggests that duplication of SP6-9 in cephalopods may mediate the co-option of the limb patterning program. Thus, our study suggests that this program could perform a more universal developmental function in radial patterning and highlights how canonical genetic programs are repurposed in novel structures.

Auswirkungen auf den vorderen Augenabschnitt beim Andocken eines Femtosekundenlasers an das Patienteninterface

Purpose. To compare the intraoperative OCT (optical coherence tomographer) of the femtosecond laser LenSx (Alcon Pharma GmbH, Freiburg) with a Scheimpflug-tomographer and an anterior segment OCT and thus to investigate a possible influence on the anterior segment of the eye when docking the patient’s interface. Material and Methods. A prospective cross-sectional study was conducted with 57 subjects who underwent a planned femtosecond laser-assisted cataract surgery or refractive lens exchange. The eye to be operated on was measured prior to the operation in mydriasis with the Visante OCT (Carl Zeiss Meditec AG, Jena) and the Pentacam AXL (Oculus Optikgeräte GmbH, Wetzlar). During the surgery, images of the anterior segment of the eye were taken by the integrated intraoperative OCT of the laser, which were evaluated afterwards and compared to the values of the other devices. The parameters examined were the internal anterior chamber depth (ACD), nasal and temporal chamber angles, central corneal thickness (CCT) and central lens thickness (LT). Results. The comparison of the intraoperative OCT and the two other devices showed clinically relevant differences in all parameters. The intraoperative OCT showed a 9.19 ± 27.55 μm larger CCT, 0.96 mm (median difference) larger LT, 0.05 mm smaller ACD than the Pentacam AXL and a 21.36 ± 25.50 μm larger CCT, 0.10 mm (median difference) smaller ACD than the Visante OCT. Conclusion. The comparison of the intraoperative OCT with the Visante OCT and the Pentacam AXL shows clinically relevant differences. Changes in the anterior segment of the eye may be due to errors in measurement or docking of the patient’s interface. Keywords. femtosecond laser, OCT, anterior segment of the eye, cataract surgery, refractive lens exchange

Assessment of Biosafety and Implantation Feasibility of Novel Phakic Refractive Lens

Purpose: To investigate the biosafety and implantation feasibility of newly developed phakic refractive lens (PRL) in rabbit eyes. Methods: The PRLs, including short PRL (S-PRL), large PRL (L-PRL), and large grooved PRL (LG-PRL), were prepared by molding liquid medical silicon. The in vitro cytotoxicity of the above PRLs was evaluated by incubating them with human lens epithelial cells (HLECs) and then measuring cell viability by CCK-8 assay. In vitro cell adhesion of PRLs was assessed by culturing HLECs on PRL film surface and calculating the cell number and average cell area after stained with Calcein-AM and fluorescent. The implantation feasibility was appraised by observing the relative positions of S-PRL, L-PRL or LG-PRL implanted in the posterior chamber of rabbit eyes by optical coherence tomography, and calculating their retention ratio postoperatively. The intraocular pressure (IOP) of S-PRL, L-PRL, LG-PRL and control groups of rabbit eyes was compared to evaluate the biosafety of implantation.Results: The results of in vitro cytotoxicity showed no significant difference of cell viability was observed in the S-PRL, L-PRL or LG-PRL groups compared to the control group throughout the whole experiment. The HLECs cultured on the PRL film surface presented similar cell number, but smaller average cell area (53.8% vs 100%) when compared to the control group, which implied obvious adhesion inhibition on HLECs caused by PRL film. After implantation of S-PRL, L-PRL or LG-PRL into the posterior chamber of rabbit eyes, no obvious inflammation and IOP elevation were observed at each time point in all sample groups compared to the control group, which indicated that PRL samples had good implantation biosafety. Most of the implanted L-PRL and LG-PRL kept in the correct location, while only less of the S-PRL was at the right site. That was, L-PRL and LG-PRL had proper relative position and high retention ratio in the posterior chamber of rabbit eyes. L-PRL and S-PRL samples tended to attach to iris surface, while LG-PRL sample constructed enough space on the iris surface by its grooves surrounding the central optical zone, which was conducive to circulation of aqueous humor.Conclusions: The newly developed LG-PRL sample presented good biosafety in terms of the negligible in vitro cytotoxicity, ocular inflammation and IOP fluctuations. The LG-PRL provided the best implantation feasibility due to the more proper relative position, available space for aqueous humor circulation, and high retention ratio in the posterior chamber of rabbit eyes among the three kinds of PRL samples. Thus, LG-PRL is a promising alternative with appropriate size and surface structure to more effectively correct refractive errors.

Refractive lens power and lens thickness in children (6–16 years old)

To examine the refractive lens power (RLP) and lens thickness and their associated factors in children from North-Western China. Children from two schools (primary school and junior high school) in the North-Western Chinese province of Qinghai underwent a comprehensive ophthalmic examination including biometry and cycloplegic refractometry. The RLP was calculated using Bennett’s equation. The study included 596 (77.9%) individuals (mean age: 11.0 ± 2.8 years; range: 6–16 years) with a mean axial length of 23.65 ± 1.24 mm (range: 20.02–27.96 mm). Mean lens thickness was 3.30 ± 0.16 mm (range: 2.85–3.99 mm) and mean RLP was 24.85 ± 1.98D (range: 19.40–32.97). In univariate analysis, girls as compared to boys had a significantly thicker lens and greater RLP, shorter axial length, smaller corneal curvature radius and shorter corneal curvature radius (all P < 0.001). Both sexes did not differ significantly in refractive error (P = 0.11) and corneal thickness (P = 0.16). RLP was positively associated with refractive error (correlation coefficient r = 0.33; P < 0.001) and lens thickness (r = 0.62; P < 0.001) and negatively with axial length (r = − 0.70; P < 0.001). In univariate analysis, RLP decreased significantly with older age in the age group from age 6–13, while it plateaued thereafter, with no significant difference between boys and girls. In multivariate regression analysis, a higher RLP was associated with younger age (P < 0.001; standard regression coefficient β = − 0.07), female sex (P < 0.001; β = − 0.08), shorter axial length (P < 0.001; β = − 0.48) and higher lens thickness (P < 0.001; β = 0.42). In Chinese children, RLP with a mean of 24.85 ± 1.98D decreases with older age, male sex, longer axial length, and thinner lens thickness. Changes in RLP and axial length elongation are important players in the emmetropization and myopization.

Distribution of preoperative angle alpha and angle kappa values in patients undergoing multifocal refractive lens surgery based on a positive contact lens test

Purpose To assess the preoperative objective angle alpha and angle kappa measurements of patients deciding to undergo multifocal refractive lens surgery based on a subjective positive multifocal contact lens test (MCLT). Methods Retrospective, consecutive case series. Alpha and kappa angles were measured using the iTrace aberrometer. All patients also performed a 1-week MCLT. Only patients with a positive MCLT underwent surgery. Visual outcome (UCVA) was obtained in the 1-year follow-up. We assessed the preoperative distribution of angle values within MCLT positive and negative patient groups. Results Two hundred seventeen eyes (111 patients) were included. Mean age was 56.4 years (SD 5.6) and 46.9% were female. In 71 eyes (38 patients), MCLT was positive. Of them, 12 eyes (17%) had an angle alpha and angle kappa ≥ 0.5mm. Of 146 eyes (73 patients) who refrained from surgery due to a negative MCLT, 71 eyes (48.6%) had both angles small (<0.5mm). In the 1-year follow-up, UCVA improved by 0.68 logMAR (SD 0.51; p<0.001) from baseline. Eyes with both small angle alpha and kappa sizes improved by 0.78 logMAR (SD 0.56), as did eyes with high (≥0.5mm) angle sizes (0.82 logMAR (SD 0.53). UCVA of eyes (n=24) with high alpha but low kappa sizes improved less (−0.31 logMAR (SD 0.13; p=0.019)). Conclusion Four out of five patients with a positive MCLT also had correspondingly small angle values. One-half of patients with low preoperative angle values refrained from surgery due to a negative MCLT result. One-year visual acuity improvement was substantial and independent from angle sizes.