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Locomotive soft robots (SoRos) have gained prominence due to their adaptability. Traditional locomotive SoRo design is based on limb structures inspired by biological organisms and requires human intervention. Evolutionary robotics, designed using evolutionary algorithms (EAs), have shown potential for automatic design. However, EA-based methods face the challenge of high computational cost when considering multiphysics in locomotion, including materials, actuations, and interactions with environments. Here, we present a design approach for pneumatic SoRos that integrates gradient-based topology optimization with multiphysics material point method (MPM) simulations. This approach starts with a simple initial shape (a cube with a central cavity). The topology optimization with MPM then automatically and iteratively designs the SoRo shape. We design two SoRos, one for walking and one for climbing. These SoRos are 3D printed and exhibit the same locomotion features as in the simulations. This study presents an efficient strategy for designing SoRos, demonstrating that a purely mathematical process can produce limb-like structures seen in biological organisms.

Transparent silica glass is one of the most essential materials used in society and industry, owing to its exceptional optical, thermal, and chemical properties. However, glass is extremely difficult to shape, especially into complex and miniaturized structures. Recent advances in three-dimensional (3D) printing have allowed for the creation of glass structures, but these methods involve time-consuming and high-temperature processes. Here, we report a photochemistry-based strategy for making glass structures of micrometer size under mild conditions. Our technique uses a photocurable polydimethylsiloxane resin that is 3D printed into complex structures and converted to silica glass via deep ultraviolet (DUV) irradiation in an ozone environment. The unique DUV-ozone conversion process for silica microstructures is low temperature (~220°C) and fast (<5 hours). The printed silica glass is highly transparent with smooth surface, comparable to commercial fused silica glass. This work enables the creation of arbitrary structures in silica glass through photochemistry and opens opportunities in unexplored territories for glass processing techniques.

Shape-morphing structures that can reconfigure their shape to adapt to diverse tasks are highly desirable for intelligent machines in many interdisciplinary fields. Shape memory polymers are one of the most widely used stimuli-responsive materials, especially in 3D/4D printing, for fabricating shape-morphing systems. They typically go through a hot-programming step to obtain the shape-morphing capability, which possesses limited freedom of reconfigurability. Cold-programming, which directly deforms the structure into a temporary shape without increasing the temperature, is simple and more versatile but has stringent requirements on material properties. Here, we introduce grayscale digital light processing (g-DLP) based 3D printing as a simple and effective platform for fabricating shape-morphing structures with cold-programming capabilities. With the multimaterial-like printing capability of g-DLP, we develop heterogeneous hinge modules that can be cold-programmed by simply stretching at room temperature. Different configurations can be encoded during 3D printing with the variable distribution and direction of the modular-designed hinges. The hinge module allows controllable independent morphing enabled by cold programming. By leveraging the multimaterial-like printing capability, multi-shape morphing structures are presented. The g-DLP printing with cold-programming morphing strategy demonstrates enormous potential in the design and fabrication of shape-morphing structures., (© 2023. Springer Nature Limited.)

A depolymerizable vitrimer that allows both reprocessability and monomer recovery by a simple and scalable one-pot two-step synthesis of vitrimers from cyclic lactones is reported. Biobased δ-valerolactone with alkyl substituents (δ-lactone) has low ceiling temperature; thus, their ring-opening-polymerized aliphatic polyesters are capable of depolymerizing back to monomers. In this work, the amorphous poly(δ-lactone) is solidified into an elastomer (i.e., δ-lactone vitrimer) by a vinyl ether cross-linker with dynamic acetal linkages, giving the merits of reprocessing and healing. Thermolysis of the bulk δ-lactone vitrimer at 200 °C can recover 85-90 wt% of the material, allowing reuse without losing value and achieving a successful closed-loop life cycle. It further demonstrates that the new vitrimer has excellent properties, with the potential to serve as a biobased and sustainable replacement of conventional soft elastomers for various applications such as lenses, mold materials, soft robots, and microfluidic devices., (© 2023 Wiley-VCH GmbH.)

Turing patterns are self-organizing stripes or spots widely found in biological systems and nature. Although inspiring, their applications are limited. Inflatable shape-morphing structures have attracted substantial research attention. Traditional inflatable structures use isotropic materials with geometrical features to achieve shape morphing. Recently, gradient-based optimization methods have been used to design these structures. These methods assume anisotropic materials whose orientation can vary freely. However, this assumption makes fabrication a considerable challenge by methods such as additive manufacturing, which print isotropic materials. Here, we present a methodology of using Turing patterns to bridge this gap. Specifically, we use Turing patterns to convert a design with distributed anisotropic materials to a distribution with two materials, which can be fabricated by grayscale digital light processing 3D printing. This work suggests that it is possible to apply patterns in biological systems and nature to engineering composites and offers new concepts for future material design.

Liquid crystal elastomers (LCE) are appealing candidates among active materials for 4D printing, due to their reversible, programmable and rapid actuation capabilities. Recent progress has been made on direct ink writing (DIW) or Digital Light Processing (DLP) to print LCEs with certain actuation. However, it remains a challenge to achieve complicated structures, such as spatial lattices with large actuation, due to the limitation of printing LCEs on the build platform or the previous layer. Herein, a novel method to 4D print freestanding LCEs on-the-fly by using laser-assisted DIW with an actuation strain up to -40% is proposed. This process is further hybridized with the DLP method for optional structural or removable supports to create active 3D architectures in a one-step additive process. Various objects, including hybrid active lattices, active tensegrity, an actuator with tunable stability, and 3D spatial LCE lattices, can be additively fabricated. The combination of DIW-printed functionally freestanding LCEs with the DLP-printed supporting structures thus provides new design freedom and fabrication capability for applications including soft robotics, smart structures, active metamaterials, and smart wearable devices., (© 2022 Wiley-VCH GmbH.)

Shape-morphing magnetic soft materials, composed of magnetic particles in a soft polymer matrix, can transform shape reversibly, remotely, and rapidly, finding diverse applications in actuators, soft robotics, and biomedical devices. To achieve on-demand and sophisticated shape morphing, the manufacture of structures with complex geometry and magnetization distribution is highly desired. Here, a magnetic dynamic polymer (MDP) composite composed of hard-magnetic microparticles in a dynamic polymer network with thermally responsive reversible linkages, which permits functionalities including targeted welding for magnetic-assisted assembly, magnetization reprogramming, and permanent structural reconfiguration, is reported. These functions not only provide highly desirable structural and material programmability and reprogrammability but also enable the manufacturing of functional soft architected materials such as 3D kirigami with complex magnetization distribution. The welding of magnetic-assisted modular assembly can be further combined with magnetization reprogramming and permanent reshaping capabilities for programmable and reconfigurable architectures and morphing structures. The reported MDP are anticipated to provide a new paradigm for the design and manufacture of future multifunctional assemblies and reconfigurable morphing architectures and devices., (© 2021 Wiley-VCH GmbH.)

Shape-programmable soft materials that exhibit integrated multifunctional shape manipulations, including reprogrammable, untethered, fast, and reversible shape transformation and locking, are highly desirable for a plethora of applications, including soft robotics, morphing structures, and biomedical devices. Despite recent progress, it remains challenging to achieve multiple shape manipulations in one material system. Here, a novel magnetic shape memory polymer composite is reported to achieve this. The composite consists of two types of magnetic particles in an amorphous shape memory polymer matrix. The matrix softens via magnetic inductive heating of low-coercivity particles, and high-remanence particles with reprogrammable magnetization profiles drive the rapid and reversible shape change under actuation magnetic fields. Once cooled, the actuated shape can be locked. Additionally, varying the particle loadings for heating enables sequential actuation. The integrated multifunctional shape manipulations are further exploited for applications including soft magnetic grippers with large grabbing force, reconfigurable antennas, and sequential logic for computing., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Purpose of Review: This study provides an overview of the three types of corneal inlays now in use for the correction of presbyopia and reviews recently published evidence of the inlays' safety and efficacy., Recent Findings: Results for corneal reshaping and refractive inlays are promising, but very limited. Small-aperture inlays are already in widespread use and have been shown to improve uncorrected near and intermediate vision without a significant loss in distance acuity or an unacceptable increase in visual symptoms. Complications have been minimal, but the inlays may be removed if necessary. They do not prevent visualization or imaging of the retina and may be retained during subsequent cataract surgery., Summary: The presbyopic demographic is large and growing, with a high level of interest in spectacle independence. There is currently no other effective solutions for presbyopes who desire good uncorrected vision at all distances without the risks of intraocular surgery or the visual compromises of monovision. Additional research is needed, but the future for corneal inlay technology is bright.

Purpose: To compare clinical outcomes of wavefront-guided LASIK with and without aspheric compensation in myopic eyes., Methods: In this observational, single-center study, 134 eyes were treated using an aspheric module in combination with wavefront-guided profiles (PTA-algorithm) and compared to 146 eyes treated with the predecessor wavefront-guided software (APT) that has no aspheric compensation. All treatment plans included the Rochester nomogram that accounts for the preoperative manifest refraction and interaction of higher order aberrations. Active eye-tracking (including cyclorotational movements) was utilized during photoablation., Results: Results at the 3-month follow-up: 67 % of PTA-treated eyes and 39 % of APT-treated eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 or better. Change in mean higher order aberration root-mean-square (HOA RMS) after PTA treatments was not statistically significant (p = 0.18). The increase in HOA RMS after APT treatments was statistically significant (p = 0.003). Change in mean postop spherical aberration (SA) after PTA treatments was not statistically significant (p = 0.27). The change in SA after APT treatments was statistically significant (p = 0.001). In both cohorts, mean uncorrected low-contrast visual acuity was statistically not different to preoperative corrected values., Conclusions: Adding an aspheric compensation to wavefront-guided myopic LASIK statistically improved clinical results in terms of visual acuity and refractive outcomes. Low-contrast visual acuity was not negatively affected in either group. While in APT-treated eyes mean HOA RMS and mean SA were significantly increased postoperatively, PTA-treated eyes showed neither induced HOA RMS nor induced SA.

Purpose: To evaluate higher-order aberrations (HOAs) after implantation of Artiflex phakic intraocular lenses (pIOLs)., Setting: Department of Ophthalmology, Academic Hospital Maastricht, Maastricht, The Netherlands., Methods: This retrospective comparative case series comprised 27 eyes (14 patients) that had Artiflex pIOL implantation and 22 eyes (13 patients) that had Artisan pIOL implantation. Refractive data, pupil size, IOL decentration, and HOA values were recorded and compared. Laboratory analysis was performed. Follow-up was 1 year., Results: In the Artiflex group, the mean spherical equivalent (SE) changed from -9.95 diopters (D) +/- 1.43 (SD) (range -6.75 to -12.13 D) to -0.30 +/- 0.53 D (range -1.94 to 0.56 D). Postoperatively, trefoil-y increased (increase factor 1.73) and spherical aberration decreased (increase factor 0.55). The mean pIOL decentration was 0.24 +/- 0.12 mm; 96.3% were decentered 0.5 mm or less. There was a significant correlation between pIOL decentration and postoperative spherical aberration and coma-y. In the Artisan group, the mean SE changed from -9.90 +/- 2.74 D (range -4.00 to -14.50 D) to -0.20 +/- 0.42 D (range -0.75 to 0.50 D). Postoperatively, trefoil-y and spherical aberration increased (increase factors 3.32 and 6.84, respectively). Laboratory analysis confirmed the negative and positive spherical aberration profile of the Artiflex pIOL and Artisan pIOL, respectively., Conclusions: Artiflex pIOL implantation decreased spherical aberration, while Artisan pIOL implantation increased spherical aberration. Trefoil-y increased in both groups. These changes might be explained by incision size differences in relation to trefoil and differences in optic design in relation to spherical aberration.

Purpose: To develop and test the efficacy of myopic treatment, based on preoperative manifest refraction and higher order aberrations, in enhancing the postoperative refractive error following customized LASIK treatment and compare results with the manufacturer-recommended sphere offset Zyoptix treatment nomogram, which does not account for the preoperative higher order aberrations., Methods: One hundred seventy-five myopic eyes (89 patients) were treated based on the Rochester nomogram, which specified the amount of myopia to be treated based on preoperative manifest refraction and higher order aberrations, including third order aberrations and spherical aberration. Postoperative refractive error was measured at 1 month and compared to that theoretically estimated with the Zyoptix nomogram., Results: The mean preoperative sphere and cylinder were -4.52 +/- 2.05 diopters (D) and -0.81 +/- 0.70 D, respectively. The mean postoperative spheres were +0.04 +/- 0.33 D and +0.31 +/- 0.54 D, using the Rochester and Zyoptix nomograms, respectively. The mean postoperative spherical equivalent refractions were -0.11 +/- 0.34 D and +0.15 +/- 0.53 D using the Rochester and Zyoptix nomograms, respectively. The Rochester nomogram reduced the range of postoperative spherical equivalent to +/- 1.00 D, which was significantly better than that using the Zyoptix nomogram (t = 5.46, P < .0001), which would have resulted in 8% of eyes with a postoperative spherical equivalent refraction > +/- 1.00 D. Using the Rochester nomogram, 93.1% of eyes attained a postoperative UCVA > or = 20/20. The percentage of postoperative hyperopic overcorrection decreased to 2.8% in the Rochester nomogram group from 22.3% using the Zyoptix nomogram, which only adjusts spherical values based on preoperative sphere and does not account for preoperative aberrations., Conclusions: The Rochester nomogram compensates for the effect of preoperative higher order aberrations on sphere and provided reduced range of postoperative spherical equivalent refraction.

Purpose: To compare outcomes after custom LASIK based on non-pharmacologically dilated (natural mesopic pupil) and pharmacologically dilated wavefront aberration measurement., Design: Case-control study., Participants and Controls: The study group included 81 myopic eyes from 81 patients (mean preoperative spherical equivalent [SE], -4.15+/-1.97 diopters [D]). The control group consisted of 87 myopic eyes from 87 patients (mean preoperative SE, -4.98+/-2.00 D)., Methods: The 81-eye study cohort was treated based on nonpharmacological low mesopic dilated wavefront aberration measurement (Zywave aberrometer), and the postoperative outcome was compared with that of the control group of 87 eyes treated, based on pharmacologically dilated (2.5% neosynephrine) wavefront data, using the Zyoptix platform. The same nomogram was used for both groups, which adjusts sphere based on the amount of preoperative higher-order aberration. All eyes had a low mesopic pupil diameter of > or =6.3 mm without pharmaceutical intervention., Main Outcome Measure: Postoperative 3-month visual acuity (VA), contrast sensitivity, and refractive error., Results: Of the non-pharmacologically dilated eyes (study) and pharmacologically dilated (control) eyes, 96.3% and 96.6%, respectively, attained postoperative uncorrected VA of 20/20 or better. Although 96.6% of the eyes were within the target SE of +/-0.50 D in the control group, 100% of the 81 study eyes were within an SE of +/-0.50 D postoperatively. The range of postoperative SE (-0.75 to +1 D) was slightly reduced among the study eyes (+/-0.50 D). Differences were not statistically significant., Conclusions: When a low mesopic pupil dilates to > or =6.3 mm, pharmacological dilation with wavefront-guided ablation may provide no additional benefit with regard to spherical accuracy when compared with nonpharmacological wavefront-guided ablation. The use of the Rochester nomogram, which accounts for aberration interaction, provided excellent results with or without pharmacological dilation.

Purpose: Customized laser surgery attempts to correct higher order aberrations, as well as defocus and astigmatism. The success of such a procedure depends on using a laser beam that is small enough to produce fine ablation profiles needed to correct higher order aberrations., Methods: Wave aberrations were obtained from a population of 109 normal eyes and 4 keratoconic eyes using a Shack-Hartmann wavefront sensor. We considered a theoretical customized ablation in each eye, performed with beams of 0.5, 1.0, 1.5, and 2.0 mm in diameter. We then calculated the residual aberrations remaining in the eye for the different beam sizes. Retinal image quality was estimated by means of the modulation transfer function (MTF), computed from the residual aberrations. Fourier analysis was used to study spatial filtering of each beam size., Results: The laser beam acts like a spatial filter, smoothing the finest features in the ablation profile. The quality of the correction declines steadily when the beam size increases. A beam of 2 mm is capable of correcting defocus and astigmatism. Beam diameters of 1 mm or less may effectively correct aberrations up to fifth order., Conclusion: Large diameter laser beams decrease the ability to correct higher order aberrations. A top-hat laser beam of 1 mm (Gaussian with FWHM of 0.76 mm) is small enough to produce a customized ablation for typical human eyes.

Purpose: To describe the results of treating interface keratitis using a combination of intensive topical and oral corticosteroids., Setting: Casey Eye Institute, Portland, Oregon, USA., Methods: Thirteen eyes treated for grade 2 to 3 interface keratitis using an oral corticosteroid (prednisone 60 to 80 mg) as well as an hourly topical corticosteroid were retrospectively reviewed. The best corrected visual acuity (BCVA) was used as an objective guide of whether to treat with intense topical and oral corticosteroids, flap irrigation, or both. Predisposing factors such as intraoperative epithelial defects or a history of severe allergies or atopy were also looked for., Results: All 13 eyes responded favorably to the combination of intensive topical and oral corticosteroids and had a BCVA of 20/20 after the keratitis resolved. In 6 eyes (46%), the patients had a history of severe seasonal allergies. One day postoperatively, 3 eyes (23%) had an epithelial defect and 2 eyes (15%), lint particles or debris embedded in the interface. With oral corticosteroid use, 3 patients (23%) noted mild stomach irritation and 2 (15%) noted nervousness. All 5 side effects resolved without sequelae. No patient developed a serious side effect., Conclusions: A short, intense course of an oral corticosteroid was an effective treatment in patients with grade 2 or higher interface keratitis when combined with a topical corticosteroid administered hourly. The BCVA is a helpful objective measure of the severity of interface keratitis and can be used to guide the clinician in the therapeutic strategy.

Purpose: Photoastigmatic refractive keratectomy (PARK) was studied in a multi-center clinical trial. The Nidek EC-5000 excimer laser was evaluated for its effect on refraction, visual acuity, and safety measures as part of a U.S. Food and Drug Administration (FDA) regulated study., Methods: Eight U.S. centers enrolled adults with eyes having refractive astigmatism up to 4.00 D and a myopic spherical equivalent refraction up to -8.00 D. Results are reported for 749 eyes of 486 patients with at least 6 months follow-up. The rectangular beam scanning Nidek EC-5000 used a 5.5-mm-diameter treatment zone, a 7.0-mm-diameter peripheral blend zone, and a 40 Hz pulse rate for surface treatment of myopic astigmatism. Nomogram corrections to machine settings were required to achieve the desired results., Results: Preoperative average spherical equivalent refraction of -4.90+/-1.74 D was reduced to -0.02+/-0.79 D at 6 months. Refractive stability was established at 3 months. Over 62% of eyes were within +/-0.50 D of desired correction at 6 months, with over 86% within +/-1.00 D. Uncorrected visual acuity improved by an average of 10 Snellen lines; over 64% of eyes saw 20/20 or better uncorrected and over 93% saw 20/40 or better uncorrected at 6 and 12 months. PARK treatment effectively reduced astigmatism with little average axis error or magnitude error. Corneal haze and safety concerns were minimal., Conclusions: Photoastigmatic refractive keratectomy using the Nidek EC-5000 excimer laser provided significant reduction of myopia and astigmatism, with minimal complications.

Background: The long-term effects of radial keratotomy on the corneal endothelium are not well understood. We evaluated the effects of radial keratotomy on the corneal endothelium on the central and midperipheral corneal endothelium., Methods: Anterior radial keratotomy in 25 eyes was performed and patients were followed for a duration of 4 to 10 years after surgery. Eleven non- contact lens wearing control eyes did not have surgery and were followed for the same period. Morphometric analysis of specular microscopic images was performed with regard to cell density, percent hexagonality, and coefficient of variation., Results: Mean corneal endothelial cell loss rates were 0.4% per year in the radial keratotomy group and 0.9% in the untreated control group over the study duration (mean 7 yr). Morphometric analysis of the cells failed to show a significant change in hexagonality and coefficient of variation. Evaluation of the midperipheral corneal cell counts demonstrated a 1% per year cell loss rate. The cell loss rates in radial keratotomy patients followed over this period were consistent with that noted for normal aging (0.5 to 2.5% per year)., Conclusion: Radial keratotomy does not cause accelerated endothelial cell loss over 4 to 10 years.

Purpose: The purpose of this study is to determine the long-term effects of polymethylmethacrylate (PMMA) contact lens wear on the corneal endothelium. The authors had noted previously advanced polymegethism and decreased cell densities in a few long-term PMMA contact lens wearers. They evaluated a large group of such lens wearers to determine the prevalence of polymegethism and reduced endothelial cell density within this lens-wearing population., Methods: The authors examined the morphologic characteristics of the corneal endothelium in 162 PMMA contact lens wearers or age-matched controls. Eighty-one subjects had worn contact lenses for more than 20 years., Results: Patients showed advanced polymegethism and pleomorphism compared with controls. Mean cell density in the contact lens-wearing group was not different from controls, but a significantly greater percentage of contact lens wearers (11%, 9 of 81 patients) had cell densities less than 2000 cells/mm2 compared with controls (2.5%, 2 of 81 patients), and were also significantly more likely to have severe polymegethism (coefficient of variation, > 0.60) and severe pleomorphism (frequency of hexagons < 40%)., Conclusion: This study is unique, in that it notes a subgroup of PMMA contact lens wearers who are more susceptible to significant morphometric changes and reduced endothelial cell densities with long-term contact lens use.

Some patients require a contact lens after glaucoma filtering surgery. The visual rehabilitation of such eyes can be challenging. We report on a total of eight eyes (seven patients) fit with lenticular-design, rigid gas permeable (RGP) contact lenses after the successful establishment of a filtering bleb. In follow-up (mean: 40 months), all patients have successfully worn lenses without adverse effects. We believe that, with careful fitting, close monitoring, and appropriate patient selection, the presence of a filtering bleb need not be a contraindication to contact lens wear, particularly when a smooth-edged, rigid gas permeable (RGP) daily wear lens is used.

Vitamin A is required for the normal growth maintenance and maturation of the corneal epithelium and is effective in the treatment of xerophthalmia and experimental corneal epithelial wounds when applied topically as retinoic acid. The normal route of delivery of vitamin A to the cornea has remained undefined. We collected tears from normal and vitamin A deficient rabbits and from humans and analyzed them by high pressure liquid chromatography. A peak corresponding to a retinol standard was eluted from normal rabbit and human tears but was absent from the vitamin A deficient rabbit tears. The retinol concentration in rabbit tears was 69 ng/ml (0.2 X 10(-6)M) and in human tears was 16 ng/ml (0.5 X 10(-7)M). This demonstration that vitamin A is present in the tears as retinol establishes the rationale for treatment of corneal disease with topical vitamin A.

The majority of patients with recurrent corneal erosion respond to conventional forms of therapy such as topical lubricants, patching, debridement, or bandage soft contact lenses. However, there remain a small number who do not. For the small number of patients who do not respond to this type of treatment, this report describes a procedure: multiple anterior stromal punctures are created that presumably stimulate more secure epithelial adhesion to the underlying stroma. Of 21 eyes in 18 patients treated in this manner, three eyes required retreatment of adjacent areas; otherwise, there were no recurrences in follow-up periods ranging from 5 months to 12 years. This procedure is a simple and effective method for safe office treatment of patients with recalcitrant recurrent erosion.

Records of approximately 310,000 patients admitted to the 10 hospitals in Botswana between 1960 and 1972 have been studied and details of 1445 patients with malignant tumours abstracted. For the 894 tumours for which there was some supporting evidence--at best histological proof and minimally a clinical description of symptoms--proportional frequencies have been calculated for all sites and comparison made with the findings of other surveys. Cancer of the cervix uteri is overwhelmingly the most commonly occurring malignant tumour and the proportional frequency is among the highest observed in Africa south of the Sahara. Skin tumours are unusually common for Southern Africa in both sexes. In males, penile and prostatic tumours have a relatively high frequency whilst the frequencies for liver and lung are lower than in other parts of Southern Africa. Oesophageal cancer in males has a moderate frequency. Other tumours which show a marked variation of frequency within Africa--Kaposi's sarcoma and cancers of the stomach and bladder--are all low in frequency in Botswana. Tumours which are rare throughout Africa but common in Western Europe and North America--cancers of the colon, rectum and corpus uteri--are also rare in Botswana.

Contact lenses may induce short- and long-term corneal endothelial changes. The endothelial bleb response is a short-term, reversible change noted with contact lens wear. Long-term endothelial changes such as polymegethism (increased variation in cell size) and pleomorphism (a decrease in the frequency of hexagonal cells) have also been detected in polymethylmethacrylate, rigid gas permeable, and daily and extended wear soft contact lens patients. These morphometric changes have also been seen in myopes, aphakes, and corneal transplant recipients. Differences in endothelial morphometry between the central and mid-peripheral regions of the cornea have also been noted in hard lens wearers. The long-term significance of these findings is discussed.

Wide-field specular microscopy and computer-assisted morphometry were performed on 20 aphakic eyes in 16 patients who had worn a high-water content hydrogel contact lens on an extended wear basis for at least 12 months (mean, 28 months) following intracapsular cataract extraction. When compared with 22 non-lens-wearing aphakic eyes matched for age and postoperative period, the endothelial cell changes in the above patients included a significantly higher coefficient of variation in cell area (polymegathism) and a marked reduction in the frequency of hexagonal cells (pleomorphism) without any significant difference in cell density. Although the clinical significance of these endothelial changes remains unclear, they may indicate hypoxic stress to the corneal endothelium or be an early sign of ongoing cell loss.

Using wide-field specular microscopy, we evaluated the morphologic features of the corneal endothelium in 14 eyes of 14 patients with keratoconus who had worn a polymethylmethacrylate hard contact lens for at least four years (mean, 71 months) after penetrating keratoplasty. Comparisons were made with 14 non-lens-wearing eyes of 14 patients with keratoconus matched for age, length of postoperative period, and other variables. Examination of the endothelium of the contact lens wearers showed a significantly higher coefficient of variation in cell size (polymegethism) and a marked decrease in the percentage of hexagonal cells (pleomorphism), with a significant decrease in cell density (P less than .05). The cause of these morphologic abnormalities remains unclear but may be related to lens-induced hypoxic stress to the corneal endothelium causing ongoing cell loss.