Hard Lenses Research Articles

Environmental factors that contribute to upper eyelid ptosis: a study of identical twins.

Current literature provides little information about the impact of environmental exposures on the severity of acquired blepharoptosis. The authors assessed environmental factors that may contribute to eyelid ptosis in a population of identical twins. Photographs of 286 sets of twins from a prospectively collected database from 2008 to 2010 were reviewed. The authors identified 96 sets of identical twins (192 individual persons) who had differing severity of ptosis. Digital photographs were analyzed, and the degree of ptosis was measured in each eye of every subject. The external factors that could potentially contribute to blepharoptosis were taken into consideration. The authors then assessed the correlations of 9 different environmental risk factors with ptosis. Generalized linear mixed model were constructed to determine the associations of ptosis measurements with environmental risk factors obtained from the subject survey database. The mean level of upper eyelid ptosis in the study population was 1.1 mm. The mean difference in ptosis between twins was 0.5 mm. Wearing contact lenses, either hard or soft, was significantly associated with ptosis. The mean ptosis measurement among twins who did not wear contact lenses was 1.0 mm; for those who wore soft contact lenses, the mean was 1.41 mm, and for those who wore hard contact lenses, the mean was 1.84 mm. Acquired ptosis is not linked to body mass index, smoking behavior, sun exposure, alcohol use, work stress, or sleep. Wearing either hard or soft lenses was associated with an increased risk of ptosis. These influences are independent of genetic predisposition. 3 Diagnostic.

Focusing performance of hard X-ray single Kinoform lens

Nowadays, X-ray nanoprobe plays an important role in many research fields, ranging from materials science to geophysics and environmental science, to biophysics and protein crystallography. Refractive lenses, mirrors, and Laue lenses, can all focus X-rays into a spot with a size of less than 50 nm. To design a refractive lens at fixed wavelengths, absorption in the lens material can be significantly reduced by removing 2πup phase-shifting regions. This permits short focal length devices to be fabricated with small radii of curvatures at the lens apex. This feature allows one to obtain a high efficiency X-ray focusing. The reduced absorption loss also enables optics with a larger aperture, and hence improving the resolution for focusing. Since the single Kinoform lens can focus hard X-ray into a spot on a nanoscale efficiently, it has very important application prospect in X-ray nano-microscopy and nano-spectroscopy. We present a theoretical analysis of optical properties of the single Kinoform lens. Using Fermat's principle of least time, an exact solution of the single Kinoform lens figure is derived. The X-ray diffraction theory is reviewed. The complex amplitude transmittance function of the X-ray single Kinoform lens is derived. According to Fourier optics and optical diffraction theory, we set up the physical model of X-ray single Kinoform lens focusing. Employing this physical model, we study how the focusing performance of hard X-ray single Kinoform lens is influenced by the material, the photon energy, the number of steps and the vertex radius of curvature. We find that diamond single Kinoform lens can achieve a smaller focusing beam size with higher intensity gain than Al and Si single Kinoform lens. The single Kinoform lens designed at a certain photon energy can also focus other photon energies with different lateral beam sizes, axial beam sizes, intensity gains and focusing distances. The numbers of steps of a single Kinoform lens can be lessened with the thickness of step increasing, while the single Kinoform lens keeps good focusing performance. To improve the focusing performance further, reducing the vertex radius of curvature is proposed. Following these rules, a single Kinoform lens is optimally designed to focus 30 keV hard X-ray down to a lateral size of 14 nm (full-width at half-maximum, FWHM) and an axial size of 62 μm (FWHM) with an intensity gain of four orders of magnitude and transmittance of 30%.

Surgical outcomes of 23-gauge vitrectomy for the management of lens fragments dropped into the vitreous cavity during cataract surgery

PurposeTo assess the clinical features and surgical outcomes of 23-Gauge (G) vitrectomy for lens fragments dropped into the vitreous during cataract surgery. MethodsA retrospective, non-comparative, interventional case series at a single medical center. The medical records of 45 eyes from 45 consecutive patients who were referred to our hospital for surgical retrieval of phacoemulsification dropped lens fragments and who underwent 23-G vitrectomy were retrospectively reviewed. Data pertaining to patient demographics, pre- and post-operative Snellen visual acuity, and postoperative complications were recorded. Factors associated with dropped lens fragments were also examined. ResultsMean patient age was 68.18±11.47years. The preoperative and postoperative mean logarithm of minimum angle of resolution (logMAR) visual acuity was 1.91±0.59 (Snellen equivalent 0.06±0.15) and 0.42±0.51 (Snellen equivalent 0.54±0.31), respectively. Forty-two eyes (93.3%) had dislocated lens fragments <50% of the total lens size. Two eyes (4.4%) had a large and hard lens nucleus, which necessitated the use of a 20-G fragmatome to efficiently and completely remove the lens material. At the final examination, 30 eyes (66.6%) had a visual acuity better than 20/40. Post-vitrectomy complications included elevated IOP for at least 3months (n=5 eyes, 11.1%), intraocular lens dislocation (n=2 eyes, 4.4%), and cystoid macular edema (n=1 eye, 2.2%). No cases of postoperative endophthalmitis or retinal detachment were observed. ConclusionsA 23-G vitrectomy is safe and efficient for the surgical management of dropped lens fragments following cataract surgery.

Retained soft contact lens masquerading as a chalazion: A case report

A misplaced contact lens is a common ocular emergency presenting to the eye casualty. We report a case of lost soft contact lens which migrated in the lid and presented 13 years later with symptomatic eye lid swelling. Authors in the past have reported migration and subsequent retention of lost hard lenses in locations such as the superior fornix and eyelid. To the best of our knowledge, misplaced soft contact lens masquerading as a chalazion has not been reported in the literature. Consideration should be given to the possibility of a retained contact lens in a patient with a history of a lost or misplaced lens, and examination of the ocular surface with double eversion of the upper lid should be performed.

The role of macromolecular crowding in the evolution of lens crystallins with high molecular refractive index

Crystallins are present in the lens at extremely high concentrations in order to provide transparency and generate a high refractive power of the lens. The crystallin families prevalent in the highest density lens tissues are γ-crystallins in vertebrates and S-crystallins in cephalopods. As shown elsewhere, in parallel evolution, both have evolved molecular refractive index increments 5–10% above those of most proteins. Although this is a small increase, it is statistically very significant and can be achieved only by very unusual amino acid compositions. In contrast, such a molecular adaptation to aid in the refractive function of the lens did not occur in crystallins that are preferentially located in lower density lens tissues, such as vertebrate α-crystallin and taxon-specific crystallins. In the current work, we apply a model of non-interacting hard spheres to examine the thermodynamic contributions of volume exclusion at lenticular protein concentrations. We show that the small concentration decrease afforded by the higher molecular refractive index increment of crystallins can amplify nonlinearly to produce order of magnitude differences in chemical activities, and lead to reduced osmotic pressure and the reduced propensity for protein aggregation. Quantitatively, this amplification sets in only at protein concentrations as high as those found in hard lenses or the nucleus of soft lenses, in good correspondence to the observed crystallin properties in different tissues and different species. This suggests that volume exclusion effects provide the evolutionary driving force for the unusual refractive properties and the unusual amino acid compositions of γ-crystallins and S-crystallins.

A Modified Technique for Extracting a Dislocated Lens with Perfluorocarbon Liquids and Viscoelastics

The authors describe a modified technique for extraction of a dislocated crystalline lens or large and hard lens fragments displaced into the vitreous cavity. An ophthalmic viscosurgical device was used around and on top of the heavy liquid bubble to keep the lens centered and less mobile for easier phacofragmentation or removal by the cutting-suction probe. This technique was used in 10 eyes, including cases of traumatic dislocation and Marfan syndrome, with excellent anatomical results and no complications that could be attributed to the surgical technique. The technique has also been used to retrieve and reposition dislocated intraocular lenses.

Intravitreal Bimanual Surgery for Residual Lens Fragments and Displaced Crystalline Lenses

The authors have developed a new technique for removing large and hard lens fragments or crystalline lenses with hard nuclei dislocated into the vitreous cavity using an optic fiber-free intravitreal surgical system (OFFISS). The OFFISS visualizes the fundus without a fiberoptic and facilitates the bimanual technique. The lens materials are stabilized with one hand and the fragmatome to emulsify the lens fragments is controlled with the other. The lens fragments or subluxated crystalline lenses can be removed through 20-gauge incisions. This technique was used in 14 cases and was found to be safe and not invasive.

Fabrication and Testing of Hard X-Ray Hourglass Lenses

Based on the refraction theory of the lens, the SU-8 photoresist hard X-ray hourglass lenses with three different structure parameters are fabricated. The mask-back exposure technique is introduced to fabricate the lenses. The focusing performance of this device is tested at Beijing Synchrotron Radiation Facility (BSRF). At the distance of 1.65m from the lenses, an obviously focusing performance in one dimension is observed. The relative intensity of the lenses with the largest gain is about 217.7, the gain of the lens is about 1.15, and the dimension of the focus is about 33µm. The focusing performance of this device can be improved through the developing of the mask-back exposure technique.

Rings around cones

A 65-year-old Caucasian male was referred for suspected keratoconus with Fleischer ring in both eyes. He had worn hard contact lenses since 1975 and recently changed to rigid gas permeable...

Obtaining a contact lens acquired electroretinogram in the presence of topical anesthetic hypersensitivity

Clinical circumstances often demand flexibility in electrodiagnostic procedures. We present a clinical case that required alteration of our routine full-field electroretinography technique. The patient presented with reports of allergy to Xylocaine (lidocaine) and refused the use of any type of topical anesthetic drops. This conflicted with our routine ERG method that combines the use of the Henkes Lovac hard contact lens and the topical anesthetic Alcaine (proparacaine hydrochloride). We acquired a successful electroretinogram without topical anesthesia by using a "piggy-back" system involving the interposition of a soft hydrophilic contact lens between the cornea and the recording hard lens. The procedure yielded excellent ERG recordings and was well tolerated. This non-routine technique was also compared to our standard ERG technique using a normal volunteer. It appears that this proposed "piggy-back" technique is a useful alternative to routine ERG procedure in cases of refusal/allergy to ophthalmic solutions and also potentially in cases where additional corneal protection is needed.

Stick-Slip: Wet Versus Dry

A rubber lens (polydimethylsiloxane) is pressed against silanated or bare glass plates (Johnson-Kendall-Roberts (JKR) contact). As the plate slides with a velocity U, we measure the friction on the lens using a “macro Atomic Force Microscope (AFM)”, where the cantilever is a thin rectangular glass rod and the tip is the rubber lens. We observe the contact area via optical interferometry. In air for “hard” lenses (Young's modulus E ≈ 1 MPa), we find smooth sliding on a model substrate, and a transition to stick-slip on a hysteretic substrate above a threshold velocity, V M . For soft lenses (E ≈ 0.1 MPa), we observe Schallamach waves and stick-slip depending on normal force and the plate's velocity, U. When immersed in a liquid (silicone oils, water-glycerol mixtures), the contact remains dry at low velocities, but is invaded by a liquid film above a critical velocity, U c . For hard lenses we observe smooth sliding and high friction below U c , and low friction above U c . For soft lenses, we find wet Schallamach waves for U < V M and stick-slip instabilities at large velocities. In the stick-slip regime, the contact is wet in the slip phase, and dewets in the stick phase. We measure the period of the stick-slip cycle as a function of the liquid viscosity. We interpret the stick-slip process by the formation and rupture of adhesive bonds (between the rubber polymer chains and active sites on the glass). Using a recent model, we can explain most of the data for the stick-slip period and slip threshold velocity.

Comparison of BD Multivisc™ with the Soft Shell Technique in Cases with Hard Lens Nucleus and Fuchs Endothelial Dystrophy

To compare the efficacy of 2.5% sodium hyaluronate (BD Multivisc) with the soft shell technique in reducing corneal endothelial cell damage during cataract phacoemulsification in patients with hard lens nucleus (3+) and cornea guttata. Thirty patients (37 eyes) scheduled for cataract surgery at Department of Ophthalmology and Visual Sciences, University Hospital San Raffaele, Milano, Italy. Thirty-seven eyes (randomly divided into Groups A and B) with hard lens nucleus (grade 3 or higher) and cornea guttata had phacoemulsification using the soft shell technique (Group A) with Biolon (sodium hyaluronate 1%) and Viscoat (sodium hyaluronate 3%-chondroitin sulfate 4%) or with BD Multivisc alone (Group B). Patients were evaluated preoperatively and after 1, 15, 90, and 180 days, checked for best-corrected visual acuity (BCVA), intraocular pressure (IOP), central corneal thickness, and corneal endothelial density. Stop and chop phacoemulsification technique, with burst mode (Alcon Legacy 20000, Advantec), was performed. There were no significant differences between the two groups at 3 and 6 months in BCVA, IOP, corneal thickness, or endothelial cell density. The increase of central corneal thickness (preoperative: Group A 584+/-30 microm, Group B 573+/-30 microm; postoperative at 90 days: Group A 593+/-38 microm, Group B 577+/-25 microm) was not significant. Endothelial cell loss was similar in both groups. The results suggest that the soft shell technique (Biolon, Viscoat) and 2.5% sodium hyaluronate (BD Multivisc) are both effective in protecting the corneal endothelium in Fuchs dystrophy during phacoemulsification in patients with hard lens nucleus.

Management of Scleral Defect With Phacocele

Subconjunctival dislocation of the crystalline lens is known as phacocele. Most cases of phacocele are associated with blunt trauma, existence of scleral rigidity, hard crystalline lens, and a history of scleral surgery. We report a case of traumatic phacocele with a scleral defect in a patient whom had been operated for trabeculectomy 5 years ago.

Subconjunctival lens dislocation

In their article on patients with subconjunctival crystalline lens dislocation secondary to blunt ocular trauma,1 Yurdakul and coauthors observed that all patients reported to have subconjunctival lens dislocation to date, including theirs, were older than 40 years and attributed this to the presence of a hard lens and rigid sclera as apparent prerequisites for the subconjunctival dislocation. We reported a case of posttraumatic subconjunctival dislocation of the lens and its successful management in a 16-year-old patient.2 The patient had Ehlers-Danlos syndrome type VI, and the defective collagen synthesis and susceptibility to trauma in this condition seem to be the reason for the young age at presentation. Other differences between our case and other reported cases were the unusual inferonasal subconjunctival dislocation of the lens and the long period (90 days) that the dislocated lens remained intact subconjunctivally without being absorbed. Previously, the longest duration was 2 months.3 We believe the underlying connective tissue disorder and the young age of the patient explain the findings. Yurdakul and coauthors rightly conclude that with timely intervention, the visual outcome is reasonably good. Amit Gaur MD, FRCS Yog Raj Sharma MD Rejiv Sudan MD aSheffield, United Kingdom bNew Delhi, India

Contact Lens Complications

Hans-Walter Roth Contact Lens Complications, Etiology, Pathogenesis, Prevention, Therapy 214 pages Georg Thieme Verlag, Stuttgart, New York, 2003 ISBN 1 58890 132 7 Price: $119.00 This book is an authorized translation of the German edition published in 2002. It is composed of 10 chapters concerning different aspects of the various complications associated with contact lens wear, and contains 476 illustrations, 466 of which are in colour. The bulk of the text concerns clinical descriptions and illustrations of most pathological findings in complications related to contact lens wear. The complications are classified according to anatomical position and each location begins with a short description of its anatomy and physiology. Thereafter, the different conditions are presented in terms of symptoms, clinical findings, differential diagnosis and prophylaxis. A separate chapter related to the clinical location describes the treatment for each type of condition. This clear and mainly regional method of presentation makes it easy for the ophthalmologist to access information on specific types of contact lens problems. Other chapters describe patient counselling and examination, fitting and wearing problems, and eye injuries in contact lens wearers. These chapters are marked by the author's experience in a university eye clinic attended by patients with many types of eye disease and are not necessarily representative of the experience of the majority of normal contact lens wearers. For example, the author states that despite recent advances in soft lens technology, hard lenses are still better tolerated in the longterm. I think it will be difficult to convince the general contact lens wearer of this! The book contains over five pages of references. Unfortunately these references are not related to specific statements in the text. Otherwise it could be desirable with a reference, which for instance documented the benefits of the proposed 3–6 month interval between follow-up examinations of adults wearing soft lenses. The frequency of contact lens complications is described as being between 1% and 30%. The author emphasizes that such figures are mostly based on reports that fail to state either the composition of their patient populations or the length of wearing time. Furthermore, in my opinion it is also important to distinguish between the frequencies of mild and severe complications. It is interesting that in the author's experience, 60% of contact lens complications are caused by faulty handling, cleaning or disinfection. This is important to mention in patient counselling. In conclusion, this book contains much useful information presented in a clear and short text complemented by many good illustrations. It represents excellent reference material for any ophthalmologist confronted with complications arising from contact lens wear.

Blepharoptosis in RGP and PMMA hard contact lens wearers

Background: Contact lens wear has been documented to cause an acquired non‐senile blepharoptosis. This is generally associated with prolonged wearing of hard contact lenses. The aim of this study was to determine the clinical features of blepharoptosis associated with contact lens wear including the type of contact lens and the duration of wear. Methods: This is a retrospective study of consecutive patients seen over four years (1997 to 2001) in the private practice of an oculoplastic surgeon. Results: A total of 15 consecutive patients presented over the four‐year period with blepharoptosis in the context of prolonged contact lens use. Four of the 15 patients (27 per cent) were wearing rigid gas permeable (RGP) lenses. The rest had been wearing PMMA hard lenses. Thirteen patients (87 per cent) had been wearing their contact lenses for more than 17 years. The patients' ages ranged between 15 and 71 years with a mean age of 46 years. All 15 patients had normal levator palpebrae superioris function. Four patients (27 per cent) had bilateral involvement. Eleven patients (73 per cent) underwent ptosis repair where aponeurosis thinning/dehiscence was noted. When compared with patients who presented over the same period with other causes of blepharoptosis (traumatic, myopathic, anophthalmic and involutional), contact lens wear was found to be an uncommon cause of ptosis across all age groups. Conclusion: The majority of contact lens wearers presenting with blepharoptosis gave a history of prolonged use of hard contact lenses. One explanation for this would be the mechanisms of removal of hard contact lenses. This involves pulling the lids laterally at the lateral canthus followed by a harsh blink, which over years can lead to levator aponeurosis dehiscence. Contact lens associated ptosis is an uncommon cause of acquired ptosis across all age groups.

Fixed focus: Adjustable lenses from liquid droplets

These lenses may cut the price of the assemblies of laser chips and lightmanipulating components in fiberoptic telecommunications systems, says chemist Shu Yang, a member of the Lucent team. Currently, installing such assemblies requires a technician to use an expensive micromanipulator to make time-consuming alignments of tiny, hard lenses. The droplet strategy may offer an easy-to-tweak alternative, Yang says.

The association of carbonate alteration of banded iron formation with the Carajás high-grade hematite deposits

The Carajás iron ore deposits in the eastern part of the Amazonas Craton contain approximately 18 000 Mt of hematite ore with > 66%Fe. These deposits are hosted by jaspilitic banded iron formation (BIF) of the Carajás Formation which together with metavolcanic rocks comprise the ~2·8 Ga Grao Para Group of the Itacaiunas Supergroup in the ~1000 km long by 100 km wide, eastwest trending Carajás Synclinorium. The Carajás Formation comprises discontinuous layers and lenses of partly dolomitised jaspilitic BIF (17-43%Fe and 35-61%SiO2), bodies of jaspilitic BIF and lenses of high-grade iron ore, cut by mafic sills and dykes. Dolomitisation of the BIF occurs mainly at the base of the Carajás Formation. With increasing amounts of dolomite, the BIF lamination (microbanding) and other fine primary structures are progressively obliterated resulting in irregular alternating carbonate and iron-oxide mesobands. The high-grade iron ores occur as tabular bodies of soft friable hematite with smaller lenses of hard (compact) massive hematite. The hard hematite lenses typically occur at the contact with the underlying metavolcanic rocks of the Parauapebas Formation surrounded by an aureole of hydrothermal carbonate alteration in both overlying and underlying rocks. The common association of carbonate altered and jaspilitic BIF with the Carajás hematite ore bodies is similar to the Mount Tom Price deposit where carbonate altered BIF has been recognised below massive hematite ore and a jaspilitic halo occurs above the ore body. This indicates that, as at Mount Tom Price, hydrothermal carbonate alteration and associated loss of silica from BIF may be an important step in the formation of the giant Carajás hematite deposits.

Quantification of corneal aberrations with an aberration coefficient

Abnormal corneal surfaces in keratoconus, contact lens induced corneal distorsion or after refractive surgery are thoroughly described by Zernike polynoms. This study investigated such deviations from the healthy eye by a newly introduced aberration coefficient. 300 healthy eyes were measured with videokeratometry. Corneal Zernike coefficients (grade 1. - 8. degrees ) were used to calculate the aberration coefficient. This number was also determined for 113 eyes with keratoconus (videokeratometric stage 1 to 3 - 4), 326 eyes of contact lens wearers (200 soft and 126 hard lenses) and 119 eyes after Lasik surgery. In the keratoconus group the aberration coefficient was outside normal limits in 99.2 % and correlated well with the illness stage. Corneal distorsions of low extent appeared in 5 % of soft lens wearers without a difference between yearly or disposable replacement mode. The percentage of hard lens-induced distorsions was 39 % (low extent) and 5 % (considerable extent), respectively. Only 16.8 % of eyes after Lasik had a completely normal aberration coefficient; the rest lied between 1.0 - 1.5 (62.2 %), 1.6 - 2.0 (19.3 %) and > 2.0 (1.7 %). The aberration coefficient is a helpful tool for keratoconus classification, quality control of contact lens fitting and quantification of corneal aberrations after refractive surgery. Optical aberrations of the cornea after Lasik surgery are more widespread than presumed so far and reach a considerable extent in a fifth of the operated persons.

Efficacy and safety of the soft-shell technique in cases with a hard lens nucleus

Purpose To evaluate the efficacy and safety of the soft-shell technique in reducing corneal endothelial cell damage during cataract surgery in patients with a hard lens nucleus. Setting Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan. Methods Sixty eyes of 57 cataract patients with a hard lens nucleus (Emery-Little classification grade 3 or higher) had phacoemulsification using the soft-shell technique with Healon ® (sodium hyaluronate 1%) and Viscoat ® (sodium hyaluronate 3.0%–chondroitin sulfate 4.0%) (soft-shell group) or with Healon alone (control group). The visual acuity, intraocular pressure (IOP), flare intensity in the anterior chamber, central corneal thickness, and corneal endothelial cell density were evaluated postoperatively. Results There were no significant IOP elevations in either group. The mean central corneal thickness in the control group was 539 μm ± 26.0 (SD) preoperatively and 578 ± 52.0 μm 1 day after surgery; the increase was significant ( P = .0154). There was no significant change in the central corneal thickness in the soft-shell group. There were no statistically significant differences between the 2 groups in uncorrected visual acuity, best corrected visual acuity, IOP, flare intensity in the anterior chamber, and central corneal thickness throughout the follow-up. The rate of endothelial cell loss 3 months after surgery was 6.4% ± 9.6% in the soft-shell group and 16.3% ± 9.8% in the control group ( P = .0003). Conclusion The results suggest that the soft-shell technique is safe and effective in protecting corneal endothelial cells during cataract surgery in patients with a hard lens nucleus.