Corneal Lens Research Articles

Ocular surface injury after shoulder surgery in the beach-chair position.

During shoulder surgery in the beach-chair position, head fixation can sometimes cause rare complications. The authors share their experience in treating ocular injury due to improper head fixation during surgery in the beach-chair position. The study investigated consecutively 6075 patients who underwent shoulder surgery in the beach-chair position between March 2007 and March 2016, those patients who saw an ophthalmologist with a complaint of post-operative ocular discomfort. In the beach-chair position, surgery is performed with the patient's upper body raised by 70°. A total of seven patients saw an ophthalmologist due to post-operative ocular discomfort, and a total of five patients (0.082%) had corneal abrasion. Three of these patients underwent arthroscopic surgery, and the other two underwent open surgery. The mean surgery duration for the five patients was 45.0 ± 14.68minutes. Of these patients, four were male and one was female, and their average age was 46 ± 22.24years (range: 18-69years). All patients complained of unbearable ophthalmodynia immediately after surgery that was not resolved using analgesics. The ophthalmodynia resolved immediately after wearing corneal protective lenses. Unlike typical surgery, when shoulder surgery is performed in the beach-chair position, there is a risk of ocular surface injury due to improper head fixation; one manifestation of this problem is corneal injury. If a severe ophthalmodynia that cannot be controlled using analgesics occurs immediately after surgery in the beach-chair position, a corneal injury should be suspected, and the patient should wear a corneal protective lens. Level IV.

Is combined mechanism glaucoma a distinct entity?

Primary adult glaucomas that have an occludable angle with peripheral anterior synechiae which are too few to account for the chronically raised IOP, or the glaucomatous optic neuropathy, do not fit the definition of either POAG or PACG and can be considered as combined mechanism glaucoma (CMG). We aimed to compare the clinical features and anatomical parameters of combined mechanism glaucoma with age, sex, and refraction-matched POAG and chronic PACG eyes. Consecutive adult patients with definitive optic nerve head and perimetric changes of glaucoma were screened at a tertiary care center. All glaucomatous eyes having an IOP > 22mmHg on at least three separate occasions and glaucomatous optic neuropathy consistent with moderate visual field loss in the eye were divided as POAG, PACG, and CMG. Eyes with occludable angles having < 90° of goniosynechiae were diagnosed as CMG. A detailed clinical examination, ocular biometry, and ASOCT were performed in the better eye of all individuals. A total of 93 patients with similar visual field index or pattern standard deviation on perimetry were evaluated: 32 POAG, 31 CMG, and 30 PACG. The mean anterior chamber depth was 3.47 ± 0.37mm in POAG, 2.81 ± 0.32mm in PACG, and 3.06 ± 0.26mm in CMG (p < 0.0001). Mean lens thickness was 4.22 ± 0.27mm in POAG, 4.53 ± 0.35mm in PACG, and 4.44 ± 0.29mm in CMG (p = 0.0004). Iridotrabecular contact on ASOCT was nil in POAG, a mean of 87.60 ± 12.802% in PACG eyes, and 15.23 ± 14.19% in CMG eyes, p < 0.0001. CMG was similar to PACG in terms of corneal diameters and lens thickness and had an axial length in between PACG and POAG. On ASOCT, all parameters had highest values in POAG eyes and the least in PACG eyes, with CMG eyes having values in between the other two groups, p value of < 0.0001 between each group for all parameters. This study has demonstrated significantly different anatomical parameters in eyes with CMG, in addition to the differences on gonioscopy and iridotrabecular contact, indicating that CMG is discernibly dissimilar to PACG and POAG.

Directed Differentiation of Human Corneal Endothelial Cells From Human Embryonic Stem Cells by Using Cell-Conditioned Culture Media.

A shortage of human corneal endothelial cells (HCEC) for transplant and current methods of differentiation induction require chemical compounds, which might cast further influences after differentiation induction. Therefore, we developed a simple and straightforward approach to endothelial cell differentiation from human embryonic stem cells (hESC). HESC are used to differentiate into HCEC by employing a two-stage method, which involves the application of two different types of conditioned culture medium, human corneal stromal cell-conditioned medium (HCSC-CM) and lens epithelial cell (LEC) plus HCSC-CM (LEC-CM+HCEC-CM). In brief, hESCs were treated with different conditioned media to induce directed endothelial differentiation. In the presence of conditioned culture medium, embryonic stem cells differentiate first under the control of periocular mesenchymal precursors (POMPs). Consequently, the expression of several POMP markers was observed. Following this first stage differentiation, POMPs were further directed to differentiate into corneal endothelial cell (CEC)-like cells in the presence of the second-conditioned culture medium. The differentiation of POMPs into CEC-like cells is regulated by a TGFβ-2/FOXC1 signaling pathway that is activated by the factors present in the conditioned culture medium. HCEC-like cells could be differentiated from hESC by simply using a two-step, preconditioned, medium-mediated approach, which could significantly minimize the workload to generate HCEC for potential clinical use. This research may provide an ideal cell source for corneal regenerative medicine and clinical treatment for corneal diseases in the future.

Clinical management of pellucid marginal degeneration (PMD) using scleral rigid contact lenses: A case report

A 55-year-old male, KMI, presented to our Optometry clinic for contact lens fitting. The patient complained about blurry distant vision and high astigmatism in both eyes. He denied any remarkable ocular and general health history. After a comprehensive eye examination, the patient was diagnosed to have pellucid marginal degeneration in both eyes, with remarkable inferior corneal steepening and thinning. Multi-curve RGP lenses (Rose K2) with different parameters and piggyback back system were fitted to the patient. However, optimal lens fitting could not be obtained due to his irregular and inferiorly steepened cornea. Scleral RGP contact lenses (ICD 16.5) were then refitted to him. Both visual and fitting performances of the lenses were good during delivery. However, after the patient wore the contact lenses for a month, the lens vaulting thickness reduced significantly due to lens settling, and causing lens bearing in OS. Therefore, lenses with increased lens sag, especially at the limbal and peripheral corneal regions were refitted for the patient. Both visual and fitting performances of the lenses were good. Subjective feeling and corneal health condition were optimal during the subsequent aftercare consultations. In the early stage, PMD can be managed using spectacles or normal soft contact lenses, or at moderate stages, using spherical, bitoric or quadrant specific corneal RGP lenses. However, in advanced stages, as the inferior corneal steepening increases, corneal lenses system may not be able to provide an acceptable fitting, which may result in heavy bearing and excessive inferior edge stand-off. In contrast, With adequate sag, scleral lens can be fitted on eyes with severe corneal distortion without inducing any bearing on the cornea, therefore, lens fitting and visual performance can be significantly improved.

UV light crosslinking regresses mature corneal blood and lymphatic vessels and promotes subsequent high-risk corneal transplant survival.

Immunologic graft rejection is the main complication after corneal transplant into pathologically prevascularized so‐called high‐risk eyes. The aim of this study was to evaluate whether ultraviolet (UV) light crosslinking can regress pathologic corneal blood and lymphatic vessels and thereby improve subsequent graft survival. Using the murine model of suture‐induced corneal neovascularization, we found that corneal crosslinking with UVA light and riboflavin regressed both preexisting blood and lymphatic vessels significantly via induction of apoptosis in vascular endothelial cells. In addition, macrophages and CD45+ cell counts were significantly reduced. Consistently, corneal crosslinking reduced keratocyte density and corneal thickness without affecting corneal nonvascular endothelial cells, iris, and lens depending on the crosslinking duration. Furthermore, using the murine model of corneal transplant, long‐term graft survival was significantly promoted (P < .05) and CD4+ CD25+FoxP3+ T regulatory cells were upregulated (P < .01) in high‐risk eyes preoperatively treated with crosslinking. Our results suggest UV light crosslinking as a novel method to regress both pathologic corneal blood and lymphatic vessels and to reduce CD45+ inflammatory cells. Furthermore, this study demonstrates for the first time that preoperative corneal crosslinking in prevascularized high‐risk eyes can significantly improve subsequent graft survival and may become a promising novel therapy in the clinic.

Protective efficacy of bandage lens on corneal flap of patients with retinal detachment after LASIK surgery

Objective To evaluate the protective efficacy of bandage contact lens on corneal flap for retinal detachment patients with LASIK history. Methods A prospective, self-controlled clinical study. Nine eyes of 9 patients with retinal detachment who had history of LASIK were enrolled. All cases underwent vitreoretinal surgery with non-contact wide-angle lens. Corneal bandage lenses were used to completely cover the surface of the corneal flap during surgery. The visual acuity, IOP, corneal fluorescein sodium staining, tear function, corneal thickness and corneal endothelial cell density at 1 d, 1 week and 1 month postoperatively were recorded. Results No corneal flap displacement or loss occurred in 9 cases. Before surgery corneal fluorescein staining showed scattered cornea around the next spot color in 7 cases. The score of corneal fluorescein staining was (2.00±0.87) 1 d after surgery, it was higher than that before surgery (t=-5.547, P=0.001). The score returned to preoperative level at 1 week after surgery. BUT was agreement with results of corneal fluorescein sodium staining. The corneal thickness at 1 week after surgery was (531.78±24.17)μm, it was thicker than that before surgery(t=-4.918, P=0.001). The difference of corneal thickness was not statistically significant between before and 1 month after surgery. The difference of Schirmer Ⅰtest and corneal endothelial cell density were not statistically significant between before and after surgery. Conclusion Application of corneal bandage lens for retinal detachment patients with history of LASIK can protect corneal flap, recovery early of tear film stability, effectively protect the corneal function. Key words: Retinal detachment, after surgery, laser in situ keratomileusis(LASIK); Vitreoretinal surgery; Bandage contact lens; Corneal flap

Scleral Lens Hygiene and Care

Scleral lenses (ScCLs) are developed using the same material as rigid gas permeable corneal lenses yet the care of scleral lenses differs from corneal lenses. These large diameter rigid gas permeable lenses necessitate hygiene, care and compliance protocol that is more complex compared with corneal lenses. Cleaning, disinfection, storing, rinsing and applying ScCL will be discussed. Practitioners will gain confidence in ScCL care which will provide patients with a better understanding of the steps involved in ScCL disinfection leading to increased patient compliance and increased success rates. In turn, patient education will lower the risk for infection and other complications associated with ScCL.

Wedge resection of the tarsal plate combined with the modified Hotz procedure for correction of involutional lower eyelid entropion

ObjectivesTo investigate the outcomes for correction of involutional lower eyelid entropion by wedge resection of the tarsus combined with the modified Hotz procedure. DesignRetrospective study. ParticipantsPatients with lower eyelid involutional entropion that was surgically repaired by wedge resection of the tarsal plate combined with the modified Hotz procedure. MethodsIn a consecutive series of 43 patients with involutional lower eyelid entropion, wedge resection combined with the modified Hotz procedure was performed with an average follow-up period of 29.6 months (range, 6–62 months). ResultsAmong the patients, 93% had an excellent outcome within the follow-up period. For one patient, the outcome of both eyes was poor. For another patient, incision dehiscence of the eyelid margin in one eye occurred after the stitches were removed. The incision was sutured again, and it healed well. One patient complained of foreign body sensation in one eye after removal of the skin stitches. The complaint was resolved after wearing a corneal contact lens. No other significant complications occurred. ConclusionsIn our clinic, tarsal plate wedge resection combined with the modified Hotz procedure has been highly effective for correction of involutional lower eyelid entropion. Although this approach does not directly address lateral canthal tendon laxity, it does preserve the eyelid in case there is a future need for reconstruction due to ocular surface disease or trauma. Thus, wedge resection of the tarsal plate combined with modified Hotz procedure is a safe and effective method for involutional lower eyelid entropion.

Comparison of clinical outcomes between femtosecond laser-assisted versus conventional phacoemulsification

BackgroundTo compare femtosecond laser-assisted versus conventional phacoemulsification in terms of visual and refractive outcomes, cumulative dissipated energy, anterior chamber inflammation and endothelial cell loss.MethodsIn this retrospective cohort study, records of eyes that underwent femtosecond laser-assisted cataract surgery (FLACS) or conventional phacoemulsification (CP) were reviewed. The Victus femtosecond laser (Bausch and Lomb, Germany) was used to carry out corneal incisions, anterior capsulotomy, and lens fragmentation in FLACS procedures. Manifest refraction spherical equivalence (MRSE), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), cumulative dissipated energy (CDE), postoperative cells and flare and endothelial cell count data were collected. Subgroup analysis of the visual acuity tests was performed based on the type of intraocular lens implanted (monofocal, monofocal toric, multifocal, multifocal toric, accommodating).ResultsA total of 735 eyes were included in the study (296 eyes for the FLACS group and 439 eyes for the CP group). At one year follow-up, 120 eyes comprised the FLACS group and 265 eyes for the CP group. MRSE in the FLACS group was − 0.16 ± 0.58 D and − 0.20 ± 0.52 D in the CP group (P = 0.50). UDVA in the FLACS group was 20/25 (mean logMAR 0.12 ± 0.13) and 20/25 (mean logMAR 0.11 ± 0.13) in the CP group (P = 0.48). CDVA was 20/20 (mean logMAR 0.03 ± 0.07) in the FLACS group and 20/20 (mean logMAR 0.02 ± 0.06) in the CP group (P = 0.15). No statistically significant trend was seen for FLACS versus CP by intraocular type for visual acuity. CDE for the different cataract grades ranged from 6.97 ± 5.74 to 29.02 ± 16.07 in the FLACS group and 7.59 ± 6.42 to 35.69 ± 18.30 in the CP group. The FLACS group was significantly lower for post-operative central corneal edema (P = 0.05), cells and flare (P = 0.01), and endothelial cell loss (P = 0.04).ConclusionsFemtosecond laser-assisted cataract surgery and conventional phacoemulsification had similar refractive and visual outcomes. Phacoemulsification energy, anterior chamber inflammation and corneal endothelial cell loss were less in the femtosecond laser group.

Microscopic scleral buckling under direct vision with application of corneal contact lens

Objective To study the efficacy of microscopic scleral buckling under direct vision using corneal contact lens for the treatment of rhegmatogenous retinal detachment. Methods The data of 40 eyes of 40 consecutive clinical cases with rhegmatogenous retinal detachment from Jul. 2012 to Dec. 2014 were collected and analyzed retrospectively. They underwent surgery of microscopic scleral buckling under direct vision with application of corneal contact lens. Twenty-six cases were male, and 14 cases were female. The age ranged from 13 to 87 years, average (34.48±16.47) years. The course of disease was 3-180 d, average (36.20±4.80) d. The follow-up time was 1 year. Results Accurate retinal hole localization were done in all 40 cases. The retina was reattached in 39 cases (97.50%). One case (2.50%) with jelly-like subretinal fluid received vitrectomy due to failed of retinal reattachment. During the surgery, a new retinal tear was found in 1 case after transcleral outflow drainage of subretinal fluid, and the tear was accurately localized and cryocoagulated immediately. There was no other complication in operation. BCVA was significantly improved after surgery (t=6.794, P=0.000). Conclusion Microscopic scleral buckling under direct vision with application of corneal contact lens is a recommendable surgery for rhegmatogenous retinal detachment. It can provide good retinal reattachment with less complications, with supplying clear operation view, accurate retinal tear localization, and appropriate cryotherapy and buckling. Key words: Retinal detachment; Scleral buckling, under direct vision; Corneal contact lens

Risk factor analysis of persistent corneal epithelial defects after vitrectomy in patients with proliferative diabetic retinopathy

Objective To analyze the risk factors for persistent corneal epithelial defects (PCED) after pars plana vitrectomy (PPV) in patients with proliferative diabetic retinopathy (PDR). Methods A total of 201 PDR patients (201 eyes) who received PPV were enrolled in this retrospective study. There were 86 males (86 eyes) and 115 females (115 eyes). The patients aged from 30 to 81 years, with the mean age of (57.94±9.65) years. Among them, 159 patients were ≥50 years of age, and 42 patients were 1000 points were performed in 123 eyes. Sixty-one eyes involved intravitreal silicone oil tamponade, 18 eyes involved intravitreal tamponade with C3F8, and 122 eyes were not involved with intraocular tamponade. Postoperative persistent intraocular hypertension was defined as an intraocular pressure (IOP) ≥21 mmHg (1 mmHg=0.133 kPa) after PPV with necessary treatment using IOP-lowering medications for ≥2 weeks. The diagnostic criteria for corneal epithelial defects were taken from the Expert Consensus on Clinical Diagnosis and Treatment of Corneal Epithelial Defect in China (2016). The corneal epithelial defect was diagnosed as PCED if it was treated with common methods such as a lacrimal substitute or corneal contact lens, but showed no improvement and no signs of healing for ≥2 weeks. The incidence of PCED after eye surgery was recorded and its related risk factors were analyzed. A multivariate logistic regression was used to analyze the risk factors for PCED, which were expressed as a odds ratio (OR) and a 95% confidence interval (CI). Results Of 201 eyes, 16 eyes (7.96%) presented with PCED after surgery and 185 eyes (92.04%) with no PCED. There was no significant difference in the age, sex, and eyes between the patients with or without PCED (χ2=6.548, 0.927, 0.044; P=0.011, 0.336, 0.833). A multivariate logistic regression showed that intraoperative epithelial debridement (OR=13.239, 95%CI 2.999−58.442, P=0.001), intraoperative treatment in combination with cataract surgery (OR=7.448, 95%CI 1.975−28.091, P=0.003), intravitreal tamponade with C3F8 (OR=11.344, 95%CI 2.169−59.324, P=0.004), and postoperative persistent intraocular hypertension (OR=10.462, 95%CI 2.464−44.414, P=0.001) were risk factors for PCED after PPV. Conclusion Intraoperative epithelial debridement, intraoperative treatment in combination with cataract surgery, intravitreal tamponade with C3F8, and postoperative persistent intraocular hypertension are risk factors for PCED in patients with PDR after PPV. Key words: Epithelium, corneal/injuries; Vitreoretinal surgery; Diabetic retinopathy

Correlation of Corneal and Scleral Pneumatonometry in Pediatric Patients

To study the correlation between corneal and scleral intraocular pressure (IOP) by pneumatonometry in pediatric patients. Cross-sectional study. Patients (age range, 0-15 years) undergoing an eye examination under anesthesia or eye surgery were recruited at the University of California, San Francisco, Benioff Children's Hospital between July 2015 and April2016. Intraocular pressure measurements were obtained by pneumatonometry on the central cornea and the inferonasal and inferotemporal sclera in a random order. Spearman correlations between corneal versus inferonasal scleral IOP and corneal versus inferotemporal scleral IOP were calculated. A linear mixed-effect model was used to derive a predictive equation for corneal IOP from scleral IOP and to perform covariate analysis for age, axial length, central corneal thickness, and lens status. The standard deviation of the predicted corneal IOP was determined by bootstrap mixed-effect regression analysis. The predictive model of corneal IOP from scleral IOP. Seventy-five eyes from 40 patients were included in the study. Spearman correlation coefficient for corneal versus inferotemporal scleral IOP was 0.79 (P < 0.01) and 0.48 for corneal versus inferonasal scleral IOP (P<0.01). Corneal IOP may be predicted from scleral IOP via the following equations: corneal IOP= 0.73× inferotemporal scleral IOP+ 7.45 and corneal IOP= 0.21× inferonasal scleral IOP+ 17.83. Central corneal thickness (P= 0.07), lens status (P= 0.4), age (P= 0.33), and axial length (P= 0.15) did not affect significantly the relationship between corneal and scleral IOP in the multivariate regression analysis. The standard deviation of predicted corneal IOP was less than 1.2 mmHg within an inferotemporal scleral IOP range of 10 to 35 mmHg. In children, corneal and scleral IOP are correlated significantly when measured by pneumatonometry. Measurements obtained from the inferotemporal sclera are better predictors of corneal IOP than those obtained from inferonasal sclera. Pneumatonometry on the inferotemporal sclera may be an alternative method to estimate IOP for pediatric patients from whom corneal IOP measurement is difficult to obtain.

Clinical research of corneal bandage contact lens in prevention and treatment of ocular surface diseases

The corneal contact bandage lens has gained clinicians acceptance for their wearing comfort and definite curative effects in ocular surface protection and damage reparation.Recently, application fields of contact bandage lens are still expanding with continuous exploration and development of new materials and function.To non-infectious ocular surface diseases, bandage lens obviously alleviate irritate symptoms and accelerate tissue healing.The application of bandage lens in infectious ocular surface diseases remains controversial.The bandage lens has become a routine intervention of ocular trauma and corneal perforation.It can also improve ocular surface microenvironment after the surgery of glaucoma, cataract, pterygium, corneal transplantation and refraction.It is an adjuvant therapy for aniridia, dry eye and children ocular surface diseases.This review summarized the history, current corneal contact bandage lens in preventing and treating ocular surface diseases. Key words: Corneal contact lens; Bandage lens; Ocular surface diseases; Clinical research

Cornea and anterior eye assessment with placido-disc keratoscopy, slit scanning evaluation topography and scheimpflug imaging tomography.

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple and several devices and technologies allow to explore and to manage patients. The purpose of this special issue is to present and also to update in the evaluation of cornea and ocular surface and this second part, reviews a description of the corneal topography and tomography techniques, providing updated information of the clinical recommendations of these techniques in eye care practice. Placido-based topographers started an exciting anterior corneal surface analysis that allows the development of current corneal tomographers that provide a full three-dimensional reconstruction of the cornea including elevation, curvature, and pachymetry data of anterior and posterior corneal surfaces. Although, there is not an accepted reference standard technology for corneal topography description and it is not possible to determine which device produces the most accurate topographic measurements, placido-based topographers are a valuable technology to be used in primary eye care and corneal tomograhers expanding the possibilities to explore cornea and anterior eye facilitating diagnosis and follow-up in several situations, raising patient follow-up, and improving the knowledge regarding to the corneal anatomy. Main disadvantages of placido-based topographers include the absence of information about the posterior corneal surface and limited corneal surface coverage without data from the para-central and/or peripheral corneal surface. However, corneal tomographers show repeatable anterior and posterior corneal surfaces measurements, providing full corneal thickness data improving cornea, and anterior surface assessment. However, differences between devices suggest that they are not interchangeable in clinical practice.

Analysing the ocular biometry of new-born infants.

To model and analyse the ocular biometry of new-born infants. This work is based on previously published data of a cohort of 66 new-born infants aged 0-3days. After exclusion of seven myopic subjects, the available retinoscopy, keratometry and ultrasound biometry data were analysed, along with calculated parameters such as lens power and whole eye power. Male infants have significantly flatter corneas that female infants (Mann-Whitney U test, p<0.001), which was associated with a difference in gestational age between genders (multiple linear regression; p=0.043). No other gender-based differences were seen. Corneal curvature (Pearson, r=0.575; p<0.001), lens power (r=-0.681; p<0.001), and anterior chamber depth (r=0.654; p<0.001) were all correlated to axial length, but not refraction (r=-0.114; p=0.42). Most ocular parameters were associated with gestational age (linear regression analysis; p<0.05), rather than birth length, birth weight, fertilization method or parental myopia (all p>0.05), suggesting scaled eye growth during the last weeks before birth. Multivariate Gaussian analysis demonstrated that a statistical eye model can be defined that generates synthetic data that is significantly equal to the original data (non-parametric Mann-Whitney test for equality; all p<0.05), with similar variability (non-parametric Levene test; all p>0.05). The eye undergoes a scaled growth until birth, at which time male and female infants have similar values. The models presented may serve as an early biometry reference.

Ocular biometric changes with different accommodative stimuli using swept-source optical coherence tomography.

To evaluate ocular biometric changes with different accommodative stimuli using a new swept-source optical biometer. Only the right eye was analyzed. Each subject was measured six times with the IOLMaster 700 swept-source optical biometer (Carl Zeiss Meditec, Jena, Germany) with the subject looking at the stimulus shown by the instrument and with the subject looking at a target placed outside the instrument at 0D of vergence. Axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT), white-to-white (WTW), and keratometry readings (K1 and K2) were evaluated in both cases. To assess if the changes found may affect the intraocular (IOL) power calculation for surgical applications, we have applied some formulae, using the software provided by the optical biometer manufacturer, to the ocular parameters found in both situations for three different types of IOLs. No statistically significant differences were found for AL, CCT, WTW, K1 and K2 between the subject looking at the stimulus of the biometer and looking at the outside target at 0D of vergence (p>0.05). However, the measurement of ACD revealed a statistically significant reduction of 20 microns (p=0.03) and, on the contrary, LT increased significantly 30 microns (p=0.02). ACD and LT changes were highly correlated (R2=0.91). As for the IOL power calculation, in all cases, the mean change was lower than 0.25 D both for IOL power selection and residual refraction. Although ACD and LT change significantly with different accommodative stimuli measured by swept-source optical biometry, these changes are not clinically relevant.

Scleral Lenses Reduce the Need for Corneal Transplants in Severe Keratoconus

To investigate the success and failure rates of scleral lens correction in severe keratoconus. Retrospective case series. Study population comprised patients with keratoconus who attended the keratoconus clinic at the Antwerp University Hospital, Belgium, between January 1, 2010, and December 31, 2014. The included eyes had maximal keratometry values ≥ 70 diopters, as measured using the sagittal curvature map that was obtained by Scheimpflug tomography. The exclusion criteria included amblyopia, mental retardation, and concomitant ocular disease that limited their visual potential. Scleral lens fitting was proposed for the 75 eyes included in the study. Eight eyes underwent transplant surgery because of insufficient visual acuity with the lenses, lens intolerance, and issues with handling the lenses. Twelve eyes did not have lenses fitted because of good visual acuity in the other eye or a contraindication for lens wear. Three eyes were successfully fitted with corneal or hybrid lens wear. Scleral lenses were prescribed in 51 of 75 eyes. The mean gain in visual acuity (lens vs spectacle-corrected visual acuity) was 0.54 ± 0.18 (decimal fraction, Snellen eye chart). Seven eyes were lost to follow-up, 4 eyes abandoned wearing the scleral lens because of an inability to handle the lenses, and 40 eyes wore the lenses at their last follow-up visit, with a mean follow-up interval of 30.15 ± 12.83months. Forty of the 51 eyes with severe keratoconus that would otherwise have undergone transplant surgery were successfully treated with long-term scleral lens wear. In this way, the indication for keratoplasty was more than halved in our keratoconus population.

Phacoemulsification on the Eye with Corneal and Iridal Perforation and Anterior Lens Capsule Disruption by Cat Claw in a Miniature Poodle Dog

Phacoemulsification on the Eye with Corneal and Iridal Perforation and Anterior Lens Capsule Disruption by Cat Claw in a Miniature Poodle Dog

A Complex Lens for a Complex Eye

A key innovation for high resolution eyes is a sophisticated lens that precisely focuses light onto photoreceptors. The eyes of holometabolous larvae range from very simple eyes that merely detect light to eyes that are capable of high spatial resolution. Particularly interesting are the bifocal lenses of Thermonectus marmoratus larvae, which differentially focus light on spectrally-distinct retinas. While functional aspects of insect lenses have been relatively well studied, little work has explored their molecular makeup, especially in regard to more complex eye types. To investigate this question, we took a transcriptomic and proteomic approach to identify the major proteins contributing to the principal bifocal lenses of T. marmoratus larvae. Mass spectrometry revealed 10 major lens proteins. Six of these share sequence homology with cuticular proteins, a large class of proteins that are also major components of corneal lenses from adult compound eyes of Drosophila melanogaster and Anopheles gambiae. Two proteins were identified as house-keeping genes and the final two lack any sequence homologies to known genes. Overall the composition seems to follow a pattern of co-opting transparent and optically dense proteins, similar to what has been described for other animal lenses. To identify cells responsible for the secretion of specific lens proteins, we performed in situ hybridization studies and found some expression differences between distal and proximal corneagenous cells. Since the distal cells likely give rise to the periphery and the proximal cells to the center of the lens, our findings highlight a possible mechanism for establishing structural differences that are in line with the bifocal nature of these lenses. A better understanding of lens composition provides insights into the evolution of proper focusing, which is an important step in the transition between low-resolution and high-resolution eyes.

Prediction of Orthokeratology Lens Decentration with Corneal Elevation

Lens decentration is common and unavoidable to some extent during ortho-k treatment. By using a simplified method, we are able to predict the magnitude and direction of ortho-k lens decentration, which provides useful insights in screening for ideal ortho-k candidates and to make a quick decision when decentration happens. The aim of this study was to investigate the influence of corneal elevation asymmetry on ortho-k lens decentration. Thirty-six eyes of 36 subjects were fitted with four-curve reverse geometry ortho-k contact lenses. Corneal topography was collected before and 1 month after ortho-k lens wear. The difference in corneal elevation at the 8-mm chord of the respective two principal meridians of corneal astigmatism was calculated. Vector analyses were performed on these differences to calculate the magnitude and direction of a vector (corneal asymmetry vector). The relationship between the angle and magnitude of corneal asymmetry vector and lens decentration was analyzed. Baseline refractive sphere and cylinder for the 36 tested eyes were -2.84 ± 1.04 diopters (D) (range, -4.75 to -1.00 D) and -0.21 ± 0.28 D (range, -1.00 to 0 D), respectively. The mean magnitude of lens decentration was 0.72 ± 0.26 mm (0 to 1.34 mm). For overall displacement, inferotemporal decentration was the most common as observed in 24 eyes (67%). The mean angle of the corneal asymmetry vector (202 ± 39 degrees) was significantly correlated to the mean angle of lens decentration (200 ± 39 degrees) (r = 0.76, P < .001). The magnitude of corneal asymmetry vector significantly contributed to the magnitude of lens decentration (standardized β = 0.448, P = .002) whereas the other tested variables did not affect lens decentration (all P > .05). Lens decentration is a common phenomenon in ortho-k that mostly happens toward the inferotemporal quadrant of the cornea. The magnitude and direction of lens decentration are predetermined by paracentral corneal asymmetry.