Clinical outcomes and complications of fluid-filled scleral lens devices for the management of limbal stem cell deficiency

AimsTo evaluate the clinical and visual outcomes of fluid-filled scleral lens devices (SL) wear in patients with limbal stem cell deficiency (LSCD).DesignRetrospective consecutive case series.Methods27 eyes with LSCD confirmed by in vivo confocal microscopy at the Stein Eye Institute and fitted with SL were included. Correlations between corrected distance visual acuity (CDVA) and LSCD stage determined by clinical grading were performed between baseline (after the SL fit) and the last follow-up (the time of discontinuation of SL wear or the last visit in eyes in which SL were continued). In a subset of patients that had worsened LSCD while using SL, anterior segment optical coherence tomography (AS-OCT) and anterior segment fluorescein angiogram (AS-FA) were performed.ResultsBaseline LSCD grading was stage I in 12 eyes (44.4%), stage 2 in 12 eyes (44.4%), and stage III in 3 eyes (11.1%). At the last follow-up, CDVA was improved in 7 eyes (25.9%), remained stable in 13 eyes (48.1%) and decreased in 7 eyes (25.9%, P = 0.16). The LSCD stage was improved in 7 eyes (25.9%), remained stable in 8 eyes (29.6%) and worsened in 12 eyes (44.4%, P = 0.10). AS-OCT and AS-FA, performed in 5 eyes, showed limbal compression and delayed fluorescein filling.ConclusionSL can improve visual acuity and maintain the ocular surface in the majority of eyes. Worsening of the ocular surface might be a result of limbal hypoxia. Close monitoring of SL fit is necessary in these compromised eyes.     

Recovering vision in corneal epithelial stem cell deficient eyes

A healthy corneal epithelium, which is essential for proper vision and protection from external pathogens, is continuously replenished throughout life by stem cells located at the limbus. In diseased or injured eyes, however, in which stem cells are deficient, severe ocular problems manifest themselves. These are notoriously difficult to manage and as a result the last 20 or so years has seen a number of therapeutic strategies emerge that aim to recover the ocular surface and restore vision in limbal stem cell deficient eyes. The dominant concept involves the generation of laboratory cultivated epithelial cell sheets expanded from small biopsies of the epithelial limbus (for patient or donors) or another non-corneal epithelial tissue such as the oral mucosa. Typically, cells are grown on sterilised human amniotic membrane as a substrate, which then forms part of the graft, or specially formulated plastic culture dishes from which cells sheets can be released by lowering the temperature, and thus the adherence of the plastic to the cells. Overall, clinical results are promising, as is discussed, with new cultivation methodologies and different cell lineages currently being investigated to augment the treatment options for visual disturbance caused by a corneal epithelial limbal stem cell deficiency.     

A pilot study investigating the effect of extended contact lens wear on limbal and central corneal morphology

PurposeTo investigate the effect of long-term extended soft contact lens wear on limbal and central corneal cell morphology, and limbal architecture.MethodsEach participant attended a study visit involving in vivo confocal microscopy of central corneal and limbal epithelium. Scans were graded by five masked graders for three features: central epithelial irregularity, limbal epithelial irregularity and the prominence of palisades of Vogt. The variability of grades between different graders and the difference of grades between extended wearers and daily soft/non-contact lens wearers were assessed.ResultsNineteen participants (9 extended soft contact lens wearers and 10 daily soft/non-contact lens wearers) aged 31–65 years were enrolled in this study. Scans from 37 eyes were included in the analysis. Agreement between graders for each feature was moderate to good with inter class correlation >0.7. While there were no significant differences in central epithelial cell irregularity (p = 0.527) and the prominence of palisade of Vogt (p = 0.182) between extended or daily soft/non-contact lens wearers, limbal epithelial cell irregularity showed a trend with increased irregularity in extended soft contact lens wearers (p = 0.091).ConclusionsWhile no differences in limbal cell morphology and structure or central epithelial cell was found in this subjective grading study of extended wearers compared to daily soft/non-contact lens wearers, further studies using a larger sample size or a longitudinal study design are warranted.     

The influence of limbal and scleral shape on scleral lens design

Purpose

To summarize the research findings on the ocular surface profile, to provide a definition and a classification of the corneoscleral shape, and to offer guidelines in selecting scleral lens design.

Review of 20 years of soft contact lens wearer ocular physiology data

BackgroundSince the introduction of Silicone hydrogel (SiHy) contact lenses 20 years ago, industry has continued to modify lens materials, designs, lens care products and manufacturing processes, striving to improve contact lens physiological performance, comfort, and convenience for wearers. The purpose of this study was to investigate whether the ocular health of habitual soft contact lens wearers today is better than it was in previous decades.MethodsBaseline ocular physiology data for 3624 participants from a The Brien Holden Vision Institute clinical trials database were retrospectively reviewed. Records were grouped into 3 time periods; A: >2 decades ago (1997–1999), B: one decade ago (2009–2014) and C: recent years (since 2015). Physiology data for both neophytes and habitual contact lens wearers included; bulbar, limbal and upper palpebral conjunctival redness, corneal and conjunctival staining and conjunctival indentation from contact lenses.ResultsCorneal staining levels are similar between neophytes and contact lens wearers at time points A and C but worse for contact lens wearers at time point B. Limbal redness was greater in contact lens wearers than in neophytes at time point A but at time points B and C they are not different to the non-contact lens wearing population. In recent years, most ocular physiological variables in habitual contact lens wearers are similar to neophytes.ConclusionsWhile there have been changes over the past two decades in ocular physiological responses to contact lens wear, it appears that ocular health with current day contact lens wear is similar to no lens wear in most respects.     

Non-invasive objective and contemporary methods for measuring ocular surface inflammation in soft contact lens wearers – A review

Contact lens wear is one of the primary risk factors for the development of ocular surface inflammatory events. The purpose of this review is to examine and summarize existing knowledge on the mechanisms of contact lens related ocular surface inflammation and the evidence for the effectiveness of current objective methods to measure ocular surface inflammation. Contact lens wear is postulated to trigger an inflammatory response on the ocular surface due to mechanical, chemical, hypoxic stress, or by the introduction of microbes and their toxins. Apart from the traditional signs of inflammation, such as swelling, oedema, redness and heat, on the ocular surface, other methods to measure ocular surface inflammation in sub-clinical levels include tear inflammatory mediator concentrations, conjunctival cell morphology, and corneal epithelial dendritic cell density and morphology. Tear inflammatory mediator concentrations are up- or down-regulated during contact lens wear, with or without the presence of associated inflammatory events. There is higher conjunctival cell metaplasia observed with contact lens wear, but changes in goblet cell density are inconclusive. Dendritic cell density is seen to increase soon after initiating soft contact lens wear. The long term effects of contact lens wear on dendritic cell migration in the cornea and conjunctiva, including the lid wiper area, require further investigation. Currently patient factors, such as age, smoking, systemic diseases and genetic profile are being studied. A better understanding of these mechanisms may facilitate the development of new management options and strategies to minimize ocular surface inflammation related to contact lens wear.     

Ocular health of children wearing daily disposable contact lenses over a 6-year period

PurposeTo report on the ocular health and safety of children fit with soft hydrogel daily-disposable contact lenses, and followed for 6-years in a double-masked clinical trial investigating the performance of a dual-focus contact lens designed to control myopia progression.MethodsChildren aged 8−12 years, naïve to contact lens wear, were enrolled across four international sites. During years 1–3, children were randomised to either MiSight® 1 day or Proclear® 1 day (both omafilcon A, CooperVision, Inc.). The lenses were identical in material and geometry except for the front optical zone design. At the end of year-3, all those wearing Proclear 1 day were switched to MiSight 1 day, therefore all wore MiSight 1 day in years 4−6. Subjects agreed to wear the lenses at least 10-hours/day, 6-days/week. After dispensing, study visits were at 1-week, 1-month, 6-months and every 6-months until 6-years. At each visit, ocular measurements and subjective responses were recorded. Biomicroscopy used 0–4 grading scales; grade 0 represented no findings.Results144 children were enrolled: 69F:75M; mean age 10.1 years; mean cycloplegic spherical-equivalent refraction -2.11D; ethnicities included 34 East-Asian, 12 West-Asian, and 79 Caucasian. 92 completed the 6-years. Only three subjects discontinued due to an ocular adverse event (AE). No contact lens related AEs were classified as serious. The incidence rate of infiltrative AEs was 0.61% (6.1/1000 wearing-years; 95%CI: 0.24%–1.57%). The most common biomicroscopy findings were limbal, bulbar and tarsal hyperaemia and tarsal roughness. 99% of all biomicroscopy findings were grade-1 or lower. After 6-years of lens wear, ocular health by biomicroscopy was similar to pre-lens wear.ConclusionsAcross the 6-years, there were no contact lens related serious AEs and biomicroscopy showed no significant changes. Results suggest that children this age can successfully wear daily-disposable hydrogel contact lenses with minimal impact on ocular physiology.     

Randomized crossover trial of silicone hydrogel contact lenses

PurposeThe aim of the current study is to assess, using new technologies, the interaction of four monthly silicone hydrogel contact lenses on the ocular surface and the comfort over 15 days of use.MethodsProspective cross-over, randomized and double-masked study including four materials (lotrafilcon-B, samfilcon-A , comfilcon-A and filcom-V3). Clinical examination was performed in the following order: tear meniscus height, first break-up of the tear film, the average time of all tear film breakup incidents, bulbar redness, limbal redness (Keratograph 5M ,Oculus, Germany); central corneal thickness (Pentacam, Oculus, Germany), thermography values (FLIR A325; FLIR Systems Inc., USA), and slit-lamp evaluations, including ocular surface staining. Finally, subjective comfort was obtained from Contact Lens Dry Eye Questionnaire-8.ResultsThe impact of contact lens wear on the ocular surface didn’t show statistically significant changes over time except for corneal and conjunctival staining grades on day 15 compared to day 1 for the comfilcon A group (P = .003 and P = .01, respectively). Contact lens stability and impact on the ocular surface during contact lens wear didn’t show statistically significant changes over time except in the case of the comfilcon A material with respect to the irritation item (P = .01).ConclusionsThese results suggest that the impact of monthly silicone hydrogel contact lens materials on the ocular surface after and during contact lens wear, contact lens stability over time, and subjective comfort did not reveal any significant changes over 15 days of use for any of the materials.     

Visual function,ocular surface integrity and symptomatology of a new extended depth-of-focus and a conventional multifocal contact lens

PurposeTo evaluate visual function, ocular surface integrity and dry eye symptoms with an extended depth-of-focus (EDOF) design and a conventional multifocal (MF) contact lens (CL) after 15 days of wear.MethodsA crossover single mask randomised clinical trial was conducted including 30 presbyopes who used an EDOF and a conventional MF CL (Biofinity MF) for 15 days each. Defocus curves, depth-of-focus range, contrast sensitivity (CS) under photopic and mesopic conditions (with and without glare) and subjective perception of halos and glare were evaluated. The ocular surface was evaluated through non-invasive Keratograph tear breakup time (NIKBUT), averaged tear breakup time (NIKBUT-avg), tear meniscus height (TMH), bulbar and limbal redness, and conjunctival and corneal staining. Dry eye symptoms were assessed with the OSDI questionnaire.ResultsNo statistically significant differences were found for defocus curves or depth-of-focus between the two CLs (both p > 0.05). Subjective perception of halos and glare was not significantly different between CLs. Statistically significant differences were observed for CS under mesopic conditions for low spatial frequencies (p = 0.008). None of the CL produced significant changes in NIKBUT, NIKBUT-avg, TMH or redness. No change in conjunctival staining was observed in 76.7 % and 73.3 % of participants for EDOF and Biofinity MF, respectively. No change in corneal staining was observed in 86.7 % and 83.3 % of participants for EDOF and Biofinity MF, respectively. No changes were observed in the symptomatology measured with OSDI questionnaire (p > 0.05).ConclusionsBoth CL for presbyopia offer good visual quality, preserve the ocular surface integrity and provide the patient with similar symptomatology levels after 15 days of lens wear.     

The management of allergic eye diseases in primary eye care

Allergy is an over-reaction of the body's immune system to innocuous foreign substances or allergens that the body perceives as a potential threat or undesirable. It is estimated to affect approximately 20% of the population. Of this subset at least 20% suffer from ocular allergy. It has a significant impact on the quality of life of the individual. Allergic diseases are those conditions in which an antibody- and/or T-cell mediated mechanisms are involved.Allergic eye diseases are characterized by IgE-mast cell mediated, as seen in allergic conjunctivitis; chronic mast cell activation and eosinophil/T-lymphocyte-mediated response, as seen in giant papillary conjunctivitis, vernal keratoconjunctivitis and atopic keratoconjunctivitis; or a T-lymphocyte-mediated response in contact ocular allergy.The management of allergic eye disease is aimed at preventing the release of mediators of allergy, controlling the allergic inflammatory cascade and preventing ocular surface damage secondary to the allergic response. In the management of ocular allergic disease, the clinician is advised to recommend non-pharmacologic and pharmacologic therapeutic regimens that address the acute presentation of ocular allergy and provide prophylaxis aimed at providing long-term maintenance therapy. This approach to the management of allergic eye diseases aims to minimize the impact of the allergic reaction on the individual's quality of life.To achieve success in the management of allergic eye diseases, the clinician requires a considerable understanding of the pathophysiology, clinical features and differential diagnosis of the different types of ocular allergy, as well as an adequate knowledge of their pharmacotherapy.     

Corneal epithelial bullae after short-term wear of small diameter scleral lenses

Complications of scleral lens wear are not well documented or understood. While multiple studies focus on oxygen transmission during scleral lens wear and associated corneal swelling, little is known about the effects of varying scleral lens fitting relationships, especially when there is corneal interaction. Scleral lenses, by convention, are designed to completely clear the corneal surface and rest on the conjunctival and scleral tissue. However, some designs maximize oxygen transmission by reducing the lens diameter, thickness, and recommended corneal clearance.While the modifications increase oxygen transmission in any scleral lens design, they also distribute the lens mass closer to the limbus and make visualization of corneal clearance, especially narrow in the limbal region, more difficult. The sequelae from mechanical interaction between scleral lenses and the ocular surface, in particular the cornea, remain uncertain.This case series will describe corneal epithelial bullae, molding, and epithelial erosions as unintended scleral lens complications. These corneal changes corresponded to areas of contact lens-corneal bearing confirmed utilizing a combined scanning laser ophthalmoscopy (SLO) and anterior segment OCT. This case series will discuss epithelial bullae detection, their etiology, and suggestions for application of this information into scleral lens fitting protocols.     

Short-term tolerability of commercial eyelid cleansers: A randomised crossover study

PurposeTo evaluate the short-term tolerability of five commercially available anti-demodectic eyelid cleansers; OCuSOFT Oust Demodex (OD), I-MED I-Lid’n Lash Plus (ILL+), Labtician BlephaDex (BD), Chrissanthe Eye Cleanse (EC), and Théa Blephademodex (BDdx).MethodsThirty healthy non-contact lens wearers (18 female; mean ± SD age, 33 ± 12 years) were enrolled in a prospective randomised crossover study. On separate visits, spaced at least 48 h apart, participants were randomised to receive topical application of one of five eyelid cleansers or saline. Participants rated subjective ocular discomfort during the 10-minute post-application period. Visual acuity, non-invasive tear film stability, conjunctival hyperaemia, and ocular surface staining were assessed at baseline and 10 min.ResultsNo inter-group differences in ocular parameters were noted at baseline (all p > 0.05). Ocular discomfort scores significantly exceeded baseline scores for 60 s following BD application, 120 s with OD, 135 s with BDdx, 150 s with ILL+, and 195 s with EC (all p < 0.05). Deterioration in non-invasive tear film stability, limbal conjunctival hyperaemia, as well as corneal, conjunctival, and lid margin staining was detected following EC application (all p < 0.05), and increased bulbar conjunctival hyperaemia was observed following both EC and ILL+ treatment (both p < 0.05).ConclusionsStudy outcomes highlight varying tolerability profiles with different anti-demodectic lid cleanser preparations, and the potential to induce tear film instability, conjunctival hyperaemia and ocular surface staining on application. Awareness of possible adverse effects arising from topical application of commercial anti-demodectic lid cleanser formulations may help clinicians set realistic patient expectations and encourage better compliance in their use of lid hygiene therapies.     

甘蓝型油菜对干旱和低磷双重胁迫的生理反应Ⅰ：叶片气体交换参数及产量

通过对气体交换参数及产量的测定和分析,研究了干旱和低磷双重胁迫对油菜不同生育期叶片光合特性的影响。结果表明：油菜在不同生育期受到干旱和低磷胁迫后,叶片净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）会明显降低。在干旱和低磷双重胁迫下,苗期油菜Ci降低、Ls升高,表明气孔限制是导致Pn降低的主要原因;而蕾薹期和花期Ci升高、Ls降低,表明非气孔限制是导致Pn降低的主要原因。对单一的胁迫而言,低磷胁迫对油菜叶片Pn影响最大的时期是蕾薹期,而干旱胁迫对油菜叶片Pn影响最大的时期则是花期;与对照相比,它们均显著降低了油菜的株高、每角粒数、单株有效角果数和单株产量。     

The ability of the Contact Lens Dry Eye Questionnaire (CLDEQ)-8 to detect ocular surface alterations in contact lens wearers

PurposeTo study whether some ocular surface alterations could be associated with contact lens (CL) wearers suffering from CL discomfort (CLD) detected using the Contact Lens Dry Eye Questionnaire (CLDEQ)-8.MethodsForty-one soft CL wearers further classified into symptomatic CL wearers (SCLW) and asymptomatic CL wearers (ACLW) by the CLDEQ-8, and 20 non CL wearers (NCLW) were included. Tear osmolarity, slit-lamp biomicroscopy findings, tear film break-up time, corneal and conjunctival staining, and Schirmer test were performed 24 h after CL removal. Data were compared among groups using the analysis of variance and the Student t-test or the Kruskal-Wallis H and the Mann-Whitney U tests, applying the Bonferroni correction. Correlations between the CLDEQ-8 and the clinical signs were performed using the Spearman correlation coefficient.ResultsTwenty-four SCLW, 17 ACLW and 20 NCLW were recruited. There were significant differences among groups for tear osmolarity (p < 0.001), limbal hyperaemia (p = 0.014), and tarsal hyperaemia (p = 0.031). Pairwise comparisons revealed that SCLW and ACLW had higher tear osmolarity (p < 0.003, both comparisons) and limbal hyperaemia (p = 0.027 and p = 0.048, respectively) than NCLW. Moreover, SCLW had higher tarsal hyperaemia (p = 0.030) than NCLW. No significant correlations were found (p > 0.05).ConclusionThe CLDEQ-8 was ineffective to detect clinical alterations between SCLW and ACLW; therefore, the use of questionnaires alone remains being the best approach to detect CLD. The role of the tarsal conjunctiva in the development of CLD should be analyzed in future studies.     

Culture systems for pluripotent stem cells

Pluripotent stem cells have the capacity to self renew and to differentiate to cells of the three somatic germ layers that comprise an organism. Embryonic stem cells are the most studied pluripotent stem cells. Pluripotent stem cells have also been derived from adult tissues. Both embryonic and adult stem cells represent valuable sources of cells for applications in cell therapy, drug screening and tissue engineering. While expanding stem cells in culture, it is critical to maintain their self-renewal and differentiation capacity. In generating particular cell types for specific applications, it is important to direct their differentiation to the desired lineage. Challenges in expansion of undifferentiated stem cells for clinical applications include the removal of feeder layers and non-defined components in the culture medium. Our limited basic knowledge on the requirements for maintaining pluripotency of adult pluripotent stem cells and the lack of appropriate markers associated with pluripotency hinders the progress toward their wide spread application. In vitro differentiation of stem cells usually produces a mixed population of different cell lineages with the desired cell type present only at a small proportion. Use of growth factors that promote differentiation, expansion or survival of specific cell types is key in controlling the differentiation towards specific cell lineages. A variety of bioreactors for cell cultivation exist and can be readily adapted for stem cell cultivation and differentiation. They provide a well-controlled environment for studying the process of stem cell propagation and differentiation. Their wide use will facilitate the development of processes for stem cell application.     

Conjunctival prolapse during open eye scleral lens wear

PurposeTo investigate the incidence and peak elevation of conjunctival prolapse during short-term open eye scleral lens wear and its association with lens fitting characteristics.MethodsTen young, healthy adults (mean age ± SD, 30 ± 4 years) wore a high Dk sealed scleral lens for 90 min with an initial central post-lens fluid reservoir thickness defined as low (144 ± 23 μm), medium (487 ± 63 μm), and high (726 ± 55 μm). Optical coherence tomography was used to quantify limbal clearance, lens settling, and changes in conjunctival thickness.ResultsThe incidence of conjunctival prolapse was 37% across all fluid reservoir thickness conditions, with 80% of participants exhibiting conjunctival prolapse at least once. Prolapse was observed more frequently nasally (73%) than temporally (27%) (p < 0.01). The peak prolapse elevation did not vary with fluid reservoir thickness condition or anatomical location (both p > 0.05). For the low fluid reservoir thickness condition, eyes with conjunctival prolapse had greater initial limbal clearance (97 ± 38 μm compared to 43 ± 34 μm, p = 0.01) and more settling after 90 min of lens wear (−85 ± 30 μm compared to −34 ± 29 μm, p < 0.01). Greater limbal settling was associated with a higher peak elevation of the conjunctival prolapse (r = 0.48, p = 0.02), but not with landing zone tissue compression (r = 0.22, p = 0.33) or the initial or final limbal fluid reservoir thickness asymmetry (r ≤ 0.07, p > 0.05).ConclusionConjunctival prolapse was commonly observed during short-term sealed scleral lens wear in healthy eyes. The peak elevation of the conjunctival prolapse was associated with the extent of limbal settling, but not landing zone tissue compression or fluid reservoir thickness asymmetry.     

ANALYSIS OF CONJUNCTIVAL VASCULAR DENSITY IN SCLERAL CONTACT LENS WEARERS USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PurposeTo investigate conjunctival vascular density (VD) using Anterior Segment Optical Coherence Tomography Angiography (OCTA) in Scleral Contact Lens (ScCL) wearers.MethodsIn this cross-sectional study, the conjunctival blood VD was assessed using OCTA with an anterior segment lens adapter. The nasal surface of each eye (6 ×6 mm) was scanned to a depth of 800 μm with ScCL and fifteen minutes after removing the lens. Conjunctival VD was defined as the percentage of the scanned volume occupied by vessels in which blood flow was measured. Measures of limbal indentation were subjectively determined by two independent observers using Anterior Segment Optical Coherence Tomography (AS-OCT). Comparisons between VD measurements before and after ScCL removal and correlations between conjunctival VD, time of use, vault and indentation values were also investigated.ResultsA total of 23 patients (3 females, 20 males) with keratoconus, with a mean age (years±SD) of 38.74±10.38 were included in the study. VD was significantly higher without ScCL (71.75%±2.97) than VD measured with ScCL (69.81%±2.63), p=0.02. A moderately negative correlation was found between indentation and vault (r=-0.44, p<0.05) and a positive tendency regarding the time of wearing ScCL and indentation (r=0.11 and r=0.068, respectively).ConclusionsUsing OCTA with an anterior segment lens adapter, the ocular surface blood VD was imaged and assessed with good repeatability and reliability. This study presents a new possible application of OCTA to investigate and monitor conjunctival vasculature in ScCL wearers. This results cautiously suggest that the repeated use of ScCL can cause vascular alterations in conjunctiva of the eyes of ScCL wearers, possibly due to a hidden hypoxia caused by prolonged limbal indentation.     

Multicenter review of impression-based scleral devices

ObjectiveTo describe outcomes using impression based-scleral devices for the management of anterior segment disease.MethodsRetrospective chart review identified all patients who were fitted with impression-based scleral devices between January 1, 2013 and June 30, 2019 at three specialty contact lens practices. Patient demographic data, indication for device use, visual and physiological outcomes, as well as details of the fitting process and survival of device use were determined.ResultsForty-four patients (70 eyes) were included in the study. Primary indications for device use included corneal irregularity (28 patients, 44 eyes) and ocular surface disease (16 patients, 26 eyes). Fifty-four percent of patients had more than one ocular surface condition, and 39 % of patients had undergone at least one anterior segment surgical procedure. Twenty-nine patients had unsuccessfully attempted to wear standard scleral lenses prior to being fit with impression-based devices. Visual acuity improved significantly with impression-based devices compared to habitual correction (p < 0.001). Completion of the fitting process (including visit to acquire the impression and post-fitting assessments) required an average of 4 [1.5] visits.Ideal haptic alignment was achieved with 74 % and complete limbal clearance was achieved in 83 % of fits. Device use was discontinued due to complications in two eyes.ConclusionPatients with complex eye disease who are unable to successfully wear standard scleral lenses successfully may achieve visual and therapeutic success with impression-based devices.     

Anterior chamber parameters in early and advanced keratoconus. A meridian by meridian analysis

Purpose

To explore anterior segment changes with keratoconus onset and progression to determine whether structural changes are predominantly corneal, limbal or both. To investigate these changes in different corneal meridians.

The cellular perspective on mammary gland development: stem/progenitor cells and beyond

Study of the mammary gland at the stem cell level is necessary for understanding mammary gland development. Knowledge of mammary gland development and growth is the first step toward formulating strategies to improve milk production. The success of these strategies requires an understanding of the dynamics of adult stem cells and their progeny in the development of the bovine mammary gland. The stem cell lineage pathway begins with adult stem cells and ends with the production of terminally differentiated cells. The progression of adult stem cells along the mammary gland stem cell lineage pathway requires the coordination of many events. One important event in this process is cell differentiation. This differentiation process evolves with a gradient appearance of cell organelles progressing from stem cells to terminally differentiated cells. To dissect differentiation, mechanisms that regulate stem cells to differentiate toward a particular cell fate must be identified. Ultrastructural characteristics assist in distinguishing cells in various stages of differentiation in the mammary gland cell lineage pathway. Cells in the lineage pathway can become either epithelial cells or myoepithelial cells. Epithelial cells function in the production and secretion of milk, whereas myoepithelial cells assist epithelial cells in milk secretion. This review focuses on current concepts regarding adult stem cells and the recent progress on bovine mammary gland stem/progenitor cell development and differentiation. Multistep strategies that incorporate manipulation of the mechanisms influencing lineage choices in the mammary gland will produce beneficial effects on mammary gland development and milk production.