727 resultados para Soft Contact-lenses


Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose. To compare visual function with the Bausch & Lomb PureVision multifocal contact lens to monovision with PureVision single vision contact lenses. Methods. Twenty presbyopic subjects were fitted with either the PureVision multifocal contact lens or monovision with PureVision singlevision lenses. Aftera 1-month trial, the following assessments of visual function were made: (a) distance, intermediate, and near visual acuity (VA); (b) reading ability; (c) distance and near contrast sensitivity function (CSF); (d) near range of clear vision; (e) stereoacuity; and (f) subjective evaluation of near vision ability with a standardized questionnaire. Subjects were then refitted with the alternative correction and the procedure was repeated. All measurements were compared between the two corrections, whereas the ``low addition'' multifocal lens was also compared with the ``high addition'' alternative. Results. Distance and near VA were significantly better with monovision than with the multifocal option (p < 0.05). Intermediate VA (p = 0.13) was similar with both corrections, whereas there was also no significant difference in distance and near CSF (p = 0.29 on both occasions). Reading speeds (p = 0.48) and the critical print size (p = 0.90) were not significantly different between the two contact lens corrections, but stereoacuity (p < 0.01) and the near range of clear vision (p < 0.05) were significantly better with the multifocal option than with monovision. Subjective assessment of near ability was similar for both types of contact lens (p = 0.52). The high addition multifocal lens produced significantly poorer distance and near CSF, near VA, and critical print size compared with the low addition alternative. Conclusions. Monovision performed better than a center-near aspheric simultaneous vision multifocal contact lens of the same material for distance and near VA only. The multifocal option provides better stereoacuity and near range of clear vision, with little differences in CSF, so a better balance of real-world visual function may be achieved due to minimal binocular disruption. (Optom Vis Sci 2009;86:98-105)

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The limbal vascular response to extended contact lens wear was examined in a group comparative study initially intended to last eighteen months. After six months all patients wearing contact lenses had presented with micro-epithelial cysts. This unanticipated occurrence of the micro-epithelial-cysts necessitated termination of the study, and limited the quantity of data collected. However, sufficient results were available to allow a limited description of •the vascular response to this form of contact lens wear. Interpretations of the date collected ore discussed in relation to suggested vasostimulating factors in the cornea. The micro-epithelial cysts observed after extended wear were classified and their rate of recovery recorded. A further clinical study was undertaken to observe cysts in both contact lens - and non contact lens-wearing eyes. Cysts were observed in every category of patient, although the characteristic patterns varied. These observations of micro-epithelial cysts are discussed with respect to the aetiopathogeneses of corneal epithelial cystic disorders. Subsequently, attempts were made to induce cysts in rabbit corneae by extended contact lens wear. Clinical observations revealed cyst-like appearances. Histological sections did not contain cysts but did exhibit signs characteristic •of cystic disorders of the corneal epithelium. In general, the results from the study indicate that extended wear is subjectively acceptable to contact lens wearers. However, the objective findings of significant vascular changes, micro-epithelial cysts and cases of acute red eye response cast considerable doubt on the recommendation of extended wear contact lenses for purely cosmetic applications.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

FULL TEXT: Like many people one of my favourite pastimes over the holiday season is to watch the great movies that are offered on the television channels and new releases in the movie theatres or catching up on those DVDs that you have been wanting to watch all year. Recently we had the new ‘Star Wars’ movie, ‘The Force Awakens’, which is reckoned to become the highest grossing movie of all time, and the latest offering from James Bond, ‘Spectre’ (which included, for the car aficionados amongst you, the gorgeous new Aston Martin DB10). It is always amusing to see how vision correction or eye injury is dealt with by movie makers. Spy movies and science fiction movies have a freehand to design aliens with multiples eyes on stalks or retina scanning door locks or goggles that can see through walls. Eye surgery is usually shown in some kind of day case simplified laser treatment that gives instant results, apart from the great scene in the original ‘Terminator’ movie where Arnold Schwarzenegger's android character encounters an injury to one eye and then proceeds to remove the humanoid covering to this mechanical eye over a bathroom sink. I suppose it is much more difficult to try and include contact lenses in such movies. Although you may recall the film ‘Charlie's Angels’, which did have a scene where one of the Angels wore a contact lens that had a retinal image imprinted on it so she could by-pass a retinal scan door lock and an Eddy Murphy spy movie ‘I-Spy’, where he wore contact lenses that had electronic gadgetry that allowed whatever he was looking at to be beamed back to someone else, a kind of remote video camera device. Maybe we aren’t quite there in terms of devices available but these things are probably not the behest of science fiction anymore as the technology does exist to put these things together. The technology to incorporate electronics into contact lenses is being developed and I am sure we will be reporting on it in the near future. In the meantime we can continue to enjoy the unrealistic scenes of eye swapping as in the film ‘Minority Report’ (with Tom Cruise). Much more closely to home, than in a galaxy far far away, in this issue you can find articles on topics much nearer to the closer future. More and more optometrists in the UK are becoming registered for therapeutic work as independent prescribers and the number is likely to rise in the near future. These practitioners will be interested in the review paper by Michael Doughty, who is a member of the CLAE editorial panel (soon to be renamed the Jedi Council!), on prescribing drugs as part of the management of chronic meibomian gland dysfunction. Contact lenses play an active role in myopia control and orthokeratology has been used not only to help provide refractive correction but also in the retardation of myopia. In this issue there are three articles related to this topic. Firstly, an excellent paper looking at the link between higher spherical equivalent refractive errors and the association with slower axial elongation. Secondly, a paper that discusses the effectiveness and safety of overnight orthokeratology with high-permeability lens material. Finally, a paper that looks at the stabilisation of early adult-onset myopia. Whilst we are always eager for new and exciting developments in contact lenses and related instrumentation in this issue of CLAE there is a demonstration of a novel and practical use of a smartphone to assisted anterior segment imaging and suggestions of this may be used in telemedicine. It is not hard to imagine someone taking an image remotely and transmitting that back to a central diagnostic centre with the relevant expertise housed in one place where the information can be interpreted and instruction given back to the remote site. Back to ‘Star Wars’ and you will recall in the film ‘The Phantom Menace’ when Qui-Gon Jinn first meets Anakin Skywalker on Tatooine he takes a sample of his blood and sends a scan of it back to Obi-Wan Kenobi to send for analysis and they find that the boy has the highest midichlorian count ever seen. On behalf of the CLAE Editorial board (or Jedi Council) and the BCLA Council (the Senate of the Republic) we wish for you a great 2016 and ‘may the contact lens force be with you’. Or let me put that another way ‘the CLAE Editorial Board and BCLA Council, on behalf of, a great 2016, we wish for you!’

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Premium intraocular lenses (IOLs) aim to surgically correct astigmatism and presbyopia following cataract extraction, optimising vision and eliminating the need for cataract surgery in later years. It is usual to fully correct astigmatism and to provide visual correction for distance and near when prescribing spectacles and contact lenses, however for correction with the lens implanted during cataract surgery, patients are required to purchase the premium IOLs and pay surgery fees outside the National Health Service in the UK. The benefit of using toric IOLs was thus demonstrated, both in standard visual tests and real-world situations. Orientation of toric IOLs during implantation is critical and the benefit of using conjunctival blood vessels for alignment was shown. The issue of centration of IOLs relative to the pupil was also investigated, showing changes with the amount of dilation and repeat dilation evaluation, which must be considered during surgery to optimize the visual performance of premium IOLs. Presbyopia is a global issue, of growing importance as life expectancy increases, with no real long-term cure. Despite enhanced lifestyles, changes in diet and improved medical care, presbyopia still presents in modern life as a significant visual impairment. The onset of presbyopia was found to vary with risk factors including alcohol consumption, smoking, UV exposure and even weight as well as age. A new technique to make measurement of accommodation more objective and robust was explored, although needs for further design modifications were identified. Due to dysphotopsia and lack of intermediate vision through most multifocal IOL designs, the development of a trifocal IOL was shown to minimize these aspects. The current thesis, therefore, emphasises the challenges of premium IOL surgery and need for refinement for optimum visual outcome in addition to outlining how premium IOLs may provide long-term and successful correction of astigmatism and presbyopia.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Approximately half of current contact lens wearers suffer from dryness and discomfort, particularly towards the end of the day. Contact lens practitioners have a number of dry eye tests available to help them to predict which of their patients may be at risk of contact lens drop out and advise them accordingly. This thesis set out to rationalize them to see if any are of more diagnostic significance than others. This doctorate has found: (1) The Keratograph, a device which permits an automated, examiner independent technique for measuring non invasive tear break up time (NITBUT) measured NITBUT consistently shorter than measurements recorded with the Tearscope. When measuring central corneal curvature the spherical equivalent power of the cornea was measured as being significantly flatter than with a validated automated keratometer. (2) Non-invasive and invasive tear break-up times significantly correlated to each other, but not the other tear metrics. Symptomology, assessed using the OSDI questionnaire, correlated more with those tests indicating possible damage to the ocular surface (including LWE, LIPCOF and conjunctival staining) than with tests of either tear volume or stability. Cluster analysis showed some statistically significant groups of patients with different sign and symptom profiles. The largest cluster demonstrated poor tear quality with both non-invasive and invasive tests, low tear volume and more symptoms. (3) Care should be taken in fitting patients new to contact lenses if they have a NITBUT less than 10s or an OSDI comfort rating greater than 4.2 as they are more likely to drop-out within the first 6 months. Cluster analysis was not found to be beneficial in predicting which patients will succeed with lenses and which will not. A combination of the OSDI questionnaire and a NITBUT measurement was most useful both in diagnosing dry eye and in predicting contact lens drop out.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

I was recently part of a small committee looking at higher qualifications in contact lens practice and the discussion turned to future technologies. There was mention of different materials and different applications of contact lenses. Drug delivery with contact lenses was discussed as this has been talked about in the literature for a while. The first paper I could find that talked about using contact lenses for drug delivery dates back over 40 years. There was a review paper in CLAE in 2008 that looked specifically at this too [1]. However, where are these products? Why are we not seeing them in the market place? Maybe the technology is not quite there yet, or maybe patents are prohibiting usage or maybe the market is not big enough to develop such products? We do have lenses on the market with slow release of lubricating agents but not therapeutic agents used for ocular or systemic conditions. Contact lenses with pathogen detectors may be part of our contact lens armoury of the future and again we can already see papers in the literature that have trialled this technology for glucose monitoring in diabetics or lactate concentration in the tear film. Future contact lenses may incorporate better optics based on aberration control and we see this starting to emerge with aspheric designs designed to minimise spherical aberration. Irregular corneas can be fitted with topography based designs and again this technology exists and is being used by some manufacturers in their designs already. Moreover, the topography based fitting of irregular corneas is certainly something we see a lot of today and CLAE has seen many articles related to this over the last decade or so. What about further into the future? Well one interesting area must the 3-dimensional contact lenses, or contact lenses with electronic devices built in that simulate a display screen. A little like the virtual display spectacles that are already sold by electronics companies. It does not take much of a stretch of the imagination to see a large electronic company taking this technology on and making it viable. Will we see people on the train watching movies on these electronic virtual reality contact lenses? I think we will, but when is harder to know.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose. We investigated structural differences in the fatty acid profiles of lipids extracted from ex vivo contact lenses by using gas chromatography mass spectrometry (GCMS). Two lens materials (balafilcon A or lotrafilcon A) were worn on a daily or continuous wear schedule for 30 and 7 days. Methods. Lipids from subject-worn lenses were extracted using 1:1 chloroform: methanol and transmethylated using 5% sulfuric acid in methanol. Fatty acid methyl esters (FAMEs) were collected using hexane and water, and analyzed by GCMS (Varian 3800 GC, Saturn 2000 MS). Results. The gas chromatograms of lens extracts that were worn on a continuous wear schedule showed two predominant peaks, C16:0 and C18:0, both of which are saturated fatty acids. This was the case for balafilcon A and lotrafilcon A lenses. However, the gas chromatograms of lens extracts that were worn on a daily wear schedule showed saturated (C16:0, C18:0) and unsaturated (C16:1 and C18:1) fatty acids. Conclusions. Unsaturated fatty acids are degraded during sleep in contact lenses. Degradation occurred independently of lens material or subject-to-subject variability in lipid deposition. The consequences of lipid degradation are the production of oxidative products, which may be linked to contact lens discomfort. © 2014 The Association for Research in Vision and Ophthalmology, Inc.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

PURPOSE. To report differences in the incidence of adverse events and discontinuations found in a group of neophyte contact wearers using two different silicone hydrogel contact lenses on a daily- and continuous-wear basis during an 18-month period. METHODS. Sixty-one subjects were initially examined, and 53 were eligible to participate in the study. Eligible subjects were randomly assigned to wear one of two silicone hydrogel materials: lotrafilcon A or balafilcon A lenses on a daily- or continuous-wear basis. After an initial screening, subjects were monitored weekly for the first month and then after 3, 6, 12, and 18 months. The incidence of adverse events, including corneal infiltrative events, superior epithelial arcuate lesions, and contact lens-induced papillary conjunctivitis, and discontinuations in each of the four contact lens groups were recorded. RESULTS. Twenty-two adverse events were found. A higher incidence of adverse events was found in subjects wearing lotrafilcon A lenses than in those wearing balafilcon A lenses (χ = 4.40, P=0.04). There were fewer adverse events in subjects wearing lenses on a daily-wear basis than in those wearing lenses on a continuous-wear basis (χ = 5.98, P=0.01). Eight subjects discontinued from the study as a result of recurrent corneal infiltrative events (one), vision problems (two), excessive ocular discomfort (one), relocation (one), noncompliance with the study protocol (one), and being lost to follow-up (two). No significant differences were found in the number of discontinuations between the two lens types (χ = 0.66, P=0.42) and wearing regimens (χ = 0.08, P=0.78). CONCLUSIONS. Lotrafilcon A lenses were associated with a higher incidence of adverse events than balafilcon A lenses were, and this difference is attributed to the difference in the incidence of corneal infiltrative events. Subjects wearing lenses on a daily-wear basis had fewer adverse events than did subjects wearing lenses on a continuous-wear basis. Both lens types and wearing regimens showed a similar incidence of discontinuations. © 2007 Lippincott Williams & Wilkins, Inc.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose. The purpose of this study was to evaluate the longitudinal changes in ocular physiology, tear film characteristics, and symptomatology experienced by neophyte silicone hydrogel (SiH) contact lens wearers in a daily-wear compared with a continuous-wear modality and with the different commercially available lenses over an 18-month period. Methods. Forty-five neophyte subjects were enrolled in the study and randomly assigned to wear one of two SiH materials: lotrafilcon A or balafilcon A lenses on either a daily- (LDW; BDW) or continuous-wear (LCW; BCW) basis. Additionally, a group of noncontact lens-wearing subjects (control group) was also recruited and followed over the same study period. Objective and subjective grading of ocular physiology were carried out together with tear meniscus height (TMH) and noninvasive tear breakup time (NITBUT). Subjects also subjectively rated symptoms and judgments with lens wear. After initial screening, subsequent measurements were taken after 1, 3, 6, 12, and 18 months. Results. Subjective and objective grading of ocular physiology revealed a small increase in bulbar, limbal, and palpebral hyperemia as well as corneal staining over time with both lens materials and regimes of wear (p < 0.05). No significant changes in NITBUT or TMH were found (p > 0.05). Subjective symptoms and judgment were not material- or modality-specific. Conclusions. Daily and continuous wear of SiH contact lenses induced small but statistically significant changes in ocular physiology and symptomatology. Clinical measures of tear film characteristics were unaffected by lens wear. Both materials and regimes of wear showed similar clinical performance. Long-term SiH contact lens wear is shown to be a successful option for patients. Copyright © 2006 American Academy of Optometry.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Background: Optometric practices offer contact lenses as cash sale items or as part of monthly payment plans. With the contact lens market becoming increasingly competitive, patients are opting to purchase lenses from supermarkets and Internet suppliers. Monthly payment plans are often implemented to improve loyalty. This study aimed to compare behavioural loyalty between monthly payment plan members and non-members. Methods: BBR Optometry Ltd offers a monthly payment plan (Eyelife™) to their contact lens wearers. A retrospective audit of 38 Eyelife™ members (mean. ±. SD: 42.7. ±. 15.0 years) and 30 non-members (mean. ±. SD: 40.8. ±. 16.7 years) was conducted. Revenue and profits generated, service uptake and product sales between the two groups were compared over a fixed period of 18 months. Results: Eyelife™ members generated significantly higher professional fee revenue ( P<. 0.001), £153.96 compared to £83.50, and profits ( P<. 0.001). Eyelife™ members had a higher uptake of eye examinations ( P<. 0.001). The 2 groups demonstrated no significant difference in spectacle sales by volume ( P= 0.790) or value ( P= 0.369). There were also no significant differences in contact lens revenue ( P= 0.337), although Eyelife™ members did receive a discount. The Eyelife™ group incurred higher contact lens costs ( P= 0.037), due to a greater volume of contact lens purchases, 986 units compared to 582. Conclusions: Monthly payment plans improve loyalty among contact lens wearers, particularly service uptake and volume of lens purchases. Additionally the greater professional fees generated, render monthly payment plans an attractive business model and practice builder.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose: To quantify the end-of-day silicone-hydrogel daily disposable contact lens fit and its influence of on ocular comfort, physiology and lens wettability. Methods: Thirty-nine subjects (22.1. ±. 3.5 years) were randomised to wear each of 3 silicone-hydrogel daily-disposable contact lenses (narafilcon A, delefilcon A and filcon II 3), bilaterally, for one week. Lens fit was assessed objectively using a digital video slit-lamp at 8, 12 and 16. h after lens insertion. Hyperaemia, non-invasive tear break-up time, tear meniscus height and comfort were also evaluated at these timepoints, while corneal and conjunctival staining were assessed on lens removal. Results: Lens fit assessments were not different between brands (P > 0.05), with the exception of the movement at blink where narafilcon A was more mobile. Overall, lag reduced but push-up speed increased from 8 to 12. h (P <. 0.05), but remained stable from 12 to 16. h (P > 0.05). Movement-on-blink was unaffected by wear-time (F = 0.403, P = 0.670). A more mobile lens fit with one brand did not indicate that person would have a more mobile fit with another brand (r = -0.06 to 0.63). Lens fit was not correlated with comfort, ocular physiology or lens wettability (P > 0.01). Conclusions: Among the lenses tested, objective lens fit changed between 8. h and 12. h of lens wear. The weak correlation in individual lens fit between brands indicates that fit is dependent on more than ocular shape. Consequently, substitution of a different lens brand with similar parameters will not necessarily provide comparable lens fit.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

Purpose: To assess the validity and repeatability of objective compared to subjective contact lens fit analysis. Methods: Thirty-five subjects (aged 22.0. ±. 3.0 years) wore two different soft contact lens designs. Four lens fit variables: centration, horizontal lag, post-blink movement in up-gaze and push-up recovery speed were assessed subjectively (four observers) and objectively from slit-lamp biomicroscopy captured images and video. The analysis was repeated a week later. Results: The average of the four experienced observers was compared to objective measures, but centration, movement on blink, lag and push-up recovery speed all varied significantly between them (p <. 0.001). Horizontal lens centration was on average close to central as assessed both objectively and subjectively (p > 0.05). The 95% confidence interval of subjective repeatability was better than objective assessment (±0.128. mm versus ±0.168. mm, p = 0.417), but utilised only 78% of the objective range. Vertical centration assessed objectively showed a slight inferior decentration (0.371. ±. 0.381. mm) with good inter- and intrasession repeatability (p > 0.05). Movement-on-blink was lower estimated subjectively than measured objectively (0.269. ±. 0.179. mm versus 0.352. ±. 0.355. mm; p = 0.035), but had better repeatability (±0.124. mm versus ±0.314. mm 95% confidence interval) unless correcting for the smaller range (47%). Horizontal lag was lower estimated subjectively (0.562. ±. 0.259. mm) than measured objectively (0.708. ±. 0.374. mm, p <. 0.001), had poorer repeatability (±0.132. mm versus ±0.089. mm 95% confidence interval) and had a smaller range (63%). Subjective categorisation of push-up speed of recovery showed reasonable differentiation relative to objective measurement (p <. 0.001). Conclusions: The objective image analysis allows an accurate, reliable and repeatable assessment of soft contact lens fit characteristics, being a useful tool for research and optimisation of lens fit in clinical practice.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The literature suggests that diabetic patients may have altered tear chemistry and tear secretion as well as structural and functional changes to the corneal epithelium, endothelium and nerves. These factors, together with a reported increased incidence of corneal infection, suggest that diabetic patients may be particularly susceptible to developing ocular complications during contact lens wear. Reports of contact lens-induced complications in diabetic patients do exist, although a number of these reports concern patients with advanced diabetic eye disease using lenses on an extended wear basis. Over the past decade or so, there have been published studies documenting the response of the diabetic eye to more modern contact lens modalities. The results of these studies suggest that contact lenses can be a viable mode of refractive correction for diabetic patients. Furthermore, new research suggests that the measurement of tear glucose concentration could, in future, be used to monitor metabolic control non-invasively in diabetic patients. This could be carried out using contact lenses manufactured from hydrogel polymers embedded with glucose-sensing agents or nanoscale digital electronic technology. The purpose of this paper is to review the literature on the anterior ocular manifestations of diabetes, particularly that pertaining to contact lens wear. © 2012 The Authors. Clinical and Experimental Optometry © 2012 Optometrists Association Australia.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

The poor retention and efficacy of instilled drops as a means of delivering drugs to the ophthalmic environment is well-recognised. The potential value of contact lenses as a means of ophthalmic drug delivery, and consequent improvement of pre-corneal retention is one obvious route to the development of a more effective ocular delivery system. Furthermore, the increasing availability and clinical use of daily disposable contact lenses provides the platform for the development of viable single-day use drug delivery devices based on existing materials and lenses. In order to provide a basis for the effective design of such devices, a systematic understanding of the factors affecting the interaction of individual drugs with the lens matrix is required. Because a large number of potential structural variables are involved, it is necessary to achieve some rationalisation of the parameters and physicochemical properties (such as molecular weight, charge, partition coefficients) that influence drug interactions. Ophthalmic dyes and structurally related compounds based on the same core structure were used to investigate these various factors and the way in which they can be used in concert to design effective release systems for structurally different drugs. Initial studies of passive diffusional release form a necessary precursor to the investigation of the features of the ocular environment that over-ride this simple behaviour. Commercially available contact lenses of differing structural classifications were used to study factors affecting the uptake of the surrogate actives and their release under 'passive' conditions. The interaction between active and lens material shows considerable and complex structure dependence, which is not simply related to equilibrium water content. The structure of the polymer matrix itself was found to have the dominant controlling influence on active uptake; hydrophobic interaction with the ophthalmic dye playing a major role. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Relevância:

90.00% 90.00%

Publicador:

Resumo:

This study identifies and investigates the potential use of in-eye trigger mechanisms to supplement the widely available information on release of ophthalmic drugs from contact lenses under passive release conditions. Ophthalmic dyes and surrogates have been successfully employed to investigate how these factors can be drawn together to make a successful system. The storage of a drug-containing lens in a pH lower than that of the ocular environment can be used to establish an equilibrium that favours retention of the drug in the lens prior to ocular insertion. Although release under passive conditions does not result in complete dye elution, the use of mechanical agitation techniques which mimic the eyelid blink action in conjunction with ocular tear chemistry promotes further release. In this way differentiation between passive and triggered in vitro release characteristics can be established. Investigation of the role of individual tear proteins revealed significant differences in their ability to alter the equilibrium between matrix-held and eluate-held dye or drug. These individual experiments were then investigated in vivo using ophthalmic dyes. Complete elution was found to be achievable in-eye; this demonstrated the importance of that fraction of the drug retained under passive conditions and the triggering effect of in-eye conditions on the release process. Understanding both the structure-property relationship between drug and material and in-eye trigger mechanisms, using ophthalmic dyes as a surrogate, provides the basis of knowledge necessary to design ocular drug delivery vehicles for in-eye release in a controllable manner.