Tear mixing under a soft contact lens: effects of lens diameter

McNamara, Nancy; Polse, Kenneth A.; Brand, Richard; Graham, Andrew D.; Chan, Judy S.; McKenney, Curtis D.

doi:10.1016/s0002-9394(99)00051-3

Cited by 137 publications

(96 citation statements)

References 9 publications

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“…Based on clinical and anecdotal feedback, consensus was reached on the ideal settling time being 20 minutes; the rating of discomfort on a 5 point scale, which has previously been shown to sufficiently differentiate between comfort states, without scale grades being redundant 1 ; white diffuse light evaluation of centration and coverage, with recording linked to issues that would affect clinical management such as crossing the limbus or the optic zone is encroaching across the pupil; and movement on blink which is critical to healthy ocular physiology. 19,21 Fluorescein assessment was concluded to be best evaluated with the GP lens centred, using lid manipulation if necessary, using a ± 2 grading system in the four principal meridians, Interestingly, simulated fluorescein patterns were subjectively graded as significantly less intense than actual photographs in each zone and this was confirmed objectively. In addition, the correlation between the objective quantification of the real and simulated fluorescein patterns was significant, but only just.…”

Section: Discussionmentioning

confidence: 99%

“…19 The tear layer between the contact lens and cornea also reduce the friction between the surfaces, avoiding significant mechanical interaction. While soft lenses with limited mobility have been shown to have a more negative impact on ocular physiology than well fitting soft lenses, 20 this is not well researched for GPs.…”

mentioning

confidence: 99%

“…While soft lenses with limited mobility have been shown to have a more negative impact on ocular physiology than well fitting soft lenses, 20 this is not well researched for GPs. This is probably because tear exchange beneath an GP is typically 15-16% compared to 1-2% for soft lenses, 19,21 although tear mixing with differing amounts of lens movement does not seem to have been examined.…”

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confidence: 99%

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Consensus on recording of gas permeable contact lens fit

Wolffsohn¹,

Worp²,

Brabander³

2013

Contact Lens and Anterior Eye

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Purpose:To develop a new schematic scheme for efficiently recording the key parameters of gas permeable contact lens (GP) fits based on current consensus. Methods:Over 100 established GP fitters and educators met to discuss the parameters proposed in educational material for evaluating GP fit and concluded on the key parameters that should be recorded. The accuracy and variability of evaluating the fluorescein pattern of GP fit was determined by having 35 experienced contact lens practitioners from across the world, grading 5 images of a range of fits and the topographer simulation of the same fits in random order using the proposed scheme. The accuracy of the grading was compared to objective image analysis of the fluorescein intensity of the same images. Results:The key information to record to adequately describe the fit of an GP was agreed as: the manufacturer, brand and lens parameters; settling time; comfort on a 5 point scale; centration; movement on blink on a ±2 scale; and the Primary Fluorescein Pattern in the central, mid-peripheral and edge regions of the lens averaged along the horizontal and vertical lens axes, on a ±2 scale. On average 50-60% of practitioners selected the median grade when subjectively rating fluorescein intensity and this was correlated to objective quantification (r=0.602,p <0.001). Objective grading suggesting horizontal median fluorescein intensity was generally symmetrical, as was the vertical meridian, but this was not the case for subjective grading. Simulated fluorescein patterns were subjectively and objectively graded as being less intense than real photographs (p<0.01).Conclusion: GP fit recording can be standardised and simplified to enhance GP practice.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Consensus on recording of gas permeable contact lens fit

Wolffsohn¹,

Worp²,

Brabander³

2013

Contact Lens and Anterior Eye

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“…Contact lenses are separated from the cornea by a thin fluid layer called post-lens tear film. The clearance time of the post-lens tear film in soft contact lenses is about 30 min (McNamara et al, 1999). Thus, ophthalmic drugs released from the contact lenses will have a residence time in front of the cornea for at least 30 min compared to 2 min for eye drops.…”

Section: Contact Lens Delivery Of Dinucleoside Polyphosphatesmentioning

confidence: 99%

The role of dinucleoside polyphosphates on the ocular surface and other eye structures

Carracedo

Crooke

Guzmán-Aránguez

et al. 2016

Progress in Retinal and Eye Research

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a b s t r a c tDinucleoside polyphosphates comprises a group of dinucleotides formed by two nucleosides linked by a variable number of phosphates, abbreviated NpnN (where n represents the number of phosphates). These compounds are naturally occurring substances present in tears, aqueous humour and in the retina. As the consequence of their presence, these dinucleotides contribute to many ocular physiological processes. On the ocular surface, dinucleoside polyphosphates can stimulate tear secretion, mucin release from goblet cells and they help epithelial wound healing by accelerating cell migration rate. These dinucleotides can also stimulate the presence of proteins known to protect the ocular surface against microorganisms, such as lysozyme and lactoferrin. One of the latest discoveries is the ability of some dinucleotides to facilitate the paracellular way on the cornea, therefore allowing the delivery of compounds, such as antiglaucomatous ones, more easily within the eye. The compound Ap 4 A has been described being abnormally elevated in patient's tears suffering of dry eye, Sjogren syndrome, congenital aniridia, or after refractive surgery, suggesting this molecule as biomarker for dry eye condition. At the intraocular level, some diadenosine polyphosphates are abnormally elevated in glaucoma patients, and this can be related to the stimulation of a P2Y 2 receptor that increases the chloride efflux and water movement in the ciliary epithelium. In the retina, the dinucleotide dCp 4 U, has been proven to be useful to help in the recovery of retinal detachments. Altogether, dinucleoside polyphosphates are a group of compounds which present relevant physiological actions but which also can perform promising therapeutic benefits.

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“…2,14,15,16 . While eye drops are comfortable to instill, the low bioavailability of less than 5% is a major drawback.…”

Section: Advantage Of Contact Lenses For Drug Deliverymentioning

confidence: 99%