We are being myopic about myopia control

Editorial

Wound healing studies and interfacial phenomena:use and relevance of the corneal model

The interaction of the wound dressing as a biomaterial with the wound bed is the central issue of this chapter. The interfacial phenomenon that encompasses the biological and biochemical consequences that arise when a biomaterial is introduced to a host biological environment is discussed. A great deal can be learned from observations arising from the behaviour of biomaterials at other body sites; one particularly relevant body site in the context of wound healing is the anterior eye. The cornea, tear film and posterior surface of the contact lens provide an informative model of the parallel interface that exists between the chronic wound bed, wound fluid and the dressing biomaterial. © 2011 Woodhead Publishing Limited All rights reserved.

Short- and long-term changes in corneal aberrations and axial length induced by orthokeratology in children are not correlated

PURPOSE: To assess the correlation between changes in corneal aberrations and the 2-year change in axial length in children fitted with orthokeratology (OK) contact lenses. METHODS: Thirty-one subjects 6 to 12 years of age and with myopia −0.75 to −4.00DS and astigmatism ≤1.00DC were fitted with OK. Measurements of axial length and corneal topography were taken at regular intervals over a 2-year period. Corneal topography at baseline and after 3 and 24 months of OK lens wear was used to derive higher-order corneal aberrations (HOA) that were correlated with OK-induced axial length changes at 2 years. RESULTS: Significant changes in C3, C4, C4, root mean square (RMS) secondary astigmatism and fourth and total HOA were found with both 3 and 24 months of OK lens wear in comparison with baseline (all P0.05). Coma angle of orientation changed significantly pre-OK in comparison with 3 and 24 months post-OK as well as secondary astigmatism angle of orientation pre-OK in comparison with 24 months post-OK (all P0.05). DISCUSSION: Short-term and long-term OK lens wear induces significant changes in corneal aberrations that are not significantly correlated with changes in axial elongation after 2-years.

Développement d’une lentille cornéenne médicamentée

L’utilisation de lentilles cornéennes peut servir à améliorer le profil d’administration d’un principe actif dans les yeux. Avec une efficacité d’administration de 5% par l’utilisation de gouttes, on comprend rapidement que l’administration oculaire doit être améliorée. Cette faible administration a donné naissance à plusieurs tentatives visant à fabriquer des lentilles cornéennes médicamentées. Cependant, à cause de multiples raisons, aucune de ces tentatives n’a actuellement été mise sur le marché. Nous proposons dans cette étude, une possible amélioration des systèmes établis par le développement d’une lentille cornéenne à base de 2-(hydroxyéthyle)méthacrylate (HEMA), dans laquelle des microgels, à base de poly N-isopropylacrylamide (pNIPAM) thermosensible encapsulant un principe actif, seront incorporé. Nous avons donc débuté par développer une méthode analytique sensible par HPCL-MS/MS capable de quantifier plusieurs molécules à la fois. La méthode résultante a été validée selon les différents critères de la FDA et l’ICH en démontrant des limites de quantifications et de détections suffisamment basses, autant dans des fluides simulés que dans les tissus d’yeux de lapins. La méthode a été validée pour sept médicaments ophtalmiques : Pilocarpine, lidocaïne, proparacaïne, atropine, acétonide de triamcinolone, timolol et prednisolone. Nous avons ensuite fait la synthèse des microgels chargés négativement à base de NIPAM et d’acide méthacrylique (MAA). Nous avons encapsulé une molécule modèle dans des particules ayant une taille entre 200 et 600 nm dépendant de la composition ainsi qu’un potentiel zêta variant en fonction de la température. L’encapsulation de la rhodamine 6G (R6G) dans les microgels a été possible jusqu’à un chargement (DL%) de 38%. L’utilisation des isothermes de Langmuir a permis de montrer que l’encapsulation était principalement le résultat d’interactions électrostatiques entre les MAA et la R6G. Des cinétiques de libérations ont été effectuées à partir d’hydrogels d’acrylamide chargés en microgels encapsulant la R6G. Il a été trouvé que la libération des hydrogels chargés en microgels s’effectuait majoritairement selon l’affinité au microgel et sur une période d’environ 4-24 heures. La libération à partir de ces systèmes a été comparée à des formules d’hydrogels contenant des liposomes ou des nanogels de chitosan. Ces trois derniers (liposomes, microgels et nanogels) ont présenté des résultats prometteurs pour différentes applications avec différents profils de libérations. Enfin, nous avons transposé le modèle développé avec les gels d’acrylamide pour fabriquer des lentilles de contact de 260 à 340 µm d’épaisseur à base de pHEMA contenant les microgels avec une molécule encapsulée devant être administrée dans les yeux. Nous avons modifié la composition de l’hydrogel en incorporant un polymère linéaire, la polyvinylpyrrolidone (PVP). L’obtention d’hydrogels partiellement interpénétrés améliore la rétention d’eau dans les lentilles cornéennes. L’encapsulation dans les microgels chargés négativement a donné de meilleurs rendements avec la lidocaïne et cette dernière a été libérée de la lentille de pHEMA en totalité en approximativement 2 heures qu’elle soit ou non encapsulée dans des microgels. Ainsi dans cette étude pilote, l’impact des microgels n’a pas pu être déterminé et, de ce fait, nécessitera des études approfondies sur la structure et les propriétés de la lentille qui a été développée. En utilisant des modèles de libération plus représentatifs de la physiologie de l’œil, nous pourrions conclure avec plus de certitude concernant l’efficacité d’un tel système d’administration et s’il est possible de l’optimiser.

Effect of overnight orthokeratology on conjunctival goblet cells

Objective: To evaluate the differences between goblet cell density (GCD) and symptomatology after one month of orthokeratology lens wear. Methods: A pilot, short-term study was conducted. Twenty-two subjects (29.7. ±. 7.0 years old) participated voluntarily in the study. Subjects were divided into two groups: habitual silicone hydrogel contact lens wearers (SiHCLW) and new contact lens wearers (NCLW). Schirmer test, tear break up time (TBUT), Ocular Surface Disease Index (OSDI) questionnaire and conjunctival impression cytology. GCD, mucin cloud height (MCH) and cell layer thickness (CLT) were measured. All measurements were performed before orthokeratology fitting and one month after fitting to assess the evolution of the changes throughout this time. Results: No differences in tear volume and TBUT between groups were found (p>0.05). However, the OSDI score was statistically better after one month of orthokeratology lens wear than the baseline for the SiHCLW group (p=0.03). Regarding the goblet cell analysis, no differences were found in CLT and MCH from the baseline visit to the one month visit for the SiHCLW compared with NCLW groups (p>0.05). At baseline, the GCD in the SiHCLW group were statistically lower than NCLW group (p<0.001). There was a significant increase in GCD after orthokeratology fitting from 121±140cell/mm2 to 254±130cell/mm2 (p<0.001) in the SiHCLW group. Conclusion: Orthokeratology improves the dry eye subject symptoms and GCD after one month of wearing in SiHCLW. These results suggest that orthokeratology could be considered a good alternative for silicone hydrogel contact lens discomfort and dryness. © 2016 British Contact Lens Association.

Changes in Diadenosine Polyphosphates during Alignment-Fit and Orthokeratology Rigid Gas Permeable

Purpose.: To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap4A) and diadenosine pentaphosphate (Ap5A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment. Methods.: Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap4A and Ap5A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated. Results.: Ap4A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period. Conclusions.: Daily wear of RGP lenses increased the levels of Ap4A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.

Clinical performance of three silicone hydrogel daily disposable lenses

Purpose: To determine the clinical performance of DAILIES TOTAL1 (DT1), Clariti 1Day (C1D), and 1-DAY ACUVUE TruEye (AVTE) silicone hydrogel daily disposable contact lenses (SiHy DDCLs).

Methods: Eligible participants, subdivided into asymptomatic and symptomatic groups, wore each SiHy DDCLs for three consecutive days. Each participant attended three visits (on day 1 at 0 hours; on days 1 and 3 after 8 hours of wear) per lens type. The order of lens wear was randomized, with at least 1 day washout between lenses. Lens-related performance was evaluated by assessing lens surface deposits, wettability, pre-lens noninvasive tear breakup time, lens movement, and centration; ocular response assessments included conjunctival redness, corneal staining, and conjunctival staining and indentation.

Results: Fifty-one asymptomatic and 53 symptomatic participants completed the study. For all visits, the mean noninvasive tear breakup time was about 1 second longer with DT1 than with C1D and AVTE (p < 0.01). Overall, the wettability of all three lenses was good; however, DT1 was graded marginally better than the other lenses (both p < 0.01). On day 3, eyes wearing AVTE had significantly more dehydration-induced corneal staining compared with DT1 (AVTE, 24%; DT1, 11%; p < 0.01). After 8 hours, conjunctival staining was different between lenses (greatest with C1D and least with DT1; all p < 0.01). Conjunctival indentation was more prevalent with the C1D lenses (n = 70) compared with DT1 (n = 1; p < 0.01) and AVTE (n = 11; p < 0.01). There were no differences between asymptomatic and symptomatic lens wearers for any of the clinical parameters (all p > 0.05).

Conclusions: Each of the three SiHy DDCLs performed well. Noninvasive tear breakup time was longest and wettability was greater with DT1. C1D had the most conjunctival staining conjunctival indentation. There was no difference between asymptomatic and symptomatic wearers with regard to ocular response and contact lens–related parameters. These results suggest that SiHy DDCLs may be an excellent contact lens modality for the symptomatic patient

Short-term and long-term changes in corneal power are not correlated with axial elongation of the eye induced by orthokeratology in children

PURPOSE: To assess the relationship between short-term and long-term changes in power at different corneal locations relative to the change in central corneal power and the 2-year change in axial elongation relative to baseline in children fitted with orthokeratology contact lenses (OK). METHODS: Thirty-one white European subjects 6 to 12 years of age and with myopia −0.75 to −4.00 DS and astigmatism ≤1.00 DC were fitted with OK. Differences in refractive power 3 and 24 months post-OK in comparison with baseline and relative to the change in central corneal power were determined from corneal topography data in eight different corneal regions (i.e., N[nasal]1, N2, T[temporal]1, T2, I[inferior]1, I2, S[superior]1, S2), and correlated with OK-induced axial length changes at two years relative to baseline. RESULTS: After 2 years of OK lens wear, axial length increased by 0.48±0.18 mm (P0.05). CONCLUSION: The reduction in central corneal power and relative increase in paracentral and pericentral power induced by OK over 2 years were not significantly correlated with concurrent changes in axial length of white European children.