A polyvinyl alcohol (PVA) hydrogel as a soft contact lens material

A transparent polyvinyl alcohol (PVA) hydrogel was prepared from a PVA solution in a mixed solvent consisting of water and a water miscible organic solvent by cooling. The physical properties were evaluated in comparison with commercially available soft contact lens materials, such as polyhydroxyethyl methacrylate (PHEMA) and copolymers of methyl methacrylate (MMA) and N-vinyl pyrrolidone (VP). The PVA hydrogel showed higher tensile strength and elongation at break than the other materials, while it had high water content and oxygen permeability the latter being comparable to those of PMMA/VP copolymers. The protein adsorption of the PVA hydrogel was much less than those of the other materials. The PVA hydrogel soft contact lenses were applied on rabbit eyes for 12 weeks. The influence on the cornea was studied by biomicroscopy, ultrasonic corneal pachymetry and histopathological examination. These examinations revealed no abnormal findings in the cornea. These results suggest that the PVA hydrogel may be promising as a new soft contact lens material.     

Now soft toric contact lenses; silicone hydrogel lens for astigmatism

Soft toric contact lenses are a good alternative for the optical correction of astigmatism. They provide a wide visual field, quick adaptation process, negligible aniseikonia, together with enhanced comfort and reduced incidence of complications introduced by the lenses for frequent replacement. Still practitioners do not recommend them proactively and the satisfaction obtained by the patients is not high enough. This paper presents two recent studies that investigate the opinions of specialists and contact lens wearers and introduce a new contact lens, with an original design, born after 30 years of domination of only 2 modalities of rotational stabilization: prism ballast and dual thin zones. The lens is manufactured using a silicon-hydrogel material of 2-nd generation that provides sustained comfort and better oxygenation.     

Comparison of effectiveness of silicone hydrogel contact lens and hydrogel contact lens in patients after LASEK

AIM: To conduct a comparative study of effectiveness of silicone hydrogel contact lens and hydrogel contact lens, which are used in patients after laser-assisted subepithelial keratomileusis (LASEK). METHODS: Sixty-three patients (121 eyes) with a spherical equivalent ≤-5.0 D were chosen after undergoing LASEK in 2012 at Guangdong General Hospital. They were randomly divided into 2 groups. The silicone hydrogel group included 32 cases (61 eyes) that wore silicone hydrogel contact lenses for 4-6d after the operation, while the hydrogel group included 31 cases (60 eyes) who wore hydrogel contact lenses for 4-6d after the operation. Patients’ self-reported postoperative symptoms (including pain, photophobia, tears, and foreign body sensation) were evaluated. The healing time of the corneal epithelium, the visual acuity of patients without contact lens after epithelial healing, and the incidence of delayed corneal epithelial shedding were also assessed. The follow-up time was 1mo. RESULTS: Postoperative symptoms were milder in the silicone hydrogel group than in the hydrogel group. There were significant differences in pain, foreign body sensation, and photophobia between the 2 groups (P<0.05), although there was no significant difference in postoperative tearing (P>0.05). The healing time of the corneal epithelium in the silicone hydrogel lens group was markedly shorter than that in the hydrogel group (4.07±0.25 vs 4.33±0.82d, t=2.43, P=0.02). Visual acuity without contact lenses after healing of the corneal epithelium was better in the silicone hydrogel group compared with the hydrogel group (χ2=7.76, P=0.02). There was no significant difference in the occurrence of delayed corneal epithelial shedding between the 2 groups (P>0.05). CONCLUSION: Patients with LASEK using silicon hydrogel contact lenses had less discomfort and shorter corneal epithelial healing time compared with those using hydrogel contact lenses, suggesting that silicon hydrogel contact lenses may be considered to be a better choice of bandage contact lens after LASEK.     

Compatibility of two new silicone hydrogel contact lenses with three soft contact lens multipurpose solutions*.

Purpose: The purpose of this study is to assess corneal staining and subjective symptom ratings with six different silicone hydrogel contact lens/multipurpose solution combinations, including the recently launched Menicon PremiO silicone hydrogel contact lens, after the first night of soaking the lenses in solution. Methods: This study is a prospective, single-centre, subject-masked, contralateral, crossover, daily wear clinical trial in which subjects were randomly fitted in the morning with a different lens/solution combination in each eye, asked to wear the lenses for the whole day (at least 12 h), soak each of the lenses overnight in one of the test solutions and insert the lenses on the following morning. Subjects were asked to come on that morning for assessment of corneal staining and subjective ratings. All subjects repeated this procedure on another two occasions in order to collect the results of the six different lens/solution combinations: Menicon PremiO/MeniCare Soft; Menicon PremiO/Complete 10; Menicon PremiO/OptiFree Express; Acuvue Oasys/MeniCare Soft; Acuvue Oasys/Complete 10; Acuvue Oasys/OptiFree Express. Results: Menicon PremiO lenses were associated with a lower level of corneal staining overall, and in the nasal and temporal locations, compared with Acuvue Oasys lenses (p < 0.05). No significant differences were found in corneal staining between solutions (p > 0.05). An overall rate of solution-induced corneal staining per eye of 12% was found. Symptoms were very similar among the six different lens/solution combinations (p > 0.05). Discussion: The lower level of corneal staining found with Menicon PremiO lenses compared with Acuvue Oasys lenses might be attributed to material, surface and design differences between lens types. The overall rate of solution-induced corneal staining and symptomatology found between the different lens/solutions combinations is consistent with previous studies.     

The influence of soft contact lens material on the corneoscleral profile

Purpose

To objectively quantify changes in corneoscleral profile, as evaluated by the limbus position and corneoscleral junction (CSJ) angle, as a consequence of wearing different soft contact lens (CL) materials.

Methods

Twenty-two healthy participants wore silicone hydrogel (SiHy, MyDay, CooperVision) and hydrogel (Hy, Biomedics 1 day extra, CooperVision) soft CLs for 8 h per lens in their left eye. In each session, corneoscleral topography was captured before and immediately after CL removal with an Eye Surface Profiler. Previously validated automatic and objective algorithms for limbal position and CSJ angle calculation were applied to 360 semi-meridians to investigate the effect of short-term CL wear on corneoscleral topography, globally and by sectors, depending on the soft CL material worn.

Results

Short-term soft CL wear significantly impacted limbal position (SiHy: 120 ± 97 μm, Hy: 128 ± 85 μm) and CSJ angle (SiHy: 0.57 ± 0.36°, Hy: 0.55 ± 0.40°); all p < 0.05. A statistically significant difference was found between the sectors with regard to limbus position and CSJ angle before CL wear that remained following lens wear (all pairwise comparisons, p < 0.001). Although individual differences were observed, there was no evidence that one material caused more substantial corneoscleral alterations.

Conclusion

Corneoscleral profile parameters were altered significantly following 8 h of soft CL wear. The observed changes in limbus position and CSJ angle support the importance of participant-material biocompatibility.     

Clinical evaluation of a custom toric hydrogel contact lens

Eleven astigmatic patients seen in a private practice were fit with the Hydron-T custom toric soft lens. The fitting mechanics are described along with the results which illustrate the potential utilization of this lens in the management of patients with high astigmatic errors.     

软性角膜接触镜诱发角膜改变的共焦显微镜观察

目的应用共焦显微镜对长期配戴软性角膜接触镜所诱发的活体角膜组织改变情况进行观察.方法选择2002年8月～2003年4月于天津医科大学眼科中心门诊进行检查的患者36例(72眼),其中男性19例(36眼),女性17例(34眼),平均年龄为(27.63±10.7)岁,平均等效球镜度为(-5.87±0.67)D(-1.0～-9.0D),平均日戴时间超过8h,平均戴镜时间为(5.60±3.38)年(1～13年).选择未戴角膜接触镜者41例(82眼)作为对照组,其中男性20例(40眼),女性21例(42眼).平均年龄为(28.54±12.4)岁(18～52岁),平均等效球镜度为(-5.94±4.06)D(-1.25～-13D).结果戴软性角膜接触镜组角膜上皮的厚度为(42.6±6.1)μm,前基质角膜细胞密度为(1243±116)个/μm2,与对照组比较存在差异,其差异有显著性.戴角膜接触镜组的内皮细胞密度与对照组之间无差异,多形性内皮细胞和内皮细胞异形性百分比与对照组之间存在差异,其差异有显著性.结论长期戴软性角膜接触镜可诱发角膜组织改变.     

Surface deposition and cracking of a tinted hydrogel contact lens

For some years, anecdotal reports have been made that certain tinted soft contact lenses accumulate more deposits than non-tinted lenses. Clinical observation and subsequent scanning electron microscopic examination of a blue tinted soft contact lens confirmed more marked surface deposition over the tinted zone of one lens. In addition, crazing of the surface film and cracking of the material surface were observed over the tinted area.     

Solving soft contact lens problems

Soft contact lens wearers encounter a variety of problems affecting their vision and comfort. Six patients with soft lens-related problems are discussed, illustrating the various sources of problems and approaches to their solution.     

Corneal vascularization in hydrogel contact lens wearers

Limbal injection, peripheral corneal edema, and adjacent leukocyte infiltration may all be involved in the neovascularization of corneal tissue. Hydrogel lenses should be made with a minimum average thickness an maximum water content to increase oxygen transmission to the cornea. Lenses should not compress the limbal area in order to decrease the risk of limbal injection and, therefore, possible leukocyte invasion. Following these guidelines will decrease the risk of corneal vascularization in the hydrogel contact lens wearer. Keeping these principles in mind will also help the practitioner evaluate corneal health in all patients.     

Contact lens material characteristics associated with hydrogel lens dehydration

Purpose: To determine the association between material dehydration and hydrogel contact lens material characteristics, including water content and ionicity. Methods: Water content and refractive index data were derived from automated refractometry measurements of worn hydrogel contact lenses of 318 participants in the Contact Lens and Dry Eye Study (CLADES). Dehydration was determined in two ways; as the difference between nominal and measured (1) water content and (2) refractive index. Multiple regression models were used to examine the relation between dehydration and material characteristics, controlling for tear osmolality. Results: The overall measured and nominal water content values were 52.58 ± 7.49% and 56.88 ± 7.81% respectively, while the measured and nominal refractive indices were 1.429 ± 0.015 and 1.410 ± 0.017. High water content and ionic hydrogel lens materials were associated with greater dehydration (p < 0.0001 for both) than low water content and non‐ionic materials. When dehydration was assessed as the difference in refractive index, only high water content was associated with dehydration (p < 0.0001). Conclusions: High water content and ionic characteristics of hydrogel lens materials are associated with hydrogel lens dehydration, with the former being more strongly associated. Such dehydration changes could in turn lead to important clinical ramifications such as reduced oxygen transmissibility, greater lens adherence and reduced tear exchange.     

Comamonas acidovorans keratitis in a hydrogel contact lens wearer.

PURPOSE: To present an unusual case of keratitis in a patient who wears hydrogel contact lenses that are replaced on a monthly basis. The agent isolated was Comamonas acidovorans, a species of Pseudomonas. METHODS AND RESULTS: A 40-year-old patient who wears hydrogel contact lenses that are replaced on a monthly basis presented with a red eye. The patient reported that the eye had been red for 2 days. A peripheral corneal stromal infiltrate was found and Comamonas acidovorans was isolated in culture. The patient was initially treated with high-dose gentamicin. After the results of cultures and sensitivity studies were obtained, she was given ciprofloxacin, leading to the remission of the case. CONCLUSIONS: Comamonas acidovorans should be considered as a possible agent of keratitis in hydrogel contact lens wearers-a culture and sensitivity studies may be indicated.     

Contact lens compliance amongst soft contact lens users

目的:从卫生和镜片、镜片盒及镜片护理液的更换来调查隐形眼镜配戴者的依从性.方法:以每天配戴镜片至少8h、持续配戴≥6mo的隐形眼镜配戴者为研究对象.采用半结构化、经过预先测试和验证的问卷调查表,在接受口头知情同意后评估软性隐形眼镜配戴者的依从性.每位受试者都接受访问,收集有关戴隐形眼镜使用历史的信息.年龄、性别、使用的镜片类型、配戴经验(a)、配戴时间和习惯、一天中持续使用镜片的时间和护理方法的细节都进行了记录.结果:共73名参与者的平均年龄为23.63±5.23y.观察到:依从性最高的项目为镜片清洁和消毒程序(98%);依从性最低的是隐形眼镜配件护理(81%).依从性较差的是:更换镜片盒(41%),检查并丢弃过期的护理液(22%)和未能进行后续随访(22%).镜片配戴的性别、配戴方式、配戴类型以及隐形眼镜使用年限依从性间无统计学差异.结论:这项研究结果证明总体上配戴者依从性良好.然而,在隐形眼镜盒和护理液等镜片配件的护理中,存在一定程度的不遵嘱执行.我们认为有必要考虑改善镜片护理操作依从性的方法.