Changes in myopia with low-Dk hydrogel and high-Dk silicone hydrogel extended wear.

PURPOSE: This study compared changes in myopia between wearers of high-oxygen permeability (Dk) silicone hydrogel lenses and low-Dk hydrogel lenses after 1 year of extended wear (EW). METHODS: Ninety-two adult subjects were randomly assigned to a lens type. Subjective refraction and autokeratometry were performed at baseline and at 6 and 12 months. RESULTS: After 6 months of EW, myopia (spherical equivalent) regressed by 0.18 +/- 0.33 D (p < 0.001) in the high-Dk silicone hydrogel group and progressed by -0.23 +/- 0.36 D (p < 0.001) in the low-Dk hydrogel group. There were no further changes after 12 months. Previous lens wear history, baseline refractive error, and age and gender did not have an impact on the change in myopia, and only 35% of the variation could be accounted for by changes in corneal curvature and lens type. CONCLUSION: Soft contact lens type significantly affects the direction of change in myopia during EW. We hypothesize that these changes are driven by pressure-related redistribution of corneal tissue in high-Dk silicone hydrogel lens wearers and by hypoxia-associated corneal thinning in low-Dk hydrogel wearers. More long-term studies are required to confirm whether the effects of high-Dk silicone hydrogel lens wear on myopia are permanent.     

Incidence of keratitis of varying severity among contact lens wearers

AIM: To determine the incidence of non-severe keratitis (NSK) and severe keratitis (SK) among wearers of current generation contact lenses. METHODS: A 12 month, prospective, hospital based epidemiological study was conducted by examining all contact lens wearers presenting with a corneal infiltrate/ulcer to a hospital centre in Manchester. A clinical severity matrix was used to differentiate between NSK and SK, based on the severity of signs and symptoms. The size of the hospital catchment population and the wearing modalities (daily wear (DW) or extended wear (EW)) and lens types being used were estimated from relevant demographic and market data. RESULTS: During the survey period, 80 and 38 patients presented with NSK and SK, respectively. The annual incidences (cases per 10,000 wearers) for each wearing modality and lens type were: DW rigid--NSK 5.7, SK 2.9; DW hydrogel daily disposable--NSK 9.1, SK 4.9; DW hydrogel (excluding daily disposable)--NSK 14.1, SK 6.4; DW silicone hydrogel--NSK 55.9, SK 0.0; EW rigid--NSK 0.0, SK 0.0; EW hydrogel--NSK 48.2, SK 96.4; EW silicone hydrogel--NSK 98.8, SK 19.8. The difference in SK between EW hydrogel and EW silicone hydrogel was significant (p = 0.04). CONCLUSIONS: A clinical severity matrix has considerable utility in assessing contact lens related keratitis. There is a significantly higher incidence of SK in wearers who sleep in contact lenses compared with those who only use lenses during the waking hours. Those who choose to sleep in lenses should be advised to wear silicone hydrogel lenses, which carry a five times decreased risk of SK for extended wear compared with hydrogel lenses.     

A 6-month follow-up of successful refits from daily disposable soft contact lenses to continuous wear of high-Dk silicone-hydrogel lenses

PURPOSE: To compare, in routine optometric practice, the outcome of keeping successful soft contact lens (SCL) wearers in their lenses to re-fitting them with continuous wear of silicone hydrogel (SiH) lenses. METHODS: Forty-nine successful daily disposable lens wearers were recruited; 19 continued to wear daily SCLs and 30 were refitted with high-Dk SiH lenses on a 30-day/night schedule. Patients were assessed at baseline, 3 and 6 months by slit lamp examination along with the Efron grading scales, and central corneal thickness (CCT) and the corneal endothelium were assessed by non-contact specular microscopy. RESULTS: No substantial changes in subjective vision, refraction, visual acuity or overall lens comfort occurred for those completing the study, although five SiH lens wearers did discontinue due to reduced comfort, eyelid problems or seasonal allergy. Contact lens induced peripheral ulcers (CLPU) were observed in three patients in the first 3 months in the SiH lens group and these were also discontinued. Over the 6 month period, a complete set of records was obtained for 16 in each group. For those completing the study, lens dryness scores were variable, but there was a slight improvement in favour of SiH lenses. Small, but statistically significant, reductions in corneal staining, bulbar hyperaemia, and limbal neovascularisation in favour of the SiH lenses were also evident but mainly because of further increases in the daily lens wearers. Contact lens induced papillary conjunctivitis (CLPC) and corneal endothelial polymegethism were mild to moderate and showed slight increases in the daily lens wearers at 6 months. CONCLUSIONS: The present studies confirm that the continuous wear of SiH lenses for up to 30 days can be considered as an alternative to daily disposable soft lens wear, but is not suitable for everyone.     

A comparative study of biweekly disposable contact lenses: silicone hydrogel versus hydrogel

Background: Our aim was to compare the clinical performance of a biweekly (second generation) silicone hydrogel lens and a biweekly hydrogel lens worn for daily wear modality. Methods: We used a double‐masked study, in which non‐presbyopic, asymptomatic and adapted soft lens wearers were recruited. Subjects wore a silicone hydrogel lens in one eye and a hydrogel lens in the other (lens types and eyes were randomly assigned) for one month. Lenses were replaced every two weeks. Contact lens fitting, pre‐lens tear film thinning time, vision, corneal integrity and lens deposits were assessed before and every fortnight after delivery of new lenses. A questionnaire was used to compare the subjective performance of the two lens types. Results: Thirty of the 33 subjects completed the study. There were no significant differences in lens fitting (centration and movement), pre‐lens tear film thinning time, vision or corneal integrity between the two lens types. Statistically, there was no significant difference in lens deposits between the two lens types but silicone hydrogel lenses tended to have more Grade 3 to 4 lipid deposits than hydrogel lenses. Subjects found no significant differences between the two lens types in terms of vision and comfort. Preference for silicone hydrogel lenses increased from 33 at the first after‐care visit to 50 per cent at the second after‐care visit. Conclusion: This short‐term study demonstrates that the performance of silicone hydrogel and hydrogel lenses is comparable but the former tends to build up more lipid deposits than the latter. We did not find better performance in terms of ocular integrity of silicone hydrogel lenses compared to the hydrogel lenses, probably because the subjects were adapted asymptomatic contact lens wearers before commencing the study. Contact lens wearers having hypoxia‐related problems are likely to benefit from using silicone hydrogel lenses, as these lenses provide at least three times more oxygen than conventional hydrogel lenses.     

Silicone hydrogel contact lenses and the ocular surface

For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.     

A market survey of contact lens practice in Hong Kong

Purpose : The aim of this survey was to evaluate the use of contact lenses, current prescribing habits of practitioners and the development of the contact lens market in Hong Kong. Methods : Questionnaires were sent to all registered contact lens practitioners in Hong Kong. This questionnaire sought information about their choices on prescribing contact lenses and lens care products and their opinions on continuing education and future trends of contact lens development. Results : A total of 286 responses (22 per cent) were returned. On average, the respondents reported that 36 per cent of their patients were contact lens wearers and most were myopes. The ratio of new fittings to refittings was 1:3. Of the contact lens wearers, 66 per cent were fitted with planned replacement lenses, mostly daily disposable lenses. Multipurpose solution was the most popular lens care regimen prescribed. Only 48 per cent of astigmatic patients were fitted with toric lenses and the use of overnight orthokeratology and silicone hydrogel lenses was limited. Single vision contact lenses with over‐spectacles and monovision contact lenses were the most popular management for presbyopes. Dryness was the major problem reported by contact lens wearers. Practitioners look forward to further development of custom‐made toric, multifocal and silicone hydrogel lenses. The major source of new contact lens information was communication with contact lens suppliers. Conclusion : Compared to previous reports, there was no significant change in the prescribing habits of practitioners. The major complaint of contact lens wearers is still ocular dryness. The contact lens market is driven by younger contact lens wearers, and planned replacement soft contact lenses together with multipurpose solutions dominate. The use of bifocal/multifocal lenses remained low and practitioners want low cost bifocal/multifocal contact lenses with better visual performance and toric lenses with a wider range in parameters. The use of overnight wear lenses such as silicone hydrogel and ortho‐k lenses is limited and 30 days continuous wear silicone hydrogel lenses are prescribed mainly for daily wear.     

Incidence and morbidity of hospital‐presenting corneal infiltrative events associated with contact lens wear

Aim : To determine the incidence and morbidity (visual loss) of hospital‐presenting corneal infiltrative events (CIEs) associated with the wearing of current generation contact lenses. Methods : All contact lens wearers presenting with any form of corneal infiltrate/ulcer to a hospital centre in Manchester, UK, were surveyed in this 12‐month, prospective, hospital‐based epidemiological study. A clinical severity matrix was used to quantify the overall severity of presenting signs and symptoms. The size of the hospital catchment population and the wearing modalities (daily wear [DW] or extended wear [EW]) and lens types used in that population were estimated from relevant demographic and market data to facilitate the calculation of incidence. We also attempted to ascertain, from their eye care practitioners, the visual acuity (VA) of patients suffering from CIEs prior to and at about six months following attendance at the hospital. Results : During the survey period, 118 patients presented with CIEs of varying severity. The annual incidence (cases per 10,000 wearers) for all wearing modalities and lens types is 21.3 (95 per cent confidence interval 17.8 to 25.5). The incidence of CIEs for each wearing modality and lens type is: DW rigid, 8.6 (3.9 to 18.7); DW hydrogel daily disposable, 14.0 (9.3 to 21.0); DW hydrogel (excluding daily disposable), 20.4 (15.9 to 26.2); DW silicone hydrogel, 55.9 (9.9 to 309.6); EW rigid, zero (0.0 to 1758.8); EW hydrogel, 144.6 (66.4 to 311.8) and EW silicone hydrogel, 118.6 (75.2 to 186.7). The risk of developing a CIE with EW lenses was 8.1 (5.3 to 12.5) times greater than that with DW lenses (p < 0.0001). Although there was no difference between EW hydrogel and EW silicone hydrogel lenses with respect to the risk of developing CIEs, the clinical severity of CIEs was greater with EW hydrogel lenses (p = 0.04). Results of VA for pre‐and post‐hospital attendance were obtained from 38 patients, none of whom lost more than one line of VA. For the study population, zero patients (95 per cent CI: 0 to 9.2 per cent) suffered a significant loss of VA as a result of developing a CIE. Conclusions : Overall, there is an eight times higher incidence of CIEs in wearers who sleep in contact lenses compared with wearers who use lenses only during the waking hours. For those who choose to routinely or intermittently sleep in soft contact lenses, silicone hydrogels are the lens of first choice because CIEs are less clinically severe with this lens type compared with hydrogel lenses. The rate of significant visual loss as a result of developing a CIE is low.     

The effect of nonpreserved care solutions on 12 months of daily and extended silicone hydrogel contact lens wear

PURPOSE: To determine the effects of nonpreserved care solutions on human corneal epithelium in long-term daily wear (DW) compared with overnight (extended) wear (EW) of hyper-oxygen-permeable silicone hydrogel contact lenses. METHODS: This was a prospective, randomized, double-masked, single-center, parallel treatment group clinical trial (NCT 00344643). One hundred twenty-one patients completed the 13 month study: (1) Lotrafilcon A (30 night EW, n = 29; DW, n = 32); (2) Galyfilcon A (DW, n = 20); and (3) Lotrafilcon B (6 night EW, n = 20; DW, n = 21). Irrigation chamber collection of corneal surface cells (OD) and confocal microscopy (OS) were performed at baseline, 1 week; and 1, 3, 6, 9, and 12 months of EW. The main outcome measures were: (1) Pseudomonas aeruginosa (PA) binding to exfoliated corneal surface cells; (2) central epithelial thickness (CET); and (3) epithelial surface cell exfoliation rate (desquamation). RESULTS: DW had no significant effect on CET; there was a decrease in CET with EW that recovered (adapted) over 1 year (Lotrafilcon B, P < 0.05). All lens wear (DW, EW) decreased desquamation with adaptive effects over 1 year (P < 0.001). There was no significant difference in PA binding between lenses or modality of wear. CONCLUSIONS: PA binding to corneal epithelial cells is a prerequisite for infection, and no binding indicates no lens-enhanced risk of infection. In contrast to prior studies of preserved lens-care products, the absence of a change in the PA binding data results predict that the risk for PA CTL-keratitis should be similar for daily and extended silicone hydrogel lens wear over 1 year when preservative-free care solutions are used.     

Oedematous corneal response of the fellow control eye to lotrafilcon a and vifilcon a hydrogel contact lenses in the rabbit

PURPOSE: To compare central corneal swelling after 24 h in eyes wearing Lotrafilcon A (high Dk silicone hydrogel) and Vifilcon A (low Dk hydrogel) lenses and the fellow control eyes of rabbits. METHODS: 24 New Zealand albino rabbits, free of corneal and conjunctival disease, were anaesthetised with ketamine and xylazin. In 12 rabbits, the right eye was fit with the high Dk Lotrafilcon A silicone hydrogel lens. In the other 12 rabbits, the right eye was fit with the low Dk Vifilcon A hydrogel lens, whereas the left eyes were kept as control eyes. Thereafter, the lens-fitted eyes had partial tarsorrhaphy that left a central gap of approximately 4 mm in length. After 24 h the eyelids were opened and the lenses removed. Central corneal thickness was measured using an ultrasonic pachymeter (Mentor O&O-Advent). RESULTS: Central corneal oedema induced by Vifilcon A lens was significantly higher than that with the Lotrafilcon A lens (p < 0.0001). The oedema of the fellow eyes paired with the Vifilcon A lens-wearing eyes was also higher than that of the fellow eyes paired with the Lotrafilcon A lens-wearing eyes (p < 0.01). CONCLUSIONS: The Lotrafilcon A lens induced significantly less corneal oedema than the Vifilcon A lens. Corneal oedema of the fellow eyes appears to be influenced by the swelling of the contralateral lens-wearing eyes. The oedema of the fellow control eye was significantly lower when there was less oedema in the contralateral eye wearing a high Dk silicone hydrogel lens. This may be a sympathetic physiological response. The presence of silicone in the high Dk hydrogel lens may suppress corneal oedema in the lens-wearing eye, thus affecting the fellow eye.     

The comparative clinical performance of a new polyhexamethylene biguanide- vs a polyquad-based contact lens care regime with two silicone hydrogel contact lenses

PURPOSE: To compare the clinical performance of a new polyhexamethylene-biguanide (PHMB)- vs a polyquad-based contact lens care regime with two silicone hydrogel contact lenses. METHODS: This study was a randomised, controlled and investigator-masked (to the lens regimen) clinical study where the clinical performance of two multipurpose contact lens solutions was compared at a single site. Forty-one existing contact lens wearers were recruited and fitted randomly with either galyfilcon A or lotrafilcon A contact lenses. Subjects wore the same lens type for a period of 2 months but used a different care regime (PHMB- and polyquad-based) in a crossover manner, each for a period of 1 month. The primary outcome measure was the difference in corneal staining. Corneal staining was graded in five different locations: central, superior, inferior, temporal and nasal. Measurements of conjunctival redness, limbal redness, conjunctival staining and papillary conjunctivitis were also carried out throughout the study. Biomicroscopic measures were graded using the Efron grading scales. A variety of symptoms were also measured using a visual analogue scale. RESULTS: There was no statistically significant difference in overall corneal staining between lens types (p = 0.16) or care regimens (p = 0.60). Central corneal staining was significantly greater for the polyquad-based care regimen when compared with the PHMB-based care regimen (p = 0.04). Lotrafilcon A lenses showed greater superior corneal staining (p = 0.0004) and papillary conjunctivitis (p = 0.02), and lower comfort on insertion (p = 0.03) when compared with galyfilcon A lenses regardless of the care regime used. There were no statistically significant differences in the other biomicrosopic signs and symptoms between the lens types and the care regimes. CONCLUSIONS: Both care regimes performed in a similar clinical manner and are valid for use with the two silicone hydrogel contact lenses used in this study.     

Preoperative screening of contact lens wearers before refractive surgery.

PURPOSE: To evaluate corneal stability, measured by computerized videokeratography (CVK) after discontinuation of contact lens wear in preoperative refractive surgery candidates. SETTING: Baylor College of Medicine, Cullen Eye Institute, Houston, Texas, USA. METHODS: Topographic differences were analyzed in 136 noncontact lens wearers (NCLW) and 76 contact lens wearers (CLW) (18 rigid gas-permeable contact lenses [RGPCL], 58 soft contact lenses [SCL]) using EyeSys CVK after discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks. RESULTS: There were no differences in CVK patterns between the NCLW and the CLW groups. There were no statistically significant differences between the 2 groups in topographic symmetry, asphericity, corneal uniformity index, predicted corneal acuity, and irregular astigmatism. The dioptric range for the axial and the profile difference maps in the CLW group was slightly lower than in the NCLW group. CONCLUSIONS: For patients whose manifest refraction and CVK maps were within 0.5 diopters of earlier values, discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks was adequate for the cornea to return to its baseline topographic state.     

Changes in myopic refractive error with nine months' extended wear of hydrogel lenses with high and low oxygen permeability.

BACKGROUND: A small but significant increase in myopia after extended wear of low oxygen permeability (Dk) hydrogel lenses has been previously reported; however, the specific impact of hypoxia on refractive status and corneal curvature with extended wear are not well documented. The purpose of this study was to compare the refractive changes induced over a period of 9 months' extended wear with high-Dk fluorosiloxane hydrogel lenses and low-Dk hydrogel lenses. METHODS: Adapted daily wear contact lens wearers were randomly assigned to one of two groups. The low-Dk group wore etafilcon A (Dk = 28) for up to 7 days and 6 nights and the high-Dk group wore lotrafilcon A (Dk = 140) for up to 30 days and nights. Refractive error and corneal curvature were measured at 3-month intervals over 9 months of extended wear. RESULTS: The etafilcon A group demonstrated an average increase in myopia of 0.30 D over the 9-month period; however, no change in spherical myopic correction was measured in the lotrafilcon A group. The cylindrical component did not change in either group. A stratified analysis revealed a greater increase in myopia for low myopes than moderate myopes in the etafilcon A group but no difference in the lotrafilcon A group. Keratometric analysis revealed no change in the etafilcon A group and a small degree of central corneal flattening in both major meridians of 0.35 D in the lotrafilcon A group. CONCLUSIONS: Nine months of extended wear of low-Dk lenses is associated with a small degree of myopic progression in adult myopes that appears to be reversible. Wearing fluorosiloxane-hydrogel lenses of high-Dk had no impact on refractive error and may be associated with a small degree of central corneal flattening.     

The characteristics of corneal staining in successful daily and extended disposable contact lens wearers

Purpose : The aim of this investigation was to measure levels of corneal staining in successful daily and extended wearers of disposable hydrogel contact lenses. Methods : Twenty-four subjects on a daily wear (DW) schedule and 20 subjects on an extended wear (EW) schedule were examined at six-monthly intervals over a two-year period. Subjects wore two types of disposable hydrogel lenses. Measurements were taken from the eye wearing an etafilcon A contact lens only. The cornea was divided into five equally sized zones and the extent and depth of corneal staining were assessed on a zero to four scale. Results : The overall levels of corneal staining were low with median values below or equal to grade 0.5 in all groups. There was no difference in the extent, depth or geographical distribution of corneal staining between the DW and EW groups. Staining was more frequently recorded in the superior and inferior areas of the cornea than in the central, nasal or temporal regions (Pearson's Chi-Square, p < 0.10). Conclusions : The mode of wear with disposable contact lenses is not a contributing factor to the amount of corneal staining seen in successful wearers. Low levels of corneal staining should be expected in successful DW and EW wearers.     

角膜塑形镜治疗青少年中度近视的临床观察

目的观察夜戴型角膜塑形镜治疗青少年中度近视的临床疗效,以及戴镜1年后屈光度、角膜厚度和眼轴的变化。方法前瞻性临床研究。9～15岁的中度近视青少年患者87例（174眼）,平均等效球镜度为（-4.13±0.74）D;37例配戴角膜塑形镜,戴镜前和戴镜后1周、1个月、3个月、6个月、1年随访裸眼视力、角膜曲率;测量并比较1年后等效球镜度、角膜厚度及眼轴的变化。50例配戴框架眼镜,测量并比较1年后等效球镜度、眼轴的变化。对相关数据进行重复测量的方差分析和独立样本t检验。结果角膜塑形镜组戴镜1年后停戴1个月等效球镜度为（-4.69±0.57）D;框架眼镜组戴镜1年后为（-4.72±0.80）D,塑形镜组和框架组1年等效球镜度分别增加（0.31±0.21）D、（0.77-0.46）D,两者比较差异有统计学意义（t=30.109,P〈0.01）;眼轴增加分别为（0.11±0.26）mm、（0.26±0.60）mm,两者比较差异有统计学意义（t=18.565,P〈0.01）。角膜塑形镜组戴镜前与1年后角膜厚度无差异。结论角膜塑形镜治疗青少年中度近视效果确切;与框架眼镜相比,可明显减少近视增长,有效控制眼轴变长,一定程度上可以控制近视发展。     

Assessment of stromal keratocytes and tear film inflammatory mediators during extended wear of contact lenses

PURPOSE: To monitor quantitative changes in stromal keratocyte density and the level of tear film inflammatory mediators following extended contact lens wear. METHODS: Twenty-two subjects aged 32 +/- 11 years participated in this cross-sectional study. Eleven subjects had worn silicone hydrogel (Si-H) lenses on a 30-day continuous wear basis for 12 months. Eleven subjects had worn rigid gas permeable lenses on the same basis for 12 months. Eleven age-matched control subjects were also recruited. Ultrasound pachometry, confocal microscopy, and tear fluid sample collection were performed on all subjects. Tear samples were assayed for epidermal growth factor (EGF), hepatocyte growth factor (HGF) and interleukin (IL)-8. RESULTS: Corneal thickness was similar for all subject groups. Total keratocyte density was not different between the 3 groups; however, keratocyte density was lower for rigid lens wearers in the anterior to mid stroma and lower for Si-H lens wearers in the posterior stroma compared with control subjects. Rigid lens wearers exhibited an irregular keratocyte distribution across the corneal stroma. EGF concentration and rate of release was greater in the tears collected from the rigid lens wearers and Si-H lens wearers, and IL-8 concentration was higher in the samples collected from the rigid lens wearers compared with the samples collected from the control subjects. CONCLUSIONS: Mechanical stimulation of the corneal surface due to the physical presence of a contact lens and the consequent release of inflammatory mediators may account for a loss or redistribution of keratocytes.     

The size, location, and clinical severity of corneal infiltrative events associated with contact lens wear.

PURPOSE: The purpose of this study is to determine the relationship between the size, location, and clinical severity of corneal infiltrative events (CIEs) associated with contact lens wear. METHODS: We examined a series of contact lens wearers, presenting consecutively to a large hospital clinic, who had any form of CIE. The severity of the CIE was quantified using a clinical severity matrix based on scores attributed to each of 10 signs and symptoms. The infiltrate was accurately drawn on a schematic diagram of the ocular surface, and from this, we determined its size (i.e., largest dimension) and distance from the limbus. Cartograms were constructed to illustrate the size and location of the corneal infiltrates according to wearing modality and lens type. RESULTS: Useable data pertaining to 111 patients were analyzed. A significant positive correlation was found between the distance of the infiltrate from the limbus versus clinical severity (p = 0.002), but not between the distance of the infiltrate from the limbus versus infiltrate size (p = 0.97). The cartograms revealed a tendency for infiltrates to occur in the superior cornea of patients wearing extended wear silicone hydrogel lenses (p = 0.0002) in the central cornea of patients wearing daily wear hydrogel daily disposable lenses (p = 0.007) and in the peripheral cornea of patients wearing daily wear hydrogel (excluding daily disposable) lenses (p = 0.0006). CONCLUSIONS: These data statistically validate the previously held anecdotal notion that CIEs which occur in the peripheral cornea are less clinically severe than those which occur in the central cornea. Consideration of the distribution of CIEs may facilitate a better understanding of the etiology of these events and can serve to alert practitioners as to their likely clinical presentation.     

Impact of contact lens material and design on the ocular surface

Background

To evaluate the impact on the ocular surface of a daily disposable hydrogel contact lens with high water content compared with two silicone hydrogel daily disposable lenses of lower water content.

Methods

The hydrogel lens assessed was made from nesofilcon A and the silicone hydrogel lenses were made of delefilcon A and stenfilcon A. Contact lens thickness was measured to assess material stability during daily wear, and ocular surface parameters such as tear film osmolarity, tear meniscus area and central corneal thickness were also assessed. Optical quality was analysed for all cases by means of wavefront aberrometry.

Results

The nesofilcon A was shown to be the thinnest lens (p < 0.001), while no differences in lens thickness were found between the two silicone hydrogel lenses (p = 0.495). No significant differences were found in tear film osmolarity, tear meniscus area, central corneal thickness or corneal aberrations, either as a function of the lens measured or time of use (p > 0.05).

Conclusion

In spite of having the thinnest lens and the highest water content, the hydrogel does not significantly impact on tear film and corneal swelling after one day of use in first‐time wearers.

     

Corneal exhaustion syndrome with long-term wear of contact lenses.

After many years of successful contact lens wear, 3 long-term wearers of polymethyl methacrylate (PMMA) lenses (14, 15, and 18 years) and 1 long-term wearer of thick hydrogel lenses (11 years) suddenly developed intolerance to their lenses. Symptoms included ocular discomfort, reduced vision, and photophobia. All patients exhibited an excessive open-eye edema response with low to moderate Dk lenses. Posterior corneal changes included distortion of the endothelial mosaic and moderate to severe endothelial polymegethism. Patients were successfully refitted with lenses having higher oxygen transmissibility. It is proposed that long-term hypoxia and acidosis accompanying PMMA and thick hydrogel contact lens wear may be responsible for a syndrome characterized by endothelial dysfunction which results in inadequate regulation of corneal hydration and subsequent intolerance to contact lens wear. This condition has been termed Corneal Exhaustion Syndrome (CES).     

Objective and subjective responses in patients refitted to daily-wear silicone hydrogel contact lenses.

PURPOSE: Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. METHODS: Eighty-seven successful soft lens wearers (8.4+/-4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were "masked" as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. RESULTS: Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p<0.001), particularly for those subjects with greater baseline hyperemia (p<0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p<0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. CONCLUSIONS: Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort.