Comparison of the effects of first and second generation silicone hydrogel contact lens wear on tear film osmolarity Running title:Tear film osmolarity and silicone hydrogel contact lens wear

AIM: To evaluate the outcomes of pars plana vitrectomy (PPV) without the use of an ocular tamponade in patients having tractional retinal detachment (TRD) secondary to proliferative diabetic retinopathy (PDR).METHODS: It was an interventional study conducted at the Department of Ophthalmology, B.V. Hospital, Bahawalpur, Pakistan, from July 2011 to July 2012. A total of 75 patients (84 eyes) having TRD secondary to PDR were treated by PPV without using an ocular tamponade. All patients included in the study had a tractional retinal detachment secondary to proliferative diabetic retinopathy but didn’t have or develop retinal breaks before or during the study period. The surgical procedure included a PPV combined with the removal of the tractional retinal membranes and the application of endolaser photocoagulation to the retina. The mean follow-up period was 12 months.RESULTS:Successful retinal reattachement was observed in 78 of the operated eyes (92.8%). In these patients, the retina remained attached till the end of the one year follow-up period. Improvement in best corrected visual acuity (BCVA) was seen in 63 eyes (75%). The visual acuity remained unchanged in 9 eyes (10.7%). Mean improvement in BCVA was 2.00+1.24 at baseline to 1.24+1.22 (P<0.05) at the end of the follow-up period.CONCLUSION: In the absence of the retinal breaks, a TRD secondary to PDR can be successfully treated by pars plana vitrectomy without the use of an ocular tamponade.     

Comparison of tear osmolarity and ocular comfort between daily disposable contact lenses: hilafilcon B hydrogel versus narafilcon A silicone hydrogel

The aim of this study was to evaluate tear osmolarity and ocular comfort with two different types of hydrogel daily disposable lenses. The right eyes of 15 first-time contact lens users were included in this prospective study. All eyes wore hilafilcon B silicone hydrogel contact lenses for 8 h (group 1). After 1 week without contact lenses, all eyes wore narafilcon A silicone hydrogel contact lenses for 8 h (group 2). Tear osmolarity measurement was performed before and after 4 and 8 h of each contact lens wear. Ocular comfort was assessed after 4 and 8 h of each contact lens wear. In group 1, the mean baseline, 4- and 8-h tear osmolarity values were 293 ± 10.57, 303.00 ± 10.5 mOsm/L (p = 0.023), and 295.0 ± 1.4 mOsm/L (p > 0.05), respectively. In group 2, the mean baseline, 4- and 8-h tear osmolarity values were 294 ± 13.65, 300.9 ± 11.3 mOsm/L (p = 0.007), and 298.80 ± 7.2 mOsm/L (p > 0.05), respectively. In group 1, the mean comfort score was 7.20 ± 0.45 and 8.60 ± 0.45 at 4 and 8 h, respectively (p = 0.038). In group 2, the mean comfort score significantly decreased from 9.80 ± 0.45 to 7.80 ± 0.84 at 4 h (p = 0.039). Both hydrogel and silicone hydrogel daily disposable contact lenses elevated tear osmolarity during 8 h of contact lens wear. The increase in tear osmolarity with both contact lenses was below the cut-off value for dry eye and was not associated with ocular comfort.     

Comparison of tear-film osmolarity in different types of contact lenses.

PURPOSE: To investigate the tear-film osmolarity of contact lens wearers for different types of contact lenses. METHODS: Fifty six eyes of 56 cases were evaluated in four different groups according to the type of contact lens worn, with 14 eyes in each group. Groups 1 and 2 consisted of subjects who wore frequent-replacement daily wear soft contact lenses; group 1 lenses had 55% water content, and lenses in group 2 had 38% water content. Groups 3 and 4 consisted of subjects who wore rigid gas-permeable contact lenses, with a Dk value of 90 in group 3 and a Dk value of 52 in group 4. Tear-film osmolarity values in milliosmole (mosm) units were determined by auto-osmometer (Orstat 6030, Daiichi Kagacu, Kyoto, Japan) before and after contact lens wear for each group, and the results were compared statistically by ANOVA test. RESULTS: Before the period of contact lens wear, the tear-film osmolarity values of group 1, 2, 3, and 4 were 283.61+/-12.83 mosm, 285.23+/-8.94 mosm, 285.57+/-11.39 mosm, and 280.15+/-12.07 mosm, respectively. After the period of contact lens wear, these values were measured at 312.15+/-16.03 mosm in group 1, 316.54+/-12.14 mosm in group 2, 313.14+/-9.66 mosm in group 3, and 316.38+/-11.60 mosm in group 4. Although the difference between the values before and after the period of contact lens wear was statistically significant for each group (F=291.45; P=0.0005), there was no statistically significant difference among the groups. CONCLUSIONS: When a contact lens is placed in the eye, the lens alters the normal structure of the tear film and affects its rate of evaporation; therefore tear-film osmolarity may increase. In our study, all contact lenses produced a similar effect on tear-film osmolarity.     

Tear osmolarity in unilateral pseudoexfoliation syndrome

Purpose: The aim was to evaluate tear osmolarity of patients with clinically unilateral pseudoexfoliation (PEX) syndrome and to compare the values with otherwise normal subjects. Methods: Sixty‐two eyes of 31 patients with unilateral PEX syndrome and 31 eyes of 31 normal subjects were studied. The TearLab osmolarity system (OcuSense, Inc, San Diego, CA, USA) was used to measure tear osmolarity. Eyes were grouped as normal eyes of patients having unilateral PEX syndrome (group A), eyes of patients having unilateral PEX syndrome with deposits of PEX material (group B) and eyes of normal subjects (group C). Differences in tear osmolarity were compared among groups A, B and C. Independent t‐tests and paired t‐tests were used for statistical analysis. Results: The mean tear osmolarity was 298.7 ± 7.8 mOsm/l (range 285 to 306) in the control group (group C), 306.3 ± 6.6 mOsm/l (range 290 to 314) in the eyes of patients having PEX syndrome with deposits of pseudoexfoliative material (group B) and 301.4 ± 7.1 mOsm/l (range 284 to 305) in the fellow eye of these patients (group A). There was a significant difference between tear osmolarity of groups C and B (independent t‐test, p = 0.011). Also, there was a significant difference between the osmolarity of each eye of patients with unilateral PEX syndrome (groups A and B) (paired t‐test, p = 0.001). The difference between tear osmolarity of groups A and C was not statistically significant (independent t‐test, p = 0.146). Conclusion: In conclusion, tear osmolarity is higher in both eyes of patients when compared with normal subjects, using the independent t‐test (although highest in clinically positive eyes of these patients). Both eyes of patients having PEX syndrome could be more prone to the development of dry eye syndrome.     

地夸磷索钠联合玻璃酸钠改善配戴角膜塑形镜后的泪膜稳定性

目的：探究地夸磷索钠滴眼液联合玻璃酸钠滴眼液对改善角膜塑形镜配戴后的泪膜稳定性的作用。

方法：前瞻性研究。选取2022-03/08于安徽爱尔眼科医院门诊就诊的初次配戴角膜塑形镜患者82例82眼(均取右眼数据),根据随机数字表法分为玻璃酸钠组(玻钠组)30眼、地夸磷索钠组(地夸组)24眼和地夸磷索钠联合玻璃酸钠组(联合组)28眼,各组患者均配戴同一品牌的角膜塑形镜。每位患者分别在配戴角膜塑形镜前,配戴后1 d,1 wk,1 mo进行非接触式泪膜破裂时间(NIBUT)、非接触式泪河高度(NITMH)和脂质层厚度检查,并记录患者是否有角膜点染。

结果：联合组与地夸组治疗1 mo的NITMH与NIBUT较配戴前升高(均P<0.05)。配戴1 mo,联合组的NIBUT和NITMH分别为19.74±3.29 s和0.30±0.05 mm,均优于地夸组(NIBUT：16.09±2.98 s,NITMH：0.22±0.08 mm)和玻钠组(NIBUT：15.67±3.90 s,NITMH：0.22±0.04 mm)(均P<0.01)。各组间脂质层厚度均无明显差异(均P>0.05)。各组患者角膜点染发生率无明显区别(P>0.05)。

结论：地夸磷索钠滴眼液联合玻璃酸钠滴眼液在配戴角膜塑形镜后1 mo对改善NIBUT和NITMH有更佳的效果,有效提高配戴角膜塑形镜患者的泪膜稳定性。     

El ojo seco está relacionado con un aumento intrasujeto de la variabilidad de osmolaridad lagrimal confirmado por tecnología de aprendizaje de máquinas

ObjectiveBecause of high variability, tear film osmolarity measures have been questioned in dry eye assessment. Understanding the origin of such variability would aid data interpretation. This study aims to evaluate osmolarity variability in a clinical setting.Material and methodsTwenty dry eyes and 20 control patients were evaluated. Three consecutive osmolarity measurements per eye at 5 min intervals were obtained. Variability was represented by the difference between both extreme readings per eye. Machine learning techniques were used to quantify discrimination capacity of tear osmolarity for dry eye.ResultsMean osmolarities in the control and dry eye groups were 295.1 ± 7.3 mOsm/L and 300.6 ± 11.2 mOsm/L, respectively (P = .004). Osmolarity variabilities were 7.5 ± 3.6 mOsm/L and 16.7 ± 11.9 mOsm/L, for the control and dry eye groups, respectively (P < .001). Based on osmolarity, a logistic classifier showed an 85% classification accuracy.ConclusionsIn the clinical setting, both mean osmolarity and osmolarity variability in the dry eye group were significantly higher than in the control group. Machine learning techniques showed good classification accuracy. It is concluded that higher variability of tear osmolarity is a dry eye feature.     

Preliminary tear film measurements of tolerant and non-tolerant contact lens wearers

Background : The relationship between contact lens intolerance and tear stability, tear quantity, distribution and consistency has yet to be clearly established. In this study, we have examined the tear film of several tolerant and non-tolerant soft contact lens wearers. We aimed to develop a number of clinical and biochemical techniques to establish a correlation between one or more factors leading to contact lens intolerance. Methods : Subjects were separated by their self-described tolerance to contact lens wear. Five tolerant and five non-tolerant subjects were chosen. A McMonnies symptomatology questionnaire was used to ascertain subject history, while non-invasive tear break-up time (TBUT) examined tear stability. Basal tear collection was performed using glass capillary tubes, the tear flow rate was measured and one dimensional gel electrophoresis used to analyse protein differences. Results : Non-tolerant subjects experienced primary symptoms, such as dryness and grittiness, more often than tolerant subjects (p = 0.007). The TBUT of non-tolerant lens wearers was also reduced (average of seven seconds) compared to tolerant lens wearers (p < 0.002). Tolerant lens wearers had a longer more stable tear film with an average TBUT of 20 seconds and this correlated with a fast tear flow rate (p < 0.04). Protein gel electrophoresis showed that some subjects who were non-tolerant to lens wear had variations in their tear protein profiles compared to tolerant subjects. Conclusion : These preliminary results demonstrate that clinical and biochemical tear profiles can be used to differentiate subjects with good lens wear tolerance from those who may be non-tolerant to lens wear.     

Role of tear secretory IgA in hard contact lens-related changes in the tarsal conjunctiva.

The role of tear secretory IgA in contact lens-related conjunctival changes was investigated in 40 subjects (80 eyes) who wore polymethyl methacrylate (PMMA) contact lenses and 10 subjects (20 eyes) who did not wear contact lenses. The eyes in the contact lens group had significantly higher tear IgA levels than the control eyes (p < 0.05). We were not able to demonstrate a relation between increased IgA levels and the presence of symptoms or duration of contact lens wear. Increased IgA levels were correlated to papilla formation in the contact lens group. A rise in tear IgA levels seems to be the first abnormal change related to papilla formation in patients who wear PMMA contact lenses.     

Changes in ocular physiology, tear film characteristics, and symptomatology with 18 months silicone hydrogel contact lens wear.

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.     

Randomised controlled trial of the effects of two rigid gas permeable (RGP) contact lens materials and two surface cleaners on straylight values

Purpose: In a double‐masked randomized controlled crossover study we investigated both the retinal responses to straylight, and the effects of lens cleaners on straylight values, in two different RGP contact lens materials. Methods: Thirty patients (20–59 years) wearing RGP lenses were refitted with new lenses made of Boston XO material in one eye and made of Comfort O2 (ONSI‐56) material in the other eye. Reported wetting angles for the Boston XO material (103°) and for the ONSI‐56 material (7.2°) were obtained by sessile drop measurements. After refitting, the study comprised three 5‐week trial periods. In Period 1 half of the participants (Group A) wore Boston XO lenses in their right eye and Comfort O2 (ONSI‐56) lenses in their left eye, and the other half (Group B) vice versa. In Period 2 Group A wore Comfort O2 (ONSI‐56) lenses in their right eye and Boston XO lenses in their left, and Group B vice versa. All participants used Miraflow cleaner during periods 1 and 2. In Period 3, during which all participants used Boston cleaner, Group A wore Boston XO lenses in their right eye and Comfort O2 (ONSI‐56) lenses in their left eye and Group B vice versa. Straylight data (log S) were obtained with and without contact lenses using the Oculus C‐Quant straylight meter in all three periods. Central corneal thickness (CCT) was measured in the second and third periods. Results: When not wearing lenses (n = 60 eyes) at the end of the second 5 week trial period straylight was measured twice with averages of 1.07 log S, and the corrected CCT measurements averaged 546 μm. Straylight values with Comfort O2 (ONSI‐56) reached 1.15 log S at the end of both the second (n = 25 eyes) and third periods (n = 23 eyes). Straylight values with Boston XO were 1.17 log S (n = 26 eyes) at the end of the second period, and 1.16 log S (n = 25 eyes) at the end of the third period. Conclusions: Existing RGP lens wearers refitted with new lenses with different contact angles, made of Boston XO and Comfort O2 (ONSI‐56) showed, over three 5 week periods, relatively small increases in straylight, which were functionally comparable, irrespective of the type of lens material or lens cleaner used. At every visit, straylight values and CCTs returned to baseline levels after RGP lens removal, confirming that the straylight fluctuations were mainly due to scattering from the RGP lenses; or tear film interaction; or a combination of both.     

Increased Tear Film Osmolarity in Systemic Lupus Erythematosus

Purpose: To evaluate tear film osmolarity in patients with systemic lupus erythematosus (SLE). Methods: A total of 55 eyes from 55 patients with SLE and 47 eyes from 47 age- and gender-matched healthy individuals were included in this study. Tear film osmolarity was evaluated with a lab-on-a-chip technique (TearLab; TearLab Corporation, San Diego, CA) in SLE patients in comparison with healthy individuals, and results were correlated to clinically available diagnostic tests for dry eye, such as tear ?lm break-up time (BUT), Schirmer’s test, and Ocular Surface Disease Index (OSDI). Results: The mean tear film osmolarity in the SLE patients and healthy individuals was 306.02 ± 13.27 mOsm/L and 300.74 ± 9.11 mOsm/L, respectively, which made for a statistically significant difference (p = 0.020). In the SLE group, tear film osmolarity was negatively correlated with the Schirmer’s test score and the BUT value (r = ?0.295 p = 0.029 and r = 0.347 p = 0.009, respectively), whereas tear film osmolarity was not correlated with OSDI score (r = ?0.182 p = 0.183). Conclusions: This study revealed that tear film hyperosmolarity and abnormal tear film function are associated with SLE.     

Hydrogel lens wettability and deposition in vivo

Background : Wearing a hydrogel contact lens disrupts tear film stability, resulting in a low non-invasive surface drying time (NISDT) on the lens front surface. Reduced wettability causes deposit formation, reducing the quality of vision and lens comfort. This investigation determined the effect of commercially available HEMA-based materials on pre-lens tear film stability and deposition. Methods : Twenty patients in a randomised, double blind study wore four lenses for eight hours. These lenses were Tefilcon, Polymacon (Group I lenses), Vifilcon A and Etafilcon A (Group IV lenses). Non-invasive surface drying time (NISDT) was measured for each lens type after 10 minutes, one hour, four hours and eight hours wear. Lenses were then removed and examined by scanning electron microscopy. Results : NISDT decreased significantly (p < 0.05) over the eight-hour wear period for all lens types. Group IV lenses showed a slightly, but not clinically significantly, higher NISDT compared to Group I lenses. A greater number of deposits was seen on Vifilcon A and Polymacon compared to Etafilcon A and Tefilcon lenses. Conclusions : Wear decreases lens wettability over eight hours, irrespective of lens type. Higher wettability was seen with Group IV lenses, although the increase was not clinically significant. Wettability was not correlated with the formation of discrete deposits. Deposit formation depends on the composition of the lens base material, its ionic charge, surface topography, water content and wearers' ocular characteristics.     

Ocular surface assessment in soft contact lens wearers; the contribution of tear osmolarity among other tests

Purpose:  To determine whether tear osmolarity contributes to the assessment of the ocular surface in soft contact lens (CL) wearers. Methods:  Prospective, case–control series in 44 CL wearers (28 tolerant and 16 intolerant) and 34 healthy subjects. Every patient underwent a thorough ophthalmic examination with a tear osmolarity test (TearLab System), conjunctival impression cytology and meibomian lipid sampling. Symptoms, break‐up time (BUT), tear osmolarity, conjunctival expression of HLA‐DR and meibomian fatty acid composition were evaluated. Results:  Tear osmolarity did not differ between controls and CL wearers (p = 0.23). Flow cytometry results expressed in antibody‐binding capacity (ABC) units and percentage of positive cells revealed a significant difference between the intolerant CL wearer group and the control group (p < 0.0001). Comparisons between tolerant and intolerant CL wearers showed only a significant difference for mean fluorescence levels expressed in ABC units (p < 0.0001). The BUT was significantly shorter in intolerant and tolerant CL wearers subjects than in healthy subjects (p < 0.0001), whereas there was no significant difference in meibomian fatty acid composition (p = 0.99) between the two groups. Conclusion:  Contact lens wear is responsible for ocular surface alterations whose patterns are very similar to those reported in early dry‐eye syndrome. However, tear osmolarity was not modified in these selected CL wearers. The yield of tear osmolarity with TearLab? in assessing ocular surface disorders in CL wearers deserves further investigation.     

翼状胬肉切除术中亲水软性角膜接触镜的应用

目的:探讨翼状胬肉切除术中应用亲水性软性角膜接触镜减轻异物感和刺激症状的安全性及有效性.方法:选取2011-05/2013-06在南京市高淳人民医院就诊的翼状胬肉患者86例86眼,均接受翼状胬肉切除联合自体角膜缘干细胞移植术,其翼状胬肉长入角膜缘内2.5～7mm,随机分为两组:软性角膜接触镜和对照组,每组43例43眼.亲水性软性角膜接触镜组在手术结束时涂入氧氟沙星眼膏于角膜结膜表面,配戴角膜接触镜,不用纱布敷眼,术后2d取下亲水性软性角膜接触镜,对照组不作任何处理.术后用纱布覆眼,比较术后2、6、8、24、48、72h两组患者疼痛程度,术后3d角膜上皮荧光素染色评分及角膜上皮缺损面积的差异,并观察并发症的发生情况.结果:两组患者年龄、性别及翼状胬肉大小差异均无统计学意义(P＞0.05).术后2、6、8、24、48、72h两组患者疼痛程度评分,软性角膜接触镜组分别为0.80±0.41、0.89±0.52、0.42±0.49、0.28±045、0.30±0.43、0.25±0.35分;对照组分别为2.56±0.52、2.57 ±0.25、1.85 ±0.67、1.44±0.50、1.42±0.52、0.85±0.53分;亲水性软性角膜接触镜组患者疼痛评分均较对照组显著降低(P＜0.01).术后角膜上皮染色评分对照组为1.58±1.35分,亲水性软性角膜接触镜组为0.89±1.12分,两组间差异无统计学意义(P=0.140).角膜上皮缺损面积:对照组为2.69±4.34mm2,亲水性软性角膜接触镜组为0.18±0.46mm2,两组间差异有统计学意义(P=0.048).随访3～ 12(平均4.50±1.25)mo,未见感染、复视、植片愈合不良,有2眼发生鼻侧伤口处球形肉芽,经表面麻醉下切除后未复发.结论:软性角膜接触镜可明显减轻翼状胬肉术后疼痛反应,促进角膜上皮愈合,是一种安全、有效的辅助治疗措施.     

Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible.

PURPOSE: To determine whether the eyes of high-Dk soft contact lens wearing subjects can be discriminated from non-contact lens wearing subjects. METHODS: This study was a prospective masked assessment of 32 subjects, 16 of whom wore experimental high-Dk soft contact lenses and 16 of whom did not wear contact lenses. Subjects wore high-Dk lenses on a 30-night replacement schedule for an average of 9 months. Tear film characteristics, staining and vascularization of the cornea, conjunctival staining, and the presence of microcysts in the corneal epithelium were assessed using slitlamp microscopy. The endothelium was examined for polymegethism. RESULTS: No differences were found between the two groups in any of the variables that were examined (p > 0.05) except that the high-Dk lens wearing group had about twofold more tear film debris and 2.5-fold more severe conjunctival staining (p < 0.05). CONCLUSIONS: Hypoxia-associated effects were not apparent in the eyes of subjects wearing experimental high-Dk soft contact lenses. Conjunctival staining can generally distinguish lens wearers from non-lens wearers and can be used to discriminate between high-Dk lens wearing subjects and non-lens wearing subjects.     

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.     

Protection against corneal hyperosmolarity with soft-contact-lens wear

Hyperosmotic tear stimulates human corneal nerve endings, activates ocular immune response, and elicits dry-eye symptoms. A soft contact lens (SCL) covers the cornea preventing it from experiencing direct tear evaporation and the resulting blink-periodic salinity increases. For the cornea to experience hyperosmolarity due to tear evaporation, salt must transport across the SCL to the post-lens tear film (PoLTF) bathing the cornea. Consequently, limited salt transport across a SCL potentially protects the ocular surface from hyperosmotic tear. In addition, despite lens-wear discomfort sharing common sensations to dry eye, no correlation is available between measured tear hyperosmolarity and SCL-wear discomfort. Lack of documentation is likely because clinical measurements of tear osmolarity during lens wear do not interrogate the tear osmolarity of the PoLTF that actually overlays the cornea. Rather, tear osmolarity is clinically measured in the tear meniscus. For the first time, we mathematically quantify tear osmolarity in the PoLTF and show that it differs significantly from the clinically measured tear-meniscus osmolarity. We show further that aqueous-deficient dry eye and evaporative dry eye both exacerbate the hyperosmolarity of the PoLTF. Nevertheless, depending on lens salt-transport properties (i.e., diffusivity, partition coefficient, and thickness), a SCL can indeed protect against corneal hyperosmolarity by reducing PoLTF salinity to below that of the ocular surface during no-lens wear. Importantly, PoLTF osmolarity for dry-eye patients can be reduced to that of normal eyes with no-lens wear provided that the lens exhibits a low lens-salt diffusivity. Infrequent blinking increases PoLTF osmolarity consistent with lens-wear discomfort. Judicious design of SCL material salt-transport properties can ameliorate corneal hyperosmolarity. Our results confirm the importance of PoLTF osmolarity during SCL wear and indicate a possible relation between PoLTF osmolarity and contact-lens discomfort.     

配戴软性角膜接触镜对角膜中央厚度影响的临床研究

目的:探讨配戴软性角膜接触镜对中央角膜厚度的影响。方法:应用超声角膜测厚仪检测中央角膜厚度,在我院近视患者中随机抽取配戴软性角膜接触镜者及不戴镜者各100例200眼,做统计分析。再在近视患者中按戴镜时间<1a,1～3a,3～5a,5～7a,≥7a分组,每组随机抽取60例120眼,做统计分析。结果:配戴软性角膜接触镜者与不戴镜者的角膜厚度比较,差异有统计学意义(P<0.05)。戴镜时间<1a,1～3a,3～5a,5～7a者的角膜厚度比较,差异有统计学意义(P<0.05)。结论:配戴软性角膜接触镜者平均中央角膜厚度薄于不戴角膜接触镜者,并且配戴软性角膜接触镜的时间越长中央角膜厚度越薄。     

Effects of a 0.9% sodium chloride ophthalmic solution on the ocular surface of symptomatic contact lens wearers

BACKGROUND: Ocular surface-related discomfort is the main reason for stopping contact lens wear. We carried out a study to evaluate the efficacy of preservative-free artificial tears containing 0.9% sodium chloride on ocular surface signs and symptoms in contact lens wearers experiencing discomfort and its possible influence on the duration of contact lens wear. METHODS: We studied 49 contact lens wearers experiencing discomfort who had normal results of slit-lamp biomicroscopy, a fluorescein tear film break-up time (BUT) of 10 seconds or more, and wetting greater than 5 mm in 5 minutes on the Schirmer 1 test with and without anesthesia. Twenty-nine subjects (16 men and 13 women with a mean age of 32.5 years [standard deviation (SD) 8.7 years]) received one instillation of the 0.9% sodium chloride solution four times daily in the lower conjunctival fornix for 21 days. Twenty subjects (12 men and 8 women with a mean age of 35.1 [SD 6.2] years) received no drops and served as a control group. The overall comfort and duration of contact lens wear, results of tear film analysis and adverse events were recorded on days 7 and 21. Patients rated their symptoms (while not receiving any medications or hydrating solutions) on a 100-mm visual analogue scale with "Excellent (lenses not felt)" at the left and "Very uncomfortable (lenses cause irritation or discomfort)" at the right. Measurement of corrected visual acuity, slit-lamp examination, determination of the tear film BUT, the Schirmer 1 test with and without anesthesia, and assessment of the colour and surface of the lens were performed at baseline and at day 21. We analysed the data for the more uncomfortable eye or, if the eyes were equally uncomfortable, the right eye. RESULTS: Significant lessening of ocular discomfort was observed in the treatment group during the study: the mean rating on the visual analogue scale at baseline was 60.2 mm (SD 12.7 mm), compared with 35.8 mm (SD 18.0 mm) at day 21 (p < 0.001, Student's t test). The duration of contact lens wear was significantly longer at day 21 than at baseline (7.0 [SD 2.6] hours vs. 6.4 [SD 2.6] hours, p < 0.05, Student's t test), and the proportion of subjects with conjunctival hyperemia was significantly lower at day 21 (48.3% vs. 82.8%, p < 0.05, chi2 test). No statistically significant changes were observed in tear film BUT, results of the Schirmer 1 test, corneal punctate staining by fluorescein or results of tear film analysis. The treatment was well tolerated by all patients. No significant differences in any of the variables studied were observed in the control group. INTERPRETATION: Treatment with a preservative-free 0.9% sodium chloride ophthalmic solution reduced ocular surface discomfort and extended the duration of contact lens wear without interfering with the tear film or contact lens materials. Long-term studies are needed to confirm the role of this solution in reducing discomfort experienced by contact lens wearers.     

The effects of six months of contact lens wear on the tear film, ocular surfaces, and symptoms of presbyopes.

PURPOSE: To assess the tear film, ocular surfaces, and symptoms of ocular discomfort in a presbyopic population before and after contact lens wear. METHODS: A total of 150 presbyopes (49% were previous soft contact lens wearers) participated in a clinical trial in which they wore either monovision (single vision Acuvue lenses) or Acuvue Bifocal contact lenses. Clinical measurements of tear film, biomicroscopy, and corneal sensitivity as well as subjective ratings using the Dry Eye Questionnaire were collected at the initial visit and repeated after 6 months. Comparisons were made between age groups (40 to 51 years and 52 to 71 years) and genders before and after contact lens wear. Associations between objective and subjective tests were sought. RESULTS: After 6 months of contact lens wear, clinical signs had worsened by less than one-half of a grade, and tear break up time (TBUT) worsened by 3 s. Only TBUT was lower for the older age group. Females had less bulbar hyperemia, more sensitive eyes, more lissamine green staining, and lower TBUT and phenol red thread measurements (all p < 0.04). Twenty-eight percent experienced dryness before contact lens wear, but this figure increased to 68% when wearing contact lenses. There were no age differences, but almost twice as many females as males reported dryness. Reporting symptoms of dryness was associated with gender, corneal sensitivity, and type of corneal staining. CONCLUSIONS: These results provide a representation of the ocular surface condition and symptoms of ocular discomfort in the middle-aged population and seem similar to reports of younger populations. Wearing contact lenses seems to influence dry eye symptoms more than age or gender. Therefore, presbyopes should not be excluded from consideration for contact lens fitting.