Proliferation rate of rabbit corneal epithelium during overnight rigid contact lens wear.

PURPOSE: To examine cell proliferation of the normal corneal epithelium and during extended rigid gas-permeable (RGP) lens wear. METHODS: Twenty-three New Zealand White rabbits were fitted unilaterally with either a low oxygen transmissible (Dk/t) or hyper-Dk/t RGP lens, with the other eye serving as a control. The rabbits were injected with 5-bromo-2-deoxyuridine (BrdU) 24-hours later and killed at three time points: 1, 3, and 7 days after injection. Corneas were processed for immunocytochemistry, and sequential digital images were taken from the superior limbus to the central epithelium with an epifluorescence microscope. The total number of BrdU-labeled cell pairs was quantified. RESULTS: The limbus in normal corneas was significantly less populated with BrdU-labeled cells than the central and peripheral epithelium (P < 0.05). The peripheral epithelium adjacent to the limbus was marked by a peak of labeled cells (P < 0.05). Both types of RGP lenses produced an increase in BrdU labeling in the limbus and a dramatic decrease in the central epithelium (80% for low Dk/t, 37% for hyper Dk/t). At day 3 and 7 after BrdU injection, the low-Dk/t lens continued to show decreased BrdU labeling centrally, whereas the limbus remained increased. Hyper-Dk/t lens wear however, showed persistent limbal elevation but equivalent numbers of BrdU-labeled cells centrally at days 3 and 7, compared with control corneas. Keratocytes unexpectedly showed BrdU labeling during RGP lens wear. CONCLUSIONS: Limbus, peripheral, and central epithelium were characterized by different proliferation rates in the normal rabbit cornea. RGP lens wear significantly altered the homeostatic proliferation pattern of the epithelium with the low-Dk/t lens having the most dramatic effect. RGP contact lens wear appears to stimulate proliferation of keratocytes.     

Spherical indentations of human and rabbit corneal epithelium following extended contact lens wear.

PURPOSE: Mucin balls appear to cause spherical indentations in the corneal epithelium during silicone hydrogel extended contact lens wear. The purpose of this report is to describe and quantify these spherical indentations, as examined in the human cornea by in vivo confocal microscopy and by in vitro immunocytochemistry in the rabbit cornea. METHODS: Confocal images of full-thickness corneal epithelium were taken from three human patients participating in a 1-year extended contact lens-wear trial. Diameter and depth of the indentations were determined and measured. Two rabbit corneas showing identical indentations were stained with propidium iodide (nuclear stain) and Ki-67 (proliferation marker) and were examined using a laser scanning confocal microscope. RESULTS: The diameter of the spherical indentations is largest on the epithelial surface, ranging from 33.9 to 78.8 microm. Indentations form spherical sections whose depth variably extends into the corneal epithelium, reaching as far as the basal lamina. The rabbit model showed no epithelial nuclei within the indentation. Furthermore, stromal cells localized immediately beneath the indentations were positive for Ki-67 (proliferation). DISCUSSION: Spherical indentations of the corneal epithelium induced by mucin balls appear to be gaps or holes that can extend deep into the corneal epithelium. Indentations may potentially open a pathway for infectious microorganisms to penetrate the cornea. Surprisingly, stromal cells immediately beneath the holes were stimulated to proliferate, and there seemed to be an increase in localized cell density.     

Morphology of corneal nerves in soft contact lens wear. A comparative study using confocal microscopy

The aim of this study was to evaluate corneal innervation in soft contact lens wearers using the Tomey Confoscan confocal microscope (40x/0.75 objective lens). Three distinct age- and sex-matched subject groups were involved, including extended soft (hydrogel and silicone-hydrogel) contact lens wearers, overnight soft (hydrogel) contact lens wearers, and non contact lens wearers. A number of variables were objectively measured, subjectively evaluated, or graded in order to investigate the distribution and morphology of corneal nerves. For most of the evaluated parameters, no statistically significant differences were found. However, qualitative observations showed noticeable differences in corneal nerve appearance among the different subject groups; the degree of corneal oedema was suggested as the main causative factor. In conclusion, neither the short-term (overnight wear) nor the long-term (12-month extended wear) soft contact lens wear appeared to affect the morphology and/or distribution of corneal nerves as viewed with confocal microscopy.     

Impact of rigid gas-permeable contact lens extended wear on corneal epithelial barrier function

PURPOSE: To measure the effect of hypoxia and eye closure on epithelial permeability to fluorescein (P(dc)) during rigid lens extended wear (EW). METHODS: Central corneal thickness (CT) and P(dc) were measured in 42 subjects with an optical pachometer and automated scanning fluorophotometer, respectively. All subjects had been successfully wearing rigid gas-permeable (RGP) lenses on a 6-night EW regimen, and each individual was randomized to wear either medium- or high-oxygen-permeable (Dk) RGP lenses (two types of siloxane-fluorocarbon polymer lenses with Dk of 49 and 92). CT and P(dc) measurements were performed at an afternoon visit (baseline) and were repeated in the morning after 8 hours of overnight wear. Subjects slept with a patch over the right eye. The patch was not removed until immediately before the morning measurement. RESULTS: The mean overnight swelling response for subjects in the medium-Dk group was greater than that in the high-Dk group. Results of a paired t-test indicate that the eye wearing the medium-Dk lens with a patch overnight had a significant increase in epithelial permeability. Results of mixed-effect models suggest that eye closure and lens-induced hypoxia are significant factors in altering P(dc). CONCLUSIONS: The results indicate that corneal epithelial permeability increases with hypoxic dose and that epithelial barrier function is impaired by overnight rigid lens wear.     

连续配戴软性角膜接触镜对眼表上皮的影响

目的:探讨软性角膜接触镜(soft contact lens,SCL)连续配戴对眼表上皮的影响以及可能机制。方法:将SCL配戴者依据连续戴镜时间分为<12h组、12~24h组和>24h组,共3组。对正常对照组(35例70眼)与病例组(99例198眼)进行用角膜荧光素染色(fluores-cein vital staining,FLS)、结膜印迹细胞学检查(conjunctivalimpression cytology,CIC),对比各组间各观察指标差异。结果:SCL戴镜各组FLS记分、杯状细胞密度与结膜上皮鳞状化分级与正常对照组间差异有统计学意义(P<0.01);<12h组与12~24h组之间,<12h组与>24h组之间FLS、杯状细胞密度与结膜上皮鳞状化分级的差异有统计学意义(P<0.05);12~24h组与>24h组之间FLS、杯状细胞密度与结膜上皮鳞状化分级的差异无统计学意义。结论:连续配戴软性角膜接触镜会导致眼表上皮损伤和结膜杯状细胞减少,结膜上皮角化。且持续戴镜时间越长,变化越明显。     

Effects of rigid gas permeable contact lens solutions on the human corneal epithelium.

In this investigation, the effects of three rigid gas permeable (RGP) contact lens wetting and soaking solutions, Boston Advance Conditioning Solution, Boston Conditioning Solution, and Allergan Wet-N-Soak Plus, were tested on the human corneal epithelium. Thirty subjects participated in three experimental sessions, during which one eye received three drops of one of these RGP solutions, while the other eye served as a control. After 10 and 30 min, corneal staining was graded in 5 areas and the eyes were photographed for a digitized analysis of staining. Our results indicate that corneas exposed to Boston Advance Conditioning Solution demonstrated significantly more fluorescein staining than control eyes at both 10 and 30 min by both methods of analysis, whereas corneas treated with the other two solutions were not significantly different from controls. The increased corneal staining noted with Boston Advance Conditioning Solution may be caused by the presence and concentration of the preservative, 0.0015% polyaminopropyl biguanide. An unforeseen result of this experiment was the relatively large number of subjects exposed to Boston Conditioning Solution and Allergan Wet-N-Soak Plus who had more corneal staining in the control eye. This may suggest that the two RGP solutions served as a barrier to fluorescein, protecting the epithelial cells from staining.     

Effect of rigid gas permeable contact lens wetting solutions on the rabbit corneal epithelium

This investigation was designed to compare the effects of three rigid gas permeable (RGP) contact lens solutions on the rabbit corneal epithelium. Boston Advance Conditioning Solution, Boston Conditioning Solution, and Allergan Wet-N-Soak, which are preserved with 0.0015% polyaminopropyl biguanide, 0.006% chlorhexidine gluconate, and 0.003% benzalkonium chloride, respectively, were evaluated by scanning (SEM) and transmission electron microscopy (TEM). Our results show that Boston Advance Conditioning Solution is significantly more toxic to the corneal epithelium than either Boston Conditioning Solution or Allergan Wet-N-Soak Plus. This is presumably due to the presence and concentration of the preservative, 0.0015% polyaminopropyl biguanide. Although this study was conducted using rabbits, the results raise clinical concerns for human RGP contact lens wearers.     

Effects of an experimental contact lens disinfectant on rabbit corneal epithelium cultures.

We investigated the toxicity of a new, chlorine-based, experimental contact lens disinfectant (Alcide Corp., Norwalk, CT) on rabbit corneal epithelium in tissue culture. Explants of isolated corneal epithelium were grown in tissue culture for 7 days and then exposed for 1 h to one of three different concentrations of the experimental disinfectant or to a saline control. At the manufacturer's standard concentration, and at one-half the standard concentration, the relative area covered by living cells in the culture was reduced an average of 32% 3 days after treatment. At double the standard concentration, the area was reduced 63%, which was a significant reduction in comparison with controls. All groups showed some recovery in area of living epithelial cells within 7 days after treatment. In comparison with similar studies on other chemicals used in ophthalmic preparations, these results suggest that this chlorine-based disinfectant is relatively nontoxic to corneal epithelial cells.     

Effects of low and hyper Dk rigid gas permeable contact lenses on Bcl-2 expression and apoptosis in the rabbit corneal epithelium.

PURPOSE: To study Bcl-2 expression and apoptotic cell shedding of the rabbit corneal epithelium during extended wear of low and hyper Dk rigid gas permeable (RGP) contact lenses. METHODS: Rabbits were fit with either a low or a hyper Dk RGP lens (Dk/Ltotal= 10 and 97). The rabbits wore the lenses for either 24 hours, 3 days, or 1 week at which point they were humanely sacrificed. Immunocytochemistry and western blot analyses were performed to detect Bcl-2 in the corneal epithelium; TUNEL assay (TdT-mediated dUTP nick-end labeling) was used to identify apoptotic epithelial cells. RESULTS: 1) Immunocytochemistry: In the normal cornea, antibodies to Bcl-2 uniformly stained nuclei of all epithelial cell layers. Occasional surface epithelial cells, however, showed no anti-Bcl-2 nuclear staining; concomitant TUNEL assay revealed that all TUNEL-labeled-surface cells were Bcl-2 negative. By contrast, RGP contact lens wear, regardless of test lens oxygen transmissibility or lens wearing interval, significantly decreased both the total number of Bcl-2 negative and TUNEL-labeled cells on the epithelial surface (P < 0.05). In addition, contact lens wear was associated with labeling of keratocytes with TUNEL assay in the anterior stroma. 2) Western blot analysis: Total epithelial layer Bcl-2 expression was markedly decreased in the low Dk lens test group but was similar to control values in the hyper Dk lens test group. CONCLUSION: Bcl-2 protein seems to play an important role in the regulation of apoptotic cell shedding in the normal rabbit corneal epithelium. The identical staining pattern was seen in previous studies of the normal human cornea. RGP contact lens wear, however, appears to block the changes in Bcl-2 protein prior to apoptotic surface cell shedding, suggesting a lens-related anti-apoptotic effect. Taken together, these findings may explain why contact lens wear reduces surface cell exfoliation as previously reported in human studies.     

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.     

Effects of eyelid closure and disposable and silicone hydrogel extended contact lens wear on rabbit corneal epithelial proliferation

PURPOSE: To examine the rabbit corneal epithelial cell proliferation rate after extended wear of disposable or silicone hydrogel contact lenses or prolonged eyelid closure. METHODS: One randomly chosen eye of 40 New Zealand White rabbits was assigned to silicone hydrogel contact lens wear (n = 15, SH), disposable hydrogel contact lens wear (n = 6, DH), eyelid suturing (n = 15, SUT), or no intervention (n = 4). Contralateral eyes served as the control. After 24 hours or 1 week of lens wear, 5-bromo-2-deoxyuridine (BrdU) was injected intravenously to label dividing corneal epithelial cells, and animals were killed 24 hours after injection. Corneas were stained with monoclonal anti-BrdU antibody and FITC-conjugated secondary antibody. A series of continuous digital images of the wholemounted epithelium were collected from the superior to inferior limbus, and the number of BrdU-labeled cell pairs was counted. RESULTS: SH, DH, and SUT caused a significant decrease in BrdU-labeled pairs of cells over the entire corneal epithelium at day 2 compared with the number in contralateral control eyes (P < 0.001). One week of SUT or SH caused a significant increase centrally in BrdU-labeled cells (P < 0.01). BrdU labeling at the limbus in all groups was not significantly different from the control. Unexpectedly, the proliferation rate of the control corneas was also significantly affected by contralateral lens wear and suturing. CONCLUSIONS: Short-term overnight SH, DH, and SUT all significantly suppressed the cell proliferation rate in the rabbit corneal epithelium. However, adaptation, with central hyperproliferation of cells, appeared to occur at 8 days. The effects of lens wear and eyelid suturing on the cell proliferation rate in contralateral control eyes suggests a central mechanism that regulates corneal epithelial proliferation.     

Practical experience with a high Dk lotrafilcon A fluorosilicone hydrogel extended wear contact lens in Spain.

PURPOSE: Several research studies on high Dk soft contact lens materials have been published, but little has been reported from practical clinical experience with these new materials. This study reports in-practice clinical experience with the lotrafilcon A fluorosilicone hydrogel material from a 6-month study in Spain. METHODS: Eighty-five patients were dispensed lotrafilcon A lenses (Focuse NIGHT & DAY [CIBA Vision Corporation]) for monthly replacement by 13 investigators from eight practices. The recommended wear schedule was daily wear for the first week and then up to 6-night extended wear through the first month and up to 30-night extended wear through 6 months. Follow-up visits were at 1 week, 1 month, 3 months, and 6 months. Clinical and patient subjective data were collected at each visit. RESULTS: Among patients who continued in the study at each visit, Snellen visual acuity (VA) of 20/25 or better was achieved by at least 96% of all eyes at all visits; lens surfaces assessments for front surface deposits, front surface wetting, and back surface debris averaged less than grade 1 (0-4 scale) for all lenses at all visits; biomicroscopy grades averaged well below grade 1 (0-4 scale) for all eyes at all visits; acceptable or optimal fit was assessed for 97% or more of all lenses at all visits. These patients rated the average overall comfort, vision, and handling above 9 (0-10 scale) at 6 months and 98% reported satisfaction with the lenses at 6 months. Eighty-two percent of patients dispensed completed the study. Seven patients were discontinued because of fit, and seven were discontinued because of positive biomicroscopy signs. CONCLUSIONS: The lotrafilcon A lens performed well clinically and it was accepted well by patients, with most practitioners recommending and most patients wearing it for up to 30 nights extended wear. Practitioners should be attentive to fit and discomfort complaints at dispensing and follow-up and may want to recommend lubricating or rewetting drops for those patients with dryness symptoms.     

The ocular response to extended wear of a high Dk silicone hydrogel contact lens

Purpose: A four‐month extended wear clinical trial was conducted to compare die ocular effects of a high Dk Balafilcon A silicone hydrogel lens and a low Dk HEMA 38.6 per cent H²O soft lens. Method: Twenty‐four subjects who were adapted to daily wear of soft lenses wore a high Dk lens in one eye and a low Dk HEMA lens in the other eye for four months on an extended wear basis after one week of daily wear. Thirteen progress evaluations were conducted using standard clinical procedures. Results: Eighteen subjects (75 per cent) completed the study. The high Dk lens induced significantly less bulbar and limbal injection and corneal vascularisation dian the low Dk HEMA lens (p < 0.05). Epithelial microcysts were observed only in the eyes wearing the low Dk lens. A significant increase in myopia was found in die eyes wearing die low Dk HEMA lens (mean = 0.50 D, p < 0.01) compared to die insignificant myopic increase of 0.06 D in the eyes wearing the high Dk lens. Three subjects developed small infiltrates in the high Dk lens wearing eyes and significantly more post‐lens debris was observed under the high Dk lens. Six subjects developed papillary conjunctivitis in die eye wearing silicone hydrogel lenses but only two of those were discontinued from the study. Conclusion: No hypoxia‐related effects were observed with extended wear of the high Dk Balafilcon A silicone hydrogel lens.     

配戴夜戴型角膜塑形镜两年后角膜激光共聚焦显微镜观察

目的利用激光共聚焦显微镜观察配戴夜戴型角膜塑形镜2年以上患者的角膜组织有无变化。方法回顾性病例研究。选择2009年1月至2012年12月于南京军区总院眼科就诊且配戴夜戴型角膜塑形镜2年的患者30例（60眼）作为戴镜组,未配戴任何形式角膜接触镜的角膜正常患者30例（60眼）作为对照组。对2组对象进行角膜中央部激光共聚焦显微镜观察（观察组摘镜2～3 h后）。数据采用独立样本t检验进行分析。结果配戴角膜塑形镜后角膜形态可发生明显变化,上皮至前基质层可见皱褶,上皮下神经丛疏密不均、扭曲,基质神经及内皮细胞形态正常。上皮下神经丛的分布比对照组稀疏,戴镜组的上皮细胞计数为（4818±148）cells/mm2,前基质细胞计数为（1345±154）cells/mm2,后基质细胞计数为（799±76）cells/mm2,内皮细胞计数为（3025±193）cells/mm2,与对照组相比2组差异无统计学意义。结论长期配戴夜戴型角膜塑形镜对上皮下神经丛数量及眼表形态有影响,对内皮细胞及基质细胞无明显影响。     

Histopathological analysis of the corneal epithelium after contact lens wear

Complications from contact lens wear are seldom examined histopathologically. Understanding of the epithelial reactions in response to contact lens wear would help early diagnosis and direct treatment action. Therefore, this study examines the histopathology of abrasion, epithelial edema, epithelial thinning and superficial punctate staining. Important factors in the etiology of these conditions are various definable lens and tear characteristics as well as mechanical effects from the lens. Observations on corneal innervation that have not been previously reported are used to help explain the reduced corneal sensitivity in the contact lens wearer. It is concluded that the breakdown of the epithelial surface prevents the epithelium from fulfilling its fluid and microorganism barrier functions. In addition, disturbance of the normal epithelial structure interferes with its ability to withstand further trauma and to convey the injury to the brain via the neural pathways.     

The effect of rigid gas permeable contact lens wear on proliferation of rabbit corneal and conjunctival epithelial cells.

PURPOSE: To study the effect of rigid contact lens oxygen transmissibility on cell proliferation of the corneal, limbal, and conjunctival epithelium in vivo following 2 days of extended wear in the rabbit model. METHODS: Fourteen adult New Zealand White rabbits were divided equally into two groups. Each group was assigned to one of two test rigid gas permeable (RGP) contact lenses (Dk/Ltotal = 10 and 97) with uniform thickness (0.15 mm) and diameter (14.0 mm). One eye of each rabbit randomly received a contact lens for two days (48 hrs) extended wear, and the fellow eye was used as a control. Rabbits were injected intravenously with 5-bromo-2-deoxyuridine (200 mg/kg) in sterile phosphate buffered saline (pH 7.4) 24 hours before being killed. Corneas with a limbal rim of episclera and overlying conjunctiva were fixed in situ and excised. Nuclei labeled with BrdU were detected with a monoclonal anti-BrdU antibody and an FITC-conjugated secondary antibody. Digital images were collected and BrdU-labeled nuclei of whole-mount corneas were counted from superior limbus to inferior limbus using epifluorescence microscopy. RESULTS: Twenty-four hours after intravenous injection of BrdU, labeled nuclei were confined to and appeared as pairs in the basal epithelial layer. The density of BrdU-labeled nuclei were found to be 258 +/- 42, 167 +/- 43, 372 +/- 64, and 310 +/- 46 (pairs/mm2, mean +/- SD, n = 14) in normal controls for adjacent conjunctiva, limbus, peripheral cornea, and central cornea, respectively. By contrast,there was significant 81.35% (low Dk)and 22.46% (ultra-high Dk) suppression of cell proliferation in the central cornea after two days lens wear (n = 7). In addition, significant increases in the labeling of limbal and conjunctival epithelium were also noted. CONCLUSIONS: Significantly less BrdU labeling of epithelial cells at the normal rabbit limbus was noted as compared to the peripheral and central cornea (P < 0.05) and is consistent with the presence of slow-cycling limbal basal cells and the limbal stem cell theory; however, this is the first report of up-regulation of limbal cell proliferation induced by contact lens wear. This study also revealed, for the first time, that short-term extended wear of RGP lenses inhibits central corneal epithelial cell proliferation. This effect was significantly more pronounced for a low-oxygen vs. a hyper-oxygen transmissible test lens. This data also suggests that corneal epithelial layer thinning seen following extended contact lens wear may be explained, in part, by suppression of basal epithelial cell proliferation. Further study is clearly necessary to validate and extend these preliminary findings.     

共焦显微镜评价长期配戴角膜接触镜对眼角膜组织的影响

目的应用共焦显微镜对长期配戴角膜接触镜患眼在不同时期的角膜组织的变化进行观察和分析。方法选择于大连医科大学附属一院眼科门诊进行检查的戴角膜接触镜患者47例（93眼1，年龄为17-38岁，屈光度为-1．75- 10．00D．平均日戴时间超过8h，戴镜时间为1～18年。分为三组：第一组（G1），戴镜时间5年以内者（含5年）；第二组（G2），戴镜时间5～10年者（含10年）；第三组（G3），戴镜时间10年以上者。另选择未戴角膜接触镜者15例（30眼）为第四组（G4），年龄为18～40岁，屈光度为-0．75～8．00D。共焦显微镜记录各层角膜图像,并对各层组织细胞形态、细胞密度等进行自动分析。四组间统计学分析采用单因素方差分析。结果①四组的角膜中央区Langerhans细胞密度分别为：（206．0±21．7）个/μm^2、（229．0±28．0）个／μm^2、（251．0±50．8）个／μm^2（154．0±36．7）个／μm^2。四组的角膜缘Langerhans细胞密度分别为：（308．0±76．4）个／μm^2、（364．0±53．9）个／μm^2．（417．0±83．6）个／μm^2、（254．0±127．0）个／μm^2。四组之间差异有统计学意义（P〈0．05）。②四组的角膜上皮厚度分别为：（51．2±4．5）μm、（45．6±2．7）μm、（43．5±5．0）μm、（53．6±2．5）μm。四组的前基质角膜细胞密度分别为：（1157．0±120．5）个／μm^2、（1094．0±103．0）个／μm^2、（1011．0±197．8）个／μm^2、（1187．0±139．0）个／μm^2。四组之间差异有统计学意义（P〈0．05）③四组的多形性内皮细胞百分比分别为：（36．2±1．7）％、（33．7±1．7）％、（32．8±1．5）％、（45．1±9．1）％四组的内皮细胞异形性百分比分别为：（56．5±3.4）％、（63．3±3．7）％、（64．2±7．11％、（45．8±12．2）％四组之间差异有统计学意义（P〈0．05）④四组的角膜全层厚度、后?