Tear secretion induced by selective stimulation of corneal and conjunctival sensory nerve fibers

PURPOSE: To measure the increase in tear secretion evoked by selective stimulation of the different populations of sensory receptors of the cornea and conjunctiva by using moderate and intense mechanical, chemical, and cold stimuli. METHODS: Six healthy subjects participated in the study. Tear secretion was measured in both eyes by the Schirmer's test conducted under control conditions and after stimulation of the center of the cornea and the temporal conjunctiva with a gas esthesiometer. Mechanical stimulation consisted in three pulses of 3 seconds' duration of warmed air (at 34 degrees C on the eye surface) applied at moderate (170 mL/min) and high (260 mL/min) flow rates. Cold thermal stimulation was made with cooled air that produced a corneal temperature drop of -1 degrees C or -4.5 degrees C. Chemical (acidic) stimulation was performed with a jet of gas containing a mixture of 80% CO(2) in air. RESULTS: The basal volume of tear secretion increased significantly (P < 0.05, paired t-test) after stimulation of the cornea with high-flow mechanical stimuli (260 mL/min), intense cooling pulses (-4.5 degrees C), and chemical stimulation (80% CO(2)). The same stimuli were ineffective when applied to the conjunctiva. Moderate mechanical (170 mL/min) and cold (-1 degrees C) stimulation of the cornea or the conjunctiva did not change significantly the volume of tear secretion. CONCLUSIONS: Reflex tear secretion caused by corneal stimulation seems to be chiefly due to activation of corneal polymodal nociceptors, whereas selective excitation of corneal mechanonociceptors or cold receptors appears to be less effective in evoking an augmented lacrimal secretion. Conjunctival receptors stimulated at equivalent levels do not evoke an increased tear secretion.     

Nociceptive sensation and sensitivity evoked from human cornea and conjunctiva stimulated by CO2

PURPOSE: To compare sensation and sensitivity evoked from human cornea and conjunctiva stimulated by CO2. METHODS: Twenty healthy participants were recruited for the study. Central corneal and temporal conjunctival chemical sensation and sensitivity of only one eye of each subject were evaluated. Air mixed with different concentrations of CO(2) was delivered by a modified Belmonte pneumatic esthesiometer. The ascending method of limits was used to determine the sensitivity and subjects were required to characterize the sensation at threshold. RESULTS: The sensations evoked by CO(2) in the cornea and conjunctiva were stinging or burning. The sensation evoked by mechanical stimulation was that of irritation. The corneal and conjunctival chemical thresholds were 31% +/- 2% and 54% +/- 5% CO(2) (mean +/- SE), respectively. The corneal and conjunctival mechanical thresholds were 80 +/- 6 and 140 +/- 10 mL/min (mean +/- SE), respectively. The corneal sensitivity was significantly higher for both mechanical and chemical stimuli (P < 0.05). CONCLUSIONS: The results suggest that CO(2) stimulates similar corneal and conjunctival nociceptors in that the interpretations were the same (i.e., nociceptive). The central cornea had a higher sensitivity to CO(2) than the temporal conjunctiva, which may reflect a different peripheral innervation, such as different nerve density or different receptor characteristics. Sensations evoked by mechanical and chemical stimulation were different, which suggests that at the peripheral level, the two modalities stimulate two different kinds of molecular receptors or channels and that this information is somehow retained within the nociceptive system.     

The association between eye color and corneal sensitivity measured using a Belmonte esthesiometer.

PURPOSE: The purpose of this study is to determine the association between corneal sensitivity measured using a pneumatic esthesiometer and eye color quantified objectively. METHODS: Twenty subjects had ocular surface sensitivity measured using a Belmonte esthesiometer. An ascending method of limits followed by the method of constant stimuli were used to estimate 1) cold detection thresholds, 2) discomfort detection thresholds (both using pneumatic stimuli at 20 degrees C, 3) mechanical detection thresholds using pneumatic stimuli at 50 degrees C (ocular surface temperature approximately 33 degrees C), and 4) percent CO2 chemical detection thresholds using 50 degrees C pneumatic stimuli at flow rates set at half of each subject's pneumatic detection threshold (therefore detected by the chemical content and not the mechanical content). Eye color was estimated 1) clinically by two observers ranking the color (light to dark) of digital images of each subject's iris, 2) photometrically by measuring iris luminance, and 3) using chromaticity obtained from a Photo Research 650 spectroradiometer with controlled illumination. Correlation and linear and nonlinear regression analyses were used to examine relationships between variables. RESULTS: There were no associations between eye color (determined clinically or objectively) for mechanical and chemical detection thresholds (best r = 0.15, all p > 0.05). There was a significant linear association between 20 degrees detection thresholds and eye color (r = 0.39), which was substantially improved with a two-line function (part level and part increasing linearly, r = 0.65). CONCLUSIONS: We were generally unable to demonstrate the relationship between eye color and sensitivity reported previously using a Cochet-Bonnet esthesiometer. However, for a subset of subjects with palest irises, there appears to be a linear association between eye color and sensitivity to cooling stimuli.     

Decreased corneal sensitivity in patients with dry eye

PURPOSE: To explore changes in corneal sensitivity that develop in patients with dry eye and the relationship between sensibility and severity of the dry eye disease. METHODS: Experiments were performed in 44 patients with dry eye and 42 healthy individuals. Corneal sensitivity was measured with the Belmonte noncontact gas esthesiometer. Mechanical (air jets at flow rates from 0 to 200 mL/min, reaching the corneal surface at 34 degrees C), thermal (cold or warm air at subthreshold flow rates changing corneal basal temperature +/-1 degrees C), and chemical stimuli (air containing 0% to 50% CO2 at subthreshold flow rate and temperature at the cornea of 34 degrees C) were applied to the center of the cornea to determine the sensitivity threshold for each stimulus modality. The clinical state of the ocular surface was also explored, measuring the fluorescein tear break-up time, the degree of corneal staining with fluorescein and Lissamine green, and tear production with the Schirmer test. RESULTS: Both in control subjects and patients with dry eye, the corneal thresholds for mechanical, chemical, and thermal stimulation increased with age. Moreover, the thresholds for the three modalities of stimuli were significantly higher in patients with dry eye than in control subjects. In both groups, individual mechanical, chemical, and thermal thresholds correlated significantly. Also, high thresholds in patients with dry eye correlated with the intensity of fluorescein and Lissamine green corneal staining but not with the results of the Schirmer test. CONCLUSIONS: Patients with dry eye exhibit corneal hypoesthesia after mechanical, thermal, and chemical stimulation that appears to be related to damage to the corneal sensory innervation.     

Eccentric variation of corneal sensitivity to pneumatic stimulation at different temperatures and with CO2

The purpose was to measure corneal sensitivity at multiple corneal positions using pneumatic stimuli, at room temperature and at ocular surface temperature (with and without CO(2) added), in 15 healthy participants. Sensitivity of central, mid-peripheral, and peripheral cornea was measured using a computer-controlled modified Belmonte esthesiometer to deliver pneumatic cool (air at 20 degrees C), mechanical (air at 50 degrees C), and chemical stimuli (air at 50 degrees C with CO(2) added). The ascending method of limits and method of constant stimuli were adopted to determine the threshold to these stimuli at each location. Sensitivity across the cornea using pneumatic stimuli at different temperatures and chemical stimuli varied only slightly. These patterns of variation are different to what has been previously reported using Cochet-Bonnet esthesiometry.     

The inhibitory interaction between human corneal and conjunctival sensory channels

PURPOSE: To explore human corneal and conjunctival sensory channels at suprathreshold level. METHODS: Ten healthy human subjects participated in the study. The Belmonte pneumatic esthesiometer was used to apply mechanical and chemical stimuli to the central cornea and temporal conjunctiva of the left eye. Stimuli were applied in a paired and unpaired way for conjunctival stimulation. A 100-point visual analog scale (VAS) was used to rate the intensity of the stimulus. RESULTS: The magnitudes of the sensation evoked from the conjunctiva were different when using different methods for presenting stimuli to the ocular surface. When stimuli were applied to the conjunctiva alone, the magnitude of the sensation was stronger than when the stimuli were applied in pairs to the cornea and conjunctiva for both mechanical (P = 0.04) and chemical (P = 0.02) stimulation. CONCLUSIONS: The relatively strong discomfort evoked from the cornea appears to suppress partially the relatively weaker conjunctival stimulation. This manifested as the conjunctival sensory transducer function being shallower (less intense sensation) when immediately preceded by corneal stimulation than when the conjunctival sensory transducer functions were measured alone (unpaired). The underlying mechanism could be adaptation or some other inhibitory effect, such as diffuse noxious inhibitory control. At some level therefore, corneal and conjunctival sensory channels are not independent.     

Neural basis of sensation in intact and injured corneas

A renewed interest in the characteristics and neural basis of corneal and conjunctival sensations is developing in recent years due to the high incidence of discomfort and altered sensitivity of the cornea following refractive surgery, use of contact lenses and dry eyes. Corneal nerves are functionally heterogeneous: about 20% respond exclusively to noxious mechanical forces (mechano-nociceptors); 70% are additionally excited by extreme temperatures, exogenous irritant chemicals and endogenous inflammatory mediators (polymodal nociceptors), and 10% are cold-sensitive and increase their discharge with moderate cooling of the cornea (cold receptors). Each of these types of sensory fibres contributes distinctly to corneal sensations. Mechano-nociceptors mediate, sharp acute pain produced by touching of the cornea. Polymodal nociceptors elicit the sustained irritation and pain that accompany corneal wounding; cold receptors evoke cooling sensations. Depending on the relative activation by the stimulus of each subpopulation of corneal sensory fibres, different subqualities of irritation and pain sensations are evoked. Corneal sensations can be explored experimentally in humans with a gas esthesiometer that applies controlled mechanical, chemical and thermal stimuli to the corneal surface. When the cornea is wounded, corneal nerves are excited and eventually severed in a variable degree and local inflammation is produced. Activated corneal nerves release neuropeptides (SP, CGRP) that contribute to the inflammatory reaction (neurogenic inflammation). They also become sensitized by local inflammatory mediators, such as prostaglandins or bradykinin and thus exhibit spontaneous activity, lowered threshold and enhanced responses to new stimuli. This leads to spontaneous pain and hyperalgesia. Nerves destroyed by injury soon start to regenerate and form microneuromas that exhibit abnormal responsiveness and spontaneous discharges, due to an altered expression of ion channel proteins in the soma and in regenerating nerve terminals. Presumably, this altered excitability is the origin of the lowered sensitivity and the spontaneous pain, dry eye sensations and other disaesthesias reported in patients following refractive surgery.     

Recovery of corneal sensitivity to mechanical and chemical stimulation after laser in situ keratomileusis

PURPOSE: To evaluate the time course of changes in corneal sensitivity to mechanical and chemical stimuli produced by laser in situ keratomileusis (LASIK) in humans. METHODS: We performed a cross-sectional study of 17 LASIK-operated eyes (VisX S2, equipped with version 2.50-3.10 software) and 15 control eyes of 17 individuals to evaluate regeneration of corneal sensitivity after LASIK. Gas pulses of variable flow and compositions were applied to the cornea by a non-contact gas esthesiometer. Mechanical stimuli consisted of air puffs at flows from 0 to 200 ml/min. Chemical stimulation was made with gas pulses containing 0% to 80% CO2 in air at subthreshold flow. Mechanical and chemical thresholds and intensity-response curves for the evoked sensations were determined prior to surgery, and 7 to 9 days, 3 to 5 months, and 1.5 to 2.5 years after surgery. RESULTS: Corneal sensitivity to mechanical stimulation was enhanced 7 to 9 days after surgery but subsequently dropped markedly and remained significantly below control levels 3 to 5 months after LASIK. Sensitivity to both mechanical and chemical types of stimuli was close to normal 2 years postoperatively. CONCLUSIONS: Corneal sensitivity decreased immediately after LASIK but mechanical sensitivity showed a transient hyperesthesia 7 to 9 days afterward. Subsequently, a long-lasting and deep hypoesthesia to mechanical and chemical stimuli was observed. Gas esthesiometry revealed that disturbances of corneal sensation still exist at times when coarse mechanical sensitivity appeared to be normal.     

Sensations evoked by selective mechanical, chemical, and thermal stimulation of the conjunctiva and cornea

PURPOSE: To study the sensations evoked by selective mechanical, chemical, and thermal stimulation of the conjunctiva and compare them with those elicited by similar stimulation of the cornea. METHODS: Six young subjects participated in the study. Using a gas esthesiometer, selective mechanical (air puffs at flows from 0 to 264 ml/min), chemical (0--80% CO(2) in air), and thermal (air at temperatures from -10 degrees C to +80 degrees C) stimulation was performed on the center of the cornea and on the temporal conjunctiva. The intensity, degree of irritation, stinging and burning pain components, and thermal characteristics of the evoked sensation were evaluated after each stimulus in separate, 10-cm continuous visual analogue scales (VASs). The ability of the subjects to identify the quality of the stimulus applied to the cornea and the conjunctiva was also studied. RESULTS: The subjective intensity and thermal components (cooling or warming) of the sensation reported after mechanical, chemical, and heat stimulation were similar in the conjunctiva and cornea, although lower VAS scores were always reported in the conjunctiva for the irritation and the stinging and burning pain components. In the cornea, stimulation with low temperatures was perceived as a cooling sensation with an irritative component. In the conjunctiva, cooling was perceived as a purely cold sensation. Subjects showed similar discrimination capability in the cornea and the conjunctiva for the various types of stimuli. CONCLUSIONS: Sensations evoked in the cornea by selective mechanical, chemical, and heat and cold stimulation always presented an irritation component. In the conjunctiva, stimuli of the same intensity are always perceived as less irritating than in the cornea. Cold and other non-noxious subqualities of sensation can be evoked in the conjunctiva.     

Dystrophia Helsinglandica – corneal morphology,topography and sensitivity in a hereditary corneal disease with recurrent erosive episodes

Purpose: The aim of this study was to describe the morphology, corneal topography and sensitivity in individuals with Dystrophia Helsinglandica. This autosomal dominant corneal disease is characterized by recurrent corneal erosive episodes and progressive subepithelial fibrosis not significantly affecting visual acuity. Methods: The corneas of nine affected and nine unaffected individuals were examined using slit‐lamp biomicroscopy, in vivo confocal microscopy (IVCM) and videokeratography. Corneal mechanical sensitivity was also measured using a non‐contact esthesiometer. Results: Slit‐lamp biomicroscopy revealed that the affected individuals represented different stages of corneal changes, from a nearly normal cornea to subepithelial fibrosis of the central cornea. Corneal changes in affected individuals did not significantly decrease the best spectacle‐corrected visual acuity. In vivo confocal microscopy detected morphological changes in the epithelium and stroma. Subepithelial opacity formation including altered keratocytes could be found in the anterior stroma in all affected eyes. With the exception of two eyes (one affected and one unaffected), all videokeratographies showed irregular astigmatism. Corneal sensitivity was significantly lower in affected individuals (p = 0.01). Age and corneal sensitivity showed no correlation. Conclusion: The main morphological findings in affected individuals were discrete and progressive subepithelial fibrosis, in the in vivo confocal microscope corresponding to optically dense extracellular matrix and activated keratocytes. Subbasal nerve morphology was changed in the affected family members who also showed a decreased corneal sensitivity. The findings are per se not specific to the disease. The changes probably reflect a healing response to erosive events on the corneal surface influenced by the genotype.     

Changes in mechanical, chemical, and thermal sensitivity of the cornea after topical application of nonsteroidal anti-inflammatory drugs

PURPOSE: In addition to their well-known anti-inflammatory actions, some of the nonsteroidal anti-inflammatory drugs (NSAIDs) appear to have an analgesic effect. In human subjects, the changes in threshold and intensity of sensations evoked by mechanical, chemical, and thermal stimulation of the cornea induced by topical administration of two commercial NSAIDs, diclofenac sodium (Voltaren; Novartis, Basel, Switzerland) and flurbiprofen (Ocuflur; Allergan, Irvine, CA), were studied. METHODS: Corneal sensitivity was measured in 10 young, healthy subjects with a gas esthesiometer. Chemical (10%-70% CO2 in air), mechanical (0-264 mL/min), and thermal (corneal temperature changes between -4.5 degrees C and +3 degrees C around the normal value) stimuli were applied to the center of the cornea. The intensity and perceived magnitude of the psychophysical attributes of the evoked sensation were scored at the end of the pulse in a 10-cm, continuous visual analog scale (VAS). The threshold was expressed as the stimulus intensity that evoked a VAS score >0.5. Sensitivity was measured in both eyes of each subject on two separate days, one without treatment and the other 30 minutes after topical application of 0.03% flurbiprofen (seven subjects) or 0.1% diclofenac sodium (six subjects). RESULTS: Diclofenac attenuated significantly all the sensation parameters evoked by high-intensity mechanical, chemical, and thermal stimuli. Flurbiprofen produced a slight reduction of the sensations evoked by mechanical and chemical stimulation that became significant only for the irritation caused by chemical stimuli of maximum intensity (70% CO2). None of the drugs modified significantly the detection threshold of the different stimuli. CONCLUSIONS: Flurbiprofen had a very limited effect on sensations evoked by corneal stimulation, whereas diclofenac reduced the intensity of sensations evoked by stimuli of different modality, suggesting a mild local anesthetic effect of this drug on all types of corneal sensory fibers. Such anesthetic action could explain the analgesic effect that has been reported after topical application of diclofenac in inflamed human eyes.     

带蒂结膜瓣移植术在角膜溃疡治疗中的应用研究

目的探讨带蒂结膜瓣移植治疗角膜溃疡的临床效果。方法对56例药物治疗无效的难治性角膜溃疡行病灶清除及带蒂结膜瓣移植术,合并穿孔者行带眼球筋膜囊的改良带蒂结膜瓣移植术,术后针对原发病进行药物治疗。结果 53例1次手术治愈角膜溃疡,达到了保存眼球的目的。3例术后结膜瓣脱落,反复行结膜瓣遮盖术2～3次,但最终角膜融解。结论对于药物治疗无效的难治性角膜溃疡,带蒂结膜瓣移植术仍是有效的治疗方法,尤其是对角膜穿孔者,可以控制炎症,保存眼球,并为进一步行角膜移植术创造条件。     

大鼠角膜化学伤后PEDF和VEGF的不平衡表达

目的比较硝酸银化学伤后大鼠角膜和正常角膜色素上皮衍生因子（PEDF）和血管内皮生长因子（VEGF）表达水平，揭示两者与角膜新生血管的相关性。方法10只大鼠左眼角膜硝酸银化学伤后为实验组，右眼为正常对照组，伤后15d行免疫组织化学法定位及Western blot定量检测样本角膜PEDF、VEGF等的表达。结果免疫组织化学检查：实验组角膜VEGF、碱性成纤维细胞生长因子（bFGF）强表达，PEDF未见表达或弱表达。正常组角膜PEDF高表达，VEGF弱表达，bFGF几乎不表达。Western Blot分析：实验组角膜PEDF表达明显下降（t=8．0049，P〈0．01），VEGF表达显著升高（t=48．3637，P〈0．01）。结论角膜严重化学伤后新生血管抑制因子PEDF破坏，刺激因子VEGF产生增加，PEDF／VEGF比值降低，角膜血管新生。     

How long does the recovery of corneal sensitivity in different corneal regions take after LASEK?

AIM: To determine the corneal sensitivity recovery period after laser-assisted sub-epithelial keratectomy (LASEK) refractive surgery and investigate the effects of ablation depth on it. METHODS: In this study examinations were performed on 90 right eyes of 90 people (34 males and 56 females) with an age range of 20-35 and an average of 22.26±3.8 years old. A sensation of 5 corneal regions, including the center and 4 mid-peripheral regions, i.e., nasal, inferior, temporal, and superior, each at a distance of 2 mm from the center of the cornea were measured with a Cochet-Bonnet esthesiometer device in 3-time points including before LASEK, 1 and 3mo after the surgery, respectively. LASEK was performed on individuals with stabilized myopia of -1.00 to -7.00 diopters and astigmatism of less than 2.00 diopters. Furthermore, the individuals were divided into three groups regarding ablation depth. RESULTS: The highest level of corneal sensitivity before surgery was related to the center of the cornea (59.1±7.76), and the highest level of corneal sensitivity loss was also related to this region. The sensation of all measured corneal regions significantly reduced 1mo postoperatively and returned to their preoperative levels 3mo after surgery (mean of 5 corneal regions in levels of preoperation: 58.2±6.48, 1mo postoperation: 57.3±5.84, 3mo postoperation: 58.2±5.49; P<0.05). A significant relationship was found between ablation depth and corneal sensitivity changes in the center and temporal regions (P<0.05). CONCLUSION: Corneal sensitivity in myopia and low astigmatism decreases after LASEK and reaches the preoperative level within 3mo. The depth of ablation during surgery affected the recovery of corneal sensitivity.     

甘油保存角膜材料行深板层角膜移植术后临床和共焦显微镜观察

目的 观察甘油保存角膜材料行深板层角膜移植术后临床和共焦显微镜活体组织学改变.方法 2008年1月至2011年5月在我院行深板层角膜移植治疗的患者26例（26只眼）,所有患者植片均选择甘油脱水低温保存角膜材料,术后裂隙灯观察角膜植片愈合和透明情况,Cochet-Bonnet角膜知觉计测量角膜中央知觉值,共焦显微镜观察角膜全层组织的活体改变.结果 （1）裂隙灯观察26例患者均于术后1~3个月上皮完全修复,角膜植片透明,术后2例发生基质排异反应.（2）术后3个月可不同程度检测到角膜中央知觉,术后3个月角膜中央知觉平均阈值（18.35±9.56）mm,12个月（51.62±6.48）mm.（3）共焦显微镜观察术后1~3个月上皮细胞密度达正常值,3个月内未观察到角膜基质细胞,6~12个月基质细胞密度增加,术后6个月可观察到基质内神经干细胞,角膜内皮细胞密度维持稳定,但在两例发生基质排异反应患者出现内皮细胞密度明显下降.结论共焦显微镜在组织学上证明甘油保存角膜材料行深板层角膜移植后可在一定程度上恢复正常生理结构,并与临床观察角膜愈合过程相吻合.     

水囊法超声生物显微镜对儿童先天性角膜混浊影像学特点的分析

目的借助水囊法超声生物显微镜检查探讨儿童先天性角膜混浊的影像学特点。方法回顾性分析先天性角膜混浊患儿142例(181眼),观察先天性角膜混浊的眼前节发育情况,根据发育异常的表型分为A、B、C、D四型。结果 181眼中有A型43眼(23.8%),仅前部角膜混浊不伴有其他结构异常。B型11眼(6.1%)为后部或全层角膜混浊,伴角膜后部局部缺损,而虹膜晶状体正常。C型88眼(48.6%)为虹膜或房角发育异常,但晶状体未见异常,其中房角发育异常范围小于4个方位的C1型共35眼(19.3%);房角发育异常范围大于等于4个方位的C2型共53眼(29.3%)。D型39眼(21.5%)为角膜虹膜与晶状体粘连,或存在混浊、膜样、缺如等晶状体异常。双眼混浊患者两眼表现可不对称;同时伴有晶状体和虹膜异常的比例,双眼混浊(32.1%)显著多于单眼(13.6%)(χ2=8.947,P=0.003)。结论采用水囊包裹探头的超声生物显微镜是适合于儿童的眼前节检查方法,可用于分析先天性角膜混浊角膜、虹膜、房角和晶状体的影像学特点并分型,对明确其诊断和预后具有指导意义。     

RGP镜片对儿童角膜敏感性的影响

目的:研究儿童配戴RGP镜片后角膜敏感性的变化.方法:采用问卷的形式收集基本信息,应用Cochet and Bonnet aesthesiometer测量67例134眼角膜敏感性,按照不同分组进行比较分析.结果:儿童戴镜1～12mo组,戴镜1～5a组中央部和下方角膜敏感性明显下降(中央P=0.000,下方P=0.002),而2组之间的差异无显著意义(中央P=0.997,下方P=0.056).儿童戴镜1～5a组颞侧,鼻侧,上方角膜敏感性明显下降(颞侧P=0.000,鼻侧P=0.000,上方P=0.001),戴镜1～5a组与戴镜1～12mo组(颞侧P=0.133,鼻侧P=0.125,上方P=O.205),未戴镜组与戴镜1～12mo组(颞侧P=0.06,鼻侧P=0.200,上方P=0.207),差异均无显著意义.儿童与成年人分别配戴RGP镜片1～12mo和1～5a,中央角膜敏感性无显著差异(1～12mo.P=0.343,1～5aP=0.105).结论:RGP镜片对于儿童和成人的中央角膜敏感性的影响是相似的.但由于儿童自身的特点,为儿童验配RGP仍应慎重.     

Characteristics of human corneal psychophysical channels

PURPOSE: To characterize human corneal psychophysical channels. METHODS: Twenty subjects participated in this study. A Belmonte pneumatic esthesiometer was used to deliver stimuli, and the ascending method of limits and the method of constant stimuli were used to estimate thresholds. Sensation was characterized for different stimuli. Corneal mechanical and chemical thresholds were measured at different temperatures. RESULTS: The qualities of the sensations induced by stimuli with different temperatures were different, and the corresponding detection thresholds of the pneumatic stimuli at four temperatures gradually increased (repeated measures ANOVA (F(3,12) = 10.326, P = 0.000). There were no temperature effects on chemical thresholds (repeated measures ANOVA F(3,12) = 0.235, P = 0.870) or mechanical discomfort thresholds from 20 degrees C to 50 degrees C (paired t14 = -0.233, P = 0.818). There were strong interactions when chemical and mechanical stimuli were added. Chemical thresholds were progressively lower when the flow rate increased and mechanical thresholds went down as the percentage of added CO2 increased (repeated measures ANOVA F(3, 12) = 6.407, P = 0.007, F(4, 16) = 19.904, P = 0.000). CONCLUSIONS: This study suggests that humans sense corneal non-noxious cold and noxious mechanical and chemical stimuli, and that the sensitivity of some submodalities can be modulated by others. There are at least five psychophysical channels (non-noxious cold, noxious mechanical, noxious chemical-H+, noxious heat, and itching) processing corneal sensory information. Both decreased corneal chemical thresholds at high flow rates and decreased mechanical thresholds with an added chemical stimulation demonstrate that corneal psychophysical channels are not independent.     

不同年龄段马凡综合征晶状体不全脱位患者角膜特征及意义

目的 比较不同年龄段马凡综合征晶状体不全脱位患者的角膜特征并探讨其临床意义.方法 马凡综合征组45例84眼和对照组84例84眼列入研究,前者按年龄分为两组:儿童组(5 ～14岁)49眼和非儿童组(＞14岁)35眼.使用Pentacam测量角膜曲率、角膜散光和中央角膜厚度.结果 与对照组相比,马凡综合征组患者角膜变平、散光增大,两组间差异均具有统计学意义(均为P =0.000).马凡综合征患者角膜前表面曲率儿童组为(40.02±1.42)D,非儿童组为(41.03±1.57)D;角膜后表面曲率儿童组为(-5.71±0.23)D,非儿童组为(-5.89±0.31)D;总角膜散光儿童组为(-1.71±0.84)D,非儿童组为(-1.34 ±0.78)D,两组相比差异均具有统计学意义(均为P＜0.05).角膜前表面散光儿童组高于非儿童组(P=0.017),而后表面散光两组间差异无统计学意义(P =0.377).儿童组总角膜散光和角膜前表面散光以顺规散光(69.39％)为主,而非儿童组顺规散光和斜向散光的比例相当.两组角膜后表面都以逆规散光为主(儿童组占85.71％,非儿童组占77.14％).以角膜前表面散光估计总角膜散光时约有一半的患者会高估约0.32 D.结论 马凡综合征晶状体不全脱位患者角膜变平、散光增大.儿童组角膜更扁平,总角膜散光和角膜前表面散光值较高,以顺规散光为主.马凡综合征患者的角膜后表面散光值较稳定,以逆规散光为主.忽视角膜后表面散光,以角膜前表面散光值估计总角膜散光时易高估.     

眼前节光学相干断层扫描对角膜裂伤缝合术后早期角膜伤口的形态学分析

目的　利用眼前节光学相干断层扫描（ａｎｔｅｒｉｏｒｓｅｇｍｅｎｔｏｐｔｉｃａｌｃｏｈｅｒｅｎｃｅｔｏｍｏｇｒａｐｈｙ,ＡＳ-ＯＣＴ）技术分析角膜裂伤缝合术后早期角膜伤口形态学的特点。方法　选取１９６例（１９６眼）角膜裂伤患者,于角膜裂伤缝合术后第１天,运用ＡＳ-ＯＣＴ分析角膜伤口对合情况,测量角膜厚度,同时观察患者对侧眼相应部位角膜厚度情况,以作对比。结果　术后所有患者裂隙灯下检查角膜伤口均闭合良好,无渗漏。根据ＡＳ-ＯＣＴ的表现,患者角膜伤口形态分为４型,其中２７眼（１３．７８％）为Ⅰ型对合良好;１２３眼（６２．７６％）为Ⅱ型错位对合;４１眼（２０．９２％）为Ⅲ型内口哆开;５眼（２．５５％）为Ⅳ型虹膜前粘连。４种类型中,患眼伤口处最大角膜厚度平均值均明显大于对侧眼相应部位角膜厚度平均值,差异均具有统计学意义（均为Ｐ＜０．０５）;４种类型中患眼与对侧眼角膜厚度差值的组间比较,差异无统计学意义（Ｐ＝０．３８３）。结论　角膜裂伤缝合术后早期角膜伤口形态差异大,ＡＳ-ＯＣＴ可精确观察、定量分析角膜伤口形态。