Cochet-Bonnet Esthesiometer Research Articles

Sensory Changes in Periocular Skin After Upper Eyelid Surgery.

The aim of this interventional, prospective study is to estimate the change in periocular cutaneous sensation after upper eyelid surgery. The trial included 48 eyes of 24 patients undergoing upper eyelid blepharoplasty or upper eyelid blepharoplasty and blepharoptosis repair. Eyelid sensation was measured using a Cochet-Bonnet filament-type esthesiometer at 4 predetermined anatomical locations in the upper eyelid. The mean esthesiometry reading was calculated at the preoperative visit (4.06 cm), at 2-week postoperative visit (4.38 cm), and at final postoperative visit (4.52 cm). Paired t test showed no significant difference in sensation measurement at second visit compared with baseline (P = 0.205) or at final visit compared with baseline (P = 0.092). Paired t test showed no correlation between type of surgery and change in sensation. Sex and age did not influence change in sensation. In 40 of 42 eyelids, (95.24%), patients reported no reduction in subjective eyelid sensation. The authors conclude that eyelid sensation was not compromised objectively or subjectively by upper eyelid skin incision surgery. Surgeons can reassure patients contemplating surgery that it is very unlikely that cutaneous sensation will be damaged.

Patterns of Altered Corneal Sensation in Patients With Chronic Migraine.

Migraine is a central sensitization disease characterized by recurrent unilateral headache. The aim of this study was to evaluate corneal sensitivity and associated findings in patients with migraine. In this study, we included 58 patients with migraine (52 female and 6 male, mean age: 32.98±8.51 years) and 30 healthy control subjects (27 females and 3 males, mean age: 35.29±8.00 years). Only patients who did not have any eye disease were included in this study. Corneal sensation was evaluated with Cochet-Bonnet esthesiometer in five different regions of the cornea. There was no significant difference between the groups for age, sex, and visual acuity. Increased mean sensitivity of the nasal cornea in the patients with migraine was found (55.0 vs. 53.75 mm, P=0.020). There was no significant difference in mean sensitivity for central (57.5 vs. 55 mm, P=0.163), temporal (57.5 vs. 55 mm, P=0.066), superior (52.5 vs. 52.5 mm, P=0.551), and inferior cornea (48.75 vs. 47.5 mm, P=0.818), or mean overall sensation (54.0 vs. 52.75, P=0.14), although there was a trend toward increased sensitivity in the patients with migraine. Among the subgroup of patients with unilateral migraine, mean overall sensation (54.0 vs. 53.0 mm, P=0.049) and temporal sensation (57.5 vs. 55.0 mm, P=0.043) were increased on the affected side. In this study, we have demonstrated that patients with migraine have increased corneal sensation, especially in the cornea of the affected side. This finding supports the idea that corneal sensation is altered in patients with migraine.

The effect of cold tetracaine on the severity of burning sensation upon instillation.

PurposeTetracaine is one of the most common eye drops that are used for analgesia in clinical practice. However, it causes ocular burning sensation when instilled. This study aimed to compare the effects of the cold and room temperature tetracaine on burning sensation.Patients and methodsWe conducted a prospective, double-blinded, randomized controlled trial at the ophthalmology outpatient clinic, Phramongkutklao Hospital during January 2016–February 2017. In this study, 424 consecutive patients (those with a history of keratopathy or neuropathy were excluded) who received dilated fundus examination were randomized to receive cold tetracaine (4°C) in one eye and room temperature tetracaine (22.5°C) in the other eye. Each patient was asked to answer the questionnaire on the severity of burning sensation using 100 mm visual analog scale.ResultsPatients reported less burning sensation on the eye that received cold tetracaine (visual analog scale 20.50±18.8 vs 22.70±20 mm; P=0.025). In the subgroup analysis, young patients (≤40 years old), female subjects, patients who received tetracaine for the first-time and those who had no previous ocular surgery reported more benefit from cold tetracaine. The subgroup of patients who had normal corneal sensation, identified by using a Cochet–Bonnet esthesiometer, also showed greater benefit from cold tetracaine compared to those with impaired corneal sensation.ConclusionCold tetracaine caused less burning sensation than room temperature solution. Its benefit was greater in the subgroup of patients who reported more severe burning sensation. We recommend using cold tetracaine in routine practice, especially in those who are anticipated to have this common side effect.

An in vivo confocal microscopy study of corneal changes in pseudoexfoliation syndrome.

To evaluate, through the in vivo confocal microscopy, the pathological changes of each corneal layer in eyes affected by pseudoexfoliation syndrome. We studied 40 eyes of 40 patients with diagnosis of unilateral senile cataract associated with pseudoexfoliation syndrome and 40 eyes of 40 control subjects with senile cataract without pseudoexfoliation syndrome. All patients underwent a complete ophthalmic examination including best corrected visual acuity, slit-lamp examination, corneal sensitivity measurement using a Cochet-Bonnet nylon thread esthesiometer, and anterior segment optical coherence tomography (Visante OCT, Carl Zeiss Meditec AG, Germany); in vivo confocal microscopy of corneal sections (endothelium, stroma, sub-basal nerve plexus, and superficial and basal epithelium) was performed with the ConfoScan 4.0 (Nidek, Japan). In pseudoexfoliation syndrome group, the mean corneal sensitivity was 44.1 ± 1.3 mm and in the control group was 55.6 ± 4.7 mm. The corneas of the eyes with pseudoexfoliation syndrome were significantly less sensitive than those of control group eyes (p < 0.001). Pseudoexfoliation syndrome eyes had a lower nerve density and less nerve beadings and a higher degree of tortuosity in sub-basal plexus compared to the control group. The cell density of epithelial and endothelial layers was significantly lower in pseudoexfoliation syndrome eyes than controls. In 80% of pseudoexfoliation syndrome eyes, we found activated keratocytes and inflammatory cells in the anterior stroma. Our study demonstrates the morpho-structural corneal alterations in eyes affected by pseudoexfoliation syndrome, using corneal in vivo confocal microscopy as a non-invasive and high-reproducible technique to evaluate pathophysiology of each corneal layer; the sub-basal nerve plexus alterations are correlated with the lower corneal sensitivity.

Evaluation of the effects of isotretinoin for treatment of acne on corneal sensitivity

PurposeTo determine the effect of isotretinoin on corneal sensitivity in acne patients. MethodsFifty patients (13 men and 37 women) with a mean age of 23.24 ± 3.4 years were selected among patients receiving isotretinoin (1.0 mg/kg) for acne according to inclusion criteria. The Cochet-Bonnet esthesiometer was used to measure corneal sensitivity (in mm filament length) two times (the measurements were done immediately before starting the medication, then 3 months after that), including 3 measurements each time, between 11 a.m. and 1 p.m. by an experienced operator. The average of the 3 measurements in each time was recorded as the final value. One-way analysis of variance and Chi square were used for quantitative and qualitative comparison of corneal sensitivity before and after isotretinoin use, respectively. ResultsThe mean corneal sensitivity was 5.54 ± 0.05 before medication consumption which decreased to 5.41 ± 0.05 after isotretinoin treatment for 3 months (P < 0.005). After controlling the effect of age and sex, the decrease of corneal sensitivity was markedly significant (P = 0.003) as decreased corneal sensitivity was more pronounced at higher ages and in female gender. In non-parametric evaluation, corneal sensitivity was categorized as substantial (5.5–6 mm), intermediate (4.5–5.5 mm), and low (3.5–4.5). About 72% of the participants had substantial corneal sensitivity before drug consumption, which decreased to 60% after 3 months of treatment. ConclusionsAccording to the results of this study, corneal sensitivity decreases after three months of treatment with isotretinoin. This decrease is more pronounced at higher ages and in women.

Corneal hyperalgesia in patients with short tear film break-up time dry eye

PurposeTo evaluate corneal tactile and pain sensations in patients with short tear film break-up time dry eye (sBUT DE). MethodsThis study enrolled 60 patients with sBUT DE and 46 healthy volunteers from Japan. We evaluated corneal tactile and pain sensations using a modified method with the Cochet-Bonnet corneal esthesiometer. ResultsPatients with sBUT DE had higher corneal pain sensitivity (26.3 ± 23.1 mm) than healthy subjects (6.9 ± 16.4 mm), but similar corneal tactile sensation (52.0 ± 15.5 mm and 52.9 ± 14.9 mm, respectively). In patients with sBUT DE and corneal hyperalgesia (n = 22, 36.7%), defined as a pain sensitivity ≥40 mm (i.e., the cutoff value at the 95th percentile of corneal pain sensitivity in healthy subjects), a strong significant correlation was found between the subjective pain score and objective corneal pain sensation (R = 0.79). However, for the entire cohort, we found a weak positive correlation between the subjective pain score and objective corneal pain sensation. ConclusionsPatients with sBUT DE were hypersensitive to corneal pain, which suggested that corneal hyperalgesia partly accounted for subjective symptoms in patients with sBUT DE.

Confocal microscopy of corneal nerve plexus as an early marker of eye involvement in patients with type 2 diabetes

PurposeTo measure the thickness and length of corneal nerves and the peri-papillary retinal nerve fiber layer (RNFL) thickness in patients recently diagnosed with diabetes mellitus (DM). MethodsTwenty-two eyes of 22 patients recently diagnosed with type 2 DM and 22 eyes of 22 healthy individuals were consecutively enrolled. Central corneal sensitivity was measured using a Cochet-Bonnet esthesiometer, and corneal nerve length (CNL) and thickness (CNT) were evaluated through in vivo confocal microscopy. The confocal images were examined using software that could semi-automatically trace the corneal nerve pathway. Spectral domain optical coherence tomography (SD-OCT) was performed to quantify the overall and sectorial RNFL thickness. ResultsMean DM duration was 3.5 ± 1.7 months, whereas the mean glycemia and HbA1c levels were 180.5 ± 73.13 mg/dl and 8.6 ± 1.7% (65.2 ± 19.7 mmol/mol), respectively. Corneal sensation threshold was significantly lower in the DM group compared to control group (p = 0.003). CNL and CNT were reduced in the DM group (p = 0.043 and p = 0.004, respectively). Significant correlations were found between CNT and HbA1c levels (p = 0.04; r = −0.47), and between CNT and the corneal sensation threshold (p = 0.04; r = 0.69). RNFL thickness was significantly reduced in the temporal quadrants, but no correlation was found with CNT and CNL changes (p > 0.05). ConclusionsCNL and CNT changes are evident even in the early stages of DM, and RNFL reduction was recorded in the temporal quadrants. These findings indicate that, in the eye with diabetes, neuropathy may represent an early marker of the disease.

Randomized Controlled Study to Investigate the Effect of Topical Diquafosol Tetrasodium on Corneal Sensitivity in Short Tear Break-Up Time Dry Eye.

Complex mechanisms underlie dry eye (DE) symptom provocation. In particular, corneal hypersensitivity may provoke symptoms in short tear break-up time (BUT) DE characterized by tear film instability. We hypothesized that improved tear film stability may alleviate corneal sensitivity in patients with short tear BUT DE. Therefore, we investigated the effect of topical diquafosol tetrasodium (DQS) on corneal sensitivity in unstable tear film DE. This prospective, randomized study included 27 subjects (age: 39.1 ± 8.4years; range: 25-59years) with short tear BUT DE, defined based on the presence of DE symptoms and tear film instability. Subjects were randomly divided into DQS (3% DQS, 12 subjects) and artificial tear (AT; preservative-free AT, 15 subjects) groups. Subjects applied the medication 6 times a day for 5weeks. The perception of touch (S-touch) and pain (S-pain) sensitivity was measured using a Cochet-Bonnet esthesiometer. Tear evaluation, corneal sensitivity, and DE symptoms were compared before and after DQS or AT administration. The correlation between the improvement degrees of corneal sensitivity and DE symptoms following medication was analyzed. DQS significantly improved tear BUT and tear meniscus height (TMH) scores (p < 0.05), while AT significantly improved tear BUT (p < 0.05) but not TMH score. Mean S-pain and DE symptom scores were lower after medication use in the DQS (S-pain and DE symptoms: p < 0.05) and AT groups (S-pain: p = 0.05; DE symptoms: p < 0.05). However, S-touch did not change significantly in either group. A positive correlation was observed between the improvement degrees of S-pain and DE symptoms in the overall subjects studied. Both DQS and AT alleviate corneal hypersensitivity and DE symptoms in eyes with short tear BUT DE. However, DQS seems to be more effective to adjust tear environment, leading to the normalization of corneal sensitivity and DE symptoms. UMIN Clinical Trials Registry Identifier, UMIN000014536.

Short-Term Effects of Overnight Orthokeratology on Corneal Sub-basal Nerve Plexus Morphology and Corneal Sensitivity.

To assess the effects of a short period of orthokeratology (OK) on corneal sub-basal nerve plexus (SBNP) morphology and corneal sensitivity. Measurements were made in 56 right eyes of 56 subjects with low-to-moderate myopia who wore 2 OK lens designs (Group CRT: HDS 100 Paragon CRT, n=35; Group SF: Seefree; n=21) for a period of 1 month and in 15 right eyes of noncontact lens wearers as controls. The variables determined in each participant were corneal sensitivity using a Cochet-Bonnet esthesiometer and 12 SBNP variables determined on laser scanning confocal microscopy images using 3 different software packages. Correlation between SBNP architecture and corneal sensitivity was also examined. Few changes were observed over the 1-month period in the variables examined in the OK treatment and control groups. However, significant reductions were detected over time in the number of nerves in the central cornea in the groups CRT (P=0.029) and SF (P=0.043) and in central corneal sensitivity in CRT (P=0.047) along with significant increases in central and midperipheral corneal Langerhans cell counts in SF (P=0.001 and 0.048, respectively). This study provides useful data to better understand the anatomical changes induced by OK in corneal SBNP. The different response observed to the 2 OK lens designs requires further investigation.

Long-Term Impacts of Orthokeratology Treatment on Sub-Basal Nerve Plexus and Corneal Sensitivity Responses and Their Reversibility.

To examine the effects of one year of overnight orthokeratology (OK) treatment on the sub-basal nerve plexus (SBNP) and corneal sensitivity and to assess the reversibility of these effects one month after treatment interruption. Thirty-two subjects with low-moderate myopia underwent OK treatment for one year. Fifteen non-contact lens wearers served as controls. At the time points baseline, one year of treatment, and one month after removing the OK lenses, two tests were conducted: corneal sensitivity (Cochet-Bonnet esthesiometer) and SBNP imaging by in vivo confocal microscopy. In participants wearing OK lenses, significant reductions over the year were produced in SBNP nerve density (P=0.001 and P=0.006) and number of nerves (P<0.001 and P=0.001) in the central and mid-peripheral cornea, respectively. Differences over the year were also detected in central objective tortuosity (P=0.002). After lens removal, baseline values of nerve density (P=0.024 and P=0.001) and number of nerves (P=0.021 and P<0.001) for the central and mid-peripheral cornea, respectively, were not recovered. At one month post-treatment, a difference was observed from one-year values in central corneal sensitivity (P=0.045) and mid-peripheral Langerhans cell density (P=0.033), and from baseline in mid-peripheral objective tortuosity (P=0.049). Direct correlation was detected at one year between nerve density and tortuosity both in the central (P<0.01; r=0.69) and mid-peripheral cornea (P<0.01; r=0.76). Long-term OK treatment led to reduced SBNP nerve density and this was directly correlated with corneal tortuosity. After one month of treatment interruption, nerve density was still reduced.

The effects of subconjunctival bupivacaine, lidocaine, and mepivacaine on corneal sensitivity in healthy horses.

To compare the efficacy and duration of effect of three local anesthetics on corneal sensitivity when administered subconjunctivally in horses. Eight healthy adult horses. A randomized, masked, crossover study design was used, with a two-week washout period between trials. The subconjunctival space of the randomly selected eye was injected with 0.2 mLs of bupivacaine (0.5%), lidocaine (2%), mepivacaine (2%), or saline. All horses received each medication once. The contralateral eye served as a control. The corneal touch threshold (CTT) was measured in both eyes with a Cochet-Bonnet esthesiometer prior to sedation with xylazine, after sedation, and at 10-min intervals after subconjunctival injection until corneal sensitivity returned to baseline. The total time of decreased CTT and the maximum decrease in CTT were compared for each medication using a general linear mixed model (P < 0.05). Total time of decreased CTT was 105.0 min for bupivacaine, 103.8 min for lidocaine, 138.8 min for mepivacaine, and 7.5 min for saline. All local anesthetics decreased CTT longer than saline (P < 0.001) and mepivacaine decreased CTT longer than lidocaine (P = 0.04). The mean minimum CTT was 1.67 cm for bupivacaine, 1.42 cm for lidocaine, and 0.73 cm for mepivacaine, which were all significantly less (P < 0.001) than saline (4.73 cm). No evidence of corneal toxicity was noted with any treatment. Subconjunctival injections of lidocaine, bupivacaine, and mepivacaine effectively and safely reduce corneal sensitivity in eyes of healthy horses for 1.5-2 h, and may be useful for providing perioperative analgesia for equine corneal procedures.

Impact of Smoking on the Ocular Surface, Tear Function, and Tear Osmolarity

ABSTRACTPurpose: This study evaluated the effects of cigarette smoking on the ocular surface, tear function, and tear osmolarity.Materials and Methods: A total of 50 smokers with at least 5 years of heavy smoking (defined as 1 pack/day) and 51 nonsmoking, healthy individuals were enrolled. Tear osmolarity was measured with an osmometer (TearLab™ Osmolarity System). Ocular surface examinations involved corneal fluorescein staining, measurement of the tear film breakup time (TBUT), the Schirmer 1 test, measurement of corneal sensitivity with a Cochet–Bonnet esthesiometer, and conjunctival impression cytology. Dry eye symptoms were scored using the Ocular Surface Disease Index (OSDI) questionnaire. The results were compared with those from an age and sex-matched control group. The Chi-squared and independent sample t-tests were used for statistical analyses.Results: The smokers had significantly higher tear osmolarity values (305.38 ± 9.81 vs. 301.14 ± 7.04 mOsm/L; p = 0.014) and OSDI scores (34.13 ± 16.58 vs. 18.09 ± 9.61; p < 0.001) than the healthy controls. However, the TBUT, corneal sensitivity, and goblet cell density were significantly lower in smokers compared to healthy controls, but the fluorescein staining and Schirmer 1 test results were not statistically different between the smokers and controls.Conclusion: Smoking results in increased osmolarity of the tear film, which can damage the ocular surface and tear function.

Pilot Study of a “Large-Eye,” Surgically Induced Dry Eye Rabbit Model by Selective Removal of the Harderian, Lacrimal, and Meibomian Glands

Background/Aims: Establish a reliable rabbit dry eye (DE) model. Methods: An interventional cohort study surgically removing glands contributing to the tear film. Eight rabbits were studied after removal of left lacrimal, Harderian, or both glands. Additional rabbits had Meibomian glands in the left eye thermally obstructed. All were followed for 10 weeks with phenol red thread (PRT) and slit-lamp examination with 2% fluorescein. We assessed corneal sensitivity using a Cochet-Bonnet esthesiometer. Outcome measures were severity/duration of reduced PRT, punctate epithelial erosions (PEE), and histologic evidence of corneal pannus. Results: Fluorescein staining demonstrated signs of dryness including PEE in all of the interventional eyes. The subjective measurement of epithelial erosions correlated with decreased tear production. PRT measurements in the control eyes averaged 31.54 mm (±1.83) and 22.71 mm (±1.60) in the eight left eyes, without loss of corneal sensitivity. Conclusions: Surgical removal of either the Harderian or lacrimal gland results in statistically significant decreases in tear volume and the development of severe DE. Removal of both glands results in the occurrence of a DE of comparable severity/duration to removal of either the lacrimal or Harderian gland alone. Meibomian gland obstruction contributes less to the DE model.

Esthesiometric evaluation of corneal analgesia after topical application of 1% morphine sulfate in normal horses.

To evaluate whether topical ocular application of 1% morphine sulfate would change corneal sensitivity and to identify the duration of action. Eight healthy adult horses. Corneal touch threshold (CTT) was measured in the center of one randomly selected eye of each horse by Cochet-Bonnet esthesiometer (Luneau Cochet-Bonnet Esthesiometer; Western Ophthalmics, Lynnwood, WA, USA). Immediately following baseline CTT measurement, 0.3ml of 1.0% preservative-free morphine sulfate (Morphine Sulfate 25mg/ml Preservative-free; Hospira, Lake Forest, IL, USA) (3mg) was applied to the tested eye. The same volume of artificial tear (LiquiTears; Major Pharmacauticals, Livonia, MI, USA) solution was then applied to the control eye following acquisition of baseline CTT. Corneal touch threshold was then subsequently measured at 1min after medication application, followed by every 5min until 60min post administration. If the corneal touch threshold had not returned to baseline by 60min, measurements were continued at 15-min intervals until corneal sensitivity returned to baseline CTT measurement up to 180min post administration if needed. The control eye was treated identically and measurements on the control eye stopped when the corresponding treated eye returned to baseline. Mean baseline CTT of both eyes was 21.8mm with an identical range of 15-30mm. Mean corneal touch threshold was not statistically different between morphine-treated and control eyes (P=0.22). There was a large degree of inter- and intrasubject variation in the CTT measurements obtained. All but three horses were considered to be at baseline values by 60min. Topical ophthalmic 1% morphine sulfate did not have a clinically significant analgesic effect on the corneal touch threshold of intact healthy equine corneas.

Subconjunctival Bevacizumab Injection Impairs Corneal Innervations and Epithelial Wound Healing in Mice.

To investigate the effects of subconjunctival bevacizumab injection on the corneal nerve, sensitivity, and epithelial wound healing in mice. Adult C57BL/6 mice were treated with subconjunctival injection of 1, 2, 5, or 25 mg/mL bevacizumab. The corneal nerve was observed with whole-mount anti-β3-tubulin fluorescence staining. Corneal sensitivity was measured with a Cochet-Bonnet esthesiometer. The protein levels of pigment epithelium-derived factor (PEDF), nerve growth factor (NGF), glial-derived neurotrophic factor (GDNF), and ciliary neurotrophic factor (CNTF) were measured by ELISA. The corneal epithelial wound-healing rate was evaluated by fluorescein staining. The recovery of impaired mouse corneal innervations and epithelial wound-healing rate following bevacizumab injection was evaluated with the co-injection of PEDF, NGF, or CNTF. Subconjunctival bevacizumab injection caused apparent corneal nerve degeneration, attenuated corneal sensitivity, and delayed corneal epithelial wound healing and nerve regeneration in normal mice, which was more significant with increased concentration and times of the bevacizumab injection. However, the corneal nerve and sensitivity gradually improved and recovered in mice with a single injection of 1 to 5 mg/mL bevacizumab. Moreover, the bevacizumab injection significantly decreased the corneal PEDF, NGF, and CNTF content, whereas exogenous PEDF, NGF, or CNTF supplement attenuated impairment of the corneal nerve, sensitivity, and epithelial wound healing after subconjunctival bevacizumab injection. Subconjunctival bevacizumab injection impairs corneal innervations, epithelial wound healing, and nerve regeneration in normal mice, which may be caused by the reduction of neurotrophic factor content in the cornea.

Assessment of Corneal Sensation, Innervation and Retinal Nerve Fiber Layer in Patients Treated with Multiple Intravitreal Ranibizumab Injections.

PurposeTo evaluate the effects of repeated intravitreal ranibizumab injections on corneal sensitivity, corneal sub-basal nerve plexus (SBNP) and peripapillary retinal nerve fiber layer (RNFL) thickness in patients with neovascular age-related macular degeneration (AMD).MethodsSixty-six eyes of 33 patients who had received unilateral repeated intravitreal ranibizumab injections (0.5 mg/0.05 ml) for the treatment of AMD and 25 eyes of 25 healthy subjects were included in the study. Central corneal sensation was measured using the contact Cochet-Bonnet esthesiometer. The laser scanning in vivo corneal confocal microscope was used to determine corneal SBNP parameters. The peripapillary RNFL thickness was assessed with spectral-domain optical coherence tomography. Data obtained from the ranibizumab-injected eyes were compared with those of the fellow non-treated eyes and the eyes of the healthy control subjects.ResultsThe mean number of ranibizumab injections per eye was 8.9±5.0 (range 3–20). There were no statistically significant differences in the central corneal sensitivity threshold and corneal SBNP parameters between the ranibizumab-injected eyes and the fellow untreated eyes or between those with neovascular AMD and the healthy control group (P>0.05 for all). The average peripapillary RNFL thickness of the treated eyes did not differ significantly to the fellow eyes (P = 0.237), and the eyes of healthy control subjects (P = 0.918). There were no significant correlations between the number of ranibizumab injections and any of the study parameters.ConclusionsMultiple intravitreal injections of ranibizumab seem to have no harmful effects on corneal sensitivity, innervation and peripapillary RNFL thickness in patients with AMD.

Corneal sensitivity in five horse breeds

ABSTRACT: This study aimed to determine and compare corneal sensitivity values in different regions of the cornea in five horse breeds. One hundred and forty five healthy horses, adults of both sexes, of the following breeds - Arabian horse (AH; n=20), Mangalarga Marchador (MM; n=50), Pure Blood Lusitano (PBL; n=35), Quarter Horse (QH; n=20), Brazilian Sport Horse (BSH; n=20)-were investigated. Corneal touch threshold (CTT) was measured with a Cochet-Bonnet esthesiometer in five different corneal regions. Measurements of the median central CTT were: 4.50±0.50cm (AH), 3.50±0.56cm (MM), 3.00±0.25cm (PBL), 2.50±0.44cm (QH) and 2.50±0.00cm (BSH). The central region was the most sensitive and the dorsal region the least sensitive corneal region for all breeds. CTT values differed for corneal regions and horse breeds. The CTT values were different among the corneal regions and the horse breeds. Arabian horses presented higher sensitivity values being the most sensitive in all of the corneal regions.

Determining Factors for Fast Corneal Sensitivity Recovery After Pterygium Excision.

To establish determining factors for fast corneal sensitivity (CS) recovery after pterygium excision. Thirty-two eyes of 14 males and 18 females with primary nasal pterygium were recruited. Differences in CS (in the 4 quadrants and the center using a Cochet-Bonnet esthesiometer), pterygium corneal area (PCA), tear osmolarity, tear break-up time, Schirmer test, and ocular symptoms were analyzed before and 1 month after lesion excision. The relationship between CS recovery (difference between the 2 time points; CS1 - CS0) and the other features was assessed. All the studied locations exhibited normal (6 cm) or near-normal mean CS at the 2 time points, except a tendency for moderate hypoesthesia in nasal CS0 (median 4.5; range: 1.5-6.0 cm). Point by point comparison revealed significant postoperative improvements in nasal location (P = 0.008; Wilcoxon signed-rank test) with normal values in 17 eyes (53%) and a median CS1 = 5.0 cm (2.5-5.5 cm) in 15 eyes with no complete recovery. No significant correlation was found between CS0 and the studied variables, and CS1 was only significantly correlated with PCA (rho: -0.441; P < 0.05). CS recovery also showed significant correlation with PCA (rho = -0.516; P < 0.01). CS recovery after pterygium excision showed important variability, and the only studied factor that seems to be determinant could be PCA. It would be advisable to operate when the lesion is relatively small, with lower surgical injury and faster and complete recovery, thus protecting ocular surface homeostasis.

IL-6 Contributes to Corneal Nerve Degeneration after Herpes Simplex Virus Type I Infection

Herpes simplex virus type 1 (HSV-1) is a leading cause of neurotrophic keratitis characterized by decreased corneal sensation because of damage to the corneal sensory fibers. We and others have reported regression of corneal nerves during acute HSV-1 infection. To determine whether denervation is caused directly by the virus or indirectly by the elicited immune response, mice were infected with HSV-1 and topically treated with dexamethasone (DEX) or control eye drops. Corneal sensitivity was measured using a Cochet-Bonnet esthesiometer and nerve network structure via immunohistochemistry. Corneas were assessed for viral content by plaque assay, leukocyte influx by flow cytometry, and content of chemokines and inflammatory cytokines by suspension array. DEX significantly preserved corneal nerve structure and sensitivity on infection. DEX reduced myeloid and T-cell populations in the cornea and did not affect viral contents at 4 and 8 days post infection. The elevated protein contents of chemokines and inflammatory cytokines on infection were greatly suppressed by DEX. Subconjunctival delivery of neutralizing antibody against IL-6 to infected mice resulted in partial preservation of corneal nerve structure and sensitivity. Our study supports a role for the immune response, but not local virus replication in the development of HSV-1-induced neurotrophic keratitis. IL-6 is one of the factors produced by the elicited inflammatory response to HSV-1 infection contributing to nerve regression.

Relationship of Corneal Pain Sensitivity With Dry Eye Symptoms in Dry Eye With Short Tear Break-Up Time.

The purpose of this prospective comparative study was to investigate corneal sensitivity in subjects with unstable tear film, with and without dry eye (DE) symptoms. Forty-one eyes of 41 volunteers (mean age: 45.1 ± 9.4 years; age range, 23-57 years), with normal tear function and ocular surface except for tear stability, were studied. The eyes were divided into two groups depending on the presence or absence of DE symptoms: 21 eyes with DE symptoms (symptomatic group); and 20 eyes without DE symptoms (asymptomatic group). Three types of corneal sensitivity values were measured using a Cochet-Bonnet esthesiometer: the sensitivity for perception of touch (S-touch), the sensitivity for blinking (S-blink), and the sensitivity for pain (S-pain). Mean S-blink and S-pain were significantly higher in the symptomatic group than in the asymptomatic group (P < 0.05), whereas there was no significant difference in mean S-touch between these groups (P > 0.05). Corneal sensitivity for blinking and pain evoked by increased stimuli was higher in the symptomatic group (subjects with short break-up time DE) compared with subjects who have no DE symptoms despite decreased tear stability. The presence of both tear instability and hyperesthesia, rather than tear instability alone, may contribute to DE pathogenesis.