Corneal Nerve Assessment by Aesthesiometry: History, Advancements, and Future Directions.

The measurement of corneal sensation allows clinicians to assess the status of corneal innervation and serves as a crucial indicator of corneal disease and eye health. Many devices are available to assess corneal sensation, including the Cochet-Bonnet aesthesiometer, the Belmonte Aesthesiometer, the Swiss Liquid Jet Aesthesiometer, and the newly introduced Corneal Esthesiometer Brill. Increasing the clinical use of in vivo confocal microscopy and optical coherence tomography will allow for greater insight into the diagnosis, classification, and monitoring of ocular surface diseases such as neurotrophic keratopathy; however, formal esthesiometric measurement remains necessary to assess the functional status of corneal nerves. These aesthesiometers vary widely in their mode of corneal stimulus generation and their relative accessibility, precision, and ease of clinical use. The development of future devices to optimize these characteristics, as well as further comparative studies between device types should enable more accurate and precise diagnosis and treatment of corneal innervation deficits. The purpose of this narrative review is to describe the advancements in the use of aesthesiometers since their introduction to clinical practice, compare currently available devices for assessing corneal innervation and their relative limitations, and discuss how the assessment of corneal innervation is crucial to understanding and treating pathologies of the ocular surface.

Comparison of Proparacaine, Tetracaine, and Oxybuprocaine in Corneal Sensitivity Measurement.

Purpose: This study aimed to determine the onset and duration of action of 3 commercially available topical anesthetic solutions in Brazil, using the Cochet-Bonnet esthesiometer (Luneau®, Paris, France) and to quantitatively assess patient-reported discomfort during application. Methods: A prospective, randomized, masked, and double-blind study was conducted, involving 40 eyes from 21 patients. Patients were administered each one of the topical anesthetics weekly, and corneal sensitivity was measured using the Cochet-Bonnet esthesiometer's corneal touch threshold (CTT). Patients rated the burning sensation using a visual analogue scale (VAS). Results: Among the 21 patients (42.9% male), with a mean age of 31.95 years (±standard deviation = 10.17, range = 22.0-58.0), corneal sensitivity significantly decreased 30 s after application, returning to baseline after 30 min for all groups (P < 0.0001). Significant differences in CTT were observed at 5 min, with proparacaine exhibiting a superior anesthetic effect (P = 0.0003), at 10 min, where tetracaine displayed the most substantial anesthetic effect (P = 0.0135), and at 20 min, where tetracaine demonstrated the highest anesthetic efficacy (P < 0.0001). VAS scores indicated the most intense burning sensation with tetracaine (P < 0.0001). Men reported experiencing more discomfort during instillation compared with women (P = 0.0168). Conclusions: Proparacaine exhibited the fastest onset of action among the 3 topical anesthetics and provided a more comfortable eye sensation during instillation. However, tetracaine demonstrated the longest duration of action despite causing more discomfort.

New disposable esthesiometer (KeraSenseⓇ) to improve diagnosis and management of neurotrophic keratitis.

PURPOSE: To validate the use, repeatability, and reproducibility of a new, cost-effective, disposable, sterile device (KeraSenseⓇ, Dompè farmaceutici SpA, Milan Italy) compared to Cochet-Bonnet (CB) esthesiometer. Secondly, to identify a simple, safe, rapid, and low-cost test to diagnose neurotrophic keratitis (NK). METHODS: 16 patients with diagnosis of NK stage I, 25 patients with diabetes mellitus (DM), and 26 healthy subjects were included in the study. Corneal sensitivity (CS) was assessed by CB and KeraSenseⓇ. Repeatability, accuracy, and reproducibility of the novel disposable aesthesiometer were assessed. Specificity, sensitivity, and cut-off value for NK diagnosis were calculated by ROC curve analysis. RESULTS: All NK patients showed a CS ≤ 40 mm, while none of the healthy patients showed a CS value < 50 mm. Significant agreement was found between CB measurements and the single use esthesiometer evaluations of CS (p < 0.001). Repeatability evaluations of the single use esthesiometer showed 100% agreement between different measurements (p < 0.001). Reproducibility evaluations showed 99.6% concordance between different operators (p < 0.001). A 55 mm value of the single use esthesiometer was adequate to exclude an NK diagnosis, while all NK patients showed a value ≤ 35 mm. CONCLUSIONS: Corneal hypo/anaesthesia is considered the hallmark of NK. The use of the novel single-use esthesiometer will allow for a diagnostic improvement in NK, sparing time and guaranteeing patients' safety. Diabetic patients despite normal corneal findings may show impairment of CS, suggesting a preclinical stage of NK, requiring a close follow-up.

Clinical application of the Swiss Liquid Jet Aesthesiometer for corneal sensitivity measurement.

CLINICAL RELEVANCE: Corneal sensitivity represents an important indicator for corneal health, its innervation and hence also for ocular disease. It is therefore of great interest from a clinical and research perspective to quantify ocular surface sensation. BACKGROUND: The aim of this prospective cross-sectional cohort study was to clinically test the within-day and day-to-day repeatability of the new Swiss Liquid Jet Aesthesiometer, employing small droplets of isotonic saline solution for repeatability, and correlate with the Cochet-Bonnet aesthesiometer in a cohort of participants of two different age groups, based on participant feedback (psychophysical method). METHODS: Participants were recruited from two equally, large age groups: group A (18-30 years) and group B (50-70 years). The inclusion criteria were healthy eyes, Ocular Surface Disease Index (OSDI) ≤ 13, and no contact lens wear. Mechanical corneal sensitivity threshold measurements with means of liquid jet and Cochet-Bonnet methods were carried out twice during two visits (a total of four measurements), with a stimulus temperature equal to or slightly above the ocular surface temperature. RESULTS: Ninety participants completed the study (n = 45 per age group, average age in group A: 24.2 ± 2.94 years, group B: 58.5 ± 5.71 years). The coefficient of repeatability for the liquid jet method was 2.56 dB within visits and 3.61 between visits. For the Cochet-Bonnet method, it was 2.27 dB within visits and 4.42 dB between visits (Bland Altman with bootstrap analysis). Moderate correlation was observed between the liquid jet and the Cochet-Bonnet method (r = 0.540, p < .001, robust linear regression). CONCLUSIONS: Swiss liquid jet aesthesiometry offers a new examiner independent method for corneal sensitivity measurement with acceptable repeatability and moderate correlation with the Cochet-Bonnet aesthesiometer. It offers a large stimulus pressure range of 100-1500 mbar and a precision of 1 mbar. Stimulus intensity can be tuned more precisely and much smaller sensitivity fluctuations may be potentially detected.

Sensory Changes in the Ocular Surface After Pterygium Removal.

Purpose: We measure changes in ocular surface sensation after pterygium surgery with a conjunctival autograft. Methods: This prospective, interventional study was carried out in patients, with nasal primary pterygium undergoing pterygium surgery with conjunctival autograft. Sensation was measured by applying the tip of the Cochet-Bonnet esthesiometer filament perpendicular to the ocular surface in the cornea and conjunctiva. Patients were tested preoperatively (baseline), and at 2 weeks, 2 and 4 months, postoperatively. Results: Nineteen eyes of 18 patients completed the 4-month follow-up. Mean age was 61±10.1 (range 36-76) years. Corneal sensation returned to normal values in all at 2 and at 4 months. The central cornea was significantly more sensitive compared to the average of the four peripheral measurements pre- (59.2 mm vs 48.3 mm, p=0.000) and postoperatively (59.2 mm vs 48.4 mm, p=0.000). Conjunctival sensation was reduced significantly 2 months postoperatively in the inferior region (p=0.04). Four months postoperatively, it was more sensitive in the superior area (13.9 mm vs 17.1 mm, p=0.01) and the inferior area (13.7 mm vs 19.5 mm, p=0.003). In each matching area, the cornea was significantly more sensitive than the conjunctiva pre- and postoperatively (p=0.00). Sensation was not significantly different between the sexes or age groups. Conclusion: This study demonstrates the presence of inferior and superior conjunctival hyperesthesia at conjunctival autograft sites after pterygium surgery. The healing process, sensory input, tear film instability and epitheliopathy of the ocular surface are possible explanations for these novel findings.

Corneal sensitivity in silicone hydrogel and rigid gas permeable contact lens wear.

PURPOSE: The aim of this prospective cross-sectional cohort study was to test the effect of silicone hydrogel (SH) and rigid gas permeable (RGP) contact lens (CL) wear on corneal sensitivity, applying the new Swiss Liquid Jet Aesthesiometer for Corneal Sensitivity (SLACS) and the Cochet-Bonnet (CB) aesthesiometer, based on subject feedback (psychophysical method). METHODS: Participants were recruited for three equally large groups: Group A (SH CL), Group B (RGP CL) and Group C (non-CL wearers). Inclusion criteria were healthy eyes and OSDI ≤ 13. Corneal sensory thresholds were determined twice during two visits, with aid of SLACS and CB. RESULTS: 96 participants completed the study (n = 33 in groups A and C, n = 30 in group B); average age in group A: 27.42 ± 6.83 years, group B: 36.90 ± 9.68 years and group C: 26.06 ± 6.19 years. No statistically significant difference in corneal sensitivity was observed between the three groups for either method (p = 0.302 for SLACS, p = 0.266 for CB; Kruskal-Wallis rank sum test). Higher CSTs were obtained for males than for females in both CL groups with SLACS, and with CB only in the RGP CL group (p = 0.041 in Group A, p = 0.006 in Group B with SLACS; p = 0.041 in Group B with CB; bootstrap analysis with age correction and gender balancing). No correlation was observed between CL comfort and corneal sensitivity for neither method applied (for SLACS r = 0.097 and p = 0.51, for CB r = 0.17 and p = 0.15; robust linear mixed model). CONCLUSIONS: No difference in corneal sensitivity with CL compared to non-CL wear was noted in this study. However, lower levels of corneal sensitivity were observed in the male CL groups, warranting further investigation.

Evaluation of Corneal Sensitivity and Quadrature Variability in Patients with Diabetic Neuropathy.

PURPOSE: The purpose of the study was to evaluate the corneal sensitivity and its quadrature variability in patients with diabetic neuropathy (DN) diagnosed with electromyography and to compare these results with age- and sex-matched healthy individuals. METHODS: The left eyes of 32 patients who applied for refraction or fundus examination and had a diagnosis of DN by electromyography in their medical history were included in this study. Corneal sensitivity was evaluated using the Cochet-Bonnet esthesiometer (Luneau, Paris) in five zones: central, nasal, superior, temporal, and inferior. The measurements of the patients were compared with the measurements of 32 age- and sex-matched healthy volunteers. Furthermore, the measurements of five corneal zones were compared with each other, and the level of correlation was investigated in each group. RESULTS: The central corneal sensitivity values were measured as 4.12 ± 1.04 (mm) and 5.92 ± 0.14 (mm) (P < 0.001). While the sensitivity values at the superior, inferior, nasal, and temporal quadrants were detected as 5.85 ± 0.21, 5.85 ± 0.26, 5.94 ± 0.13, 5.93 ± 0.13, and 5.92 ± 0.14 (mm) in the control group, it was measured as 3.67 ± 0.66, 3.67 ± 0.62, 3.67 ± 0.62, and 3.89 ± 0.73 (mm) in the DN group, respectively. The corneal sensitivity values were all found to be significantly lower in the DN group (P < 0.001 for all parameters) at all quadrants as well as the central cornea. Furthermore, a moderate positive correlation between all five zones in the control group and a very strong positive correlation in the DN group were found in terms of the corneal quadrature sensitivity. CONCLUSION: The current study revealed a significant reduction in corneal sensitivity in patients with DN. In both the control group and DN group, all corneal zones showed positive correlations which show the consistency of the measurement in different quadratures. Evaluating corneal sensitivity with a Cochet-Bonnet esthesiometer might serve as a useful screening tool in detecting neuropathy development. By taking the necessary precautions, further damage can be prevented.

Corneal anesthesia associated with topical application of 2% lidocaine nonophthalmic gel to healthy canine eyes.

OBJECTIVE: To assess the degree and duration of corneal anesthesia induced by topical application of 2% lidocaine gel to the healthy canine eye. ANIMALS: Nineteen adult Beagles free of ocular abnormalities. PROCEDURES: Baseline corneal touch threshold (CTT) was measured bilaterally with a Cochet-Bonnet aesthesiometer. The 2% lidocaine gel (0.1 mL) was applied to one eye, randomly assigned, and the same volume of a lubricant gel was applied to the opposite eye. The CTT measurements were repeated bilaterally within 1 minute, after drug application, and every 5 minutes, until the baseline corneal sensitivity was restored. The potential for local adverse effects was evaluated. RESULTS: Complete desensitization of the cornea (CTT = 0) was achieved one minute after lidocaine gel application and was maintained during 25.3 ± 12.5 minutes. Overall, the corneal sensitivity was significantly decreased for 58.4 ± 16.6 minutes compared with baseline level. Minor and reversible punctate epithelial erosions of the cornea were observed in the two treatment groups and were attributed to the anesthetic effect and the aesthesiometry procedure. CONCLUSIONS: In the current study, the 2% lidocaine gel provided a sustained, deep and well-tolerated corneal anesthesia in ophthalmically normal dogs.

Nerve growth factor in dogs: Assessment of two immunoassays and selected ocular parameters following a nicergoline challenge per os.

Impairment of corneal nerves can result in the development of ocular surface diseases such as aqueous tear deficiency and neurotrophic keratopathy. This study investigates oral nicergoline, an α-adrenoceptor antagonist shown to enhance endogenous secretion of nerve growth factor (NGF) by the lacrimal gland, as a potential therapy for these conditions. Five female spayed Beagle dogs received a 2-week course of oral nicergoline (10 mg twice daily). Drug safety was evaluated with ophthalmic and physical examinations, blood pressure monitoring, bloodwork, and urinalysis. The effect of nicergoline on the ocular surface was assessed with corneal esthesiometry, Schirmer tear test-1, and tear film breakup time. Drug effect on NGF levels was assessed by collecting tears and blood at baseline and completion of therapy using a bead-based immunoassay and an enzyme-linked immunosorbent assay. Although nicergoline was well tolerated in all dogs, it did not have a significant impact on corneal sensitivity, tear production, or tear stability. Of note, NGF was below the limit of quantification in all tear samples and was only detected in 8/20 serum samples with no significant difference between levels at baseline (189.4 ± 145.1 pg/mL) and completion of therapy (149.4 ± 79.4 pg/mL). Further validation of NGF analytical assays is warranted before nicergoline is investigated in clinical patients.

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

PURPOSE: To evaluate corneal tactile and pain sensations in patients with short tear film break-up time dry eye (sBUT DE). METHODS: This 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. RESULTS: Patients with sBUT DE had higher corneal pain sensitivity (26.3 ±â€¯23.1 mm) than healthy subjects (6.9 ±â€¯16.4 mm), but similar corneal tactile sensation (52.0 ±â€¯15.5 mm and 52.9 ±â€¯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. CONCLUSIONS: Patients with sBUT DE were hypersensitive to corneal pain, which suggested that corneal hyperalgesia partly accounted for subjective symptoms in patients with sBUT DE.

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

PURPOSE: To determine the effect of isotretinoin on corneal sensitivity in acne patients. METHODS: Fifty 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. RESULTS: The 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. CONCLUSIONS: According 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.

Tactile sensitivity thresholds for the radial hemi-pulp of the index: A comparison between the Semmes-Weinstein and Cochet-Bonnet tests in 25 healthy subjects.

The purpose of this work was to determine whether the Cochet-Bonnet (CB) corneal sensitivity test has a lower cutaneous pulp sensitivity threshold than the Semmes-Weinstein (SW) monofilament test. Tactile sensitivity thresholds for the radial hemi-pulp of the index finger of 25 healthy adult subjects aged 30 years on average were measured using SW and CB esthesiometers. The sensitivity threshold of the radial hemi-pulp of the index was lower with the CB test than with the SW test. The sensitivity and specificity of the CB test on palm wounds still needs to be determined to rule out nerve damage.

Effect of topical application of 2% lidocaine gel on corneal sensitivity of clinically normal equine eyes.

OBJECTIVE: To assess the degree and duration of corneal anaesthesia provided by topical application of a non-ophthalmic 2% lidocaine gel in horses. STUDY DESIGN: Experimental, 'blinded', randomized prospective study. ANIMALS: Twelve adult horses without relevant ocular abnormalities. METHODS: Baseline corneal touch threshold (CTT) measurements were obtained bilaterally by use of a Cochet-Bonnet aesthesiometer just prior to topical treatment. A volume of 0.2mL of 2% lidocaine gel was administered in one randomly selected eye and the same volume of a viscous lubricant in the other eye to serve as control. The CTT value was measured on both eyes 5, 10, 20, 30, 45, 60, 75 and 90 minutes after drug application. The potential for local adverse effects following lidocaine gel application was also evaluated. RESULTS: Mean CTT baseline measurements were not significantly different (p>0.05) between the control eyes (3.41±0.56cm) and those subsequently treated with the lidocaine gel (3.50±0.64cm). In control eyes, no significant changes in corneal sensitivity (p>0.05) occurred over time during the study period. By contrast, a marked reduction in corneal sensitivity was observed after lidocaine application, with mean CTT values significantly lower (p<0.001) than those of the control eyes from 5 to 75 minutes. A steady-state maximal corneal anaesthesia was present from 10 to 45 minutes after lidocaine gel application with mean CTT values ranging from 0.21 to 0.45cm. Corneal epithelial irregularities were detected in three lidocaine-treated eyes, but spontaneous resolution occurred within 24hours. CONCLUSIONS AND CLINICAL RELEVANCE: Deep and sustained corneal anaesthesia is achieved after application of 2% lidocaine gel to the equine eye, with minimal changes in the corneal epithelium. It might be useful for minor ophthalmic surgeries performed in the standing sedated horse.

Effects of topical flurbiprofen sodium, diclofenac sodium, ketorolac tromethamine and benzalkonium chloride on corneal sensitivity in normal dogs.

To evaluate corneal sensitivity by using the Cochet-Bonnet® esthesiometer in normal canine eyes at different time points following instillation of three different topical non-steroidal anti-inflammatory drugs (flurbiprofen sodium 0.03%, diclofenac sodium 0.1% and ketorolac tromethamine 0.5%) and benzalkonium chloride 0.01%. Six healthy mixed breed dogs from the same litter were used in two different stages. First, one drop of flurbiprofen sodium 0.03% and diclofenac sodium 0.1% in each eye; second, one drop of ketorolac tromethamine 0.5% and benzalkonium chloride 0.01% in each eye. Baseline esthesiometry was obtained before eye drop application and every 15 minutes thereafter until a total of 105 minutes of evaluation time. A one-week interval was allowed between the two treatment phases. Statistical analysis was used to compare means according to time of evaluation and drug used. Diclofenac sodium 0.1% decreased corneal sensitivity at 75 and 90 minutes (P > 0.015) with possible interference on neuronal nociceptive activity and analgesic effect while ketorolac tromethamine 0.5% did not show any variation for esthesiometry means along the evaluation. Flurbiprofen sodium 0.03% resulted in increased esthesiometry values 30 minutes after instillation (P > 0.013), increasing corneal sensitivity and possibly producing a greater irritant corneal effect over its analgesic properties. Benzalkonium chloride 0.01% significantly increased corneal sensitivity at 15 minutes of evaluation (P > 0.001), most likely resulting from its irritating effect. Esthesiometry did not allow a definite conclusion over the analgesic effect of the NSAIDs tested; however it was effective in detecting fluctuations in corneal sensitivity.

Corneal sensitivity in five horse breeds / Sensibilidade corneana em cinco raças de equinos

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.

RESUMO: Objetivou-se com o presente estudo, determinar e comparar valores de sensibilidade corneana em diferentes regiões da córnea em cinco raças de equinos. Foram investigados 145 equinos hígidos, adultos de ambos os sexos, das raças: Puro Sangue Árabe (PSA; n=20), Mangalarga Marchador (MM; n=50), Puro Sangue Lusitano (PBL; n=35), Quarto de Milha (QH; n=20) e Brasileiro de Hipismo (BSH; n=20). O limiar táctil da córnea (LTC) foi mensurado com o auxílio do estesiômetro de Cochet-Bonnet, em cinco diferentes regiões da córnea (central, nasal, ventral, temporal e dorsal). Os valores médios das mensurações do LTC central foram: 4,50±0,50cm (PSA), 3,50±0,56cm (MM), 3,00±0,25cm (PSL), 2,50±0,44cm (QM) e 2,50±0,00cm (BH). A região central foi a mais sensível e a região dorsal a menos sensível para todas as raças. Os valores de LTC diferiram para as regiões da córnea e entre as raças dos cavalos, sendo a raça Puro Sangue Árabe o que apresentou valores maiores de sensibilidade, desta forma sendo o mais sensível em todas as regiões corneanas.

Conjunctival Sensation in Scleritis.

PURPOSE: To investigate conjunctival sensation in patients with scleritis. METHODS: Retrospective cross-sectional study of patients with scleritis. Conjunctival sensation was tested by Cochet-Bonnet aesthesiometer in four quadrants of the bulbar conjunctiva plus the area(s) of active or previously active inflammation; sensation was compared with the contralateral eye. RESULTS: Of 28 patients with scleritis, nine had active scleritis and 19 had inactive scleritis. Eleven patients had a systemic autoimmune condition and five had infectious scleritis. The mean conjunctival sensation score of areas of inactive scleritis was significantly less than that of corresponding normal areas in the contralateral eye (p<0.001). Among patients with presumed herpetic scleritis, conjunctival sensation was significantly lower in the affected eye than in the unaffected eye (p<0.001). CONCLUSIONS: Conjunctival sensation is decreased in areas of previously active inflammation from scleritis. Eyes with herpetic scleritis had reduced conjunctival sensation, even in areas without previous active inflammation.

Corneal anesthesia following application of 0.4% oxybuprocaine hydrochloride ophthalmic solution to normal feline eyes.

OBJECTIVE: To evaluate the loss and recovery of corneal sensitivity after instillation of 0.4% oxybuprocaine hydrochloride solution in the normal feline eye. ANIMAL STUDIED: Eighteen European shorthair cats free of ocular disease PROCEDURES: Baseline corneal touch threshold (CTT) readings were obtained bilaterally with a Cochet-Bonnet aesthesiometer prior to treatment. Subsequently, each cat received a single drop of 0.4% oxybuprocaine ophthalmic solution in the right eye and one drop of sterile 0.9% NaCl in the left eye to serve as control. The corneal touch threshold (CTT) of both eyes was then measured 1 min after drug administration and every 5 min for 60 min. The potential for ocular irritation following oxybuprocaine application was also evaluated. RESULTS: Baseline CTT readings were not significantly different (P > 0.05) between the control and oxybuprocaine-treated eyes with values of 1.75 ± 0.31 cm and 1.75 ± 0.30 cm, respectively. In control eyes, mean CTT did not significantly change (P > 0.05) during the study period. By contrast, after oxybuprocaine application mean CTT was significantly reduced from baseline (P < 0.05) for 45 min. Maximal corneal anesthesia, with a CTT value of 0, was achieved at 1 and 5 min in all treated eyes. A markedly reduced mean CTT of 0.14 ± 0.23 cm was still present at 20 min. Age and gender did not significantly affect corneal anesthesia. No clinically relevant ocular side effects occurred during the observation period. CONCLUSION: This is the first study that provides objective information on the depth and duration of corneal anesthesia following instillation of oxybuprocaine in healthy feline eyes.

Evaluation of corneal anaesthesia after the application of topical 2 per cent lidocaine, 0.5 per cent bupivacaine and 1 per cent ropivacaine in dogs.

The objective of this study was to describe and compare the efficacy and duration of topical anaesthesia induced by 2 per cent lidocaine (L), 0.5 per cent bupivacaine (B) and 1 per cent ropivacaine (R) in the dog using 24 clinically healthy beagles with normal ocular examination. Dogs were randomly divided into three groups: 2 per cent lidocaine (n=8), 0.5 per cent bupivacaine (n=8) and 1 per cent ropivacaine (n=8). The baseline corneal touch threshold (CTT) was measured using a Cochet-Bonnet aesthesiometer. Following baseline CTT measurement, a single drop of the assigned anaesthetic was applied to each eye and the CTT was measured bilaterally within one minute after administration and every five minutes until the basal CTT value was restored. Data were analysed with non-parametric analysis of variance models and Dunnet's test for post hoc analysis. One per cent ropivacaine was the most effective drug (LCTTmax=3 cm, BCTTmax=2 cm, RCTTmax=0 cm; P<0.001), and had the shortest latency (LLatency=5 minutes, BLatency=5 minutes, RLatency=1 minute; P<0.001) and the smallest AUC (LAUC=80 cm×minute, BAUC=68.25 cm×minute, RAUC=36.88 cm×minute; P<0.001). There was no statistical difference in the duration of corneal anaesthesia between the groups (P=0.09) and all topical anaesthetics tested reduced corneal sensitivity, although 1 per cent ropivacaine had the maximal and quickest anaesthetic effect. This drug could be used for specific diagnostic procedures where quick and short, but effective, corneal anaesthesia is needed.

Ophthalmic and anesthetic evaluation of topical 1 percent tetracaine and 0.5 percent proparacaine in dogs / Ação anestésica e oftálmica da administração de colírio de tetracaína 1 por cento e proparacaína 0,5 por cento em cães

The aim of this study was to establish the action of 1 percent tetracaine eye drops in combination with 0.1 percent phenylephrine in two different posologies and their effects on the eye compared to the 0.5 percent proparacaine drops in dogs. 22 animals were divided into two groups: TG (11 animals), received 1 percent tetracaine associated with 0.1 percent phenylephrine eye drops, one drop instilled in the left eye and two drops, with one-minute interval between each, instilled in the right eye; PG (11 animals) received 0.5 percent proparacaine eye drops following the same dosage. The average duration of the observed anesthetic action was 25 minutes for tetracaine and 15 minutes for proparacaine. The instillation of two drops increased anesthetic time in five minutes. No changes in intraocular pressure, pupil diameter and tear production was observed. The drops of tetracaine triggered chemosis in four (36.4 percent) animals. Topical anesthesia with proparacaine eye drops showed no adverse reactions and is thus recommended preferentially.

Estudou-se a ação do colírio de tetracaína 1 por cento, em associação com a fenilefrina 0,1 por cento em duas posologias diferenciadas, bem como seus efeitos oculares, comparando-a com a do colírio de proparacaína 0,5 por cento em cães. Vinte e dois animais foram separados em dois grupos. Os do GT (n=11) receberam colírio de tetracaína 1 por cento associada à fenilefrina 0,1 por cento, sendo uma gota instilada no olho esquerdo e duas gotas, com intervalo de um minuto entre cada, instiladas no olho direito; e os do GP (n=11), receberam colírio de proparacaína 0,5 por cento seguindo a mesma posologia. A média de duração da ação anestésica observada foi de 25 minutos para a tetracaína e 15 minutos para a proparacaína. A instilação de duas gotas aumentou o tempo anestésico em cinco minutos. Não ocorreram alterações na pressão intra-ocular, no diâmetro pupilar e na produção lacrimal. O colírio de tetracaína desencadeou quemose em quatro (36,4 por cento) animais. Na anestesia tópica do olho com proparacaína não ocorreram reações adversas sendo, assim, recomendada preferencialmente.

Changes in Corneal Sensitivity after Laser in-situ Keratom ileusis

To evaluate the changes of corneal sensitivity after LASIK, we measured corneal sensitivity threshold at 5 regions of cornea using Cochet-Bonnet aesthesiometer in 41 myopic eyes of 23 patients who underwent LASIK. Corneal sensitivities were tested in the Central, medial, superior, temporal and inferior region of cornea preoperatively and postoperatively. Central corneal sensitivity was reduced to 1.1+/-4.6% of preoperative sensation at 1 day postoperatively and gradually recovered showing 40.3+/-27.8% at 3 months postoperatively. The sensitivity of the central region was the lowest of all significantly and medial region was the highest(p0.05). There were no overall differences in the sensitivities of the superior, temporal and inferior regions(p>0.05) and their sensitivities were higher than that of central region and lower than that of medial region. The amount of preoperative myopia and the thickness of corneal flap showed no significant correlation with the decrease of postoperative corneal sensitivity(r0.05).