Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy.

OBJECTIVE: To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry. ANIMALS STUDIED: Sixty eyes of 30 healthy adult horses aged 8-24 years. PROCEDURES: Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pressure (IOP) was estimated using rebound tonometry, and axial globe length was measured using ultrasonographic biometry. RESULTS: CT (mean ± SD µm) measured by UBM was 854 ± 61 (central), 994 ± 58 (superior), 930 ± 57 (temporal), 979 ± 55 (inferior), and 898 ± 48 (nasal). CT measured by UBM was greater than that measured by ultrasonic pachymetry at all locations and was statistically significant at all locations except inferior (p = 0.0006-0.048). No sex nor age effect was detected for CT at any location. The repeatability of ultrasonic pachymetry was superior to that of UBM. Mean ± SD ACD was 5.74 ± 0.41 mm. A weak positive correlation was identified between central CT and IOP and between central CT and axial globe length. CONCLUSIONS: Normal data for CT and ACD of the adult horse obtained using UBM are provided. CT determined by UBM was greater relative to pachymetry at all corneal locations.

The effect of central corneal thickness on intraocular pressure values using various tonometers in the dog.

OBJECTIVE: To compare intraocular pressure readings from three different tonometers, the Tono-Pen AVIA® (TP), TonoVet® (TV) and TonoVet Plus® (TV+) and to determine how measurements from each tonometer are affected by central corneal thickness (CCT). ANIMALS: Ninety dogs. PROCEDURES: Normal dogs and dogs with ocular disease were selected for study inclusion. Central corneal thickness measurements were gathered with the Pachette 4 ultrasonic pachymeter, and IOP measurements were gathered with the three tonometers in random order. ANOVA or Wilcoxon tests were utilized for overall group comparisons. Linear regression analyses were utilized to determine the association between IOP and CCT. RESULTS: When comparing tonometers to each other, for all dogs, readings from the TV+were significantly different compared to the TV (p = <.0001) and TP (p = <.0001); however, there was no significant difference between the TV and the TP (p = .999). Linear regression did not find any significant correlation between corneal thickness and IOP readings with any tonometer when looking at normal dogs or when including dogs with ocular abnormalities. DISCUSSION: This study did not find a significant correlation between an increase in CCT and increase in IOP reading in any tonometer comparison amongst normal and dogs with ocular abnormalities. The TV+produced consistently and significantly higher readings, but measurements did not exceed the expected IOP range in normal dogs. For consistency, the same tonometer should be used when monitoring IOP over time.

A Retrospective Study of Corneal Endothelial Dystrophy in Dogs (1991-2014).

PURPOSE: To retrospectively evaluate the clinical data, diagnostic tests, treatments, and outcomes for dogs with corneal endothelial dystrophy (CED) and determine risk factors for CED when compared with a canine reference population. METHODS: Medical records of 99 dogs (1991-2014) diagnosed with CED at the University of California Davis Veterinary Medical Teaching Hospital were reviewed and compared with 458,680 dogs comprising the general hospital population during the study period. Retrieved data included signalment, examination findings, diagnoses, treatments, and outcomes associated with CED. The exact Pearson χ2 test or exact Kruskal-Wallis test was used to compare parameters between the groups. Progression of corneal edema was assessed using 3 independent Kaplan-Meier curves, identifying clinically significant changes in corneal opacity. RESULTS: Boston terriers, German wirehaired pointers, and Dachshunds were overrepresented in the CED-affected group, whereas Labradors were underrepresented. Dogs older than 11 years were overrepresented in the CED-affected group, whereas intact dogs were underrepresented. Surgical intervention was performed (n = 11) based on the severity of disease and secondary complications from CED. Median time to progression of corneal edema was 1) 368 days when an at-risk eye initially without edema developed edema at a subsequent visit, 2) 701 days when there was progression from mild to marked corneal edema, and 3) 340 days when there was progression from focal to diffuse corneal edema. CONCLUSIONS: Many CED-affected dogs progress over months to years without surgical intervention, making dogs with CED a useful model for studying genetic predispositions and development of novel therapeutics for Fuchs endothelial corneal dystrophy.

A modified technique of keratoleptynsis ("letter-box") for treatment of canine corneal edema associated with endothelial dysfunction.

PURPOSE: To describe a modified keratoleptynsis procedure, as a method of preserving central corneal function, and evaluate the outcome in vision, reduction of corneal thickness and treatment of epithelial corneal ulcers in cases with endothelial cell dysfunction. METHODS: Forty-four dogs (72 eyes) were affected by progressive corneal edema, with or without ulcerative keratitis. All patients were treated with a dorsal and ventral superficial keratectomy followed by conjunctival flaps, maintaining a clear central cornea. Corneal thickness measurements were obtained via ultrasound biomicroscopy. RESULTS: All eyes showed resolution of ocular discomfort postoperatively, with a median time to resolution of 35 days. Two years post-surgery, vision had been lost in 2 of 29 eyes (7%). From the initial population, 23 dogs (39 eyes) had follow-up evaluations of corneal thickness. The mean central corneal thickness was 1359 ± 251 µm prior to surgery. Thickening of the central cornea was observed one week after surgery to 1559 ± 263 µm. Decreased corneal thickness was reported, at 1 month, 4 months, 10 months and 2 years postoperatively (1285 ± 267 µm, 1102 ± 150 µm, 1121 ± 288 µm, 1193 ± 283 µm, respectively). All eyes showed a similar trend of increasing and then decreasing corneal thickness. CONCLUSIONS: This surgical technique provided statistically significant reduction in central corneal thickness and sustained relief of ocular pain. Reduction in corneal thickness appeared to be maintained 2 years post-surgery, and all patients remained comfortable. Superficial corneal pigmentation and fibrosis resulted in vision loss in two eyes.

Comprehensive Clinical, Diagnostic, and Advanced Imaging Characterization of the Ocular Surface in Spontaneous Aqueous Deficient Dry Eye Disease in Dogs.

PURPOSE: To perform a comprehensive clinical, diagnostic, and imaging characterization of the ocular surface in West Highland White Terriers (WHWTs) diagnosed with aqueous deficient dry eye (ADDE) disease. METHODS: Six ADDE-affected and 13 ADDE-unaffected WHWT dogs were enrolled and underwent clinical assessment and disease scoring, tear osmolarity, phenol red thread test, Schirmer tear test, tear film breakup time, fluorescein staining, Rose bengal and lissamine green vital dye staining, meibometry, corneal esthesiometry, ultrasound pachymetry, optical coherence tomography, in vivo confocal microscopy, and conjunctival biopsy. Subjective assessment of their condition was provided by owner-reported surveys. RESULTS: ADDE-affected WHWT dogs had higher median clinical disease (conjunctiva: 5.75 vs. 0.00; cornea: 14.00 vs. 5.00; total: 17.50 vs. 5.00), vital staining (Rose bengal: 2.25 vs. 1.50; lissamine green: 2.00 vs. 1.00), and histologic disease (conjunctiva: 2 vs. 0) scores when compared with the controls. In addition, ADDE-affected WHWTs had significantly lower phenol red thread test (5.0 vs. 17.5, mm/15 s), Schirmer tear test (3 vs. 20, mm/min), tear film breakup time (3.6 vs. 13.9, s) values and higher area under the curve values for meibometry (394 vs. 245, meibometry units [MU]). There were no significant differences in other tear film tests performed. Advanced imaging revealed decreased tear meniscus height (optical coherence tomography) and variable pigment deposition within corneal epithelial cells (in vivo confocal microscopy). CONCLUSIONS: This comprehensive assessment of ADDE-affected WHWTs depicts the ocular surface changes associated with quantitative lacrimal gland dysfunction. Importantly, ADDE-affected WHWTs may prove a valuable naturally occurring ADDE model for investigating underlying pathophysiological mechanisms and the development of novel therapeutics.

Anterior segment parameters measured in young healthy cats using a rotating Scheimpflug camera.

OBJECTIVE: The purpose of this study is to measure parameters of the anterior segment of normal feline eyes using a rotating Scheimpflug camera in young and adult cats. PROCEDURE: Sixteen domestic short-haired (DSH) healthy cats (seven castrated males and nine spayed females) with a mean age of 17 months (SD = 3.5) were anesthetized. Cats were considered immature and adults if they were < or ≥12 months of age, respectively. The keratometric values, the anterior chamber depth (ACD), and central corneal thickness (CCT) of the right eye of each animal were measured using a Pentacam Oculus topographer. The repeatability of the measures was assessed by calculating the coefficient of variation of the successive measures in cats (five repetitions per cat). We performed an ANOVA to test the effect of age on the parameters measures. RESULTS: The mean CCT and ACD were 601.97 ± 38 µm and 5.27 ± 0.04 mm, respectively. No significant differences were observed between adult and young cat's measures. The average keratometric value was 39.6 ± 0.3 D. The mean average cylindrical error was 2.48 ± 0.35 D (43.75% "against-the-rule" astigmatism and 43.75% "oblique" astigmatism). CONCLUSION: The Oculus Pentacam under clinical conditions give CCT and ACD values very similar to those reported in previous studies. Corneal astigmatism measures were markedly elevated (>2 D). Further studies with a larger population of cats of various breeds and ages are needed to confirm or refute these results, using a rotating Scheimpflug camera.

Corneal collagen cross-linking following superficial keratectomy as treatment for corneal endothelial cell dystrophy in dogs: Preliminary clinical study.

OBJECTIVE: To describe the outcome of corneal collagen cross-linking (CXL) combined with superficial keratectomy (SK) as treatment for corneal edema due to corneal endothelial dystrophy (CED) in dogs. ANIMALS STUDIED: Four eyes of four dogs (3 Shih Tzus and 1 English Cocker Spaniel) with corneal edema due to CED were treated with SK and CXL. Two were males, and two were females. PROCEDURE: Depending on corneal thickness, 500-700 µm of edematous cornea was removed by SK. Next, CXL was performed by irradiating the cornea with UVA (365 nm) at 3 mW/cm² irradiance for 30 min after soaking with 0.1% riboflavin in 20% dextran every three minutes for 30 minutes. One drop of riboflavin was instilled every three minutes during irradiation. Slit lamp biomicroscopy and optical coherence tomography were used to examine the cornea during the follow-up period. RESULTS: The corneas had focal to diffuse edema, and the average corneal thickness was 1553 (1282-1900) µm. All corneas showed a significantly reduced corneal thickness and regained marked transparency immediately after treatment; however, the opacity increased as the corneal thickness increased during the follow-up period. Corneal vascularization (n = 4) disappeared within a month. Corneal pigmentation (n = 1) and bullae (n = 1) were observed. All cases showed marked reduction in corneal thickness; however, transparency was improved in only one case. CONCLUSION: Collagen cross-linking with SK has the potential to reduce the corneal thickness in CED cases; however, a lasting clinically significant improvement of corneal transparency seems unlikely. As the added benefit of CXL to the SK procedure is unclear based on the results of this study, combined treatment of CXL and SK for the treatment of corneal edema caused by CED is currently not recommended in dogs.

Comparison of ultrasonic pachymetry and Fourier-domain optical coherence tomography for measurement of corneal thickness in dogs with and without corneal disease.

Several ultrasonic and Fourier-domain optical coherence tomography (FD-OCT) pachymeters are used to measure corneal thickness in canine patients and research subjects. This study assessed the reliability of and consistency between two ultrasonic pachymetry (USP) devices, Pachette 3 and Accupach VI, as well as automated and manual measurements obtained using FD-OCT in dogs with and without corneal disease. Corneal thickness measurements were compiled from 108 dogs and analyzed using mixed effects linear regression, with Bonferonni adjustments for post-hoc comparisons, to determine the effects of age, weight and disease state. Data are presented as predicted mean±standard error. Canine corneal disease can result in marked increases in thickness that frequently exceed the upper limits of measurement of some pachymetry devices developed for human use. In this study, the corneas of dogs with endothelial disease or injury frequently exceeded the upper limits of quantitation of 999 and 800µm for the Accupach VI and automated FD-OCT pachymeters, respectively. Using values <800µm, the Pachette 3 generated significantly greater values for central corneal thickness (CCT) than the Accupach VI, manual FD-OCT and automated FD-OCT at 625±7.0, 615±7.2, 613±7.2, and 606±7.4µm respectively (P<0.001). Of the two devices where measurements >1000µm were obtained, manual FD-OCT demonstrated less variability than the Pachette 3. Corneal thickness increased linearly with age and weight with an increase of 6.9±1.8µm/year and 1.6±0.8µm/kg body weight (P<0.005 and P=0.038, respectively).

Comparison of central corneal thickness in dogs measured by ultrasound pachymetry and ultrasound biomicroscopy.

Ultrasound pachymetry (UP) is currently the most common technique used to evaluate central corneal thickness (CCT). New devices which allow assessment of CCT without corneal contact have been compared, but there are discrepancies among instruments. The aim of this study was to compare CCT measurements obtained by UP and ultrasound biomicroscopy (UBM) in 28 eyes of 14 healthy Beagles dogs. Mean CCT±standard deviation (SD) were 552±63µm for UP and 551±55µm for UBM. UBM showed both a fixed and proportional bias when compared to ultrasound pachymetry, but this was not considered to be clinically important. Measured CCT did not differ between UP and UBM (P=0.796). The intra-class correlation coefficient indicated a strong agreement between methods (0.990). The CCT measurements between left (548±61µm) and right (555±59µm) eyes did not differ (P=0.760). Male dogs had higher CCT measurements than female dogs (P=0.038).

Comparison of corneal thickness measurements using ultrasound pachymetry, ultrasound biomicroscopy, and digital caliper in frozen canine corneas.

OBJECTIVE: To evaluate the clinical efficacy among ultrasound pachymetry (UP), ultrasound biomicroscopy (UBM), and manual measurement (MM) with digital caliper by comparing corneal thickness (COT) values obtained from frozen canine corneas ex vivo. PROCEDURES: COT was measured using UP, UBM, and MM in eight enucleated normal canine eyes frozen at -20 °C for 4 weeks. After thawing at room temperature for 2 h, the COT values were obtained from five sites on each cornea: central corneal thickness (CCOT), thickness at the 3, 6, 9, and 12 o'clock positions (3COT, 6COT, 9COT, and 12COT, respectively). For each device, measurements were performed three times at each designated site by one operator. Intraclass correlation coefficient, repeated-measures analysis of variance, and Bland-Altman plot were performed for statistical analyses. RESULTS: The mean CCOT was 839.0 ± 138.2, 857.6 ± 127.9, and 849.1 ± 132.8 µm for UP, UBM, and MM, respectively. There was no statistically significant difference among the measurements by all three devices (P > 0.05). The statistical agreement among these devices was also shown to be good according to Bland-Altman plots. In addition, the values measured on the peripheral sites of the cornea (3COT, 6COT, 9COT, and 12COT) also revealed no significant differences among the three devices. The difference between CCOT and peripheral corneal thickness was also statistically insignificant. CONCLUSIONS: The UP, UBM, and MM measurements showed statistically similar COT values. The UBM and UP provided accurate and reliable measurements comparable to MM and could be used effectively for clinical COT measurements.

Phenotypic Characterization of Corneal Endothelial Dystrophy in German Shorthaired and Wirehaired Pointers Using In Vivo Advanced Corneal Imaging and Histopathology.

PURPOSE: To evaluate corneal morphology using ultrasonic pachymetry (USP), Fourier-domain optical coherence tomography (FD-OCT), and in vivo confocal microscopy (IVCM) in 2 related canine breeds-German shorthaired pointers (GSHPs) and German wirehaired pointers (GWHPs)-with and without corneal endothelial dystrophy (CED). This condition is characterized by premature endothelial cell degeneration leading to concomitant corneal edema and is similar to Fuchs endothelial corneal dystrophy. METHODS: Corneas of 10 CED-affected (4 GSHP and 6 GWHP) and 19 unaffected, age-matched (15 GSHP and 4 GWHP) dogs were examined using USP, FD-OCT, and IVCM. A 2-sample t test or Mann-Whitney rank-sum test was used to statistically compare parameters between both groups. Data are presented as mean ± SD or median (range). RESULTS: Central corneal thickness determined using USP was significantly greater in CED-affected than in unaffected dogs at 1179 (953-1959) and 646 (497-737) µm, respectively (P < 0.001). Central epithelial thickness was found to be significantly decreased in CED-affected versus unaffected dogs at 47 ± 7.1 and 55 ± 7.1 µm, respectively (P = 0.011), using FD-OCT. With IVCM, corneal endothelial density was significantly less (P < 0.001) in 5 dogs with CED versus 19 unaffected controls at 499 ± 315 versus 1805 ± 298 cells/mm, respectively. CED-affected dogs exhibited endothelial pleomorphism and polymegethism, whereas CED-unaffected dogs had regular hexagonal arrangement of cells. CONCLUSIONS: GSHPs and GWHPs with CED exhibit marked differences in corneal morphology when compared with age-matched control dogs. These 2 CED-affected breeds represent spontaneous, large animal models for human Fuchs endothelial corneal dystrophy.

Canine central corneal thickness measurements via Pentacam-HR® , optical coherence tomography (Optovue iVue® ), and high-resolution ultrasound biomicroscopy.

OBJECTIVE: To compare central corneal thickness (CCT) values in canine eyes using Pentacam-HR® Scheimpflug imaging (Pentacam), Optovue® iVue spectral-domain optical coherence tomography (SD-OCT), and high-resolution ultrasound biomicroscopy (UBM) and generate normative canine Pentacam CCT values. ANIMALS STUDIED: Twenty-four client-owned dogs (37 eyes) with nondiseased cornea(s) presenting to the Colorado State University Veterinary Teaching Hospital. PROCEDURES: Corneal images were acquired via Pentacam, SD-OCT, and UBM in the listed order. Machine-calculated values of CCT from Pentacam and SD-OCT were compared to operator-measured values from UBM. Bland-Altman analysis was performed to evaluate agreement between instruments. RESULTS: Mean CCT ± SD measured by Pentacam was 629.73 ± 64.57 µm, by SD-OCT was 610.56 ± 57.48 µm, and by UBM was 689.77 ± 55.93 µm. On average, Pentacam CCT was 19.17 ± 32.90 µm (3%) thicker than SD-OCT and 65.12 ± 44.52 µm (10.3%) thinner than UBM. SD-OCT was on average 82.47 µm (13.5% ) thinner than UBM. The 95% limits of agreement were (-45.31, 83.65), (-152.38, 22.13), and (-126.674, -38.270) for Pentacam vs. SD-OCT, Pentacam vs. UBM, and SD-OCT vs. UBM respectively. All differences were statistically significant (P < 0.01). CONCLUSIONS: Considering there is an average of 7.5% normal diurnal variation in canine CCT, a 3.0% difference between Pentacam and SD-OCT values is likely not clinically relevant. However, Pentacam measurements were both statistically and clinically significantly different from UBM and SD-OCT measurements.

Corneal thickness of eyes of healthy goats, sheep, and alpacas manually measured by use of a portable spectral-domain optical coherence tomography device.

OBJECTIVE To determine corneal thickness of eyes of healthy goats, sheep, and alpacas by use of a portable spectral-domain optical coherence tomography (SD-OCT) device and evaluate intraoperator reliability for measurements. ANIMALS 11 female goats, 10 female sheep, and 11 (4 males and 7 females) alpacas. PROCEDURES Each animal was sedated, and gentle manual restraint was used to ensure proper positioning of the head and globe. Corneal pachymetry was performed (in triplicate) with a portable SD-OCT device on both eyes of each animal. All corneal measurements were obtained manually by use of the integrated caliper function. Corneal epithelial thickness (CET), corneal stromal thickness (CST), Descemet membrane thickness (DMT), and total corneal thickness (TCT) were measured twice on each image, and a mean value was calculated. RESULTS Mean ± SD values for CET, CST, DMT, and TCT were 96.1 ± 5.0 µm, 486.0 ± 10.3 µm, 36.8 ± 4.8 µm, and 616.9 ± 7.1 µm, respectively, for the goats; 111.6 ± 5.7 µm, 599.8 ± 10.0 µm, 31.0 ± 4.5 µm, and 741.1 ± 9.9 µm, respectively, for the sheep; and 147.4 ± 5.7 µm, 446.1 ± 7.4 µm, 44.5 ± 5.0 µm, and 634.8 ± 6.2 µm, respectively, for the alpacas. Intraclass correlations ranged from 0.49 to 0.83 for CET, CST, and TCT and from 0.13 to 0.36 for DMT. CONCLUSIONS AND CLINICAL RELEVANCE SD-OCT provided manual measurement of corneal thickness (CET, CST, and TCT) with clinically acceptable intraoperator reliability for eyes of healthy goats, sheep, and alpacas.

Superficial Keratectomy and Conjunctival Advancement Hood Flap (SKCAHF) for the Management of Bullous Keratopathy: Validation in Dogs With Spontaneous Disease.

PURPOSE: To evaluate the efficacy of superficial keratectomy and conjunctival advancement hood flap (SKCAHF) for the treatment of bullous keratopathy in canine patients. METHODS: Nine dogs (12 eyes) diagnosed with progressive corneal edema underwent superficial keratectomy followed by placement of conjunctival advancement hood flaps. The canine patients were examined pre- and postoperatively using in vivo confocal microscopy, ultrasonic pachymetry (USP), and Fourier-domain optical coherence tomography (FD-OCT). All owners responded to a survey regarding treatment outcomes. RESULTS: Mean central corneal thickness (CCT) as measured by FD-OCT was 1163 ± 290 µm preoperatively and significantly decreased postoperatively to 795 ± 197 µm (P = 0.001), 869 ± 190 µm (P = 0.005), and 969 ± 162 µm (P = 0.033) at median postoperative evaluations occurring at 2.2, 6.8, and 12.3 months, respectively. Owners reported significant improvement (P < 0.05) in vision and corneal cloudiness at 6.8 and 12.3 months postoperatively. The percentage of cornea covered by the conjunctival flap was correlated (P = 0.0159) with a reduction in CCT by USP at 12.3 months postoperatively. All canine patients were comfortable pre- and postoperatively. CONCLUSIONS: SKCAHF results in a reduction of corneal thickness in canine patients with bullous keratopathy. The increase in corneal thickness over time, after performing SKCAHF, is likely because of progressive endothelial decompensation. This surgery is a potentially effective intervention for progressive corneal edema in dogs that may have value in treatment of human patients with bullous keratopathy.

Comparison between Pentacam-HR and optical coherence tomographycentral corneal thickness measurements in healthy feline eyes.

OBJECTIVES: To measure the central corneal thickness (CCT) in healthy feline eyes with Scheimpflug imaging (Pentacam, Pentacam(®) -HR) and to compare these values with those obtained with spectral-domain optical coherence tomography (OCT, Optovue(®) iVue). ANIMALS STUDIED: Thirty one sedated Domestic Short-haired cats. PROCEDURES: Two repeated CCT measurements were obtained from both eyes using Pentacam measured at the pupil center and corneal apex (CCTpupil and CCTapex ) and using SD-OCT (CCTOCT ). Agreement between the imaging modalities for CCT and intradevice repeatability was evaluated with Bland-Altman analysis. Mixed modeling was used to test for a difference between methods. RESULTS: The calculated mean ± SD CCT was CCTOCT  = 584.93 ± 39.05 µm, CCTpupil  = 608.25 ± 47.26 µm, and CCTapex  = 606.41 ± 44.18 µm. There was a statistically significant difference between CCTOCT vs. CCTpupil (P < 0.0007) and CCTOCT vs. CCTapex (P < 0.0003) (n = 59 eyes). The 95% limits of agreement (LoA) for CCTOCT vs. CCTpupil was (-89.57 µm, 40.04 µm) and for CCTOCT vs. CCTapex was (-79.62 µm, 33.79 µm) (n = 59 eyes). 95% LoA between repeated CCT measurements by SD-OCT was (-10.23 µm, 9.32 µm) and by Pentacam was (-22.66 µm, 18.30 µm) at pupil and (-15.81 µm, 16.17 µm) at corneal apex (n = 11 eyes). CONCLUSIONS: SD-OCT and Pentacam provide excellent CCT measurement repeatability. Pentacamapex is our recommended clinical setting for use of the Pentacam. The level of agreement between SD-OCT and Pentacam for CCT is good.

Comparación de las características corneales en gallina y codorniz como modelos experimentales de cirugía refractiva / Comparison of the characteristics in hen and quail corneas as experimental models of refractive surgery

OBJETIVO: Analizar y comparar la histología, la morfología y las medidas biofísicas corneales de la gallina y la codorniz para determinar qué modelo experimental animal es el más adecuado para la realización de estudios de investigación en cirugía corneal. MATERIAL Y MÉTODOS: Se estudiaron las medidas biofísicas de la córnea (curvatura, espesor, refracción y longitud axial) de 20 animales (10 gallinas y 10 codornices). Después las córneas fueron procesadas para el estudio de histología clásica bajo la luz del microscopio. RESULTADOS: Los 2 grupos analizados poseen una córnea similar a la del humano con respecto al número de capas y con una evidente capa de Bowman. El espesor corneal, así como la longitud axial del ojo de la gallina, 225,3 ± 18,4 μm y 12,8 ± 0,25 mm, respectivamente, fueron significativamente mayores que los de la codorniz (p < 0,01 y p < 0,001). El radio de curvatura de la córnea central de la gallina también fue significativamente mayor que el de la codorniz (p < 0,001). El poder refractivo de las 2 especies fue similar. La proporción del espesor estromal con relación a la córnea en la gallina fue más similar al humano (82,6%) que de la codorniz (72,5%). La densidad de la población de queratocitos en la gallina, 8,57 ± 1,49/5.000 μm2, correspondió a cerca de la mitad del número de queratocitos encontrados en la córnea de la codorniz (p < 0,005). CONCLUSIONES: La córnea de gallina, por su tamaño, espesor del estroma y similitud de proporción en sus capas con la córnea humana, es más adecuada para la cirugía refractiva corneal que la de codorniz

AIM: To compare the histological, morphological and the biophysical measurements between hen and quail corneas, in order to determine which of them were better suited for use as an animal model for research into corneal refractive surgery. MATERIAL AND METHODS: A study was performed using the biophysical measurements of the cornea (curvature, thickness, refraction, and axial length) of 20 animals (10 hens and 10 quails). The corneas were then prepared for histological analysis under microscopy light. RESULTS: The analysis showed that both groups have the same number of corneal layers as the human cornea and with an evident Bowman's layer. The thickness of the hen cornea and axial length of the eye, 225.3 ± 18.4 μm and 12.8 ± 0.25 mm, respectively, were larger than that of the quail (P < .01 andP < .001, respectively). The radius of curvature for the hen central cornea, 3.65 ± 0.08 mm, was greater than that for the quail (P < .001), but the refractive power of each cornea was similar. The proportion of total corneal thickness of the hen stroma, 82.6%, was more similar to that of the human than was the quail stroma, 72.5%. Within the hen stroma, the density of keratocytes, 8.57 ± 1.49 per 5,000 μm2, was about half that in the quail stroma (P < .005). CONCLUSIONS: Because of the large size of the hen cornea, the stromal thickness and proportional similarity of the corneal layers with human cornea, the hen maybe better than the quail as an alternative species suitable for use in studies of corneal refractive surgery

Ophthalmic variables in rehabilitated juvenile Kemp's ridley sea turtles (Lepidochelys kempii).

OBJECTIVE: To determine central corneal thickness (total corneal thickness [TCT], epithelial thickness [ET], and stromal thickness [ST]), anterior chamber depth (ACD), and intraocular pressure (IOP) in Kemp's ridley sea turtles (Lepidochelys kempii). DESIGN: Prospective cross-sectional study. ANIMALS: 25 healthy rehabilitated juvenile Kemp's ridley sea turtles. PROCEDURES; Body weight and straight-line standard carapace length (SCL) were recorded. All turtles underwent a complete anterior segment ophthalmic examination. Central TCT, ET, ST, and ACD were determined by use of a spectral-domain optical coherence tomography device. Intraocular pressure was determined with a rebound tonometer; the horse setting was used to measure IOP in all 25 turtles, and the undefined setting was also used to measure IOP in 20 turtles. For each variable, 3 measurements were obtained bilaterally. The mean was calculated for each eye and used for analysis purposes. RESULTS: The mean ± SD body weight and SCL were 3.85 ± 1.05 kg (8.47 ± 2.31 lb) and 29 ± 3 cm, respectively. The mean ± SD TCT, ET, ST, and ACD were 288 ± 23 µm, 100 ± 6 µm, 190 ± 19 µm, and 581 ± 128 µm, respectively. Mean ± SD IOP was 6.5 ± 1.0 mm Hg when measured with the horse setting and 3.8 ± 1.1 mm Hg when measured with the undefined setting. CONCLUSIONS AND CLINICAL RELEVANCE: Results provided preliminary reference ranges for objective assessment of ophthalmic variables in healthy juvenile Kemp's ridley sea turtles.

Comparison of the characteristics in hen and quail corneas as experimental models of refractive surgery. / Comparación de las características corneales en gallina y codorniz como modelos experimentales de cirugía refractiva.

AIM: To compare the histological, morphological and the biophysical measurements between hen and quail corneas, in order to determine which of them were better suited for use as an animal model for research into corneal refractive surgery. MATERIAL AND METHODS: A study was performed using the biophysical measurements of the cornea (curvature, thickness, refraction, and axial length) of 20 animals (10 hens and 10 quails). The corneas were then prepared for histological analysis under microscopy light. RESULTS: The analysis showed that both groups have the same number of corneal layers as the human cornea and with an evident Bowman's layer. The thickness of the hen cornea and axial length of the eye, 225.3±18.4µm and 12.8±0.25mm, respectively, were larger than that of the quail (P<.01 and P<.001, respectively). The radius of curvature for the hen central cornea, 3.65±0.08mm, was greater than that for the quail (P<.001), but the refractive power of each cornea was similar. The proportion of total corneal thickness of the hen stroma, 82.6%, was more similar to that of the human than was the quail stroma, 72.5%. Within the hen stroma, the density of keratocytes, 8.57±1.49 per 5,000µm(2), was about half that in the quail stroma (P<.005). CONCLUSIONS: Because of the large size of the hen cornea, the stromal thickness and proportional similarity of the corneal layers with human cornea, the hen maybe better than the quail as an alternative species suitable for use in studies of corneal refractive surgery.

In vivo evaluation of the cornea and conjunctiva of the normal laboratory beagle using time- and Fourier-domain optical coherence tomography and ultrasound pachymetry.

OBJECTIVE: To obtain normative data for the canine cornea and conjunctiva using high-resolution time- and Fourier-domain optical coherence tomography (TD-OCT and FD-OCT) and ultrasound pachymetry (USP). ANIMALS: One hundred sixty-eight eyes of 133 healthy young intact laboratory beagles. PROCEDURES: The cornea and conjunctiva of 16 eyes of 8 healthy young intact female beagles were imaged using FD-OCT. Corneal thickness was measured with FD-OCT and USP, while corneal epithelial thickness and conjunctival epithelial thickness were measured with FD-OCT. The central corneal thickness (CCT) was determined in 152 eyes of 125 healthy young adult intact female (35) and male (90) beagles using TD-OCT. Mixed effects linear regression was used for statistical analysis. RESULTS: The CCT was (mean ± standard deviation) 497.54 ± 29.76, 555.49 ± 17.19, and 594.81 ± 33.02 µm as measured by FD-OCT, USP, and TD-OCT, respectively. The central, superior paraxial, superior perilimbal corneal epithelial thickness and superior bulbar conjunctival epithelial thickness were 52.38 ± 7.27, 56.96 ± 6.47, 69.06 ± 8.84 and 42.98 ± 6.17 µm, respectively. When comparing techniques used for measuring CCT (USP vs. FD-OCT and FD-OCT vs. TD-OCT), USP and TD-OCT generated significantly greater values in comparison with FD-OCT (both P < 0.001). For all dogs, CCT increased with increasing age and body weight (both P < 0.001) and was higher in intact males vs. females using TD-OCT (P = 0.034). CONCLUSION: High-resolution FD-OCT and TD-OCT provide detailed noninvasive evaluation of in vivo canine anterior segment structures. Normative values of the canine cornea and conjunctiva are reported.

Ocular dimensions, corneal thickness, and corneal curvature in quarter horses with hereditary equine regional dermal asthenia.

OBJECTIVES: The aim of this study was to compare ocular dimensions, corneal curvature, and corneal thickness between horses affected with hereditary equine regional dermal asthenia (HERDA) and unaffected horses. ANIMALS: Five HERDA-affected quarter horses and five healthy control quarter horses were used. METHODS: Schirmer's tear test, tonometry, and corneal diameter measurements were performed in both eyes of all horses prior to ophthalmologic examinations. Ultrasonic pachymetry was performed to measure the central, temporal, nasal, dorsal, and ventral corneal thicknesses in all horses. B-mode ultrasound scanning was performed on both eyes of each horse to determine the dimensions of the ocular structures and to calculate the corneal curvature. RESULTS: Each corneal region examined in this study was thinner in the affected group compared with the healthy control group. However, significant differences in corneal thickness were only observed for the central and dorsal regions. HERDA-affected horses exhibited significant increases in corneal curvature and corneal diameter compared with unaffected animals. The ophthalmologic examinations revealed mild corneal opacity in one eye of one affected horse and in both eyes of three affected horses. No significant between-group differences were observed for Schirmer's tear test, intraocular pressure, or ocular dimensions. CONCLUSIONS: Hereditary equine regional dermal asthenia-affected horses exhibit decreased corneal thickness in several regions of the cornea, increased corneal curvature, increased corneal diameter, and mild corneal opacity. Additional research is required to determine whether the increased corneal curvature significantly impacts the visual accuracy of horses with HERDA.