Endothelial cell density and characterization of corneal endothelial cells in the Tawny Owl (Strix aluco) using specular microscopy.

OBJECTIVE: To determine endothelial cell density (ECD) and morphology and morphometry of corneal endothelial cells in the tawny owl (Strix aluco), as well as to report the effects of aging on these parameters. ANIMAL STUDY AND PROCEDURES: Twenty tawny owls were included in the study and classified into 2 groups according to their age: fledglings (<1 year old) and adults (>1 year old). Central corneal endothelium was studied by means of noncontact specular microscopy (Specular Microscope SP-2000P; Topcon, Tokyo, Japan), and results for ECD (cells/mm2 ), mean cell area ((MCA (µm2 )), polymegathism (CV), and pleomorphism (% hexagonal cells) were obtained. Results are described by median, interquartile range (25th, 75th percentiles), and absolute range for ECD, MCA, pleomorphism, and polymegathism. In addition, inferential analyses by Mann-Whitney U test were also performed. A two-tailed Type I error of 5% was established. RESULTS: Results in fledglings were as follows: ECD = 2864 cells/mm2 , MCA = 348 µm2 , % hexagonal cells = 72.75%, and CV = 21. Results in adults were as follows: ECD = 2602 cells/mm2 , MCA = 384 µm2 , % hexagonal cells = 78.83%, and CV = 16. No significant differences in ECD and MCA were seen between the groups (P > .05), although there were significant differences in % hexagonal cells and CV (P < .05). CONCLUSIONS: Tawny owls present a uniform endothelium in cell size and shape, although ECD and MCA differ greatly from other bird species. Differences in ECD and MCA could not be found between fledglings and adults probably because of the youth of adult specimens, although there were differences in pleomorphism and polymegathism.

A dose-escalation ex vivo study on the effects of intracameral benzalkonium chloride in rabbits.

BACKGROUND: Rabbits are currently not a good model for studying diseases of the corneal endothelium because their corneal endothelial cells (CECs) maintain a high proliferative capacity throughout almost all their life. Addressing this particular feature might allow the use of this species for such a purpose. The aim of this study was to evaluate the corneal endothelial injury after intracameral benzalkonium chloride (BAC) injection into rabbit eyes ex vivo, and to establish the most suitable starting dose for an in vivo study aimed at developing an animal model of corneal endothelial disease. RESULTS: Forty rabbit eyes obtained postmortem by transconjunctival enucleation were divided into 8 groups according to the injected compound: Control (no injection), BSS, and increasing BAC concentrations (0.005%, 0.01%, 0.025%, 0.05%, 0.1% and 0.2%). At 0, 6, 24 and 48 h, ophthalmologic examination of the anterior segment, pachymetry and specular microscopy were performed, and corneas were finally vital-stained and observed under the light microscope to assess the CECs morphology and mortality rate. When compared to BSS, CECs density started to decrease significantly at 0.025% BAC concentration, while mean cell area, corneal edema and corneal thickness began to increase significantly at 0.05%, 0.005% and 0.1% BAC concentrations, respectively. Concentrations of 0.05% BAC and above caused significant increases in CECs pleomorphism (decreased hexagonality) and mortality, compared to control and BSS. CONCLUSIONS: Ex vivo intracameral BAC injection induces corneal endothelial toxicity in rabbits. However, confirmatory in vivo studies are required to develop the desired model, with 0.05% BAC being a suggested starting point.

Effects of age and breed on corneal thickness, density, and morphology of corneal endothelial cells in enucleated sheep eyes.

OBJECTIVE: The purpose of the study was to determine corneal thickness (CT), endothelial cell density (ECD), morphology, and morphometry in ovine eyes, and to report the effects of age and breed on these parameters. ANIMALS STUDIED AND PROCEDURES: Forty-eight healthy ovine eyes were classified into six groups (eight eyes per group) according to animals' age (lambs and adults) and breed (Manchega, Ripollesa, and Rasa Aragonesa). Endothelial cell density (cells/mm(2) ) and CT (µm) were calculated in the central cornea and four peripheral quadrants by means of specular microscopy. Mean cell area (MCA (µm(2) )), pleomorphism (% hexagonal cells), and polymegethism (CV) were evaluated in the central cornea. Statistics consisted of an ANOVA model and a LSD test for the post hoc analysis. RESULTS: Results in lambs were as follows: ECD = 3532 ± 259, CT = 699 ± 56, MCA = 283 ± 22, % hexagonal cells = 75.64 ± 3.09, and CV = 18 ± 8.4; and in adults: ECD = 2204 ± 261, CT = 804 ± 87, MCA = 473 ± 53, % hexagonal cells = 69.9 ± 3.42, and CV = 18.1 ± 5.2. There were differences (P < 0.001) in all parameters studied between both groups except for the CV (P = 0.962). Regarding the breed, Rasa Aragonesa presented a higher CT (P = 0.001) and CV (P = 0.04) compared to other breeds. Mean values of all groups together showed that central and dorsal areas of the cornea were the thickest, whereas temporal quadrant was the thinnest (P < 0.001). CONCLUSIONS: This study demonstrates that age and breed influence corneal and endothelial parameters in sheep.

Effect of topical 1% cyclopentolate hydrochloride on tear production, pupil size, and intraocular pressure in healthy Beagles.

OBJECTIVE: The objective of the study was to evaluate the effect of topical 1% cyclopentolate hydrochloride (CH) on tear production (TP), pupil size (PS), and intraocular pressure (IOP) in dogs. ANIMAL STUDIED: Fifteen healthy beagle dogs from the UAB research-teaching colony. PROCEDURE: Dogs without ocular diseases were included. Each animal received one drop of 1% CH ophthalmic solution in a randomly selected eye. TP, PS, and IOP were evaluated by means of STT-1, static pupillometry, and rebound tonometry, respectively. Evaluations were performed before drug instillation and at 0.5, 1, 2, 4, 8, 12, 24, 30, 36, 48, 54, 60, 72, 84, and 96 h postinstillation. Examinations took place in a room with fixed light intensity (40-55 lux). Statistical analysis was performed by means of generalized estimating equations for the effect on STT-1, pupil size, and IOP over time. RESULTS: After unilateral application of 1% CH, significant pupillary dilation started at 30 min, reached its maximum at 12 h, and returned to pre-instillation size after 72 h. No significant effects were found on TP or IOP, at any time. No effects were observed in the untreated eye on any of the parameters evaluated. CONCLUSION: Cyclopentolate hydrochloride could be considered a therapeutic alternative when use of a cycloplegic drug is needed and effects on tear production and IOP are unwanted.

Corneal thickness, endothelial cell density, and morphological and morphometric features of corneal endothelial cells in goats.

OBJECTIVE To determine corneal thickness (CT), endothelial cell density (ECD), and morphological and morphometric features of caprine eyes and to assess effects of aging on these variables. SAMPLE 27 healthy eyes of 19 Murciano-Granadina goats. PROCEDURES Goats were classified into 2 age groups (kids, 14 months old [14 eyes]; and adults, 7 to 10 years old [13 eyes]). The ECD and CT were calculated in the central cornea and 4 peripheral quadrants. Mean cell area (MCA), pleomorphism (percentage of hexagonal cells), and polymegathism were evaluated in the central cornea. RESULTS Median values for kids were determined for ECD (3,831 cells/mm2; inter-quartile [25th to 75th percentile] range [IQR], 3,669 to 4,011 cells/mm2), CT (608 µm; IQR, 573 to 655 µm), MCA (255 µm2; IQR, 243 to 272 µm2), pleomorphism (80.53%; IQR, 78.83% to 83.30%), and polymegathism (19; IQR, 18 to 22). Median values for adults were determined for ECD (2,101 cells/mm2; IQR, 1,966 to 2,251 cells/mm2), CT (706 µm; IQR, 670 to 730 µm), MCA (466 µm2; IQR, 425 to 507 µm2), pleomorphism (67.80%; IQR, 65.50% to 70.00%), and polymegathism (21; IQR, 15 to 26). Values differed significantly between the 2 groups for all variables, except polymegathism. For both groups, the dorsal and temporal quadrants were the thickest and thinnest, respectively. Ventral ECD was the lowest for both groups. CONCLUSIONS AND CLINICAL RELEVANCE ECD decreased with age, whereas MCA, pleomorphism, and CT increased. Moreover, differences among regions of the cornea indicated that the central cornea should not be considered as representative of the entire cornea.