Time-specific intraocular pressure curves in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension.

OBJECTIVE: To detect and categorize time-specific variations in daytime intraocular pressure (IOP) found in Rhesus monkeys with laser-induced ocular hypertension. PROCEDURES: Ten male monkeys with argon laser-induced ocular hypertension in one eye were anesthetized with ketamine hydrochloride, and the IOP measured in both eyes at 7 a.m., 7.30 a.m., and then hourly until 1 p.m. with a Tonopen trade mark XL applanation tonometer. Intraocular pressure time profiles for both eyes in each animal were developed. The means +/- SD of the IOPs for both eyes were calculated for the whole 6-h study period, and the values compared statistically. The difference between the lasered eye mean IOP standard deviation and the normal eye mean IOP standard deviation for each animal during the 6-h follow-up was also calculated and compared. RESULTS: Mean IOP (+/- SD) in the glaucoma and normal eyes for the 10 animals during the 6-h study was 32.6 +/- 2.5 and 14.9 +/- 2.5 mmHg, respectively. The IOP was significantly higher in the experimental eye than in the normal eye (P = 0.0008). The mean IOP in the lasered eye did not significantly change during the study period, whereas a slight but significant increase in IOP of the normal eye over the study period was recorded (P = 0.003). The variance in IOP in the hypertensive eyes was considerably greater than that in the untreated control eyes. From 7 a.m. to 1 p.m. the IOP declined in five eyes and increased in the other five eyes with laser-induced ocular hypertension. CONCLUSIONS: The time-specific IOP variation pattern in the daytime in the laser treated eyes is significantly greater than the variation in the normotensive eyes. This shows that in order to detect statistical differences between IOP variations induced by an IOP-reducing drug, and the exaggerated spontaneous IOP variations present in the laser-induced hypertensive eye, sufficient animals should be included in any study. Understanding the time-specific IOP variation present in a group of monkeys with laser-induced ocular hypertension is essential prior to using the model for the evaluation of IOP-reducing drugs.

Corneal thickness and endothelial cell density measured by non-contact specular microscopy and pachymetry in Rhesus macaques (Macaca mulatta) with laser-induced ocular hypertension.

PURPOSE: Sustained increase in intraocular pressure (IOP) in humans results in a loss of corneal endothelial cells and an increase of corneal thickness. The effects of chronically elevated IOP on the corneal endothelium of monkeys with laser-induced ocular hypertension, a commonly used animal model of human glaucoma have not been documented. This study examined the central corneal thickness (CCT), the corneal endothelial cell density (ECD), and the corneal endothelial cell size (ACS) in Rhesus monkeys with experimental ocular hypertension. Materials and methods. Ten male monkeys with argon laser-induced ocular hypertension in one eye for an average duration of 2.4+/-0.7 years, were sedated with ketamine hydrochloride, and the CCT, ECD, and ACS measured at the center of the cornea of both eyes with a Topcon SP-2000P non-contact specular microscope (Topcon America Corporation((R)), Paramus, NJ, USA). CCT was also measured using a DHG-500 Pachette ultrasonic pachymeter (DHG Technology Inc., Exton, PA, USA). Mean and standard deviation (S.D.) of CCT, ECD and ACS for each eye was calculated and statistically compared.Results. Mean CCT in the hypertensive and normal eyes measured by specular microscopy was 0.477+/-0.023mm and 0.468+/-0.020 mm, respectively. Mean ECD in the hypertensive and normal eyes was 2601.7+/-631.8 and 3990.2+/-402.9 cells mm(-2), respectively. The mean size of the endothelial cells was 252.4+/-23.9 micro m(2) in the normal eye and 408.7+/-115.0 microm m(2) in the hypertensive eye. No significant difference in the measurement of CCT was observed between the specular microscope and the pachymeter (p=0.46). No significant difference in the mean CCT was observed between the two eyes (p=0.4820), whereas the mean ECD was significantly lower in the hypertensive eye than in the normal eye (p<0.001). The ECD was inversely related to the length of IOP elevation (p<0.001). CONCLUSIONS: No difference in the corneal thickness measurement was observed between the specular microscopy and the pachymetry techniques. Chronic ocular hypertension did not significantly affect the CCT, but caused a significant loss of endothelial cells in the center of the cornea of the laser treated eyes compared to the normotensive eyes. The duration of elevated IOP was the most important factor affecting the ECD.

Merkel cell carcinoma of the abdominal wall.

Merkel cell carcinoma is a rare highly malignant tumour. There have been previous descriptions of the CT appearances of this tumour, but to our knowledge this is the first MRI description. MRI may be a more sensitive method of initial evaluation of the local extension of the primary tumour.

Diurnal intraocular pressure curves in healthy rhesus macaques (Macaca mulatta) and rhesus macaques with normotensive and hypertensive primary open-angle glaucoma.

PURPOSE: The authors identify any diurnal intraocular pressure (IOP) variation in healthy Cayo Santiago macaques, as well as Cayo Santiago macaques with normotensive and hypertensive primary open-angle glaucoma (POAG), to further evaluate their potential value as a model for human POAG. METHODS: Twenty-four monkeys (eight animals each of the healthy control, normotensive glaucoma, and hypertensive glaucoma groups) were sedated with ketamine hydrochloride and the IOP measured hourly from 8:00 AM until 3:00 PM with a Tonopen XL applanation tonometer (Mentor, Norwell, MA, U.S.A.). Mean IOP time profiles, mean IOPs at each observation time, and linear trends in mean IOP over time were compared among groups. Intraocular pressure rate-of-change over time and residual variation about the regression line for each individual eye were analyzed. Cup/disc ratio (C/D) was compared with baseline IOP, IOP profile mean and slope, and IOP residual variation. RESULTS: A significant group and time effect on mean IOP (p = 0.0001 and 0.011, respectively), with highest values at 2:00 PM or 3:00 PM, and a significant increasing linear trend in mean IOP over time in the hypertensive group were observed (p = 0.012). Intermediate readings between control and hypertensive mean IOPs were identified for the normotensive glaucoma group. The biggest range of IOP variation was found in the hypertensive glaucoma monkeys. Higher variations in IOP did not lead to an increase in C/D. CONCLUSIONS: This study provides evidence that the Cayo Santiago macaques are a valuable model for human normotensive and hypertensive POAG.