The Central Retinal Artery and Regression of the Hyaloid Artery in Perinatal Cattle

B-Scan Biometry and Color Doppler Ultrasound Imaging of the Eye in Clinically Normal Donkeys (Equus asinus): Effect of Laterality, Maturity and Gender

Despite the extensive research on ocular ultrasonography, there is paucity of information regarding ocular biometry and color Doppler imaging of the donkey's eye. This study establishes B-scan ocular biometry and color Doppler ultrasonographic reference values in normal donkeys and describes effect of laterality, maturity and gender on ocular biometry and vasculature. Forty (80 eyes) clinically normal immature and mature donkeys of both sexes were included. Transpalpebral ocular ultrasonography was made using a 12-MHz linear transducer. Biometric ocular measurements were made including the anterior chamber depth, central lens thickness, vitreous chamber depth, axial globe length, longitudinal globe length, lens pole diameter and posterior wall thickness. Color Doppler velocimetric measurements including peak systolic velocity and end-diastolic velocity were made. Blood flow indices represented by resistive and pulsatility indices were calculated. Results revealed that laterality and gender did not represent variability factors in ocular biometry (P >.05), while the animal's maturity had an influence on axial globe length (P <.001), longitudinal globe length (P = 0.000) and lens pole diameter (P = .000). Laterality had no effect on velocimetric parameters and indices (P >.05) while gender had significant effect on resistive index (P = .024), pulstality index (P = .000) and volume flow per area (P = .008). The state of maturity had significant effects on peak systolic velocity (P = .027) and blood volume flow per distance (P = .012), and area (P = .048). Ocular biometry and color Doppler ultrasonography provided a clinically useful tool to evaluate the donkey's eye that will be helpful in diagnosing donkeys with ocular diseases.

Precocious synapses in 13.5-week fetal holoprosencephalic cortex and cyclopean retina

BACKGROUND

Genetic programming of cerebral development involves tissue morphogenesis and also timing of developmental processes. Precocious synaptogenesis in the neocortical plate was previously demonstrated in 5 of 6 fetuses of 20-31 weeks gestation.

MATERIALS AND METHODS

Neuropathological examination was performed of a 13-week-5-day fetus with trisomy-13, a lobar holoprosencephaly, hydrocephalus, cyclopia and absence of ears. Immunocytochemical demonstration of the synaptic vesicle protein synaptophysin was performed in the brain and retina, along with other neuronal markers.

RESULTS

Synaptophysin reactivity in the cortical plate was patchy and precocious. Radial glial fibres, demonstrated by vimentin, were oriented parallel to the cortical plate rather than perpendicular, probably because of hydrocephalus. A corpus striatum was not identified, but the poorly formed thalamus exhibited synaptophysin reactivity around many neurones. The cyclopean eye had ocular features of maturational delay including persistent hyaloid artery; ganglion cells were reduced in number, but retinal synaptophysin reactivity was paradoxically precocious.

CONCLUSIONS

Holoprosencephaly exhibits abnormal patchy synapse distribution in the neocortex and retina; synaptogenesis was precocious, as we previously described in older fetuses. Too soon an onset of synapse formation may promote early epileptic circuitry, leading to severe infantile epilepsies postnatally. The visual system is the last of the special sensory systems to mature, yet in this case showed too early synapse formation. In HPE, cyclopia and in trisomy 13, total absence of external ears has not been reported; it results from faulty craniofacial induction by neural crest.

Central retinal artery originating from the temporal short posterior ciliary artery associated with intraorbital external-to-internal carotid arterial anastomoses

Although variations in the peripapillary division pattern of the central retinal artery (CRA) are common, variations in the origin of this artery are seldom reported in the literature. Herein, the authors report a variant of the CRA that originated from the temporal short posterior ciliary artery. Two intraorbital anastomoses were also noted between the internal and external carotid arterial systems: one through the lacrimal artery-middle meningeal artery to the ophthalmic artery and the other through supraorbital artery-recurrent meningeal artery to the ophthalmic artery. A brief review of CRA variations and potential clinical significances of the observed variant are discussed.