Prevalence of Cilioretinal Arteries: A systematic review and a prospective cross-sectional observational study

PURPOSE

To review studies focusing on cilioretinal arteries (CLRA) in order to assess the overall prevalence and establish the prevalence of CLRA in a Hungarian Caucasian population. METHODS #1: Systematic literature review of published studies with at least 100 participants. METHODS #2: Non-mydriatic digital colour photographs were taken of 1000 consecutively enrolled healthy Caucasian young adult volunteers. Images were graded by two trained independent observers. Number and location of identified cilioretinal arteries were recorded and statistically analysed. RESULTS #1: Prevalence of CLRA ranges from 6.9% to 49.5%. Detection with fluorescein angiography yields the highest values followed by fundus photography and ophthalmoscopy. Unilateral presence of CLRA is between 70.30% and 93.65%, and temporal location is between 80.77% and 100%. RESULTS #2: We found at least one CLRA in 36.5% of the participants and in 22.75% of all the examined eyes. Cilioretinal arteries (CLRA) were unilateral in 75.34% and bilateral in 24.66%. Of all the identified CLRA, 96.16% were originating from the temporal rim of the optic disc. We identified at least one temporal CLRA supplying the macula in 28% of the participants and 16.95% of the examined eyes.

CONCLUSION

Prevalence of CLRA varies depending on identification method. Unilateral presence is unequivocally more frequent similarly to temporal location. From a risk of bias standpoint, high-quality studies are rare. Our data on the distribution pattern of CLRA are similar to that in the international literature. Based on our findings, we assume that slightly more than one-third of the Hungarian Caucasian population has a CLRA.

Analysis of urokinase immobilization on the polytetrafluoroethylene vascular prosthesis

The polytetrafluoroethylene (PTFE) vascular prosthesis is thrombogenic and therefore not an ideal artificial blood vessel. The immobilization of urokinase on the surface of this substance has the potential to render the PTFE thrombolytic. Urokinase was immobilized to PTFE using tridodecylmethyl-ammonium chloride as a surfactant. In this preliminary study, a success rate of 45 percent was observed for the immobilization of active urokinase to PTFE. A model is proposed wherein application of the graft to an in vivo system is discussed. The urokinase graft is expected to be most effective under conditions of reduced blood flow which otherwise might promote thrombogenesis. The systemic side effects of the immobilized urokinase are expected to be significantly less when compared with the side effects of urokinase infused for clot lysis. The model presented of the urokinase-bound graft suggests that development and further study of the graft will result in an improved PTFE vascular prosthesis.

Clinical study of urokinase-bound fibrocollagenous tubes

Dacron-reinforced fibrocollagenous tubes (FCT) were synthesized from canine mongrels using the mandril-rod technique in order to develop a small diameter (i.e., 4 mm i.d.) vascular graft. They were rendered fibrinolytic by immobilizing urokinase on to the inner surface of the tubes. Urokinase-bound fibrocollagenous tubes (UK-FCT), control FCTs (i.e., no bound enzyme), Perloff grafts (Dr. Perloff, Department of Surgery, University Medical Center, Sidney Australia, has developed a mandril-derived collagenous tube from goats. Samples were implanted for comparative purposes.) and autogeneous saphenous veins, were interposed in the carotid or femoral artery in chronic studies involving 21 canine mongrels. On the basis of Doppler auscultation and palpation, the UK-FCTs were statistically more patent than other candidate prostheses. Fibrin degradation product (FDP) increased in the dogs' systemic circulation with a postoperative peak of 5 days. The host's increase in fibrinolytic activity was shown to be local to the anastamosis. A carotid arterial extracorporeal shunt was designed to evaluate acute patency. Results indicated a rapid thrombosis but no platlet or fibrin adherence to the graft surface was observed, as evidenced by scanning electron microscopy.

Lysis time and FDP immunoprecipitation by soluble and immobilized urokinase

Urokinase (UK) was immobilized to the lumen of dacron-reinforced fibrocollagenous tubes (UK-FCT) using a glutaraldehyde entrapment process, in an effort to develop a fibrinolytic small diameter (i.e., 4 mm i.d.) vascular graft. Soluble and immobilized urokinase were evaluated for their ability to lyse synthetic clots made from purified physiologic substrates, alpha 2 plasmin inhibitor (alpha 2PI) mediated whole canine blood (WCB) and alpha 2PI-depleted WCB by measuring lysis time and fibrin degradation product (FDP) formation. Lysis times were orders of magnitude lower and FDP formation rates were orders of magnitude higher with synthetic clots compared with either alpha 2-mediated or alpha 2-depleted WCB clots as a substrate, using both soluble and immobilized UK. However, both soluble and immobilized UK catalyzed FDP formation at an enhanced rate for alpha 2PI-depleted WCB compared with the inhibitor-mediated substrate. These results suggest that both soluble and immobilized UK behave similarly when treated with either standard clots, alpha 2PI-mediated WCB and alpha 2PI-depleted WCB as substrates and the use of urokinase-bound fibrocollagenous tube may prove suitable as a fibrinolytic vascular prosthesis.