Poster
# 3
Poster |
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6th Internet World Congress for Biomedical Sciences |
Kazuo Emi(1)
(1)Emi Eye Clinic - Yokkaichi. Japan
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[Ophthalmology] |
It is well known fact that an increased intraocular pressure (IOP) may cause a glaucomatous optic neuropathy. But the eye can tolerate a mild increase in IOP for a long time without any obvious defect in the optic nerve or visual field. Whereas many patients develop a glaucomatous optic nerve damage and a visual field defect. This evidence indicates that there are any other facters which cause similar optic nerve damage. The normal IOP can damage the optic nerve which is considerably vulnerable to the hydrostatic pressure. An acute ischemia in the optic nerve causes anterior ischemic optic neuropathy. It is often said that the chronic ischemia in the optic nerve may cause the normal-tension glaucoma. (NTG) It is very important to assess the difference of the ocular blood circulation between normal-tension glaucoma patients and normal subjects.
Fourteen NTG patients and seventeen normal controls were compared. The mean age of the NTG patients was 72 years old. The mean age of the normal controls was 70 years old. After precise explanations of the procedure were given, consent was granted by all of the subjects.
The LOGIQ500 color Doppler unit (GE Medical System) with a 6.5MHz linear phase transducer was used to examine all of the subjects. Color-encoded blood flow of the central retinal artery (CRA) can be seen in the B-scan image of the optic nerve. The short posterior ciliary artery (PCA) is depicted just adjacent to the optic nerve within the retrobulbar space. We performed color Doppler imaging and pulse Doppler method to detect the blood flow of the CRA and PCA. The intraocular pressure, systemic blood pressure and pulse rate of all the subjects were measured before the procedure.
Many glaucoma studies have confirmed that high intraocular pressure is the most important risk facter for the disease. However, many patients seem to develop the disease with normal and occasionally low pressures. It should be considered that there must be other risk factors for the glaucoma. The normal IOP can damage the optic nerve which has considerably vulnerable to the hydrostatic pressure. An acute ischemia in the optic nerve causes anterior ischemic optic neuropathy. It is often said that the chronic ischemia in the optic nerve may cause NTG. Some NTG patients have Raynaud´s phenomenon, migrane or coldness of the hands or feet1,2. But most NTG patients have no systemic blood circulation disturbance. I think the insufficient ocular blood supply is an important risk factor among the other causative factors 3. The peripheral vascular resistence of the NTG patients is grater than that of normal controls in this experiment. At the end-diastolic phase of the heart, the low systemic blood pressure and high ocular peripheral vascular resistance might cause the insufficient ocular blood supply in NTG patients to certain extent. Such circulatory disturbance is apparently harmful for NTG patients with regard to the blood supply to the optic nerve. This study shows that its quite important to maintain the ocular blood circulation especially such NTG patients.
I believe the usage of betaxolol is the first choice for such type of the NTG patient because betaxolol is a beta-1 blocker which doesn´t have the vasoconstrictive effect and prohibit the calcium influx into the vessel´s endothelium resulting dilating the ocular peripheral vasculatures 4,5,6. The second choice, I think, is the usage of the unoprostone eye drops which improve the ocular blood circulation and no vasoconstrictive effect 7,8,9,10,.
High pulsatility indexes and low systemic blood pressure at the end-diastolic phase of the NTG population suggest that the ocular blood circulation of the NTG patients is insufficient when compared with the normal subjects. It is very important for NTG patients to maintain the ocular blood circulation to protect the optic nerve.
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[Ophthalmology] |
