Frequency of spontaneous pulsations of the central retinal vein

The central retinal vein is the only structure in the body which can be examined non‐invasively, runs through the cerebrospinal fluid space, and has a shape that depends on the relationship between its internal pressure and the pressure in the space surrounding it. Estimation of central retinal vein pressure is, therefore, helpful in the assessment of cerebrospinal fluid pressure—that is, the intracranial pressure.¹,²,³,⁴ Central retinal vein pressure may be assessed by determining the external pressure at which the central retinal vein starts to pulsate. This method of assessment is similar to Riva‐Rocci's method of indirect measurement of arterial blood presure. For the central retinal vein, the external pressure is the intraocular pressure. The purpose of the present study was to find out the proportion percentage of subjects in whom the central retinal vein shows spontaneous pulsations, indicating that the pressure in the vein is lower than the intraocular pressure. The assessment of spontaneous retinal venous pulsations may be very useful for the opthalmic assessment whether the intracranial pressure is normal, or if spontaneous vein pulsation cannot be detected, whether the intracranial pressure is likly to be elevated.¹,²,³,⁴

Case report

Our clinical observational case series included 199 patients (384 eyes; mean (standard deviation (SD)) age, 63.9 (12.3) years; range, 7–90 years) attending the hospital because of cataract (n = 66 ), age‐related macular degeneration (n = 37) or other diseases (n = 96) not affecting the optic nerve or primarily the inner retina. Intraocular pressure ranged between 10 and 21 mm Hg. The mean (SD) refractive error was –0.15 (3.04) D (range, –15.5 to +6.50 D). Using tropicamide and phenylephrine 5% eye drops, the pupil was dilated. The optic disc was examined using a slit lamp and a hand‐held 78‐D ophthalmoscopic lens for at least 30 s. Any small pulsatile synchronous movement of the central retinal vein or its major branches inside the optic disc was noted as spontaneous pulsations. The non‐contact examination was part of a routine ophthalmoscopic examination of the fundus of the patients. The medical ethics committee approved the study protocol, fulfilling the criteria of the Declaration of Helsinki.

Spontaneous central retinal vein pulsations were detected in 343 (89.3%; 95% confidence interval (CI), 7.6 to 13.8) eyes of 186 (93.5%; 95% CI, 3.1 to 10) patients. The presence of a spontaneous central retinal vein pulsation was statistically independent of age (p = 0.57; 95% CI, 0.98 to 1.04) and gender (p = 0.78; odds ratio (OR): 1.19; 95% CI, 0.39 to 3.68). Frequency of detected spontaneous central retinal vein pulsations was significantly associated with hyperopic refractive error (p = 0.017; 95% CI, 1.08 to 2.19).

Comment

Confirming the findings of previous studies,⁵,⁶ the results of the present study (relatively high frequency of ophthalmoscopically detected spontaneous pulsations of the central retinal vein), suggest that about 10% of otherwise normal people do not have ophthalmoscopically detectable spontaneous central retinal vein pulsations. Our results as well as the previous findings may be important for several reasons: in a patient with an increased intracranial pressure, the retrobulbar cerebrospinal fluid pressure rises, eventually equalling the intraocular pressure. When this occurs, there is no longer a fluctuating intravascular pressure gradient between the intraocular retinal veins and the retrolaminar retinal vein. The venous blood flow becomes constant, and spontaneous central retinal vein pulsations cease.⁴ Based on the results of previous studies and the present investigation a lack of a spontaneous central retinal vein pulsation in a patient with a presumed increase in intracranial pressure may suggest with a probability of 10% a normal finding and with a probability of about 90% an abnormal situation. To cite an example, by Levine searched for spontaneous retinal venous pulsations in 218 subjects in a previous investigation.⁶ Spontaneous venous pulsations were present in 87.6% of 146 unselected subjects 20–90 years of age, and were absent in 100% of 33 patients with raised intracranial pressure without papilloedema and in 10 patients with papilloedema. Lumbar puncture in nine patients with raised intracranial pressure established the upper level at which spontaneous pulsations disappear as 190 mm H₂O, and no pressure above 180 mm H₂O was found in 29 patients with venous pulsations present before lumbar puncture. Some normal subjects with no pulsations showed definite pulsations on subsequent examinations. Levine's findings show that presence of spontaneous venous pulsations is a reliable indicator of an intracranial pressure below 180–190 mm H₂O. They suggest, like the results of the present investigation, that pulsations may be absent in normal subjects and absence of pulsations is, therefore, not a reliable guide to raised intracranial pressure.

In conclusion, ophthalmoscopic assessment of spontaneous pulsation of the central retinal vein is useful for the estimation of increased intracranial pressure; in a similar manner, it may be useful for the diagnosis of glaucomatous optic neuropathy and retinal vein occlusions, in which increased central retinal vein pressure has been reported.⁷