Introduction: Patients with central retinal vein occlusion (CRVO) may experience reduced vision in the morning. This may be due to increased cystoid macular oedema (CMO), which can be measured on optical coherence tomography (OCT).
Methods: A prospective study was performed on ten patients. Retinal thickness measurements were made with the Topcon 3D OCT-1000: at 9 A.M., 11 A.M., 1 P.M., 3 P.M., 5 P.M. In addition, at 9 A.M. and 5 P.M. visual acuity was recorded using ETDRS LogMAR.
Results: There were seven males and three females with average age of 59.4 years (range 40-80 years). The average duration of symptoms was 5.4 months (range 3-9 months). In eyes with CRVO, median central macular thickness (CMT) significantly reduced from 571 microm at 9 A.M. to 475 microm at 5 P.M. (p < 0.05). Comparison of CMT at 9 A.M. to each of the subsequent time intervals found that there was a significant reduction in the central macula thickness late in the day (p < 0.05). There was no statistical difference in the visual acuity and change in macular thickness did not correlate with change in visual acuity in eyes affected by CRVO.
Discussion: Patients with CRVO demonstrate increase in CMO in morning compared with late morning and afternoon. Possible causes are diurnal variation in blood pressure, retinal metabolism and erect posture. Interventions designed to influence these factors could be used to try to reduce CMO severity.