ABSTRACT
The pathogeneses, clinical features, and management of central retinal artery occlusion (CRAO) are discussed. CRAO consists of the following four distinct clinical entities: non-arteritic CRAO (NA-CRAO), transient NA-CRAO, NA-CRAO with cilioretinal artery sparing, and arteritic CRAO. Clinical characteristics, visual outcome, and management very much depend upon the type of CRAO. Contrary to the prevalent belief, spontaneous improvement in both visual acuity and visual fields does occur, mainly during the first 7 days. The incidence of spontaneous visual acuity improvement during the first 7 days differs significantly (P < 0.001) among the four types of CRAO; among them, in eyes with initial visual acuity of counting finger or worse, visual acuity improved, remained stable, or deteriorated in NA-CRAO in 22%, 66%, and 12%, respectively; in NA-CRAO with cilioretinal artery sparing in 67%, 33%, and none, respectively; and in transient NA-CRAO in 82%, 18%, and none, respectively. Arteritic CRAO shows no change. Recent studies have shown that administration of local intra-arterial thrombolytic agent not only has no beneficial effect but also can be harmful. Investigations to find the cause and to prevent or reduce the risk of any further visual problems are discussed. Prevalent multiple misconceptions on CRAO are discussed.
ABSTRACT
Context: Retinal perfusion variability impacts ocular disease and physiology. Aim: To evaluate the response of central retinal artery (CRA) blood flow to temperature alterations in 20 healthy volunteers. Setting and Design: Non-interventional experimental human study. Materials and Methods: Baseline data recorded: Ocular surface temperature (OST) in °C (thermo-anemometer), CRA peak systolic velocity (PSV) and end diastolic velocity (EDV) in cm/s using Color Doppler. Ocular laterality and temperature alteration (warming by electric lamp/cooling by ice-gel pack) were randomly assigned. Primary outcomes recorded were: OST and intraocular pressure (IOP) immediately after warming or cooling and ten minutes later; CRA-PSV and EDV at three, six and nine minutes warming or cooling. Statistical Analysis: Repeated measures ANOVA. Results: (n = 20; μ ± SD): Pre-warming values were; OST: 34.5 ± 1.02°C, CRA-PSV: 9.3 ± 2.33 cm/s, CRA-EDV: 4.6 ± 1.27 cm/s. OST significantly increased by 1.96°C (95% CI: 1.54 to 2.37) after warming, but returned to baseline ten minutes later. Only at three minutes, the PSV significantly rose by 1.21 cm/s (95% CI: 0.51to1.91). Pre-cooling values were: OST: 34.5 ± 0.96°C, CRA-PSV: 9.7 ± 2.45 cm/s, CRA-EDV: 4.7 ± 1.12 cm/s. OST significantly decreased by 2.81°C (95% CI: −2.30 to −3.37) after cooling, and returned to baseline at ten minutes. There was a significant drop in CRA-PSV by 1.10cm/s (95% CI: −2.05 to −0.15) and CRA-EDV by 0.81 (95% CI: −1.47 to −0.14) at three minutes. At six minutes both PSV (95% CI: −1.38 to −0.03) and EDV (95% CI: −1.26 to −0.02) were significantly lower. All values at ten minutes were comparable to baseline. The IOP showed insignificant alteration on warming (95% CI of difference: −0.17 to 1.57mmHg), but was significantly lower after cooling (95% CI: −2.95 to −4.30mmHg). After ten minutes, IOP had returned to baseline. Conclusion: This study confirms that CRA flow significantly increases on warming and decreases on cooling, the latter despite a significant lowering of IOP.