The jelly-like substance filling the space between the crystalline lens and the retina is called “vitreous humour”. The vitreous humour degenerates and liquefies when we get older, at which time we start to see floaters. Floaters can be moving opacities of various shapes and sizes (dots, circles, lines or spider webs). Physiological floaters usually occur when we are looking at a bright homogenous background such as a white wall or the blue sky. The floating opacities are few in number and remain unchanged over time. They represent normal physiological changes of the vitreous humour. As we age, the vitreous humour undergoes the processes of synchysis (liquefying) and syneresis (dehydrating and shrinking). These are normal agerelated degenerations.

Pathological floaters appear suddenly and may occur in great numbers. They may suggest bleeding within the vitreous humour, inflammation of the uvea or separation of the posterior vitreous humour from the retina. If the floaters are accompanied by flashes or visual field defects, it may indicate retinal tear or retinal detachment. When the vitreous humour contracts and detaches from the retina, it is called acute posterior vitreous detachment (acute PVD), at which time sudden onset of floaters and flashes occur. Floaters can be caused by vitreous opacities or haemorrhages, whereas flashes are caused by the vitreous humour pulling on the retina. An urgent dilated eye examination is essential to check for retinal tears, which should be repaired with laser as soon as possible, to prevent it from evolving into retinal detachment within a few hours.

懷疑是痣或色素變化，建議接受「全面眼科視光檢查」，由眼科視光師作出診斷及建議。

色弱問題暫時未有方法可處理，而本中心亦暫時沒有提供予色弱患者的協助工具。

如果閣下發現的黑影會跟隨眼睛轉動而移動的，有機會是飛蚊症的徵狀，建議閣下作全面眼睛檢查以排除視網膜疾病的可能性。一般而言，出現飛蚊是眼睛隨年齡增長而退化的正常徵狀，但若飛蚊在短時間內突然出現大量或增加，或見到閃光，則擔心有視網膜病變或脫落的徵狀，建議盡快找眼科視光師或眼科醫生作全面眼睛檢查及跟進。

恕未能單憑描述判斷閣下的眼睛的實際情況，其實有很多原因導致眼乾，例如睡眠時間不足、眼睛過度疲勞及眼睛淚水分泌不足等，而眼睛隨年紀退化亦是可能性之一。建議接受「全面眼科視光檢查」，由眼科視光師作出診斷及建議。

正常情況下驗度數不需要先作放瞳，但眼科視光師會因應情況決定是否需要放瞳再作檢查。透過散瞳劑能放鬆睫狀肌以更準確檢查屈光度數。可是，度數準確性可因不同原因而有所差異，故未能在此為閣下作判斷。建議閣下接受「全面眼科視光檢查」，當中包括放瞳眼底檢查，詳細檢查眼睛內外健康狀況後，包括有否白內障或青光眼，再由眼科視光師作出判斷及跟進。

大部份的散光是先天性，度數變化不大。另如眼皮過緊、經常摔眼有機會令散光加深。

如果只是偶爾進行此動作時（如動作很快地站立）才見到閣下提及的發光現象，有可能是血壓突然改變所致。如果情況變得頻密或明顯，有可能會是視網膜出現問題。如有懷疑，建議接受「全面眼科視光檢查」，由眼科視光師作出診斷及建議。

導致重影的原因可以與雙眼合作性、眼疾及度數有關，怒未能根據閣下的描述而作出判斷，建議作詳細眼睛檢查，以查明真正原因。

捽眼可能是一些壞習慣，亦可能是眼睛不適的警示，如眼乾、眼痕、眼睫毛倒生、雙眼協調問題等都有機會導致捽眼。建議閣下可帶兒子到政府眼科醫院，理工大學附屬的眼科視光診所作詳細檢查，前述的醫院及眼科診所針對幼兒視力問題的處理有一定經驗及配套，相信能夠解答閣下疑問。