Red Reflex of the Eye - Part I PDF

Part 1: The red reflex in vitreous haemorrhage and retinal detachment Few clinical techniques are as simple as observing the red reflex of the eye and examination of the reflex is one of the fastest and most accurate ways of assessing a wide range of ocular pathologies. Included in this document...

Part 1: The red reflex in vitreous haemorrhage and retinal detachment Few clinical techniques are as simple as observing the red reflex of the eye and examination of the reflex is one of the fastest and most accurate ways of assessing a wide range of ocular pathologies. Included in this document Understanding the red reflex Examining the red reflex Findings in vitreous haemorrhage and retinal detachment Illustrations See also: Abnormalities of the red reflex in trauma and inflammation Understanding the red reflex The red reflex occurs because some of the light entering the eye is reflected from the retina and exits the pupil. A normal red reflex depends on two things, a healthy smooth retina and clear media (cornea, lens and vitreous). If there is an abnormality present in any of these structures, the reflex will usually become dulled and/or uneven. For example, a retinal detachment gives rise to an area of darkness or greyness in the red reflex because less light is reflected from the loose and wrinkled retina. Diffuse vitreous hemorrhage will cause a generalised dulling of the reflex because less light enters and exits the eye. Sharply demarcated opacities such as a corneal foreign body or a cortical lens opacity will appear as a localised black spot or line in the reflex. In almost all cases pathology causes a darkening, the exception being the leucocorias where retinal tumors or inflammations increase the amount of reflected light. Examining the red reflex The patient Dilation of the pupils is extremely helpful, particularly in elderly patients who have small pupils. Tropicamide 1.0% is the best mydriatic agent. Most patients will be adequately dilated in ten minutes. Tell the patients that the drops will sting or instil a single drop of local anaesthetic a few seconds before the dilating agent. Warn the patient that their vision will be blurred for approximately four hours and that there is a very small risk of developing acute angle closure. Instruct them to seek medical help if they develop pain, headache and nausea. The lighting Examine the patient in a darkened room. If the patient cannot be dilated, keep your ophthalmoscope turned down as much as possible to avoid constricting the pupils. The technique Place yourself before the patient. You can use your dominant eye to examine both eyes of the patient. Begin at arms length and move in to about 40 cms. Adjust your ophthalmoscope until the reflex is as sharp as possible. Compare the brightness of each red reflex and look for localised variations in each reflex. View the patient’s eye from various angles and get them to move their eyes back and forth. Findings in vitreous haemorrhage and retinal detachment Vitreous haemorrhage Blood in the vitreous may cause either a diffuse or a focal loss of the red reflex (Figs 1 & 2). The appearance in any one patient depends on how much blood there is and the extent to which it has diffused throughout the vitreous cavity. The reflex often changes as the examiner views the patient from different angles because the blood is commonly asymmetrically located in the vitreous. Moreover, the blood usually moves within the mobile vitreous and so the reflex may ‘swirl’ or change in appearance, particularly if the patient is asked to move their eye rapidly away from, and then back to, the examiner. The patient in Fig. 1 has a diffuse haemorrhage typical of that seen some time after a bleed or in elderly patients who have very ‘watery’ vitreous. The reflex is usually darker inferiorally. Figs 2a & 2b are two photographs of the same patient taken several seconds apart. Between the two pictures the focal collection of blood has moved with the mobile vitreous and appears to ‘drift’ across the red reflex.  Retinal detachment The patient in Fig. 3 has a superior retinal detachment. The change between the normal reflex and the dark area due to the detachment is sharply demarcated. The appearance and the level of demarcation will change according to the angle of viewing and the extent of the detachment. In this patient, the red reflex was totally normal when viewed with the eye in downgaze and totally black on upgaze. Illustrations Fig. 1. Diffuse vitreous haemorrhage. Fig. 2a & 2b. Focal vitreous haemorrhage. Fig. 3. Superior retinal detachment. © GP Eyes - Dr Malcolm McKellar 2011