Retinopathy (Vascular) refers to non inflammatory damage to the blood vessels that supply the retina.

 

There are many different causes for retinopathy. This article will focus on the most common causes:

 

  •   Diabetes mellitis
  •   Hypertension
  •   Retinal vein occlusion
  •   Retinal artery occlusion
  •   Premature birth
  •   Haemoglobinopathies e.g. sickle cell trait

         

        Understanding Signs of Retinal Vascular Disease

         

        The signs of retinopathy arise as a result of two mechanisms:

        1. Leakage of substances from capillaries
        2. Capillary occlusion
        Adapted from James B, Chew C, Bron A. Lecture Notes on Ophthalmology. 10/e Blackwell Publishing.

        Diabetic Retinopathy

         

        Diabetic retinopathy is common condition. Diabetic eye disease accounts for about 12% of people who are registered blind or partially sighted every year.

         

        20 years after initial diagnosis of diabetes mellitus, almost all patients with Type I diabetes and 60% of patients with Type II diabetes will show signs of retinopathy on examination, although not all of these patients will be symptomatic. 30 years after diagnosis of diabetes, 30% of Type I diabetics and 3% of Type II diabetics will have proliferative diabetic retinopathy.

         

        Risk factors:

        •   Duration of diabetes
        •   Glycaemic control
        •   Renal disease
        •   Systemic hypertension
        •   Hyperlipidaemia
        •   Pregnancy
        •   Laser treatment
        •   Previous diabetic eye disease

         

        Symptoms:

        •   Often asymptomatic
        •   Blurred vision
        •   Distortion
        •   Floaters
        •   Decreased visual acuity

         

          Visual loss may occur gradually (due to the maculopathy) or suddenly (due to vitreous haemmorhage).

           

           

            Progression of diabetic retinopathy

             

            Diabetic retinopathy can be divided into 3 stages:

            1. non-proliferative (background) retinopathy
            2. pre-proliferative retinopathy
            3. proliferative retinopathy

             

              Maculopathy (macular oedema), describes the presence of non-proliferative changes in the macula. This is the leading cause of visual loss in patients with diabetic retinopathy. It may occur in the setting of non-proliferative or proliferative retinopathy.

               

                Changes indicated in bold may lead to vision loss

                Signs of diabetic retinopathy

                Images taken from Clark M, Kumar P. 2009 Kumar &Clark’s Clinical Medicine 7/e Saunders

                Complications of proliferative retinopathy

                 

                1. Rubeosis iridis - neovascularisation of the iris, may cause a rise in intraocular pressure, resulting in neovascular glaucoma.
                2. Vitreous haemorrhage - occurs due to formation of new blood vessels towards the vitreous. These blood vessels tend to be more permeable, and thus are prone to breakage.
                3. Traction retinal detachment - oedema may separate the retinal pigment epithelium from the retina, resulting in retinal detachment.

                 

                Treatment

                 

                •   Proliferative retinopathy is treated with laser photocoagulation therapy. This scatters the retina with 1000-2000 burns, with the aim of eliminating the ischaemic retina, and thus the release of vasoproliferative factors.

                 

                •   Maculopathy is also treated using laser therapy directed at the points of leakage. If effective, the retinal oedema and exudate will resorb.

                 

                •   Vitrectomy may be indicated for patients with vitreous haemmorhage.

                 

                Screening for diabetic retinopathy

                A National Screening programme for diabetic retinopathy has been set up by the Department of Health. It offers annual screening with digital photography of the fundus of patients over the age of 11 with diabetes. Patients with signs of maculopathy, preproliferative or proliferative changes should be referred to an ophthalmologist.

                 

                 

                      HYPERTENSIVE RETINOPATHY

                       

                      Hypertension is the second most important cause of retinopathy after diabetes; 11% of patients over the age of 43 years with hypertension, but without coexisting diabetes have some evidence of retinopathy. 

                       

                      Retinal vessels respond to both acute and chronic hypertension:

                       

                      •   Acute elevation in blood pressure causes a vasospastic reaction (true hypertensive response)

                       

                      •   Chronic hypertension results in an arteriosclerotic reponse.

                      RETINAL VEIN OCCLUSION

                       

                      Aetiology

                      One of the most important causative factors for retinal vein occlusion is arteriosclerosis.

                       

                       

                      Other important risk factors include:

                      1. Increased age
                      2. Hypertension
                      3. Hyperlipidaemia
                      4. Diabetes mellitis
                      5. ↑ intra-ocular pressure (IOP)
                      6. (Rarely) blood dyscrasias/vasculitis

                       

                      Categorisation

                      Retinal vein occlusion can be divided into central retinal vein occlusion (CRVO), and branch retinal vein occlusion (BRVO). In branch retinal vein occlusion, changes are confined to the part of retina drained by the occluded vessel.

                       

                      Symptoms:

                       

                      Sudden, painless loss of vision. This may be partial or complete. The condition is usually unilateral.

                       

                      Signs

                      •   Flame and dot & blot haemmorhages
                      •   Cotton wool spots
                      •   Swollen optic disk
                      •   Macular oedema

                       

                      The retina may become ischaemic as a result of the vein occlusion. This may result in:

                       

                      •   The growth of abnormal new vessels on the retina and optic disk, causing vitreous haemorrhage.
                      •   Abnormal growth of vessels on the iris, resulting in rubeotic glaucoma

                       

                        Treatment

                         

                        Treatment should target the complications and any underlying cause.

                         

                        Retinal vein occlusion can be managed by treating the following complications:

                         

                        •   Macular oedema - laser treatment may be indicated to reduce oedema. This may be successful in branch retinal vein occlusion.
                        •   Neovascularisation - laser photocoagulation may be used to place burns on ischaemic retina (similar to the treatment in proliferative diabetic retinopathy).
                        •   Neovascular glaucoma - Both surgical and laser treatments are available, although they usually have a poor outcome.

                         

                        Prognosis

                           

                          In central and often in branch retinal vein occlusion, there is usually profound visual loss, with a poor prognosis. However, younger patients may experience some visual improvement.

                           

                          RETINAL ARTERY OCCLUSION

                           

                          Pathophysiology

                           

                          Retinal artery occlusions are usually embolic in origin. They may be:

                          •   Fibrin-platelet emboli - from diseased carotid arteries
                          •   Cholesterol emboli - from diseased carotid arteries
                          •   Calcific emboli - from diseased heart valves

                           

                          Other risk factors include:

                          •   Atherosclerotic changes (most common cause)
                          •   Cardiac embolism e.g. vegetations (endocarditis)
                          •   Vasculitis
                          •   Migraines (in younger patients)
                          •   Thrombophilia

                           

                          Symptoms

                           

                          Sudden painless loss of vision

                           

                          Fibrin-platelet emboli usually results in a fleeting loss of vision as the emboli passes through the retinal circulation (termed amaurosis fugax). Cholesterol and calcific emboli may cause a more permanent vision loss.

                           

                          Signs  

                          Immediate:

                          •   Emboli within arterioles

                           

                            Within a few weeks:

                            •   'Cherry red spot' on macula (for first 6 weeks)
                            •   Attenuation of arterioles
                            •   Retinal oedema
                            •   Cotton wool spots

                             

                              After several weeks:

                              •   Optic disc pallor

                               

                                Treatment

                                Acute treatment (within 24h of onset) involves dilating the occluded artery to allow the embolus to pass more distally, thus limiting the damage.

                                This may be achieved by:

                                •   Lowering the IOP with IV acetazolamide
                                •   Ocular massage
                                •   Paracentesis (IOP is lowered by releasing aqueous from the anterior chamber)
                                •   Increasing inhaled carbon dioxide (which causes vasodilation) by using a rebreath bag

                                 

                                  RETINOPATHY OF PREMATURITY

                                   

                                  Premature infants with a low birth-weight who have been exposed to oxygen therapy are at risk of developing this form of retinopathy, to varying degrees of severity. It affects up to 60% of infants weighing less than 1.5kg.

                                   

                                  Normal retinal vascularisation is not complete until full term gestation. In some premature babies, normal growth of blood vessels cease. This may occure due to a response to inhaled oxygen therapy. Vacularisation may then continue again normally (spontaneous regression) or abnormal growth of blood vessels (neovascurisation) may occur. At more severe stages, it can even result in traction retinal detachment and blindness.

                                   

                                  Risk factors

                                  •   Gestation < 32 weeks
                                  •   Birthweight < 1.5kg
                                  •   Oxygen therapy
                                  •   Apnoea
                                  •   Sepsis
                                  •   Duration of ventilation
                                  •   Blood transfusion
                                  •   Intraventricular haemorrhage
                                  •   Retinal light exposure

                                   

                                   

                                  Signs

                                  Signs of the disease depend on the severity of the condition, but the following may be seen:

                                  •   New vessels
                                  •   Retinal haemorrhage
                                  •   Increased tortuosity and dilatation of retinal vessels
                                  •   Bleeding into vitreous
                                  •   Retinal detachment

                                   

                                  Treatment

                                  Only infants with the most severe stages of retinopathy of prematurity, are likely to progress to visual loss and will require treatment (i.e. when the benefits of treatment outweigh the potential risks). Cryotherapy or laser therapy can be used to ablate the avascular area to induce regression of abnormal blood vessels.

                                   

                                  Screening of at risk babies is very important. Follow up care is also often provided, as premature babies are at a greater risk of myopia, strabismus and intracranial haemorrhage (which may cause cortical blindness).

                                   

                                  SICKLE CELL RETINOPATHY

                                   

                                  Sickle cell retinopathy occurs as a result of impaction of deformed red blood cells in the retinal blood vessels, resulting in occlusion and ischaemia. Paradoxically, this phenomenon is most severe in heterozygous individuals (who have sickle haemoglobin S, combined with normal haemoglobin A), as opposed to homozygous SS individuals.

                                   

                                  Sickle cell retinopathy can affect the eye in two ways:

                                   

                                  1. Proliferative retinopathy:

                                  •   Sea fan neovascularisation
                                  •   Progressive contraction of fibrovascular tissue can cause tractional retinal detachment/formation of retinal tears.

                                   

                                  2. Non- proliferative retinopathy

                                  •   Black 'sunburst' scars
                                  •   'Salmon patch' retinal haemorrhages
                                  •   Venous tortuosity
                                  •   Retinal artery/vein occlusion

                                   

                                  Formation of new blood vessels may result in vitreous haemorrhage and traction retinal detachment.

                                   

                                  References

                                   

                                  Moorfields Eye Hospital 2007 Diabetic Retinopathy [Online] Available from: http://www.moorfields.nhs.uk/Eyehealth/Commoneyeconditions/Diabeticretinopathy. Accessed 30/01/11

                                  Kanski J. 2009 Clinical Ophthalmology A Synopsis 2/e Elsevier

                                  James B, Chew C, Bron A. 2007 Lecture Notes Ophthalmology 10/e Blackwell Publishing.

                                  Batterbury M, Bowling B. 2005 Ophthalmology An Illustrated Colour Text 2/e Elsevier

                                  Kanski J. 2007 Clinical Ophthalmology: A Systematic Approach 6/e Butterworth-Heinemann.

                                  Clark M, Kumar P. 2009 Kumar & Clark’s Clinical Medicine 7/e Saunders

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