Definition: it is the degenerative disease of the central part of retina known as macula, characterized by a loss of visual acuity, retinal pigment epithelium (RPE) and photoreceptors.
Classification of ARMD:
|No or few small drusen|
|Early||Multiple small drusen or RPE abnormality|
|Intermediate||Extensive inter drusen, large drusen|
Atrophy or neovascular maculopathy
Drusen: Is a tiny yellow or white accumulation of extracellular material in Bruch’s membrane of the eye. Drusen can also be defined as deposits of extracellular debris between basal lamina of RPE & inner collagenous layer of Bruch’s membrane. These lesions are hallmark of ARMD. They can be hard or soft. Soft drusen are larger & have no well-defined margins. Whereas hard drusen’s are smaller & well defined. Drusen is composed of lipids, carbohydrates, zinc & proteins.
Stages of ARMD: early stages are characterized by macula with yellowish sub retinal deposits and increased pigmentation.
- Dry ARMD also known as non exudative, non neovascular or atrophic ARMD. Is more common & has slow progression.
- Wet ARMD also called exudative & neovascular ARMD. It has rapid distortion & a sudden loss of central vision. Macular edema due to accumulation of fluid underneath retina can also be seen.
Etiology & risk factors: are multifactorial and involves genetics, environment, metabolics, family history, smoking, blood pressure etc. Macular deterioration destroys central vision but peripheral vision remains intact.
Diagnosis: ARMD is usually asymptomatic but acute vision loss may occur. As it has a slow progression, so routine dilated eye exams are recommended. 13% patients with ARMD present with Charles Bonnet syndrome, in which healthy patients have vision loss & visual hallucinations. Tests: Visual acuity tests, dilated fundoscopy, fundus autofluorescence are done.
Treatment: Thermal laser photocoagulation was choice of treatment, but was seen to be associated with high rate of recurrence.
Submacular surgery, external beam irradiation, I/V steroids for their anti angiogenic effect have more side effects & lesser use.
Better options include;
PDT… Photodynamic therapy which uses a combination of drugs & laser. Verteporfin forms free radicals, coagulating retinal damaging vessels. It is reconstituted with WFI to give 7.5ml containing 2mg/mL. Contraindication to verteporfin is porphyria.
VEGF inhibition: Vascular endothelial growth factor inhibitors for angiogenesis being used are Bevacizumab (Avastin), ranibizumab intravitreally.