Diabetic Retinopathy

How/why does anti-VEGF treat DMO in NPDR? Supposedly, there is no neovascularisation (or at least, no macroscopic neovascularisation)?

reference: Campochiaro 2016 in Ophthalmology

  • Hyperglycaemia causes non perfusion of tissue capillaries (Jampol 2020)

Passive

reference: Jampol LM 2020 in NEJM (Review)

retinopathy develops from 10 yrs after onset of diabetes

increased retinal vessel permeability

hard exudates are intraretinal

non perfusion of capillaries tissue hypoxia drives vegf release

vascular permeability intra and subretinal fluid

neovascularisation develops, and can cause - vitreous haemorrhage - tractional retinal detachment -

ultrawide field photography allows for imaging of more than 80% of the retinal surface in a single image

there are three layers of retinal vessels

fluorescein angiography remains important for detecting leakage

pan retinal photocoagulation has revolutionised treatment

2010 drcr network showed that ranibizumab with immediate or delayed laser to the macula (if necessary) was better than laser alone

initial anti vegf has replaced macular laser therapy as the initial standard treatment in diabetic macular oedema

ivi triamcinolone had initiallly fained traction in tx diabetes, but the drcr network showed that laser photocaogulation was superiior to triamcinolone for dmo

sustained release steroids were also shown to reduce macular thickness, but they cause cataract and increase iop/cause glaucoma

anti vegf are generally cleared from the eye within a month, yet the duration of treatment varies

the optimal treatment protocol for antivegf remains unclear

but the injection protocol used in the drcr retina network trial for ranibizumab gives some guide. in that study: - monthly for 6 months - this is a bit intricate, come back to this later

there is a drcr reitna network trial comparing aflibercept to ranibizumab and bevacizumab

in this comparison, there was little difference when vision was better than 6/12 when vision was 6/18 or worse, then aflibercept had better vision that bevacizumab at 2 years

the main complications of proliferative diabetic reinotpathy are vitreous haemorrhage, retinal detachment, and neovascular glaucoma

the clarity study showed that at 1 year, patients receiving aflibercept did better than prp

a drcr retinal trial showed that ranibizumab were non inferior than prp at 2 and 5 years

desipte this, vegf needs regular injection, and there is high loss to follow up in which case, prp may be more suitable for patients, particularly with poor injection compliance / poor access to injections

Open evidence, but look this up properly:

Patient Information

What is happening to my eyes?

  • High blood sugar damages your blood vessels

  • This causes occlusion

reference: Jampol LM 2020 in NEJM (Review)

non perfusion of capillaries tissue hypoxia drives vegf release

vascular permeability intra and subretinal fluid

Some references to look up:

  • Eye 2018. Laws of physics help explain capillary non perfusion in diabetic retinopathy

  • NEJM 2020. Evaluation and care of patients with diabetic retinopathy