Gradual change in or loss of vision

Gradual change in or loss of vision is a common presentation, especially in older adults. Unlike sudden visual loss, it usually reflects progressive structural or metabolic damage. Early recognition is essential to preserve sight and address reversible causes.

🔬 Physiology of Vision

• The retina contains rods and cones that convert light into neural signals.
• The optic nerve transmits impulses to the lateral geniculate nucleus and occipital cortex.
• The macula provides high-acuity central vision and is vulnerable in degenerative disease.
• The lens and cornea refract light; opacification causes blurring.
• The vascular supply (retinal and choroidal arteries) is crucial — chronic ischaemia leads to atrophy.

⚠️ Causes of Gradual Visual Loss

• 📏 Refractive / Media: Myopia, hypermetropia, presbyopia, cataract, corneal dystrophies.
• 🧠 Retinal & Macular: Age-related macular degeneration (AMD), diabetic retinopathy, retinal dystrophies.
• 🩸 Optic Nerve: Chronic glaucoma (open-angle), compressive optic neuropathy, optic atrophy.
• ⚡ Systemic / Neurological: Multiple sclerosis (progressive optic neuritis), stroke-related occipital damage.

📋 History

• Onset: gradual vs stepwise decline.
• Laterality: unilateral vs bilateral.
• Associated symptoms: glare, halos (cataract), distortion (AMD), floaters (diabetic eye disease).
• Medical history: diabetes, hypertension, autoimmune disease.
• Medication history: steroids (risk of cataracts/glaucoma).
• Family history: glaucoma, inherited dystrophies.

🧑‍⚕️ Examination

• Visual acuity testing (Snellen/LogMAR).
• Pupil responses (afferent pupillary defect in optic nerve disease).
• Ophthalmoscopy: cataract (lens opacity), diabetic retinopathy (microaneurysms, haemorrhages), AMD (drusen, atrophy).
• Intraocular pressure measurement (tonometry for glaucoma).
• Visual fields (perimetry).

🔎 Investigations

• Optical Coherence Tomography (OCT) – retinal layers & macula.
• Fundus photography & fluorescein angiography (vascular disease, AMD).
• Visual field testing (glaucoma, optic nerve lesions).
• Ultrasound if opaque media prevent fundus view.
• Blood tests: glucose, HbA1c, ESR/CRP (temporal arteritis suspicion).
• Neuroimaging (MRI/CT) if optic nerve or brain pathology suspected.

💊 Management

• Refractive errors → spectacles/contact lenses.
• Cataract → surgical extraction + intraocular lens implantation.
• Glaucoma → topical IOP-lowering drops, laser trabeculoplasty, or surgery.
• AMD → smoking cessation, dietary modification, anti-VEGF intravitreal injections (for wet AMD).
• Diabetic retinopathy → tight glycaemic & BP control, laser photocoagulation, anti-VEGF therapy.
• Supportive → low-vision aids, referral to ophthalmology & vision support services.

💡 Teaching point: Always differentiate between reversible causes (e.g., cataract, refractive error) and irreversible causes (e.g., advanced glaucoma, macular degeneration). Early detection is key to preserving sight.

👁️ Case 1 — Age-Related Macular Degeneration (AMD)

A 78-year-old woman notices progressive difficulty reading and recognising faces over several months, though peripheral vision is preserved. Fundoscopy shows drusen and pigmentary changes at the macula. 💡 AMD is the leading cause of central vision loss in older adults. The dry form progresses slowly with retinal atrophy, while the wet form involves neovascularisation and faster decline. Management includes smoking cessation, dietary modification, and intravitreal anti-VEGF therapy for wet AMD.

👁️ Case 2 — Chronic Open-Angle Glaucoma

A 65-year-old man presents with slowly worsening peripheral vision, described as "tunnel vision," discovered incidentally on an optician’s visual field test. Examination shows cupped optic discs with raised intraocular pressure. 💡 Chronic open-angle glaucoma causes optic nerve damage due to impaired aqueous humour drainage. It is often asymptomatic until advanced, highlighting the importance of screening. First-line management is usually topical prostaglandin analogues to reduce intraocular pressure.

👁️ Case 3 — Diabetic Retinopathy

A 58-year-old man with poorly controlled type 2 diabetes complains of gradual, painless blurring of vision over several years. Fundoscopy reveals microaneurysms, dot-blot haemorrhages, and cotton wool spots. 💡 Diabetic retinopathy is caused by chronic hyperglycaemia leading to microvascular damage in the retina. It progresses from background to proliferative changes, and maculopathy may cause central vision loss. Management focuses on tight glycaemic, blood pressure, and lipid control, with laser or intravitreal therapy for advanced disease.