Blindness - global causes

👁️🌍 Blindness is a major global public health issue, affecting over 40 million people worldwide and significantly reducing quality of life, independence, and economic productivity.

📖 Introduction

• Most blindness is avoidable - either preventable (e.g., infections, nutritional deficiency) or treatable (e.g., cataract, refractive error).
• According to the World Health Organization (WHO), more than 75% of global blindness is due to conditions that could be treated or prevented.
• Leading causes vary by region: - 🌍 Low-income regions: infectious causes (trachoma, onchocerciasis) and nutritional deficiency (vitamin A). - 🌍 High-income regions: degenerative causes (age-related macular degeneration, diabetic retinopathy, glaucoma).
• 📈 Ageing populations and rising diabetes prevalence are increasing the global burden of blindness.
• 🔑 Early detection, accessible treatment (e.g., cataract surgery, ivermectin distribution), and public health interventions remain the cornerstone of reducing preventable blindness.

☁️ Cataract

• Features: Gradual, painless vision loss (worse at night 🌙), glare sensitivity, frequent spectacle changes.
• Investigations: Visual acuity + slit-lamp exam.
• Treatment: Surgery with intraocular lens (IOL) implantation ✅ (most effective in reducing global blindness).

👁️‍🗨️ Glaucoma (“silent thief of sight”)

• Features: Early asymptomatic → progressive peripheral vision loss, halos, eye pain (acute cases).
• Investigations: Tonometry (IOP), optic disc exam, visual fields.
• Treatment: Eye drops (e.g. prostaglandins), laser, trabeculectomy in advanced cases.

🩸 Diabetic Retinopathy

• Features: Microaneurysms, haemorrhages, exudates → proliferative neovascularisation → blindness.
• Investigations: Dilated fundoscopy, fluorescein angiography, OCT.
• Treatment: Glycaemic control, laser photocoagulation, anti-VEGF injections, vitrectomy if severe.

🧓 Age-Related Macular Degeneration (ARMD)

• Features: Central vision loss, distorted lines (metamorphopsia), difficulty recognising faces.
• Investigations: Ophthalmoscopy, OCT, fluorescein angiography.
• Treatment: - Dry ARMD: supplements (AREDS2) 🍎, vision aids. - Wet ARMD: anti-VEGF injections 💉, laser in selected cases.

😷 Trachoma

• Features: Recurrent conjunctivitis → eyelid scarring → trichiasis (inward lashes) → corneal opacity → blindness.
• Investigations: Clinical eye exam, cultures for Chlamydia trachomatis.
• Treatment: SAFE strategy 🚰: Surgery, Antibiotics (azithromycin), Facial cleanliness, Environmental improvements.

🥕 Vitamin A Deficiency

• Features: Xerophthalmia (dry eye), keratomalacia (corneal ulceration), night blindness 🌙.
• Investigations: Ocular exam, serum retinol levels.
• Treatment: Vitamin A supplementation, fortified foods, public health nutrition programmes.

🦟 Onchocerciasis (River Blindness)

• Features: Itchy skin, nodules, visual loss → corneal scarring, optic nerve damage.
• Investigations: Skin snips (microfilariae), slit-lamp exam, serology.
• Treatment: Mass ivermectin administration 💊, community-directed treatment, supportive ophthalmic care.

📚 References

• WHO – Causes of Blindness
• National Eye Institute – Eye Health Data
• Merck Manual – Causes of Blindness

Cases - Blindness (Global Causes)

• Case 1 - Cataract (reversible) 👁️: A 72-year-old woman from rural India presents with gradual, painless loss of vision, difficulty recognising faces, and glare in bright sunlight. Exam: bilateral lens opacities. Diagnosis: cataract-related blindness, the leading global cause of avoidable blindness. Managed with cataract extraction and intraocular lens implantation.
• Case 2 - Trachoma (infectious) 🦠: A 40-year-old man from sub-Saharan Africa has progressive visual loss. History: recurrent childhood eye infections. Exam: trichiasis (inward-turned lashes scratching cornea) and corneal opacity. Diagnosis: blinding trachoma due to repeated Chlamydia trachomatis infection. Managed with SAFE strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement).
• Case 3 - Glaucoma (irreversible) 🧬: A 65-year-old Afro-Caribbean man presents with progressive tunnel vision and now central vision loss. Exam: raised IOP, optic disc cupping, constricted visual fields. Diagnosis: primary open-angle glaucoma, a major cause of irreversible blindness worldwide. Managed with prostaglandin analogue drops (latanoprost), possible trabeculectomy if uncontrolled.

Teaching Point 🩺: The major global causes of blindness are: - Cataract (most common, reversible with surgery). - Glaucoma (chronic, irreversible optic neuropathy). - Age-related macular degeneration (developed world). - Trachoma (infectious, preventable with hygiene/antibiotics). - Diabetic retinopathy (increasing worldwide). Prevention and early treatment are critical, as up to 80% of global blindness is avoidable.