Cataract and Glaucoma: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Cataracts and glaucoma are the world's leading causes of reversible and irreversible blindness, respectively. Cataracts — progressive opacification of the crystalline lens — affect over 94 million people globally and are the leading cause of correctable visual impairment; cataract surgery is the most commonly performed elective surgical procedure worldwide. Glaucoma — optic nerve damage typically from elevated intraocular pressure (IOP) — affects approximately 80 million people globally and is the leading cause of irreversible blindness. Both conditions are strongly age-related and increase substantially after age 60. They frequently coexist; phacoemulsification cataract surgery may transiently lower IOP, and combined cataract plus glaucoma surgery (phaco-MIGS, phaco-trabeculectomy) is increasingly performed. Early detection through regular eye examinations is the key to preventing blindness from both conditions.

Cataract causes: age-related lens fiber protein oxidation (nuclear sclerosis, most common), UV-B radiation exposure (posterior subcapsular cataract), diabetes mellitus (sorbitol pathway), prolonged systemic or topical corticosteroids, ocular trauma, metabolic disorders, and congenital causes (TORCH infections, galactosemia). Glaucoma: primary open-angle glaucoma (POAG) results from aqueous humor outflow resistance at the trabecular meshwork causing chronically elevated IOP; primary angle-closure glaucoma arises from anatomically narrow anterior chamber angle; secondary causes include uveitis, topical/systemic steroid use, trauma, and pigment dispersion syndrome. Shared risk factors for both conditions: age over 60, diabetes mellitus, hypertension, family history, and ocular hypertension. African ancestry is a strong independent risk factor for POAG.

Cataract: gradual, painless blurring of vision that worsens in bright light; increased glare and halos around lights particularly problematic at night while driving; monocular diplopia; reduced color contrast and saturation (yellowing of whites); frequent changes in spectacle or contact lens prescription; and difficulty reading. Glaucoma (POAG): typically entirely asymptomatic until substantial optic nerve damage has occurred, with insidious peripheral visual field loss progressing to tunnel vision and eventual central vision loss. Acute angle-closure glaucoma (AAC): sudden severe unilateral eye pain, nausea and vomiting, blurred vision with halos around lights, red eye, and fixed mid-dilated pupil — this is a true ophthalmic emergency requiring same-hour treatment. Normal-tension glaucoma may present with paracentral scotoma detected on formal visual field testing.

Cataract diagnosis: slit-lamp biomicroscopy assesses lens opacity type (nuclear, cortical, posterior subcapsular), grade (Lens Opacity Classification System III, LOCS III), and correlation with visual symptoms; best-corrected visual acuity determines timing of surgical intervention. Glaucoma diagnosis: Goldmann applanation tonometry measures IOP (normal range 10-21 mmHg, but damage occurs at normal IOP in 30% of POAG); optic disc assessment by stereoscopic fundoscopy for cup-to-disc ratio and neuroretinal rim thinning; OCT (optical coherence tomography) of the retinal nerve fiber layer quantifies progressive thinning with high sensitivity; Humphrey automated visual field testing maps scotomata; gonioscopy classifies the drainage angle as open or closed (critical for treatment selection); pachymetry measures central corneal thickness (thin corneas underestimate IOP).

Cataract: phacoemulsification with intraocular lens (IOL) implantation is the definitive curative surgical treatment performed as a day case under topical anesthesia in 15-30 minutes. Premium IOLs (toric for astigmatism, multifocal for presbyopia, extended-depth-of-focus) provide spectacle independence. Femtosecond laser-assisted cataract surgery (FLACS) enhances precision. Glaucoma — IOP-lowering therapy: first-line prostaglandin analogue drops (latanoprost 0.005%, bimatoprost 0.01%) once daily reduce IOP by 25-30%; additional agents include beta-blockers (timolol), alpha-2 agonists (brimonidine), carbonic anhydrase inhibitors (dorzolamide), and rho kinase inhibitors (netarsudil). Selective laser trabeculoplasty (SLT) as first-line or adjunct therapy (LIGHT trial: SLT equal to drops as first-line). Trabeculectomy (filtration surgery) for inadequate IOP control. Minimally invasive glaucoma surgery (MIGS: iStent, iStent inject W, OMNI, Hydrus) performed at time of cataract surgery for mild-moderate glaucoma.

Prognosis after cataract surgery is excellent: phacoemulsification with intraocular lens implantation achieves visual recovery in over 99% of appropriately selected patients, with best-corrected visual acuity of 6/12 or better in over 95% of eyes without coexisting retinal or macular pathology. Vision improvement is typically apparent within 24-48 hours. Posterior capsule opacification occurs in approximately 20% of patients within 5 years but is easily resolved with a 5-minute YAG laser capsulotomy. Glaucoma, by contrast, causes irreversible optic nerve damage; treatment halts or slows progression but cannot restore lost vision. The Early Manifest Glaucoma Trial (EMGT) demonstrated that without IOP lowering, significant visual field progression occurs in 62% of patients over 6 years versus 45% in treated patients — confirming that treatment meaningfully delays progression. Patients diagnosed early and treated consistently maintain functional vision throughout their lifetime in most cases. Advanced glaucoma or normal-tension glaucoma with progressive optic nerve damage despite adequate IOP control carries higher risk of eventual visual disability. Key prognostic factors for glaucoma include age at diagnosis (younger patients require decades of sustained disease control), baseline IOP, severity of optic disc cupping, central corneal thickness, and adherence to treatment — with non-adherence being the dominant cause of preventable visual loss. Long-term monitoring includes IOP measurement every 3-6 months, annual Humphrey visual field testing, and OCT retinal nerve fiber layer assessment every 6-12 months to detect progression before clinically significant functional loss occurs. All glaucoma patients require lifelong ophthalmological review.

Cataract prevention: UV-protective sunglasses to reduce UV-B exposure, optimal diabetes control (reduces diabetic lens changes), avoidance of unnecessary systemic and topical corticosteroids, smoking cessation, adequate dietary antioxidant intake (vitamin C and E), and minimizing blunt ocular trauma. Glaucoma prevention focuses on regular screening for IOP and optic nerve changes: eye examinations every 1-2 years after age 40, and annually after age 60 or with risk factors (family history, African ancestry, myopia, diabetes). For ocular hypertension (IOP >21 mmHg without glaucomatous changes): evidence from the OHTS trial supports IOP-lowering therapy (latanoprost) to reduce conversion to glaucoma by approximately 50%. Acute angle-closure prevention: prophylactic laser peripheral iridotomy in the fellow eye after a first attack prevents second-eye acute AAC, which occurs in up to 50% without treatment.

Acute angle-closure glaucoma is an ophthalmic emergency requiring same-hour treatment: seek emergency eye care immediately for sudden severe eye pain, nausea, blurred vision with halos, and red eye. Routine ophthalmological assessment is recommended for: adults over age 40, annually or every 2 years even without symptoms; individuals with diabetes, hypertension, or a family history of glaucoma — annually; anyone noticing gradual blurring of vision, increasing glare at night, or difficulty with contrast — book an urgent eye examination. Glaucoma is asymptomatic until advanced: regular IOP and optic nerve assessment is the only way to detect it before irreversible damage occurs. Patients on long-term oral or inhaled corticosteroids should have IOP monitoring to detect steroid-induced glaucoma.