Pathological Myopia

High myopia with structural changes of the posterior segment from progressive axial elongation of the globe, typically axial length above 26 mm and a spherical equivalent worse than -6.00 dioptres, with degenerative fundus complications that can cause irreversible visual loss. It is a leading cause of blindness in East Asia and is rising worldwide.

• Prevalence of high myopia in young adults: 5 to 20 percent in urban East Asia, 2 to 5 percent elsewhere.
• Risk factors: early onset of myopia, parental myopia, prolonged near work, little outdoor time, female sex, and genetic and syndromic causes (Stickler, Marfan, Ehlers-Danlos, retinopathy of prematurity, congenital stationary night blindness).
• Complications:
  • Posterior staphyloma, lacquer cracks, chorioretinal atrophy (myopic maculopathy, graded from tessellated fundus to patchy and macular atrophy).
  • Myopic choroidal neovascularisation (about 5 to 10 percent), with a Fuchs spot (pigmented scar).
  • Myopic traction maculopathy (foveoschisis, macular detachment, lamellar and full-thickness macular hole).
  • Retinal tears and rhegmatogenous detachment (lifetime risk about 5 percent above -6 dioptres), lattice degeneration, and giant tear.
  • Glaucoma (2 to 3 times risk), early cataract, and tilted optic disc with peripapillary atrophy and myopic optic neuropathy.

• Blurred distance vision, reduced best-corrected acuity unresponsive to glasses, floaters (vitreous liquefaction), photopsia, night vision difficulties, and metamorphopsia and central scotoma when the macula is involved.
• Fundus: large tilted disc with a temporal crescent, tessellated fundus, posterior staphyloma, lacquer cracks (linear breaks in Bruch membrane), diffuse and patchy atrophy, Fuchs spot, haemorrhage over lacquer cracks, and macular hole or schisis.
• Visual field defects from staphyloma and glaucoma.

• Cycloplegic refraction, axial length by optical biometry, keratometry, intraocular pressure, dilated fundus examination with scleral depression.
• Optical coherence tomography (foveoschisis, macular hole, subretinal fluid, choroidal thinning, neovascular membrane); wide-field fundus and autofluorescence imaging; optical coherence tomography angiography.
• Fluorescein or indocyanine green angiography for choroidal neovascularisation.
• Visual field testing and optic nerve imaging to detect glaucoma; B-scan ultrasound or magnetic resonance imaging to show staphyloma and globe shape.
• Genetic and systemic evaluation in syndromic cases.

• Correct refractive error with spectacles, contact lenses, or surgery (phakic implantable lenses in selected patients; laser refractive surgery has no effect on pathology).
• Myopic choroidal neovascularisation: intravitreal anti-VEGF (ranibizumab 0.5 mg or aflibercept 2 mg, one injection with retreatment as needed according to optical coherence tomography; bevacizumab 1.25 mg commonly used), usually requiring fewer injections (average 2 to 4 over 2 years) than other neovascular macular conditions.
• Myopic foveoschisis or macular hole: observation if vision is good and stable; pars plana vitrectomy with internal limiting membrane peeling (with foveal-sparing techniques) and gas tamponade for progressive schisis, detachment, or hole; macular buckling (posterior scleral buckle) for recurrent or refractory cases.
• Retinal tears and lattice degeneration with symptoms or tears: laser retinopexy or cryopexy; retinal detachment: scleral buckle or vitrectomy with gas or silicone oil; give patients urgent-symptom instructions (flashes, floaters, curtain).
• Glaucoma screening annually; cataract surgery with care for long globes (deep anterior chamber, lens-iris diaphragm retropulsion syndrome, zonular weakness).
• Myopia control in children: atropine 0.01 to 0.05 percent nightly, orthokeratology, multifocal or defocus soft contact lenses, defocus spectacle lenses, at least 2 hours of outdoor time daily, and limited near work, to reduce progression and the risk of later pathological myopia.
• Follow-up every 6 to 12 months, Amsler grid self-testing, advice to avoid contact sports and trauma, and low-vision rehabilitation for macular atrophy.