OcuLearning › Retina
Pathologic/Degenerative Myopia
ROUTINE — Retina
Symptoms
- often asymptomatic until middle adulthood
- decreased central vision or metamorphopsia (if macular cnv or schisis develops)
- floaters or flashes: high risk for retinal breaks or detachment
- severe near-sightedness requiring high-minus corrective lenses
Clinical Findings
Diagnostic thresholds
- refractive error: worse than −6.00 d
- axial length: ≥26.5 mm (mechanical stretching of all ocular coats)
Posterior pole & macula
- posterior staphyloma: pathologic outpouching of the posterior globe wall
- lacquer cracks: yellow, linear subretinal streaks (mechanical bruch ruptures)
- fuchs spots: hyperpigmented scars from prior hemorrhage or regressed cnv
- chorioretinal atrophy: patchy or diffuse thinning of the retina/choroid
Disc & periphery
- tilted disc: oblique insertion often with a large white myopic crescent
- peripheral thinning: lattice degeneration and high risk for retinal tears
Etiology
Pathophysiology
- progressive axial elongation leads to mechanical stretching and thinning of the ocular tissues
- bruch membrane breaks (lacquer cracks) allow for choroidal neovascularization (cnv)
Statistics
- strong genetic component; progression often continues into early adulthood
- fellow-eye risk: >30% lifetime risk of cnv once the first eye is affected
Red Flags
- myopic cnv: sudden central distortion/blur; requires urgent anti-vegf
- new lacquer cracks: heralds a high risk for immediate subretinal hemorrhage
- macular schisis or hole: progressive vision loss needing surgical evaluation
- sudden floaters/curtain: suggests rhegmatogenous retinal detachment
Investigations
Biometry & refraction
- axial length measurement (a-scan or iol master) to track elongation
- cycloplegic refraction for accurate power determination
Ocular exam
- dilated 360° peripheral exam with scleral depression (screen for tears)
- tonometry: note that standard applanation may underestimate iop in thin scleras
Imaging
- oct: mandatory for detecting foveoschisis, macular holes, and cnv
- oct-a: useful for identifying cnv within areas of chorioretinal atrophy
Treatment
Macular complications
- intravitreal anti-vegf: first-line for active myopic cnv; excellent response rate
- vitrectomy: for myopic traction maculopathy or macular holes
Peripheral disease
- laser photocoagulation or cryotherapy for high-risk retinal breaks/tears
Glaucoma management
- maintain a low threshold for treatment, as myopic discs are hard to evaluate for cupping
Clinical Pearl
high myopes need a 360° peripheral exam every visit — lattice, breaks, myopic cnv, and posterior staphyloma all hide in a seemingly quiet fundus.
Differential Diagnosis
- ## Age-related macular degeneration (AMD)
- • distinguished by presence of drusen and older age of onset
- ## Ocular histoplasmosis (POHS)
- • "punched-out" scars and peripapillary atrophy without high axial length
- ## Gyrate atrophy
- • scalloped areas of peripheral atrophy; associated with high ornithine levels