What does the RNFL (Retinal Nerve Fiber Layer) thinning in my OCT (Optical Coherence Tomography) report indicate for my vision, given my history of high myopia and normal intraocular pressures?

RNFL Thinning in High Myopia: Glaucoma Suspect vs. Physiologic Changes

Your RNFL thinning on OCT, combined with high myopia and normal intraocular pressures, places you in a glaucoma suspect category that requires comprehensive evaluation with visual field testing and IOP monitoring—you cannot dismiss these findings as purely myopic changes without ruling out early glaucomatous damage. 1

Understanding Your OCT Findings

The critical distinction: High myopia alone causes diffuse RNFL thinning, but focal thinning patterns—especially in the inferior and superior regions—suggest glaucomatous damage rather than purely myopic changes. 1, 2

What High Myopia Does to RNFL

• High myopia (≥-6.0 D) inherently causes thinner RNFL measurements, with studies showing mean RNFL thickness of 80.0 microns in high myopes versus 108.8 microns in controls 3
• After magnification adjustment, highly myopic eyes actually show thicker global and temporal RNFL but thinner nasal RNFL compared to emmetropic eyes 4
• The pattern matters more than absolute numbers: diffuse thinning across all quadrants suggests myopia, while focal inferior or superior thinning is highly suspicious for glaucoma 1, 2

Why Your Findings Are Concerning

You are classified as a primary open-angle glaucoma (POAG) suspect based on suspicious RNFL appearance, even with normal IOP. 5 The American Academy of Ophthalmology defines a glaucoma suspect as someone with "an appearance of the optic nerve head or RNFL suspicious for glaucomatous damage" regardless of IOP level 5

Key red flags in your situation:

• Myopia is an established risk factor for developing POAG 5
• Nearly 40% of POAG patients never show elevated IOP during office measurements 5
• Inferior and superior RNFL thinning are the most common early manifestations of glaucomatous damage 1, 6
• Structural optic nerve damage often precedes detectable visual field defects 6

Required Next Steps

Immediate Comprehensive Testing

You need baseline documentation that goes beyond just OCT 5, 1:

• Visual field testing with standard automated perimetry (SAP) to detect functional damage 1
• Multiple IOP measurements at different times of day to assess diurnal variation and rule out intermittent pressure spikes 1
• Gonioscopy to confirm open anterior chamber angles 5, 1
• Central corneal thickness (pachymetry) measurement, as thin corneas underestimate true IOP and increase glaucoma risk 5
• Stereoscopic optic nerve examination through dilated pupils to assess cup-to-disc ratio asymmetry and neuroretinal rim appearance 5, 1

Monitoring Protocol

Given your structural findings, you require monitoring every 3-6 months initially with repeat OCT, visual field testing, and IOP measurements 1

The rationale:

• Even treatment-naïve myopic patients with normal-tension glaucoma can show significant progression within 2 years 7
• 22.5% of myopic normal-tension glaucoma patients showed progressive RNFL thinning when left untreated 7
• Family history of glaucoma and higher mean IOP (even if "normal") are significant risk factors for progression 7

Treatment Decision Framework

When to Treat

Treatment is indicated if any of the following develop 5:

1. Evidence of progression on serial OCT or visual field testing indicating conversion to POAG 5, 1
2. Visual field defects consistent with glaucomatous damage (arcuate defects, nasal steps, paracentral depressions) 5, 6
3. High-risk profile based on additional factors beyond myopia 5, 1

Treatment Target

If treatment is initiated, aim for 20-30% IOP reduction from baseline 5, as clinical trials demonstrate this reduces risk of developing POAG and slows progression 5, 1, 6

Importantly:

• In the Ocular Hypertension Treatment Study, treatment reduced the risk of developing POAG from 9.5% to 4.5% 5
• However, 90-95% of untreated ocular hypertension patients did not progress to glaucoma over 5 years 5
• The decision balances your individual risk factors against the burden of lifelong treatment 5

Critical Pitfalls to Avoid

Don't Assume It's "Just Myopia"

The most dangerous error is dismissing RNFL thinning as purely myopic without comprehensive evaluation including IOP and visual fields 1. While high myopia does cause thinner RNFL, the pattern of focal inferior thinning with asymmetric cupping is highly suspicious for glaucoma 1, 2

Don't Rely on Single IOP Measurements

• IOP can fluctuate significantly throughout the day 1
• In myopic normal-tension glaucoma, even a mean IOP >14.2 mm Hg significantly increases the rate of RNFL thinning 7
• Patients with mean IOP <11 mm Hg showed no progression, but those above this threshold remained at risk 7

Don't Delay if High-Risk Features Present

Early treatment initiation is advised for high-risk patients with myopic glaucoma suspect status, even when the condition appears stable 7, particularly if you have:

• Family history of glaucoma 7
• Higher baseline IOP (even if "normal" range) 7
• Progressive RNFL thinning on serial OCT 7

Your Risk Stratification

Use the OHTS risk calculator (available at http://ohts.wustl.edu/risk/calculator.html) to quantify your 5-year risk of developing glaucoma based on age, cup-to-disc ratio, visual field pattern standard deviation, central corneal thickness, and IOP 5

Bottom line: Your OCT findings mandate complete glaucoma suspect workup—this is not optional surveillance but necessary diagnostic evaluation to determine if you have early POAG requiring treatment versus physiologic myopic changes requiring only monitoring 5, 1.