What does an Optical Coherence Tomography (OCT) report showing 91% symmetry, Cup-to-Disc Ratio (CDR) of 0.33 and 0.46 in the right and left eyes, respectively, Retinal Nerve Fiber Layer (RNFL) thickness of 88 and 87 micrometers, and myopic eyes with axial lengths of 25.9mm and 26.2mm suggest for a patient's risk of glaucoma or other retinal issues?

OCT Findings Suggest Primary Open-Angle Glaucoma Suspect with Asymmetric Structural Damage

This OCT report indicates you should be classified as a primary open-angle glaucoma (POAG) suspect requiring close monitoring, with the left eye showing more concerning structural changes than the right eye, particularly given the asymmetric cup-to-disc ratios (0.33 vs 0.46) and focal RNFL thinning in glaucoma-susceptible regions.

Key Structural Findings and Their Significance

Cup-to-Disc Ratio Asymmetry

• The CDR asymmetry between eyes (0.33 right vs 0.46 left) is a red flag for glaucomatous optic neuropathy, as optic disc neural rim asymmetry between the two eyes consistent with neural tissue loss is a characteristic finding in POAG 1
• While the right eye CDR of 0.33 falls within normal limits, the left eye CDR of 0.46 approaches the threshold for concern, particularly when combined with other findings 1
• The American Academy of Ophthalmology guidelines emphasize that diffuse or focal narrowing of the neuroretinal rim, especially at the superior and/or inferior poles, is a key indicator of glaucomatous damage 1

RNFL Thickness and Regional Thinning

• Your average RNFL thickness of 88μm (right) and 87μm (left) is borderline low, falling in a range where glaucomatous damage must be differentiated from other causes 1
• The inferior (I) and temporal (T) region thinning is particularly concerning because inferior and superior RNFL thinning are the most common early manifestations of glaucomatous damage 1
• The color-coded severity (yellow in right eye, red in left eye) indicates progressive worsening from right to left, with the left eye showing more advanced thinning 1
• Diffuse or localized thinning of the parapapillary RNFL, especially at the inferior or superior poles, is explicitly listed as evidence of optic nerve damage in POAG 1

Myopia as a Confounding Factor

• Your high myopia (axial lengths 25.9mm and 26.2mm) complicates interpretation because highly myopic individuals without glaucoma may have diffusely thin RNFL 1
• However, the focal nature of your thinning (specifically I and T regions) rather than diffuse thinning, combined with the asymmetric CDR, suggests glaucomatous rather than purely myopic changes 1
• The guidelines note that myopic eyes require careful interpretation of OCT results in the context of clinical examination 1

Intereye Asymmetry Analysis

Structural Asymmetry as a Diagnostic Indicator

• The 91% symmetry may seem reassuring, but the specific asymmetries in CDR and focal RNFL thinning patterns are more clinically relevant 2
• Research demonstrates that intereye RNFL asymmetry for global average greater than 6.0μm achieves 74% sensitivity and 90% specificity for differentiating glaucoma from normal eyes 2
• Your CDR asymmetry of 0.13 (0.46-0.33) represents significant structural asymmetry that warrants investigation 3
• Studies show that even in normal-tension glaucoma, greater RNFL thinning correlates with the eye having higher IOP, emphasizing the importance of asymmetry assessment 3

Required Next Steps for Diagnosis

Essential Baseline Testing

• You require comprehensive baseline evaluation including IOP measurement (preferably Goldmann applanation tonometry), gonioscopy to confirm open angles, and visual field testing with standard automated perimetry (SAP) 1
• IOP measurements should be obtained at multiple time points to assess diurnal variation, as larger inter-eye IOP asymmetry increases glaucoma risk 1
• Gonioscopy is mandatory to exclude angle closure or secondary causes of potential IOP elevation 1

Visual Field Assessment

• Standard automated perimetry is essential because structural changes on OCT may precede functional defects in some patients, while in others functional deficits occur first 1
• In the Ocular Hypertension Treatment Study, 55% of endpoints were reached by optic nerve damage alone without visual field loss, but both assessments remain integral to care 1
• Look for visual field patterns consistent with RNFL damage, such as nasal step, arcuate defects, or paracentral depressions 1

Documentation and Monitoring

• Stereoscopic disc photographs or additional OCT imaging should be obtained for baseline documentation to enable detection of progression over time 1
• The American Academy of Ophthalmology emphasizes that computer-based imaging and stereoscopic photography provide complementary information 1
• Serial OCT measurements are critical because progression analysis can detect structural changes that may precede visual field loss 1

Clinical Classification and Risk Stratification

POAG Suspect Criteria

• You meet criteria for POAG suspect based on structural abnormalities (asymmetric CDR, focal RNFL thinning in characteristic locations) even without confirmed IOP elevation or visual field defects 1
• The American Academy of Ophthalmology defines POAG suspects as having optic disc or RNFL structural abnormalities consistent with glaucoma, which you demonstrate 1

Risk Factors Present

• Structural asymmetry between eyes (CDR and RNFL patterns) 1
• Focal RNFL thinning in inferior region, the most common site of early glaucomatous damage 1
• High myopia, which may increase susceptibility to glaucomatous damage 1

Management Approach

Monitoring Frequency

• Given the structural findings, you require monitoring every 3-6 months initially with repeat OCT, visual field testing, and IOP measurements 1
• More frequent monitoring is warranted if any progression is detected or if additional risk factors are identified 1

Treatment Threshold

• Treatment decisions depend on your complete risk profile including IOP levels, visual field results, rate of progression, and life expectancy 1
• If IOP is elevated or visual field defects are present, treatment to lower IOP by 20-30% from baseline is recommended, as clinical trials demonstrate this reduces risk of developing POAG and slows progression 1
• The Ocular Hypertension Treatment Study proved that lowering elevated IOP reduces the risk of developing glaucomatous visual field and optic nerve damage 1

Critical Pitfalls to Avoid

Interpretation Errors

• Do not dismiss these findings as purely myopic changes without comprehensive evaluation including IOP and visual fields 1
• OCT results outside normative ranges do not always represent disease, but your pattern of focal inferior thinning with asymmetric cupping is highly suspicious for glaucoma 1
• Avoid relying solely on summary statistics (like the 91% symmetry); the specific patterns of CDR asymmetry and focal RNFL loss are more diagnostically significant 4, 2

Monitoring Gaps

• Do not assume stability without serial testing—structural changes can progress before functional loss becomes apparent 1
• Even with CMS-defined severe glaucoma criteria, substantial RNFL may remain measurable for monitoring, so continued OCT surveillance is valuable 5