A Glaucoma Suspect With Red OCT Sectors and a High-Myopia Warning
A 55-year-old software manager is referred as a glaucoma suspect. IOP is 24 mmHg OD and 23 mmHg OS; central corneal thickness is 540 micrometres in each eye. Optic discs show vertical cup-to-disc ratios of 0.65 OD and 0.60 OS with some nasalization of vessels, but no haemorrhage or notch. Humphrey 24-2 SITA-Faster fields are reliable (fixation losses 1/10, false positives 2%, false negatives 4%) and show mean deviation -1.2 dB OD and -0.8 dB OS, with no cluster. OCT retinal nerve fibre layer imaging reports a red temporal sector OD and a red inferior sector OS, but signal strength is 6/10 in both eyes and the printout shows a high-myopia segmentation warning. He is -5.50 D bilaterally. He asks whether he has glaucoma and whether he needs drops today.
1. Evaluate the reliability and interpretation of the OCT and visual field results. What artifacts could explain the red sectors?
Read the worked answer
The visual fields are reliable by the stated indices and show no cluster or pattern deviation, so they do not establish glaucomatous field loss. The OCT is less trustworthy: signal strength 6/10 is below the usual acceptable threshold, and the high-myopia warning indicates possible segmentation error. High myopia produces a tilted disc, peripapillary atrophy, and a thin scleral canal, all of which can create false red sectors. The red temporal OD and inferior OS sectors may therefore be artifact rather than true retinal nerve fibre layer loss. I would repeat OCT with good signal strength, inspect the disc photographs, and use the 24-2 and 10-2 fields plus gonioscopy before calling this glaucoma. A single red sector on a poor-quality scan is not enough to diagnose glaucoma.
2. Estimate his risk of glaucoma and decide whether to start treatment today. Justify your answer with the specific findings.
Read the worked answer
He has ocular hypertension (IOP 24 and 23 mmHg) with a normal corneal thickness, suspicious but not definitive discs, and no reliable field or OCT evidence of damage. The risk of glaucoma is not zero, but it is not high enough to justify starting drops today on the basis of an unreliable OCT. The red sectors are more likely artifact. I would explain that he is a glaucoma suspect, not a confirmed glaucoma patient, and that the priority is to obtain clean baseline data. Treatment would be triggered by reproducible structural or functional progression, very high IOP, or a disc haemorrhage, not by a single poor-quality scan. This approach avoids unnecessary lifelong therapy and its side effects while still respecting the risk.
3. Design a monitoring plan for the next 12 months, including which tests you would repeat and what would trigger treatment.
Read the worked answer
Over 12 months I would obtain baseline optic disc photographs, repeat OCT after maximizing signal quality (dilating if needed), repeat 24-2 and 10-2 fields, gonioscopy, and a diurnal IOP curve. I would review him at 4-6 months and again at 12 months if stable. Treatment would be considered if there is reproducible retinal nerve fibre layer thinning, a new or enlarging field defect, a disc haemorrhage, or a sustained IOP rise. I would also discuss risk factors and adherence. This monitoring plan avoids treating a label while still detecting true conversion early. If the repeat OCT remains poor quality, I would rely more on disc photographs and fields rather than repeating an uninterpretable test indefinitely.