The Zeiss OCT

I recommend optical coherence topography (OCT) as part of a routine sight test to all of my patients over the age of 40, and use it extensively when performing other consultations too.

When I first decided to invest in an OCT device, after extensive research I opted for the Zeiss Cirrus as it is the OCT of choice for my local hospital department. I was therefore minded that it would be helpful that if I was referring on the basis of OCT results, they were presented in a format familiar to the consultants.

I find the Zeiss Cirrus OCT an amazingly versatile instrument. I even used it when conducting research to generate images of cortical cataract and found that I could obtain images of the mid peripheral retina, which are immensely valuable when differentiating between a schisis and a detachment, or observing if a peripheral lesion was raised or atrophic.

"I regard my OCT as an invaluable asset to the practice, but also one which pays its way too, whilst improving patient retention. I wouldn't practice without one"

Its anterior segment capabilities generate dynamic images of the angle and how it changes with variations in illumination, as well as corneal images for pachymetry or to provide a view of corneal pathology.

The scanning laser image shows up diabetic retinopathy and vitreous floaters in perfect detail. And year-on-year sequential optic nerve measurements using the tool’s guided progression analysis are an incomparable method for detecting early pre-perimetric glaucomatous retinal nerve fiber layer (RNFL) loss and establishing a structure-function relationship in glaucoma.

Scans of the macula frequently reveal changes that are undetectable in a conventional examination. Overall, there are very few posterior segment pathologies that the OCT does not provide some additional insight into.

This OCT can also give images where all else fails – even through a cataract that looks opaque to visible light, OCT will often provide an image good enough to verify that the macula is flat and the retinal pigment epithelium/photoreceptor intact. This in turn enables me to refer a patient for cataract removal with confidence that their vision has the potential to improve, or conversely recommend that referral is not worthwhile.

Small pupils present no problem – think about that patient on pilocarpine whose macula and discs you haven’t seen properly for years. I warn though, the device doesn’t like scanning through corneal opacities.

However, I can confidently say that my OCT device has saved the sight of some of my patients, usually due to the detection of subtle macula oedema, which indicates the asymptomatic onset of wet age-related macular degeneration or diabetic maculopathy, that has been entirely undetectable with any other method.

Often a patient with unexplained, slightly reduced visual acuity will display a tiny foveal gap in the photoreceptor layer from some previous vitreo-macular traction. Whilst untreatable, it provides reassurance to the patient.

While benefits are aplenty, OCT is certainly not a replacement for any of the other instruments that I routinely use, and should always be used in conjunction with conventional examination. For example, colour changes in the absence of structural change will not show up, and it is impractical to attempt to image the far periphery. In addition, over-reliance on automatic disc and RNFL measurements will lead to false positives and negatives.

As an educational tool for patients though, this OCT is wonderful. Above the instrument itself I have a 32” monitor, on which I display the scans that I have just taken. This means that I can explain to patients exactly what I am looking at, and compare them with the previous year’s scans so they can see what has changed. Patients are invariably impressed.

I regard my OCT as an invaluable asset to the practice, but also one which pays its way too, whilst improving patient retention. I wouldn’t practice without one.