Figure 1. Corneal radial
Dr Bruce Munro
MB BS DO FRCOphth FRACS FRANZCO
Nidek RS-3000 Advance OCT and Kowa Non-Myd WX 3D fundus camera
Designs For Vision
My website introduces me as ‘Bruce Munro, still trying to help with general eye problems in Geelong after 40 years in solo practice.’ I ceased surgery a few years ago and invested in diagnostic equipment that has included a Nidek Spectral Domain RS-3000 Advance OCT.
The ability to see scanning laser ophthalmoscope imaging next to pixel-for-pixel correspondence on OCT has been a great source of delight to me. Last year, I upgraded to a Nidek RS-3000 Advance OCT for a wider scan of both macula and disc in the 12 mm x 9 mm format. The resolution of the cross scans is outstanding. The new Nidek Advance takes only a couple of minutes to register a new patient and this pause allows time for the patient and me to settle, and for the patient to tell me how I may help. Within another couple of minutes, I have viewed and recorded a large area 12 mm x 9 mm macula map 3-D scan of the macula of both eyes, which is wide enough to include the optic disc. This helps me plan how to proceed with the presenting problem.
I believe that I am less likely to make errors in diagnosis and treatment with the help of this new equipment so that I may be a safer diagnostic ophthalmologist. I also purchased a Kowa Non-Myd WX 3D stereo colour camera for optic discs and macula to complete my suite of equipment.
A 71-year-old patient was referred for opinion and management by an optometrist. The patient had suspicious optic discs, IOP was 23 mmHg in each eye. Central corneal thickness (CCT) was 543 µm as measured on the Nidek anterior segment module. (Figure 1)
There was a probable ‘Drance’ haemorrhage at temporal margin of right disc. No previous history of trauma or eye surgery, no significant refractive error and no family history of glaucoma. Humphrey 24-2 fields were full with reliable, low error parameters and the patient appeared to be in good general health.
The images obtained seemed to fit with a diagnosis of preperimetric glaucoma.
I made careful examination of the discs to exclude both distorted tilting discs and disc drusen. The discs did not appear to be unusual apart from cupping and were recorded on Kowa stereo 3-D camera. I formed the opinion that the thinning of retinal nerve fibre layer around the right optic disc was true thinning as there were no variants. (Figure 2)
Figure 2. Disc map
There is close agreement between the Disc Circle and Disc Map scans, which strengthens this finding. As the visual fields appeared normal, without focal deficit or generalised decrease in the mean decibel result on reliable Humphrey threshold 24-2 testing, I believed it could not be an optic neuropathy.
The large 9 mm x 9 mm ganglion cell complex analysis from the macular map scan also showed thinning, supporting the diagnosis of preperimetric glaucoma. This type of scan has been helpful in other cases of tilted or myopic discs, where disc circle and disc map scan may not be a success. (Figure 3)
Figure 3. Macula map with ganglion cell analysis
The follow-up examination by careful disc observation in glaucoma is paramount. (Figures 4A and 4B)
Figure 4A and 4B. Kowa stereo images
I am finding the Kowa stereo 3-D camera to be most helpful in comparing present with previous optic disc appearance. The standard 45-degree fundus photos can be acquired through 3.5 mm pupils, though I do use a drop of Mydriacyl to ensure that pupil is at least 4 mm in size in order to obtain a reliable stereo picture.
For more images from this case report, visit www.drbrucemunro.com.au/disc.