![]() Drawing a diagram of this and annotating any areas of thinning can be very useful. ![]() To examine this, you need to view around the 360° of the NRR and try to identify any areas of localised thinning or notches. Actually what we are more interested in is the condition of the NRR, as this is the tissue containing all the healthy ganglion cell axons, and in short, the more of these the better. Traditionally the amount of cupping was described, and a cup to disc ratio measured. This is probably the key to examining the optic nerve head in most eyes. There is a really useful tool called the Disc Damage Likelihood Scale developed by Dr George Spaeth, which you can look up which equates disc size and NRR changes, which is really how we have to think about the optic nerve head. There may be a corrective factor owing to which lens you are using, but at very least this gives you an idea of whether the disc is of average size, is particularly small or large. This is measured by lining up a vertical beam of light from the slit lamp over the nerve head and reducing the height until it matches that of the disc and reading the height off the beam height graticule. It is only by doing this that we can consider any degree of optic nerve head cupping, or thinning of the NRR in proper context. I have put this parameter high up the list on purpose as it is really important to measure the height of the. This is just be by virtue of the tilted disc, rather than there being a progressive glaucoma. I see quite a lot of tilted discs, which by default have areas of the NRR that appear thinned, and may produce a visual field defect. ![]() It is always worth highlighting that bilateral swollen discs can represent an ocular emergency. There are however several variants of optic nerve head which sometimes make our conventional analysis pretty much impossible.Īn important skill is being able to recognise these variants and have a working knowledge as to how to manage them. If this is the case we can apply our usual criteria as described in the next paragraphs, to help decide whether or not this looks healthy. The first thing to have a look at is to decide whether this is a ‘conventional’ appearing disc with a normal insertion into the back of the eye, with a discernible neuro-retinal rim (NRR), and cup in the centre. Please note that this is always with a volk lens at the slit-lamp, with dilation when required, and only with direct ophthalmoscopy if the patient is unable to position at the slit-lamp. In order to examine a disc in detail I try to follow these steps. However with a lot of discs the analysis of it is not clear cut and we have to monitor the disc over the course of time for evidence of change.Įxamination of the optic nerve head for potential glaucoma or other pathology is one of the very fundamental skills that all optometrists require, and so hopefully this refresher will be useful. The skill of trying to decipher a normal optic nerve, from one which is perhaps just a variant of normal, from one which has glaucoma is something which you develop over time and seeing lots of different discs. I currently do a lot of hospital glaucoma clinics, as this is my main area of clinical interest. In this latest blog post I thought it might be useful to give a short overview of how to examine the optic nerve head.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |