Prescribing medicines

18 February 2015
Optometrists prescribing medicines
 
Some optometrists can prescribe medicines in the same way a medical doctor can. At our practice we have 3 optometrists who can do this.
 
So if your eye is red or sore you can come to one of our optometrists for treatment. We have the necessary equipment and after 5 years studying the eye we are in a great position to help you.
 
Having optometrists prescribe medicines enables New Zealand optometrists to provide a very high standard of care to their patients but it has been a long time coming. Optometrists in the USA have been prescribing medicines for over 30 years.
 
Twenty five percent of practising optometrists in New Zealand are able to prescribe prescription medicines. This percentage is increasing quite rapidly.
 
 
The technical bits…
 
Medicines prescribed by an optometrist prescriber attract the same government subsidies for the patient as if the medicine was prescribed by a medical practitioner.
 
The formulary for designated optometry prescribers includes all topical eye preparations excluding those for glaucoma.
 
The Bachelor of Optometry program at the University of Auckland became a 5 year degree in 2006 in order to accommodate the therapeutic component of the new degree. Graduates from that year onward are able to register immediately in the optometry prescriber scope of practice. Post graduates have needed to complete a 280 hour bridging course.
 
Regulations under the Medicines Act 1981to permit optometrists prescribing medicines came into effect late 2005.
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Optical Coherence Tomography (OCT)

18 February 2015

Optical Coherence Tomography (OCT) is one of the two major advances in ophthalmology over the past 10 years

 

The other is the discovery of Avastin (or Lucentis) – an injection into the eye that prevents the proliferation of destructive new blood vessels within the eye e.g. in macula degeneration or diabetic retinopathy

 

The OCT permits high resolution 2-D and 3-D views of the retina allowing all of the retinal layers to be easily identified. This makes the OCT an invaluable machine in identifying abnormality in these layers and makes the non invasive diagnosis of most retinal diseases much easier. 

This patient presented after noticing small ring in the centre of their right eye vision. Using our regular examination techniques the eye looked normal 

 

Only when we used the OCT could we see this abnormality – it shows all of the retinal layers but especially it shows a hole that shouldn’t be there (compare to the picture of the normal left eye below) (For the expert this is an obvious pseudo lamella hole at the macula caused by traction of a small epi-retinal membrane)

  

OCT also allows us to image and quantify the optic nerve head (ONH) and the retinal nerve fiber layer (RNFL) around the optic nerve head. Detected abnormality in the ONH or the RNFL can be the earliest sign of damage caused by glaucoma – but perhaps even more importantly – it can show more sensitively, change over time i.e. between visits

The cornea iris interface (the drainage angle of the eye) can also be imaged by OCT. This is relevant to the diagnosis of narrow angles that can lead to an acute form of glaucoma (sudden onset, very painful, red eye). Being able to identify these narrow angles before an acute angle closure attack means that preemptive (and simple) treatment to open the angle can be done by a medical eye specialist.

The first image below shows a wide open angle between the cornea and the iris and second shows a very narrow - but not closed angle

All our patients, here at McClellan Grimmer Optometrists will be offered an OCT exam when it is clinically indicated but especially where there is suspicion of glaucoma or where there is a strong family history of glaucoma, where there is unexplained central vision loss or where we need to further assess the macula or other retinal areas

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Glaucoma

11 February 2015

Introduction 

Glaucoma, in its most prevalent form, is a slowly progressing eye condition that causes damage to the optic nerve (optic neuropathy) resulting in permanent vision loss. It has been called the “silent thief” because it can slowly steal your sight without you being aware of it. By the time you have become aware that your vision is no longer normal, it is usually too late. 

Consequently, routine eye health examinations are of huge benefit. Glaucoma diagnosed early by your optometrist means that, while the condition cannot be cured, the condition can be arrested (with medical treatment) and your vision preserved. 

The prevalence of glaucoma in New Zealand is about 2% of the population but that prevalence increases with age. 

Understanding glaucoma
 
Light enters the eye through the pupil and casts an image on the retina at the back of the eye. This image is transferred to the brain via nerve fibres from the retina. These retinal nerve fibres band together as they exit the eye and become the optic nerve. The point where these fibres exit the eye is called the optic nerve head (or optic disc). The optic nerve head is the area where an optometrist can observe damage caused by glaucoma. 

Glaucoma is the name given to a number of different conditions that can result in damage to the optic nerve head. That damage starts as a painless, peripheral loss of vision which is why it so often remains undetected by the person developing glaucoma. The principle cause of damage to the optic nerve disc is elevated eye pressure. 

 

Types of glaucoma
 
Primary open angle glaucoma. This form of glaucoma is also called chronic open angle glaucoma. The eye produces (at a large muscle called the ciliary body) a fluid called aqueous. This fluid needs to drain out of the eye at the same rate as it is being produced. If this doesn’t happen, the pressure of the eye increases. For a particular eye there will be a critical pressure where the optic nerve head will become damaged resulting in vision loss.
 


Angle closure and angle closure glaucoma. This condition is quite rare in a white population (about 0.02%) but not so rare that an optometrist will be surprised to detect its risk factors. It is much more prevalent in the Eskimo and the Chinese. This is the acute form of glaucoma i.e. its onset is sudden. The patient will have a painful eye (and may be vomiting because of that pain); the eye is red, the pupil mid-dilated and not moving, and the vision “steamy”. Angle closure happens because of a sudden closure of the angle made by the iris and the cornea coming into contact with each other. This is the drainage angle of the eye and suddenly blocking it off means that eye pressure rockets. This constitutes a medical emergency with the patient hospitalised for a day or two. Failure to treat angle closure within a day can result in angle closure glaucoma. 
Chronic angle closure and angle closure glaucoma. In acute angle closure the drainage angle of the eye closes suddenly with the entire angle closed. In chronic angle closure the angle gradually closes and mimics the same pressure rise as in Primary open angle glaucoma. 

Secondary glaucoma’s. Primary glaucoma’s are primary because the cause of the glaucoma is not truly known. A secondary glaucoma is secondary because the cause of the elevated pressure can be found. These secondary causes can include:

 

  • Pigmentary dispersion syndrome. Occurs when pigment, usually from the iris, clogs up the drainage angle and so increases eye pressure
  • Pseudo exfoliation. Exfoliative material from the lens of the eye clogs up the drainage angle and so increases eye pressure
  • Trauma to the eye resulting in damage to the drainage angle structures
  • Medications with particular consideration to steroid use

Low tension glaucoma. This condition is not well understood. The optic nerve head disc shows signs of glaucoma damage but the eye pressure is within a normal range. A possible cause of this optic neuropathy may be compromised blood flow to the optic nerve disc. 

Risk factors. 

  • Having a parent, brother or sister with glaucoma
  • Being over 60 years old 
  • Being of a specific race: In Primary open angle glaucoma being a black American, in angle closure being Eskimo or Chinese
  • Having certain medical conditions: diabetes, thyroid disease, Raynaud’s disease or a history of migraine. 
  • Taking steroids over a prolonged period
  • A history of eye injury
  • Injuries that have involved sudden blood loss
  • Being near sighted (in angle closure) and far sighted in primary open angle glaucoma

What should I do to prevent getting glaucoma? 

You can’t prevent getting glaucoma but you can have it diagnosed early by having regular routine eye examinations especially if you have any of the risk factors above (with particular reference to having a family history of glaucoma or being over 60 years old). Today’s treatments are very effective at preventing any further glaucoma damage and so preserving your vision.