Ocular Coherence Tomography (OCT)
Topcon - Ocular Coherence Tomography (OCT) - OCT is a diagnostic tool that provides images of the back of the eye of exceptional quality. This information is useful in diagnosing and monitoring retinal diseases. With the OCT a laser beam of light is focused on the retina. This beam is split with one beam being the reference to the other passing through the pupil and the various layers of the retina. The reflected beams are analysed and provide an exceptionally detailed cross sectional view of the retina and this allows us to demarcate any pathology.
OCT is helpful in diagnosing new retinal diseases and monitoring response to treatment. This is particularly the case with diabetes and with macular disease when administering the new "anti-VEGF" drugs like Lucentis Eylea and Avastin intravitreally. This investigation is often used every 4 to 6 weeks to monitor progress. The use of an OCT is quick painless and non-invasive.
OCULAR COHERANT TOPOGRAPHIC ANGIOGRAPHY (OCTA)
OCTA is an even more exciting new diagnostic tool that ushers in a new era of retinal care. Ultra clear 3D microvascular visualisation provides imaging even beyond that what Flourescein angiography can provide with no risk from the injection of a contrast medium. It is quick and totally safe and is advancing our ability to see deeper into the retinal circulation with no need for injections as has been the case up to now.
Visual Field Testing
Visual fields are checked sequentially to monitor for various diseases of the eye particularly diseases of the optic nerve.
Most patients complain they do not like doing field tests however, a field test is essential to demarcate a field defect that often starts in the periphery and might progress centrally and only be detected late in the disease. One can have normal central vision with loss of the peripheral field of vision resulting in a tunnel vision type effect. One can have perfect central vision until late in glaucoma and the field test is therefore essential in ensuring that adequate therapy is provided early enough. These tests can be difficult to perform and there is a learning effect. Results are usually more accurate after a few fields have been successfully performed.
We have recently discovered that the thickness of ones cornea can influence the pressure reading and lead to inaccurate measurements either under or over estimating the intraocular pressure. For this reason corneal pachymetry is performed on all glaucoma patients as a baseline and subsequent to this as required. The test is simple, painless and takes a few seconds only. Pachymetry is an integral part of a glaucoma assessment.
Corneal topography is an accurate way of assessing corneal curvature and anatomy using computer analysis.
A Corneal Topographer projects a series of illuminated rings onto the corneal surface. These are reflected back into the instrument and analysed by a computer. A topographic map is generated of the surface of the eye. This is an objective way to assess astigmatism and whether corneal scarring or keratoconus is an issue. This diagnostic procedure is also essential when assessing the front of the eye with a view to performing refractive procedures. This instrument is essential in calculating intraocular lens powers in the context of previous refractive surgery (such as Lasik).
A Topcon digital camera is used for standard retinal photography, photographs of the optic nerve head and for Fluorescein angiography. This is a routine therapeutic tool for diagnosis and treatment of macular disease as well as all other forms of retinovascular pathology including diabetic retinopathy.
Therapeutic Lasers – Argon and YAG lasers
L.A.S.E.R is an acronym for Light Amplification by Stimulated Emission of Radiation. This is concentrated light energy of one wave length. Therapeutic lasers are used extensively in ophthalmology and various types exist. They essentially use different wave lengths and depending on the duration of the beam either burn, coagulate, cut or disrupt any number of ocular tissues. All lasers can be exquisitely aimed at a particular tissue and therefore are useful in accurately dealing with specific pathology.
Lasers are used for retinal treatment as in diabetic retinopathy and Age Related Maculopathy where an Argon laser is used. Retinal diseases are usually treated using a green laser which coagulate areas of bleeding, haemorrhage or leakage. Glaucoma and anterior segment diseases are often treated using a YAG laser. This is a red laser. Our current YAG laser is known as a TANGO system which is used to perform selective laser trabeculoplasty for open angle glaucoma. The YAG laser can be used for other glaucoma interventions including a peripheral iridotomy or disruption of any number of tissues in the anterior segment of the eye. The YAG laser is often used to perform a capsulotomy disrupting an opaque posterior or anterior capsule post cataract surgery.
Laser therapy is performed on site at the Kite Street Specialist Centre. It is a day procedure and the patient is usually treated under local anaesthetic using topical anaesthesia. Most laser procedures performed are painless, well tolerated and require only simple analgesia afterwards if anything is required at all.
A-Scan biometry measures ocular dimensions before cataract surgery. We currently use an IOL Master which is a non-contact diagnostic laser. This assists us in measuring the curvature of the eye and the length of the globe thereby accurately determining which lenses are to be used at the time of cataract surgery.
The A-Scan can also be performed by a immersion with the probe placed in the device between the upper and lower lids within a saline bath in special circumstances. This is an essential measurement prior to any cataract surgery and will enable us to source the ideal intraocular lens. This will be discussed in depth prior to planning of any cataract procedure.