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MetWest Surgical passes Accreditation

On 26 October, MetWest Surgical, the first floor day surgery at MetWest Eye Centre, underwent an organisation-wide survey by the Australian Council on Healthcare Standards.  This involved two surveyors spending the day at the centre, observing the day procedure centre and checking all the procedures and policies currently used to ensure that they meet the current standards.  MetWest Surgical passed the survey and achieved another 3 years of accreditation.  Congratulations to all involved!

Some of the surveyors comments are below:

“MetWest surgical is a small boutique ophthalmic day surgery service ,located close to Blacktown Hospital,in an area zoned medical and dental precinct. The day surgery operates in a highly competitive and challenging market and maintains its’ market share by offering high quality specialist services. The service was exceptionally presented and the physical environment complimented the service provided. Staff were clearly strongly committed to the organisation and were very well supported and appreciated by management.”

Glaucoma

What is glaucoma?

Glaucoma is an optic neuropathy where intraocular pressure (IOP) is one of the main risk factors. It is the leading cause of irreversible vision loss in adults in Australia. Patients typically gradually lose peripheral vision without noticing until it encroaches on the central vision.

Common types of glaucoma are Ocular Hypertension, Primary open angle glaucoma Acute angle closure glaucoma Primary Angle Closure glaucoma Secondary glaucoma and Normal Tension Glaucoma or Normal Pressure Glaucoma

Ocular hypertension just means high IOP. A normal IOP is around 10-20mmHg and anything over 21mmHg is usually considered to be above normal. OHT implies a healthy optic nerve and therefore is not technically glaucoma, but OHT is often grouped with glaucoma as these patients will need monitoring for the risk of progression to glaucoma. The risk of conversion to glaucoma from OHT is around 10% over 5 years, therefore most practitioners do not treat OHT, unless they have additional risk factors.

Primary Open Angle Glaucoma is the most common form of glaucoma, it usually occurs in patients over the age of 40 years old. It is thought to be caused by reduced outflow at the drainage angle due to blockage at the cellular level, which in turn causes raised IOP and subsequently optic nerve damage. Glaucoma patients also seem to have a particularly susceptible optic nerve, such that they tend to be damaged more easily than others at moderately elevated IOP levels. Other factors such as mechanical stress, inflammation and reduced blood flow have also been associated with glaucoma.

Primary Angle Closure Glaucoma is a chronic form of glaucoma where the increased IOP is caused by a mechanical closing of the drainage angle by the iris due to abnormal morphology and overcrowding at the angle. This overcrowding may be due to a cataract or patients with small eyes (long sighted patients). Asian patients have a higher risk due to their abnormal iris morphology.

Acute Angle Closure Glaucoma happens when the drainage angle suddenly closes and the IOP goes up to a high level (around 40-50mmHg) in under an hour. The iris is pushed forward against the cornea due to a pressure shift. This is a very painful condition with associated redness, fixed mid dilated pupil, rock hard globe, vomiting and loss of vision. This is a medical emergency and requires an urgent referral.

Secondary Glaucoma is usually an increased IOP caused from ischaema (neovascular or rubeotic glaucoma), inflammation (uveitic glaucoma) or trauma (traumatic glaucoma). The mechanism here is again damage to the outflow channels.

Normal Tension Glaucoma (NTG) is thought to be a less IOP depended form of glaucoma, although lowering IOP still can prevent progression of glaucoma in many (but not all) cases. Here other factors also come into play to cause the optic neuropathy. Such as blood supply, mechanical stress and IOP fluctuations. Nocturnal hypotension is thought to be a major culprit in many cases and the role of 24 hr BP monitoring to reduce the noturnal BP dip may improve optic nerve perfusion. Obstructive sleep apnoea has been associated with NTG and the management of this condition with CPAP is thought to help. Other risk factors for NTG are migranes, Raynauld’s and anaemia.

How is glaucoma monitored?

Patients will have an automated Humphrey’s Visual Field test and OCT scan done of the nerve at most glaucoma follow up visits. The HVF tests the peripheral vision and tests the “functional” or subjective performance of the patient’s glaucoma. The OCT measures the thickness of the optic nerve and assesses the “structure” of the optic nerve. The eye specialist will assess the “structure” and “function” of the optic nerve to look for evidence of progression of the disease, where the nerve rim becomes more thin and the visual field defect becomes deeper and larger.

Patient undergoing OCT scan

Patient undergoing OCT scan

What is a disc suspect or glaucoma suspect?

You may see these 2 terms used in correspondence letters. This means that the Ophthalmologist has examined the optic nerve’s “structure” and “function” and decided that there is a feature suspicious  of glaucoma but no definite glaucoma diagnosis. The differential diagnosis is usually physiological cupping, physiological disc asymmetry or myopic tilt of the nerve. These patients usually have eye pressure in the normal range and are specifically normal tension glaucoma suspects. In this situation most specialists would choose to monitor patients for evidence of structure/function progression or evidence of IOP fluctuations. If there is no evidence of progression after several years, then the diagnosis of NTG can be excluded.

If there is optic neuropathy with visual field loss in the absence of any risk factors for glaucoma, then the specialist will need to be mindful of other causes. This would include compressional, toxic, inflammatory and infiltrative causes and the appropriate investigations would need to be done.

What is the treatment for glaucoma?

Eye drops are the most common treatment for glaucoma. There are 4 main categories of eye drops with Xalatan/latanoprost (prostaglandin analogue) the most common first line treatment. Its main side effects are redness, irritation, lash growth, increase pigmentation of the surrounding skin and cystoid macular oedema. Timolol (B-Blocker) is the most common second line treatment with shortness of breath and bradycarida the most common side effect. Other glaucoma medications include Alphagan (alpha-agonist) and azopt (carbonic anhydrase inhibitor).

Laser (selective laser trabeculoplasty – SLT) is also a good option for the treatment of open angle glaucoma. It has similar efficacy as Xalatan/latanoprost and can be used instead of drops to allow patients to be drop-free for several years, or in addition to drops in patients refractory to drops alone. SLT works by stimulating the outflow channel cells to increase outflow and reduce the eye pressure. It is important to note that the effects of the laser tend to wear off after a few years, after which the patient may need to start drops or have a repeat SLT treatment. Around 20% of patients do not respond or respond poorly to this laser. The laser is very safe, with most side effects such as inflammation and pressure spikes having a transient effect.

Laser Peripheral Iridotomy is a different laser ONLY used in primary angle closure glaucoma. It involved making a small hole in the peripheral iris to stop the mechanical obstruction of the channel by the iris. In angle closure, the pressure behind the iris pushes the iris forward, blocking off the drainage outflow angle. The iridotomy releases this pressure differential and the iris naturally falls posteriorly and opens up the angle. The management there after becomes similar to open angle glaucoma.

Trabeculectomy with Mytomycin C is a filtration operation, to create a channel to reduce the eye pressure. The channel allows fluid to enter the subconjunctival space forming a “bleb” which sits under the upper lid. This operation is usually reserved for patients who do not respond to drops and laser. There is a potential long term risk patients having a bleb. The bleb can thin out and begin to leak or become infected (blebitis) and this needs to be managed as an emergency.

Newer glaucoma procedures are known as MIGS – minimally invasive glaucoma surgery. These operations are safer than the traditional trabeculectomy but also do not work as well or as long. They are stents that bypass the blocked outflow filter (trabecular meshwork), to allow flow back into the normal drainage pathway. There are 2 stents on the market at the moment – iStent and Hydrus implants. Both currently need to be used in combination with cataract surgery due to government rebate regulations, but will likely be used as a stand alone operation in the near future. They reduce the IOP by small amounts and can often reduce the number of medications being used by 1. Therefore, they do not replace traditional surgery, but give a new option for patients with mild to moderate glaucoma.

 

Improving our efficiencies

Over the coming months, visitors to the centre will notice several changes occurring at the MetWest Eye Centre.

Firstly, our Reception desk is being relocated to make an easier transition for visitors to the centre, and to allow greater room for patient seating close to doctors consulting rooms.

Additionally, we are building two new rooms to house equipment regularly in use.  We hope that with the addition of these rooms, the flow of patients through the centre is made more efficient, as there has been a bit of a “backlog” with multiple instruments previously used in the one room.

Finally, the centre is making it’s way to paperless records.  This process has been taking some time, and it will take a bit of getting used to by the staff and doctors.  Please be patient with them!

Bringing clarity to cataracts

Cataracts cause 40% of cases of visual impairment in Australians aged 55 and over, and there are currently over two million Australians in this age bracket who suffer from untreated cataract, most of whom live in remote and regional Australia. Globally, cataract is the leading cause of blindness.

There are several different types of cataracts, including nuclear, cortical, sub-capsular and mixed cataracts.

Each type affects a particular anatomical location within the crystalline lens and has specific pathological processes and risk factors for their development.

In Australian patients, nuclear cataract is the most common type, and consists of a central opacification or yellow discoloration that interferes with visual function. Nuclear cataracts tend to progress slowly and affect distance vision more than near vision. Nuclear cataracts may induce myopia or a reduction in pre-existing hyperopia.

Increasing frequency of changes in the prescription of spectacles may be an early sign of cataract formation.

Cortical cataracts are spoke-like in appearance. Patients with this type of cataract commonly complain of glare, especially while driving at night. As a result, elderly patients often stop driving in conditions of low light and low contrast, but cannot always directly ascribe this to poorer quality of vision.

Posterior subcapsular cataracts are found more often in younger patients than either nuclear or cortical cataracts. Patients often have glare and poor vision in bright light, and near vision is typically more affected than distance. This type of cataract is more common in diabetic patients or those who have used systemic or topical corticosteroids. Posterior subcapsular cataracts progress more rapidly than other types, and can result in significant impairment in vision in only a few months.

Advancing age is by far the most important risk factor for cataract development, such that most individuals have some degree of cataract by their mid-60s. Other risk factors include diabetes mellitus; long-term use of topical, systemic, intravitreal, inhaled or oral corticosteroids; prior intraocular surgery; or significant ocular trauma.

The impact of a cataract on visual function can be subjectively assessed by self-reported functional status or difficulty with vision. However, patients may adapt to their visual impairment, and may fail to notice the functional decline that accompanies the insidious progression of a typical cataract. It is equally important to note that the impact of cataract is not limited to a reduction of distance visual acuity, as measured on a Snellen chart, this being a very narrow measure of a person’s visual function.

Other important facets of visual function including near vision, vision in dim lighting or situations of low contrast (e.g. dawn or dusk), glare, impaired colour vision or peripheral vision, and depth perception, can all be adversely affected by a significant cataract.

Loss of vision in the elderly can, in addition, be associated with a decline in physical and mental function, as well as a loss of independence in activities of daily living. Visual impairment caused by cataract is an important risk factor for falls and hip fractures, and a significant reduction in the rate of falls and fractures after cataract surgery has been demonstrated in randomised controlled trials. Drivers with visually significant cataracts are also 2.5 times more likely to have an at-fault motor vehicle crash, compared with drivers without cataracts.

In short, it is well established that physical function, mental health, emotional wellbeing, safety, and overall quality of life can be enhanced when visual function is restored by cataract extraction.

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PREVENTION

Preventive measures that impart even a modest decrease in the risk of cataract could have a large public health impact, given that millions of people are affected by cataracts in Australia, with numbers set to grow as our population ages.

Several studies show a link between smoking and nuclear cataract, demonstrating a dose-response effect. Smoking is also associated with an increased risk for posterior subcapsular and, to a lesser degree, cortical cataract.

Cumulative lifetime exposure to ultraviolet-B radiation has also been associated with cataract development. Therefore, brimmed hats and ultraviolet-B blocking sunglasses are reasonable precautions to recommend to all people.

There is some evidence that long-term multivitamins may decrease the risk of nuclear cataract but not enough to guide recommendations for their use.

However, little evidence exists that long-term high-dose antioxidant supplements (Beta-carotene, Vitamin E and C, lutein/zeaxanthin) or Omega-3 long-chain fatty acids, such as those in fish oil, decrease the progression of cataract.

There is also some evidence that a diet rich in fruits, vegetables, and wholegrains may reduce the progression of cataract, with vegetarian and pescatarian diets also conferring a protective effect compared with diets containing red meat.

HISTORICAL PERSPECTIVES

The history of cataract surgery is interesting and worth visiting. It is one of the oldest surgical procedures known, first documented in the 5th century BC. In ancient times, cataracts were treated with a technique called “couching”. The eye would be struck with a blunt object with sufficient force to cause the zonules to break, so that the lens would dislocate into the vitreous cavity, restoring limited but completely unfocused vision. Centuries later, the technique was modified so that a sharp fine instrument was inserted into the eye to cause the dislocation.

The first reported surgical removal of a cataract from the eye was in Paris in 1748, when the advent of topical anaesthesia made the procedure more practical and palatable. Using the early techniques, the entire opaque lens was removed in one piece using an incision that went halfway around the circumference of the cornea. It was critical that the lens remained intact during removal, so surgery was restricted to so-called ripe or “mature” cataracts.

This limited the surgery to only the most advanced cataracts. Since fine sutures did not exist at that time, patients were kept immobilised with sandbags around their head while the wound healed, with many eyes lost to infection. The early literature routinely documented the mortality rate from cataract surgery, an almost unheard of phenomenon in the current day, secondary to pulmonary emboli.

The most significant change in the modern era was the introduction of phacoemulsification surgery in 1967 by Dr Charles Kelman. In this technique, ultrasonography is used to break the lens into minute fragments that can be aspirated (termed phacoemulsification). A combined ultrasonographic irrigation and aspiration hand piece allows the removal of any lens (hard or soft) through a small incision. This revolutionised cataract surgery, with modern day corneal wounds routinely less than 3mm in size.

Originally, no intraocular lens implants were used following cataract surgery, and patients had to rely on “Coke bottle”- thick hyperopic glasses. At a later date, thanks to the pioneering work of Howard Ridley, a British ophthalmologist, intraocular lenses were developed. Ridley recognised that the penetration of shattered fragments from airplane windshields into the eyes of World War II fighter pilots did not always lead to damage, and went on to create the first artificial lens from the same material.

The evolution of smaller surgical incisions was matched by the development of new lens implants that could be folded to allow the lens to be inserted through a tiny wound. At present, commercially available lenses can be inserted through wounds as small as 2mm.

The predominant method of cataract surgery used in the developed world today is suture less small-incision phacoemulsification with foldable intraocular lens (IOL) implantation. Cataract surgery is one of the commonest and most effective procedures in modern medicine, and in 2013–14, approximately 160,500 cataract surgical procedures were performed in Australia.

The primary indication for cataract surgery in the developed world is visual function that no longer meets the patient’s needs, and for which cataract surgery provides a reasonable likelihood of improved vision. Other indications for cataract removal include clinically significant anisometropia (a large difference in the focusing power of the two eyes), or presence of a cataract that interferes with optimal diagnosis or management of posterior segment conditions such as diabetic retinopathy. A cataract that causes inflammation or secondary glaucoma should also be removed.

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PRE-OPERATIVE MEDICAL EVALUATION

The pre-operative evaluation of the cataract patient includes a detailed history, a comprehensive ophthalmic assessment, and discussion of the natural history of the condition, expected recovery, and potential risks. Presence of systemic co-morbidities such as uncontrolled diabetes, hypertension or unstable angina should be sought. The surgeon also pays attention to the presence of a neck deformity or abnormal posture, significant head tremor, or claustrophobia – factors which may affect patient positioning intra-operatively.

Routine preoperative laboratory testing is not indicated, and discontinuation of antiplatelet agents or anticoagulants prior to cataract surgery is generally not required. While several studies demonstrate a higher risk of subconjunctival haemorrhage, current available evidence does not support an increased risk of vision-threatening complications in association with these agents.

During the pre-operative assessment, the ophthalmologist routinely assesses the possibility of intra-operative floppy iris syndrome, which is strongly associated with the use of systemic alpha-1 antagonists, most commonly for symptomatic treatment of benign prostatic hyperplasia. Floppy iris syndrome results in progressive pupillary constriction during cataract surgery with possible prolapse of the iris through the corneal incisions, and is associated with a higher risk of intra-operative complications.

However, it can be safely managed with additional measures that maintain pupillary dilation during surgery. It is important to note that discontinuing alpha-1 antagonists preoperatively does not prevent floppy iris syndrome, which may occur long after drug cessation.

INTRAOCULAR LENS POWER CALCULATION

Modern-day cataract surgery is a very precise operation. Patients routinely expect and demand predictable refractive outcomes, and desire reduced dependence on spectacles post-operatively. Knowledge of the patient’s vision requirements, hobbies, and personality are crucial in selecting an appropriate intraocular lens and an optimal refractive outcome.

Accurate measurement of the eye’s axial length and central corneal power, combined with the selection of an appropriate intraocular lens implant, based on a power calculation formula, is the minimal requirement to achieve the targeted postoperative refraction. This is done preoperatively using a high-resolution non-contact optical biometer, which uses a laser to make precise measurements of the eye. Modern intraocular lenses have an in-built UV filter, as well as aspheric optics. The latter improves mesopic (low light condition) and scotopic (dark condition) contrast sensitivity and visual quality by reducing optical aberrations of the eye.

Modern day implants also correct the patient’s underlying refractive error (short-sightedness, long-sightedness, and astigmatism). Additionally, use of presbyopia-correcting IOLs (multifocal or extended focus lenses), or monovision may improve quality of life by reducing glasses dependence after cataract surgery.

Monovision involves correction of one eye for distance vision and the other eye for intermediate or near vision. The success of monovision depends on blur suppression, where the blurred image from one eye does not interfere with the image from the in-focus eye. Patients with a history of successful adaptation to monovision with eyeglasses or contacts lenses are particularly well suited for this modality.

However, both multifocal and monovision techniques come with some optical side effects and whether the reduced dependence on glasses outweighs these side effects will vary between patients, making careful and considered patient selection a critical step of successful cataract surgery.

In the past, a sharp fine instrument was inserted into the eye to dislocate the lens.

SURGICAL TECHNIQUE

Cataract surgery is generally completed as a day procedure under local or topical anaesthesia. Intravenous sedation is commonly used to complement the anaesthesia in order to optimise the patient’s surgical experience and cooperation.

The operation generally takes 15 to 20 minutes to perform, and is associated with minimal to no post-operative pain. In many cases, the patient’s vision is improved even at the first post-operative day, but continues to sharpen further over a few days.

A recent adjunctive tool used in cataract extraction is a femtosecond laser, which can be used to construct the corneal incisions and to perform some of the steps in cataract surgery including opening of the lens capsule and cleaving of the cataract. There is still controversy around the relative benefits and disadvantages of laser-assisted cataract surgery, and while it is associated with more reproducible wounds and more predictable lens centration, this is yet to translate to a meaningful clinical benefit for the patient. At present and as a relatively new technology, it is also associated with a significant financial cost that is borne directly by patients, although this may change in the future.

As with any operation, risks exist. Post-operative endophthalmitis (infection of the whole globe), although rare, is a potentially serious complication, occurring most commonly at three to five days post-operatively. It results in profound and rapid vision loss that may become permanent if not urgently treated.

The clinical triad of a red eye, severe vision loss and significant eye pain (not irritation) in the context of recent cataract surgery, should alert the general practitioner to the possibility of endophthalmitis and the patient should be referred immediately to the ophthalmologist or to a specialist unit for urgent assessment and treatment i.e. a vitreous biopsy for microbial culture and intravitreal injection of antibiotics.

In summary, cataract is an almost universal finding in the elderly population, but also affects younger age groups, especially diabetic patients and those taking long-term corticosteroids. Symptoms or signs of cataracts should ideally be looked for in all patients over the age of 65 in the general practice setting and be referred for further assessment if visually significant symptoms exist.

Dr Dana Robaei is an ophthalmologist based in Sydney. Her expertise includes complex cataract surgery, corneal transplantation and diseases of the anterior segment of the eye.

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