New lens to help old eyes available in Singapore

SINGAPORE - A water-filled lens implant - about one-sixth the width of a contact lens and less than half the thickness of a human hair - may help the ageing eye see better at close range.

The age-related loss of ability to focus on near objects is called presbyopia. It is believed to be the result of the lens stiffening and becoming less elastic with age, usually from 40 years of age.

A person with presbyopia experiences blurred vision at near distances, such as when reading, sewing or working at the computer.

The Raindrop near-vision inlay is implanted into the cornea of a patient's non-dominant eye. The dominant eye is the eye that looks directly at an object while the other eye, the non-dominant one, looks at the same object at a slight angle.

The new inlay is placed under a flap on the surface of the cornea, created by a femtosecond laser, identical to that used in Lasik. But unlike in Lasik, the laser will not be used to remove tissue below the flap to reshape the cornea and correct its refractive error.

The inlay has no refractive power, but it raises the centre of the cornea - the clear part of the front of the eye - by 30 microns, which is enough to change the way that light passes through the eye and improve near vision.

When engaging in near-vision work such as reading or writing, a person relies on the centre of the cornea.

Dr Julian Theng, chairman and group medical director of the Eagle Eye Centre at Mount Alvernia Hospital, said the inlay changes the curvature of the cornea, making the cornea multifocal so that it can focus on both near and far objects.

As other parts of the cornea are untouched by the inlay, the vision for far objects is unaffected.

The inlay is available in Europe and is currently in a phase three clinical trial in the United States.

In Singapore, since April this year, Dr Theng has implanted it in 15patients in a trial on Asian eyes, which he was invited to carry out by the inlay maker, ReVision Optics, a private corporation based in the United States.

Dr Theng, who plans to track 20patients over a year, said a study on Asian eyes is important because they have been observed to have a higher tendency to develop inflammation, for reasons which are not known.

NOT FOR ABNORMAL CORNEAS

In an earlier study of 20 patients published in the Journal Of Refractive Surgery earlier this year, all eyes with the implant achieved uncorrected near visual acuity (sharpness) of 6/12 or better a week after the procedure and up till a year later.

A person has visual acuity of 6/12 if he can read a line on the 11-line Snellen eye chart at 6m, and someone with normal visual acuity of 6/6 can do so at 12m.

One patient who was dissatisfied with the resulting vision had the implant removed.

At one year, all 19 remaining patients were satisfied or very satisfied with their overall vision, and 16 of them seldom or never wore glasses. Only two patients reported moderate visual symptoms, such as glare, halos or blurred vision.

Preliminary results of the first 11patients from Dr Theng's trial here have been similar.

Patients experienced glare and halos for a week to a month, but these disappeared over time.

A patient whose inlay was placed incorrectly complained of worsened near vision. She declined to have it repositioned and had it removed.

The inlay cannot correct existing refractive errors related to the shape of the eyeball - myopia (short-sightedness caused by an eyeball that is too long); hyperopia (long-sightedness caused by an eyeball that is too short); or astigmatism (when the eye surface is not round but resembles a rugby ball - more curved on one side and flatter on the other side).

If people with these problems and presbyopia want to be able to see both near and far objects without using spectacles or contact lenses, they are strongly recommended to undergo Lasik to correct these errors before the inlay is inserted at the same sitting.

But patients who have cataracts and presbyopia are better suited to have their cloudy eye lens removed and replaced with a multifocal lens implant, Dr Theng said.

Those who develop cataracts after having the inlay inserted will have no issue undergoing cataract surgery.

Dr Theng will not offer the inlay to people whose corneas are abnormal - for instance, too thin or scarred by previous infections.

Their healing process is "less predictable" and they are more prone to developing dry eyes temporarily after procedures to the surface of their corneas, he said.

CENTRING OF INLAY IS AN ISSUE

CENTRING OF INLAY IS AN ISSUE

No studies have compared the safety and efficacy of the inlay with other types of treatment for presbyopia.

But the visual results from Raindrop are comparable with those achieved with multifocal contact lenses, Dr Theng said.

Spectacles are the most commonly used method to treat presbyopia, followed by contact lenses, because they are less invasive than surgery.

Cost may also be a factor for some. A pair of spectacles costs from as low as $10 to almost $3,000, while existing surgical methods cost between $900 and $2,800 per eye.

The cost of the Raindrop near-vision inlay and the procedure to insert it is about $3,200.

However, surgery is increasingly being done, possibly because patients want the convenience of not relying on spectacles or contact lenses, Dr Theng said.

Patients can opt for Lasik to correct presbyopia, in which a laser is used to sculpt the cornea, effectively creating a multifocal lens on the eye itself.

Patients can also choose from two other types of corneal inlays, the Kamra and the Icolens (Options to boost vision, Fans on how they cope with presbyopia).

Centring of an inlay is an issue, said Dr Jerry Tan, an ophthalmologist at Camden Medical Centre, who does not use any inlays.

In the human eye, the line of sight changes from person to person and depends on the size of the pupil and the distance at which a person reads, he said.

So, an implant that is well-centred for reading in the day may become "decentred" at night when the pupil enlarges from a lack of ambient light, he said.

However, Lasik changes the cornea permanently, unlike a corneal inlay, which can be removed from the eye in a subsequent procedure if required, Dr Theng said.

The Kamra can result in corneal melt - a change in the shape of the cornea - though this is not common.

So far, no major eye complications, including corneal melt, have been reported in patients who have had the Raindrop near-vision inlay, said Dr Theng.

MORE STUDIES NEEDED

MORE STUDIES NEEDED

For patients who need Lasik to correct other refractive errors before the inlay is inserted, they can have both done in one sitting if they are using the Raindrop inlay.

But if they are using the other methods, they have to wait for a month after Lasik before the inlay can be inserted.

For those who do not need Lasik, small pocket incisions in the cornea, rather than a flap, are needed to put in the Kamra or Icolens.

These are less likely than a flap to weaken the cornea, said Dr Theng.

The Singapore National Eye Centre (SNEC) said it takes a conservative approach in offering corneal implants for presbyopic correction. The centre is awaiting one-year results on the Kamra before considering its use.

The SNEC also believes more studies are required on Asian eyes, which are known to have a higher risk of hyperopic shift (increasing long-sightedness) and haze formation (clouding of the normally clear eye surface) from the use of corneal inlays.

But the Raindrop inlay has helped real estate agent Alan Chia, 60, who had perfect vision until presbyopia hit him in his early 50s.

The father of three grown-up children said he became "half-blind" without his reading glasses.

As he was forgetful and wanted to avoid a situation where he was without his glasses, he kept a pair in different parts of the house, his car and even his wife's handbag, amassing more than 20pairs in a few years.

In April, he had the new inlay put into his left eye, which took no more than five minutes. A visual test twomonths later showed that he has regained his perfect vision.

He quipped: "Now there's no way I can lose my glasses because they are in my eye."

joanchew@sph.com.sg


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