Presbyopia, also called “old-sightedness” or “laohua” in Mandarin, is a condition that affects everyone without fail, around the age of 40 year old. Although not everyone experiences the same symptoms, the fundamental causative factor is the same, which is a decline in the accommodation or “autofocus function” of the natural lens in our eyes.
In reality the human eye’s “autofocus” ability starts to decline from a peak range of more than 1500 degrees at the age of 10 years old. For a normal reading distance of about 35 cm, we need around 300 degrees of autofocus power, which generally is what a 40 odd year old still possess. After this age, the autofocus ability needs compensation from reading aid, but how much reading aid is required depends on what the “baseline” eye power is.
By “baseline” I mean what power the eye has before the onset of the “laohua”. Short-sightedness and long-sightedness are the two main refractive errors that affect the degree of inconvenience one gets with the onset of “old-sightedness”. It is a reversal of fortune of sorts; those who had always been plagued by short-sightedness and had to wear corrective glasses for it will find that their worsening near vision is improved by removing their glasses now.
Those who wear contact lenses or had LASIK or other vision correction surgeries done fall into a “corrected and hence perfect” eyesight category before the onset of presbyopia. This group resembles those who have long-sightedness, which is the opposite condition versus short-sightedness. In general those who have “perfect” or long-sighted eye power see far well in their adulthood, but once they reach 40, their “laohua” becomes more obviously symptomatic.
Treatment for this condition can be as simple as changing to the appropriate progressive glasses, or even progressive contact lenses. Another strategy is to choose “monovision” by spectacles or contact lenses, which is when one eye is targeted for sharp distance vision and the other for sharp near vision. This can even be permanently created by undergoing LASIK etc. The brain will usually merge the two eyes and the resultant images become reasonably clear for almost all distance. However, not everyone is suitable for this. Those who have a very particular preference for clear vision in BOTH eyes may experience headaches and discomfort with this method.
Another option is by undergoing eye surgery using cornea inlays. These are inserts that can be implanted in the cornea i.e. the front clear window of the eyeball. Usually this is performed in the eye meant for near focus. It is vaguely similar to monovision, but for the fact that the “near eye” has a larger range of distance.
For those who already have some degree of lens hardening or cataract, a cataract surgery can be the best treatment for “laohua”. An artificial lens implant is de rigueur in cataract surgery; all cases need a lens implant after the cataract is removed, to restore the focusing power of the eye. Presbyopia-correcting intraocular lens (IOL) is one of the best inventions in modern Ophthalmology. The variety of choices and lens designs is a boon. With proper care and guidance by an experienced cataract surgeon, most patients will benefit from spectacle freedom through the use of these premium lenses, and be returned to their younger state of vision, pre-“laohua”.
by Dr Daphne Han – Senior Consultant Ophthalmology