Seeing without specs

by Roy Carpenter

Roy Carpenter is an Optometrist at the Family Medical Centre in Quinta do Lago

For many people spectacles are a necessity rather than a desirable acquisition in order to correct their sight – but nowadays this is not necessary as other means can be used to correct focussing problems.

Contact lenses have been around for over a hundred years and since the 1960s have been routinely fitted to correct both long and short sightedness. Initially these were the haptic lenses which fitted over the whole eye and gave good results over a limited period of wear – normally around six to eight hours – but which were difficult to fit (hence expensive), often involving making a mould of the eye, and then took a long period of adaptation due to the gradual settling of the lenses on the eye, requiring frequent adjustments. These are now only rarely fitted for some pathological conditions and also for deep diving where more modern lenses may be dislodged or distorted by the increased pressure.

The mid 60s saw corneal lenses, which fitted only the centre of the eye, and with the development of which I was involved when working as a trainee optician in the practice of one of the world’s leading pioneers in London. These small lenses (around 9.5mms in diameter) could correct most prescriptions and be worn for pretty much all day, but they did have limitations – because they move around on the cornea they could, over time, cause central abrasions and also dust could get between the lens and the eye causing considerable pain in windy, dusty conditions.

Astigmatic designs

In the 1970s, gas permeable materials which allowed oxygen to pass through them rather than lens movement exposing the cornea on blinking meant that lenses could be fitted tighter thus lessening, but not completely removing, the dust problem.

By the 1980s soft lenses started to come on the market which were larger and ‘draped’ on the eye thus largely removing the dust problem and the lid irritation of the ‘hard’ lenses. This very property however meant that only limited prescriptions could be fitted because any irregularities on the eyes surface were transmitted through the material and it was not until the turn of the century that astigmatic designs were perfected to overcome this problem and now these are the lenses of first choice.

However, when I moved to the Algarve, I found that even these lenses were generally only worn for limited periods of time without problems. The answer was obvious to me – atmospheric conditions in Mediterranean latitudes are different to Northern climates for which most lenses were designed – it is hotter, drier and dustier. To overcome this I went back to my suppliers and got them to produce lenses which have a higher ultra-violet protection and higher water retention to reduce drying out.

All day wear

After some teething problems involving frequent breakages and difficult handling, we are now supplying lenses which can normally be worn comfortably all day, even in the height of summer. Dust, causing degradation of the lens surface, is still a problem which we are overcoming by producing a wider range of prescriptions in daily disposable (throw away) lenses.

Nearly all problems can now be handled, including presbyopia (middle-age sight) which interestingly here due to the bright light I mainly correct with a monovision principle, fitting the dominant eye for distance and the non-dominant for near, whereas in England I normally used bi- or multi-focal lenses.

A lot of people now undergo laser corrective surgery (which will be discussed in a later article), wherein the corneal surface is reshaped using a laser like a lathe on the eye and eliminates the handling problems of lenses. However because the optical effects of both procedures are very similar I always advise potential patients to initially try contact lenses – which can easily be discontinued or altered if the effects are not what they want – before committing themselves to surgery which is difficult, or indeed impossible to reverse or change if they are not happy.

Finally, as in all things medical, ensure that your practitioner is currently registered, proficient and has full professional indemnity insurance because even in this modern world not everything can be 100 per cent guaranteed.