[This is just one of many articles in the author’s Astronomy Digest.]
In the autumn of 2017 my optician told me that I was developing cataracts in both eyes but with the right eye more advanced. I only really become aware of this when, at a star party, I looked up at a first quarter Moon and saw a coloured halo around it – but when I closed my right eye it disappeared! Visually testing some 80 mm refractors, I was surprised to find no false colour at the edge of the Moon when using an f/5 achromat which is my autoguiding scope. Photographs showed that the false colour was there. It appeared that the cataracts were limiting the range of colours that my eyes were sensitive to and, when one eye had had the cataract removed, it was obvious that when observing a white wall with the other it appeared yellowish in colour.
I should say at this point that for most of my life I have been myopic, requiring strong (~-3.5 dioptres) lenses to correct my sight – which was then excellent. I suffered very little astigmatism and so could use a telescope eyepiece without wearing glasses. I used three pairs of prescription glasses.
- A bifocal pair for distance and reading. (Though I tended not to wear them when reading.)
- A pair of photochromic (darkening in bright light) glasses corrected for distance vision which I used as sunglasses when out and about.
- A pair to use when working with my computer and 24 inch HP monitor at one and a third arm’s length distance.
One advantage of fairly strong myopia is that my ‘near point’ without glasses was just a few centimetres so I could clearly see very close up objects – sometimes a real asset and one which I now miss.
The following autumn, my optician referred me to have both cataracts removed and the first of these was carried out swiftly in a private eye clinic on behalf of the NHS, so no cost was involved. The operation took, in total, about two hours. First a tablet was replaced under the lower eyelid to dilate the pupil. After a while to allow for its effects, drops were placed in the eye to act as a local anaesthetic. I then was taken to talk to the surgeon who selected a replacement lens corrected for distance vision. Finally I was taken into the operating theatre and lay down with my head supported on a pillow. A sheet was laid over my head and hole cut above the eye – which had had an arrow pointing down to it. I was told to keep very still and look upwards towards a light whilst, initially I believe, an ultrasonic beam was used to break up the cataract. It transpired that the central part of the cataract had become very hard and required full power to break it up. The remains were then sucked out and the replacement lens inserted. I was given a pair of eye drops to use each day for the next three weeks.
The following morning, the eye was incredibly sensitive to light − as my operation was late the previous evening it may be that the pupil was still dilated – but this wore off by the afternoon and I began to see clearly by that evening so the operation had been a success and the eye recovered very quickly.
I had realised that my right eye would no longer need a lens for distance vision so, prior to the operation, I had a pair of glasses altered with a right eye lens of zero dioptres. Due to refurbishment of the clinic where the cataracts were being removed it was 6 weeks before the left eye was operated on. This was an interesting period as, without glasses, my right eye had near perfect distance vision and my left eye could be used for reading or close-up use.
Following the operation on my left eye, which was also successful, one has to wait for some weeks to let the eye settle down before new glasses could be prescribed. Very little correction (~1/4 dioptre) was required for distance vision (and often, I no longer wear glasses) but I would now need glasses for near vision. I thus had two prescription glasses made for me.
- A bifocal pair for general use for both distance and reading.
- A photochromic pair for out and about use and which act as variable strength sunglasses. With very little optical strength these have very thin and light lenses making a notable difference from my previous pair – but can still get surprisingly dark under bright sunlight.
As the two eyes were nearly identical I could now buy low cost non-prescription glasses for close vision requirements.
- A pair for use with my computer monitor. (+2 dioptres)
- A pair for reading. (Not really necessary but easier to use than the bifocals. (+2.5 dioptres.)
- A pair for really close-up work of +3.5 dioptres. (Sometimes useful as, for example, fitting a micro USB plug into camera for use with an intervalometer and checking the sharpness of stellar images on a camera screen.)
There is no doubt that colours have become more vibrant and an astronomer friend maintains that he can see stars which are about ½ a magnitude fainter than before his operations. I suspect that that this is true for me too. The night sky has become both clearer and brighter!