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Saturday / January 29.
HomemicontactThose Pesky Cyls

Those Pesky Cyls

Professor Nathan Efron wonders whether his ophthalmic journey of retinopexy, cryopexy, vitrectomy and IOL surgery really is over, or whether he will require further refractive surgery to eliminate residual astigmatism in each eye.

I returned to the clinic a week after my left eye intraocular lens (IOL) surgery with excited anticipation. This would be my first chance to have a refraction performed and to discover how close I ended up to our goal of perfect emmetropia in that eye. At this visit I was only going to be seen by the tech.

We started with the Humphrey Autorefractor, which gave a readout of R -1.00/-1.00 x 78 L +0.50/-0.25 x 20. We then proceeded to do a subjective refraction, which was R -1.00/-1.00 x 90 L +0.25/-0.25 x 20. Vision was recorded as R 6/6 L 6/5.

This finding of almost perfect emmetropia in my left eye was not necessarily good news. You see, it was only one week since my operation, and it would be a while before my eyeball fully recovered and my refraction fully stabilised. Given that my right eye shifted about -0.75 in the three months following IOL surgery in that eye, would this mean that I was going to end up more myopic in my left eye, perhaps with a greater cyl?

Unfortunately, my final stabilised refractive status it is not an entirely happy situation…

Well, there is no quick answer; it is impossible to predict the final refractive outcome. If there is one thing I have learned in this long ophthalmic journey, it is that one has to be patient and give the eye time to settle following any procedure.

The tech completed further testing, including intra-ocular pressure measurement –R&L 11 mmHg; slit lamp biomicroscopy – slight oedema around the area of the limbal incision but otherwise all looked quiet; and optical coherence tomography – slight macular oedema and still not a complete foveal pit, but otherwise fine. I was advised to return for a follow-up examination in one week, when I would also see Bill.

When I presented for my follow-up visit 12 days later, my refraction had not changed. Bill confirmed the posterior capsular wrinkling and suggested we go ahead with YAG laser capsulotomy straight away. Even through it was only 12 days since my cataract operation, he could see no reason to delay the procedure.

We also discussed what I considered to be sub-optimal vision in my right eye. Bill suggested I think about trying to eliminate the residual astigmatism in that eye with laser refractive surgery. Maybe my ophthalmic journey was not yet over after all… but more on that later.

After signing a consent form, I was led into the small YAG lasering room. About three minutes later it was all over. It was a repeat experience of loud clicking and bright red flashes. I was left with a few random floaters that I hoped would dissipate after a few days, just as happened with my right eye. I was prescribed an eye drop regime of Pred Forte four times per day, but since I was already doing this following my IOL surgery, I did not need to alter my eye drop regimen.

(Click here to view image)

Fast Forward Sixteen Months

When I started writing miblogs, they were more or less contemporaneous with what was actually happening in real time. However, with the accelerated time frame of my various operations, largely to alleviate visual discomfort, these blogs are now lagging somewhat behind my surgical escapades. So, I can now declare that, as I write this blog, it is 16 months since my final ophthalmic procedure.

Fortunately, my retinas are anatomically intact. Figure 1 shows full retinal thickness maps, generated using optical coherence tomography, at various stages of my ophthalmic journey. The slightly bluish hues in the far right maps reveal my retinas to be a little thinner compared to when I started, presumably as a result of the bilateral epiretinal membrane peels. The uneven thickness profile of the final map for my right eye is perhaps consistent with the sub-optimal vision in that eye.

Unfortunately, my final stabilised refractive status is not an entirely happy situation.

My refraction eventually stabilised about nine months following my final surgical procedure, and has not altered to this day. Uncorrected vision is recorded as R 6/30-1 L 6/5. My refraction has ended up as

R-1.25/-1.00 x 75 L +0.25/-0.50 x 45, and corrected visual acuity is R 6/5 L 6/4.

In terms of best sphere refraction, the outcome is exactly as planned, with a -1.75D myopic reading right eye and Plano distance left eye. But sadly, I am left with pesky cyls of 1.00D in my right eye and 0.50D in my left eye.

For generally getting around and going about my normal day-to-day activities, that amount of astigmatism is not really a problem. Everything in the distance generally looks clear, including television.

The problem is that my vision is somewhat degraded at near. Unaided near vision is R N6 (slow) L N14. Corrected near vision is R N4 (slow) L N4. The reduced unaided vision in my right eye is due to the ‘double jeopardy’ situation, whereby near vision is degraded by 1.00D astigmatism as well as my annoying flying angel of death. Even in good lighting, seeing text on my iPhone, scrutinising dials, readouts and the LCD display on my digital camera, and reading small newspaper print, is all a bit of a struggle. When I looked at a test card with a near correction in a trial frame, everything seemed so much clearer.

With all of this in mind, I recently decided that I needed to find an optical solution to improve my near vision. A key motivation for proceeding with all these eye operations was to avoid having to rely on glasses or contact lenses, which I had been doing for the past 45 years. I tried a contact lens to correct the astigmatism in my right reading eye, but this helped only marginally and of course failed to obviate the adverse impact of my flying angel of death.

Another option was an anterior chamber intra-ocular lens. I did a little reading around this and was not convinced that a satisfactory visual outcome could be achieved. And anyway, I had had enough of ocular surgery!

For a while I seriously contemplated laser refractive surgery. Bill referred to this as ‘ASLA’ – an acronym I had not heard before, which I was told stands for ‘advanced surface laser ablation’. From what I can gather, this is just a fancy name for photorefractive keratectomy (PRK). I decided against this for four reasons: (1) I was not convinced that the accuracy of this technique, or any other refractive surgery procedure for that matter, is sufficient to guarantee the elimination of all astigmatism; (2) I have had enough eye surgery already; (3) it is painful; and (4) I am acutely aware of the physiological damage caused by laser refractive surgery, and am not particularly keen to subject my eye to this.

Frightened By My Own Research

Let me expand on this last point. The cornea contains a rich plexus of nerves at the base of the epithelium, just anterior to Bowman’s layer. I happen to know this because I have been researching this tissue layer for the past 15 years using a laser scanning corneal confocal microscope. In fact, I was the first to describe this layer in the literature 14 years ago, in what has become one of my most highly cited papers.1

I have also published papers on the impact of laser ablation surgery on this nerve layer, and the results are not pretty!2,3 PRK, or ASLA as it is now called, causes complete ablation of this nerve layer, resulting in substantially reduced corneal sensitivity and dry eye symptoms for 12 months following the procedure. And on top of this, it takes about five years for subbasal nerve plexus to fully regenerate back to normal. I could not countenance the thought of obliterating such a beautiful tissue structure – that I have long been so passionate about in a research context – in my own eyes.

The only other viable solution was glasses, which I had been trying so hard to avoid. I will tell you about my ‘back to the future’ experience wearing glasses in my next, penultimate blog.

Professor Nathan Efron AC is a researcher at the Institute of Health and Biomedical Innovation and School of Optometry and Vision Science, Queensland University of Technology. He is currently President of the Australian College of Optometry and Vice-President of the International Society for Contact Lens Research.

References

1. Oliveira-Soto L, Efron N. Morphology of corneal nerves using confocal microscopy. Cornea 2001; 20: 374-384.

2. Perez-Gomez I, Efron N. Changes to corneal morphology following refractive surgery (myopic
laser in situ keratomileusis) as viewed with a confocal microscope. Optom Vis Sci 2003; 80: 690-697.

3. Darwish T, Brahma A, O’Donnell C, Efron N. Sub-basal nerve fiber regeneration after LASIK and LASEK assessed by noncontact esthesiometry and in vivo confocal microscopy: Prospective study. J Cataract Refract Surg 2007; 33: 1515-1521.

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