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Monday / April 15.
HomemipatientPondering the Imponderable

Pondering the Imponderable

An unanticipated diagnosis of diabetes type 2 set about a cascade of ocular complications leading to a precarious situation.

Ray,* a 60-year-old male, presented for the first time to my practice after COVID-19 lockdowns. He wanted new rigid gas permeable (RGP) contact lenses for his keratoconus as he had recently lost a lens, and was wearing an older lens, which was deposited and scratched. He was struggling with his vision.

PATIENT HISTORY

Ray has a complex ocular history.

Since the age of 15, Ray had been managing high myopia with RGP contact lenses. He had been diagnosed with keratoconus at age 39 and was diagnosed with type 2 diabetes following a routine blood test at 54. Ray’s diagnosis was a surprise to all as he felt and looked healthy. At diagnosis his blood glucose levels were alarmingly high at 28mmol/L, resulting in hospital admission until his blood glucose levels were under control. Ray does have a strong family history of type 2 diabetes with both parents suffering from the disease.

Ray developed cataracts in both eyes soon after his diabetes type 2 diagnosis. Right cataract surgery was performed first, with the view of performing the left soon after. Unfortunately he developed diabetic macular oedema (DMO), which was treated with anti-VEGF injections.

A plan to refit Ray with a new RGP lens for his right eye was disrupted by COVID-19 lockdowns, so he had continued with an RGP contact lens in his left eye only.

During that time, he allowed his health to lapse; living a sedentary life, trading exercise for the couch, and healthy eating for junk. As a consequence, his blood sugar levels elevated. However, once lockdowns were lifted, he resumed exercise and improved his diet, and his blood sugar levels returned to 6mmol/L.

Ray was prompted to seek optometric care after he lost his left contact lens, and had to rely on an older lens. He assumed his reduced vision was due to the age of the older lens.

ASSESSMENT

When Ray presented in my practice, his unaided right eye vision was count fingers. The left RGP contact lens, which was deposited and scratched, enabled 6/38 vision. A contact lens fitting revealed no improvement in contact lens acuities.

Anterior examination revealed a clear right intraocular lens, and moderate posterior subcapscular changes in the left ocular lens. There was moderate corneal thinning and ectasia in the both eyes R>L. There was also mild apical corneal scarring in the right eye.

A mydriatic fundus examination revealed right disc pallor, and a healthy optic nerve in the left eye. There were a few flame haemorrhages noted in the right eye (Figure 1), and milder diabetic retinopathy (DR) in the left. Optical coherence tomography (OCT) revealed bilateral macula oedema R>L (Figures 2).

TREATMENT

Ray was referred to a retinal specialist. He had multiple anti-VEGF injections (Eylea) in both eyes, which improved the macula oedema, however the right eye did not resolve, even on monthly dosing. His treatment was escalated to right intravitreal steroid injections (triamcinolone) and later, Ozurdex intravitreal implants every two to three months. This significantly improved the oedema, however it did not result in complete resolution. Over time, the left eye recovered to 6/12 contact lens acuity; but the macula oedema stopped responding to Eylea; fortunately it responded well to Vabysmo when switched. During this process, which spanned 20 months, his left cataract significantly worsened.

He returned to my practice to be refitted with contact lenses. The plan was that if the right eye could be improved to a reasonable level, left cataract surgery would be performed. However, if a new contact lens could improve his vision in the left eye to driving vision, cataract surgery would be delayed.

With his new lenses, Ray’s contact lens acuities were R 6/75, L 6/18. OCT revealed pervading macula oedema in the right eye and no oedema in the left (Figure 3).

The severity of Ray’s cataract had already reached a point where it hindered his ability to drive. However, his corneal surgeon was hesitant to proceed with cataract surgery until his vision loss was such that he could no longer work and function.

Given the long duration of the DMO in the right eye with minimal recovery in vision, the prognosis was poor. The left eye was essentially Ray’s ‘only’ eye and his corneal surgeon and Ray did not wish to risk worsening his DR while he was still functioning. The strategy was to monitor for now.

DISCUSSION

Diabetic retinopathy is the leading cause of legal blindness in working-aged people in developed countries,1 with DMO the most common cause of vision loss in DR.2

The International Diabetes Federation (IDF) estimated the worldwide population of diabetes to be 463 million in 2019, and projected an increase to 700 million by 2045. In those living with diabetes, the risk for DR is between one in five and one in three, with vision-loss occurring in 6.2%, and clinically significant macular oedema in 4.1%.3,4

The presence of cataracts occurs more commonly and at an earlier age in people living with diabetes. While cataract surgery is typically uncomplicated with excellent visual outcomes, cataract surgery for people with diabetes can induce or exacerbate DMO post-operatively. Only half of patients with existing DR achieve post-surgical visual acuities of ≥6/12 compared with >95% in those without DR.5

Ray’s retinal surgeon proposed prophylactic intravitreal Vasbysmo in combination with triamcinolone at the time of surgery to prevent further DMO. The DIMECat trial found that the use of intravitreal triamcinolone during cataract surgery can lead to improved visual acuities post-surgery, with 74% of patients not requiring any additional treatment at six months. At 12 months, this number reduced to 62%.5

Ray’s situation is certainly very precarious. He is still of working age and runs a business with no plan to retire in the immediate future. The cataract will not improve and there will come a time, probably in the not too distant future, when he needs to proceed with surgery. However this comes with huge risk of non-reversible loss of vision, potentially rendering him blind.

This is an unfortunate situation where hindsight is a b****. The best cure would have been prevention – i.e., tight glycaemic control throughout Ray’s life. Unfortunately, diabetes is a complex condition where regaining glycaemic control does not immediately result in cessation of disease, in fact it has been widely shown that rapid improvement in blood glucose levels can lead to worsening of diabetic retinopathy,6 as was the case for Ray. As optometrists, our (hopefully) annual diabetic reviews may feel repetitive and mundane, especially when each time their eyes appear completely healthy. Hopefully this case can be a reminder of why we perform these reviews, and the importance of frequently educating our patients about the importance of maintaining constant glycaemic control.

*Patient name changed for anonymity.

Jessica Chi is the director of Eyetech Optometrists, an independent specialty contact lens practice in Melbourne. She is the current Victorian, and a past national president of the Cornea and Contact Lens Society, and an invited speaker at meetings throughout Australia and beyond. She is a clinical supervisor at the University of Melbourne, a member of Optometry Victoria/South Australia State Advisory Committee and a Fellow of the Australian College of Optometry, the British Contact Lens Association, and the International Academy of Orthokeratology and Myopia Control.

References

  1. Mohamed, Q., Gillies, M.C., and Wong T.Y., Management of diabetic retinopathy: a systematic review. JAMA: the Journal of the American Medical Association, 2007. 298(8): p. 902–16.
  2. Wong, T., and Klein K., The epidemiology of eye diseases in diabetes. The Epidemiology of Diabetes Mellitus (2nd ed), Ekoé, J., et al., Editors. 2008, John Wiley and Sons: Oxford. p. 475–497.
  3. Saeedi P., Petersohn I., et al., Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes Federation Diabetes Atlas, 9th ed, Diabetes Res Clin Prac. 2019:157:107843.
  4. American Diabetes Association. Microvascular complications and foot care: standards of medical care in diabetes – 2018. Diabetes Care. 2018;31:S105-S118.
  5. Lim L.L., Constantinou M., et al., The DiMECat Trial: A prospective, randomised clinical trial of intravitreous bevacizumab vs. triamcinolone in patients with diabetic macular oedema at the time of cataract surgery – 12-month results. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3862.
  6. Bain, S.C., Klufas, M.A., Ho, A., Matthews, D.R., Worsening of diabetic retinopathy with rapid improvement in systemic glucose control: A review. Diabetes Obes Metab. 2019 Mar;21(3):454–466.