Focusing on anterior therapeutics

The theme of the second Ocular Therapeutics Evening (OTE) was anterior segment. Dr Sue Ormonde, the first of four guest speakers, opened by discussing the management of different forms of infective keratitis, emphasising that we should not use topical steroids until we know what we are treating. She recommended the use of conjunctival swabs before treating keratitis with a broad-spectrum antibiotic, explaining that although a conjunctival swab is not as sensitive as a corneal scrape, it’s less invasive, easy to perform and relatively inexpensive. It also helps avoid antibiotic resistance developing, which is already an issue for some countries, though New Zealand is faring well in this regard.

Changing trends in corneal transplants

Professor Charles McGhee discussed the transitions in corneal transplantation in New Zealand over the last two decades. The most significant change was the large reduction in the number of corneal transplants for keratoconus, the primary indication for transplantation in the last 30 years, largely due to the increased use of corneal collagen crosslinking. As a result, in 2019, re-graft became the most common indication for corneal transplantation. The second trend observed was that penetrating keratoplasty (PK) and lamellar techniques are almost equally employed – similar to trends in the United States, South Korea, Canada and Germany – but PK remained the most common technique in New Zealand, likely due to the high prevalence of keratoconus. In addition, transplantation due to bullous keratopathy has decreased, as cataract surgeries with improved phacoemulsification technology have become more common.

Steroid-induced IOP

Dr David Pendergrast covered the pathophysiology of mast-cell-mediated perennial and seasonal allergic conjunctivitis, as well as the more severe, difficult to manage, T-cell-mediated vernal and atopic keratoconjunctivitis. He reinforced prescribing topical steroids with care, due to the risk of patients developing elevated intraocular pressure (IOP), lens opacity, infection, corneal melt and perforation, as well as delayed epithelial healing. Patients who are very young or those with glaucoma, myopia or diabetes have the highest risk of developing steroid-induced IOP elevation. If patients require long-term steroid treatment or develop steroid-induced complications, Dr Pendergrast advised considering topical cyclosporine or tacrolimus. However, these are not commercially available in New Zealand, so require special authority and manufacture at a formulating pharmacy.

Focusing on anterior therapeutics-ote-anterior-1-2.jpg — Tim Chang and A/Prof Rob Jacobs

Acidic povidone-iodine

Associate Professor Ilva Rupenthal, OTE organiser and director of the Buchanan Ocular Therapeutics Unit, covered the differing mechanisms of antibiotics. Interestingly when povidone-iodine, used off-label for treating adenoviral conjunctivitis, is diluted with saline it has a pH of 4, which is sufficiently acidic to exacerbate ocular irritation. An ex vivo study showed that diluting povidone-iodine with phosphate buffer maintains a pH of 7, providing reduced corneal irritation and increased tolerability without affecting stability or efficacy.

Detailed history

The second OTE was rounded off by Dr Mo Ziaei’s case studies. An unusual case portrayed a patient who suffered blurry vision due to corneal oedema but the cause of oedema was not known. Upon taking a very detailed history, the patient finally recalled rubbing her eyes after gardening and it was revealed that she’d been in contact with milkweed, a plant that belongs to the Asclepiadaceae family known to contain cardiac glycosides in stems and leaves for protection against predators. Thus the corneal oedema was likely due to temporary inhibition of the Na⁺/K⁺-ATPase pump of endothelial cells by cardiac glycosides.

Dr Ziaei provided three tips when faced with unusual cases: 1) Take a very detailed history, asking the patient about contact lenses, foreign bodies, over-the-counter drugs and family history; 2) Examine the good eye for signs of corneal dystrophy; 3) Consider further investigations, such as blood tests, swabs, confocal microscopy, optical coherence tomography (OCT) and topography.

The next two OTEs cover paediatrics (26 October) and dry eye disease (23 November). You can register for either by visting: https://uoaevents.eventsair.com/ocular-therapeutics-evening-series-2021/registration/Site/Register

Charisse Kuo is a therapeutically qualified optometrist in the second year of her PhD at the University of Auckland. Her research involves the development of tissue culture models using human donor retinas and choroids to explore the mechanisms behind sight-threatening diseases.