July 2019 marked the evolution and merger of ODMA and the SRC conference into O=Mega, complete with trade fair, clinical lectures, dispensing master classes and all the social stuff. The conference aim was to meet the needs of optometrists at all stages of their career; and that it did. There were new research updates, case discussions, refreshers on more obscure conditions and testing guides for more streamlined but sensitive work-ups.
Here are just some of the highlights of this new, three-day biennial conference.
OCT for glaucoma
It’s amazing, so many optometry practices now have optical coherence tomography (OCT) systems readily available to clinicians, with some even incorporating it as a routine clinical tool performed in pretesting and not only on indication. This has increased our sensitivity for identifying true glaucoma suspects. However, with limited time resources, it is important to know how to effectively pick up a glaucoma suspect without being thrown off by common OCT limitations.
Keynote speaker, Professor Danica Marrelli from Houston University, stressed that OCT scans must not be processed in a vacuum. For one thing, normative databases are quite limited in terms of subject number, ethnic diversity, age range and the magnitude of refractive error, which relates to optic disc size and shape. With this in mind, an ‘abnormal’ flagging does not necessarily mean unhealthy. A prime example of this is ‘red disease’ where a patient’s data falls into the lowest 1% of the reference database (and thus, we see their OCT scan coloured red) but does not actually have glaucoma. Conversely, there’s ‘green disease’, thus OCT is most effective when serial scans are analysed over extended follow up periods.
Careful clinical examination and structure-function correlation is also important to avoid being confused by artefacts. For example, naturally shifted peripapillary vasculature with corresponding shifted distribution of the retina nerve fibre layer (RNFL) can convey wedge shaped RNFL defects falling outside the normative database. Presence of glial cells and peripapillary atrophy can also change thickness measurements. We must be mindful to avoid false positive results and tentative diagnoses of glaucoma, said Prof Marrelli.
Provided the patient has no concurrent macular disease, macular scans are useful but underutilised secondary scans for glaucoma risk assessment. The macula contains 50% of retinal ganglion cells and its avascular nature and less anatomic variation compared to peripapillary tissue allows results to be more reproducible. Intereye and intraeye (superior/inferior) macular thickness asymmetry can be measured and monitored. The inferio-temporal region of the macula is the macular vulnerability zone and at the highest risk of glaucomatous damage, so asymmetry between superior and inferior temporal macula is a useful marker.
Novel dry eye therapies
Associate Professor Jennifer Craig who notably served as vice chair of the Tear Film and Ocular Surface Society (TFOS) second Dry Eye Workshop (DEWS II) discussed intense pulsed light (IPL) and manuka honey as novel therapies for dry eye.
IPL is a light therapy emitted at a 580-1200nm wavelength range originally in aesthetic practices for skin therapy to coagulate telangiectasic vessels in rosacea and treat facial melasma. These skin doctors then recognised the treatment appeared to improve patient’s dry eye symptoms as well and so some began performing IPL for meibomian gland dysfunction, the main cause of dry eye disease (DED). Until recently, IPL had only ever been investigated as a treatment alongside meibomian gland expression, which made it impossible to determine whether IPL just benefitted patients through the immediate effect of heating the sebum inside the glands or if it actually reduced the number of inflammatory mediators reaching meibomian glands by oxyhaemoglobin. These inflammatory mediators, which are a response to bacterial exotoxins, break down lipid stability and change tear film osmolarity.
The Auckland University IPL study was double masked, randomised, and solely tested the effects of IPL therapy. It found IPL did improve patients’ symptoms, reduced MG capping and inflammatory markers and improved lipid layer thickness. There was no significant association between IPL and aqueous tear production or staphylococcal lash crusting and Demodex. Benefits were demonstrated to be cumulative with the greatest improvement after four to five treatments, with five flashes per eye, per treatment speeding up improvement. Ideal candidates are patients with significant dry eye symptoms, poorer baseline meibomian gland scores and greater seborrheic lash crusting.
The natural antibiotic and anti-inflammatory effects of manuka honey (active ingredient methylglyoxal) are well documented. But a new in vitro finding has demonstrated methylglyoxal’s abilities in eliminating Demodex. Complexed manuka in the form of a microemulsion cream applied on skin around eye, has been demonstrated to decrease dry eye symptoms, improve lipid layer grade and tear breakup time, reduce lid wiper epitheliopathy and reduce the Demodex count to the equivalent of using a not-so-pleasant 50% tea tree oil concentrate. All DED clinical signs showed improvement after three months of using the manuka cream.
Novel keratitis therapies
Brisbane-based optometrist David Foresto and Melbourne-based ophthalmologist Dr Georgia Cleary delivered a lively session discussing conflicting views on microbial keratitis (MK) and aminoglycoside/steroid therapy, which really conveyed the subjective nature of empirical therapies. Another notable therapy examined by Foresto was corneal crosslinking for infectious keratitis (PACK-XCL).
Like the traditional technique for keratoconics, the cornea is saturated with riboflavin and photoactivated with UVA. This disrupts base pairings of pathogenic RNA and DNA, inhibiting replication. The reactive oxygen species that initiates the development of crosslinks which equips the stiffer cornea against ulcerative melts (common with infectious keratitis) also destroys the pathogen via oxidative means. This three-fold benefit makes PACK-XCL a great adjunct therapy to mainstay MK topical pharmacologic therapy, particularly for bacterial, fungal and acanthamoeba causes of MK, said Foresto. But, because there is no standardised protocol, it works poorly with deeper ulcers and doesn’t treat herpetic causes. It has also only ever been tested for its effects as a treatment in conjunction with antimicrobials (vs antimicrobials alone), so is only useful as a secondary therapy for MK.
More clinical pearls
There were many clinical pearls shared throughout the conference, so here are a few I feel are noteworthy and could be useful in clinical practice even though they may seem a little left of routine.
- LASIK and pregnancy - Recommend LASIK candidates pursue surgery at least six months following delivery. This is due to pregnancy hormones in about 10% of patients causing corneal swelling which can change corneal thickness and curvature, leading to refractive regression. Pregnancy can also exacerbate symptoms of dryness and halos that are common side effects of LASIK.
- Symptomatic coma - If you have a keratoconic patient with coma (confirmed with wavefront aberrometry or inferred from night glare symptoms), you can prescribe alpha agonist 0.1% alphagan to be administered 30mins to 1hr prior to night activity to shrink pupil in mesopic conditions and reduce symptoms. The lower concentration lowers risk of allergy and alpha agonists don’t have the parasympathomimetic side effects (like brow ache and accommodative spasm) that pilocarpine has.
- Red Eye - Make sure to always check ocular motilities, even with red eye patients. CN III, IV, V, and VI all pass through the cavernous sinus and so a carotid cavernous fistula causing an increased pressure in the cavernous sinus will not only cause chemosis, but potential nerve palsies of the aforementioned cranial nerves (or motility restriction due to enlarged ophthalmic veins).
- Conventional contact lenses can still be used for specialised cases - Alcon Air Optix toric is the highest modulus toric contact lens and so is a great option for masking undercorrected cylindrical refractive error and corneal curvature irregularities in some patients. While tinted contacts can be prescribed to help elite sports players. For example, amber tints enhance contrast and can be useful for ball recognition.
Overall, the O=Mega conference demonstrated great ways to implement clinical care in a commercial practice, from offering streamlined guides for the conditions we routinely screen for (such as glaucoma) to case study reminders of more obscure conditions and patient presentations, and novel therapies for common conditions.
Australian-based Layal Naji is a staff optometrist with the Australian College of Optometry and co-founder of the outreach optometry clinic at the Asylum Seekers Centre in Newtown, Sydney.