The macula represents a small part of the retina but it is essential for clear vision. Australian researchers shared their findings related to the macula through e-poster presentations during The Royal Australian and New Zealand College of Ophthalmologists (RANZCO) 52nd Annual Scientific Meeting.
Impact of Cuticular Drusen on Vision
Cuticular drusen represent a phenotype of clinical relevance in the spectrum of age-related macular degeneration (AMD) and may confer a higher risk of progression to vision-threatening complications. To determine the prognostic significance and impact on visual function of the cuticular drusen phenotype in intermediate AMD, Dr. Kai Lyn Goh from the Centre for Eye Research Australia and colleagues examined 280 eyes from 140 participants with bilateral large conventional drusen.
The patients underwent color fundus photography (CFP), optical coherence tomography (OCT), fundus autofluorescence and microperimetry testing at baseline, and then once every 6 months for 3 years. These eyes were graded for the presence of cuticular drusen, based on characteristic changes on CFP and OCT – multiple yellow, small, uniform, round deposits on CFPs corresponding to a series of retinal pigment epithelium elevations on OCT.
“There are three important things we noted about patients with cuticular drusen. First, those with the phenotype did not show increased progression to late AMD over 3 years. Second, there is no significant difference in baseline visual sensitivity between those with and without cuticular drusen. And third, those with cuticular drusen did not show a greater rate of visual sensitivity decline prior to the development of late AMD compared to those without this phenotype.
“These findings suggested that those with cuticular drusen have a similar prognostic significance as those with conventional drusen and should be managed accordingly,” she noted, adding that further work is needed to understand the unique disease pathways in the development of cuticular drusen which will likely inform the best treatment strategies for the phenotype.
Nocturnal Hypoxia and AMD
Our eyes have millions of photoreceptors that are highly metabolically active, especially at night, and are vulnerable to AMD. Dr. Wendy Fang from Monash University explored the possible role of nocturnal hypoxia in AMD.
She and colleagues did a study that measured nocturnal oxygen levels in a cohort of 98 AMD cases and 47 age-matched controls using a pulse oximeter over three consecutive nights. Parameters measured included: oxygen desaturation index (ODI), basal peripheral oxygen saturation (SpO2), minimum SpO2, range of SpO2 and percentage of time spent below 90% SpO2.
“We found that AMD was not significantly associated with any of these parameters. Results are inconclusive and the reason could be that our study was underpowered due to sample size. Therefore, increasing the cohort size will be important and we can continue to explore this novel, potentially modifiable risk factor for AMD,” she said.
Macular Cell Loss in Rod-cone Dystrophy
Gene therapy has emerged as a novel treatment strategy for inherited retinal diseases (IRD). However, measurement of treatment efficacy is limited by traditional clinical trial endpoints such as best-corrected visual acuity (BCVA), according to Dr. Joel Mudri from the Royal Perth Hospital, Western Australia.
To investigate this, he and his colleagues did a prospective, observational cohort study to quantify the progression of total macular volume (TMV) in patients with rod-cone dystrophy over a two-year period compared with the traditional endpoint of BCVA. They also aimed to determine the feasibility of using TMV change as endpoint in clinical trials and assess the symmetry in progression rate between eyes.
During the study, the patients underwent baseline ophthalmic examinations including BCVA test and spectral domain (SD)-OCT with the Heidelberg Spectralis HRA+OCT and were followed up every 6 months for a minimum of 2 years.
“We found that in one-third of cases, TMV decline exceeded the retest variability. The feasibility of using TWV as an endpoint for clinical trials is limited by coexisting pathology (e.g. cystoid macular edema, epiretinal membrane, macular hole and gliosis). While the progression of TMV between eyes is highly symmetrical,” he said.
Editor’s Note: The 52nd Annual Scientific Congress of The Royal Australian and New Zealand College of Ophthalmologists (RANZCO Brisbane 2022) was held virtually from February 26 to March 1. Reporting for this story took place during the event.
