Professor Omar Mahroo on inherited retinal disease

Professor Omar Mahroo highlighted the valuable role that optometrists can play in supporting patients with inherited retinal disease during his keynote presentation at the British Congress of Optometry and Vision Science conference (14-15 September, Cardiff University).

The consultant ophthalmologist and professor of retinal neuroscience at University College London highlighted that optometrists can play a key role in identifying patients who may have an inherited eye disease.

“Optometrists may not be directly managing these patients, but recognising them, referring them on and giving them an idea of what is happening in the retinal genetics clinics can be useful,” Mahroo shared.

While an ophthalmologist may provide a diagnosis, optometrists can improve a patient’s quality of life through providing visual aids and signposting them to other support – for example, through the sight loss certification pathway.

“Often optometrists can do more for a patient than an ophthalmologist can,” Mahroo reflected.

He highlighted that accessing the right support can make a big difference to a child’s future.

“Educational support can make a huge difference to that child's trajectory through life,” Mahroo said.

The ophthalmologist noted that inherited retinal disease is the largest cause of working age blindness in England.

“People think of these conditions as very esoteric and rare. But when you put them together they are a bigger cause of blindness than diabetic retinopathy, for example,” Mahroo highlighted.

Reflecting on factors that may suggest inherited retinal disease, Mahroo shared that family history and a patient’s age should be taken into account.

“If you see something that looks like AMD, but the patient’s 30, then you may think this could be a genetic macular dystrophy rather than age-related macular degeneration,” he observed.

He noted that inherited retinal disease is often bilateral and symmetric.

“Some inflammatory diseases can mimic genetic diseases, but they’re usually not so symmetric,” Mahroo noted.

The professor of retinal neuroscience noted that the order in which the loss of vision presented can give clues about its genetic source.

For example, a child who loses their central vision is more likely to have a form of macular dystrophy than retinitis pigmentosa (RP).

“In RP, the night vision goes first, then the peripheral vision, and then maybe the central vision,” Mahroo observed.

He added that establishing longstanding problems with night vision can be helpful in determining whether a patient has RP.

“Very rarely are you in an environment where you are just using your rods. What question might you ask to elicit that response? In what situations do we go from light to dark? The cinema is the right answer,” Mahroo explained.

Mahroo told delegates that one patient he spoke with had followed the wrong woman to her seat, while another had mistakenly sat in a seat that was occupied.

“They got really angry with her, but she couldn’t tell that the seat was taken,” he said.

People are desperate. Why wouldn’t parents would sell their house if we could get their kid’s vision back?

Emerging treatments

Reflecting on the importance of getting a diagnosis, Mahroo shared that treatments are available for some conditions.

For example, macular oedema can be treated with carbonic anhydrase inhibitors, while cataracts – which are a complication of many inherited retinal diseases – can also be treated.

“Macular neovascularisation can complicate many of the macular dystrophies, and that responds to anti-VEGF injections,” Mahroo shared.

He added that while most novel gene therapies are in the research phase, a treatment for an inherited retinal disease caused by changes in the RPE65 gene is now available on the NHS.

Mahroo observed that sometimes letting patients know that there is nothing currently available for their condition can act as an important service.

He added that this protects patients from spending money on treatments with a lack of evidence.

“People are desperate. Why wouldn’t parents would sell their house if we could get their kid’s vision back?” Mahroo noted.

“Some of these people [advertising treatments] are very unscrupulous,” he said.

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Outlining other categories of treatment that are in the pipeline for inherited retinal disease, Mahroo shared that while gene therapies focus on replacing faulty genes, these require surviving cells.

“Stem cell treatments aim to replace the cells that have died,” he said.

Electronic implants could be used in patients who have lost photoreceptors to electrically stimulate the bipolar cells and ganglion cells, Mahroo shared, while optogenetics focuses on making alternative cells sensitive to light.

A life-saving genetic diagnosis

Mahroo shared an example of a case where a genetic diagnosis had made a profound difference to a patient outcome.

He recalled a colleague coming from eye casualty on a Friday afternoon to show him some unusual eye scans.

Mahroo recognised signs of Danon disease – a rare genetic condition that is associated with cardiomyopathy.

“I found out these scans belonged to a 16-year-old boy who had been admitted with heart failure,” Mahroo shared.

The cardiology team had initially suspected cardiac vasculitis, and planned to conduct a biopsy of the patient’s heart.

However, after rapid genetic testing confirmed Mahroo’s suspicion, the biopsy was no longer necessary. The patient was sent to a hospital that specialises in Danon disease where he received a heart and lung transplant.

“A couple of years ago, when he came to clinic his mum said to me ‘You saved his life’,” Mahroo shared.

“It doesn’t happen often, but you can do some real good by knowing your genetics,” he reflected.