Genetic Disorders that Cause Vision Loss: When You Think Nothing More Can Be Done, THINK AGAIN!
Laura K. Windsor, OD, FAAO with Richard J. Shuldiner, OD, FAAO, FIALVS, Chief Clinical Editor
When you think nothing more can be done, tell the patient to Google “low vision help”.
New medical treatments and low vision rehabilitation are improving the quality of life for the visually impaired.
Low vision care has greatly evolved over the past century. Currently, there are over 25 million people in the United States with bilateral retinal diseases and this number is estimated to double by 2050. Low vision care began by treating veterans with ocular injuries following World War I and II. It then turned to treating children with retinopathy of prematurity (ROP) in the 1960s and 70s. Then in the 1980s to present day, low vision rehabilitation has progressed into helping those with acquired conditions like macular degeneration, glaucoma and diabetic retinopathy and caring for the thousands of patients with inherited retinal diseases (IRDs).
Technology and medicine have changed the landscape of low vision care over the years. ROP is rare now due to the better regulation of oxygen in premature babies in the NICU. The use of anti-VEGF drugs to treat exudative macular degeneration patients has allowed these patients to maintain more of their vision and keep them in a range where low vision services are beneficial. Also, the better management of diabetic retinopathy by injections, earlier laser treatment and better blood sugar control is helping diabetic patients keep more of their vision. Now, we are seeing major medical advancements in treating the inherited eye conditions by gene therapies.
THE FIRST GENE THERAPY
The first gene therapy drug released was Luxturna by Spark Therapeutics in 2018. This drug treats those patients with a RPE65 genetic mutation. The mutation of this gene is the cause of approximately 8% of all Leber’s Congenital Amaurosis (LCA) cases and 2% of all retinitis pigmentosa (RP). This adeno-associated virus vector-based gene therapy is halting the loss of vision and giving patients back some visual acuity, improving their visual field and night vision and even helping with their color vision. This one-time treatment has held vision in the trial subjects for over 10 years.
Other gene therapies in FDA trials are for patients with achromatopsia, Stargardt’s macular dystrophy, wet macular degeneration, retinitis pigmentosa, choroideremia, and Usher’s syndrome. Hopefully these treatments are going to allow these patients to keep more of their vision and improve their quality of life as well.
ACHROMATOPSIA AND LOW VISION REHABLITATION
For achromatopsia patients, they suffer from debilitating hemeralopia (day blindness), reduced visual acuities and colorblindness. They are the most light sensitive patients one will ever examine. Currently, help may be on the way as there are FDA gene therapy studies for two (CNGA3 and CNGB3) of the six known genes which cause achromatopsia being done by Applied Genetics Technology Corp in the US and MeiraGTx in the UK.
For example, M.E. is a 42-year-old female who presented for a low vision examination in March 2015 by referral. She stated that she had vision loss since birth which included extreme light sensitivity, color vision issues, nystagmus, headaches and blurred vision. She said she had had multiple diagnoses over the years including ocular albinism and optic nerve damage. Her goals were to be able to drive and get back to work as she had just moved into Indiana. She had never been a driver due to her eyesight.
Her entering visual acuities were OD 20/300 and OS 20/300. Best corrected acuities were OD 20/250 and 20/300 with only a small myopic and astigmatic prescription found in the right eye. The left eye was plano. Upon retinal examination and OCT evaluation, it was concluded that M.E. had achromatopsia and not albinism or optic atrophy.
Our low vision recommendations included fitting her into custom colored contact lenses for achromatopsia, a handheld video magnifier for close work, high powered reading glasses, a 5X pocket magnifier for small tasks and recommending she get a 24-inch monitor for computer work. Upon the fitting of the colored contact lenses, her visual acuity improved to OD 20/150 and OS 20/200 by decreasing her hemeralopia. Her reading with the reading glasses and contact lenses also improved to 20/40.
With the improvement in her visual acuities, she then became eligible for bioptic driving in Indiana. She was then fit with a 4X Ocutech Sport with additional slip-in sun filters and a filtered lens cap for the telescope. She was trained in our office on use of the bioptic, spotting with the telescope and sign identification. She then underwent 30 hours of behind-the-wheel drivers training with a certified driver’s rehabilitation specialist. She became a licensed bioptic driver with both day and nighttime privileges in June of 2016. She continues to drive without any tickets or accidents to this day and works for a large national non-profit organization.
LOW VISION REHABLITATION
Low vision rehabilitation continues to change as technology and medicine to treat patients with eye disorders are developed. These advancements have made low vision services even more beneficial to these patients as they are being left with better vision than in previous decades. Referring patients for low vision care can change their lives by providing the care and tools needed to read, watch television, go to school, be able to work, and drive in some cases. Low vision rehabilitation is crucial in helping those with vision loss have an overall higher quality of life.