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Issue 3: Retinitis Pigmentosa April 2010
Welcome
Welcome to the third issue of IMAGE. This issue discusses Retinitis Pigmentosa and features the Optomap, which can digitally map elusive peripheral areas of the retina without the need for dilation. It is worth noting that CFEH currently has the only Optomap in the Southern Hemisphere. Please refer to the accompanying Instrument Profile for more information.
Save the date! On Sunday the 20th of June, the inaugural CFEH-SCOPE(Series of Continuing Ophthalmic Professional Education) will be held at the Centre. This complimentary event, for optometrists registered with CFEH, will consist of lectures and workshops by prominent ophthalmologists and optometrists. An invitation will be mailed shortly and at least nine CPD points will be available.
Centre Update
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I am very pleased to see optometrists embracing CFEH, with more than 35 per cent of optometrists in NSW and the ACT now registered to refer patients to the Centre. The rate of registrations has exceeded our expectations, which reinforces to me that there is unmet demand for advanced eye imaging and visual assessment services, particularly those provided at no charge to the patient. I would like to thank Optometrists Association Australia (NSW/ACT) for its valuable support in promoting the Centre and encouraging the profession to get behind this important initiative. |
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To date, we have also received over 450 patient referrals. While this is a great achievement, some optometrists registered with us are yet to refer a patient. We will be contacting these optometrists over the coming month to discuss how they can make use of the Centre and the types of patients to refer. Remember, we are here to assist you. If you have any suggestions or questions, please let us know. Prof. Michael Kalloniatis |
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CASE REPORT |
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Claude is having trouble seeing in low light |
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 Figure 1: Attenuated arterioles (A) and retinal pigment clumping (P), as seen on direct othalmoscopy. |
At his first eye examination three years ago, Claude, aged 50, said he had trouble reading small print at night. He was prescribed reading glasses and told to return if he noticed his vision worsening. In February 2010, Claude’s current optometrist referred him to CFEH after noticing attenuated arterioles and some mild pigment clumping on direct ophthalmoscopy (Figure 1). Claude reported that the vision on his left side felt cloudy, and that he had recently experienced difficulty navigating in low light. He had also noticed occasional flashing lights in his vision. |
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Claude has no history of ocular injury or surgery, is in excellent general health, and is not taking any medications. There is no known history of eye disease in Claude’s family. |
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Issues to consider1. What conditions can cause attenuated arterioles and retinal pigment clumping? 2. Are Claude’s difficulties in low light levels significant? 3. What services would you request to aid in diagnosis and managing Claude’s condition? |
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Results and Discussion |
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Differential diagnoses for the ophthalmoscopic fundus appearance described on page 1 include rubella retinopathy, syphilitic retinopathy, retinal drug toxicity, and melanoma-associated retinopathy. An assessment of retinal function including Optical Coherence Tomography (OCT), visual fields and photography would provide useful information. Unaided visual acuities were R:6/4.5-2 and L: 6/9, which improved to 6/6 with pinhole. There was mildly reduced contrast sensitivity and a subtle relative afferent pupil defect in the left eye. Confrontation visual fields were significantly constricted. Humphrey full-field 135-point screening test showed extensive reduction in the visual field, which was worse in the left eye and consistent with Claude’s complaints of cloudy vision on his left side. Colour vision assessment using L’Anthony’s Desaturated D15 showed no errors in the right eye and a single major crossing error in the left eye (pass). Mild posterior subcapsular opacities were observed in each eye. Dilated fundus examination revealed widespread pigmentation (bone-spicule appearance) and paravascular pigment clumping throughout the midperipheral retina in each eye (Figure 2). There was moderate arteriolar attenuation and increased visibility of the choroidal vasculature. Optic discs appeared healthy; however, there were hyperreflective changes visible in the nasal maculae and there was a choroidal naevus temporal to the right macula (Figure 3).
OCT revealed thinning and loss of the photoreceptor layer outside the central macula (Figure 4). In the fovea, the photoreceptor layer appeared intact, which is consistent with Claude’s good central visual acuity. OCT images also revealed an epiretinal membrane in the nasal macula of each eye and associated wrinkling of the inner retinal surface, corresponding to the areas of hyperreflectivity in the fundus photos (Figure 4).
Based on the combination of retinal pigmentary changes, visual field loss, night-vision problems, and loss of the photoreceptor layer on OCT, Claude appears to have changes consistent with Retinitis Pigmentosa. He is scheduled to return to CFEH for electrodiagnostic testing in the near future, and a final report will be sent to his referring optometrist. CFEH is able to provide baseline information to aid in future monitoring of such conditions. Prepared by: Paula Katalinic, CFEH Principal Optometrist |
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Eye Condition Spotlight: Retinitis Pigmentosa
Retinitis Pigmentosa (RP) is a heterogeneous group of inherited retinal dystrophies that result in progressive degeneration of the photoreceptors and subsequent degeneration of the retinal pigment epithelium (RPE)(1).
RP is characterised by an insidious, progressive loss of the visual field and difficulties with night vision (nyctalopia). The pattern of visual field loss usually begins as small midperipheral scotomas, then progresses to confluent ring scotomata with advancing constriction both inwards towards central fixation and outwards towards the periphery. (2,3).
While clinical presentation varies, common ocular findings include bonespicules, paravascular RPE hypertrophy, waxy optic nerve pallor, retinal arteriolar attenuation, and posterior subcapsular cataracts (3).
In the early stages of the disease, an initial reduction in scotopic electroretinography (ERG) measurements in response to abnormal rod function can precede clinically-detectable retinal changes and symptoms of night blindness and visual field loss(2,3). Other early signs may include pigmentary mottling of the RPE and increased visibility of the choroidal vasculature (3). Cystoid macular oedema (CME), epiretinal membrane (ERM), vitreous pigment cells and asteroid hyalosis may also be observed (3).
Loss of central vision usually occurs by age 60. However, many people with RP are legally blind by age 40 due to severe visual field constriction (2).
Difficulties with dark adaptation, photophobia and visual photopsias are common symptoms, and a tritan colour-vision defect often develops once central visual acuity drops to 6/12 or worse (3).
RP has a worldwide prevalence of 1:3000 to 1:5000. It typically presents between adolescence and early adulthood1. The condition is caused by molecular defects in more than 45 different genes (2). Inheritance is autosomal dominant in 15 to 25 per cent of RP cases, autosomal recessive in 15 to 30 per cent, X-linked in six to 10 per cent, and in more than 40 per cent of RP cases, no relatives with RP can be identified (3,4).
RP can be classified into primary cases (confined to the eye) and syndromic cases (associated with abnormalities in other organ systems) (3). Syndromic forms represent 20 to 30 per cent of RP cases, and include Usher’s syndrome, Bardet-Biedl (Laurence-Moon) syndrome, Refsum’s disease and Bassen-Kornzweig syndrome (2).
OCT, ERG, kinetic visual fields and Optomap ultra-widefield imaging are all useful tools in diagnosing and monitoring RP, as well as in detecting associated conditions that can affect a patient’s vision.
ERG, which measures the retina’s electrical response to flashes of light, is used to differentiate RP from other conditions, to assess the severity of the disease, and as a tool in monitoring progression (2). OCT, meanwhile, is invaluable in assessing the macula for CME or ERM. A recent Japanese study of RP patients using OCT found CME in 5.5 per cent of eyes, ERM in 0.6 per cent, and vitreomacular traction in 0.8 per cent (5).
Vitamin A has been shown to slow the decline of cone ERG amplitudes and visual-field loss over time (6). Gene therapy in Leber’s congenital amaurosis has provided an additional treatment option for one form of inherited retinal dystrophy (2,7).
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STAFF PROFILE |
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 Paula Katalinic Principal Optometrist Paula Katalinic joined CFEH as a Principal Optometrist in September 2009. Her interest in the early diagnosis of ocular disease developed during her three-and-a- half years at Boston’s Joslin Diabetes Center. Since returning to Australia, Paula has held a variety of roles, including Staff Optometrist at the UNSW Optometry Clinic. She is currently Projects Officer for OAA NSW. Paula has also participated in three volunteer trips to the Pacific islands of Nauru and Vanuatu, funded by the World Diabetes Foundation and ICEE. "I’m excited by the opportunities that CFEH presents to optometrists and their patients," Paula says. "Access to state-of-the-art imaging technology and diagnostic services at no cost will assist in eliminating the financial barriers to receiving timely, high-quality eye care." |
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