Case 9:
This month’s Eyes of the Month is about a young woman who experienced a recent onset of blurred vision which eventually led to a diagnosis of bilateral retinitis pigmentosa.
Patient Visit:
A 36-year-old female was referred to Queensland Eye and Retina Specialists following a visit to her optometrist, during which she complained of recent onset blurred vision. She had been noticing more difficulty with her computer work and also generally very tired and heavy eyes. Upon further questioning she had experienced an episode of very bright vision, accompanied by a pressure sensation behind the eyes.
Her past ocular history was unremarkable for her age. She had mild myopic astigmatism since her teens. There was no previous head trauma. Family history included myopia. She had no significant past medical history. She lives locally and does not currently drive but does have a driver’s license.
Ocular exam revealed the following:
Best Corrected Visual Acuity:
RE: 6/12 LE: 6/15++
Best Corrected Visual Acuity:
RE: Plano/-1.50 x 75 (6/9=) PHNI LE: -0.25/-1.50 x 95 (6/9=) PHNI
Intraocular Pressure (iCare):
RE: 20mmHg LE: 20mmHg
Pupils: EA, DCN No RAPD
External examination with slit lamp was within normal limits. There were no abnormalities or media opacities in the cornea, anterior chamber, or lens.
Figure 1: Optos Widefield imaging of the left fundus. Patchy hypopigmentation of the mid-peripheral fundus and pigment clumping can be seen. There is also attenuation of the retinal arteries.
Dilated fundus examination revealed widespread areas of patchy hypopigmentation, sparing the fovea (Fig 1). Also of note, a number of small areas of pigment clumping could be seen in the mid-peripheral retina. There was evidence of attenuation of the retinal arteries. The vitreous and optic nerves appeared healthy. There was considerable symmetry in the appearance of the left and right fundus.
Due to the appearance of both fundi, the decision was made to take fundus autofluorescence (Fig2) images and also undergo visual field testing (Fig3).
Figure 2: Fundus autofluorescence imaging of the left fundus, highlighting more subtle hyperfluorescent changes in the parafoveal area. The extent of the hypopigmentation is also more evident with this imaging modality.
The image above is a fundus autofluorescence photo taken using the Optos machine. It allows much easier visualisation of the extent of the hypopigmentary changes seen in the mid-peripheral fundus. Further, it highlights more subtle hyperfluorescent changes around the macula, which were not evident on the colour images.
The patient had never undergone visual field testing in the past. It was decided to do a 30-2 visual field to assess the patient’s peripheral vision and thus suitability to drive. The visual field below demonstrates significant constriction of the peripheral visual field in the left eye, which was mirrored in the visual field of the right eye. Both the mean and the pattern standard deviation demonstrate significant reduction when compared to the normative database.
Figure 3: Visual Field testing for the left eye, illustrating significant constriction of the peripheral visual field. The central visual field is spared.
Discussion:
Retinitis pigmentosa (RP) is the name for a group of inherited retinal disorders. The underlying cause of RP can be quite variable, as it depends on the associated genetic disorder. Ultimately, the pathology for all is similar, and vision loss is caused by defects/loss of the outer segments of the rod and cone receptors. Pigmentary cells can also be found invading the retina, which give rise to the pathognomonic retinal bone spicules.
Other than genetic predisposition, there is no known risk factors for RP. The most commonly affected gene in patients with RP is the RHO gene, which encodes for production of the photosensitive protein of the rods, rhodopsin. There are however, over 100 different gene loci which have been identified in causing RP. These genes are responsible for producing the proteins involved with transduction of light signals, whether it be the phototransduction cascade, the retinoid cycle, or the structure of photoreceptors.
The first symptoms of RP will usually present during adolescence, with patients often becoming aware of difficulty with night vision. This is followed by mid-peripheral visual field loss and finally far-peripheral visual field loss. Eventually those with RP may experience tunnel vision. More than 50% of patients will maintain good central visual acuity (6/12 or better), although some will have loss of central vision due to cystic changes at the macula or posterior subcapsular cataracts.
Treatment:
There is currently no known research-based treatment for isolated forms of RP. Although a myriad of different supplements, medications, and procedures have been trialled, none have produced reliable, consistent improvement in patients’ measured visual field.
For those patients who develop cystic macula changes, there is evidence to suggest treatment with topical carbonic anhydrase inhibitors (such as dorzolamide) and/or intravitreal corticosteroids (such as triamcinolone or Ozurdex) may reduce swelling and improve visual acuity.
It is strongly recommended that anyone newly diagnosed with RP undergo further testing with other health professionals. Genetic testing can provide patients with information regarding the inheritance of their particular form of RP. Low vision consultation should be commenced as early as possible, to provide different visual aids to optimise visual function and plan for potential future visual changes. If there is a known diagnosis or possibility of Usher syndrome, patients should be referred for audiology consultation.
If your patient visits you after experiencing a sudden onset of blurred vision, difficulty with computer work, and feeling very tired with heavy eyes, refer them to Queensland Eye and Retina Specialists for specialised treatment and personalised care.
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