Challenges in Low Vision Rehabilitation: A Rare Case of Unilateral Retinitis Pigmentosa and Contralateral Amblyopia

Noah Merhar, O.D., Linda Pham, O.D., Theresa Zerilli-Zavgorodni, O.D., F.A.A.O. West Haven VA Medical Center

Abstract: Patients with rare unilateral somatic Retinitis Pigmentosa (RP) are typically asymptomatic. This case presents with contralateral amblyopia, making management more challenging. Optometric low vision rehabilitation and treatment are discussed for this atypical presentation.

I. Case History: a. Demographics: 65 year old black male b. Chief complaint: unable to see grandchildren play sports c. Ocular history: i. RP OD: diagnosed 2002 ii. Refractive Amblyopia OS iii. POAG OU: Currently taking Azopt TID OU, Combigan BID OU, latanoprost QHS OU. iv. LPI OD, 2009 v. Cataracts OU vi. Compound hyperopic astigmatism, presbyopia OU d. Medical history: i. Hypertension ii. Coronary arterosclerosis iii. Type II DM iv. GERD v. Renal cell cancer s/p cryoablation vi. Environmental allergies e. Medications: i. Atorvastatin 80 mg QD ii. Clopidogrel bisulfate 75 mg QD iii. Folic acid 1 mg QD iv. Lisinopril 10 mg QD v. Cetirizine 10 mg prn vi. Fluticasone 50 mcg 2 sprays QD vii. Pantoprazole 40 mg QD viii. Brimonidine 0.2%/timolol 0.5% 1 gtt BID OU ix. Brinzolamide 1% 1 gtt BID OU x. Latanoprost 0.005% 1 gtt QHS OU II. Pertinent findings: a. VA 20/40-3 OD with eccentric view, 20/200-1 OS in primary gaze b. Humphrey Visual Field: 10-2 OD: 12 degrees remaining centrally, 24-2 OS: full c. Grade 3 APD OD d. SLE: Lens: OD: 2+ anterior polar, 1+ ACC, 3 NS, tr PSC. OS: 2 ACC, 2 NS, 1+ PCC e. DFE: i. OD: retinal pigment epithelium (RPE) spicules and choriocapillaris atrophy 360 degrees. Optic nerve head pallor and attenuated vessels, pigmented lattice with atrophic holes, stable. ii. OS: pigmented lattice and atrophic holes, stable f. Optical Coherence Tomography (OCT): OD: RPE and photoreceptor loss outside macula, cystic edema temporal to fovea, normal foveal contour. OS: normal foveal contour including intact RPE and photoreceptors OS, vitreomacular adhesion without traction. g. Fundus photos were taken h. Contrast Sensitivity: mildly reduced contrast OD, normal sensitivity OS III. Differential Diagnosis: a. Primary: somatic unilateral RP OD vs. asymmetric x-linked RP, amblyopia OS b. Other: i. Diffuse Unilateral Subacute Neuroretinitis (DUSN) ii. Cancer-Associated Retinopathy (CAR) iii. Gyrate Atrophy iv. phenothiazine toxicity v. syphilis vi. congenital rubella vii. ocular trauma IV. Diagnosis and discussion a. This patient presented to our clinic with a prior diagnosis of unilateral RP since 2002. The patient’s presentation has been stable since his initial work up. b. Unilateral RP is a rare presentation of an uncommon condition. While the prevalence of RP is thought to be about 1:3,500-4,000, unilateral RP accounts for only 0.02-5% of all reported cases. Only 2 case reports were about unilateral RP and contralateral amblyopia. Neither of these case reports addressed the functional needs of the patient. c. The patient did not exhibit the binocular vision issues that many small fielded patients have due to the lack of peripheral fusion cues. d. The patient reported no mobility issues, but he did report that sometimes he would suppress OS and have temporary difficulty due to his limited VF OD. V. Treatment and management: a. The patient was prescribed a +3.00 add for reading. He was not prescribed occlusion because even though he had poorer vision OS, it provided a larger field which helped him keep his place while reading. b. The patient also appreciated a plum tint in his reading and constant wear glasses and he preferred a dark amber tint for his sunwear. c. He was prescribed hand held magnifiers for spotting tasks. He benefited especially from illuminated magnifiers, as he had reduced contrast sensitivity OD. d. For intermediate tasks, he preferred a magnifier lamp over an optivisor as the field of view felt more natural. e. He was also prescribed a reading lamp to assist with his contrast sensitivity while reading poor contrast material such as the newspaper. f. For watching sporting events, he was prescribed a focusable spectacle mounted binocular telescope. Initially, it was going to be monocularly prescribed, but the loss of either field of view OS or acuity OD was detrimental. g. He continues to be followed by a retina specialist, a glaucoma specialist and low vision specialists. VI. Conclusion: The combination of unilateral RP with contralateral amblyopia presents a low vision rehabilitation challenge. While often patients with highly asymmetric acuities do better with occlusion for reading, this patient benefitted from the larger visual field in his amblyopic eye and thus his reading fluency improved with binocular reading. Similarly, the patient benefited from a low powered binocular telescope with a large field of view for distance spotting tasks. As he had mildly reduced contrast sensitivity in his dominant eye, he benefited from increased lighting and magnification to enhance the contrast. He also appreciated having his glasses tinted to help with his contrast sensitivity and photosensitivity. Finally, while he generally did not have mobility challenges except during times of suppression, he was referred for orientation and mobility training with a blind rehab specialist. In this case, the patient benefited from low vision aids despite having near normal acuity in one eye and a normal visual field in the other eye. It is the role of primary care optometrists and low vision specialists to determine the functional needs of these patients and consider low vision rehabilitation.

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