Ophthalmic Surgery, Lasers and Imaging Retina

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Case Report 

Loss of Foveal Cone Photoreceptor Outer Segments in Occult Macular Dystrophy

Robert A. Sisk, MD; Audina M. Berrocal, MD; Byron L. Lam, MD

Abstract

To describe a previously unreported finding on optical coherence tomography (OCT) in a patient with occult macular dystrophy (OMD) and correlate it with retinal dysfunction. Retrospective observational case report. A 72-year-old woman presented with sequential progressive central scotomata with reduced visual acuities and color vision in both eyes. Fundoscopic appearance, fundus autofluorescence, fluorescein angiography, and indocyanine green angiography were normal. Full-field ERG was normal, but multifocal ERG demonstrated reduced amplitudes, confirming the diagnosis of OMD. OCT demonstrated loss of cone outer segments with preservation of the inner segment-outer segment junction and photoreceptor cell bodies in both eyes. Loss of cone photoreceptor outer segments may be responsible for decreased visual acuity and foveal thinning in OMD.

Abstract

To describe a previously unreported finding on optical coherence tomography (OCT) in a patient with occult macular dystrophy (OMD) and correlate it with retinal dysfunction. Retrospective observational case report. A 72-year-old woman presented with sequential progressive central scotomata with reduced visual acuities and color vision in both eyes. Fundoscopic appearance, fundus autofluorescence, fluorescein angiography, and indocyanine green angiography were normal. Full-field ERG was normal, but multifocal ERG demonstrated reduced amplitudes, confirming the diagnosis of OMD. OCT demonstrated loss of cone outer segments with preservation of the inner segment-outer segment junction and photoreceptor cell bodies in both eyes. Loss of cone photoreceptor outer segments may be responsible for decreased visual acuity and foveal thinning in OMD.

Loss of Foveal Cone Photoreceptor Outer Segments in Occult Macular Dystrophy

From the Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.

The authors have no financial or proprietary interest in the materials presented herein.

Address correspondence to Robert A. Sisk, MD, Bascom Palmer Eye Institute, 900 NW 17th St., Miami, FL 33136.

Accepted: April 09, 2009
Posted Online: March 09, 2010

Introduction

Occult macular dystrophy (OMD) was originally described by Yozo Miyake in 1989 as a central form of cone dystrophy with decreased visual acuity in the presence of normal fundoscopic appearance and fluorescein angiography testing.1 Full-field electroretinography (ERG) showed normal photopic responses, although focal macular ERG demonstrated a foveal cone photo-receptor defect.2 Multifocal ERG has become the gold standard for diagnosis of OMD.3

Time-domain optical coherence tomography (OCT) was performed in a series of eight OMD patients, revealing a decrease in foveal thickness with increased steepness to the foveal depression.4 We present previously undescribed spectral-domain OCT findings of an atypical patient with OMD.

Case Report

A 72-year-old woman with an unremarkable past ocular history noted sudden onset of a central scotoma in her right eye. Visual acuity was 20/200 right eye (OD) and 20/20 left eye (OS) despite normal pupillary responses, anterior segment and fundoscopic examination, fluorescein angiography (FA), and automated perimetry using a 30–2 pattern in both eyes (Fig. 1). Her past medical history was negative for vascular disease and review of systems was noncontributory. She had no family history of ophthalmic disease. A systemic medical work-up, including neurologic examination and magnetic resonance imaging (MRI) of the brain were normal. She was free of new symptoms for 4 years until she developed multiple pinpoint scotomata in the left eye. Visual acuity OS remained 20/20, and Ishihara color testing showed absent color vision OD with 1/15 plates and a mild dyschromatopsia OS with 11/15 plates. Fundoscopic examination, FA, and indocyanine green angiography (ICG) were normal (Fig. 2). Full-field ERG showed normal photopic and scotopic responses both eyes (OU). Multifocal ERG showed absent responses OD and decreased amplitudes OS (Fig. 3). OCT demonstrated total loss of outer retinal elements OD with reduced foveal thickness (Fig. 4). Over eight months of follow-up, visual acuity in the left eye decreased progressively to 20/200 with severe dyschromatopsia (1/15 plates OU) despite normal fundus appearance, FA, and fundus autofluorescence. Foveal thickness on OCT was initially normal in the left eye but deteriorated over a 4 year period with progressive loss of photoreceptor outer segments. Systemic work-up for occult malignancy and MRI of the brain with gadolinium enhancement were negative. Multifocal ERG now demonstrated absent responses OU, confirming the diagnosis of OMD.

(A and B) Fundus Photograph of Normal-Appearing Maculae of the Right and Left Eyes, Respectively. (C and D) Normal Recirculation Phase Frames from Fluorescein Angiography of the Right and Left Eyes, Respectively.

Figure 1. (A and B) Fundus Photograph of Normal-Appearing Maculae of the Right and Left Eyes, Respectively. (C and D) Normal Recirculation Phase Frames from Fluorescein Angiography of the Right and Left Eyes, Respectively.

(A and B) Normal Fundus Autofluorescence (Heidelberg Spectralis® (Heidelberg Engineering, Heidelberg, Germany) of the Right and Left Eyes, Respectively. (C and D) Normal Indocyanine Green Angiography of the Right and Left Eyes, Respectively.

Figure 2. (A and B) Normal Fundus Autofluorescence (Heidelberg Spectralis® (Heidelberg Engineering, Heidelberg, Germany) of the Right and Left Eyes, Respectively. (C and D) Normal Indocyanine Green Angiography of the Right and Left Eyes, Respectively.

(A) Multifocal ERG Traces Showed Absent Foveal Responses OD. (B) Multifocal ERG Traces OS Showed Reduced Foveal Amplitudes Despite 20/20 Visual Acuity. (C) Over Eight Months of Follow-Up, OD Remained Stable. (D) Visual Acuity OS Fell to 20/200 and Foveal Amplitudes Became Extinguished.

Figure 3. (A) Multifocal ERG Traces Showed Absent Foveal Responses OD. (B) Multifocal ERG Traces OS Showed Reduced Foveal Amplitudes Despite 20/20 Visual Acuity. (C) Over Eight Months of Follow-Up, OD Remained Stable. (D) Visual Acuity OS Fell to 20/200 and Foveal Amplitudes Became Extinguished.

(A–C) Stratus® OCT 3, Cirrus® SD-OCT (Carl Zeiss Meditech, Dublin, CA), and Spectralis® HRA-OCT (Heidelberg Engineering, Heidelberg, Germany) Images OD Taken Two Years Apart Demonstrate Absent Cone Outer Segments with Reduced Foveal Thickness of 166 Microns that Remained Unchanged During Follow-Up. (D) Stratus® Images OS Initially Had Preserved Foveal Thickness (216 Microns) Despite a Discrete Loss of the Outer Photoreceptor Segments, not as Severe as OD, Which Became More Evident with Follow Up. (E and F) Cirrus® and Spectralis® Images, Respectively, Show Increased Loss of Cone Outer Segments 2 Years Later.

Figure 4. (A–C) Stratus® OCT 3, Cirrus® SD-OCT (Carl Zeiss Meditech, Dublin, CA), and Spectralis® HRA-OCT (Heidelberg Engineering, Heidelberg, Germany) Images OD Taken Two Years Apart Demonstrate Absent Cone Outer Segments with Reduced Foveal Thickness of 166 Microns that Remained Unchanged During Follow-Up. (D) Stratus® Images OS Initially Had Preserved Foveal Thickness (216 Microns) Despite a Discrete Loss of the Outer Photoreceptor Segments, not as Severe as OD, Which Became More Evident with Follow Up. (E and F) Cirrus® and Spectralis® Images, Respectively, Show Increased Loss of Cone Outer Segments 2 Years Later.

Discussion

Occult macular dystrophy is a rare heritable cause of bilateral visual loss that typically presents in the fourth or fifth decades. The degree of visual impairment is quite variable, with acuities ranging from 20/20 to 20/400. Other causes of decreased macular function in adults with normal fundoscopic examination include white dot syndromes, autoimmune retinopathy, cancer-associated retinopathy, Stargardt’s disease, and retinitis pigmentosa sine pigmento.5 Demonstration of normal full-field ERGs with severely reduced or absent multifocal ERG responses excludes these diagnoses and is pathognomonic of OMD.

Outer retinal thinning and atrophy from photoreceptor degeneration has been described as a common feature in areas of retina affected by retinal dystrophies.6 On OCT, this is initially observed as shortening of photoreceptor outer segments followed by loss of the inner segment-outer segment junction and eventually loss of photoreceptor cell bodies. As the loss of photoreceptor function overcomes local redundancy and approaches a critical threshold, visual acuity decreases.7 Brockhurst and Sandberg demonstrated that the reduction in foveal thickness in patients with OMD is from loss of the outer nuclear layer.8 In contrast, our patient has relative sparing of the cone photoreceptor cell bodies with loss of outer segments, as evidenced by a preserved inner-outer segment junction anterior to a lamellar cystic defect. Fluorescein and indocyanine green angiography exclude vascular leakage as the source of the subretinal fluid observed on OCT. Fundus autofluorescence confirms a lack of disturbance to the RPE, excluding generalized cone dystrophy, chloroquine maculopathy, solar retinopathy, and Stargardt’s disease.

Loss of cone photoreceptor outer segments was responsible for reduced visual acuity and decreased foveal thickness in our patient with OMD. In contrast to previously described patients, we observed the progression of OCT changes in our patient over a 4 year period. Perhaps our images represent an earlier stage of the disease and she will eventually lose the photoreceptor cell bodies. We anticipate the use of spectral domain OCT technology will provide better understanding to the pathogenesis of this fascinating disease.

References

  1. Miyake Y, Ichikawa K, Shiose Y, Kawase Y. Hereditary macular dystrophy without visible fundus abnormality. Am J Ophthalmol. 1989;108(3):292–299.
  2. Miyake Y, Horiguchi M, Tomita N, et al. Occult macular dystrophy. Am J Ophthalmol. 1996;122(5):644–653.
  3. Piao CH, Kondo M, Tanikawa A, et al. Multifocal electroretinogram in occult macular dystrophy. Invest Ophthalmol Vis Sci. 2000;41: 513–517.
  4. Kondo M, Ito Y, Ueno S, et al. Foveal thickness in occult macular dystrophy. Am J Ophthalmol. 2003;135:725–728. doi:10.1016/S0002-9394(02)02158-X [CrossRef]
  5. Mantel I, Ramchand KV, Holder GE, et al. Macular and retinal dysfunction of unknown origin in adults with normal fundi: evidence for an autoimmune pathophysiology. Exp Mol Pathol. 2008;84:90–101. doi:10.1016/j.yexmp.2007.10.006 [CrossRef]
  6. Witkin AJ, Ko TH, Fujimoto JG, et al. Ultra-high resolution optical coherence tomography assessment of photoreceptors in retinitis pigmentosa and related diseases. Am J Ophthalmol. 2006;142(6):945–52 doi:10.1016/j.ajo.2006.07.024 [CrossRef]
  7. Kim JI, Tan O, Fawzi AA, et al. A pilot study of fourier-domain optical coherence tomography of retinal dystrophy patients. Am J Ophthalmol. 2008;146;417–426. doi:10.1016/j.ajo.2008.05.018 [CrossRef]
  8. Brockhurst RJ, Sandberg MA. Optical coherence tomography findings in occult macular dystrophy. Am J Ophthalmol. 2007;143(3): 516–518. doi:10.1016/j.ajo.2006.10.025 [CrossRef]
Authors

From the Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, Florida.

The authors have no financial or proprietary interest in the materials presented herein.

Address correspondence to Robert A. Sisk, MD, Bascom Palmer Eye Institute, 900 NW 17th St., Miami, FL 33136.

10.3928/15428877-20100215-49

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