Decreased reading vision in one eye

Issue: December 2012

ByMark Gifford, OD

A 47-year-old Caucasian male presented for a routine eye examination with an initial complaint of severely decreased reading vision in his right eye. He stated that the symptoms seemed to present gradually over a 6-month period, but he had noticed a more rapid change within the previous month. He did not report using readers or distance correction, and he could not recall when he last had an eye exam, although he did say it was likely more than 10 years ago. His ocular history was entirely unremarkable, and he reported no significant medical history or current medications.

The patient’s entering visual acuity was 20/200 OD and 20/30 OS with no improvement on pinhole testing in the right eye and improvement to 20/25 with pinhole in the left eye. Corrected visual acuity with +0.50 D sph OD remained 20/200, while corrected visual acuity in the left eye improved to 20/20 with -0.75 D sph.

Pupillary function was normal with no afferent defect. Extraocular motility was full as well. Despite his decreased central vision without pinhole improvement in the right eye, Humphrey Matrix (Carl Zeiss Meditec, Dublin, Calif.) screening N-30 FDT testing was normal in each eye. Amsler testing was abnormal in the right eye with severe metamorphopsia encompassing most of the grid.

The patient’s blood pressure was measured at 138/92 mm Hg. Anterior segment biomicroscopic evaluation was also unremarkable with clear media and normal anterior structures. There were no cells or flare in the anterior chamber, and noncontact tonometry measured 14 mm Hg OD and 11 mm Hg OS.

Stereo pair of the macula in the right eye showing marked cystoid edema.

Images: Gifford M

Dilated examination of the right eye showed clear vitreous and a healthy, perfused optic nerve head with 0.3 cup-to-disc ratio. The posterior pole showed extensive exudation and severe macular edema. A closer look after obtaining retinal photographs revealed aneurysmal vessel dilations within the temporal aspect of the macula. The peripheral retina was flat and intact. Dilation of the left eye showed a normal retina from the posterior pole to the periphery with a healthy optic nerve head and cup-to-disc ratio of 0.3.

Optical coherence tomography testing of the macula of the right eye showed severe cystic edema with disruption of the retinal architecture throughout the macula and a central retinal thickness of nearly 700 microns.

Top figure: The patient presented with decreased vision of unknown duration. Bottom figure: Normal retinal appearance in the left eye.

What’s your diagnosis?

While the major differential that must be considered in childhood Coats’ is retinoblastoma, the differential diagnosis of adult-onset Coats’ disease includes other retinal vascular malformations and various causes of exudative retinopathy.

Such conditions include Leber’s miliary aneurysms, idiopathic juxtafoveal telangiectasia, capillary hemangioma, cavernous hemangioma, macroaneurysm and toxocariasis.

I initially tentatively diagnosed severe macular edema suspected to be secondary to the observed aneurysms in the macula. After sharing the case with colleagues, it was decided that the retinal images and the description were consistent with Coats’ disease. Consultation with a retinal specialist confirmed the diagnosis of Coats’. Because the patient did not fit the typical age demographic for Coats’ disease, generally a childhood-onset disease, the diagnosis was off my radar the day of my initial evaluation.

Adult-onset Coats’ disease is a rare presentation of the disorder, but it shares the hallmark signs of classic childhood/adolescent Coats’, which typically presents during the first or second decade of life. Both types show marked abnormal vascular development in the retina (telangiectasis) anterior or posterior to the equator resulting in vessel leakage, lipid exudation and, in severe cases, retinal detachment.

Depending on the degree and location of retinal involvement, symptoms can range from asymptomatic to complete retinal detachment and blindness. Posterior extension of the disease typically carries a more guarded prognosis due to its propensity to leak fluid into the macula. Intraretinal exudation near the macula and cystoid macular edema carry a poor prognosis for significant visual recovery. In addition to vascular leakage, capillary nonperfusion in the affected areas of the retina can also stimulate neovascularization and its subsequent sequelae of vitreous hemorrhage, tractional retinal detachment, neovascular glaucoma and phthisis bulbi. In cases of adult-onset Coats’, the signs are usually less severe and the progression slower.

See the accompanying table for the five clinical stages of Coats’ disease.

Pathogenesis, etiology

The condition occurs unilaterally in approximately 90% of patients and is more common in males by a ratio of 4:1. There are no systemic associations as is more common with some other retinal vascular anomalies such as cavernous hemangioma and capillary hemangioma.

Though the specific etiology of Coats’ disease remains unclear, researchers have suggested that a somatic mutation (as opposed to germ line mutations) in the Norrie disease pseudoglioma (NDP) gene causes the disease.

The NDP gene is responsible for making norrin protein, which plays a role in cell signaling pathways that guide cell and tissue development. Specifically in the retina, various mutations in the NDP gene and its defective norrin product cause improper formation of blood vessels resulting in familial exudative vitreoretinopathy. Other mutations in the gene have been linked to persistent hyperplastic primary vitreous, and still others are associated with a worsening course in retinopathy of prematurity.

Work-up

Fluorescein angiography is helpful in evaluating a patient with suspected adult-onset Coats’ disease because it will highlight the aneurysmal dilations (telangiectasia) of the retinal vasculature. It will also help illustrate the degree of serous exudation and capillary dropout, which can aid in directing laser treatment when necessary.

Optical coherence tomography can also be useful in monitoring patients with known retinal telangiectasis for early leakage into the macula. It is also useful to illustrate the degree of retinal damage secondary to obvious macular involvement, as in the current case.

An SD-OCT scan of the macula illustrates the destruction of the retinal architecture.

Because there is little risk of systemic involvement with a diagnosis of Coats’ disease, no systemic evaluation or genetic testing is required. A general physical may be recommended if the patient’s general systemic health is unknown so that any possible comorbid conditions, such as uncontrolled hypertension, diabetes or blood disorder, can be diagnosed and treated.

Fluorescein angiography will generally differentiate the disorder with certainty, but if the diagnosis is unclear and a differential such as cavernous hemangioma or toxocariasis is suspected, proper referral is warranted. A retinal consultation is warranted at the initial diagnosis and again if any progression is noted. After diagnosis, monitoring patients without visually significant retinal changes every 4 to 6 months is recommended.

Treatment

Traditional treatment has consisted primarily of laser photocoagulation or cryopexy to the leaking vessels in cases of Coats’ disease with macular exudation. But intravitreal steroid injection or implantation and intravitreal bevacizumab injections have been efficacious in more recent cases as well.

When intravitreal treatment is utilized, laser photocoagulation to extramacular telangiectatic vessels is also performed to hasten recovery and may help to prevent recurrence. In severe cases progressing to retinal detachment, various means of repair are implemented followed by laser treatment of telangiectasias to discourage recurrence.

This patient’s management

In this patient’s case, it appears that he had stage 2B Coats’ disease. The retinologist offered the option of laser photocoagulation or laser paired with intravitreal Kenalog (triamcinolone acetate, Bristol-Myers Squibb).

The patient initially chose photocoagulation alone with close follow-up by the retinologist for resolution and possible intravitreal treatment in the future if the edema failed to clear. His visual prognosis is guarded due to the severity of his macular edema at presentation. At the time of this report, I am awaiting a follow-up report from the specialist regarding the patient’s progress. The retinologist also recommended a complete physical to uncover any other possible conditions that could increase the risk of vascular leakage in the future.

For more information:

Black G, et al. Coats’ disease of the retina (unilateral retinal telangiectasis) caused by somatic mutation in the NDP gene: A role for Norrin in retinal angiogenesis. Hum Mol Genet. 1999;8(11):2031-2035.
Goel N, et al. Role of intravitreal bevacizumab in adult onset Coats’ disease. Int Ophthalmol. 2011;31(3):183-190.
Martinez-Castillo S, et al. Adult Coats’ disease successfully managed with the dexamethasone intravitreal implant (Ozurdex) combined with retinal photocoagulation. Case Report Ophthalmology. 2012;3(1):123-127.
Otani T, et al. Over 10 years’ follow-up of Coats’ disease in adulthood. Clin Ophthalmol. 2011;5:1729-1732.
Smithen L, et al. Coats’ disease diagnosed in adulthood. Ophthalmology. 2005;112(6):1072-1078.
Mark Gifford, OD, can be reached at Vision Care Associates, OD, PA; mgiffordod@gmail.com; www.ncvisioncare.com.
Edited by Leo P. Semes, OD, a professor of optometry, University of Alabama at Birmingham, and a PCON Editorial Board member. He may be contacted at (205) 934-6773; lsemes@uab.edu.