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Teenager presents with ‘strabismic amblyopia’
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A 17-year old Caucasian male presented to the clinic with a chief complaint of severely blurred vision involving his right eye since early childhood. He was diagnosed with “strabismic amblyopia” at the age of 6 years, and at that time he was prescribed eyeglasses. There was no improvement to visual acuity in the right eye after occlusion therapy, and symptoms have remained stable since. The remainder of the ocular and medical histories were noncontributory. He was taking no medications and denied drug allergies.
At evaluation, visual acuity was 20/100 OD (not improving with pinhole or refraction) and 20/20 OS. Cover test revealed a concomitant 8 prism diopter right hyperdeviation at distance and near. Local and global stereopsis was poor. Final refraction in the right eye was +2.50 D -0.50 D x 031 (acuity 20/100) and in the left eye was +5.75 D -1.00 D x 129 (acuity 20/20).
Both pupils were round, equal and reactive to light with a trace relative afferent pupillary defect (APD) in the right eye. Confrontation fields were full to finger counting in the right and left eyes, and ocular motility of each eye showed no restrictions. Slit lamp examination of the anterior segment was unremarkable. Intraocular pressure was 22 mm Hg OD and 19 mm Hg OS.
Pre-emptive ultra-widefield retinal imaging and iWellness spectral domain optical coherence tomography (Optovue) screenings during initial exam work-up assisted in early identification of severe abnormalities in the macula of the right eye.
Images: Belill N
Dilated stereoscopic fundus exam of the right eye confirmed an elevated macular area with hyperpigmentation extending to vessel arcades and nasal past the optic nerve. The optic nerve was obliquely inserted with good perfusion of neural rim. Severe retinal vessel tortuosity was seen throughout the entire posterior pole. An epiretinal membrane had vitreal adherence inferiorly to the macula. The peripheral retina was flat and intact 360 degrees in each eye without conditions predisposing to retinal detachment.
The left eye posterior segment examination was unremarkable.
The following tests were ordered: SD-OCT of the macula and optic nerve, automated visual fields and fundus autofluorescence imaging. Based on the symptoms and clinical findings in this case, differential diagnoses included: choroidal melanoma, retinal pigment epithelium (RPE) adenoma, retinoblastoma, and congenital combined hamartoma of the retina and RPE.
Working through the differentials
The presence of hyperpigmentation combined with the lack of leukokoria, vitritis or calcification made diagnosis of retinoblastoma unlikely. The absence of inflammation and retinal feeder vessels made a diagnosis of RPE adenoma unlikely. The lack of choroidal elevation, serous retinal detachment or orange lipofuscin pigmentation made the diagnosis of choroidal melanoma unlikely. Also, retinal vascular tortuosity is generally not associated with choroidal melanoma.
Imaging results
SD-OCT scans of the macula in the right eye revealed extremely abnormal sensory retinal and ganglion cell complex (GCC) thickness. There were no signs of elevation of the RPE or choroid, nor was there any evidence of retinal traction, calcification or optically empty cavities. SD-OCT scans of the optic nerve in the right eye resulted in abnormally thickened retinal nerve fiber layer (RNFL) around the entire disc. SD-OCT scans of the retina in the left eye showed normal sensory retinal and GCC thickness, but abnormally thick RNFL superiorly and inferiorly.
Automated visual fields were obtained. The results were normal, with reliable visual field sensitivity in both eyes. Fundus autofluorescence imaging results were mild hyperfluorescence in the fovea and macula of the right eye, while autofluorescence levels in the left eye were normal.
Normal occurrences
Hamartomas are benign overgrowths of mature cells and tissues that occur normally in the affected area or part. The fact that many cases are diagnosed in young children and infants lends support to the hypothesis that the lesions are congenital.
In 1973, Gass was the first to describe the entity called “combined hamartoma of retina and RPE.” He reported a series of children with unusual benign retinal tumors that were mistaken for choroidal melanoma or retinoblastoma. All were believed to be hamartomatous malformations involving the RPE, sensory retina, retinal blood vessels and overlying vitreous. What is remarkable about these clinical characterizations is that they were done in an era before OCT.
Combined hamartomas of retina and RPE characteristically appear as a unilateral solitary mass adjacent to or overlying a portion of the optic disc, with variable amounts of pigmentation, vascularity and gray-white tissue. The contraction of the fibroglial tissue can lead to visual disturbances, an epiretinal membrane and tortuosity of retinal vessels seen clinically. Initial symptoms of combined hamartoma of retina and RPE commonly include decreased vision and strabismus. An association with type 2 neurofibromatosis has been reported.
This patient’s management
The patient was educated about long-term visual protection strategies including: use of impact-resistant polycarbonate lenses, avoidance of tobacco products, healthy nutrition and regular physical activity to limit diabetes risk. Contact lenses were not advised due to the patient’s monocular status and risk for sight-threatening keratitis.
SD-OCT of the macula in the right eye showing extremely thick sensory retina with lack of choroidal elevation.
Our new 17-year old patient presented with a rare retinal tumor. The presumption that it is congenital is complicated by the fact that in this case it had never been previously identified. His eye exam results were reviewed from a visit elsewhere from 4 years prior. The documented findings included orthophoria, normal stereopsis and normal posterior pole. It was noted that the patient had refused pupil dilation against medical advice. He was diagnosed with strabismic amblyopia.
Whether the retinal tumor went undiagnosed at that visit is unknown, but entirely possible. In our clinic, the use of pre-emptive ultra-widefield retinal imaging and iWellness SD-OCT screenings as a standard part of every comprehensive exam work-up leads to the highest level of diagnostic accuracy and patient education.
This case serves also as a reminder to never diagnose amblyopia without ruling out organic causes of poor visual acuity. This rule especially applies when the eye with normal visual acuity has significant higher hyperopic refraction (as our patient did).
SD-OCT of the retinal nerve fiber layer and ganglion cell complex showing abnormal thickness greater in the right eye than the left.
- References:
- Arepalli S, et al. Retina. 2014;34(11):2202–2207. doi: 10.1097/IAE.0000000000000220.
- Gass JD. Trans Am Ophthalmol Soc. 1973;71:171–185.
- Rachitskaya A, et al. Combined Hamartoma of Retina and Retinal Pigment Epithelium. http://eyewiki.aao.org/Combined_Hamartoma_of_Retina_and_Retinal_Pigment_Epithelium. Updated October 17, 2015. Accessed January 12, 2016.
- Schachat AP, et al. Ophthalmology. 1984;91:1609-1615.
- For more information:
- Nicholas Belill, OD, owns a private solo optometric practice in Clio, Mich. He can be reached at lookatsign@gmail.com.
- Leo P. Semes, OD, is a professor of optometry, University of Alabama at Birmingham, and a member of the Primary Care Optometry News Editorial Board. He may be reached at: lsemes@uab.edu.
Disclosure: The authors report no relevant financial disclosures.