A 38-year-old Hispanic male presented for a second opinion about reduced visual acuity in both of his eyes. Recently, an ophthalmologist informed the patient that nothing could be done to improve his vision. The patient reported he had poor vision all of his life, but had greater difficulty seeing during the last three to four years. He also reported that his right eye turned outward, which had been a cosmetic concern. His medical history was significant for hyperlipidemia, for which he took Crestor (rosuvastatin, Abbott).

On examination, ocular motility testing showed an exotropia in the right eye that measured approximately 35 prism diopters. We documented no nystagmus. Confrontation fields were full to careful finger counting O.U. His pupils were equally round and reactive, with no afferent defect. His anterior segment exam was unremarkable. His IOP measured 14mm Hg O.U.

The dilated fundus exam showed clear media O.U. Both optic nerves appeared healthy with a moderate cup size. We noted significant lesions in the posterior poles and maculae of both eyes (figures 1 and 2). The peripheral retinae were normal O.U.

Take the Retina Quiz
1. What do the lesions in the maculae represent?

a. Chorioretinal scars.
b. Retinochoroidal scars.
c. Congenital colobomas.
d. Both a and b are correct. 

2. What would you expect his best-corrected visual acuity to be?

a. In the 20/30 to 20/50 range.
b. 20/60.
c. 20/200 to 20/400.
d. Hand motion.

3. What is the most likely diagnosis? 

a. Bilateral congenital hypertrophy of the retinal pigment epithelium (CHRPE).
b. Congenital rubella.
c. Congenital toxoplasmosis.
d. Cytomegalovirus (CMV) retinitis.

4. How do you explain the exotropia?

a. It is coincidental.
b. It is directly related to the underlying cause.
c. It is sensory in nature.
d. There is no way to know.

For answers, see below.

Discussion
Our patient had very large and prominent retinochoroidal scars that involved both maculae. Given the size and location, you would have expected that his visual acuity was quite poor. Indeed, the right eye exhibited 20/100 with eccentric fixation. The left eye, however, was able to see 20/30––which was astounding considering the location directly in the macula. In fact, if you had to predict which eye saw better, you likely would have been inclined to believe the right had better acuity because the lesion appeared to sit directly on the edge of the macula and extended more temporally. The lesion in the left eye seemed to involve much more of the macular area, and yet that eye saw better.

Traditionally, when patients are seen with macular scars such as this, we assume they stem from congenital toxoplasmosis because the lesions are so characteristic in appearance. So, how do you really know if this presentation was indeed caused by toxoplasmosis or another congenital condition? You don’t, unless it is discovered very early in life and blood studies are performed. However, most of these cases are not discovered and usually are found coincidentally as part of a routine exam.

Toxoplasmosis is caused by an intracellular parasite, Toxoplasma gondii. Active toxoplasmosis retinochoroiditis typically presents as a feathery, white or creamy-yellow lesion. The lesion may appear thick or have a slightly elevated appearance. Other findings include vitritis, papillitis, perivasculitis and sheathing of the retinal vessels. Anterior chamber cells may be common due to a “spill-over effect” from the active vitritis. With congenital toxoplasmosis, patients generally present with an inactive, chorioretinal scar. Most presentations occur in the posterior pole, and up to 40% are bilateral.¹

Congenital toxoplasmosis develops as a result of transplacental transmission. The degree and severity depends on which trimester the mother acquired the infection. The classic clinical triad of congenital toxoplasmosis includes: retinochoroiditis, cerebral calcifications and convulsions. Other findings include: hydrocephalus, microcephaly, organomegaly, jaundice, rash, fever and psychomotor retardation.¹ Also, there is a 30% incidence of retinochoroidal scarring in infants with congenital toxoplasmosis.² It is important to note, however, that toxoplasmosis acquired after birth rarely results in chorioretinitis.²

There is some debate as to when the ocular infection occurs. Is it present at birth, or does it develop within the first few months (or years) of life? In one study of 154 patients with active ocular toxoplasmosis, 8% of the patients had congenital disease and 11% had postnatal infection.^1,3 And, of particular importance, the exact time of infection could not be determined in 81% of cases.^1,3 This uncertainty may be due to a lack of screening for ocular involvement during the neonatal period. Unfortunately, relying on the patient to manifest symptoms is of no help with an infant. Further, many patients are often asymptomatic––even adults. 

It has been estimated that 70% to 80% of American women of childbearing age are at risk for contracting toxoplamosis. However, the incidence of acquiring toxoplasmosis during pregnancy is actually quite low, at 0.2% to 1% annually.¹ That said, a serologic survey conducted as part of the Third National Health and Nutrition Survey indicated 23% of adolescents and adults and 15% of women of childbearing age in the United States exhibit laboratory evidence of T. gondii infection.⁴

Further, there is some confusion between the terminology retinochoroidal vs. chorioretinal. The fact is that clinical appearance can be identical between the two, and the terms are often used interchangeably in the literature.^1,2 The distinction between them has to do with the primary site of the infection. If the origin of the infection primarily involves or starts in the retina, then it is termed a retinochoroiditis. On the other hand, if the origin of the infection is within the choroid, but extends anteriorly, it becomes a chorioretinal lesion. As mentioned previously, once the active inflammation is gone and only the scar remains, it is virtually impossible to distinguish between the two, except by knowing the initial cause––which, in patients such as ours, is assumed to be from congenital toxoplasmosis.

Reactivation of congenital toxoplasmosis is common, with one or more episodes occurring in up to 85% of patients.² Perhaps that explains why our patient noticed a change in his vision over the past three to four years. With reactivation, you would expect to see vitreous inflammation. This was not present at the time of our exam.

We explained the findings to our patient and gave him an Rx for glasses (with an add to help him read more effectively). We asked him to return if he noted any changes in visual acuity or if he began experiencing floaters.

This case was contributed by Hina Patel, O.D., resident at the Bascom Palmer Eye Institute in Miami.

1. Vitale AT, Foster CS. Uveitis affecting infants and children: Infectious causes. In: Hartnett ME. Pediatric Retina. Philadelphia: Lippincott, Williams & Wilkins; 2005:255-89.
2. Lambers SR. Ocular manifestations of intrauterine infections. In: Pediatric Ophthalmology and Strabismus. Taylor D, Hoyt GS, eds. 3rd ed. London: Elsevier Saunders; 2005:139-45.
3. Bosch-Driessen LE, Berendschot TT, Ongkosuwito JV. Ocular toxoplasmosis: clinical features and prognosis in 154 patients. Ophthalmology. 2002 May;109(5):869-78.
4. Jones JL, Kruszon-Moran D, Wilson M, et al. Toxoplasma gondii infection in the United States: seroprevalence and risk factors. Am J Epidemiol. 2001 Aug 15;154(4):357-65.

Answers to the Quiz
1. d
2. c
3. c
4. c