Report a case of a male patient with a macular scar compatible with ocular toxoplasmosis (OT) in right eye (RE) and review the relevant literature on this disease. A patient, who attended for a routine contact lens follow up, presented with amblyopic exotropia without any ocular disease. Best-corrected visual acuity of the affected eye was 20/40 with constant and mono-fixation exotropia. Ophthalmoscopic assessment revealed a macular scar compatible with OT. OT is the leading cause of infection in the posterior segment. Inactive cases could be asymptomatic and diagnosis requires a complete eye examination, providing a correct diagnosis and patient management.
Ocular toxoplasmosis is a non-curable infectious disease mainly caused by the parasite Toxoplasma gondii and is probably the most common cause of posterior segment infection in many countries [1,2]. Ocular toxoplasmosis primarily affects the retina and the most common ocular manifestation are chorioretinitis (inflammation of the choroid) [
Toxoplasmosis can be congenital or acquired [
A 46 years old male patient attended the clinic for the first time for a routine follow-up of his soft monthly disposable contact lenses. A full history was obtained including mode of contact lens use, previous eye problems and current ocular symptoms. The patient complained about intermittent dry eyes, itching, photophobia, and increasingly poorer CL-tolerance. He also reported poorer vision in one eye for many years (amblyopia) as well as a squint (strabismus) in his right eye (RE). There was no history of ocular surgery and no family history of any significant eye conditions.
Visual acuity (VA) in his RE was 20/40 with a subjective refraction of −6.25/−0.50 × 90˚. The left eye (LE) achieved 20/20 with a subjective refraction of −5.50/ −0.50 × 90˚. Cover test revealed a constant RE exotropia (distance 14Δ and near 10Δ).
Anterior eye examination with slit-lamp biomicroscopy revealed mild blepharitis (grade 2 in Efron grading scale) and slight peripheral corneal vascularization (grade 1 in Efron grading scale) in both eyes. Anterior chamber and media were clear. Posterior segment evaluation by direct undilated ophthalmoscopy revealed a chorioretinal scar in the right macular area, while no abnormalities were noted in the left eye (
When the findings were communicated to the patient, he recalled a long-standing retinal problem, diagnosed when he was about 7 years old, although he was unable to give any further details.
Following consideration of patient history and clinical findings the patient was diagnosed with bilateral, moderate myopia and astigmatism, bilateral evaporative dry eye associated with blepharitis, as well as inactive, longstanding ocular toxoplasmoxis in the RE.
No treatment was prescribed for ocular toxoplasmosis recommending eye examinations every six months. Eyelid hygiene, with the application of warm compresses for a few minutes, two times per day and tear film drops were prescribed to blepharitis management, and new
appointment to re-fit CL was propose after one month of blepharitis treatment.
Ocular manifestations produced by the parasite T. Gondii in human neonates were first described in 1929 and were accepted as a human disease in 1939 [1,2]. But until 1952 was not recognized as a disease that could affect adults. Until the late 1990’s ocular toxoplasmosis was considered as a late sign of congenital infection. Since 2000 it is recognised that the majority of cases of toxoplasmosis were secondary to infection acquired after birth [1,2].
Toxoplasma gondii is a protozoa parasite, which utilises cat as the final host, but also other animals such as mice, cows, sheep and pigs as well as humans, like intermediate hosts [2,3]. The three main forms of the parasite are: oocyst (spore form that is excreted in cat feces), tachyzoite (actively proliferating) and bradyzoite (inactive form that becomes encysted in the tissues) [1-3].
Seroprevalence of the disease varies considerably depending on socioeconomic and environmental factors, host age, genetics, immune status, parasite genotype and others [
Toxoplasmosis infection has two clinical forms: the congenital and the acquired [
The acquired form on the other hand is the most frequent clinical form (two thirds of cases are post-natally acquired) [
Ocular toxoplasmosis presents with three main phases: active, chronic or inactive and recurrent [1,5]. During the active phase the focus of chorioretinitis appears yellowish-white or white-gray, with a raised, oval or circular, with blurred edges and adjacent retinal edema due to the involvement of the inner layers of the retina [5,6]. The lesion may vary in size and can be small and punctate, and may affect two or more quadrants of the retina. Central lesions are common in the macular area, probably as a result of entrapment of free parasites in capillary perifoveal retinal terminals [1,4-6].
When the active phase is controlled, a very well defined atrophic retinal scar surrounded by a hyperpigmented border appears. The parasite cysts, containing inactive forms bradyzoites, may remain latent in the neuroretina during the lifetime of the patient without pathological effects [1,4-6].
Finally, a recurrent episode could occur, especially when the patient’s immune system is compromised. The cyst releases active parasites (tachyzoites) that invade and destroy healthy cells with new focus of chorioretinitis. Recurrences usually occur between the first and third decade of life [1,4-6] and affect from 20% to 80% of patients [
In cases of congenital infection with macular involvement, the patient will most likely experience a reduction in visual acuity, strabismus, nystagmus or leukocoria [5, 7]. When primary infection develops in adulthood, the patient may complain of decreased visual acuity, floaters or visual field defects [
Frequently, it is very difficult to distinguish whether the transmission is congenital or acquired, especially if the infection occurs in childhood because both present similar symptoms and alterations in the eye. Approximately two thirds of cases are acquired postnatally [
The great majority of cases of toxoplasmosis are based on clinical features detected on routine screening assessing the fundus and observing the presence of any chorioretinal scars similar to the findings of this case report [
During acute or active phase differential diagnosis with other types of infectious (toxocariasis, viral-induced necrotizing retinopathies, syphilis, diffuse unilateral subacute neuroretinitis, and aspergillus endophthalmitis), noninfectious (Behçet’s disease, multifocal choroiditis, panuveitis, serpiginous choroiditis, punctate inner choroidopathy) and ocular conditions (primary intraocular lymphoma) is necessary [
The diagnosis could be confirmed by serological tests ATX corroborating the patient’s exposure to the parasite [
In our case the history and symptoms of the patient did not reveal a definite previous diagnosis of ocular toxoplasmosis, but when retina scar was detected the patient was quizzed about a possible toxoplasmosis etiology and the patient recalled the eye examination when he was 7 years old. Therefore, the history and signs were in agreement with a diagnosis of congenital (or acquired) ocular toxoplasmoxis.
The aim of treatment is eliminate the parasite quickly, reduce the inflammation, limit the retinal damage, preventing future recurrences and avoid the spread of the parasite [6,9].
Active ocular toxoplasmosis is treated with antiparasitic drugs such as pyrimethamine, sulfadiazine and folinic acid [
Our case presented with a long-standing, well defined central retinal scar, but with absence of new chorioretinitis focus, compatible with an inactive phase of this disease and no treatment was required. However, the risk of recurrence episodes requires patient education and periodic follow up, to avoid visual acuity loss or other eye of health problems.
Ocular toxoplasmosis is a common identifiable cause of posterior uveitis, responsible for nearly 10% of cases with men more likely to be affected than women [
Several eye diseases may go undetected during routine eye examination. During the optometric examination of a subject with amblyopia, reduced VA is expected and this may mask the true etiologic cause, preventing an accurate diagnosis and possibly the most appropriate patient management. A detailed history and full ocular assessment including routine fundoscopy by either direct (ophthalmoscope) or indirect (slit-lamp and 90D Volk lens indirect ophthalmoscopy) methods are essential and provide the means to derive the correct diagnosis of amblyopic exotropia secondary to ocular toxoplasmosis. Ocular toxoplasmosis is a potentially blinding condition with possible recurrence. Patient education and regular follow up assessments, ideally including digital fundus photography, are useful to minimize the disease morbidity.
The authors would like to thank Dr. Sven Jonuscheit of Glasgow Caledonian University for reviewing the manuscript.