Early paracentral visual field loss in patients taking hydroxychloroquine.

OBJECTIVE: To review the natural history and ocular and systemic adverse effects of patients taking hydroxychloroquine sulfate who attended an ophthalmic screening program. DESIGN: Retrospective study. RESULTS: Records of 262 patients who were taking hydroxychloroquine and screened in the Department of Ophthalmology were reviewed. Of the 262 patients, 14 (18%) of 76 who had stopped treatment at the time of the study experienced documented adverse effects. Systemic adverse effects occurred in 8 patients (10.5%) and ocular adverse effects, in 5 (6.5%). Thirty-five patients (13.4%) had visual field abnormalities, which were attributed to hydroxychloroquine treatment in 4 patients (1.5%). Three of the 4 patients were taking less than 6.5 mg/kg per day and all patients had normal renal and liver function test results. CONCLUSIONS: The current study used a protocol of visual acuity and color vision assessment, funduscopy, and Humphrey 10-2 visual field testing and shows that visual field defects appeared before any corresponding changes in any other tested clinical parameters; the defects were reproducible and the test parameters were reliable. Patients taking hydroxychloroquine can demonstrate a toxic reaction in the retina despite the absence of known risk factors. Screening, including Humphrey 10-2 visual field assessment, is recommended 2 years after the initial baseline and yearly thereafter.

The value of VEP in the diagnosis and post-operative monitoring of meningioma.

Meningiomas are the most frequently reported primary intracranial neoplasms. At first they usually cause unilateral visual loss but eventually result in a bilateral loss of vision. Depending upon the size and location of the tumour, the ocular signs and symptoms of meningiomas may include visual field abnormalities, optic atrophy, papilledema, diplopia and proptosis. This case report highlights the value of visual evoked potentials (VEP) in a patient with unexplained bilateral optic atrophy and a progressive loss of vision over 2 years. As a result of a delayed response in the VEP recorded from the right eye, a compressive lesion of the optic nerve was suspected. That prompted the referring ophthalmologist to request a MRI scan which led to the diagnosis of meningioma. Following the subtotal removal of the suprasellar meningioma, the remaining vision in the right eye improved and the latency of the VEP returned to the normal range. However, the VEP from the blind eye (left) did not show any measurable response either pre- or postoperatively. Experience with this patient suggests that early recognition of optic nerve compression is vital to an optimal outcome and the VEP technique, which is much more cost-effective than MRI, is clinically useful for detecting such compressive lesions.

EOG as a monitor of desferrioxamine retinal toxicity.

Iron overload caused by blood transfusion-dependent anaemia usually results in lethal cardiac toxicity unless treated by iron-chelation therapy. Chelation therapy with desferrioxamine (DFO) is well established and widely used to remove excess iron. Unfortunately, visual disorders have been recorded after DFO infusion. In this investigation, a 61-year-old Caucasian female received DFO for her autoimmune haemolytic anaemia. Prior to starting with the DFO treatment, her baseline ophthalmic screening and electrooculogram (EOG) were completely normal. Two years later she noticed a grey scotoma in her right eye. Visual acuity in this eye was reduced from 6/5 to 6/9 and funduscopy revealed evidence of non-specific mottling of the retinal pigment epithelium of both retinae. The EOG was flat (106%) in the right eye and subnormal in the left (155%). The lower limit of our EOG Arden Ratio for normal subjects is 180%. After her DFO treatment was stopped, her right visual acuity returned to 6/5, her field tests showed progressive improvement bilaterally and the EOG went back to the normal range. While waiting for splenectomy, the patient was restarted on a lower dose of DFO and EOG measurements were carried out every two (or three) weeks to monitor for DFO toxicity. The EOG varied during this period indicating some deterioration of function in the retinal pigment epithelium. However, normalisation of the EOG values (right = 217%, left = 217%) occurred after splenectomy and cessation of DFO therapy. Her visual function was normal and her visual acuity 6/4 bilateral when she was discharged from our outpatient clinic. On reviewing her history it was apparent that the EOG was the most sensitive indicator of DFO toxicity.

Influence of axial length of normal eyes on PERG.

The influence of the axial length (AL) of the eye on flash electroretinogram (ERG) responses has been well established in the literature, suggesting an association between ERG abnormalities with myopia (AL > 25 mm). The aim of our present study was to determine whether the AL of normal eyes can also influence the pattern electroretinogram (PERG) on normal subjects. Thirty-nine normal volunteers were subjected to PERG measurements following the standard set by the International Society for Clinical Electrophysiology of Vision (ISCEV). The AL of the eyeball was measured using a TOMEY ultrasonic A scanner. Each volunteer had a complete ophthalmic examination including visual acuity, refraction, intraocular pressure, visual field, colour vision, orthoptic assessment and retinal photographs and had a best corrected visual acuity of 6/9 or better. Only one eye from each of the 39 normal volunteers was included in the statistical analysis of the results. The normal volunteer group had a mean P50 amplitude of 3.8 +/- 1.1 SD microV. The range of AL was between 21.8 and 25.7 mm (mean = 23.8 +/- 1.0 SD mm). Overall findings obtained from this investigation indicate a significant correlation between the AL of normal eyes and the PERG P50 amplitude (Spearman rank correlation coefficient r = -0.413, p < 0.01). The correlation accounts for 17% of the variance observed in the 39 amplitude values. This confirms the current hypothesis that the PERG amplitude is inversely related to axial length and means that AL should be considered when interpreting PERG amplitudes.