Macular thickness as a predictor of loss of visual sensitivity in ethambutol-induced optic neuropathy

Ethambutol is a common cause of drug-related optic neuropathy.Prediction of the onset of ethambutol-induced optic neuropathy and consequent drug withdrawal may be an effective method to stop visual loss.Previous studies have shown that structural injury to the optic nerve occurred earlier than the damage to visual function.Therefore,we decided to detect structural biomarkers marking visual field loss in early stage ethambutol-induced optic neuropathy.The thickness of peripapillary retinal nerve fiber layer,macular thickness and visual sensitivity loss would be observed in 11 ethambutol-induced optic neuropathy patients（22 eyes） using optical coherence tomography.Twenty-four healthy age-and sex-matched participants（48 eyes） were used as controls.Results demonstrated that the temporal peripapillary retinal nerve fiber layer thickness and average macular thickness were thinner in patients with ethambutol-induced optic neuropathy compared with healthy controls.The average macular thickness was strongly positively correlated with central visual sensitivity loss（r2=0.878,P=0.000）.These findings suggest that optical coherence tomography can be used to efficiently screen patients.Macular thickness loss could be a potential factor for predicting the onset of ethambutol-induced optic neuropathy.

Ethambutol-induced optic neuropathy with rare bilateral asymmetry onset:A case report

BACKGROUND Ethambutol-induced optic neuropathy(EON)most commonly manifests as bilateral symmetrical loss of vision and often cause serious and irreversible visual impairment because of the lack of early detection and effective treatment.We followed a case of EON with rare binocular asymmetric clinical manifestations and observed the changes of visual function and retinal structure after drug withdrawal,so as to further understand the clinical characteristics of this disease.CASE SUMMARY A 54-year-old man complained of gradual visual decline in the left eye.The patient presented with best-corrected visual acuity of 20/20 in the right eye and 20/50 in the left eye.Color vision examination revealed difficulty in reading green color plates in the left eye.The visual field manifested as concentric contraction in the left eye.After nearly a month of drug withdrawal,the right eye had a similar decline in visual function.At the last visit,19 mo after drug withdrawal,the visual function significantly recovered in both eyes.During follow-up optical coherence tomography(OCT)examination,both eyes manifested the thickness of the retinal nerve fiber layer from mild thickening to thinning and finally temporal atrophy,and the ganglion cell-inner plexiform layer showed significant thinning.The difference was that a reversible structural disorder in the outer retina of the nasal macula was detected in the left eye by macular high-definition OCT.CONCLUSION Nephropathy and high blood pressure,which damage the retinal microcirculation,may cause damage to the outer layer of the retina.Ethambutol may influence photoreceptor as well as retinal ganglion cells.

Structural impairment patterns in peripapillary retinal fiber layer and retinal ganglion cell layer in mitochondrial optic neuropathies

AIM：To evaluate the structural injure patterns in peripapillary retinal fiber layer （pRNFL）, retinal ganglion cell layer （RGCL） and their correlations to visual function in various mitochondrial optic neuropathies （MON） to offer help to their differential diagnosis.METHODS：Totally 32 MON patients （60 eyes） were recruited within 6mo after clinical onsets, including 20 Leber hereditary optic neuropathy （LHON） patients （37eyes）, 12 ethambutol-induced optic neuropathy （EON）patients （23 eyes）, and 41 age-gender matched healthy controls （HC, 82 eyes）. All subjects had pRNFL and RGCL examinations with optic coherence tomography （OCT） and visual function tests.RESULTS：In the early stages of MON, the temporal pRNFL thickness decreased （66.09±22.57μm）, but increased in other quadrants, compared to HC （76.95±14.81μm）. The other quadrants remaining stable for LHON and EON patients besides the second hour sector of pRNFL thickness reduced and the temporal pRNFL decreased （56.78±15.87μm） for EON. Total macular thickness in MON reduced remarkably（279.25±18.90μm; P=0.015）, which mainly occurring in the inner circle （3 mm diameter of circle） and the nasal temporal sectors in the outer circle （5.5 mm diameter of circle）, in contrast to those in HC. RGCL thickness reduced in each sector of the macula （61.90±8.73μm; P≤0.001）. It strongly showed the correlationship of best corrected visual acuity （R=0.50, P=0.0003） and visual field injury （R=0.54,P=0.0002） in MON patients.CONCLUSION：OCT is a potential tool for detecting structural alterations in the optic nerves of various MON. Different types of MON may have different damage patterns.