Hypoglobus, Exophthalmos, and Interpupillary Distance: Measuring Globe Dystopia in Thyroid Eye Disease.

PURPOSE: Thyroid eye disease (TED) is characterized by a variety of disfiguring periocular changes. Vertical globe changes affecting the relative position of the eyelids are not well understood in patients with TED. This study seeks to determine the effect of orbital decompression on vertical globe displacement in patients with TED, without TED, and with intraconal tumor (ICT). METHODS: For this cross-sectional study, a clinical database was used to identify patients with TED. Comparison groups were drawn from separate anonymized databases. Vertical position and interpupillary distance (IPD) were measured from photographs and exophthalmos was measured via Hertel's exophthalmometer. Primary outcomes were vertical globe position at baseline and postoperatively in patients with TED and ICT. Secondary outcomes included the relationship between vertical globe position, exophthalmos, and IPD. RESULTS: Among 269 participants meeting the inclusion criteria, mean vertical globe position was significantly lower in patients with TED following lateral decompression surgery compared to controls, after accounting for race, age, and sex. While patients with ICT had a significant difference in preoperative and postoperative IPD, patients with TED did not. Medial or inferior decompression did not significantly change globe position and lateral decompression did not cause lateral canthal dystopia in patients with TED. No association between postoperative changes in exophthalmometry, IPD, and globe position was found in patients with TED. CONCLUSIONS: Patients with TED experience hypoglobus that does not improve following decompression surgery. There was no correlation between change in vertical globe position and exophthalmos or IPD among patients with TED. Surgeons should discuss the possibility of hypoglobus as a persistent finding for patients with TED undergoing decompression surgery.

Extrascleral extension of choroidal melanoma after iodine-125 brachytherapy treatment: a case series.

BACKGROUND/OBJECTIVES: The purpose of this study is to report cases of choroidal melanoma that developed extrascleral tumour recurrence after treatment with iodine-125 brachytherapy. SUBJECTS/METHODS: In this single-institution retrospective observational case series, all instances of biopsy-confirmed orbital melanoma after known intraocular melanoma were reviewed. Tumour characteristics, clinical course, time to recurrence, cytogenetics of initial tumour and recurrence, and presence of intraocular recurrence were documented. RESULTS: Five cases of orbital melanoma following treatment with plaque radiotherapy are described. Tumour staging was Ia (1), IIa (2), and IIb (2). The primary lesion in four of the five appeared to have undergone complete regression for an average of 2 years, with the orbital melanoma developing after this interval. Recurrence of the intraocular tumour was seen in conjunction with an extrascleral component in two cases. Four cases ultimately underwent enucleation or exenteration; three had evidence of direct extension of tumour through the sclera. Four cases in this series had molecular characteristics associated with high metastatic risk (three patients with monosomy 3, one with BAP1 mutation). CONCLUSIONS: High-risk tumour biology may predispose to late appearance of extrascleral melanoma despite optimal treatment and adequate control of the intraocular tumour. Extended follow-up with detailed orbital examination and imaging is recommended for this population.

Carcinoid Tumors of the Orbit and Ocular Adnexa.

PURPOSE: Well-differentiated neuroendocrine or carcinoid tumors are found most commonly in the gastrointestinal tract. When metastatic to the orbit, they tend to have a propensity for the extraocular muscles. The purpose of this study was to better understand the diversity in presentation of orbital carcinoid disease and to determine predictors for survival. METHODS: In this observational cross-sectional cohort study, data from 8 tertiary orbital practices were compiled. Demographic, clinical, pathologic, American Joint Committee on Cancer stage and grade, imaging, and management data were extracted for all the patients. Descriptive statistics were calculated. Subgroups were compared utilizing analysis of variance analyses and Kaplan-Meier curves. Time to progression and disease-specific and overall mortality were calculated. Comparisons were performed for the following a priori pairs: unknown versus known primary tumor, single versus multiple extraocular muscle involvement, unilateral versus bilateral orbital disease, extraocular muscle versus other orbital involvement, and excisional versus incisional surgery. RESULTS: A total of 28 patients with carcinoid tumors of the orbit were identified. Of these, 57.1% of patients were female, the mean age at diagnosis of the primary tumor was 58.8 years and the mean age at diagnosis of orbital disease was 62.6 years. At primary presentation, all patients were American Joint Committee on Cancer stage III or IV and 21.4% demonstrated carcinoid syndrome. Muscle involvement was noted in 78.6% of patients, and of these, 72% were noted to have single muscle disease. Eight patients had no primary tumor identified; 3 of these 8 demonstrated disseminated disease at the time of diagnosis. The overall 5-year survival rate was 81.8% from diagnosis of primary tumor and 50% from diagnosis of orbital disease. Subgroup analysis revealed that patients with unilateral orbital disease when compared with bilateral orbital disease had a longer progression-free survival and time to death from all causes (p = 0.025). Patients with disease localized to the orbit at presentation had longer time to death than those with disseminated disease. Treatment with surgery, radiation, or octreotide did not appear to affect survival. Patients managed with systemic chemotherapy had a shorter time of survival than the rest of the group. All other subgroup comparisons were not found to be statistically significant. CONCLUSIONS: Neuroendocrine tumors of the orbit represent a wide spectrum of disease, with some cases being part of disseminated disease, while others being localized presentations. This heterogeneity may be responsible for the slightly higher overall survival in these patients than others with metastatic carcinoid tumors in other locations.

Cone Beam Computerized Tomography Dacryocystography (CBCT DCG) for the Evaluation of Lacrimal Drainage System Dysfunction.

PURPOSE: Lacrimal outflow imaging has been limited in clinical practice due to a combination of modality limitations and efficacy of clinical testing. Cone beam computed tomography dacryocystography (CBCT DCG) has certain advantages over other modalities that may enhance clinical utility. This study was intended to understand the relationships between symptoms, syringing and CBCT DCG in a population of patients presenting with tearing. METHODS: Cross-sectional cohort study of adult patients undergoing both CBCT DCG and clinical probing and irrigation. Concordance analysis between symptoms, clinical examination, and CBCT DCG was performed at baseline and postoperatively in patients who were treated with dacryocystorhinostomy. RESULTS: CBCT DCG findings correlate fairly well with probing/irrigation (Cohen kappa = 0.376). Excluding cases of canalicular obstruction identified by either method, the correlation between CBCT DCG and probing/irrigation was moderately improved (Cohen kappa = 0.488). There was no statistically significant difference in correlation with patient symptoms between CBCT DCG and probing/irrigation (p = 0.877). Fifteen patients (17 lacrimal systems) patients underwent endoscopic dacryocystorhinostomy (DCR) surgery. Ten demonstrated absence of symptoms 90 days postoperatively, 3 endorsed continued tearing and 2 were lost to follow up. All 3 who demonstrated continued tearing, demonstrated canalicular obstruction on CBCT DCG which was not initially detected on probing/irrigation. CONCLUSIONS: CBCT DCG correlates moderately well with probing and irrigation, as well as patient symptoms. This technology may assist in identification of functional/anatomic canalicular obstruction.

Contralateral Precaruncular Approach to the Lateral Sphenoid Sinus-A Case Report Detailing a New, Multiportal Approach to Lesions, and Defects in the Lateral Aspect of Well-Pneumatized Sphenoid Sinuses.

INTRODUCTION: Conventional surgical approaches to the lateral aspect of a well-pneumatized sphenoid sinus are associated with significant surgical morbidity. Transorbital endoscopic approaches have recently gained favor as an alternative approach to the skull base. We describe the use of a contralateral precaruncular endoscopic approach to provide a surgical pathway to the lateral aspect of the sphenoid sinus, allowing for improved and direct visualization of the surgical field, with limited morbidity. CASE REPORT: A 60-year-old female patient, with a spontaneous cerebrospinal fluid leak from a Sternberg canal defect in the sphenoid sinus, underwent repair of the defect at Groote Schuur Hospital (Cape Town, South Africa). A contralateral precaruncular approach, using the left medial orbital portal, was utilized to access the defect in the lateral aspect of a well-pneumatized right sphenoid sinus. Computer modeling software was used to predetermine the surgical pathway, and the case was performed under navigation guidance. Adequate surgical access was obtained to the lateral sphenoid sinus and sinus defect, with superior visualization compared to a pure transnasal or transpterygoid approach to the lateral sphenoid sinus. CONCLUSIONS: This case validates the use of computer simulation to plan and decide on the best operative approaches in skull base surgery and describes the contralateral precaruncular approach as a surgical pathway to the lateral sphenoid sinus. Advantages of the contralateral precaruncular approach include a direct trajectory toward the sinus defect, easy access with a standard 18-cm, 4-mm, 0-degree rigid endoscope, and straight instruments, with sparing of the pterygoid base and contents of the pterygopalatine fossa.

Development of the international orbital Cavernous Hemangioma Exclusively Endonasal Resection (CHEER) staging system.

BACKGROUND: Orbital cavernous hemangiomas (OCH) are the most common adult orbital tumor and represent an ideal index lesion for endonasal orbital tumor surgery. In order to standardize outcomes reporting, an anatomic-based staging system was developed. METHODS: An international, multidisciplinary panel of 23 experts in orbital tumor surgery was formed. A modified Delphi method was used to develop the cavernous hemangioma exclusively endonasal resection (CHEER) staging system with a total of 2 rounds being completed. RESULTS: Tumors medial to a plane along the long axis of the optic nerve may be considered amenable for an exclusively endonasal resection. In select cases, tumors may extend inferolaterally if the tumor remains below a plane from the contralateral naris through the long axis of the optic nerve (ie, plane of resectability [POR]). This definition reached consensus with 91.3% of panelists in agreement. Five stages were designed based on increasing technical resection difficulty and potential for morbidity. Stages were based on the relationship of the tumor to the extraocular muscles, the inferomedial muscular trunk of the ophthalmic artery (IMT), and orbital foramina. Staging by anatomic location also reached consensus with 87.0% of panelists in agreement. Size was not included in the staging system due to the lack of agreement on the contribution of size to resection difficulty. CONCLUSION: Endoscopic orbital tumor surgery is a nascent field with a growing, yet heterogeneous, body of literature. The CHEER staging system is designed to facilitate international, high-quality, standardized studies establishing the safety, efficacy, and outcomes of endonasal resection of OCH.

Role of Retrobulbar Hyaluronidase in Filler-Associated Blindness: Evaluation of Fundus Perfusion and Electroretinogram Readings in an Animal Model.

PURPOSE: Hyaluronic acid gel filler-associated blindness is an uncommon but devastating complication. Hyaluronidase can potentially dissolve intravascular filler and improve perfusion; however, its role in filler-associated blindness has yet to be determined. The purpose of this study is to determine the effect of retrobulbar hyaluronidase on hyaluronic acid gel-induced ophthalmic artery occlusion in a rabbit model. METHODS: New Zealand red rabbits were used to simulate hyaluronic acid gel filler-associated vascular occlusive blindness. Ophthalmic artery occlusion and subsequent ischemia were confirmed by both retinal fundus photography and electroretinogram changes. Retrobulbar hyaluronidase 1,000 IU was injected 30 minutes after occlusion. Fundus photography and electroretinogram changes were recorded at 30, 60, 90, and 120 after administration of retrobulbar hyaluronidase. RESULTS: A total of 6 rabbits were used, for a total of 12 eyes. Four eyes were used as controls. Of the 8 experimental eyes, 2 eyes had recorded partial occlusion and 6 eyes had fully occluded ophthalmic arteries by angiographic evaluation. One of the partially occluded eyes demonstrated some improvement in perfusion 60 minutes after injection of retrobulbar hyaluronidase; however, electroretinogram readings remained flat over the 120-minute period of observation. Six eyes with completely occluded ophthalmic arteries showed no improvement in retinal perfusion with corresponding flat electroretinogram readings at 120 minutes following retrobulbar hyaluronidase injection. CONCLUSIONS: In this rabbit model, 1,000 IU of retrobulbar hyaluronidase administered 30 minutes after occlusion failed to reverse obstruction or restore function following hyaluronic acid gel occlusion of the ophthalmic artery.

Clinical Manifestations and Cerebrospinal Fluid Status in Ocular Syphilis.

PURPOSE: To review the clinical manifestations, cerebrospinal fluid findings and outcomes of patients diagnosed with ocular syphilis. METHODS: Retrospective case review of all patients treated with ocular syphilis at Groote Schuur Hospital in Cape Town, South Africa between January 2008 and January 2013. RESULTS: A total of 77 eyes of 49 patients were included. Panuveitis was the most common presenting sign (48.9%). A lumbar puncture was performed on 37 patients (75.5%) and 64.8% (24/37) of samples had positive treponemal testing (CSF-FTA) while 24.3% (9/37) had positive non-treponemal testing (CSF-VDRL). Elevated CSF lymphocyte cell count was a strong predictor of neurosyphilis (p = 0.06 for CSF-FTA positive samples and p = 0.03 for CSF-VDRL positive samples). CONCLUSION: The majority of patients (64.8%) who underwent lumbar puncture had cerebrospinal fluid findings suggestive of neurosyphilis. Elevated CSF lymphocyte cell count and total protein count are highly suggestive of neurosyphilis.

Use of Botulinum Toxin for the Correction of Mild Ptosis.

Background: Lid margin asymmetry and its associated compensatory mechanisms might cause patients to seek treatment to improve aesthetics. Surgery might not be indicated and can potentially worsen the asymmetry in these cases. Methods: A case series of three patients was organized to illustrate the use of botulinum toxin administered to the pre-tarsal orbicularis for the correction of micro-ptosis and improved symmetry. The marginal reflex distance and tarsal platform show were measured on both sides. Measurements were made using ImageJ software on standardized frontal photographs taken pre- and post-injection. Results: The average increase in the marginal reflex distance was 0.914mm, with an average pre-tarsal botulinum toxin dose of three units. The average change in tarsal platform show between the two eyes was 0.89mm. Conclusion: Botulinum toxin application to the pre-tarsal orbicularis oculi muscle might be a suitable option for the management of small eyelid margin asymmetries.

Eyebrow Contouring with Hyaluronic Acid Gel Filler Injections.

Background: The eyebrow region presents challenges for filling: the skin is thick, the three-dimensional anatomy is complex and there is a predisposition towards fat atrophy and skeletonization with aging. Hyaluronic acid gel fillers are well known for their use in the periorbital region. We report our long-term experience with eyebrow filling over a period of five years. Methods: Twenty cases of periorbital eyebrow filling with hyaluronic acid gel fillers were followed up over a period of five years. The eyebrow filling was customized based on the patient's anatomical features in a three-dimensional plane. Standardized photographs before and after the procedure in standard lighting conditions were evaluated. Results: Hyaluronic acid gel fillers were tolerated well in the eyebrow region. There were no cases with blue-gray dyschromia or prolonged edema as is the case with lower eyelid injections. The eyebrow gained volume and looked fuller immediately after the injection. There were three cases with excessive eyebrow puffiness noted on a long-term follow-up which may be the accumulated filler weighing the eyebrow. No other adverse events were noted. Conclusion: The eyebrow anatomy is a complex three-dimensional structure. Deflation in the eyebrow area along with the superior sulcus occurs with aging. Filling the eyebrow with hyaluronic acid gel fillers is a useful tool in the armamentarium of the cosmetic facial surgeon and can be used in isolation in select patients or as an adjunct to surgical rehabilitation. We believe the fillers last longer and are well tolerated in the eyebrow region due to the complex anatomy specific to this region.

Medial Buttressing in Orbital Blowout Fractures.

PURPOSE: To study whether ethmoidectomy predisposes the orbit to medial wall fracture with lesser trauma. METHODS: An interventional cadaver study of 5 heads (10 orbits); the left or right orbit was randomized to undergo endoscopic complete ethmoidectomy with the fellow orbit as control. Fractures were induced with direct globe trauma, and heads underwent CT scanning. Energy to induce fracture, peak orbital pressure at time of fracture, fracture pattern, and volume of herniated tissue were measured and analyzed. RESULTS: Fractures were induced in both orbits of all cadavers. Experimental orbits after ethmoidectomy sustained orbital fracture at less energy required (2.14 ± 0.66 vs. 3.10 ± 0.19 J, mean difference: -0.96 ± 0.33 J, p < 0.05). Similarly, peak orbital pressure was lower for ethmoidectomized orbits than for controls (11.8 ± 8.42 vs. 28.4 ± 13.2 mm Hg, mean difference: -16.5 ± 6.9 mm Hg, p < 0.05). Orbits after ethmoidectomy were more likely to sustain medial wall involvement in fracture (100%) compared with controls (20%, p < 0.05) and pure medial wall fracture (80%) compared with controls (0%, p < 0.05). Overall volume of herniated orbital contents was not significantly different between groups (p = 0.25); volume of herniated tissue from the medial wall only was significantly greater in orbits after ethmoidectomy (mean difference: 1.01 ± -0.39 cm, p < 0.05). CONCLUSION: Endoscopic ethmoidectomy in fresh cadavers reduces impact energy necessary to induce orbital fracture and increases the prevalence of medial wall involvement. Clinicians may wish to counsel patients undergoing endoscopic sinus surgery about these relative risks.

Anomalous Sphenoid Diploe Vein: Case Report Highlighting the Value of Careful CT Evaluation Prior to Decompression Surgery.

Lateral bony decompression may offer several biomechanical advantages and has become a commonly used surgical approach. Preoperative imaging plays a key role in surgical planning by providing information about the locoregional anatomy. The marrow space of the greater wing of the sphenoid is a focal point of the decompression surgery based on the volume that it occupies. Several vessels pass through the sphenoid bone, but most are small caliber vessels. The authors describe a case of an uncommon anatomical variant of the cranial diploic venous system in which the anterior transverse diploic vessel traverses the marrow space of the sphenoid. The vessel was identified on preoperative CT evaluation. Despite anticipation of potential bleeding, lateral decompression was abandoned due to difficulties in maintaining hemostasis which compromised the view for safe surgical progress.

Filling the periorbital hollows with hyaluronic acid gel: Long-term review of outcomes and complications.

INTRODUCTION: Hyaluronic acid gel has been used for rejuvenation of the periorbital tissues since 2004. The in-office, nonsurgical procedural nature has resulted in the growing popularity of the use of fillers. The periorbital region poses unique challenges to the cosmetic surgeon. Malar edema, blue-gray dyschromia, and contour irregularities are well reported short-term complications. We present a long-term follow-up review of complications associated with periocular injection of hyaluronic acid gel fillers. METHODS: Retrospective review of 147 patients with at least a 5-year follow-up period since the first injection. Five senior masked reviewers were asked to grade photographs of patients in comparison with preinjection photographs. Grading was based on a reference photographic key looking specifically at the presence and severity of malar edema, blue-gray dyschromia, and contour irregularity. RESULTS: Malar edema (11%), blue-gray dyschromia (31.3%), and contour irregularities (30.5%) continue to be problems in longer term follow-up of patients. The vast majority (90%) of these complications were mild and required no intervention. There is no statistically significant difference in the mean volumes injected by severity grading of each measured complication. CONCLUSION: Hyaluronic acid gel fillers of the periorbital region are well tolerated in our long-term follow-up experience. The vast majority of cases of malar edema, blue-gray dyschromia, and contour irregularities are mild and do not require intervention. Conservative treatment and tailored treatment approaches, in terms of volume and frequency of injections, may decrease the tendency of these adverse effects to occur.

Clinical Profile and Outcomes of Optic Neuritis in an HIV Prevalent Urban Community in South Africa.

PURPOSE: To determine the clinical profile, causes and response to corticosteroid therapy in patients admitted and treated for optic neuritis at a tertiary hospital in Cape Town, South Africa. METHODS: A retrospective case review of 117 patients with optic neuritis between January 2002 and December 2012. Demographic information, clinical presentation, course of illness, investigations performed and visual outcomes at discharge and at three month follow up were collected for analysis. RESULTS: 60 of 117 patients (51%) had an identifiable secondary cause for optic neuritis. Of the 57 patients with idiopathic optic neuritis, 14 had features associated with demyelinating disease. HIV and syphilis accounted for 62% of secondary causes of optic neuritis. Presenting visual acuity of hand movements (HM) or worse and absence of pain with extra ocular movement were associated with poorer final visual outcomes in the idiopathic optic neuritis group. CONCLUSION: Optic neuritis in our patients, as elsewhere in Africa, tends to be atypical in presentation. A high proportion of patients have an identifiable secondary cause. These patients thus require more extensive investigation in order to identify causes which may influence management. Secondary optic neuritis and idiopathic atypical optic neuritis carry a poorer prognosis than typical demyelinating optic neuritis.

Using the Postoperative Visual Acuity to Monitor the Quality of Cataract Surgery: Does the Day One Visual Acuity following Cataract Surgery Correlate with the Final Visual Acuity?

PURPOSE: Monitoring the visual acuity following cataract surgery is used as a measure of the quality of the surgery in blindness prevention programs in middle- and low-income countries. While the day 1 visual acuity is usually available, the (final) visual acuity after several weeks may not be available, as the majority of patients may not return for review. This study was undertaken to ascertain if the early and late visual acuities are correlated and if the day 1 visual acuity can be used to predict the likely final visual acuity. METHODS: A retrospective case note review was undertaken of all eyes having cataract surgery over a 6-month period. RESULTS: There was a positive correlation between the day 1 and week 6 visual acuities in both the World Health Organization categories (Spearman coefficient = 0.4666, P = 0.001) and the logMAR visual acuity scores (Spearman coefficient = 0.5425, P = 0.001). CONCLUSION: In blindness prevention programs in middle- and low-income countries with poor postoperative follow-up where it is not possible to document the final visual acuity in all the operated cases, there is merit in documenting and monitoring the day 1 visual acuity as a quality control measure.

How useful is visual field testing in an African glaucoma clinic?

PURPOSE: To investigate the usefulness of visual field testing in the diagnosis and subsequent management of glaucoma in a specialist glaucoma clinic at Groote Schuur Hospital, Cape Town, South Africa. METHODS: A retrospective case note review of 344 patients who attended the glaucoma clinic between January and June 2010. RESULTS: The study population consisted of 201 (58%) females and 143 (42%) males. The diagnoses included 207 (60%) cases with primary open-angle glaucoma, 58 (17%) cases with chronic angle closure glaucoma, 46 (13%) cases with secondary glaucoma, 17 (5%) cases with normal pressure glaucoma, ten (3%) cases with ocular hypertension, and six (2%) glaucoma suspects. Visual field testing contributed to the diagnosis of glaucoma in only 34 (10%) cases. A total number of 2,604 fields were performed. Of these fields, 1,931 (74%) were reliable. A baseline was reached in only 141 (53%) patients. There was evidence of field progression in only 24 (9%) cases. Changes to glaucoma treatment were based on inadequate control of intraocular pressure alone in 309 (90%) patients. Visual field progression contributed to changes in treatment in only 15 (4%) cases. CONCLUSION: Visual fields are not used in the diagnosis and management of glaucoma in the majority of patients in our clinic. Patients present with advanced disease, which is easily diagnosed without the use of visual fields. Progression of fields seldom contributes to monitoring and intraocular pressure is mainly used to monitor the adequacy of treatment.

Sutured posterior chamber intraocular lenses for traumatic cataract in Africa.

PURPOSE: To determine the outcomes of sutured scleral fixation of posterior chamber intraocular lenses (PC IOLs) after trauma in an African population. SETTING: State hospital and affiliated district hospital, Cape Town, South Africa. DESIGN: Case series. METHODS: A retrospective review was performed of the medical records of patients in whom a sutured PC IOL had been implanted for traumatic aphakia in the preceding 5 years. RESULTS: Eighty-five percent of the 59 patients had a significant improvement in uncorrected distance visual acuity (UDVA) at the final visit. Two-thirds of patients achieved an UDVA of 6/18 or better. Those not improving had severe preexisting macular or corneal pathology. A significant number of patients (28%) with angle recession developed ocular hypertension during the postoperative period. CONCLUSION: After careful preoperative selection, sutured PC IOLs were effective in the visual rehabilitation of eyes with traumatic subluxated cataract in which the capsular bag could not be retained. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Ethambutol induced toxic optic neuropathy in HIV positive patients.

AIM: To determine whether HIV and the use of antiretroviral therapy is a risk factor for the development of ethambutol toxic optic neuropathy. To describe the clinical course of ethambutol toxic optic neuropathy in patients with HIV and to identify prognostic factors. METHODS: The case notes of 14 consecutive patients referred to the neuro-ophthalmology clinic were reviewed. Data regarding HIV status, antiretroviral therapy, visual function, ethambutol therapy dosage, and ethambutol therapy duration were collected and analysed. RESULTS: Eleven of the 14 patients were HIV positive. Ten of the HIV positive patients were receiving antiretroviral therapy. The mean dose of ethambutol was 17.25mg/kg/day. No statistically significant difference in mean dose, duration of therapy, age or CD4 count was found between those who showed visual improvement and those who did not. Delay in presentation of more than one month post symptom onset was correlated with poor visual outcome (P=0.001). CONCLUSION: HIV and, perhaps more importantly, the potential mitochondrial toxic effects of Nucleoside analogue reverse transcriptase inhibitors (NRTIs) may be a risk factor for the development of toxic optic neuropathy from ethambutol therapy via a multiple hit effect. Delay in presentation results in poor visual outcome. Regular monitoring is recommended for HIV positive patients receiving antiretrovirals and requiring ethambutol therapy in order to avoid permanent visual loss.