Wico W. Lai

Choroidal thickness in relation to hypercholesterolemia on enhanced depth imaging optical coherence tomography.

Purpose: To investigate the relationship of hypercholesterolemia and choroidal thickness in normal healthy volunteers. Method: This was a cross-sectional observational study. Volunteers with no ocular abnormalities were examined using enhanced depth imaging optical coherence tomography. Choroidal and retinal thicknesses were measured at the fovea, and at 4 different locations 1 mm superior, inferior, temporal, and nasal to the fovea. Subjects were further divided into those with hypercholesterolemia (Group 1) and normal control subjects (Group 2) for subgroup analysis regarding the effect of hypercholesterolemia on choroidal thickness. Subjects with hypertension and diabetes were excluded. Results: A total of 322 eyes of 161 subjects were studied. Mean age was 59.9 years (range, 24–84 years). The mean subfoveal choroidal thickness was 261 ± 98.7 &mgr;m. Mean subfoveal choroidal thickness negatively correlated with age (r = −0.326; P = 0.001). The mean serum total cholesterol was 5.02 ± 0.98 mmol/L. In Group 1, it was 5.65 ± 1.15 mmol/L, while in Group 2, it was 4.72 ± 0.73 mmol/L. The difference was statistically significant (P = 0.003). Subjects in Group 1 tended to be older and have worse vision, although the difference did not reach statistical significance. The mean subfoveal choroidal thickness in Group 1 was 306 ± 111 &mgr;m, while that in Group 2 was 258 ± 97 &mgr;m. The difference was statistically significant (P = 0.041). The same difference was also found at the 1 mm nasal (P = 0.041) and 1 mm superior (P = 0.040). Conclusion: The subfoveal choroidal thickness was found to be significantly higher in subjects with hypercholesterolemia. This has to be taken into account when analyzing choroidal thickness.

Enhanced depth imaging optical coherence tomography.

Imaging the choroid with conventional commercial spectral-domain optical coherence tomography (SD-OCT) has been difficult, mainly because of difficulty in signal transmission beyond the retinal pigment epithelium. A recent modification to the standard technique, termed enhanced depth imaging optical coherence tomography (EDI-OCT), was able to image the choroid with reasonable clarity using commercial SD-OCTs. The aim of this article was to review the technique, principle, recent findings, and possible future developments regarding EDI-OCT. A MEDLINE search on all published articles on EDI-OCT was performed up to December 2010. The principle behind EDI-OCT was discussed. Modification to the conventional technique in image acquisition was described and illustrated with figures. EDI-OCT findings in various retinal and choroidal diseases were discussed. Advantages and disadvantages were also discussed. EDI-OCT has proved to be a promising novel technique in imaging the choroid.

Racial and Ethnic Differences in Ocular Anatomy

Differences in eyelid structure are well described in the literature with respect to the Asian eyelid, but discussion of differences in eyelid structure between the other races is scarce. Most of the literature focuses on distinctions between “double” and “single” eyelids. Other clinical and surgical considerations are the presence of epicanthi and palpebral fissure slant. By understanding racial and ethnic anatomical differences, oculoplastic surgeons will be able to optimize function and aesthetics. Asians may have fuller, thicker-appearing upper eyelids with an absent or relatively lower upper lid (supratarsal) fold, making the distinction between the single and double eyelid (Figs 1, 2). The orbital septum of Asians fuses with the levator palpebrae aponeurosis at variable distances below the superior tarsal border, closer to the eyelid margin than in non-Asians. This hinders aponeurotic fibers from the levator palpebrae superioris from reaching the subcutaneous tissues, prohibiting the creating of a double eyelid crease. The fusion is above the superior tarsal

The inner segment/outer segment junction: what have we learnt so far?

Purpose of review The advancement of optical coherence tomography has improved the resolution of in-vivo images of the retina. This has led to a wealth of novel knowledge regarding the microstructures of the photoreceptor layer and its relationship with visual functions under different pathological diseases. Recent findings Identification of the hyperreflective lines in the photoreceptor layer has been made possible by spectral domain optical coherence tomography. The inner segment/outer segment junction, external limiting membrane, cone outer segment tips, and the retinal pigment epithelium were thought to be the origins of the four hyperreflective lines seen in the photoreceptor layer. Integrity of these lines has been linked with visual functions in various retinopathies, and has been suggested to carry prognostic implications. Recovery of initially interrupted lines has been documented following successful treatment. Summary Identification of these hyperreflective lines may have clinical implications as visual function was found to correlate closely with their integrity. Restoration of these lines may indicate treatment response and potential visual recovery.

Pseudohypopyon following intravitreal triamcinolone acetonide injection.

Objective: To report a case of a pseudohypopyon that developed after intravitreal injection of triamcinolone acetonide for choroidal neovascularization from age-related macular degeneration. Methods: Observational case report. Results: A 62-year-old woman received an intravitreal injection of triamcinolone acetonide for the treatment of a choroidal neovascular membrane that developed as a result of age-related macular degeneration. A layer of yellowish deposits was observed in the anterior chamber 1 day after the injection. The patient denied any pain or reduced vision, and there was no redness noted on examination. The deposits cleared spontaneously on the fourth postoperative day. Conclusions: Pseudohypopyon may develop after intravitreal injection of triamcinolone acetonide. Distinguishing this from a true hypopyon is important because the treatment and prognosis are very different for the two conditions.

Magnetic resonance imaging in the diagnosis of subretinal cysticercosis

PURPOSE To report a case of ocular cysticercosis and associated magnetic resonance imaging (MRI) findings. DESIGN Interventional case report. METHODS A 56-year-old woman from Ecuador presented with decreased vision and an exudative retinal detachment in the left eye. Subretinal cysticercosis was suspected. RESULTS In the left eye, a subretinal cyst evident on fundus examination was investigated with B-scan ultrasonography. Ultrasonography showed a cystic structure, and MRI of the orbit confirmed the suspicion for cysticercosis. Magnetic resonance imaging of the brain also revealed a small parenchymal lesion in the left occipital lobe of the brain. CONCLUSIONS Magnetic resonance imaging is a useful adjunct to B-scan ultrasonography in the diagnosis of ocular cysticercosis. Magnetic resonance imaging is superior to computed tomography in the demonstration of cystic structures in the eye and central nervous system. This finding has important therapeutic implications, as any viable cysticercus in the eye or cerebral parenchyma can be treated surgically or medically, respectively.

Correlation Between Microaneurysms and Retinal Thickness in Diabetic Macular Edema

Purpose: Microaneurysms commonly are believed to be related causally to retinal thickening in diabetic retinopathy, especially by leaking. The hypothesis that thicker areas of retina in diabetic retinopathy have more microaneurysms per unit area than areas that are not as thick was tested. Methods: Retinal thickness analysis was performed with a prototype instrument for 27 eyes of 27 diabetic patients and 22 normal eyes of 22 healthy subjects. Maps of retinal thickness were created, and microaneurysms were counted in zones having four levels of retinal thickness. Results: There was no increase in either total microaneurysms or apparent leaking microaneurysms per unit area with increasing levels of retinal thickness (P = 0.77 and 0.87, respectively). Conclusion: Some microaneurysms may not cause thickening, or other factors may contribute to retinal thickening in diabetic retinopathy. The results may have implications on the pathogenesis of diabetic macular edema.

Minimally Invasive Method for Repair of Rhegmatogenous Retinal Detachment Following Treatment for Retinoblastoma

A minimally invasive method for repair of rhegmatogenous retinal detachment following treatment of retinoblastoma is described. Two children with retinoblastoma developed rhegmatogenous retinal detachments following treatment with a combination of chemotherapy and cryotherapy. Each eye underwent a non-drainage scleral buckling procedure without retinopexy of the retinal break. Postoperatively, the retinas reattached and retinopexy with indirect laser photocoagulation was performed during subsequent examinations under anesthesia. The retinas have remained attached with 2 to 5 years of follow-up. The tumor recurred in case 2, was treated with additional chemotherapy, and has undergone type 1 regression. Non-drainage scleral buckling without retinopexy is a useful technique for repairing rhegmatogenous retinal detachment in eyes with retinoblastoma. The retinal break can be treated postoperatively with indirect laser photocoagulation to minimize the chance of viable tumor cell dissemination.

Chorioretinal Topography and Histopathology in Laser-Induced Choroidal Neovascularization

OBJECTIVE To investigate the correspondence between topographic mapping of the vitreoretinal and chorioretinal surfaces in vivo and histopathology findings. MATERIALS AND METHODS Choroidal neovascularization was induced in the retina of a primate by an argon laser. Serial optical section images of the retina were obtained using an optical imaging system based on the Retinal Thickness Analyzer. Topography of the vitreoretinal and chorioretinal surfaces was mapped. The animal was killed and the eyes enucleated for histopathologic examination. RESULTS In the normal retina, the topography of the vitreoretinal surface showed a depression at the center of the fovea while the chorioretinal surface was relatively flat, corresponding to normal anatomy. In the retina with choroidal neovascularization, the topography of the vitreoretinal surface indicated a smooth elevation while there were irregular elevations in the topography of the chorioretinal surface. Histological sections displayed focal serous retinal detachment, metaplasia of retinal pigment epithelium, and choroidal neovascularization. CONCLUSION Topographic mapping of the vitreoretinal and chorioretinal surfaces in vivo corresponds with histological findings and shows promise for quantitative evaluation of pathologic alterations caused by chorioretinal diseases.

Hemorrhage in patients who have received transpupillary thermotherapy for subfoveal choroidal neovascularization

C horoidal neovascularization (CNV) that develops as a result of age-related macular degeneration (AMD) is a major cause of severe and irreversible vision loss in the Western world. Recently, transpupillary thermotherapy (TIT), in which a diode laser delivers infrared light in the form of heat to the retina, has been used to treat occult subfoveal CNV. 13 It was found to be effective, with no or minimal side effects reported in these case series. In this paper we describe hemorrhages that developed during and after TTT.