Background: A variety of experimental animal models are used in basic ophthalmological research to elucidate physiological mechanisms of vision and disease pathogenesis. The choice of animal model is based on the measurability of specific parameters or structures, the applicability of clinical measurement technologies, and the similarity to human eye function. Studies of eye pathology usually compare optical parameters between a healthy and altered state, so accurate baseline assessments are critical, but few reports have comprehensively examined the normal anatomical structures and physiological functions in these models.

Methods: Three cynomolgus monkeys, six New Zealand rabbits, ten Sprague Dawley (SD) rats, and BALB/c mice were examined by fundus photography (FP), fundus fluorescein angiography (FFA), and optical coherence tomography (OCT).

Results: Most retinal structures of cynomolgus monkey were anatomically similar to the corresponding human structures as revealed by FP, FFA, and OCT. New Zealand rabbits have large eyeballs, but they have large optic disc and myelinated retinal nerve fibers in their retinas, and the growth pattern of retinal vessels were also different to the human retinas. Unlike monkeys and rabbits, the retinal vessels of SD rats and BALB/c mice were widely distributed and clear. The OCT performance of them were similar with human beings except the macular.

Conclusions: Monkey is a good model to study changes in retinal structure associated with fundus disease, rabbits are not suitable for studies on retinal vessel diseases and optic nerve diseases, and rats and mice are good models for retinal vascular diseases. These measures will help guide the choice of model and measurement technology and reduce the number of experimental animals required.

Abstract: Optical coherence tomography (OCT) is a widely used non-invasive medical imaging technology that has revolutionized clinical care in ophthalmology. New developments, such as OCT angiography (OCTA) are expected to contribute even further to the widespread use of OCT-based imaging devices in the diagnosis and monitoring of patients with ophthalmic diseases. In recent years, many of the disadvantages such as limited field of view and imaging artefacts have been substantially reduced. Similar to the progress achieved in the assessment of retinal disorders, OCT is expected to change the approach to patients seen in the neuro-ophthalmology clinic. In this article, we review the technical features of OCT and OCT-based imaging techniques, highlighting the specific factors that should be taken into account when interpreting OCT in the field of neuro-ophthalmology.

Background: Sodium iodate (SI) is a chemical widely applied to induce retina degeneration in animal models. SI treatment caused formation of rosettes/folds in the outer nuclear layer (ONL) of the rat retina, but it was previously unclear whether SI also forms rosettes in mice. In addition, SI induced retina degeneration was never addressed in non-separate sclerochoroid/retina pigment epithelium/retina whole mount. Here we displayed features of retina degeneration including rosette formation in mice and developed a morphological analytic assessment using sclerochoroid/retina pigment epithelium/retina whole mounts.

Methods: SI was intraperitoneally injected in Sprague-Dawley (SD) rats and C57BL/6J mice using a single dose (50 mg/kg) or with a dose range (10 to 50 mg/kg) in BALB/C mice. Rat retinas were investigated up to 2-week post-injection by histology and whole mounts, and mouse retinas were investigated up to 3-week post-injection by histology, fluorescent staining of sections and/or sclerochoroid/retina pigment epithelium/retina whole mounts for the morphological evaluations of the SI-induced retina damage.

Results: SI-induced retina damage caused photoreceptor (PR) degeneration and rosettes/folds formation, as well as retina pigment epithelium degeneration and inward migration. It displayed mixed nuclei from choroid to PRs, due to layer disorganization, as shown by single horizontal images in the sclerochoroid/retina pigment epithelium/retina whole mounts. Measurement of the PR rosette area induced by SI provided a quantitative, morphological evaluation of retina degeneration.

Conclusions: The method of non-separate sclerochoroid/retina pigment epithelium/retina whole staining and mount allows us to observe the integral horizontal view of damage from sclera to PR layers, which cannot be addressed by using sectioned and separate whole mount methods. This method is applicable for morphological evaluation of retina damage, especially in the subretinal layer.

Background: Bacillary layer detachment (BALAD) is a phenomenon characterized by fluid accumulation at the myoid region of the inner photoreceptor segments identifiable on optical coherence tomography (OCT) imaging. This finding has been recently described in patients with diverse primary diagnoses which share the common feature of serous exudation in the posterior pole. However, thus far there have been very few reports in the literature of BALAD in patients with posterior scleritis.

Case Description: A 16-year-old male presented with unilateral vision changes that acutely worsened overnight to significant unilateral vision loss. He was eventually diagnosed with idiopathic posterior scleritis with associated BALAD on OCT. Similar to other reported cases of BALAD, he experienced anatomic restoration of the outer retina followed by good visual recovery after treatment with high dose steroid, ultimately with complete recovery of both retinal anatomy and vision within 4 months.

Conclusions: This case provides further evidence that posterior scleritis can be a cause of BALAD. The rapid presentation and excellent visual and anatomical outcome of this case is entirely consistent with known descriptions of BALAD in a variety of other conditions, further supporting the categorization of BALAD as an entity which retinal specialists should be able to recognize as distinct from other forms of intraretinal fluid, retinal detachment, and retinoschisis.

Background: Bacillary layer detachment (BALAD) is a phenomenon characterized by fluid accumulation at the myoid region of the inner photoreceptor segments identifiable on optical coherence tomography (OCT) imaging. This finding has been recently described in patients with diverse primary diagnoses which share the common feature of serous exudation in the posterior pole. However, thus far there have been very few reports in the literature of BALAD in patients with posterior scleritis.

Case Description: A 16-year-old male presented with unilateral vision changes that acutely worsened overnight to significant unilateral vision loss. He was eventually diagnosed with idiopathic posterior scleritis with associated BALAD on OCT. Similar to other reported cases of BALAD, he experienced anatomic restoration of the outer retina followed by good visual recovery after treatment with high dose steroid, ultimately with complete recovery of both retinal anatomy and vision within 4 months.

Conclusions: This case provides further evidence that posterior scleritis can be a cause of BALAD. The rapid presentation and excellent visual and anatomical outcome of this case is entirely consistent with known descriptions of BALAD in a variety of other conditions, further supporting the categorization of BALAD as an entity which retinal specialists should be able to recognize as distinct from other forms of intraretinal fluid, retinal detachment, and retinoschisis.