Hi, I am Dr Thomas Whitelaw, welcome back to Espisode 64 of Basic Sciences in Ophthalmology.In Episode 64, we're exploring a fascinating and clinically important area of ophthalmology: the anatomy of orbital trauma.

The orbit is much more than a bony cavity containing the eye.

It is a complex anatomical structure containing the globe, extraocularmuscles, nerves, blood vessels, orbital fat and connective tissues.

Its walls provide protection, but their thickness and anatomicalrelationships also create areas of vulnerability.

When the orbit is injured, understanding these relationships becomesessential.

A fracture of the orbital floor can trap an extraocular muscle and producedouble vision.

An infection spreading from the paranasal sinuses can involve the orbitaltissues and threaten sight.

And modern imaging allows us to investigate structures that cannot beassessed adequately through clinical examination alone.

Today, we'll examine three interconnected subjects:

First: blowout fractures.

Second: orbital cellulitis.

And third: imaging in trauma.

Hi I am Dr Thomas Whitelaw, welcome back to Basic Sciences in Ophthalmology.

In Episode 63, we're exploring one of the most mechanically fascinating regions of the eye: the vitreoretinal interface.

The vitreous is often thought of simply as the transparent gel filling the posterior segment. But the relationship between the posterior vitreous cortex and the retinal surface is dynamic. It changes with age, and the way in which the vitreous separates—or fails to separate—from the retina can have major consequences for vision.

At the macula, persistent attachment can generate vitreomacular traction.

Cellular proliferation on the retinal surface can produce an epiretinal membrane.

And with ageing, liquefaction and collapse of the vitreous can eventually produce a posterior vitreous detachment, or PVD.

These are not completely separate processes. The uploaded Yanoff text describes vitreomacular traction, epiretinal membrane and several other macular disorders as part of a spectrum related to variations in anomalous posterior vitreous detachment.

So today we'll examine three interconnected processes:

First: vitreomacular traction.

Second: epiretinal membranes.

And third: posterior vitreous detachment.

Hi, I’m Dr Thomas Whitelaw and welcome back to Basic Sciences inOphthalmology.

In Episode 62, we're taking a closer look at an important adverse effect ofone of the most widely used groups of drugs in medicine and ophthalmology: corticosteroids.

Steroids are powerful anti-inflammatory agents. In ophthalmology, they areinvaluable in controlling ocular inflammation.

But in susceptible individuals they can also cause a significant rise in intraocularpressure, or IOP.

If that pressure elevation is sufficiently prolonged or severe, it can contribute to characteristic glaucomatous optic nerve damage.

This is steroid-induced glaucoma.

Today's episode is divided into three sections:

First: the mechanism of steroid-induced IOP rise.

Second: risk factors.

And third: management strategies.

Everything in this episode is based exclusively on the ophthalmologytextbooks supplied for this podcast project.

Hi, I am Dr Thomas Whitelaw and welcome back ‘Basic Sciences in Ophthalmology ‘ in Episode 61, we're looking at an important connection between general medicine, pharmacology and ophthalmology: the effects of systemic and locally administered drugs on vision.

A medicine prescribed to treat disease elsewhere in the body can sometimes have significant ocular consequences.

Some drugs damage the retina.

Some alter aqueous humour outflow and increase intraocular pressure.

And others interfere with the metabolism of the optic nerve.

For the ophthalmology trainee, three particularly important examples are chloroquine and hydroxychloroquine, corticosteroids, and ethambutol.

These drugs affect three different parts of the visual system and illustrate three very different mechanisms of toxicity.

Today's episode is therefore divided into three sections:

First: antimalarials and retinopathy.

Second: steroids and glaucoma.

And third: ethambutol and optic neuropathy.

Everything in this episode is based exclusively on the ophthalmology texts supplied for this podcast project.

Welcome back to Basic Sciences in Ophthalmology.

Hi, I am Dr Thomas Whitelaw and in today's episode, we're looking at an area that can initially feel quite different from anatomy, physiology and optics, but which is essential for anyone trying to understand modern ophthalmic evidence: biostatistics.

Episode 59 - Statistical Bias in Ophthalmic ResearchWelcome back to Basic Sciences in Ophthalmology.

Hi, I am Dr Thomas Whitelaw and in today's episode, we're moving away from the anatomy, physiology and optics of the eye and into another fundamental part of ophthalmic science: how we decide whether research evidence can be trusted.

Imagine reading a study reporting that a particular treatment dramatically reduces intraocular pressure, slows visual-field loss or improves visual acuity.

The statistics are significant.

The graphs look impressive.

And the conclusion appears convincing.

But there is a fundamental question we need to ask before accepting those findings:

Could bias have influenced the result?

Bias is particularly important because it is not simply random variation. It can systematically push a study towards a particular conclusion.

And even a beautifully calculated P value cannot rescue a study whose design has introduced serious bias.

The uploaded ophthalmology texts specifically discuss several important forms of bias, including selection bias, information bias, recall bias, confirmation bias, attrition bias, detection bias, lead-time bias and publication bias.

So today we'll look at three areas:

First: types of bias.

Second: designing unbiased studies.

And third: the impact of bias on study results.

Episode 58 - Polarization and Optical Devices

Welcome back to Basic Sciences in Ophthalmology.

Hi, I am Dr Thomas Whitelaw and in Episode 58, we're exploring a property of light that our visual system itself is remarkably poor at detecting, yet which can be extremely useful when incorporated into optical instruments: polarization.

Polarization arises from the orientation of the electric field within a light wave. By selectively transmitting particular orientations of that field, optical filters can suppress unwanted reflections, separate images and reveal information about materials that alter the polarization state of light.

In ophthalmology, these principles extend from relatively simple polarizing filters to sophisticated techniques such as scanning laser polarimetry, where the birefringence of retinal nerve fibres can be exploited to estimate the thickness of the retinal nerve fibre layer.

Today's episode is divided into three sections:

First: polarization filters in imaging.

Second: clinical polarimetry.

And third: applications in nerve fibre analysis.

Episode 57 - Neurotransmitters in Visual Processing

Hi, I'm Dr Thomas Whitelaw, welcome back to Basic Sciences in Ophthalmology.

In today’s episode, we’re moving from the optics of image formation into the neural language used by the retina itself.

Before an image ever reaches the optic nerve, the retinahas already performed an extraordinary amount of processing. Light is captured by photoreceptors, converted into an electrical signal, passed through several layers of retinal neurons and modified by lateral connections before ganglion cells finally transmit the processed information towards the brain.

At the centre of this process are neurotransmitters:chemical messengers that allow retinal neurons to communicate across synapses.

Today's episode is divided into three sections:

First: neurotransmitters in the retina.

Second: signal modulation.

And third: synaptic pathways.