Patología de la retina Dra. Valeria Cortés: Inducción estudiantes X semestre

Introduction to Retina Pathology

Overview of Retina Pathology

• The session is introduced by Valeria Cortés Castillo, a third-year resident from Pontificia Universidad Javeriana C de Cali.

• Retina pathology encompasses a wide range of diseases and alterations, including those stemming from systemic illnesses that affect the retina.

Key Focus Areas

• Three main topics are selected for discussion in clinical practice: retinal detachment, embryology of the eye, and its implications on retinal health.

Embryological Development of the Eye

Origin and Structure

• The eye shares an embryological origin with the brain, developing from the prosencephalon into optic vesicles that form the optic cup.

• The optic cup consists of two layers: an outer layer (epithelial pigment layer) and an inner layer (neural retina), which develop into distinct structures.

Importance of Layers

• The outer layer gives rise to the retinal pigment epithelium (RPE), while the inner layer forms neural retina containing various cell types essential for vision.

Retinal Anatomy and Function

Histological Structure

• A histological cross-section shows RPE connected to choroid; this connection is crucial for nutrient supply and waste removal.

• Various layers within the neural retina include photoreceptors, bipolar cells, ganglion cells, and their synaptic connections.

Visual Signal Processing

• Light stimuli must be converted into biochemical signals through phototransduction occurring in photoreceptors after light absorption by RPE.

Consequences of Retinal Detachment

Definition and Mechanism

• Retinal detachment is defined as separation between neurosensory retina and RPE due to physiological forces being disrupted.

Impact on Vision

Understanding Retinal Detachment

Types of Retinal Detachment

• The classification of retinal detachment is divided into three types: rhegmatogenous, tractional, and exudative.

• Rhegmatogenous detachment often begins with posterior vitreous detachment, a physiological process that typically occurs around the age of 50-52 years.

• As we age, the vitreous gel becomes less consistent and more liquid-like, leading to potential separation from the retina.

Mechanisms Behind Rhegmatogenous Detachment

• In approximately 15% of patients experiencing vitreous detachment, there may be ruptures or tears in the retina due to traction forces.

• A tear (regma in Latin means "tear" or "hole") allows fluid to enter subretinal space, separating the retinal pigment epithelium (RPE) from the neural retina.

Treatment Approaches for Tears

• If a tear is identified before full detachment occurs, laser treatment can be applied to seal it and prevent further fluid entry.

• Laser therapy involves creating points around the tear to effectively "weld" it back together and maintain retinal integrity.

Tractional Retinal Detachment

• Tractional retinal detachment is commonly seen in poorly controlled diabetic patients with proliferative diabetic retinopathy; fibrotic bands pull on the retina without causing tears.

• This type of detachment can lead to rhegmatogenous detachment if not managed properly due to ongoing traction forces.

Exudative Retinal Detachments

• Exudative detachments occur without any tears or holes but result from fluid accumulation beneath the retina due to various pathologies affecting RPE function.

Understanding Retinal Detachment and Its Symptoms

Mechanism of Retinal Detachment

• The exudation in the retina can lead to detachment due to inflammatory processes like scleritis, especially when there are no ruptures.

• Position changes can affect the detachment; for instance, lying down may cause the detachment to shift and potentially worsen.

Symptoms Indicating Retinal Issues

• Patients often report symptoms such as myodesopsias (floaters), particularly noticeable against uniform backgrounds like a clear sky or white wall.

• New or increased floaters can signal retinal issues; patients should be cautious if they notice a sudden change in their visual disturbances.

Visual Disturbances and Their Implications

• Photopsias (flashes of light) may occur due to vitreous traction on the retina, indicating potential retinal tears or detachments.

• Patients experiencing persistent flashes should be referred to an ophthalmologist for evaluation of possible retinal damage.

Urgent Signs and Referral Protocol

• If patients describe seeing a "curtain" effect in their vision, it suggests something is occupying the vitreous cavity, warranting immediate attention.

• Metamorphopsia (distorted vision), where straight lines appear wavy, indicates possible macular issues rather than just retinal detachment.

Treatment Approaches for Retinal Conditions

• Initial treatment for at-risk patients involves laser therapy to prevent further detachment by sealing any existing tears.

Diabetes and Its Impact on Vision

Understanding Diabetes Types

• Diabetes Type 1 is characterized by the destruction of pancreatic beta cells, leading to insulin deficiency, primarily affecting younger patients.

• Diabetes Type 2 involves insulin resistance and typically occurs in older adults. The classification of diabetes is broader but focuses on these two main types for this discussion.

Diabetic Retinopathy Statistics

• Diabetic retinopathy is the leading cause of irreversible vision loss in industrialized countries, with a higher incidence in Type 1 diabetes due to prolonged exposure to elevated blood glucose levels.

• In the U.S., diabetic retinopathy accounts for 6% of blindness cases, with projections estimating 161 million people affected globally by 2045.

Ophthalmological Follow-Up Guidelines

• For patients diagnosed with Type 1 diabetes, an ophthalmological follow-up should occur five years post-diagnosis; early detection is crucial as changes begin to manifest at this time.

• Patients diagnosed with Type 2 diabetes should have their first eye examination immediately upon diagnosis due to unknown duration of high glucose exposure. Annual follow-ups are recommended thereafter.

Vascular Complications from Diabetes

• Diabetes causes both microvascular and macrovascular complications, including retinal damage that can lead to severe outcomes like amputations due to vascular permeability alterations.

• Pericytes, which help maintain vascular stability in the retina, die off in diabetes, resulting in increased vessel permeability and potential leakage or hemorrhage.

Progression of Diabetic Retinopathy

• The weakening of vascular walls leads to insufficient blood flow and oxygenation within the retina, causing ischemic events that present as cotton wool spots.

• Proliferative diabetic retinopathy arises from chronic hypoxia prompting neovascularization; however, these new vessels are abnormal and prone to rupture.

Classification of Diabetic Retinopathy

• Diabetic retinopathy is classified into non-proliferative (no new vessels formed) and proliferative (new vessels present), each presenting distinct vascular changes.

Retinopathy and Its Classification

Understanding Microaneurysms and Hemorrhages

• Microaneurysms are small bulges in blood vessels, leading to point hemorrhages around the vessels. These can be deeper within the nerve fiber layer.

• Exudates appear due to vascular permeability alterations, resulting in venous dilation, which is referred to as "arrosareamiento venoso."

Classification of Diabetic Retinopathy

• Diabetic retinopathy can be classified into non-proliferative (mild, moderate, severe) and proliferative stages based on specific criteria such as intraretinal hemorrhages and microaneurysms.

• Severe non-proliferative diabetic retinopathy includes significant intraretinal hemorrhages across quadrants or defined venous changes.

Proliferative Diabetic Retinopathy Mechanisms

• Ischemia in the retina leads to a lack of oxygen, prompting the release of Vascular Endothelial Growth Factor (VEGF), stimulating abnormal vessel growth.

• Neovascularization occurs with unhealthy, tortuous vessels growing towards the vitreous body, potentially leading to complications like fibrous tissue formation.

Clinical Presentation and Urgent Care

• Patients may present with sudden vision loss; it’s crucial to consider vitreous hemorrhage in diabetic patients experiencing acute visual changes.

• The absence of a red reflex during examination may indicate underlying issues such as bleeding within the vitreous cavity.

Treatment Approaches for Diabetic Retinopathy

• Glycemic control is paramount; without managing blood sugar levels effectively, other treatments will not prevent progression of diabetic retinopathy.

• Laser treatment targets areas of non-perfusion to prevent further neovascularization by sealing off ischemic regions.

Advanced Interventions for Complications

• In cases with significant macular edema or compromised retina, anti-VEGF injections may be administered alongside laser therapy.

• For proliferative diabetic retinopathy complications like vitreous hemorrhage or retinal detachment, surgical interventions such as vitrectomy may be necessary.

Hypertensive Retinopathy Overview

Retinopathy and Hypertension: Understanding the Connection

Overview of Hypertensive Retinopathy

• Hypertensive retinopathy can accelerate other eye conditions such as diabetic retinopathy and glaucoma, leading to reduced oxygen circulation and ischemia.

• The pathophysiology involves multiple simultaneous phases, including vasoconstriction, sclerosis (hardening of blood vessels), and exudative phases affecting vascular permeability.

Phases of Retinopathy

• Initial phase includes vasoconstriction where blood vessels become tighter; this is followed by sclerosis causing arteriovenous crossings and narrowing of veins.

• Clinical diagnosis occurs through fundoscopic examination; patients may be unaware of their hypertension until detected during eye checks.

Classification of Hypertensive Retinopathy

• Mild hypertensive retinopathy shows generalized or focal arterial narrowing, arteriovenous crossings, and opacities in the arteriolar wall.

• In images, arteries appear thinner and less red compared to normal veins; these changes are indicative of early-stage hypertensive retinopathy.

Advanced Stages and Complications

• Moderate stages present with hemorrhages (spot-like), microaneurysms, cotton wool spots, or hard exudates visible in the retina.

• Malignant hypertension leads to optic disc edema characterized by blurred margins; untreated hypertension can result in severe complications like retinal artery occlusions.

Importance of Monitoring Blood Pressure

• Regular monitoring is crucial for patients with hypertension to prevent vision loss from complications associated with uncontrolled blood pressure.