• Clinical science

Diseases of the retina

Summary

The retina, which contains the first three neurons of the visual pathway, mediates the conversion of light stimuli into nerve impulses. Diseases of the retina may lead to visual impairment, visual field loss, and more complex disorders such as metamorphopsia (distorted vision) and clouding. Ophthalmoscopy is the preferred diagnostic method for identifying retinal diseases, but depending on the suspected disorder, other methods such as fluorescein angiography and optical coherence tomography (OCT) may be appropriate.

Color perception disorders

  • Color blindness or dyschromatopsia: altered color perception; congenital or acquired (e.g., optic neuritis)
    • Congenital; color perception disorders (especially red-green color vision deficiency; ) are very common and occur mostly in men.
    • Affected individuals are generally unaware of their own color-perception disorders.
    • Dichromacy: Only two of the three types of cones in the retina are fully functional.
      • Types
        • Deuteranomaly: green color deficiency (very common: ∼ 5% of the male population)
        • Deuteranopia: green color blindness (∼ 1% of the male population)
        • Protanomaly: red color deficiency (∼ 1% of the male population)
        • Protanopia: red color blindness (∼ 1% of the male population)
        • Tritanomaly: blue-yellow color weakness (very rare)
        • Tritanopia: blue-yellow color blindness (very rare)
      • Clinical features: difficulties distinguishing colors from one another
      • Diagnosis
        • Ishihara color test: set of color-dotted plates used to diagnose deuteranopia and protanopia
        • Anomaloscope: instrument used to diagnose quantitative and qualitative defects in color perception
  • Achromatism: complete color blindness (very rare)

References:[1][2][3]

Degenerative diseases of the retina

Central serous retinopathy (central serous chorioretinopathy)

  • Definition: serous retinal detachment at the posterior pole of the eyeball (at the macula or in the perimacular region) due to a defect in the pigment epithelium
  • Pathophysiology: defect in the area of Bruch's membrane/pigment epithelium → fluid leakage from the sclera into the subretinal space → serous retinal detachment
  • Etiology
    • Unknown
    • Glucocorticoids and an increase in the diastolic blood pressure are possible risk factors.
    • Stress-related
  • Epidemiology
    • Mostly affects men 20–45 years of age
  • Clinical features
    • Hyperopia
    • Metamorphopsia (distorted vision)
    • Patients perceive images as smaller than they are
    • Relative scotoma (perception of a gray area or shadow in the central field of vision)
  • Diagnostics
    • Ophthalmoscopy: roundish detachment of the central retina
    • Fluorescein angiography: an imaging procedure in which fluorescent dye (fluorescein) is injected intravenously in order to highlight retinal vessels, which are then photographed.
    • Optical coherence tomography (OCT)
  • Treatment
    • Often heals spontaneously
    • Stress reduction
    • Rarely: laser coagulation (in extramacular localization), photodynamic therapy

Macular hole

  • Definition: central small break in the macula
  • Etiology
  • Clinical features (stage-related)
  • Treatment: vitrectomy with removal of epiretinal membranes and the internal limiting membrane of the retina

Age-related macular degeneration

See age-related macular degeneration.

Retinal detachment

See retinal detachment.

References:[4]

Dystrophic retinal diseases

Retinitis pigmentosa

  • Definition: progressive hereditary dystrophy of the retina or of the photoreceptors and the retinal pigment epithelium
  • Epidemiology: early onset (5–30 years)
  • Etiology
    • Hereditary or spontaneous mutations (> 45 genes are known as triggers; e.g., mutations in the rhodopsin gene)
  • Clinical features
    • Night blindness
    • Narrowing field of vision (ring-shaped area of blindness)
    • Glare sensitivity
    • Defects in the perception of contrast and color
    • In early stages: good central vision
    • In advanced stages: impaired vision
  • Diagnostics
    • Ophthalmoscopy
      • Pattern of dark spots and star-shaped blotches that develop from the periphery to the center of the retina
    • Perimetry
    • Electroretinography
  • Differential diagnosis: Drugs (phenothiazines, chloroquine) may induce similar symptoms to those of retinitis pigmentosapseudoretinitis pigmentosa
  • Treatment: No effective treatment is known.
  • Prognosis: often leads to blindness

Best disease (vitelliform macular dystrophy)

  • Definition: juvenile macular dystrophy, autosomal dominant inheritance
  • Clinical features
    • Chronic progressive visual impairment; onset typically between 4–10 years
    • People often have vision of approx. 20/40
  • Diagnostics
    • Ophthalmoscopy: typical, yellowish, round yolk-like lesions (from Latin “vitellus” = yolk) in the region of the macula
    • Electrooculography (EOG): pathological
    • Electroretinogram (ERG): normal
  • Treatment: No causal therapy is known.
  • Prognosis: Some patients may not have visual deterioration beyond 20/40. However, the deterioration may progress after age 40.

Vascular diseases of the retina

Disorders covered in other LCs

Retinopathy of prematurity (ROP)

  • Definition: disease of the retina with abnormal vessel proliferations that affects preterm infants
  • Pathophysiology
    • Elevated and fluctuating partial pressures of oxygen → pathological extraretinal neovascularization → hemorrhages, formation of fibrovascular membranes, and, in severe cases, retinal detachment.
  • Risk factors
  • Diagnostics: screening of all premature babies that are at risk for developing ROP
    • Indications
    • Timing of examinations
      • First examination 6 weeks postnatally (in cases of prematurity, screening starts at the 30th week of gestation)
      • Follow-up depending upon findings or state of the ocular fundus
    • The examination of the ocular fundus assesses the following:
      • Vascularization of the peripheral retina
      • Demarcation line between vascularized and nonvascularized retina
      • Extraretinal vessel formations
      • Formation of membranes and distortion/detachment of the retina
      • Plus disease: increased tortuosity, exudation, hemorrhage
    • Discontinuation of follow-up screening
      • After complete vascularization of the peripheral retina
      • Significant decrease in alterations of the peripheral retina (however, only after the expected date of delivery)
  • Treatment
    • In early stages of the disease: no treatment, but regular follow-up
    • In advanced stages: laser coagulation therapy may be indicated
    • In onset of retinal detachment: vitrectomy may be indicated
  • Complications
  • Prevention
    • Monitoring oxygen pressures
    • Regular fundoscopic exams to prevent delays in necessary treatments

Other retinal disorders

Tumors of the retina

Differential diagnosis of leukocoria