Posterior segment

11 Posterior segment


Retina (Figure 11-3)

Neurosensory Retina (9 Layers)

Inner refers to proximal or vitreous side of retina


Monolayer of hexagonal cells with apical microvilli and basement membrane at base

RPE and outer segments of photoreceptors have apex-to-apex arrangement, resulting in a potential subretinal space

Merges anteriorly with pigmented epithelium of ciliary body


RPE cells may undergo hypertrophy, hyperplasia, migration, atrophy, and metaplasia


Posterior part of uveal tract that extends from ora serrata (outer layers end before inner) to optic nerve. Attached to sclera by strands of connective tissue at optic nerve, scleral spur, vortex veins, and long and short posterior ciliary vessels; derived from mesoderm and neuroectoderm; 0.22 mm thick posteriorly and 0.1–0.15 mm thick anteriorly



Electroretinogram (ERG)

Measures mass retinal response; useful for processes affecting large areas of retina

Photoreceptors, bipolar and Müller’s cells contribute to flash ERG; ganglion cells do not

Light is delivered uniformly to entire retina, and electrical discharges are measured with a corneal contact lens electrode

Components (Figure 11-10)

Early receptor potential (ERP) (Figure 11-11): outer segments of photoreceptors; completed within 1.5 ms

Disease states (Figure 11-14, Table 11-2)

Table 11-2 ERG patterns for various ocular diseases

Extinguished ERG abnormal photopic, normal ERG Normal a-wave, reduced b-wave Abnormal photopic, normal scotopic ERG
RP CSNB; Oguchi’s disease Achromotopsia
Ophthalmic artery occlusion X-linked juvenile retinoschisis Cone dystrophy
Metallosis CRAO  
RD Myotonic dystrophy  
Drug toxicity (phenothiazine; chloroquine) Quinine toxicity  
Cancer-associated retinopathy    

Electro-oculogram (EOG)

Indirect measure of standing potential of eye (voltage difference between inner and outer retina) (Figure 11-16)

Depolarization of basal portion of RPE produces light peak; normal result requires that both RPE and sensory retina be normal

Retinal Imaging

Optical Coherence Tomography (OCT)

Creates cross-sectional image of tissue using light

Provides retinal thickness measurements and cross-sectional retinal imaging to ∼5–10 µm depending on light source; anterior segment spectral domain OCT is useful to image anterior segment, in particular the cornea and angle

Superluminescent diode fires beam of infrared light through fiberoptic Michelson interferometer at both the eye and a reference mirror; the reflected light from the retina is compared with the light from the reference mirror and analyzed so that the tissue reflectivity (similar to ultrasound) and density can be determined. With time-domain OCT (TDOCT), the reference mirror moves; with spectral-domain OCT (SDOCT) the mirror does not move and a Fourier transform is used to obtain imaging information (this makes SDOCT much faster than TDOCT)

Useful for optic nerve (glaucoma) and macular pathology (edema, hole, pucker); can compare thickness in cases of macular edema from one visit to next; can diagnose and differentiate vitreomacular pathology e.g. stage 1 macular hole vs full-thickness hole (≥stage 2) vs pseudohole or lamellar holes (Figures 11-17, 11-18)


Acoustic imaging of globe and orbit

Specific lesions

(Tables 11-3 and 11-4) (Figures 11-22 to 11-27)

Fluorescein Angiogram (FA)


choroidal filling, arterial, venous, recirculation


Vitreous Abnormalities

Jun 4, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Posterior segment

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