Morphology of Emphysema - Robbins

Definition

The acinus is the functional unit distal to the terminal bronchiole, consisting of respiratory bronchioles, alveolar ducts, and alveolar sacs. A cluster of 3-5 acini forms a lobule.

The Four Types

1. Centriacinar (Centrilobular) Emphysema

• Most common type - >95% of clinically significant cases
• Part affected: Central/proximal parts of the acinus - the respiratory bronchioles - are destroyed; distal alveoli are spared
• Result: Both emphysematous AND normal airspaces coexist within the same acinus and lobule
• Distribution: Upper lobes predominate, particularly the apical segments
• Association: Heavy cigarette smokers; commonly accompanied by chronic bronchitis
• In severe cases, the distal acinus is also involved, making distinction from panacinar difficult

2. Panacinar (Panlobular) Emphysema

• Part affected: Acini are uniformly enlarged from the respiratory bronchiole all the way to the terminal blind alveoli - the entire acinus is involved
• Distribution: Lower lung zones and anterior margins; most severe at the lung bases
• Association: Alpha-1 antitrypsin (A1AT) deficiency - present in >80% of A1AT-deficient patients, occurring earlier and more severely if they also smoke. Exacerbated by smoking.
• Grossly: Produces pale, voluminous lungs that may obscure the heart when the chest is opened at autopsy

3. Distal Acinar (Paraseptal) Emphysema

• Part affected: Proximal portion of the acinus is normal; distal part is predominantly involved
• Location: Adjacent to the pleura, along lobular connective tissue septa, at the margins of lobules - often adjacent to areas of fibrosis, scarring, or atelectasis
• Usually more severe in the upper half of the lungs
• Characteristic finding: Multiple enlarged airspaces ranging from <0.5 mm to >2.0 cm in diameter, sometimes forming cyst-like structures - with further enlargement these become bullae
• Clinical significance: Underlies many cases of spontaneous pneumothorax in young adults (rupture of subpleural bullae)

4. Irregular (Paracicatricial) Emphysema

• Part affected: The acinus is irregularly involved - hence the name
• Association: Almost invariably associated with scarring (hence also called paracicatricial)
• Usually occurs in small foci
• Clinically insignificant in most instances

Summary Comparison Table

MORPHOLOGY Box (Robbins Basic Pathology)

• Panacinar emphysema produces pale, voluminous lungs that often obscure the heart at autopsy
• Centriacinar emphysema: lungs are a deeper pink and less voluminous than in panacinar; upper two-thirds more severely affected

• Destruction of alveolar walls without fibrosis - leads to enlarged airspaces
• Reduced number of alveolar capillaries (due to alveolar loss)
• Terminal and respiratory bronchioles may be deformed because septa that normally tether them in the parenchyma are destroyed
• Bronchiolar inflammation and submucosal fibrosis often present in advanced disease

Other Forms (Not COPD-Related)

1. Compensatory hyperinflation - alveolar dilation in response to loss of lung substance elsewhere (e.g., post-lobectomy); not true emphysema
2. Obstructive overinflation - air trapping from subtotal airway obstruction by tumor or foreign body; can be life-threatening
3. Bullous emphysema - large subpleural blebs/bullae (>1 cm diameter); can occur in any form; rupture causes pneumothorax
4. Interstitial emphysema - air enters connective tissue stroma of the lung, mediastinum, or subcutaneous tissue; caused by alveolar tears from transient increases in intra-alveolar pressure (coughing) or chest wounds

Cataract - Clinical Postings Guide

Definition

Lens Anatomy (Relevant to Understanding Cataracts)

• Capsule: Acellular membrane enclosing all lens material
• Epithelial cells: Cuboid, under the anterior capsule; divide continuously in the germinative zone to form new lens fibres
• Nucleus: Central, surrounded by cortex; oldest fibres
• Cortex: Peripheral surrounding the nucleus
• Zonules: Hold the lens in position, attached to the ciliary body

Classification

By Etiology

Age-Related Cataract - By Location

1. Posterior Subcapsular (PSC) Cataract

• Opacity lies just in front of the posterior capsule
• Granular/plaque-like on oblique slit lamp; black and vacuolated on retroillumination (vacuoles = Wedl/bladder cells = swollen migratory lens epithelial cells)
• Profound effect on vision due to location at the nodal point of the eye
• Symptoms: Glare (especially night driving), worse in bright light and near vision (miosis brings opacity into optical axis)
• Also occurs with: steroid use, diabetes, trauma, radiation, uveitis - typically in patients <50 years, more rapid onset

2. Nuclear Sclerotic Cataract

• Exaggeration of normal ageing change in the nucleus
• Yellowish hue (urochrome pigment deposition); when very advanced, brown (brunescent) or rarely black
• Best assessed with oblique slit lamp beam; retroillumination shows subtle nucleus-cortex distinction
• Associated with myopia (increase in refractive index of nucleus) - causes "second sight of the aged" - previously presbyopic elderly patient can read without glasses again
• Hypermetropic shift occurs in the healthy ageing eye

3. Cortical Cataract

• Involves anterior, posterior, or equatorial cortex
• Begins as clefts and vacuoles from cortical hydration
• Classic pattern: cuneiform (wedge-shaped) or radial spoke-like opacities - often starting in the inferonasal quadrant
• Glare is a common symptom; often asymptomatic until central

4. Christmas Tree Cataract

• Uncommon; polychromatic needle-like formations in deep cortex and nucleus
• Associated with myotonic dystrophy

Cataract Maturity Stages

Important: A mature cataract with leaking cortex can cause phacolytic glaucoma (lens proteins block trabecular meshwork).

Secondary (Complicated) Cataract

Cataract in Systemic Disease

Symptoms

• Slowly progressive blurred vision, usually over months-years (one or both eyes)
• Glare - especially bright sunlight or oncoming headlights at night
• Altered colour perception (yellowing/browning with nuclear cataract)
• Monocular diplopia (irregular refraction through opacified lens)
• Second sight - nuclear sclerosis causing myopic shift; patient can read without presbyopic glasses
• Cataract does NOT cause a RAPD (relative afferent pupillary defect) - if RAPD present, look for optic nerve or retinal disease

Clinical Signs

• Opacification or discoloration of the crystalline lens (critical sign)
• Diminished/absent red reflex on ophthalmoscopy or retinoscopy
• Blurred fundal view
• Myopic shift (nuclear sclerosis)
• Reduced visual acuity

Examination at Slit Lamp

• Direct illumination (oblique beam): Best for nuclear sclerosis and cortical opacities
• Retroillumination: Best for PSC (dark shadow against red reflex) and cortical opacities
• Dilated pupil examination is required for full assessment

Workup

1. History: Drug history (steroids, tamsulosin - risk of intraoperative floppy iris syndrome (IFIS)), systemic diseases, trauma, previous ocular disease
2. Visual acuity - distance and near, before and after refraction
3. Slit lamp examination - dilated, both direct and retroillumination
4. Pupil exam (no RAPD in pure cataract)
5. Glare testing - useful when BCVA is 20/30 or better to demonstrate functional impact
6. Fundus examination - to rule out concurrent macular/retinal disease
7. B-scan ultrasound - if fundus not visible (mature cataract) to rule out posterior segment pathology (e.g., retinal detachment, vitreous haemorrhage)
8. Potential Acuity Meter (PAM) / Laser interferometry - estimate visual potential when posterior segment disease coexists
9. Preoperative biometry - to calculate IOL power (keratometry + axial length measurement)

Treatment

Non-surgical (temporising)

• Correct refractive error (spectacles/contact lenses)
• Trial of mydriasis (cyclopentolate 1% BD-TDS) - useful mainly for PSC cataracts (dilated pupil moves opacity out of axis); only temporary benefit

Surgical - Indications

1. To improve visual function - symptomatic visual disability that affects quality of life
2. As surgical therapy - lens-related glaucoma (phacolytic, phacomorphic), lens-induced uveitis
3. To facilitate management - improve fundal view for monitoring/treating diabetic retinopathy or glaucoma

Surgical Techniques

Phacoemulsification (standard in high-income countries)

• Ultrasound probe fragments and aspirates the lens nucleus through a small self-sealing incision (2.2-2.8 mm)
• Followed by cortex aspiration and foldable IOL implantation into the capsular bag
• No sutures needed; fast visual recovery; low astigmatism induction

Manual Small-Incision Cataract Surgery (MSICS)

• Variant of ECCE for high-volume settings (e.g., India)
• Self-sealing sclero-corneal tunnel; nucleus expressed manually; comparable outcomes to phaco but faster and cheaper

Extracapsular Cataract Extraction (ECCE)

• Large limbal incision (8-10 mm), nucleus expressed after capsulotomy, cortex aspirated
• Requires sutures; now used mainly when phaco not feasible (dense brunescent cataract, no phaco machine)

Intracapsular Cataract Extraction (ICCE)

• Cryoprobe removes entire lens including capsule
• Largely abandoned; no capsular bag for posterior chamber IOL support

Anaesthesia Options

Complications of Cataract Surgery

Intraoperative

• Posterior capsular rupture + vitreous loss (~1% experienced surgeons, higher for trainees)
• Zonular dehiscence
• Dropped nucleus (~0.2%)

Postoperative - Common/Mild

• IOP spike
• Iridocyclitis
• Periocular ecchymosis
• Posterior capsular opacification (PCO) - commonest late complication

Postoperative - Serious

• Endophthalmitis (0.1%) - most feared; presents with pain, reduced vision, hypopyon
• Cystoid macular oedema (CMO)
• Retinal detachment (<1%)
• Corneal decompensation
• IOL dislocation
• Unexpected refractive outcome
• Suprachoroidal haemorrhage (0.04%) - rare but devastating

Posterior Capsular Opacification (PCO) - "After-Cataract"

• Most common late complication of cataract surgery
• Residual lens epithelial cells proliferate on the posterior capsule
• Presents with gradual deterioration of vision weeks-months-years post-op
• Treatment: Nd:YAG laser posterior capsulotomy - creates a central clear opening; safe, outpatient procedure

Key Clinical Points for Postings

1. Cataract alone does NOT cause RAPD - always investigate if RAPD present
2. Glaukomflecken = PSC opacities in the pupillary zone = pathognomonic of previous acute angle closure
3. Second sight of the aged = nuclear sclerosis inducing myopia; presbyopic patient temporarily reads without glasses
4. Morgagnian cataract = nucleus sinks in liquefied cortex - the classic hypermature cataract
5. PSC most visually disabling per unit size - at nodal point; worst with miosis (near work, bright light)
6. Tamsulosin (alpha-1 blocker) use must be flagged pre-op - causes intraoperative floppy iris syndrome (IFIS)
7. Diabetes - check and monitor for diabetic macular oedema before and after surgery (oedema can worsen post-op)
8. B-scan US mandatory before operating on a white mature cataract - rule out retinal detachment
9. Biometry (IOL power calculation) requires keratometry + axial length measurement