1. Grading of Nuclear Cataract

Types of Age-Related Cataract (Kanski's Clinical Ophthalmology)

Grading by Maturity

LOCS (Lens Opacities Classification System)

• Nuclear color (NC): 1-6 scale (clear → amber/brunescent)
• Nuclear opalescence (NO): 1-6 scale (clear → very dense)

• Grade 1+ - Slight nuclear yellowing, trace opalescence
• Grade 2+ - Mild yellow-brown discoloration
• Grade 3+ - Moderate brown nucleus (brunescent)
• Grade 4+ - Dense brown-black nucleus (very hard; highest phacoemulsification energy required)

- Kanski's Clinical Ophthalmology: A Systematic Approach, 10th ed.

2. Lid Anatomy

Laminar Structure

Surface Anatomy

• Normal horizontal palpebral fissure: 28-30 mm
• Normal vertical palpebral fissure: 9-10 mm
• Intercanthal distance: 25-30 mm
• Upper lid margin: midway between superior limbus and pupil
• Lower lid margin: abuts inferior corneal limbus
• Upper lid crease: 10-12 mm above lid margin in women; 7-8 mm in men
• The lateral canthal angle is more acute and ~2 mm higher than the rounded medial canthal angle

Anterior Lamella

Orbital Septum

• In whites: fuses with levator aponeurosis ~3 mm above superior tarsal border
• In Asians: fuses further inferiorly (below superior tarsal border), allowing orbital fat to lie anterior to tarsus - prevents upper eyelid crease formation

Fat Pads

• Upper eyelid: Medial and central fat pads + lacrimal gland laterally (pink, firm - must be preserved to avoid dry eye)
• Lower eyelid: Three fat pads - medial, central, lateral. Medial and central separated by the inferior oblique muscle (must be identified to prevent diplopia)

Posterior Lamella - Eyelid Retractors

• Levator palpebrae superioris (CN III): Originates from lesser wing of sphenoid at orbital apex. Horizontal muscle (36 mm) transitions at Whitnall's ligament to become aponeurosis (14-20 mm), inserting into upper third of tarsal plate and skin (forming the lid crease).
• Muller's (superior tarsal) muscle: Arises from undersurface of levator aponeurosis below Whitnall's ligament, attaches to superior tarsal plate. Sympathetically innervated. Produces 2-3 mm of lid retraction (loss causes ptosis in Horner syndrome).

• Capsulopalpebral fascia: Originates from inferior rectus fascia, inserts on inferior tarsal border. Mimics inferior rectus movement.
• Inferior tarsal muscle: Sympathetically innervated; arises from capsulopalpebral fascia.

Tarsus

• Horizontal length: 25-30 mm
• Vertical height: Upper = 10-12 mm; Lower = 3-5 mm

Conjunctiva

• Palpebral conjunctiva - lines the eyelid
• Bulbar conjunctiva - lines the globe
• They meet at the conjunctival fornix

- Cummings Otolaryngology Head and Neck Surgery

3. Peribulbar Block (Anaesthesia)

Terminology and Anatomy

• Retrobulbar (intraconal) block: Needle directed through the muscle cone toward the orbital apex - local anesthetic deposited inside the cone.
• Peribulbar (extraconal) block: Needle kept outside the muscle cone, directed parallel to the globe toward the greater wing of the sphenoid. Local anesthetic diffuses from the extraconal space into the intraconal space (cadaveric dissections confirm no complete intermuscular septum exists, so dye crosses freely).

Comparison: Peribulbar vs. Retrobulbar

Technique (Morgan & Mikhail)

1. Patient supine, looking straight ahead (or under brief deep sedation)
2. Topical anaesthesia of the conjunctiva applied first
3. Inferotemporal injection (primary):
   • Needle inserted halfway between lateral canthus and lateral limbus
   • Advanced under the globe, parallel to orbital floor
   • Past the equator of the eye: redirected slightly medial (20°) and cephalad (10°)
   • 5 mL of local anaesthetic injected
4. Medial (nasal) injection (second, for akinesia):
   • Through conjunctiva medial to the caruncle
   • Directed straight back, parallel to medial orbital wall, pointing slightly cephalad (~20°)
   • 5 mL injected (total ~10 mL)

Local Anaesthetic Agents Used

• Lignocaine (lidocaine) 2% + Bupivacaine 0.5% (1:1)
• May add hyaluronidase (150-300 IU) to improve spread

Complications

• Ecchymosis / periorbital haematoma (most common)
• Globe perforation (rare but serious)
• Retrobulbar haemorrhage
• Optic nerve injury
• Brainstem anaesthesia (from intravascular injection or spread along optic nerve sheath)
• Local anaesthetic toxicity

Adjuncts

• Facial nerve block (van Lint, Atkinson, or O'Brien technique) may be added to prevent lid squeezing and allow lid speculum placement.
• Ocular compression (e.g., Honan balloon at 30 mmHg for 10 min) after injection helps distribute anaesthetic and lowers IOP.

- Morgan and Mikhail's Clinical Anesthesiology, 7e; Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e

4. Lens-Induced Glaucoma

A. Phacolytic Glaucoma

• Associated with a hypermature cataract
• High molecular-weight lens proteins leak through the intact lens capsule into the aqueous
• These proteins obstruct the trabecular meshwork
• Macrophages that have ingested lens proteins also accumulate and contribute to trabecular obstruction

• Painful eye with poor vision (hypermature cataract)
• Corneal oedema
• Deep anterior chamber (distinguishes from phacomorphic)
• Large white floating particles in AC (lens protein + macrophages)
• Milky aqueous or pseudohypopyon if very dense
• Gonioscopy: open angle with lens-derived material; most prominent inferiorly

1. Medically reduce IOP first
2. Wash out proteinaceous material from anterior chamber
3. Cataract extraction (definitive) - zonules are likely more fragile than usual

B. Phacomorphic Glaucoma

• Caused by an intumescent (swollen) cataractous lens
• Equatorial growth of the lens slackens the suspensory ligament → lens moves anteriorly
• Anteroposterior growth increases iridolenticular contact → pupillary block → iris bombé → angle closure

• Presentation similar to acute PACG (acute painful red eye, halos, nausea)
• Shallow anterior chamber (distinguishes from phacolytic)
• Dense white (intumescent) cataract
• Mid-dilated pupil
• Corneal oedema
• Fellow eye may have deep AC and open angle (helps differentiate from primary ACG)
• AS-OCT or UBM may be useful

1. Medical treatment initially as in acute PACG
2. Miotics are omitted (they worsen iridolenticular contact and shift lens anteriorly)
3. Mydriasis may help (with caution)
4. Systemic hyperosmotic agents (more commonly needed than in PACG)
5. Laser iridotomy - often not possible due to corneal oedema or lens-cornea proximity
6. Laser iridoplasty may temporize
7. Cataract extraction is definitive - once IOP controlled and eye quietened; surgery carries higher complication risk

C. Glaucoma from Lens Dislocation/Subluxation

• Blunt ocular trauma (especially with weak zonules - pseudoexfoliation, homocystinuria)
• Congenitally small lens - microspherophakia (e.g. Weill-Marchesani syndrome)
• Marfan syndrome

• Lens dislocated into anterior chamber → pupillary block + direct corneal endothelial damage
• Lens subluxed with partial zonule disruption → pupil block at remaining lens-iris interface
• Vitreous herniation into AC may also obstruct drainage

• Lens fully or partially visible in anterior chamber
• Sudden severe IOP elevation with visual impairment
• UBM may be diagnostic

1. Systemic osmotic agents (reduce vitreous volume) - urgent
2. Patient positioned supine, pupil dilated - attempt to reposition lens posteriorly
3. Miotic with caution after repositioning
4. Bilateral laser iridotomy (extended control in some cases)
5. Surgical lens extraction (definitive) + AC IOL / iris- or scleral-fixated IOL

D. Phacoantigenic (Phacoanaphylactic) Uveitis with Secondary Glaucoma

• Granulomatous autoimmune uveitis from lens protein exposure through a ruptured capsule (trauma or surgery)
• Can lead to secondary open-angle glaucoma from trabecular inflammation and damage

Summary Table: Lens-Induced Glaucoma

- Kanski's Clinical Ophthalmology: A Systematic Approach, 10th ed.