1. Grading of Nuclear Cataract

Emery-Little Classification (most common clinical grading)

• Higher grades require greater phacoemulsification energy and carry more risk of corneal endothelial damage.

LOCS III (Lens Opacities Classification System III)

• NO1/NC1 = trace - faint yellow
• NO2/NC2 = mild yellow
• NO3/NC3 = ocher (orange-yellow)
• NO4/NC4 = amber/orange
• NO5/NC5 = brown
• NO6/NC6 = black (brunescent nigra)

Oxford System

Clinical slit-lamp grading (practical):

• Nuclear color is assessed with broad oblique slit beam and retroillumination.
• Darker color = harder nucleus = more surgical energy required.
• Brunescent (grade IV-V) cataracts have a high risk of posterior capsule rupture and endothelial cell loss.

2. Lid Anatomy

Layers from anterior to posterior (Upper Eyelid)

1. Skin - the thinnest skin in the body; no subcutaneous fat.
2. Orbicularis oculi muscle (striated, facial nerve CN VII) - very vascular; subcutaneous fat is absent, so local anaesthetic should be placed just under the skin to avoid haematoma.
3. Orbital septum - a fibrous diaphragm arising from the arcus marginalis along the superior orbital margin; fuses with the levator aponeurosis just above the tarsal plate.
4. Preaponeurotic fat pad - lies immediately posterior to the orbital septum; key surgical landmark to identify the levator aponeurosis beneath it. Contains two compartments: medial (pale/white fat) and central/main fat pad.
5. Levator aponeurosis - fibrous extension of the levator palpebrae superioris muscle; inserts into anterior surface of tarsus and skin at the level of the skin crease (creating the crease).
6. Müller's muscle (superior tarsal muscle) - smooth muscle, sympathetically innervated (CN III for levator, but Müller's is adrenergic); arises from undersurface of levator muscle, inserts into upper border of tarsus; contributes ~2 mm to lid elevation.
7. Tarsal plate - dense fibrous tissue providing structural rigidity; upper tarsus is 8-10 mm high, lower tarsus is 4-5 mm. Contains meibomian glands (modified sebaceous glands).
8. Palpebral conjunctiva - tightly adherent to posterior tarsal surface.

Lower Eyelid Layers (anterior to posterior)

1. Skin
2. Orbicularis oculi
3. Orbital septum (arising from arcus marginalis inferiorly)
4. Preaponeurotic fat (3 compartments: medial, central, lateral)
5. Capsulopalpebral fascia (lower eyelid retractor - equivalent to levator aponeurosis)
6. Lower eyelid equivalent of Müller's muscle
7. Inferior tarsal plate (4-5 mm)
8. Palpebral conjunctiva

Skin crease

• Males: ~5-6 mm above lash line; Females: ~7-8 mm above lash line.
• In East Asian eyelids, the orbital septum fuses lower on the levator aponeurosis, allowing preaponeurotic fat to descend and prevent a high skin crease.

Key landmarks

• Medial canthus: contains the lacrimal puncta, canaliculi, lacrimal sac; medial canthal tendon (anterior and posterior limbs).
• Lateral canthus: lateral canthal tendon attaches to Whitnall's tubercle on inner surface of the lateral orbital rim.
• Whitnall's ligament (superior transverse ligament): acts as a pulley for the levator.
• Lockwood's ligament (suspensory ligament of globe): suspends the globe from below.
• Inferior oblique muscle: passes between the medial and central fat compartments of the lower lid.
• Arcuate expansion: fascial extension of inferior oblique separating central and lateral fat compartments.

3. Peribulbar Block (Anaesthesia)

Background

Advantages over retrobulbar block

• No intraconal needle placement - lower risk of globe perforation, optic nerve damage, and retrobulbar haemorrhage
• Less pain on injection
• Safer in anticoagulated patients (relatively)
• No brainstem anaesthesia risk

Disadvantages

• Slower onset (5-15 min vs 3-5 min for retrobulbar)
• Greater volume of anaesthetic needed (5-10 mL vs 2-5 mL)
• More likely to cause chemosis and ecchymosis
• Akinesia may be incomplete - a second injection is often needed

Technique

Inferotemporal injection (first injection)

• Needle: 23-25 gauge, 25 mm; bevel up
• Entry point: Junction of the middle and lateral thirds of the lower lid margin, just above the inferior orbital rim
• Direction: Directed vertically backwards, parallel to the orbital floor (no angulation medially until past the equator of the globe)
• After passing the equator: redirect needle slightly medially (20°) and cephalad (10°)
• Depth: Less than 25 mm (avoid going beyond this to prevent intraconal placement)
• Volume: 5 mL of local anaesthetic injected

Superonasal injection (second injection, if needed)

• Entry: Through conjunctiva, medial to the caruncle, on the nasal side
• Direction: Straight back, parallel to the medial orbital wall, pointing slightly cephalad (20°)
• Volume: 5 mL
• Provides additional akinesia of the superior rectus and medial rectus

Local anaesthetic solution

• Commonly: Lignocaine 2% + bupivacaine 0.5% (1:1 mixture) ± hyaluronidase (to enhance spread and density of block; rare allergic reactions possible)
• Typical total volume: 5-10 mL per block

Ocular compression

• After injection, apply gentle ocular compression (Honan balloon or digital pressure) for 5-10 min to spread anaesthetic and soften the globe.

Facial nerve block (adjunct)

• Often added for akinesia of orbicularis oculi (to prevent lid squeeze, which raises IOP)
• Options:
  • Modified Van Lint block: 1 cm lateral to orbital rim at superolateral and inferolateral margins; 2-4 mL
  • Atkinson block: Inferior margin of zygomatic bone; needle 30° from vertical
  • O'Brien block: At mandibular condyle (proximal trunk)

Complications

4. Lens-Induced Glaucoma

4.1 Phacolytic Glaucoma (Lens Protein Glaucoma)

• Markedly raised IOP
• Iridescent particles and white material in anterior chamber
• Hypermature (Morgagnian) or mature cataract with intact capsule
• Large white cells in AC (macrophages bloated with lens material)
• Pseudohypopyon possible
• Open angle on gonioscopy (clumps of macrophages in inferior angle)

• Medical (immediate IOP lowering): Topical β-blocker, α2-agonist, topical/systemic CAI (acetazolamide 500 mg), topical steroid (prednisolone acetate 1% q1h), cycloplegic, mannitol if needed
• Definitive: Cataract extraction (urgent, within 24-48 hrs if IOP uncontrolled). Glaucoma surgery usually not needed.

4.2 Lens Particle Glaucoma

• White, fluffy pieces of lens cortex in the anterior chamber
• Raised IOP
• AC cell and flare, open angle on gonioscopy

4.3 Phacomorphic Glaucoma

• Acute: IV mannitol, acetazolamide, topical IOP-lowering agents, pilocarpine to constrict pupil
• Laser iridotomy to break pupillary block
• Definitive: Cataract extraction (resolves the underlying cause)

4.4 Phacoantigenic Glaucoma (Phacoanaphylaxis)

Summary Table: Lens-Induced Glaucoma