LENS

Complications of cataract surgery can be broadly classified into preoperative, operative, early postoperative, delayed postoperative, and IOL-related complications.

1. Preoperative Complications

These complications arise before the surgery proper begins, often related to preparation or anaesthesia:

  • Anxiety: Some patients experience anxiety on the eve of the operation.

  • Allergic Conjunctivitis: This may occur due to preoperative topical antibiotic drops.

  • Anaesthesia-related:

    • Retrobulbar haemorrhage: This may occur due to a retrobulbar block, necessitating the postponement of the operation,.

    • Globe perforation: This can occur during the injection.

    • Oculocardiac reflex: This manifests as bradycardia or cardiac arrhythmia due to the block.

    • Spontaneous dislocation of the lens: Vigorous ocular massage after a block in patients with weak zonules (e.g., hypermature cataract) can cause the lens to dislocate into the vitreous.

2. Operative (Intraoperative) Complications

These occur during the surgical procedure:

  • Incision-related:

    • Irregular incision: Common in conventional extracapsular cataract extraction (ECCE), leading to defective wound coaptation.

    • Tunnel construction issues: In manual small incision cataract surgery (SICS) and phacoemulsification, complications include button-holing of the anterior wall, premature entry into the anterior chamber, and scleral disinsertion,.

  • Bleeding: Excessive bleeding may occur during conjunctival flap preparation or scleral incision.

  • Injury to ocular structures:

    • Cornea: Detachment of Descemet's membrane may occur.

    • Iris: Injury may lead to iridodialysis (tear of iris from the root).

    • Superior Rectus Muscle: Laceration or hematoma may occur while applying the bridle suture.

  • Capsulorrhexis complications: These include escaping capsulorrhexis (extending to the equator), small capsulorrhexis (predisposing to posterior capsular rupture), or eccentric capsulorrhexis.

  • Posterior Capsular Rupture (PCR): This is a dreaded complication, potentially leading to the nucleus dropping into the vitreous. It can be caused by forceful hydrodissection, direct instrument injury, or accidental aspiration.

  • Zonular Dehiscence: This is especially common during nucleus prolapse in manual SICS.

  • Vitreous Loss/Prolapse: This is a serious complication following PCR.

  • Nucleus Drop: The nucleus may drop into the vitreous cavity, a complication more frequent with phacoemulsification than manual SICS.

  • Expulsive Choroidal Haemorrhage: A serious and dreadful complication characterized by spontaneous wound gaping and expulsion of ocular contents due to a gush of blood.

3. Early Postoperative Complications

These typically occur within the first few days or weeks after surgery:

  • Hyphaema: Blood collection in the anterior chamber, which usually absorbs spontaneously but may require drainage if it causes raised intraocular pressure (IOP).

  • Iris Prolapse: Caused by inadequate suturing, usually occurring in the first few days post-op.

  • Striate Keratopathy: Characterized by corneal oedema and Descemet's folds due to endothelial damage during surgery.

  • Flat Anterior Chamber: This may result from a wound leak, ciliochoroidal detachment, or pupil block,.

  • Bacterial Endophthalmitis: A dreaded complication presenting with ocular pain, lid oedema, hypopyon, and loss of red pupillary glow, usually between 48 and 72 hours after surgery.

  • Toxic Anterior Segment Syndrome (TASS): A sterile inflammation caused by toxic substances, characterized by violent inflammation,.

  • Postoperative Anterior Uveitis: Induced by trauma, residual cortex, or reaction to viscoelastics.

  • Raised Intraocular Pressure: This can be due to retained viscoelastic material, inflammation, or pupil block,.

4. Late Postoperative Complications

These may appear months or years later:

  • After-Cataract (Posterior Capsule Opacification - PCO): The most common postoperative complication, involving opacity persisting or developing after extracapsular extraction. It may present as Elschnig’s pearls, Soemmerring’s ring, or a dense membranous sheet.

  • Cystoid Macular Oedema (CME): Fluid collection in the macula, often associated with vitreous incarceration or mild iritis,.

  • Retinal Detachment (RD): The incidence is higher in aphakic patients compared to pseudophakic ones.

  • Pseudophakic Bullous Keratopathy (PBK): A continuation of postoperative corneal oedema due to endothelial damage.

  • Delayed Chronic Endophthalmitis: Caused by low-virulence organisms like Propionibacterium acnes trapped in the capsular bag, occurring weeks to years later.

  • Epithelial Ingrowth: Conjunctival cells invade the anterior chamber through a defective incision, potentially causing intractable glaucoma.

  • Fibrous Downgrowth: Rare growth into the anterior chamber causing secondary glaucoma or phthisis bulbi.

5. IOL-Related Complications

  • Malpositions: These include decentration, sunset syndrome (inferior subluxation), sunrise syndrome (superior subluxation), and lost lens syndrome (dislocation into the vitreous),.

  • UGH Syndrome: Uveitis-Glaucoma-Hyphema syndrome, historically associated with rigid anterior chamber IOLs.

  • Toxic Lens Syndrome: IOL-induced iritis.

  • Pupillary Capture: The iris may be captured by the IOL.

  • Windshield Wiper Syndrome: Occurs when a small IOL placed in the sulcus moves left and right with head movements.

Specific Procedure-Related Risks

  • Refractive Lens Exchange (RLE): Complications can include endophthalmitis, after-cataract, and retinal detachment.

  • Phakic IOLs: Risks include endophthalmitis, iridocyclitis, cataract formation, and secondary glaucoma.

  • Phacoemulsification vs. Manual SICS: Phacoemulsification has a higher risk of nucleus drop and a steeper learning curve, whereas manual SICS has a higher rate of surgically induced astigmatism and postoperative congestion,,.



ZONULAR CATARACT

Based on the provided sources, here is a detailed overview of Zonular cataract, also known as Lamellar cataract:

Definition and Prevalence

  • Terminology: Zonular cataract is also referred to as lamellar cataract.

  • Prevalence: It is the most common type of congenital cataract presenting with visual impairment, accounting for approximately 50% of such cases.

  • Nature: It is a developmental cataract where the opacity is limited to a discrete zone within the lens.

Clinical Characteristics

  • Location: Typically, the opacity occupies a zone of the fetal nucleus which surrounds the embryonic nucleus,.

  • Appearance:

    • The main mass of the lens, both internal and external to the cataractous zone, remains clear,.

    • A characteristic feature is the presence of "riders," which are small linear opacities resembling the spokes of a wheel that extend outwards toward the equator,.

    • In cases associated with hypocalcemia, it is characterized by a thin opacified lamella located deep in the infantile cortex.

    • Occasionally, two rings of opacity may be observed.

  • Laterality: The condition is usually bilateral,.

  • Visual Impact: It frequently results in severe visual defects.

Etiology

The causes of zonular cataract can be genetic or environmental:

  • Heredity: It is a common familial cataract, usually inherited as an autosomal dominant trait,.

  • Nutritional and Metabolic Factors:

    • Vitamin D deficiency: This is a known cause.

    • Hypocalcemia: Deficiency in calcium is a cause. Zonular cataracts are seen in infants with hypocalcemia (tetanic cataract).

    • Malnutrition: Maternal malnutrition during pregnancy is associated with the non-familial form of zonular cataract.

  • Infection: Maternal rubella infection, specifically when contracted between the 7th and 8th week of gestation, may cause lamellar cataract.

  • Trauma: Though rare, traumatic zonular cataract may occur.