Ophthalmology
Lens and Cataract
Lens and cataract for MBBS and NEET-PG: types and stages of cataract, biometry, phacoemulsification, small-incision surgery, and complications, mapped to NMC codes OP7.
MedNext Academy | 3 min read
Lens and Cataract
Lens and cataract for MBBS and NEET-PG: types and stages of cataract, biometry, phacoemulsification, small-incision surgery, and complications, mapped to NMC codes OP7.
This chapter covers the crystalline lens and its opacification, the single largest cause of curable blindness. It sets out the metabolism and surgical anatomy of the lens, the types, stages and causes of cataract, the preoperative work-up including biometry, and the surgical techniques from phacoemulsification to small-incision surgery with their complications.
High-yield: Lens and Cataract
- The lens is avascular and transparent and gets its nutrition from the surrounding aqueous humour, so a loss of this metabolic balance leads to opacification.
- A cataract is any opacity of the lens or its capsule and is the leading cause of reversible blindness worldwide.
- Senile cataract is the commonest type, and its subtypes are nuclear, cortical and posterior subcapsular.
- A posterior subcapsular cataract causes disproportionate difficulty with near vision and glare and is associated with steroids and diabetes.
- Diabetes, corticosteroids, trauma, radiation and intraocular inflammation are important causes of secondary cataract.
- A mature cataract is completely opaque with a white pupil, while a hypermature cataract may leak lens protein and cause phacolytic glaucoma.
- Second sight is a temporary improvement in near vision as an early nuclear cataract increases the refractive power of the lens, producing a myopic shift.
- A congenital cataract must be detected early through an absent red reflex (leucocoria) and removed promptly to prevent stimulus-deprivation amblyopia.
- Preoperative assessment includes visual acuity, refraction, slit-lamp grading, intraocular pressure and biometry to calculate intraocular lens power.
- Phacoemulsification uses ultrasound to fragment and aspirate the lens through a small self-sealing incision and is the modern standard.
- Small-incision cataract surgery is a low-cost, sutureless manual technique widely used in high-volume settings in India.
- Extracapsular cataract extraction retains the posterior capsule to support the intraocular lens, unlike the older intracapsular technique.
- Posterior capsular opacification, an after-cataract, is the commonest late complication of surgery and is treated by YAG laser capsulotomy.
- Endophthalmitis is a rare but devastating postoperative infection presenting with pain, reduced vision and hypopyon, and needs urgent intravitreal antibiotics.
Cataract surgery techniques
- **Phacoemulsification:** Ultrasound fragmentation through a small self-sealing incision. Modern standard.
- **Small-incision (SICS):** Manual, sutureless, low-cost. High-volume settings in India.
- **Extracapsular (ECCE):** Retains posterior capsule to support the intraocular lens.
- **Intracapsular (ICCE):** Removes lens with capsule. Largely historical.
NMC competencies in this chapter
- **OP7.1:** Surgical anatomy and metabolism of the lens
- **OP7.2:** Cataract: aetiopathogenesis, stages and complications
- **OP7.3:** Ocular examination in cataract
- **OP7.4:** Cataract surgery types and ECCE complications
- **OP7.5:** Participation in the cataract surgery team
- **OP7.6:** Consent and counselling for cataract surgery
- **OP8.5:** Optic nerve and visual pathway disease
Frequently Asked Questions
What is a cataract?
It is any opacity of the crystalline lens or its capsule. It scatters light and reduces vision, and it is the leading cause of reversible blindness worldwide, treated by surgical removal and lens implantation.
What is second sight in cataract?
As an early nuclear cataract increases the refractive power of the lens, it causes a myopic shift, so a previously long-sighted patient may temporarily read without glasses before vision worsens.
Which cataract surgery is standard today?
Phacoemulsification, which uses ultrasound to fragment and aspirate the lens through a small self-sealing incision, is the modern standard. Small-incision cataract surgery is a widely used low-cost alternative in India.
What is posterior capsular opacification?
It is clouding of the retained posterior capsule after cataract surgery, the commonest late complication, causing gradual blurring. It is treated painlessly with a YAG laser capsulotomy.
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