Katarak Senilis

01Pathophysiology

Cataract is defined as opacification of the crystalline lens that causes progressive decline in visual acuity. The lens is an avascular, biconvex structure composed of highly organized protein fibers (crystallins) enclosed within a capsule. Its transparency depends on the precise arrangement of these fibers and the maintenance of an appropriate intracellular environment.

The mechanism of cataract formation is multifactorial. Oxidation of membrane lipids, structural and enzymatic lens proteins, and DNA by peroxides and free radicals, particularly those generated by ultraviolet radiation, initiates the loss of transparency in the nucleus and cortex. This oxidative damage leads to protein aggregation, increasing molecular weight and optical density. As the refractive index of the nucleus changes, a progressive myopic shift occurs, which explains the clinical phenomenon of "second sight" in which a presbyopic patient temporarily regains near vision without reading glasses. Importantly, this myopic shift and second sight are characteristic of nuclear cataract and are not seen in posterior subcapsular or anterior cortical forms.

In cortical cataract, electrolyte imbalance leads to lens overhydration and liquefaction. Clinically this manifests as vacuoles, clefts, or lamellar separations visible on slit lamp. In nuclear cataract, protein denaturation from oxidation, proteolysis, and glycation causes the central lens to become opaque with a yellowish to brown discoloration visible on slit lamp.

The cataractous lens shows edema, protein alteration, proliferative changes, and disruption of lens fiber continuity. The degree of edema correlates with the stage of progression:

• Immature (insipient): only partially opaque; lens still partially transparent

• Mature: totally opaque with mild lens edema

• Intumescent: maximal water content causing the lens to swell and the capsule to stretch, which can precipitate angle-closure (phacomorphic glaucoma)

• Hypermature: relative dehydration with capsular wrinkling; liquefied cortex may leak proteins through the capsule, triggering phacolytic glaucoma

This pathophysiology directly explains why cataract causes glare: scattered light through irregular opacities reduces contrast sensitivity. It also explains monocular diplopia: a refractive gradient within a partially opaque nucleus creates a second focal point that cannot be corrected with glasses, prisms, or contact lenses.

02Classification and Clinical Manifestation

Classification by Anatomical Location

Classification by Maturity

Clinical Symptoms

03Diagnostic Workup

The diagnostic workup for cataract begins at the primary care level (FPKTP) with three simple tools: visual acuity measurement using a Snellen chart with pinhole, a shadow test using a penlight, and direct ophthalmoscopy. A patient whose VA is less than 6/12 and does not improve with pinhole should raise suspicion for a media opacity rather than uncorrected refractive error. The shadow test helps stage the cataract at the bedside: a crescent-shaped shadow on the lens surface when light is directed from the side indicates an immature cataract, while the absence of a shadow indicates a mature cataract where the entire lens is opaque.

At the secondary/tertiary level (FPKTL), the definitive diagnostic tool is the slit lamp biomicroscope, which allows direct visualization and grading of the lens opacity. Slit lamp examination should be performed both before and after pupil dilation. The Lens Opacity Classification System III (LOCS III) is the most widely used grading criteria. While diagnosis can technically be made with a penlight and ophthalmoscope, the PNPK states that slit lamp examination (dilated and undilated) is the standard of care for cataract diagnosis.

Biometry is a routine preoperative study used to calculate the appropriate IOL power. The PNPK notes that optical biometry (e.g., OLIB) is superior to immersion A-scan ultrasound (Grade B, Level IIa). For patients with high myopia (axial length > 26 mm), swept-source OCT biometry and newer IOL formulas (Barrett Universal II, Olsen, Hill-RBF) are recommended for improved accuracy.

Ocular ultrasound (B-scan) is indicated when the fundus cannot be visualized due to dense media opacity. This is critical in mature/total monocular cataracts or cataracts suspected to result from posterior segment pathology or trauma, because the surgeon needs to know the status of the retina and vitreous before operating.

Specular microscopy for corneal endothelial cell count is reserved for patients with suspected corneal endothelial disease or complicated cases. If specular microscopy is unavailable, specular reflection using the slit lamp can provide a rough assessment of endothelial health.

04Management and Treatment

Surgical Techniques

The PNPK outlines the following operative sequence for phacoemulsification:

1. Corneal incision creation

2. Intracameral adrenaline injection followed by anterior capsule staining

3. Viscoelastic injection into the anterior chamber

4. Continuous curvilinear capsulorhexis (CCC)

5. Phacoemulsification and aspiration of lens material until clean

6. Intraocular lens implantation

7. Irrigation and aspiration of residual viscoelastic

8. Intracameral antibiotic injection and wound closure

IOL Selection

Foldable single-piece IOL placed within the capsular bag is the standard. The PNPK provides several important IOL pearls:

• Silicone IOL is not recommended for patients with a history of posterior segment surgery or planned vitreoretinal surgery using silicone oil or gas tamponade, because silicone oil adherence to the IOL can impair visualization.

• Single-piece foldable IOL should not be placed in the sulcus (only in the bag), as sulcus placement risks iris chafing, glaucoma, inflammation, hyphema, and macular edema.

• Toric IOL should be considered when corneal astigmatism is ≥ 1.0 D, with greatest clinical benefit at ≥ 1.5 to 2.0 D (per ESCRS).

• Multifocal IOL requires careful patient selection and counseling regarding possible reduced contrast sensitivity, glare, halo, and mildly hazy vision; patients may still need glasses for certain activities.

• Non-foldable IOL is still acceptable when foldable IOL is unavailable, but requires suturing due to larger incision.

Indications for Secondary IOL Implantation

Secondary IOL is placed when the primary surgery could not include an IOL due to zonular or capsular bag inadequacy or elevated IOP during surgery. It is also indicated for aphakia, IOL subluxation/dislocation, IOL opacification, or refractive surprise. Secondary IOL implantation should only proceed once the eye is free of infection and inflammation.

Perioperative Protocol Highlights

Postoperative Management

Postoperative medications (minimum 4 weeks unless otherwise indicated):

• Combination antibiotic-steroid eye drops daily

• Topical antibiotic alone for infection prevention

• Topical steroid and/or NSAID for inflammation and CME prevention (combination steroid + NSAID strongly recommended for high-risk patients: diabetes, uveitis history, prior CME, complex surgery); duration approximately 3 to 4 weeks, adjusted by response

• Oral analgesics, antiglaucoma agents, or corneal edema therapy as indicated

• Eye shield/protector, especially during sleep in the first few days

Special Populations

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common trap with cataract questions on licensing exams is confusing the indication for referral or surgery with the visual acuity threshold alone. The PNPK and international guidelines (NICE NG77, WHO 2030 Targets) clearly state that the decision to refer and operate should be based on functional impact on quality of life and daily activities, not solely on a visual acuity cutoff. A patient with VA of 6/12 or better who is a professional driver experiencing dangerous glare at night is a valid surgical candidate. Do not select "observe" just because the Snellen chart reads 6/12.

A second common trap involves the shadow test. Students often reverse the interpretation. Remember: a positive shadow test (shadow visible) means the lens is only partially opaque (immature), because the opacity acts as an obstacle casting a shadow from the translucent remainder. A negative shadow test (no shadow) means the lens is uniformly and totally opaque (mature), so there is no translucent region to create contrast.

Third, when a vignette describes a presbyopic patient who "no longer needs reading glasses," do not assume improvement. This is "second sight" from a nuclear cataract causing myopic shift. It signals worsening disease, not resolution.

Fourth, be careful with the intumescent cataract vignette. If a patient presents with acute eye pain, red eye, elevated IOP, and a swollen lens, the diagnosis is phacomorphic glaucoma (angle-closure secondary to lens swelling). The next step is to lower IOP medically first, then proceed with cataract extraction. Do not confuse this with primary angle-closure glaucoma, which is treated with laser peripheral iridotomy.

Fifth, for the endophthalmitis question: the PNPK and ESCRS recommend intracameral antibiotic (levofloxacin or cefuroxime) at the end of surgery as prophylaxis. If a vignette describes severe pain, vision loss, hypopion, and significant anterior chamber reaction within days of cataract surgery, the answer is endophthalmitis, and treatment per the Endophthalmitis Vitrectomy Study is intravitreal antibiotics (ceftazidime + vancomycin), with vitrectomy reserved for cases with vision of hand motion or worse (though ESCRS now recommends earlier vitrectomy regardless of presenting VA).

Finally, do not confuse TASS (Toxic Anterior Segment Syndrome) with infectious endophthalmitis. TASS occurs within 12 to 48 hours after surgery, is sterile (caused by contaminants on instruments or non-standard irrigating solutions), shows diffuse corneal edema with minimal pain, and responds to topical anti-inflammatory therapy. Endophthalmitis typically presents later (days to a week), with more severe pain and vitritis, and requires intravitreal antibiotics. When in doubt, the PNPK advises obtaining a specimen for microbiological culture before initiating treatment.

The core competency being tested across all cataract questions is the ability to (1) recognize the presentation and stage the disease accurately, (2) understand when to refer versus observe, (3) identify the gold-standard surgical approach and its alternatives, and (4) recognize and manage postoperative complications promptly.