MS Ophthalmology Theory Exam Question

1. Definition

• Cyclodialysis: disinsertion of the ciliary body from the scleral spur (creates a suprachoroidal-anterior chamber communication -> hypotony via increased uveoscleral outflow).
• Angle recession: a tear between the longitudinal and circular fibers of the ciliary muscle, without full iris disinsertion.

2. Etiopathogenesis

• Coup-contrecoup mechanism: sudden anteroposterior compression -> equatorial expansion of the globe -> shearing force at the iris root (the weakest point of iris attachment).
• Causes: blunt trauma (most common - fist, ball, airbag), penetrating/perforating injury, intraocular surgery (phacoemulsification, especially with iris hooks/rings, malpositioned trocars), and rarely spontaneous in connective tissue disorders.

3. Clinical Features

• Often asymptomatic if small; larger dialyses cause monocular diplopia, glare, and photophobia.
• Classic sign: "double pupil" or D-shaped pupil with a crescentic, biconvex dark area near the limbus corresponding to the gap.
• Associated trauma signs: hyphema, angle recession, cataract, lens subluxation, pupillary irregularity.
• IOP can be decreased (early, due to associated cyclodialysis/hyposecretion) or increased (later, due to trabecular meshwork damage or peripheral anterior synechiae formation).
• Gonioscopy: shows the iris root defect and helps assess concurrent angle recession, but view may be limited by hyphema, corneal edema, or a shallow/inflamed anterior chamber early after trauma.

4. Role of Ultrasound Biomicroscopy (UBM)

1. Confirm and precisely localize the iris root defect when the view is obscured by hyphema, corneal edema, or a miotic/irregular pupil.
2. Measure the extent (clock hours) and width of the dialysis - essential for surgical planning (size of flap, number of sutures needed).
3. Differentiate iridodialysis from cyclodialysis cleft (ciliary body detachment) - critical because management differs (cyclodialysis needs cleft closure, not iris repair).
4. Detect associated occult findings: angle recession, zonular dialysis/lens subluxation, ciliary body detachment, choroidal effusion, suprachoroidal hemorrhage - all relevant in hypotony workup.
5. Postoperative assessment of anatomical success after repair (confirm apposition of iris root to sclera/ciliary sulcus, patency of the reformed angle).

• A gap/discontinuity at the iris root with the iris stump retracted away from the scleral spur, seen as an abrupt loss of continuity between the peripheral iris and the ciliary body face.
• Absence of the normal iris-ciliary body attachment at the site, sometimes with an adjacent cyclodialysis cleft (seen as a hypoechoic space between the ciliary body and sclera - important to identify since it drives hypotony).

5. Treatment

A. Conservative / Non-surgical

• Observation.
• Tinted/opaque contact lens with artificial pupil, or sunglasses, to control glare and monocular diplopia.
• Treat associated glaucoma medically if present: aqueous suppressants (beta-blockers, alpha-agonists, carbonic anhydrase inhibitors) are first-line. Miotics should be avoided as they may reopen an associated cyclodialysis cleft and worsen hypotony.

B. Surgical Repair

1. McCannel/Modified McCannel suture technique - a straight or curved needle with double-armed 10-0 polypropylene is passed through clear cornea (limbal approach), engaging the iris root stump, and exiting through the sclera near the limbus; the suture is tied externally under a partial-thickness scleral flap ("ab externo" technique).
2. Ab interno approach - needle passed from inside the eye through the iris stump and out through the sclera, useful when limited peripheral view.
3. Single-pass four-throw (SFT) technique - a single pass of a long needle with suture, using a Sinskey hook to retrieve the loop and create a slipknot; reduces number of needle passes and suture-related trauma.
4. Cobbler's technique (Pandav et al.) - a running "shoemaker's stitch" style suturing along the length of a large dialysis, useful for repairing extensive defects.
5. Trocar/cannula-assisted repair - use of a 23/25G trocar to guide needle passage and suture placement transsclerally with better control, minimizing tissue trauma (Narang & Agarwal techniques).
6. Dumbbell/Twofold techniques - modifications reducing the number of intraocular passes needed while ensuring firm apposition (recent Indian Journal of Ophthalmology techniques, 2022-2025).

• Peritomy and partial-thickness scleral flap/pocket at the site of dialysis.
• Anterior chamber maintained with viscoelastic or an anterior chamber maintainer.
• Needle passed through the iris stump (full-thickness, near mid-periphery) and out through sclera at the corresponding site (at the surgical limbus/ciliary sulcus).
• Suture tied with adequate tension to reposition the iris root against the ciliary sulcus without excessive traction (avoid pupil distortion).
• Knot buried under the scleral flap; flap closed with 10-0 nylon or left sutureless if self-sealing.
• Combine with cataract surgery/IOL, iris coloboma repair, or artificial iris implantation if the eye has combined pathology (common in post-traumatic or post-cataract surgery iridodialysis).

C. Combined/Complex Cases

• If associated cyclodialysis cleft with hypotony: cleft closure by direct cyclopexy sutures, diathermy, cryotherapy, argon laser to the cleft, or (in refractory cases) via pars plana approach.
• If associated with aniridia/large iris defects: artificial iris implantation combined with IOL (custom iris prosthesis, e.g., Artificial Iris/Customflex) with iridodialysis repair sutures for zonal fixation.
• Glaucoma from angle recession: managed as secondary open-angle glaucoma - medical therapy first, filtering surgery or tube shunt if refractory.

6. Complications of Iridodialysis (and its repair)

• Secondary glaucoma (angle recession, peripheral anterior synechiae).
• Hypotony maculopathy (if concurrent cyclodialysis cleft).
• Persistent glare/monocular diplopia if repair incomplete.
• Suture-related: pupil distortion (peaked pupil), iris atrophy, breakage of suture, endophthalmitis (rare), recurrent hyphema.

7. Summary Table (good for quick recall in exam)

Points to emphasize for full marks

• Always mention UBM's unique ability to image behind the iris and through opaque media as its key advantage over anterior segment OCT and gonioscopy - examiners specifically look for this comparison.
• Draw a simple diagram: eye with iris root gap, UBM probe orientation, and a suture repair schematic (McCannel loop under scleral flap) - diagrams score extra marks in MS ophthalmology practical/theory papers.
• Note that avoiding miotics (due to cyclodialysis cleft risk) is a frequently asked "trap" point.

MS Ophthalmology Theory Exam Question - Ultrasound Biomicroscopy (UBM)

1. Definition

2. Principle

• Uses a transducer with frequency 35-100 MHz, much higher than conventional A-scan/B-scan ultrasound (10-15 MHz).
• Higher frequency gives superior resolution: axial resolution ~20-25 μm, lateral resolution ~50 μm.
• Trade-off: higher frequency = lower tissue penetration. Depth of penetration is only 4-5 mm, which restricts UBM to the anterior segment only (cannot image posterior segment/retina - that remains the domain of conventional B-scan).
• Works on the same echo-reflection principle as standard ultrasound: sound waves reflect differently depending on tissue density/type, and reflected signals are reconstructed into a cross-sectional image.
• Unlike anterior segment OCT (which uses light and is blocked by opacities), ultrasound can pass through blood, pigment, and opaque tissue - so UBM can image behind the iris (ciliary body, zonules, posterior chamber) and through hazy media.

3. Technique/Procedure

• Performed with the patient supine.
• Topical anesthesia instilled; an eyecup/scleral shell filled with a coupling medium (saline or methylcellulose) is placed over the eye, or a water-bath immersion technique is used.
• The probe is not in direct contact with the cornea (immersion technique) to avoid corneal distortion/artifact.
• Multiple radial and axial scans are taken (usually 4 quadrants - superior, inferior, nasal, temporal) to give a 360-degree assessment of the angle and ciliary body.
• Key landmark for interpretation: the scleral spur, a wedge-shaped protrusion of sclera marking the anterior extent of the ciliary body and posterior extent of the trabecular meshwork - used as the reference point for all angle measurements.
• Quantitative angle parameters measured: AOD500 (angle opening distance at 500 μm from scleral spur), TISA (trabecular-iris surface area), ACD (anterior chamber depth), ACW (angle-to-angle width).

4. Indications / Clinical Applications

• Differentiating types of angle closure: pupillary block vs plateau iris configuration (UBM shows anteriorly positioned ciliary processes pushing the peripheral iris forward, with a flat iris plane after iridotomy - diagnostic of plateau iris).
• Assessing angle status when gonioscopy is not possible (corneal edema, hyphema, uncooperative patient).
• Malignant glaucoma / aqueous misdirection - shows anterior rotation of ciliary body and forward-shifted lens-iris diaphragm.
• Evaluating filtering blebs and bleb function after trabeculectomy.

• Localizing and measuring iridodialysis and cyclodialysis clefts even through hyphema or corneal edema.
• Detecting occult zonular dialysis, lens subluxation, and ciliary body detachment.
• Assessing suprachoroidal hemorrhage/effusion in hypotony.

• Iris and ciliary body cysts and tumors (melanoma, medulloepithelioma) - determines size, extent, and whether there is extrascleral extension; helps differentiate solid tumor from cystic lesion.

• IOL position, sulcus-fixated or scleral-fixated IOL haptic location, and integrity of posterior capsule.
• Subluxated natural lens or IOL, zonular status (e.g., in pseudoexfoliation, trauma, Marfan syndrome).

• Corneal thickness/pachymetry in unusual cases, scleral thinning, and depth of corneal pathology before keratoplasty.

• Identifies cyclodialysis cleft, ciliary body detachment, or cyclitic membrane as the cause.

5. Advantages of UBM

• Can image through opaque media (hyphema, corneal edema, blood, dense cataract) where slit-lamp, gonioscopy, and AS-OCT fail.
• Only modality that reliably images structures behind the iris - ciliary body, zonules, pars plicata.
• High resolution, non-invasive, quick, no radiation.
• Provides quantitative angle metrics useful for research and serial follow-up.

6. Limitations

• Requires an eyecup/immersion technique with direct contact -> mild patient discomfort, needs skilled technician, and risk of corneal epithelial abrasion.
• Limited depth of penetration (4-5 mm) - cannot assess posterior segment.
• Lower resolution than AS-OCT for very fine anterior structures (AS-OCT gives better corneal/angle detail without contact but cannot see behind the iris).
• Operator-dependent; image quality affected by probe angulation and patient cooperation/fixation.
• Time-consuming compared to AS-OCT (which is fast, non-contact).

7. UBM vs Anterior Segment OCT (quick comparison table for exam)