CATARACT SURGERY
| BIMANUAL MICROINCISION PHACOEMULSIFICATION —I. Howard Fine, MD, Clinical Professor of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland |
| Power modulations: phacoemulsification of all grades of cataracts achieved with 0.1% of energy required by other techniques; likelihood of success (completely clear cornea and uncorrected visual acuity of 20/40 or better in immediate postoperative period) inversely proportional to amount of energy put into eye |
| Bimanual microincision phacoemulsification: advantages over coaxial phacoemulsification—smaller incision (safer; reduces leakage from incision); incoming stream of fluid acts as tool to direct tissue within eye; improved stability of chambers |
| Surgical tips: diamond keratomes—produce precise reproducible incision architecture; front-irrigating choppers— immediately expand anterior chamber, preventing disruption of intraocular tissue; allow constant flow while handpiece manipulated; prevent flow of irrigation toward endothelium; wound closure—better in hard eyes (expand chamber with irrigating chopper before inserting needle); phacoemulsification needle—insert needle with bevel facing downward; rotate needle as it reaches internal incision (to avoid Descemet’s membrane); face bevel downward during procedure; consider using straight needle for capsulorrhexis in eyes with subluxed lenses; intraocular pressure (IOP)—avoid overpressurizing chamber by applying small amount of pressure to posterior lip of incision during hydrodelineation and hydrodissection; separation of cortex from capsule—perform cortical-cleaving hydrodissection (lens should spin easily) before hydrodelineation; hydrodelineation ring—peripheral in firm nuclei; central in soft nuclei; horizontal chop— avoid in eyes with hard nuclei or clear lenses; position of irrigation chopper—work below irrigation chopper; avoid blowing incoming stream of fluid at tip; incisions—avoid steep axis of incision; perform temporal clear corneal incisions (safest; least potential for astigmatism); perform limbal-relaxing incisions on steep axis; avoid enlarging microincisions to implant lens (affects ability to seal); instead, implant lens between microincisions |
| Surgical outcomes: results (clearness of cornea and visual acuity) of bimanual microincision phacoemulsification similar to those of coaxial phacoemulsification; combination of sonic and ultrasonic waves reduces energy into eye |
| Case 1: elderly woman with dense mature cataract that developed after blunt trauma has light-projection vision only; surgical notes—trypan blue ophthalmic solution (Vision Blue) preferred over indocyanine green; air expressed while directing viscoelastic (Viscoat) in opposite angle; microincision forceps useful for capsulorrhexis (improved precision and reproducibility); use of capsular tension rings (CTRs) recommended in all patients with history of ocular trauma; viscoelastic prevents “trampolining” of chamber; CTR guided into capsular fornix; chopper introduced upside-down, then rotated as vertical element enters eye; vertical chop method performed, chopping just in front of nucleus; phacoemulsification needle with 30°-tip inserted bevel-down at 30°-angle, resulting in occlusion of tip with endonucleus and immediate vacuum; all forces directed toward cataract; nuclear material mobilized at level of capsulorrhexis; cataract divided into small pieces and removed; power modulations reduce energy into eye; effective time of phacoemulsification ≈20 sec; corneal edema and striae rare; implant placed between microincisions and overlying fibrotic capsular cortical remnant trimmed with vitrector to clear visual axis; outcome—uncorrected visual acuity of 20/50 in immediate postoperative period |
| Case 2: woman blind in 1 eye presents with glaucoma and pseudoexfoliation in contralateral eye; bleeding began from multiple locations in iris 1 day after surgery and continued for \>1 day; irrigating cannula and microtip cautery implemented; sources of bleeding identified by pinching tubing from irrigating cannula (causing eye to soften); bleeding controlled; patient recovered with visual acuity of 20/50 |
| Case 3: patient with Marfan syndrome with severely subluxed lens; risk of losing viscoelastic during capsulorrhexis (resulting in trampolining of lens and damage to zonular apparatus); Fine-Hoffman forceps (Microsurgical Technology) useful for cases in which chamber may fluctuate |
| Case 4: man with posterior subluxed cataract; surgery performed with patient in side-lying position; through incision in pars plana, lens and capsule moved into anterior chamber with cyclodialysis spatula; vitreous stabilized using viscoelastic; phacoemulsification performed within capsule (note, do not disassemble nucleus if fragment drops into posterior segment); vitrectomy performed; haptics of foldable lens sutured to iris |
| Case 5: patient with subluxed cataract caused by trauma; loss of zonules; CTR inserted through side port; lens hydroexpressed from bag; phacoemulsification performed in anterior chamber at level of capsulorrhexis; phacoemulsification needle and irrigator held in opposite hands so that aspiration pulls toward zonular weakness, reducing stress on residual zonules; anterior segment sequestered with viscoelastic; single-piece acrylic lens placed in bag with no trailing haptics |
| MANAGEMENT OF COMPROMISED ZONULES —Robert J. Cionni, MD, Associate Professor of Clinical Ophthalmology, University of Cincinnati, and Medical Director, Cincinnati Eye Institute, Cincinnati |
| General goals in zonular dialysis: prevent vitreous from coming forward (tamponade anterior hyaloid face if necessary); minimize stress on remaining zonules to avoid enlarging zonular dialysis; remove as much lens as possible without losing debris or damaging corneal endothelium (surgeons uncomfortable with bringing lens forward may allow bulk of nucleus to regress and place implant in ciliary sulcus, then allow retinal specialist to retrieve lens); maintain support for intraocular lens (IOL); place lens in capsular bag to maintain stability over long term |
| Techniques: put layer of dispersive viscoelastic over area of weakened zonules; add cohesive viscoelastic to cement barrier (helps maintain chamber and prevents hypotony, collapse of chamber, and vitreous prolapse); begin capsulorrhexis using strongest zonules for countertraction; perform large capsulorrhexis in order to easily manipulate nucleus; if necessary, stabilize capsular bag with iris hooks or Ahmed segment before removing lens material; perform generous hydrodissection, moving nucleus into anterior chamber if possible, to reduce stress on remaining zonules while removing nucleus; coat endothelium with dispersive viscoelastic to prevent damage when performing phacoemulsification in anterior chamber; use “slow-motion” phacoemulsification technique (low bottle, low vacuum, low rate of aspiration); use viscoelastic as tool to reduce stress on zonules (eg, expand capsular bag to pull nuclear segments forward); expand capsular bag using CTR to increase stability and improve centration |
| Case 1: patient with generalized weakening of zonules in both eyes but minimal phacodonesis; history of peripheral iridectomy (lens prolapses anteriorly, resulting in intermittent angle closure); capsulotomy and generous hydrodissection performed; weakened zonules increase risk for vitreal prolapse; irrigation maintained as viscoelastic injected to maintain chamber; cortex stripped tangentially (pulling centrally stresses zonules); soft silicone-tipped cannula less likely to break capsular bag; viscoelastic injected into capsular bag before removing tip; dull-edged chopper used to hold edge of capsulorrhexis as CTR placed manually; trailing eyelet dropped into bag using hook (eg, Sinskey hook or Y-hook); single-piece acrylic lens easy to place in eyes with weakened zonules (fold upside down, then rotate lens while injecting it into capsular bag, allowing haptics to unfold naturally); balanced salt solution (BSS) injected while removing irrigation tip to prevent chamber from shallowing; pressure applied to posterior edge of incision to check for water tightness |
| Other methods for placing CTR: injector—when residual cortex present, inject viscoelastic beneath rim of anterior capsule, dissecting cortex from periphery of capsular bag so that CTR does not trap cortex beneath it; shooter—pull CTR into shooter directly from container (setting CTR on surface of eye increases risk for contamination); begin injecting after tip of shooter inserted into capsular bag; preferences—although shooters may place more stress on zonules, those inexperienced with placing CTRs may prefer using them; finishing—strip cortex after placement of CTR |
| Surgical tips: consider placing CTR through side port, depending on location of zonular weakness; when placing CTR before removing nucleus, put suture (10.0 nylon or proline) in lead haptic (pulling on suture while injecting CTR helps guide it into capsular bag; suture also provides way to retrieve CTR if capsular bag breaks) |
| Limitations of standard CTRs: potential for reduced stability over long term in patients with large degree of zonular dialysis, significant phacodonesis or decentration of lens, or progressive zonular process (eg, pseudoexfoliation syndrome or Marfan syndrome) |
| Modified CTR: note—speaker discloses financial interest; design—fixation hook protrudes 0.25 mm into second plane; hook rests around edge of capsulorrhexis; eyelet sutured through ciliary sulcus to scleral wall; benefits—provides increased stability and centration; case series—modified CTR placed successfully in 95% of 151 eyes; at 1 yr, 100% of IOLs remained centered in capsular bags with no pseudophacodonesis, and patients had significant improvements in vision; later, some problems with sutures breaking (all 10.0 proline); speaker now uses Goretex or 9.0 proline (Mersilene also acceptable) |
| Case 2: patient with Marfan syndrome; capsulotomy, phacoemulsification, and viscodissection of cortex as previously described; modified CTR placed, with fixation hook sutured to scleral wall (note, peripheral expansion of capsular bag decreases depth); lens injected and conjunctiva brought into place; outcome—eye appears as normal pseudophakic eye, with 20/25 uncorrected visual acuity; no pseudophacodonesis as eyes track back and forth |
| Case 3: woman, 43 yr of age, with trauma to eye; pars plana vitrectomy performed (viscoelastic behind lens for support); nuclear sclerosis required phacoemulsification; capsular bag reinflated with viscoelastic before placing CTR; 9.0 proline suture through stabilizes modified CTR; remaining zonules adequately support superior pole; 3-piece lens folded and placed into capsular bag |
| Case 4: patient with Marfan syndrome with small subluxed lenses and general zonular weakness; modified CTR with 2 fixation hooks required; Goretex tied to each hook; iris retractor holds edge of capsulorrhexis, providing countertraction; needle directed through ciliary sulcus and scleral wall; suture tied to itself (Goretex slippery, so use 0.12 tying forceps and needle holder to tighten knot); procedure repeated for opposite side; residual cortical material removed; IOL injected into capsular bag; viscoelastic removed |
| IOL CALCULATION AFTER REFRACTIVE SURGERY —David R. Hardten, MD, Adjunct Associate Professor of Ophthalmology, University of Minnesota Medical School, and Director of Research and Fellowship Program, Minnesota Eye Consultants, Minneapolis |
| Patient population: history of LASIK common (radial keratotomy rare); most patients had low to moderate myopia before refractive surgery |
| Impact of refractive surgery on corneal curvature: multifocal oblate cornea; curvatures unequal between front and back surfaces; calculation of IOL based on keratometry and axial length; measurement of corneal curvature affects power of implant |
| Measuring corneal curvature: measuring only anterior surface of cornea in patient with history of refractive surgery results in hyperopia postoperatively; manual keratometry—keratometer measures ≈3 mm of cornea; calculation of IOL based on measurements from steeper part of cornea results in underpowered lens; topography—samples multiple points of cornea, but lacks information about central portion of cornea and ignores differences in curvatures between front and back surfaces |
| Refractive change method: subtract refractive change after surgery from preoperative keratometry reading; note—stable refraction required before cataract; potential sources of error—availability of preoperative keratometry reading; accuracy of postoperative refraction |
| Contact lens method: obtain refraction without contact lens; place contact lens, trapping positive tear film between lens and cornea; refract again; add refractive error after placement of contact lens to contact lens base curve to calculate corneal curvature; potential sources of error—poor accuracy of refraction (eg, patients with hand-motion cataracts) |
| Corneal topography method: use raw data from topographer to find flattest area of cornea; use this reading for calculations of IOL; note—some machines give reading from flattest area automatically |
| Corneal tomography: Orbscan and Pentacam determine mean power of cornea by subtracting anterior from posterior curvature (use 3-mm mean total axial power on Orbscan); Pentacam adjusts multiple areas of cornea, likely improving accuracy |
| Regression formulas: calculate basic adjustments to power of IOL, based on historical method |
| Combined method: organize data from various methods (speaker uses unadjusted keratometry reading, refractive method, topography, Orbscan 3-mm zone method, and contact lens method) into spreadsheet; choose keratometry value that seems most accurate |
| Patient considerations: prepare patient for undercorrection or overcorrection; have patient sign consent form about increased risk for inaccuracy after previous surgery; educate patient about potential aberrations caused by cataract and those caused by refractive surgery; aim for emmetropia; note—if you aim toward myopia, you may have to flatten cornea further; if hyperopia results, you can steepen cornea and perform IOL exchange or piggyback IOL |
Educational Objectives
| The goal of this activity is to provide the clinician with information about advances in cataract surgery. After hearing and assimilating this program, the clinician will be better able to: |
 | 1. Discuss benefits associated with bimanual microincision phacoemulsification. |
| 2. Select appropriate instrumentation for performing bimanual microincision phacoemulsification. |
| 3. Manage patients with compromised zonules. |
| 4. Identify patients who would benefit from modified capsular tension rings (CTRs). |
| 5. Calculate power of intraocular lenses (IOLs) in patients with a history of refractive surgery. |
Suggested Reading
Adrean SD, et al: Intraocular lens calculation in a patient with previous penetrating keratoplasty and LASIK. Cornea 24:629, 2005; Dick HB: Closed foldable capsular rings. J Cataract Refract Surg 31:467, 2005; Goguen E: Perioperative pharmacology in cataract surgery. Insight 3:19, 2005; Hoffman RS, et al: New phacoemulsification technology. Curr Opin Ophthalmol 16:38, 2005; Kurz S, Dick HB: Spring constants of capsular tension rings. J Cataract Refract Surg 30:1993, 2004; Latkany RA, et al: Intraocular lens calculations after refractive surgery. J Cataract Refract Surg 31:562, 2005; Milla E, et al: Corneal endothelium evaluation after phacoemulsification with continuous anterior chamber infusion. Cornea 24:278, 2005; Paul T, Braga-Mele R: Bimanual microincisional phacoemulsification: the future of cataract surgery? Curr Opin Ophthalmol 16:2, 2005; Pesudovs K, et al: Effect of cataract surgery incision location and intraocular lens type on ocular aberrations. J Cataract Refract Surg 31:725, 2005; Preussner PR, et al: Topography-based intraocular lens power selection. J Cataract Refract Surg 31:525, 2005; Price FW JR, et al: Interim results of the United States investigational device study of the Ophtec capsular tension ring. Ophthalmology 112:460, 2005; Rosa N, et al: Double-K method to calculate intraocular lens power after refractive surgery. J Cataract Refract Surg 31:254, 2005; Saw SM, et al: Utility assessment among cataract surgery patients. J Cataract Refract Surg 31:785, 2005.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial relationship with the manufacturer or provider of any commercial product or service discussed. The following has been disclosed: Dr. Fine is a consultant for Advanced Medical Optics and Bausch and Lomb and receives support from Alcon Laboratories, Eyeonics, STAAR Surgical, Carl Zeiss Meditec, and Rayner; Dr. Cionni receives support from Alcon Laboratories and Morcher.
Drs. Fine and Cionni were recorded in Miami, at Cataract and Refractive Surgery Congress, sponsored by Bascom Palmer Eye Institute, and held February 25-26, 2005; Dr. Hardten was recorded in Seattle at 2005 Annual Meeting of the Washington Academy of Eye Physicians and Surgeons, held March 31 to April 1, 2005. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.
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