REACHING NEW PEAKS In Ophthalmic Surgery

GREAT MINDS DON’T ALWAYS PRACTICE ALIKETHINGS CANNOT CHANGE AND IMPROVE if they stay the same. That is why it is sometimes necessary tobreak away from the mainstream and try a different approach. If an alternate approach doesn’t turn out,then hopefully a lesson of some sort can be learned. Whether an off-label use or an alternate approach orsimply trying out something brand new, it doesn’t do anyone any good if the details aren’t shared.Now in its 25th year, the 2014 Reaching New Peaks in Ophthalmic Surgery meeting (formerly the ParkCity Symposium) continually strives to provide an environment in which cataract and refractive surgeonscan share their experiences and knowledge as well as openly discuss new techniques, controversies andmore. Course director Alan S. Crandall, MD, and co-directors Douglas D. Koch, MD, and Stephen Lane,MD, were actively involved as session moderators and presenters. The following pages contain the highlights of presentations from the meeting that these respected physicians found particularly interesting. Itis hoped that you find valuable information within this content and that you are able to apply it to yourown procedures.Coexistent Glaucomaand CataractAccording to Garry P. Condon, MD,the current glaucoma buzzwordis microinvasive glaucoma surgery(MIGS), which is cataract plus when combined with phacoemulsification/intraocular lens (IOL). Small-incision phacoemulsification and traditional trabeculectomy aretwo time-proven surgeries, but combiningthem invites the potential for undesirablecomplications, he explained.Ideally, performing a MIGS glaucomaprocedure with cataract extractionwill only minimally increase the risk ofcomplications, require minimal additionalmanipulation, and use the same incision.We continue to strive to increase the effectiveness of MIGS procedures and reducethe surgical learning curve.Below is a rundown of the MIGS devicesthat Dr. Condon discussed.The Hydrus Microstent (Ivantis) isan intracanalicular scaffold for the treatment of primary open-angle glaucoma(POAG) that can be performed duringcataract surgery using the same microsurgical incisions. In the United States, itis only available for clinical investigational use right now.The Hydrus Microstentdilates Schlemm’s canal for roughly threeclock hours in the nasal quadrant, isopen on the back side and fenestratedwindows on the meshwork side. It is atrue blue canal device—you can’t put itin the wrong location; if it’s not in the canal, then it’s sitting on the iris or on thefloor because there’s no place else in theeye for this to go.The inserter is 8-mmlong, has a spade-like tip and a snorkelat the tail end, which sits in the anteriorchamber and allows fluid direct accessinto the scaffold-opened area.In a six-month prospective EuropeanTrial1 of Hydrus surgery alone (n 40)and Hydrus combined with cataractsurgery (n 29), there was a 21.8 percentreduction in IOP for device only, compared to 26.1 percent reduction in IOPfor Hydrus surgery plus cataract IOL.“With infusion,the ophthalmicviscosurgical device cancome out pretty rapidly,so I hang the bottle high.That way, no matter what,I still have a nice clearview of the landmarks. ”–Garry P. Condon, MDThe CyPass Micro-Stent (Transcend Medical) is an investigational micro suprachoroidal stent. It’s a polyamideand has microperforations or fenestrations all along the tube of the device.Thetip opens up the gap between the scleraand the iris and the retention ring keepsit locked at the point where the ciliaryREVIEW OF OPHTHALMOLOGY0614 NewPeaks me10.indd 3July 2014body fuses to the sclera or scleral spur.The CyPass uses an ab interno approachthrough a small incision and spares theconjunctiva, sclera and trabecular meshwork. According to Dr. Condon, it reallyrepresents a controlled cyclodialysis.In a multicenter study of 81 patientsby Transcend Medical, there was a meandecrease of 29 percent in IOP and twointraoperative hyphemas, so it is really anontraumatic event.2 There’s currently aPhase III FDA trial underway (COMPASS).A total of 505 cataract patients with mildto moderate glaucoma have been enrolledand will be followed for two years.The Trabectome (NeoMedix Inc.) isa minimally invasive surgical device thatcan be used for ab interno trabeculectomy.It’s done under infusion, which is nice because if there is any blood, it washes away.Of all of these devices, only the Trabectome is FDA approved for more advancedglaucoma and without limitations.“With infusion, the ophthalmic viscosurgical device can come out pretty rapidly,so I hang the bottle high,” Dr. Condonexplains.“That way, no matter what, I stillhave a nice clear view of the landmarks.”The iStent Trabecular MicroBypass Stent (Glaukos Corp.) is anFDA-approved trabecular micro-bypasstechnology that improves the eye’snatural fluid outflow to safely lower eyepressure by creating a permanent opening in the trabecular meshwork. It is 36/20/14 1:38 PM

implanted through a clear corneal incision using a disposable inserter. A studyby Samuelson, et al, compared reductionin IOP following iStent implantation andcataract extraction (n 100) versus cataract extraction alone (n 106).3 Changein IOP from washout baseline to oneyear: mean (SD) was -8.4 mmHg (3.6)for iStent cataract and -8.5 mmHg(4.3) for cataract extraction only. Another study compared the same for twoyears and found the change in IOP fromwashout baseline to two years: mean(SD) was -8.3 mmHg (2.9) for iStent cataract (n 98) and -7.4 mmHg (3.3) forcataract extraction only (n 101).4therefore, the angle of attack increases thefurther away you go from that straightahead view, and so the tendency to sort of“dig” things into the angle is unavoidable.1.Tetz M, et al. Presented at: ESCRS Annual Meeting; Sept. 2011; Paris.2. Ianchulev T, et al. Presented at AAO; 2010;Chicago.3. Samuelson TW, Katz LJ,Wells JM, et al; US iStentStudy Group. Randomized evaluation of thetrabecular micro-bypass stent with phacoemulsification in patients with glaucoma andcataract. Ophthalmology. 2011;118(3):459-467.4. Craven ER, Katz LJ,Wells JM, et al.; iStentStudy Group. Cataract surgery with trabecularmicro-bypass stent implantation in patientswith mild-to-moderate open-angle glaucomaand cataract: two-year follow-up. J CataractRefract Surg. 2012;38(8):1339-45.GENERAL ADVICEDr. Condon shared that for any of this,gonioscopy is key, and being able toidentify your landmarks is important.However, the view of the angle canbe significantly different than at theslit lamp when you’re in the operatingroom, particularly if you’ve just donecataract surgery on the eye and thecornea is less than clear. Guttata havean incredible effect on the ability toidentify and really see clear detail inthe angle structures. Blood reflux in theSchlemm’s canal can also be helpful, butis not always present.Dr. Condon also noted that the fulcrumof the implantation process with any ofthese devices is really at the corneal incision, and not in the pupil or central zone;iPhone Slit LampPhotography andSurgical VideographyBaylor College of Medicine assistantprofessor Mitchell P. Weikert, MD,in collaboration with ChristianHester, MD, covered the topic of ophthalmic photography and videography.He pointed out that it is increasing inimportance and utility with the adoption ofelectronic medical records (EMRs), so themore physicians can do with photography,the better off they’ll be. Of course, yourtypical photographic equipment is a bitexpensive and cumbersome and requiresdedicated space and trained personnel. Fortunately, smartphones offer a cheaper andmore flexible alternative, and Dr. Weikertexplained how. He recommends a minimum of 5 megapixels, but adds that “really,the more the better.” He also pointed outthat a telephone contract isn’t necessary touse a phone’s camera as long as you havewi-fi connectivity.ADAPTORS & APPSDr. Weikert uses a slit lamp adaptor fromEyePhotoDoc (Haag-Streit BQ and Advanced I-Illuminator), which goes directlyover the slit lamp ocular. It has a little postso you can put it on the left ocular and itstabilizes it so it sits nice and horizontal (orvertical, but you get a little bit more realestate for your efforts in landscape mode).He shared that, with a light, it costs about 500, which, in the grand scheme of ophthalmic photography, is not that expensive.The adaptor without the light costs about 350 and is available for iPhones as well asthe iPad and iPad mini.He pointed out that Zarf Enterprises andOculoCAM also have adaptors for iPhonesand Android devices and noted that ifyou’re more of a do-it-yourselfer, you cancreate your own adaptor with the cap froma Gillette shaving foam travel pack container, the rubber disc from an empty CDstack box and rubber-based adhesive.According to Dr. Weikert, ProCamerahas a versatile, but inexpensive photography app. “The advantage of the ProCamera app,” he says, “is that it allows youto separate your exposure and focus andSURGICAL VIDEO PROGRAM BUILDS CONFIDENCEWITH UNFAMILIAR PROCEDURESDavid A. Crandall, MD, of Henry Ford OptimEyes Super Vision Center in Troy, Mich., spoke to attendees about a program he is putting together with colleagues. The program is a website and an app thatcontains short (three minutes or less), educational videos that summarize key points and pearls in surgery. “The idea is for surgeons to review a video—either online or on their mobile phone—of an unfamiliarprocedure before or during surgery to gain some confidence performing it themselves,” he explained.Right now, Dr. Crandall says the program is mainly an educational tool for residents, but in time, they’lladd increasingly complex topics. The basic categories will cover every step of cataract surgery, including subcategories such as different ways of implanting three-piece lenses or putting in anterior chamberlenses with forceps and without. He clarified that the program won’t show full cases or perfect cases, asthe point is to expose surgeons to simple procedures they will realistically run into. Additionally, all videoswill be reviewed before being added to the site and the ultimate goal is to have it hosted on the AmericanSociety of Cataract and Refractive Surgery’s website.REVIEW OF OPHTHALMOLOGY0614 NewPeaks me10.indd 4July 2014 46/20/14 1:38 PM

not an optical zoom, so you may lose afew pixels,” he said.IOL Calculations: Why WeCan’t Get Any BetterDifference in photo quality between five-megapixel iPhone 4 (left) versus the eight-megapixeliPhone 4s (right).move them independently.” He also madea point about illumination, noting that,“if you just use a slit lamp and you putthe broad beam on, you can’t light thewhole area of the eye. It’s about 8mmmaximum.” But, he explained that ifyou put a diffuser on and flip it up, youcan get broader illumination. He addedthat a transilluminator works really well,explaining that youcan hang it on the dial for the slit lamp orhave a scribe or tech hold it for you. Or,you can use a clip-on light source. Histransilluminator is from EyePhotoDoc,and he says it has a blue light and awhite light, allowing him to also do somefluorescein photographs. Additionally, theinstrument also has a little rheostat, so hecan vary the illumination.THE VALUE OF VIDEOBefore ending his talk, Dr. Weikertcommented that taking a slit lamp videois helpful—especially in the operatingroom (OR). “We all know that just seeinga static image is not always as valuable asseeing motion and being able to maneuverthe light,” he said. The ProCamera app iscapable of shooting video as well as taking still photographs, and you can do thatwith the app in the iPhone as well. TheMagnifi iPhone photoadapter case is useful in the OR, and he says it fits wellon a Zeiss scope with f125 oculars. Orionalso has an adapter (Orion SteadyPixTelescope Photo Adapter) that clips ontothe ocular and works well with a LeicaM840 scope.TAKE-HOME POINTSiPhone slit lamp photography and videography is a nice, inexpensive, portableand efficient alternative for ophthalmicphotography, Dr. Weikert concluded.He added that physicians can bill for itjust like any ophthalmic photography,and said it can be used to review surgical videos, etc. “It may be applicable intelemedicine, as you could FaceTime withit,” he postulated. “And it might be useful for screening clinics that are mannedby nonMDs.” Keep HIPAA in mind, Dr.Weikert cautioned, and don’t record anyimages with identifying information (e.g.,facial picture, date of birth). You can usethe medical record number to referenceimages. His final advice: don’t underestimate using the zoom feature on youriPhone when it’s on the eyepiece. “Justremember, you’re doing a digital zoom—Transilluminator (left) and clip-on light source (right).REVIEW OF OPHTHALMOLOGY0614 NewPeaks me10.indd 5July 2014“These days, patients expect painless,complication-free surgery at minimal cost and with instant excellentuncorrected visual acuity and minimaldowntime,” Mitchell P. Weikert, MD, beganhis second presentation. Thus, he submitted, good, accurate intraocular lens (IOL)calculations are absolutely necessary formeeting patients’ expectations.Dr. Weikert said that when many ophthalmologists consider IOL calculations,the formula is sort of a big black box. “Wetake measurements and enter them into thecalculator, which spits out the lens powerthat we’re supposed to implant in our patient,” he stated. He believes it’s valuable tolook into this black box because it containsother black boxes that have limitations andmake assumptions that can effect our results.But first, Dr. Weikert discussed IOL powercalculation formulas.IOL POWERCALCULATION FORMULAS“Most of the current IOL calculation formulasthat we use today are still based on geometricoptics and principles derived in the 1960s and1970s,” he admitted. “We have the refractiveindex outside the eye and a single refractiveindex inside the eye,” he continued. “And wehave our target refraction, the corneal powerand the power of the IOL with our imagetargeted on the retina.” Several distances mustalso be considered: the vertex distance fromthe target refraction to the eye, the anteriorchamber depth (ACD) from the anteriorcorneal surface to the lens plane, and then theaxial length from the interior corneal surface tothe retina. So this formula models the eyes asthree refractive surfaces represented by the target refraction, the cornea, and the IOL power.As Dr. Weikert noted, basically, you havelight coming into the first surface, whichcreates an image that becomes the object forthe second surface, which creates an imagethat becomes the object for the third surface, 56/20/14 1:38 PM

which hopefully is on the retina. “That givesus the vergence formula,” he added, “which isthe basis for the most common IOL calculation formulas used today.”He noted that the effective lens position (ELP), true corneal power, index ofrefraction, and the axial length are all otherblack boxes, which he went on to discuss.THE “OTHER” BLACK BOXESELP. This is the estimate of the positionwhere the IOL will sit in the eye. It’s not aphysical distance; it’s the effective refractiveplane of the lens. Dr. Weikert noted that ELPchanges with axial length, so this black boxhas a lot of potential for improvement. Thefollowing formulas rely on ELP.Dr. Weikert explained that the Holladay1 formula is based on corneal height andincreases the base of the cornea proportionally with axial lengths, according toaverage axial lengths and average angleto-angle distances. He added that it also includes the surgeon factor (an optimizationconstant), which is the difference betweenthe corneal height and the effective IOLplane. He explained that the Holladay 1 hasa very shallow linear relationship, as ELPincreases with axial length. He then pointedout that one source of error lies in the factthat although ACD will increase as the eyegets bigger and the axial link increases, thesurgeon factor is a constant number andthus stays the same.The SRK/T formula uses the same model,Dr. Weikert noted. “It changes how it increases the base of the cornea depending onthe axial length,” he explained. “The SRK/Tformula has something called an offset, whichis basically the same as the surgeon factor.The SRK/T offset can be calculated from theIOL’s A constant, so you can directly convertan A constant into a surgeon factor for ELP.”He finished the roundup of formulas withthe Hoffer Q, an empiric derivation dependenton axial length and corneal power to createa personalized A constant as its optimizationfactor, and the Haigis, another empiric derivation, that is a linear model that depends onaxial length and preoperative ACD rather thanon corneal power.“All of these ELP formulas are different,”Dr. Weikert pointed out. “But they all get putback into that same Binkhorst equation. Andbecause they all have different shapes, so youwould expect them to produce very differentresults when put into that same equation.”Corneal Power. He reminded attendees that most commonly, corneal power ismeasured indirectly via an image reflected offthe tear film. “The radius of curvature is thencalculated from this image,” he added.“Most models assume that the corneais a spherocylinder,” he continued. “Wealso have to take into account the factthat the size of the zone that we measurevaries from device to device, and thosezones will vary with the curvature.” Dr.Weikert explained further that a flattercorneal is going to measure a larger area,and a steeper cornea is going to measurea smaller area. “And we implant thoseresults back into the same formulas,” henoted. “Most devices that we typically usestill measure the anterior surface only andreduce the index of refraction to accountfor the negative value of the posteriorsurface. And they assume a fixed frontto-back curvature ratio for the cornea.Corneal power also varies with pupil size,”he reminded his colleagues.Index of refraction. The cornea is aprolate surface, steeper in the center, flatterin the periphery. “When you have incidentlight coming in, overall the effect is tohave positive spherical aberration of thecornea with peripheral rays are refractedmore strongly than paraxial rays, so youend up with a little overall myopic shift asyou sample larger areas of the cornea,” Dr.Weikert explained.In the United States, ophthalmologistsuse 1.3375 for our keratometers, whichsimply models the cornea as the sum oftwo refractive surfaces with a curvatureratio equal to the Gullstrand ratio. In Europe, they use 1.3315 because their modelfactors in the corneal thickness. Newerdevices can measure the front and backcornea, but they rely on measuringelevation, which is more difficult to dobecause you need much higher resolutionto extract curvature information.Axial length. This is one of the mostREVIEW OF OPHTHALMOLOGY0614 NewPeaks me10.indd 6critical steps in calculating IOL power,according to Dr. Weikert. “Small errorscan have large effects on our postoperativeresults and errors about 0.1 mm can have0.27D of error in the spectacle plane,”he stated. “Optical biometry has reallyimproved this over the last few years. It’snon-contact; we have high resolutions.But compared to ultrasound, we’re measuring different distances.” He explainedthat with optical biometry, we are measuring to the retinal pigment epithelium,whereas with ultrasound, we’re only measuring to the internal limiting membrane.Fortunately, the machines take that intoaccount and compensate for it.Dr. Weikert advised the doctors in theaudience to remember that these optical biometers are calibrated to ultrasound, whichis calibrated to an average population ofpatients, and pointed this out as anothersource of error. He explained, “You’retaking a direct measurement and changingit to agree with a bunch of other patientswho are going to have variation in and ofthemselves.”IOL Design. This is the final black boxDr. Weikert spoke about. The refractiveeffect of an IOL depends on the shape ofthe front and back surfaces, asphericityetc., where the lens lies in the eye, theindex of refraction, refractive power, thethickness of the lens, the spherical aberration, and the manufacturing tolerance.He noted that the International StandardsOrganization permits up to 0.3 up to 1.0Dof error in a lens, though he added thathe believes manufacturers have a muchtighter tolerance than this.WHAT NEEDS TO HAPPEN?In conclusion, Dr. Weikert admitted that unfortunately, there will always be error in ourmeasurements. He added that, “the biggesthurdle is predicting the postop position ofthe IOL. We need better formulas that moreclosely model the human eye, and we needto go beyond the paraxial approximation.We also need to account for aberrations andimplant an accurate corneal power. I thinkthe ultimate answer may lie in postop adjustment of the cornea or the IOL power.”J

Samuel Masket, MD, is clinical professor of Ophthalmology at the David Geffen School of Medicine, Jules Stein Eye Institute, University of California, Los Angeles, a past president of the American Society of Cataract and Refractive Surgery. . TearScience, SMI, Visi