ZEISS Progressive Individual® 2: - Luzerne Optical Labs

Personalized Lenses by ZEISSZEISS Progressive Individual ® 2:The Most Customized ZEISS Progressive AvailableBy Darryl Meister, ABOMSince the advent of “free-form” or “digital surfacing” technology, a myriad of new lens designs has been introduced. Although thistechnology can potentially deliver unsurpassed wearer satisfaction by eliminating the optical constraints of ordinary lenses, wearers willonly realize meaningful visual benefits with this new category of lenses if the lens design has been suitably tailored to his or her uniquevisual requirements. Carl Zeiss Vision—a leader in customized lenses—now offers ZEISS Progressive Individual 2, a customized progressivelens that extends the proven performance of ZEISS Individual through the application of several new and innovative design features.Next-Generation Optical PerformanceCarl Zeiss Vision pioneered an exciting new category of lenses thatcombines “real-time” optical design with precision digital surfacingtechnology. Carl Zeiss Vision has remained at the leading edge ofthis technology with a variety of optically customized lens solutionsthat continue to represent the most advanced progressive lensesavailable. Ongoing advancements in research and developmenthave stimulated continuous product improvement by extendingthe optical performance of these lenses with additional forms ofcustomization, further closing the gap between lens designs andthe unique vision requirements of eyeglass wearers.Eyecare professionals are increasingly aware of the potential visualbenefits of lenses optically designed in real time, immediatelyprior to fabrication using a “free-form” or “digital surfacing”manufacturing platform. Because ordinary progressive lenses areproduced from semi-finished lens blanks that are factory-moldedin mass quantity, these lenses cannot account for the visualrequirements of individual wearers. Due to the massive productdevelopment and inventory costs associated with semi-finishedprogressive lenses, each lens design is typically available in onlya handful of combinations of base curve and addition power.Moreover, these lenses are typically offered in only a single,general-purpose design for either large or small frame sizes.Although certain wearers may enjoy the intended opticalperformance in ordinary progressive lenses, many wearers musttolerate reduced optical performance as their prescription orfitting requirements depart from the assumptions used to designthe semi-finished lens blanks (Figure 1). Standard and shortcorridorprogressive lenses also accept optical compromises inorder to minimize the number of lens blanks required. Opticalperformance can be maximized, however, by tailoring the opticsof the progressive lens design to the unique visual requirements ofthe individual wearer.ZEISS Progressive Individual 2 represents the latest evolution ofthe award-winning ZEISS Individual progressive lenses. Uniquelycustomized for the visual requirements of each wearer, Individual 2enhances the proven performance of Individual with two additionalforms of customization for the wearer:1. Visual Profile. The proportions of the viewing zones of thelens design can now be altered to satisfy the particular visualdemands of the wearer using EyeFit technology.2. Ocular Anatomy. More precise calculations of the position ofthe center of the wearer’s eye improve the visual clarity andbinocular alignment of the lens design using CORE technology.+25+20+15+10+50–5–10–15–20–25TYPICAL +3.00 SPH LENS2.01.51.02.50.5+3.00 SPH, +2.00 ADD0.52.51.01.52.0+25+20+15+10+50–5–10–15–20–252.0DIFFERENT PRESCRIPTION1.00.50.5COMPROMISEDPERIPHERY2.51.50.52.51.01.52.0+25+20+15+10+50–5–10–15–20–25DIFFERENT FITTING POSITION2.01.00.5EFFECTIVE RX:+3.39 –0.36 × 29+3.00 –1.50 × 135 +3.00 SPH, 15° WRAP1.50.52.51.01.52.0Figure 1. Plots of ray-traced astigmatism—asperceived by the actual wearer—demonstratethat the optical performance of ordinaryprogressive lenses is sensitive to the specificprescription and position of the fitted lens.

Personalized Lenses by ZEISSReal-Time Optical Design with Precision Digital Surfacing» Individual 2 integratesZEISS Progressive Individual 2 is uniquelyprecision digital designed for each wearer using Carl Zeisssurfacing with real-timeVision’s proprietary optical design engineoptical designand patented free-form technology. 1 Usinginformation supplied by the eye care professional, including thewearer’s prescription, fitting geometry, frame information, andvisual profile, this powerful optical design engine calculates a newlens design in “real time,” immediately prior to fabrication. Thenewly designed lens surface is then transmitted to state-of-the-artfree-form surfacing equipment that precisely replicates the surfacedesign directly onto the lens blank using precision digital surfacing.This sophisticated optical design process begins by managing theglobal geometry of the lens design. The ideal corridor length forthe wearer’s visual profile and chosen frame size is determined inorder to maximize the utility of the central viewing zones basedupon the visual demands of the wearer, while ensuring consistentreading utility in any frame. Smooth transitions in power andastigmatism are maintained in order to avoid the rapid changes inpower that would otherwise result in excessive image swim as wellas greater levels of “high-order” wavefront aberrations. The inset ofthe near zone is also precisely calculated using the wearer’s oculardimensions, prescription requirements, and position of wear.Next, the optical performance of the lens design is precisely refinedthrough advanced optical optimization techniques. Using computerray tracing, the “low-order” wavefront aberrations—unwantedastigmatism and defocus—produced by the wearer’s specificcombination of ocular anatomy, prescription requirements, andfitting parameters are calculated over the lens. The initial opticalperformance of the calculated lens is then compared against theperformance of the ideal or “target” lens, while the optics of theactual lens design are fine-tuned on a point-by-point basis, usingcomplex aspherization algorithms, until the final lens reproducesthe desired optical performance as closely as possible (Figure 2).POINT-BY-POINTOPTICAL CONTROLFigure 2. Using the wearer’s exact prescription and fitting parameters, the optics ofeach Individual 2 lens is manipulated on a point-by-point basis.As one of the earliest pioneers in free-form lens technology, CarlZeiss Vision has comprehensive experience and expertise in freeformlens production. Carl Zeiss Vision’s Precise-Form technologyintegrates patented free-form technology with extensive processengineering and continuous quality control. Engineers at Carl ZeissVision manufacture and evaluate hundreds of lenses, while finetuningdozens of free-form process parameters, in order to ensurethat each lens in each material consistently delivers unsurpassedsurface quality and optical performance (Figure 3).Some so-called free-form progressive lenses rely on lens blankswith some or all of the progressive optics placed on the frontsurface using ordinary lens molding techniques. Using Precise-Formtechnology, on the other hand, the ZEISS Progressive Individual 2lens design is directly surfaced onto the lens blank by a precisionfree-form generator. This ensures extremely accurate replication ofthe progressive lens design. Placing the progressive optics on theback surface of the lens also maximizes the fields of clear visionby locating the viewing zones closer to the eyes while minimizingunwanted magnification effects that result in skew distortion.Figure 3. Unlike free-form surfacing withoutsufficient process control, which can result inoptical errors over the lens surface, Precise-Form technology integrates patented free-formtechnology with rigorous process engineeringin order to ensure pristine lens surfaces withincredibly accurate optical powers. Dozens offree-form surfacing and polishing parameters—including the speed, duration, and pattern ofmovement—are carefully adjusted and thentested for a range of prescription and lens designcombinations in every available lens material.0.500.370.250.120.00POWER ERROR (D)2015105LENS X,Y (MM)0-5-10-15-20-20-15-1020151050-5POWER DEVIATIONSACROSS SURFACE≥ 0.12 D0.500.370.250.120.00POWER ERROR (D)2015105LENS X,Y (MM)0-5-10-15-20-20-15-1020151050-5MINIMAL ERRORSACROSS SURFACE≥ 0.12 DFREE-FORM SURFACING USING POOR PROCESS CONTROLZEISS CUSTOMIZED LENSES USING PRECISE-FORM TECHNOLOGY2Contact: Luzerne Optical Laboratories LTDat 1-800-233-9637 or on the web at www.LuzerneOptical.com

Personalized Lenses by ZEISSCustomized for the Wearer’s Visual ProfileThe visual demands of presbyopes vary considerably from personto person. Some occupations and leisure activities involve moredynamic distance vision or mid-range vision, whereas some officework and other sedentary activities involve more up-close vision.For example, a commercial driver requires a usable periphery alongwith a clear view of the dashboard, whereas a teacher requiressharp vision up close to review and grade papers. Unfortunately,due to the blending regions necessary to produce a progressivesurface, increasing the size of either the distance, intermediate, ornear zone generally comes at the expense of decreased utility inother zones of the lens. The ideal progressive lens for a given wearerwill therefore depend upon the visual demands specific to his orher occupation or vocation. In fact, research has demonstrated thatpreference for the relative balance between the viewing zones ofa progressive lens varies with the visual demands of the wearer. 2Until recently, however, presbyopes had no choice but to wearprogressive lenses that often failed to reflect their unique visualprofile—the visual requirements that characterize their mostcommon viewing tasks. Due to the product development andinventory costs associated with mass production, ordinaryprogressive lenses are designed to offer “general-purpose” utility,with a balance among the viewing zones suitable for the averagewearer, in order to offer a single lens that appeals to the mostwearers. But with the introduction of Individual 2, presbyopes cannow select a ZEISS lens designed specifically for their own visualprofile. Once the relative visual demands of the wearer have beenassessed, the balance between the distance, intermediate, andnear zones of each ZEISS Progressive Individual 2 lens is tailored tothe wearer by manipulating the global geometry of the lens designin real time using EyeFit technology.Individual 2 Balanced ProfileFor most wearers, with a diverse range of visual demands at far,mid-range, and up-close distances, ZEISS Progressive Individual2 with the default Balanced option is the optimal solution. Thislens design offers a balance between equally generous distance,intermediate, and near zones (Figure 4). Candidates for this lensdesign include presbyopes who do not express a particular needfor additional dynamic, mid-range, or up-close utility or presbyopeswho have been completely satisfied with general-purpose lenses.+1.75PLANO RX, +2.00 ADDITIONSIMULATED FIELDS OF USABLE VISIONFigure 4. Individual 2 offers balanced visual utility.Individual 2 Intermediate/Dynamic ProfileFor wearers with either intensive visual demands at mid-rangedistances or who rely on dynamic distance vision, Individual 2Intermediate (“2I”) is the optimal solution. This lens design offers upto a 25% larger intermediate zone and a softer periphery with lessunwanted astigmatism (Figure 5). 3 Candidates include presbyopeswho routinely perform mid-range viewing tasks at 24 to 36 inches,such as computer use, or presbyopes who frequently engage invisually dynamic activities, such as driving or many sports.LARGER INTERMEDIATE+1.75PLANO RX, +2.00 ADDITIONSIMULATED FIELDS OF USABLE VISIONFigure 5. Individual 2I offers enhanced mid-range utility and dynamic utility.Individual 2 Near ProfileFor wearers with intensive visual demands at up-close distances,Individual 2 Near (“2N”) is the optimal solution. This lens designoffers up to a 30% larger near zone that is both wider and higherin size, providing easier access to more reading utility (Figure 6). 3Candidates for this lens design include presbyopes who routinelyperform sustained reading or up-close viewing tasks at 12 to 24inches and presbyopes who wear their progressive lenses primarilyfor reading with less concern for distance vision utility.LARGER NEAR+1.75PLANO RX, +2.00 ADDITIONSIMULATED FIELDS OF USABLE VISIONFigure 6. Individual 2N offers enhanced up-close utility.3

Personalized Lenses by ZEISSCustomized for the Wearer’s Ocular Anatomy» Optical performance isThe movements of the eye as the wearersensitive to the center changes gaze resemble those of a balland-socketjoint with a center of rotationof rotation, whichvaries with prescriptionlocated near the center of curvature of theposterior globe of the eyeball. The location of the ocular center ofrotation varies with the anatomical length of the eye, which in turnusually varies with the refractive error of the eye. 4 Hyperopic eyes(with plus prescriptions) are typically shorter than emmetropic eyes,and myopic eyes (with minus prescriptions) are typically longer.Consequently, the center of rotation varies with refractive error.The optical performance of a lens design is sensitive to the locationof the ocular center of rotation. The distance from the back vertexof the lens to the center of rotation of the eye is used during raytracing to calculate the angles of incidence and refraction associatedwith the line of sight as the eye rotates to different angles of gazewhile looking through various parts of the lens. Consequently, raytracing computations to minimize power errors from the desiredprescription rely on the correct location of the center of rotation(Figure 7). The calculation of the inset of the progressive corridorand near zone of the lens also rely on the location of the centerof rotation, since the eye turns about this point when converging.The location of the center of rotation is therefore a criticalparameter in lens design. Significant differences between the centerof rotation used for design calculations and the actual center of thewearer’s eyeball can result in power errors that can easily exceedthe depth of focus of the eye. Errors in the estimated distance tothe ocular center of rotation can increase unwanted astigmatismin the periphery of a progressive lens and reduce the utility of thecentral viewing zones. Moreover, the binocular alignment of theintermediate and near zones is disrupted. Although the importanceof the ocular center of rotation and the potential variation dueto refractive error have long been recognized by lens designers, afixed distance to the center rotation has often been utilized whendesigning spectacle lenses, regardless of the intended prescription. 5A fixed distance of 13.5 mm behind the plane of the cornea ofthe eye is assumed when designing many spectacle lenses. Thisdistance represents the average distance to the center of rotationfor many theoretical or “schematic” eye models with no refractiveerror (emmetropia). The distance to the ocular center of rotationcan vary considerably, however, among actual human subjects,as demonstrated by anatomical measurements using an opticalbiometer, such as the IOLMaster ® by Carl Zeiss Meditec (Figure 8).CORNEA TO CENTER OF ROTATION (MM)CENTER OF ROTATION MEASUREMENTS OF ACTUAL SUBJECTS17161513.5 MM FIXEDDISTANCE COMMONLY14USED IN LENS DESIGN131211N = 30810−10 −9 −8 −7 −6 −5 −4 −3 −2 −1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10SPHERICAL EQUIVALENT OF REFRACTIVE ERROR (D)+2MMFigure 8. Anatomical measurements of the actual distance to the center of rotationusing an optical biometer vary considerably with refractive error (data on file).For the past forty years, lens designers at Carl Zeiss Vision haveemployed a sophisticated algorithm to calculate the location of theocular center of rotation of the eye for different refractive errors,referred to as Center of Rotation Evaluation (CORE) technology.Recently, however, the combination of emerging lens manufacturingtechnologies with extensive anatomical measurements of actualpresbyopes has afforded increasingly accurate refinements to theCORE algorithm. Now, the exact prescription for each wearer canbe incorporated into the CORE algorithm, prior to fabrication usingfree-form or digital surfacing. The new CORE algorithm utilized withZEISS Progressive Individual 2 lenses is up to 50% more accurate.The estimated distance to the center of rotation will fall within ±1mm of the actual anatomical measurement for 99% of all wearers.−2MMFigure 7. Because the length of the eyeball typicallyvaries with refractive error, the distance from thecornea to the center of rotation of the eye also varieswith refractive error, causing the line of sight toform differing angles of incidence with the lens atthe same linear distance from the fitting point as theeye rotates, which must be taken into account duringcomputer ray tracing in order to achieve the desiredoptical performance.SAMEVERTEX CENTERSHORT37°CoRSAMEVERTEX MEDIUMCENTER35°CoRSAMEVERTEX33°LONGCENTERCoRHYPEROPE: SHORT EYE EMMETROPE: MEDIUM EYE MYOPE: LONG EYE4

Personalized Lenses by ZEISSCustomized for the Wearer’s Prescription Requirements» Residual aberrationsWhen the wearer looks obliquely throughproduce blur that the peripheral regions of a spectacle lens,restricts the field ofoptical aberrations occur that result in errorsclear visionfrom the desired focus. Lens aberrationssuch as oblique astigmatism create unwanted sphere power andcylinder power errors in the periphery. These unwanted powererrors produce blur, which degrades image quality and narrowsthe field of clear vision for the wearer (Figure 9). In theory, eachprescription combination requires a unique base curve or opticaldesign in order to eliminate these lens aberrations completely.Ordinary semi-finished lenses, however, are only available in alimited number of base curves due to the mold making and inventorycosts associated with mass production. Typically, each base curvewill deliver optimal optical performance only for sphere powerslocated near the center of the prescription range associated witheach base curve. Other prescription powers will suffer from residualaberrations because of this compromise. Moreover, when theprescription contains cylinder power, no conventional base curveor aspheric design can simultaneously eliminate the aberrationsproduced by both the sphere and cylinder powers of the lens.The optical effects of lens aberrations are exacerbated in progressivelenses. Oblique astigmatism interacts optically with the surfaceastigmatism of the progressive lens design, causing the zones ofclear vision to shrink. Lens aberrations can also cause the viewingzones of a progressive to become distorted and shifted from theirideal location as certain clear regions of the lens become blurred,while other regions of unwanted astigmatism actually becomeclearer. This distortion of the shape and location of the centralviewing zones disrupts binocular vision through the lenses.ZEISS Progressive Individual 2 is fully customized to the uniqueprescription requirements of each wearer. Each Individual 2 lensis optically optimized online by Carl Zeiss Vision’s optical designengine using the wearer’s exact prescription requirements (Figure10). By fine-tuning the optical design of the lens for the exactprescription, residual lens aberrations are virtually eliminated,resulting in up to 50% wider fields of clear vision. 3 Thus, wearers willenjoy the widest fields of vision possible, regardless of prescription.Furthermore, unwanted changes to the location and shape of theviewing zones are also eliminated, preserving the binocular utilityof the lenses with wide, symmetrical fields of view (Figure 11).SMALL, SHIFTEDVIEWING ZONESINTENDEDVIEWING ZONESFigure 9. With ordinary lenses, the field of clear vision may be significantly reducedand distorted by uncorrected lens aberrations for many prescriptions.Figure 11. Individual 2 is precisely customized for the wearer’s exact prescriptionrequirements, which ensures wide, symmetrical fields of clear vision.Figure 10. Ray-traced optical astigmatismcomparison: Because each Individual 2 lensis designed in real time, the optics of the lensdesign can be optically optimized to the exactprescription requirements of the wearer,ensuring that every lens performs exactly asintended, with no residual optical aberrationsthat could otherwise reduce and distort theclear fields of vision.+25+20+15+10+50–5–10–15–20–25TARGET PERFORMANCEOF IDEAL PRESCRIPTION1.01.50.52.52.02.0PLANO RX, +2.00 ADDITION0.52.51.01.5+25+20+15+10+50–5–10–15–20–25INITIAL PERFORMANCEWITH ACTUAL PRESCRIPTION0.51.01.5COMPROMISEDOPTICS2.00.50.51.00.51.01.52.0+25+20+15+10+50–5–10–15–20–25FINAL PERFORMANCEAFTER CUSTOMIZATION+3.00 –1.50 × 135, +2.00 ADDITION +3.00 –1.50 × 135, +2.00 ADDITION1.52.01.02.50.5OPTIMUMOPTICS2.50.51.51.02.0Contact: Luzerne Optical Laboratories LTDat 1-800-233-9637 or on the web at www.LuzerneOptical.com5

Personalized Lenses by ZEISSCustomized for the Wearer’s Fitting Parameters» The position of wearThe position of wear is the position of thecan have a significant fitted lens on the wearer’s face, includingimpact upon opticalthe pantoscopic tilt, face-form wrap, andperformancevertex distance of the lens as it is worn.Spectacle prescriptions are typically determined using refractorheador trial-frame lenses that are positioned perpendicular to thewearer’s lines of sight. Normal eyeglass frames, however, generallyleave spectacle lenses tilted with respect to the wearer’s lines ofsight. Unfortunately, tilting a lens introduces oblique astigmatism,which results in unwanted power changes over the lens. Therefore,the position of wear can have a significant impact upon the opticalperformance of a progressive lens (Figure 12).During the optical design process used for Individual 2, the positionof wear of the fitted lens is modeled using ray tracing to applythe necessary optical corrections over the lens (Figure 13). If thewearer’s pantoscopic tilt, face-form wrap, and vertex distance aresupplied, the optics of each ZEISS Progressive Individual 2 lensdesign will be precisely customized for this exact position of wear.Wearers will therefore enjoy the best optical performance possible,with improved vision quality through the central viewing zones inparticular, regardless of their unique fitting requirements.“NEAR” OBJECTAT INFINITYINSTRUMENTPERPENDICULARTO LENS BACKFOCIMETER MEASUREMENTREADING DISTANCEVERTEXTILTPOSITION OF WEARFigure 14. Although ordinary progressive lenses are often designed to exhibit thespecified optical powers only when measured using a focimeter, Individual 2 isdesigned to provide the specified optical powers in the actual position of wear.Ordinary progressive lenses are often designed to exhibit thespecified optical performance when measured using a focimeter(Figure 14). Because ZEISS Progressive Individual 2 is designed toprovide the wearer with the prescribed optical performance in theactual position of wear, however, small differences from the originalprescription are required at the distance and near verificationpoints of the lens. These power adjustments are supplied as acompensated prescription. Prescription compensation maximizesthe visual benefits of optical customization for the position of wear,resulting in even wider, clearer central viewing zones (Figure 15).UNWANTEDPOWER CHANGESINTENDEDPRESCRIPTION+3.00 SPH RX15° PANTO15° WRAP13MM VERTEX+3.00 SPH RX15° PANTO15° WRAP13MM VERTEXFigure 12. Vision may be significantly degraded by the position of the fitted lens.Figure 15. Individual 2 is customized for the wearer’s fitting parameters.Figure 13. Ray-traced optical astigmatismcomparison: Because each Individual 2 lensis designed in real time, the optics of the lensdesign can also be precisely tailored to the exactfitting requirements of the wearer, ensuringthat every lens performs exactly as intended,with no unwanted prescription changes thatcould otherwise degrade vision quality throughthe central viewing zones.+25+20+15+10+50–5–10–15–20–25TARGET PERFORMANCEWITH “TRIAL FRAME” FITTING1.52.51.00.52.0EFFECTIVE RX:+3.00 SPH0.51.01.52.0+3.00 SPH RX: NEGLIGIBLE LENS TILT2.5+25+20+15+10+50–5–10–15–20–25INITIAL PERFORMANCEWITH SIGNIFICANT LENS TILT1.51.02.0EFFECTIVE RX:+3.51 –0.43 × 0440.50.51.01.52.02.5+25+20+15+10+50–5–10–15–20–25FINAL PERFORMANCEAFTER CUSTOMIZATION+3.00 SPH RX: 15° PANTO & 15° WRAP +3.00 SPH RX: 15° PANTO & 15° WRAP1.52.51.00.52.0EFFECTIVE RX:+3.00 SPH1.52.00.52.51.06

Personalized Lenses by ZEISSCustomized for the Wearer’s Frame Choice» The corridor lengthThe corridor length of a progressive lens—significantly influences or the vertical distance to the near zone—optical performancesignificantly influences optical performanceand wearer satisfactionand wearer satisfaction. If the corridor istoo long for a given frame size, reading utility is greatly reduced.If the corridor is too short, the optics of the lens design must beessentially “compressed.” Due to the mathematical constraintsof progressive lens surfaces, the rate of change in unwantedastigmatism across a progressive lens design must increase as thecorridor length decreases, resulting in narrower central viewingzones, reduced intermediate utility, and higher levels of unwantedperipheral astigmatism.Because the corridor length of a progressive lens design should beno shorter than necessary for the frame size, in order to minimizeunwanted astigmatism, ordinary progressive lenses have generallybeen designed to work well in conservative frame styles with asufficiently large “B” dimension or depth. Ordinary progressive lensdesigns often do not offer sufficient reading utility in smaller, morefashionable frame styles, since much of the near zone is cut away.Short-corridor progressive lenses designed to work in extremelysmall frame styles are also available. Short-corridor progressivelens designs, however, often provide significantly reduced visualcomfort and utility compared to standard lens designs.Unless the corridor length of the lens design coincides with theoptimal length required by the size of the frame, the wearer musttolerate unnecessary optical compromises with reduced visualutility. The corridor length of the ZEISS Progressive Individual 2lens design is precisely customized in real time in order to matchthe corridor length of the lens design to the fitting height requiredby the wearer’s chosen frame style. By matching the optics of theprogressive lens design to the wearer’s frame size, Individual 2 cantake full advantage of the available lens area, down to a minimumfitting height of 13 mm (Figure 16).Standard and short-corridor progressive lens designs offer optimalvisual performance for a relatively limited range of fitting heightsor frame sizes. Further, it is often difficult for eyecare professionalsto determine which of these lens designs will offer the bestperformance at “in-between” fitting heights. Unlike ordinaryprogressive lenses, the optics of the Individual 2 lens design areperfectly matched to virtually any frame style (Figure 17).OPTIMUM VISUAL UTILITY AS A FUNCTION OF FITTING HEIGHTZEISS PROGRESSIVEINDIVIDUAL 2STANDARDPROGRESSIVE LENSSHORT-CORRIDORPROGRESSIVE LENS1314 15 16 17 18 19 20 21 22 23FITTING HEIGHT OF LENS IN FRAME (MM)Figure 17. Unlike ordinary standard and short-corridor progressive lenses,Individual 2 offers wearers optimum visual utility at any fitting height.The corridor length of ZEISS Progressive Individual 2 variescontinuously starting at 9 mm. The optical characteristics of thelens will vary with fitting height (Table 1). The use of a variablecorridor length maximizes the utility of the central viewing zoneswithout unnecessarily increasing astigmatism in the periphery ofthe lens. Every Individual 2 lens will therefore deliver sufficientreading utility while providing the widest viewing zones possible.Table 1. The optical characteristics of Individual 2 vary as a function of fittingheight (data shown in millimeters for Plano Rx, +2.00 Add, balanced design).Fitting Height (mm) 14 15 16 17 18 19Near Checking Point 13 14 15 16 17 1885% Corridor Length 9 10 11 12 13 14Intermediate Height 4.5 5.0 5.5 6.0 6.5 7.0Intermediate Width 5.9 6.1 6.5 6.9 7.4 7.9Near Width at Fit. Ht. 11.4 11.5 12.0 12.4 12.8 13.2+1.75+1.75+1.75+1.75+1.7518 MM FITTING HEIGHT13 MM CORRIDOR17 MM FITTING HEIGHT12 MM CORRIDOR16 MM FITTING HEIGHT11 MM CORRIDOR15 MM FITTING HEIGHT10 MM CORRIDOR14 MM FITTING HEIGHT9 MM CORRIDORFigure 16. Using “real-time” optical design to manage the global geometry of the progressive lens design, the corridor length of Individual 2 varies continuously starting at 9mm—in 0.1-mm increments—in order to precisely match the optics of the progressive lens design to the size and fitting height of the wearer’s chosen frame.7

Personalized Lenses by ZEISSClinically Proven PerformanceMany of the customization strategies utilized in ZEISS ProgressiveIndividual 2 were also used in the original ZEISS Individual, whichwas the subject of a clinical study conducted by the Clinical ResearchCenter at the University of California, Berkeley. Researcherscompared the optical performance and wearer satisfaction of theZEISS Individual lens to a wide variety of ordinary, semi-finishedprogressive lenses. A total of 95 subjects completed a randomized,double-blind wearer trial that assessed objective measures of visualperformance as well as subjective measures of wearer preference.The results of this clinical study were recently published in the peerreviewedjournal of the American Academy of Optometry. 6Overall, there was a clear preference for ZEISS Individual afteraccounting for various interaction effects using multivariate analysis(p