LOCS III 白内障分级 权威

Clinical application of the Lens Opacities Classification System III in the performance of phacoemulsification
James A.Davison,MD,Leo T.Chylack Jr.,MD
Purpose:To report the correlation of features of cataracts graded by the Lens Opacities Classification System,version III (LOCS III),with phacoemulsification energy expenditure and the balanced salt solution (BSS ®)volume used during cataract surgery.
Setting:Wolfe Clinic,Marshalltown,Iowa,USA.
Methods:This was a retrospective review of 2364cases operated on by a single surgeon from January 1998to July 2000in which the cataract had been graded at the slitlamp using the 4grading scales of the LOCS III:nuclear opalescence (NO),nuclear color (NC),cortical cataract (C),and posterior subcapsular cataract (P).Polynomial best-fit lines were derived using regression analysis correlating the 4preoperative LOCS III characteristics with 3intraoperative observations:ma-chine-measured phacoemulsification time,mean power expenditure,and BSS volume.
Results:As determined by best-fit lines and their coefficient of determination (R 2),there were exponential relationships between machine-measured phaco-emulsification time and the degree of NC (R 2ϭ0.48)and NO (R 2ϭ0.40).Trends existed between NC and NO and the amount of BSS used (R 2ϭ0.08and R 2ϭ0.07,respectively).No relationships were observed between the LOCS III classes of cataract,C and P,at any intraoperative observation.
Conclusions:Exponentially,greater phacoemulsification energy was required as NC and NO increased.The LOCS III cataract grading system enhanced the ability to estimate ultrasonic energy expenditure and BSS volume use during phaco-emulsification.Preoperative LOCS III cataract classification can help to create a more formally organized,integrated,customized operative plan.J Cataract Refract Surg 2003;29:138–145©2003ASCRS and ESCRS
T
he Lens
Opacities
Classification System,version
III (LOCS
III),is
a widely
used,scientifically
valid,standardized
photographic comparison
system
for grad-ing
the features
of the
human age-related
cataract.1–5
It has
been used to grade the type and severity of cataract in
cross-sectional studies and the progression of cataract in longitudinal studies.It also has been used to grade cata-racts at the slitlamp.3
Grading using LOCS III involves the assessment of 4features shown on 3sets of photographs on an 8.5-inch ϫ11-inch color transparency (Figure 1).The features of nuclear opacification and brunescence are graded according to 1set of 6photographs.The bright-ness of scatter from the nuclear region has been desig-nated nuclear opalescence (NO)and the intensity of brunescence,nuclear color (NC).The amount of corti-cal cataract (C)is determined by comparing the esti-mated aggregate of cortical spoking to that seen in
Accepted for publication September 12,2002.From the Wolfe Clinic,Marshalltown,Iowa,USA.
Presented at the Symposium on Cataract,IOL and Refractive Surgery,San Diego,California,USA,April 2001
Reprint requests to James A.Davison,MD Wolfe Clinic,309East Church Street,Marshalltown,Iowa,USA.
©2003ASCRS and ESCRS
0886-3350/03/$–see front matter Published by Elsevier Science Inc.
doi:10.1016/S0886-3350(02)01839-4
5
separate photographs.Similarly,the estimated amount
of posterior subcapsular cataract(P)is determined by comparing it to another5photographs depicting in-creasing amounts of posterior subcapsular cataract.
The grade for each feature is derived by locating the image of the patient’s lens on the scale of severity for each feature represented in the color transparency.The NC and NO are graded on a decimal scale of0.1to6.9. The severity of C and P are graded on a decimal scale of 0.1to5.9.The final LOCS III grade comprises4deci-mal values,1each for NO,NC,C,and P.
In the original publication describing the LOCS III system,1an assessment of within-grader and between-grader reproducibility was done and expressed as a“95% confidence interval”for each scale.On average,these 95%confidence intervals were approximately0.7units. The intervals were used to define a significant change in the severity of the cataract.For example,if the NO grade was2.3at baseline and1year later it was3.5,the increase in severity(3.5–2.3ϭ1.2)was greater than the95% confidence interval(0.7)and it was therefore reasonable to conclude that one was95%confident that the change was statistically significant.If the increase had been only 0.5units,the increase could more likely be the result of the intrinsic methodologic noise of the LOCS III system and not a true increase in the severity of the cataract.
Since1998,LOCS III has been used systematically in the clinical practice of one author(J.A.D.).Preoper-ative LOCS III grading of all surgical patients was done at the slitlamp to improve clinical documentation in the clinical record.Parenthetical descriptions were rarely added but usually included the critical nature of the centrality within the visual axis of subtle localized inter-faced zones of NO and NC,cortical spokes,or subcap-sular opacities.There was consistency in grading over time,and patients could be told with greater confidence whether their cataracts were stable or progressing.It was also helpful to have accurate measures of cataract severity when discussing cases with third-party payer representa-tives;surgical interventional decisions to offer surgery to some patients could be better defended.
Over time,LOCS III slitlamp grading was empiri-cally incorporated into the decision-making process and planning of upcoming surgeries.Ultimately,this re-sulted in a more organized,integrated,customized op-erative plan for each patient.
Patients and Methods
In this retrospective study,2364consecutive cases of phacoemulsification were analyzed with respect to the 4LOCS III characteristics and machine-measured phaco-emulsification time,average machine measured power(%), and the balanced salt solution(BSS௡)volume used.All data points had been recorded in2186cases.Surgery was per-formed from January1998to July2000by a single surgeon (J.A.D),who also performed LOCS III grading of all cataracts at the slitlamp.
A standardized nuclear-fracture quadrant-aspiration phacoemulsification technique was used with a straight 45-degree0.9mm ABS MicroTip with the Alcon Legacy 20,000machine.6After topical anesthesia was administered,a temporal clear corneal incision was made.Grooving was ac-complished with the machine in memory I(phacoemulsifica-
Figure1.(Davison)The LOCS III standard images in an8.5-inchϫ11-inch color transparency as used in the office at the slitlamp.The top row contains the standards for NO and NC.The second row contains the standards for grading C and the bottom row,for grading P.
J CATARACT REFRACT SURG—VOL29,JANUARY2003139
tion power maximum,90%;vacuum maximum,50mm Hg;aspiration flow rate,14cc/minute)(Figure 2).Wider,deeper grooves were made as nuclear hardness increased.The pos-terior nuclear plate was torn from the periphery toward the center by cross action with the phacoemulsification tip and a custom,modified,0.37mm cyclodialysis spatula (Figure 3).Quadrant aspiration was accomplished in memory III (phaco-emulsification power maximum,70%;vacuum maximum,500ϩmm Hg;aspiration flow rate,35cc/minute).
The aspiration process was kept posterior to the iris plane within the capsular bag as much as possible to protect the
corneal endothelium from damage from fragment impact and abrasion (Figures 4to 6).Sodium hyaluronate 3.0%–chon-droitin sulfate 4.0%(Viscoat ௡)was usually injected into the anterior chamber before quadrant aspiration when the NC was greater than 4.5.In some cases,Viscoat was reinjected before aspiration of the fourth quadrant because of the ten-dency of the capsular bag to flatten after the third quadrant had been removed,which forces the remaining process ante-rior to the iris plane.In some eyes,soft quadrants or the last fragment of the fourth firm quadrant were removed using reduced vacuum (maximum 300mm Hg),maximum
power
Figure 2.(Davison)After initial grooving is completed,a second
rotation of the nucleus allows for improved visualization while deeper grooving progresses in hard
nuclei.
Figure 3.(Davison)Nuclear cracking is created from the periphery
toward the center with a cross action of the phacoemulsi fication tip and the cyclodialysis
spatula.
Figure 4.(Davison)The 45-degree phacoemulsi fication tip is
turned sideways with its aperture facing the interior wall of the first nuclear quadrant.Low levels of emulsi fication energy are used to engage and impale the central portion of the
quadrant.
Figure 5.(Davison)A low level of ultrasonic energy and a higher
level of vacuum allow the tip to adhere to the softer edge of the quadrant and drag it centrally.
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140
(50%),and a reduced aspiration flow rate (25cc/minute)(Figures 7and 8).
Polynomial best-fit lines were derived by regression anal-ysis among the 4LOCS III characteristics and the 3phaco-emulsification observations.
Results
The mean machine-measured phacoemulsification time increased as the NO and NC grades increased (Table 1).As determined by the best-fit lines and their coefficients of determination (R 2),there was an expo-nential relationship between NO and machine-mea-sured phacoemulsification time (R 2ϭ0.40).A trend existed between NO and the mean power (R 2ϭ0.15)and the amount of BSS used (R 2ϭ0.07)(Figure 9).
A slightly stronger exponential relationship existed between NC and machine-measured phacoemulsifica-tion time (R 2ϭ0.48).A trend also existed between NC and mean power (R 2ϭ0.18)and the amount of BSS used (R 2ϭ0.08)(Figure 10).
No relationships were observed between the LOCS III classes of cataract,C and P,and any intraoperative observation (Figures 11and 12).
Discussion
In the original LOCS III publication,the NO and NC scales were highly correlated with each other and the relationships between objective measures of NO,NC,and the LOCS III grade of the standard images
were
Figure 6.(Davison)The bulk of the quadrant is central while mod-erate ultrasonic energy,vacuum,and aspiration flow are used to remove the firm portions of the
quadrant.
Figure 7.(Davison)Aspiration can begin after an edge of the last
quadrant is lifted free of the posterior
capsule.
Figure 8.(Davison)The cyclodialysis spatula protects the poste-rior capsule as phacoemulsi fication power is applied during removal of the last quadrant.Lower levels of vacuum and aspiration flow rate help protect the posterior capsule from inadvertent aspiration.
Table 1.Mean machine-measured ultrasound time
(minutes).
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Figure9.(Davison)A significant relationship is seen between
LOCS III NO and ultrasound time but not mean ultrasound power and
BSS volume used.
Figure10.(Davison)A significant relationship is seen between
LOCS III NC and ultrasound time but not mean ultrasound power and
BSS volume used.
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Figure11.(Davison)No relationship is seen between LOCS III C
and ultrasound time,mean ultrasound power,and BSS volume used.
Figure12.(Davison)No relationship is seen between LOCS III P
and ultrasound time,mean ultrasound power,and BSS volume used. J CATARACT REFRACT SURG—VOL29,JANUARY2003143
nearly linear.The NO was assessed independently with image analysis of optical density,and NC was assessed independently with fast spectral scanning colorimetry of each LOCS III standardized image.Highly different grades of NO and NC in the same cataract were un-likely.Similarly,the relationship between the expendi-ture of phacoemulsification energy and the LOCS III grades of NO and NC appears to be linear for LOCS III grades below approximately3.7.Above that,the rela-tionship between LOCS III grade and phacoemulsifica-tion energy expenditure seems to become exponential. Although in LOCS III NO and NC are graded sepa-rately,most clinicians are accustomed to describing nu-clear change by a single term,nuclear sclerosis.Both color change and increased light scattering are part of the pro-cess of nuclear sclerosis,and it is therefore not surprising to have found that both NO and NC are similarly pos-itively correlated with ultrasonic energy exposure.
When viewing a cataractous lens with LOCS III NO and NC grades of4.0to5.0,most surgeons intu-itively anticipate increased phacoemulsification times. The nucleus is simply harder,so it will take more energy to emulsify.The LOCS III NC grade has been corre-lated with hardness of the central nucleus as measured by the resistance to a fine conical probe measured by a dynamometer.7Phacoemulsification energy recorded by cumulative delivered energy as well as by postopera-tive anterior chamber flare has been shown to be corre-lated with LOCS III NC and NO.8
The surgeon in this study finds it useful to be able to accurately grade opalescence and brunescence(and the severity of C and P)to better estimate when prolonged ultrasonic time or increased ultrasonic energy is likely.It has proved advantageous to integrate LOCS III grading into routine operative planning.By doing so,the sur-geon will be better prepared to manage the more scle-rotic nucleus and his or her preoperative planning can be more patient specific.
The surgeon in this study empirically formulated several recommendations for customizing a surgical plan using preoperative LOCS III grading as a part of a com-plete preoperative ophthalmic examination.These are listed below.
1.A retentive viscoelastic material is recommended in cases in which the LOCS III NO or NC grade is4.0 or greater.
2.If the LOCS III NO or NC grade is5.0,the capsulorhexis will be more easily visualized if indocya-nine green dye is used to stain the anterior capsule.
3.If the pupil is smaller than
4.5mm and the LOCS III NO or NC grade is greater than4.5,use of a pupil expansion/maintenance device should be considered.
4.If zonular integrity is compromised and the LOCS III NO or NC grade is4.5or greater,a backup ciliary-sulcus-supported intraocular lens(IOL)or ante-rior chamber IOL should be available.
5.Surgeons in training should learn and use LOCS III grading to enable them to select“normal”cases with nuclei of enough substance to easily manipulate yet readily emulsify.Very soft or very hard nuclei may present unnecessary challenges.
6.The LOCS III is helpful and should be used in the trials of new technologies for cataract removal.For ex-ample,in one author’s experience(J.A.D.)with early AquaLase technology(Alcon Surgical),efficient removal of a nucleus with an NC grade greater than3.7was not possible.
Of course,the relationships between LOCS III characteristics and phacoemulsification energy expendi-ture vary with the individual technique and equipment used.Despite this individual-specific variation,it is likely that the trends observed will be seen with other surgeons as long as a mechanical removal technique is used.Incorporating LOCS III grading into a preopera-tive regimen should not only improve surgical planning, it should also improve clinical documentation,commu-nication among providers and with third-party payers, and the accuracy of longitudinal follow-up.Most im-portant,preoperative LOCS III classification should contribute to more predictable and effective cataract surgery.
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