Christopher J. McDevitt, M.D.
School of Ophthalmic Medical Technology, CE Course
May 19 and 20 Airport Hilton, Bloomington, MN
Corneal cross-linking (CXL), SMILE refractive procedure, Corneal inlays for presbyopia correction
Small incision lenticule extraction (SMILE) for high myopia (-6to-10 D
3 year follow up demonstrates good stability
Uses femtosecond laser and no flap
Potential for reduced laser energy, smaller superficial incision, less neurotrophic and dry eye
Results are comparable to LASIK
Compared eyes with LASIK and SMILE at 3 months showed statistically significant better in LASIK eyes. At 6 months SMILE outcomes like LASIK at 3 months.
Surgical correction of presbyopia options: LASIK monovision, clear lens extraction with multifocal IOL
Corneal inlay placed in corneal stroma in the nondominant eye under femtosecond laser keratome flap or in a pocket
KAMRA inlay relies on extended depth of focus created by a pinhole, 1.6mm in diameter in an annular disc with a diameter of 3.8mm.
Flexivue Microlens inlay: donut shaped high index of refraction lens distance vision central near vision outside.
Raindrop Near Vision inlay : 2mm meniscus with same refractive index as the cornea and ahs no refractive power in the cornea. Action is to biomechanically raise the stroma and epithelium over the inlay inlay is made of clear permeable hydrogel
373 patients in study, multicenter
Uncorrected near vision in treated improved 5.1 lines,
Uncorrected intermediate vision improved 2.5 lines
Stabilize cornea in patients with progressive corneal thinning disorders
FDA approval of Avedro KXL
FDA approval of 2 photoenhancers: Photrexa and Photrexa Viscous
Goal: halt progression of keratoconus at a point when vision is still relatively good
Other options are improved contact lens technology.
Photochemical reaction of corneal collagen resulting from combining photosensitizer riboflavin with ultraviolet light (UVA)
Avedro KXL approved for progressive Keratoconus(KCN) and post refractive surgery ectasia
Standard protocol for treatment Dresden protocol) : initial removal of the corneal epithelium + 0.1% riboflavin every 1 to 3 minutes for 30 minutes (imbibition)
Cornea then is irradiated for 30 minutes with 370nm UVA at a power of 3 milli- watts/cm2
Failure rate for KCN is less than 2%.
Mild KCN: contact lenses, soft toric, RGP contact lenses hybrid contact lenses, hard in the center , sort on he periphery of the lens.
Piggy bag lenses: soft lens on corneal surface and hard lens placed on top
Scleral lenses
Intracorneal ring segment (ICRS) to reshape cornea for patients that cornea has gotten worse and pt. cannot wear CL’s
ICRS reshape to allow CL fit
Corneal transplant: top layer : deep anterior lamellar keratoplasty (DALK)
DALK decreases graft rejection risk
Corneal transplant: full thickness, penetrating keratoplasty (PK)
Keratoconus:
Concern to intervene in young patients getting worse but that do not have severe KCN yet.
Criteria for progression are not well established
Older patient with stable KCN may not need CXL.
Good candidates are ages 15 to 35 with minimal corneal thickness of 440 to 450 micrometers
Post refractive surgery:
Mostly post LASIK and age is not a factor and results are good to stabilize ectatic corneas.
Contraindication: less than 400 micron cornea, severe corneal scarring, or opacification, history of herpes infection of poor epithelial wound healing
Depth of focus IOL, Trifocal IOL, Wrong IOL implanted
Outcomes study of more than 21,000 cases in US, since 2011 compared with procedures done in ASC/hospital in Kaiser Permanente Colorado Health Care system
Outcomes consistently excellent with safety profile of procedure performed in ASC’s (80 percent) and hospitals
Main cost of cataract surgery is facility fee: Medicare reimbursement average $964 for ASC and $1670 for hospitals (2013 data)
Two ACLS certified RN, one circulating one monitoring/charting and surgical technician. No anesthesiology.
No IV or injections given
Topical +/- intracameral anesthesia with oral triazolam
Adverse events : Intraoperative PC rupture 0.55% (119/21,501)
Vitreous loss: 0.34% (73/21,501)
Adverse events: Postop: endophthalmitis 0%; surgical reintervention within 3 months: 0.61% (131), 6 months 0.70% (150)
Surgical intervention: IOL exchange (44), repositioning( 17), insertion after lens removal (22), lens fragment removal (22), vitrectomy (16)
Office based cataract surgery pre-op testing not routinely done
Clinicians face challenges in acquiring optical data to optimize IOL selection
Error in IOL calculation 79%:
Effective lens position
Axial length
Postoperative refraction
Total corneal contribution to IOL calculation error contribute to errors of greater than 0.25 diopter in 25% of eyes
Increasing accuracy in axial length measurements by IOL master 700 and Lenstar are small with an dioptric errors of less than 0.05 Diopter.
Effective lens position (ELP) and refraction are the most persistent source of error
Better estimate of with inclusion of anterior chamber depth (ACD), lens thickness and corneal diameter.
Refraction multiple sources of variability: Patient responses
Refractionist abilities
Tear film status
Chart distance
Ocular higher order aberrations especially spherical aberration and coma
Warren Hill data base of 260,000 operated eyes
Percentage of eyes within 0.5 D of target refraction was
Equal to or less than 78% for over 50% of surgeons
79 to 84% for up to 6% of surgeons
89 to 90% for fewer than 1% of surgeons.
Results with Dr. Hill’s new RBF formula 91% of eyes within 0.5D
Eyes with AL: 20.97 to 29.10 mm
Therefore 1 in 11 normal eyes will be off by more than 0.5D
Worse outcomes with:
Short eyes
Eyes measuring cornea is problematic
Ablated
Ectatic
Postkeratoplasy
Better outcomes with Toric IOL’s with now <0.5 D for refractive astigmatism in 80% of eyes
Spherical power of the cornea
Astigmatism
Higher order aberrations
Determination of corneal spherical power
Perfect outcome: accurate measurements, good IOL power formulas, and updated formula IOL constants
Good fortune
Variable corneal easements
Anterior corneal measurement methodologies:
Reflection: manual K, Placido rings, point source LED, SimK values displayed
Scan slit imaging: Orbscan
Shheimpflug imaging: measure thickness of optical sections
OCT:
rastersteriography
Compare :
Atlas,
Galilei dual Scheimpflug,
IOL Master 500
Manual Keratometry
Intradevice deviations low
Interdevice: 95% agreement
IOL calculations based on measuring the anterior corneal curvature and assume a constant ratio between anterior and posterior corneal curvatures
Posterior/anterior ratio deviated from standard value
Standard value 1.3375
Indices lead to corneal powers greater than true power
IOL calculation formulas compensate for this error and others such as ELP, IOL optical features and use lens constant as a fudge factor
Posterior corneal power is ten times lower than anterior corneal power based on the refractive index of the adjacent media (air compared with aqueous humor)
Clinically challenging to measure the posterior cornea curvature
Posterior corneal measurements:
Scheimpflug
OCT
Reflection by color LED device
Ratio of posterior to anterior corneal curvatures:
Gullstrand: 0.883 now found to be too high closer to 0.81 for normal corneas (0.80 to 0.86).
Translates into error of 0.5 D
Myopic LASIK/PRK: lower than 0.81
Hyperopic LASIK: slightly higher than 0.81
Change anterior corneal curvature
Posterior corneal curvature unchanged
Greater range of variability in the anterior corneal power in the central 4mm after these procedures .
After RK, posterior corneal curvature is also changed in an unpredictable way
In addition introduces a second problem with ElP estimation. Solutions found in: Holliday with double K approach
ASCRS Post-Refractive Surgery calculator
Barret True-K
Method relying on prior clinical data:
Errors in pre op K’s errors
Postop refraction errors
Less than 60% accurate within 0.5 D
These methods have been removed from ASCRS calculator
Methods using combination of surgically induced refractive e change and present corneal power
Measure the surgically induced refractive change by some fraction and use this value to modify corneal power or IOL power after calculated
Some of the most accurate
Measurements based only on present data on the patient.
Regression formulas derived from analyses of pooled data
Using actual individual patient corneal power by Scheimpflug or OCT measurements
Comparing the regression formula and the OCT based formula within 0.5D was less than 70% with formulas and 68% with the OCT based formula
Intraoperative retinoscopy
Intraoperative autorefraction
Intraoperative aberrometry after cataract removed then aphakic refraction proprietary formulas used plus biometric data to calculate IOL power
Regression of data used
Outcomes: +/-0.5 D 69% to 74%
Abnormal cornea with:
the standard ratio of anterior and posterior curvature is altered
Cornea irregularity make it difficult to determine which value for the anterior corneal power to use for the calculation
Cornea are unstable
Some will undergo keratoplasty later
Few peer reviewed studies that offer helpful guidelines
Truong et al 22 eyes with mean errors of greater than 1Diopter using 3 different devices: IOL master, Placido topography and Pentacam
Errors: overestimate anterior corneal power, and underestimate the steepness of the posterior cornea (negative power).
PKP: cornea , like KCN, have high amounts of anterior corneal astigmatism, with large irregular component
PKP: uncertain posterior corneal power.
Post cataract surgery with toric IOL with residual astig of 2.61 diopters
Post cataract surgery with femto laser incisions with residual astigmatism within 1 D of intended in 76% of patients
DSEK produces modest corneal power changes with minimal astigmatism shift
DSEK produces hyperopic shift 0.7 to 1.5 D
Donor lenticule is concave and increases the minus power of the posterior cornea
Cataract s surgery and DSEK target of -0.75 to -1.5 D myopia reasonable to compensate for this hyperopic shift
Toric implant a possibility since DSEK adds little astigmatism.
DMEK adds less with hyperopic shift 0.24-0.50 and minimal astigmatism induced
DMEK effects of reversal of myopic shift from corneal edema
Residual astigmatism found
Overcorrection with the rule astigmatism WTR
Undercorrection against the rule astigmatism ATR
Posterior cornea is steep vertically in most eyes
Produces positive refractive astigmatism ATR
Reduces refractive astigmatism produced by anterior WTR
Adds to astigmatism produces by anterior WTR astigmatism
Antero WTR: as astigmatism increases the posterior corneal vertical steepness increases which decreases the total corneal astigmatism
ATR: posterior cornea does not change with increasing anterior ATR astigmatism
Baylor nomogram compensates for posterior corneal astigmatism changes as the orientation and magnitude of the anterior corneal astigmatism changes
Abulaafia-Koch formula
Barrett toric calculator
Measurement of the posterior cornea are not accurate
Presently adjustment are made based on anterior cornea curvature alone
Efficacy and safety meta analysis of 14,567 eyes compared manual cataract surgery (MCS) vs FLACS.
2802 screened articles ,15 randomized controlled trials and 22 observational cohort studies.
Primary visual and refractive outcomes no statistically significant difference detected between FLACS and MCS uncorrected visual acuity, corrected distance acuity
Secondary endpoints: effective phacoemulsification time, capsulotomy circularity post-op corneal central thickness, corneal endothelial reduction Flacs over MCS.
Distance vision quality like a monofocal IOL with near vision
AMO Symfony and Symfony toric
Incorporate a difractive echelette design with achromatic technology
Elongate focus
Correct chromatic aberrations with improved contrast sensitivities post op auto refractors may estimate more myopic result so need to refine with manifest refraction.
Better continuous intermediate vision
Good vision from distance to arms length
Readers +1.25 for near vision
IOL calcs Lenstar with Olsen ray tracing technique better than IOL master
NHS in UK wrong IOL implants even with surgical check lists; 178 (2010 to 2014)
Human factors to blame.
In US VA study confirms similar problem in US
One cause is incorrect transcription of the selected IOL to other sources and subsequent failure to refer to original source documents
Errors occur at every stage: biometry, transcription; intraoperative (change in planned procedure); perioperative (handwriting misinterpretations and wrong IOL in OR)
Misfile biometric date in wrong patient file
Mistakes in EMR
44 of unknown cause
IOL exchange 45 cases
Recommend simulation training practicing the actions, behaviors, communication skills teams
Visual tasks in the efferent system affected: convergence accommodation saccadic mechanism Vestibulo-ocular function Smooth pursuit
Common Symptoms:
Photophobia
Headache
Slowed speech
Dizzy feeling: examine the oculomotor system carefully.
Trouble with reading or using screens can be a sign of convergence problems
Motion sensitivity may be a sign of vestibular system malfunctioning
Sports Concussion Assessment Tool (SCAT 3):
Includes checklist for symptoms: memory, balance, cognitive changes
Does not use vision testing.
King-Devick Testing
Assess saccades and vergence
Tests the time to read numbers with variable spacing on 3 test cards
Assesses a variety of integrated visual systems at once: brainstem, cerebellum, and cerebral cortex.
Can capture concussions that other sideline tests may miss since athletes underreport symptoms
Can be administered by parents or coaches in one minute and requires no special equipment.
LTP by Optometrists, Nerve fiber OCT in Myopia, Cypass shunt, Intracameral implant for drug delivery
Stein et al found a clinically significant difference in the frequency of additional LTPs between optometrists and ophthalmologist in Oklahoma
Additional LTP has a decreased rate of success and an increased complication profile.
Medicare claims based study
36% of eyes treated by optometrists required more than one treatment. 15% of eyes treated by ophthalmologists required more than one treatment.
Discussion emphasizes the need for appropriate training to identify with gonioscopy the critical features of the anterior chamber angle and the application of laser trabeculoplasty.
New minimally invasive glaucoma surgery device (MIGS)
This is an new device following the iStent, approved 4 years ago.
CyPass patients achieved a reduction in IOP that was greater than those having cataract surgery
Decreased lasted for the full 2 years of the study
Microstenting reduced the long-term use of glaucoma medication to one third of those in the control group.
85% of the microstent patients were medication free compared with 59% of controls.
Bimatoprost SR as effective at 6 months as eye drops (2 year trial).
Drug is like Ozurdex implant with bimatoprost instead of dexamethasone
Drug slowly released through the Novadur biodegradable polymer platform
Decreased IOP within one day and all subsequent visits
Implant lasts 4 to 6 months
High patient satisfaction.
Contact lens sensor (CLS): Sensimed Triggerfish monitors IOP fluctuations for 24 hours
Triggerfish: records changes in the ocular dimensions ( IOP volume changes occurring at the corneoscleral junction term called measuring limbal strain
No direct conversion of this measurement to IOP
CLS parameters: number of large peaks, mean peak ration, wake sleep slope, etc.
Data is sent to a recording device that the patient wears then transferred to clinicians computer.
$650 for 1 Triggerfish CLS monitoring
Eyemate: IOP microsensor that is implanted into the ciliary sulcus during cataract or glaucoma surgery
Patient uses a hanheld reader that receives data from the device and displays the IOP value performing self-tonometry at home.
Further work being done.
New devices available in the future to provide continuous monitor rather than brief tonometer reading in clinic.
Abnormalities detected in RNFL in high myopia have high degrees of false-positive errors.
Normative databases of many OCT instruments do not include individuals with high myopia
Normal data base for Cirrus HD OCT had a mean refractive error of -0.82
Convergence of superior temporal and or inferior temporal RNFL bundles toward the macula in eyes with high myopia may render those values abnormal with reference to this normative data base.
Circumpapillary scan RNFL increases in diameter with distance from the OCT unit and the RNFL decreases a small amount
Retina becomes thin in high myopia since it is “stretched” to cover the area of the enlarged globe
Measurement circle is further from the center of the optic nerve so the measured RNFL is thinner than it would be for a 3.4 mm circle centered on the optic nerve head
The greater the axial myopia the greater the artefactual and actual RNFL thickness
Red disease pseudo condition with RNFL thickness outside normal limits and mistakenly interpreted as glaucoma myopia induced OCT artifacts deviations from normal data base , red, are diffuse and not limited to the superior and inferior area of the optic disc
Verifying abnormal OCT shows normal VF with mod to severe OCT abnormality such as less than 75% of normal
Solution is add normative data base for high myopia
Goal of home monitoring to catch the earliest signs of neovascularization as early treatment. Good vision at start of injections leads to best vision two years later.
Foresee Home (Notal Vision) was efficacious in a NEI sponsored clinical trial
Uses a preferential hyperacuity perimetry device (PHP) plus proprietary metamorphoropsia- detection algorithm
Specific tele monitoring protocols followed at a central reading center.
Notal Vision provides the equipment to the patient after receiving a prescription form the ophthalmologist
If changes from baseline test are found then a manual comparison is done by a specially trained O.D> or ophthalmologist
The location and the size of the metamorphopsia and scotomas are derived from the patient's responses to a series of dotted lines that the perimetry device flashes in the visual field at various locations.
Some of the lines are straight other intentionally abnormal and patient needs to confirm by clicking a mouse.
Errant or missing clicks may be a sign of early choroidal NV
Patients receive automatic reminders
For more than a decade the PHP system has undergone increasingly rigorous testing
Costs Medicare copay for the service is $15 per month with no patient costs and setup
Device is shipped to patient home
No cost to prescribing clinician.
Age- Related Eye Disease Study 2- Home Monitoring of the Eye study.
Foresee Home Device arm vs standard home monitoring
Device detected more early AMD and the vision was better at the time of detection
Study was stopped since the device worked so well compared to standard
Take home points: home monitoring may be useful: if patients detect a change then need to be seen in office for evaluation.
Smartphone and tablet-based mVT app (Vital Art and Science) looks for sign of progression
AMD, wet, dry, and diabetic macular edema
Testing has shown it equivalent to Amsler grid and ForeseeHome
Images of 4 circles, one of which has an irregular edge on a smartphone or tablet screen.
The degree of distortion decreases with each subsequent image
The patient uses the touch screen to choose the distorted shape and the results are tracked remotely and compared with the patients baseline performance
Small validation studies so far
Cost not decided yet and insurance coverage has not been approved
Expected approval in 1-2 years
ForeseeHome
Initial VA of 20/60 or better
Looks for metamorphopsia both centrally and outward to cover 14 degrees of the central visual field (VF)
Ease of use: 20 % in AREDS2-Home could not use device
Preexisting VF defects interfered with the PHP test
Patient could not adapt or fixate on the center light
mVT
Initial VA 20/100 or better
Macular testing and covers 3-degree center of central visual field
Feasibility trial no patients failed because of inability to perform the test.
Fixation not necessary to use the mVT app
High contrast images presented to the amblyopic eye, low contrast images to the fellow eye
Adapted to an iPAD device
Falling blocks game using red-green anaglyphic glasses
Compare one hour a day with 2 hours a day of patching
Aged 5 to 13 years with 20/40 to 20/200 amblyopoic vision.
16 weeks
AMD
Glaucoma
Dry AMD: no clear role, may consider genetic testing but does not change recommendations AREDS 2 supplements and good diet.
Smoking cessation
Not covered by Medicare and most insurance carriers
Testing is warranted if it will impact treatment or surveillance: Congenital glaucoma or juvenile-onset open angle glaucoma(JOAG)
Genetic testing allows ophthalmologist to identify patients with genetic variants that cause congenital glaucoma and JOAG
Follow them closely
Reassure family members who do not carry variants that their risk of glaucoma is no higher than the general population
Direct-to-consumer testing (DCT): variation in the cost ,scope, clarity of information content for DCT for ophthalmic conditions
DCT company 23- and- Me can report allele information for a few heritable conditions but can no longer provide interpretation need to consult genetic counselor
AAO recommends avoiding DCT services.
Genes that increase risk: many open angle glaucoma (POAG) cases the combined action of a number of genetic factors contribute to disease development
Each one increases a small increase but by themselves do not cause disease
Genes that directly cause the disease: three genes have been identified and a mutation in these genes is highly predictive of disease.
These occur in less than 5% of POAG.
Since the prevalence rate is so low it is not feasible to test for these genes in the broad unselected population.
Genetic mutation in genes myocilin (MYOC), optineurin (OPTN) and TBK1 can be a primary cause of glaucoma
Some patients with variant of MYOC respond differently to medical treatment for glaucoma
MYOC mutations are associated with 3% to 4% of POAG
OPTN or TBK1 are associated with 1 to 3 % of low tension glaucoma
Testing for early onset glaucoma(JOAG) associated with mutations with 6 genes (MYOC, PITX2, FOXC1, PAX6, CYP1B1, LTBP2). All together account for only 20% of JOAG)
If considering refer to a genetic counselor for interpretation ordering these tests many time
“Likelihood to recommend”
Press Ganey designs patient satisfaction surveys for health care providers
PG surveys used by 50% of US hospitals and 10,000 health care organizations
Patient’s perception of the time spent with the practitioner and the ease of appointment scheduling are 2 variables that best correlate with patients recommending practitioner to other patients
Friendliness/courtesy of the care provider correlated least with the likelihood to recommend