Eyeworld

EW REFRACTIVE 58 July 2018 using a completely different princi- ple because it has colored LEDs that are reflected off the anterior corneal surface, and it has seven white LEDs whose reflection off the posterior corneal surface can be detected to measure posterior corneal astigma- tism. As they continue to improve their software, I'm finding it to be an increasingly valuable way of mea- suring total corneal astigmatism," he said. Abnormal corneal topography If the corneal topography is ab- normal, Dr. Koch said to look for the cause. "If it appears to be an ocular surface issue, I will look for ocular pathology, such as epithe- lial basement membrane disease or Salzmann's nodular dystrophy. I may do a dry eye evaluation and treat the dry eye. If it's epithelial basement membrane disease or Salzmann's nodular dystrophy, and I think it will affect either the accuracy of the calculations or the quality of the vision postoperatively, I will treat that first by scraping it and letting the patient's eye heal for about 3 months. Then I will repeat the calculations," he said. "At that point topography again is import- ant because subtle irregularities can persist and need to be detected to assist in patient counseling and IOL selection." EW Editors' note: Dr. Dell has financial interests with Johnson & Johnson Vision (Santa Ana, California), Bausch + Lomb (Bridgewater, New Jersey), Presbyopia Therapies (Coronado, California), Ocular Therapeutix (Bed- ford, Massachusetts), Optical Express (Glasgow, U.K.), Tracey Technologies (Houston), Advanced Tear Diagnostics (Birmingham, Alabama), and Lume- nis (Yokneam, Israel). Dr. Koch has financial interests with Alcon (Fort Worth, Texas), Carl Zeiss Meditec, and Johnson & Johnson Vision. Contact information Dell: steven@dellmd.com Koch: dkoch@bcm.edu whether the patient has ocular surface disease irregularity-related topographical abnormalities. Then we're screening for pathology, like keratoconus, forme fruste keratoco- nus, pellucid marginal degeneration, or other things, that might influence our decision on whether the patient is a candidate for cataract surgery in the first place and if so, what type of implant he or she might eventually receive," he said. If a patient is found to have ocular surface disease, topography is used to follow the patient's progress. "That's one of the key factors in our determining whether a patient has reached an endpoint of sufficient improvement in their ocular surface disease to proceed with refractive cataract surgery," Dr. Dell said. He uses topography in conjunction with devices like the LENSTAR (Haag-Streit, Koniz, Switzerland) and the IOLMaster (Carl Zeiss Meditec, Jena, Germany) to verify and con- firm that he has achieved good read- ings on the patient's overall corneal power and corneal astigmatism. Dr. Dell screens for posterior corneal astigmatism using devices like the Pentacam (Oculus, Wet- zlar, Germany) in patients who are having laser refractive surgery or corneal refractive surgery. "We don't routinely image the posterior corneal curvature in our cataract patients because we haven't found it to be consistently helpful, so we use nomogram-based adjustments of our toric power calculations that have been described well, either in some of the modern IOL astigmatic toric calculators or nomogram ad- justments like that proposed by Dr. Koch and Li Wang, MD," he said. Lens calculations Dr. Koch is using corneal topog- raphy, in combination with other tools, to determine lens calculations. "We look at the anterior corneal astigmatism, and we look at the total corneal astigmatism with the Galilei [Ziemer, Port, Switzerland]. I am also using the Cassini [The Hague, the Netherlands] for my toric IOL calculations. The Cassini works Diagnostics continued from page 57 The seven LEDs of the Cassini with the bright reflections off the anterior corneal surface and the faint but measurable images reflecting off the posterior corneal surface Source: Douglas Koch, MD, and César Vilar, MD Patient name Tan, Ken K Tan, Ken K Patient id 0302925345 0302925345 Date of Birth May 5, 1947 May 5, 1947 OD Clinic Capture date June 5, 2018 10:10 am June 5, 2018 10:10 am Physician - - MAPS MAPS T N Anterior Axial / Sagittal Anterior Axial / Sagittal 0 30 60 90 120 150 180 210 240 270 300 330 As Ts Ps -4 -2 0 2 4 38.5 39.0 39.5 40.0 40.5 41.0 41.5 42.0 42.5 43.0 43.5 44.0 44.5 45.0 45.5 46.0 46.5 47.0 47.5 48.0 48.5 49.0 49.5 -4 -2 0 2 4 Standard Scale Standard 0.50D Anterior Tangential Anterior Tangential 0 30 60 90 120 150 180 210 240 270 300 330 As Ts Ps -4 -2 0 2 4 38.5 39.0 39.5 40.0 40.5 41.0 41.5 42.0 42.5 43.0 43.5 44.0 44.5 45.0 45.5 46.0 46.5 47.0 47.5 48.0 48.5 49.0 49.5 -4 -2 0 2 4 Standard Scale Standard 0.50D Anterior Elevation Anterior Elevation 0 30 60 90 120 150 180 210 240 270 300 330 As Ts Ps -4 -2 0 2 4  55  50  45  40  35  30  25  20  15  10   5   0  ‒5 ‒10 ‒15 ‒20 ‒25 ‒30 ‒35 ‒40 ‒45 ‒50 ‒55 -4 -2 0 2 4 Standard Scale Standard 5μm Anterior Corneal Aberrations Anterior Corneal Aberrations 3 3 (2,-2) (2,-2) Oblique Astigmatism Oblique Astigmatism -0.402 -0.402 4 4 (2, 0) (2, 0) Defocus Defocus 1.558 1.558 5 5 (2, 2) (2, 2) W/A Astig. W/A Astig. 1.193 1.193 6 6 (3,-3) (3,-3) Oblique Trefoil Oblique Trefoil -0.238 -0.238 7 7 (3,-1) (3,-1) Vertical coma Vertical coma 0.292 0.292 8 8 (3, 1) (3, 1) Horizontal coma Horizontal coma -0.215 -0.215 9 9 (3, 3) (3, 3) Horizontal Trefoil Horizontal Trefoil -0.085 -0.085 10 10 (4,-4) (4,-4) Oblique Tetrafoil Oblique Tetrafoil -0.020 -0.020 11 11 (4,-2) (4,-2) Obl. 2 Obl. 2 nd nd Ast. Ast. -0.062 -0.062 12 12 (4, 0) (4, 0) Spherical Aberration Spherical Aberration 0.371 0.371 13 13 (4, 2) (4, 2) W/A 2 W/A 2 nd nd Astig. Astig. 0.021 0.021 14 14 (4, 4) (4, 4) Horizontal Tetrafoil Horizontal Tetrafoil 0.025 0.025 K-READINGS K-READINGS (n=1.3375) (n=1.3375) Keratometric SimK Average K Average K 44.93 D (7.51 mm)  44.93 D (7.51 mm)  Steep K Steep K 45.53 D (7.41 mm) @ 174° 45.53 D (7.41 mm) @ 174° Flat K Flat K 44.34 D (7.61 mm) @  84° 44.34 D (7.61 mm) @  84° Astigm. Astigm. 1.19 D 1.19 D Total Cornea Average K Average K 43.79 D  43.79 D  Steep K Steep K 44.56 D @ 178° 44.56 D @ 178° Flat K Flat K 43.02 D @  88° 43.02 D @  88° Astigmatism Astigmatism 1.53 D 1.53 D Equivalent K Average K Average K 44.89 D  44.89 D  Steep K Steep K 45.66 D @ 178° 45.66 D @ 178° Flat K Flat K 44.12 D @  88° 44.12 D @  88° Astigmatim Astigmatim 1.53 D 1.53 D (n=1.336) (n=1.336) Posterior SimK Average K Average K -6.54 D (6.12 mm)  -6.54 D (6.12 mm)  Steep K Steep K -6.69 D (5.98 mm) @ 110° -6.69 D (5.98 mm) @ 110° Flat K Flat K -6.39 D (6.26 mm) @  20° -6.39 D (6.26 mm) @  20° Astigmatism Astigmatism -0.29 D -0.29 D QUALITY FACTORS QUALITY FACTORS Centration 93% Focus 100% Corneal Coverage 100% Stability 100% Posterior 100% NOTES NOTES SURFACE INDICES SURFACE INDICES Q (Asphericity) Q (Asphericity) 0.015 0.015 W2W/HVID W2W/HVID 11.0 mm 11.0 mm Pupil size Pupil size 1.80 mm 1.80 mm Pupil center Pupil center 0.30 mm @  14° 0.30 mm @  14° HOA HOA 0.591  0.591 μ μm m SRI SRI 0.239 0.239 SAI SAI 1.055 1.055 S/N ca1523 VERSION 2.5.0 DIAGNOSTIC REPORT DIAGNOSTIC REPORT A standard Cassini display that shows anterior, posterior, and total astigmatism

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