Corneal High-Order Aberrations in Corneal High-Order Aberrations in KeratoconusKeratoconusJuan C. Arciniega, MD; Engy M. Mohamed, MD; R. Wayne Bowman, MD; Steven Verity, MD; Juan C. Arciniega, MD; Engy M. Mohamed, MD; R. Wayne Bowman, MD; Steven Verity, MD;

James P. McCulley, MD, FRCOphth (UK).James P. McCulley, MD, FRCOphth (UK).

Department of Ophthalmology, The University of Texas Southwestern Medical Center at Department of Ophthalmology, The University of Texas Southwestern Medical Center at Dallas, Texas. USA.Dallas, Texas. USA.

This study was supported in part by grants NIH EY12430, EY016664 and an unrestricted grant from This study was supported in part by grants NIH EY12430, EY016664 and an unrestricted grant from the Research to Prevent Blindness, New York, New York. the Research to Prevent Blindness, New York, New York.

Financial DisclosureFinancial Disclosure: :

Juan C. Arciniega, Engy M. Mohamed, Steven Verity and R. Wayne Bowman have no Juan C. Arciniega, Engy M. Mohamed, Steven Verity and R. Wayne Bowman have no commercial relationships. commercial relationships.

James P. McCulley is a consultant of Alcon Inc.James P. McCulley is a consultant of Alcon Inc.

BackgroundBackground

Keratoconus is a condition in which the cornea assumes a conical shape Keratoconus is a condition in which the cornea assumes a conical shape as a result of non-inflammatory progressive corneal thinning. The as a result of non-inflammatory progressive corneal thinning. The thinning and protrusion in keratoconus induces irregular astigmatism thinning and protrusion in keratoconus induces irregular astigmatism with and without myopia resulting in mild to marked impairment in both with and without myopia resulting in mild to marked impairment in both quantity and quality of vision. It is a progressive disease ultimately quantity and quality of vision. It is a progressive disease ultimately affecting both eyes, although only one eye may be affected initially.affecting both eyes, although only one eye may be affected initially.11

1) Kanski Jack, Clinical Ophthalmology. Sixth edition, Elsevier, 2007

To evaluate the use of the anterior and posterior corneal surface high-To evaluate the use of the anterior and posterior corneal surface high-order aberrations (HOAs) as a tool to detect and grade keratoconus using order aberrations (HOAs) as a tool to detect and grade keratoconus using the Pentacam™.the Pentacam™.

PurposePurpose

MethodsMethods

A retrospective study of 111 eyes (62 patients; 33 males) was performed. A retrospective study of 111 eyes (62 patients; 33 males) was performed. The eyes were divided into 5 groups: suspect group and four other groups The eyes were divided into 5 groups: suspect group and four other groups according to the Amsler-Krumeich classification of keratoconus: stage I to according to the Amsler-Krumeich classification of keratoconus: stage I to stage IV groups. Anterior and posterior corneal HOAs were obtained using stage IV groups. Anterior and posterior corneal HOAs were obtained using the software provided by the Pentacam™ system.the software provided by the Pentacam™ system.

MethodsMethodsThe Amsler-Krumeich classificationThe Amsler-Krumeich classification11 includes the following stages: includes the following stages:

Stage I• Eccentric steeping• Myopia and astigmatism < 5.00 D•Mean central K readings < 48.00 D

Stage II

• Myopia and astigmatism from 5.00 to 8.00 D• Mean central K readings < 53.00 D•Absence of scarring • Minimum corneal thickness >400 µm.

Stage III

•Myopia and astigmatism from 8.00 to 10.00 D• Mean central K readings >53.00 D•Absence of scarring • Minimum corneal thickness 300 to 400 µm.

Stage IV

• Refraction not measurable• Mean central K readings >55.00 D• Central corneal scarring• Minimum corneal thickness 200 µm

1) Alió Jorge, Corneal Higher Order Aberrations: A Method to Grade Keratoconus. J Refract Surg. Vol. 22 No. 6 June 2006

Methods Methods

Anterior & Posterior Anterior & Posterior Zernike (Z) coefficients Zernike (Z) coefficients were used from Zwere used from Z33 to Z to Z66 to calculate:to calculate:

• Coma-like aberrationComa-like aberration• Spherical-like aberrationSpherical-like aberration• Residual aberrationsResidual aberrations

Results Results The mean age of patients was 49.4±6.7 years. The mean age of patients was 49.4±6.7 years. The mean keratometric value was 43.30±14 D The mean keratometric value was 43.30±14 D The mean thinnest point of corneal thickness was 450.8±87µm. The mean thinnest point of corneal thickness was 450.8±87µm.

Number of Patients 62

Eye number 111

Right eye 58

Left eye 53

Males 33

Females 29

Stage I 43

Stage II 24

Stage III 8

Stage IV 21

Suspect 15

ResultsResults

Patients DemographicsPatients Demographics

Suspect Stage I Stage II Stage III Stage IV

Age 41.9±18.5 44.5±11.8 41.9±16.6 43.1±15.9 43.9±12

Mean keratometric value 43.6±1.9 44.8±1.9 49.9±1.4 53.8±0.55 60.5±5.3

Corneal thickness 519.8±40.6 490.4±44.4 437.2±45.1 413.6±74.1 349.9±117

Sphere -4.4±3.3 -5.1±3.5 -9.7±3.2 -8.7±3.7 -9.7±4.7

Cylinder 2.3±1.4 3.5±1.9 2.6±2.5 4.5±1.8 4.5±3

Spherical equivalent -3.2±3.1 -3.4±3.4 -5.5±3.3 -6.5±4 -7.4±4

ResultsResults

Posterior coma-like aberration was the highest posterior HOAs among Posterior coma-like aberration was the highest posterior HOAs among all the groups and anterior coma-like aberration was the highest of all the groups and anterior coma-like aberration was the highest of anterior HOAs among all groups except for the suspect group which anterior HOAs among all groups except for the suspect group which had the anterior spherical-like aberration as the highest.had the anterior spherical-like aberration as the highest.

Anterior coma-like aberrations increased progressively with the groups Anterior coma-like aberrations increased progressively with the groups while the posterior coma-like aberrations did not show a gradually while the posterior coma-like aberrations did not show a gradually increase.increase.

ResultsResults

ConclusionConclusion

Corneal higher-order aberrations, especially coma-like aberrations, are Corneal higher-order aberrations, especially coma-like aberrations, are significantly higher in eyes with keratoconus than in keratoconus significantly higher in eyes with keratoconus than in keratoconus suspects. Only anterior coma-like aberrations measured by Pentacam™ suspects. Only anterior coma-like aberrations measured by Pentacam™ were best in the early detection and grading of keratoconus.were best in the early detection and grading of keratoconus.