Management of Astigmatism - An overview Dr. Haripriya Aravind Aravind Eye Hospital, Madurai

Why? Surgery of cataract is now Keratolenticular Refractive surgery Post op absence of optical correction desired Objective is complicated when high astigmatism exists

Definition It is condition of refraction where in, a point focus of light cannot be formed upon retina

Types Regular astigmatism Irregular astigmatism Principal meridians are perpendicular Irregular astigmatism Principal meridians are not perpendicular

Regular Astigmatism With the rule astigmatism (W.T.R) Vertical corneal meridian is steeper Against the rule astigmatism (A.T.R) Horizontal meridian is steeper WTR 60° - 120° ATR 150-300° - 180° - 30°

Regular Astigmatism Oblique astigmatism 90° 120° 60° 150° 30° 0° 180°

Measurement Retinoscopy Keratometry Corneal topography instruments

Astigmatism in Cataract Surgery Pre-existing astigmatism Cautery Incision characteristics Suture characteristics Postoperative factors use of steroids

Preexisting Astigmatism Final astigmatic error depends to a large extent on pre-operative astigmatism Place the incision at steeper meridian Modify wound characteristics

Cautery Excessive cautery causes Scleral shrinkage Scleral necrosis

Incision characteristics Location Length Configuration of the wound

Location of the Wound More anteriorly located wound - more induced astigmatism Laterally located wound - less decay in A.T.R

Wound Length of Wound Configuration of Wound Astigmatism  length3 External configuration Internal configuration

External configuration

INTERNAL CONFIGURATION d b a - b = beveled c - d = Perpendicular Three plane

INCISIONAL FUNNEL

Suture Characteristics Length Depth Tightness Suture Material Suture Orientation

Length :Zone of compression A B A = B No Astigmatism

A B A > B WTR

A B A < B ATR

Tightness Of Suture Tight suture - increase in W.T.R Loose suture - increase wound separation - increase A.T.R

Effect of Suture on Corneal Contour

Effect of Suture on Corneal Contour

Depth Of Suture Bite Superficial suture - cut through tissue - increase A.T.R Finer suture like 10-0 Nylon to be placed at 90% depth

Suture Characteristics Suture material Non-absorbable suture causes less A.T.R decay Silk suture degrades within 3 months - increase A.T.R Suture orientation Non-radial sutures cause lateral displacement - increase astigmatism

Correction of Post Cataract Surgery Astigmatism Suture relaxation Spectacles Contact lens LASIK Surgery

Management Spectacles Suture relaxation Main stay of treatment for majority of patients Suture relaxation Preferably after 3 months Indicated when > 3 D W.T.R is present

Contact Lens Indications Variety Fitting Irregular post operative astigmatism Variety Hard contact lens Fitting Difficult (especially in high astigmatism)

Surgery Astigmatic keratotomy Peripheral arcuate incisions Opposite clear corneal incision Toric IOL

Relaxing Incision - Principle

Barrier Concept

Coupling Flat Steeper Steep Flatter

Astigmatic keratotomy principles

Incisions in Astigmatic Keratotomy

Astigmatic Keratotomy Timing Depends on surgeons During cataract surgery A few months postop when postop refraction stabilises Indications Moderate to high level of astigmatism Less aggressive management in with the rule astigmatism cases Nomogram

Thornton Nomogram

Limbal Relaxing Incision Corrects about 0.5 to 4 diopters of astigmatism Can be performed at the time of cataract surgery or as an independent procedure

Modified Gills and Cayton Nomogram

Limbal Relaxing Incision Location Depth Role of Pachymetry

Opposite clear corneal incision Jeffrey Lever & Elie Dahan Creating a second penetrating clear corneal incision opposite that made for IOL implantation

How does it work? Penetrating corneal wound of certain length provokes astigmatism TCCT-3.0mm 0.28-0.53D 5.2mm 0.50-0.84D Adding an identical CCI opposite first enhances the flattening effect on the cornea Placed on steepest axis and is self sealing

Toric IOL Toric IOLs are created by incorporating a cylindrical correction on a spherical optic Single-piece, plate haptic, foldable intraocular lenses

LASIK A thin surface flap of the cornea is created using a microkeratome to expose underlying tissues and the excimer laser beam is applied to create the refractive ablation Expense and non availability

“Correcting astigmatism is not a procedure that doctors are usually paid for It is a value-added service because it means less dependency on glasses and better quality of vision”

Thank You