Small Incision Lenticule Extraction (SMILE)
Definition Small incision lenticule extraction (SMILE) is a laser refractive procedure in which a corneal stromal lenticule is created with a femtosecond laser and removed though a small incision in…
Ophthalmic Instruments
Definition From the earliest optical devices to the latest computerized imaging systems, technology has aided the clinician in the diagnosis and treatment of ocular disease. Key Features • The ability…
Excimer Laser Surface Ablation: Photorefractive Keratectomy (PRK), Laser Subepithelial Keratomileusis (LASEK), and Epi-LASIK
Definitions • Photorefractive keratectomy (PRK) is a procedure in which the cornea is reshaped using an excimer laser. PRK involves epithelial removal and photoablation of Bowman’s layer and anterior corneal…
Blepharitis
Definitions Blepharitis is a general term describing inflammation of the eyelids, whereas marginal blepharitis is inflammation of the eyelid margin, which can be subdivided into anterior and posterior blepharitis. Anterior…
Herpes Zoster Ophthalmicus
Definition Infection of varicella (chickenpox) in the ophthalmic division of the trigeminal dermatome most frequently affecting the nasociliary branch. Key Features • Herpes zoster ophthalmicus can affect any of the…
Intrastromal Corneal Ring Segments and Corneal Cross-Linking
Definitions • Corneal cross-linking (CXL) is a procedure combining corneal saturation with riboflavin and exposure to UV light to increase the amount of links between collagen fibers in the corneal…
Wavefront-Based Excimer Laser Refractive Surgery
Definition Wavefront-customized excimer laser refractive surgery corrects pre-existing lower- and higher-order aberrations. Wavefront-optimized treatments preserve pre-existing corneal optical aberrations (customizing for spherical aberration). Key Features • Zernike polynomials and Fourier…
Correction of Refractive Errors
Definition Refractive errors may be corrected by means of spectacles, contact lenses, orthokeratology, intraocular lens implants, and keratorefractive surgery. Key Features • Spectacle lens advantages: inexpensive; suitable to correct myopia,…
Clinical Refraction
Definition The neutralization of an individual’s refractive error using a variety of tests in which the patient’s responses determine the lens power that best produces a sharply focused image on…
Wavefront Optics and Aberrations of the Eye
Definition An aberration is any deviation of the path of a ray of light from geometrically ideal behavior. Key Features • Aberration theory is strictly confined to geometrical optics and…
