The Special Sense Organs and Their Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
Disorders of the visual senses are usually referred to a specialist in treating eye disorders. An ophthalmologist or oculist is a physician who specializes in diseases and surgery of the eye. An optometrist is qualified to examine the eyes for vision problems and eye disorders and to prescribe lenses and other optical aids. The specialist who fills prescriptions for lenses, dispenses the eyeglasses, and makes and fits contact lens is an optician. Radial keratotomy (kerat = cornea, -otomy = incision) is a commonly used corrective surgical technique. A newer method utilizes a laser device and is referred to as photoreflective keratotorny. A keratoplasty, sometimes called a corneal transplant, involves replacing a section of diseased cornea with a normal one.
Preclinical Toxicology/Safety Considerations in the Development of Ophthalmic Drugs and Devices
David W. Hobson in Dermal and Ocular Toxicology, 2020
Evaluation of the strength and ability of the corneal stroma to heal and withstand trauma is extremely important in evaluating the effects of topical and intraocular formulations. This impacts on postoperative healing of corneal transplants, cataracts, and refractive surgeries such as radial keratotomy and epikeratophakia. In this technique a 9 mm corneal incision is placed in the central cornea and closed with four interrupted 10.0 nylon sutures. The cornea is allowed to heal for a predetermined period of time (usually 6 to 9 days). At this time the rabbit is humanely euthanized and a needle is placed in the anterior chamber which is attached to an infusion pump. Another needle is placed in the anterior chamber which is attached to a pressure transducer and physiograph. As saline is pumped into the eye, the pressure increases and is recorded by the transducer and physiograph. The pressure increases until the incision fails, which is marked by a sudden decrease in monitored pressure. The peak of the pressure curve is called the bursting pressure.9 This pressure can be compared to others in corneas treated with test formulations, either topically or intraocularly. Steroids, for example, are known to decrease the bursting pressure of a corneal wound at various time points.
The Zero-Sum Game
Michael Fine, James W. Peters, Robert S. Lawrence in The Nature of Health, 2018
One might be inclined to argue that technology actually saves money, by simplifying care, sometimes shortening hospital stays or eliminating follow-up visits. On a case-by-case basis the argument is often sound. But simpler, faster, lower-cost medical treatments appeal to the consumer in us all. For example, where radial keratotomy seemed an exotic and rather frightening way to correct near-sightedness, its replacement, LASIK surgery, has grown by leaps and bounds: from 30,000 cases in 1995, to 950,000 in 1999, to an estimated 3.2 million in 2002.3 Economies of scale and the effects of competition have reduced the cost of the procedure in many markets, but it still costs many hundreds of dollars per eye. Multiply that by millions and it becomes crystal clear that we’re spending more overall on vision-improvement surgery. Is that so bad? Perhaps not. Perhaps eyeglasses and contact lenses are obsolete and should make way for something better, albeit more expensive. The point is, there is an added price. Multiplied by many such examples, technology adds cost. Sometimes the benefits are substantial; in many instances they are, at least, arguable.
Risk factors for complications during phacoemulsification cataract surgery
Published in Expert Review of Ophthalmology, 2020
Manpreet Kaur, Nithya Bhai, Jeewan S. Titiyal
Leaky wounds should be sutured at the end of surgery. In addition, it is preferable to suture the wound in cases with difficult anatomy such as high myopia, corneal ectasia, post-RK cases and healed keratitis. In corneas with topographical changes like keratoconus, temporal corneal incisions closer to the limbus that do not potentially disrupt the thinner ectatic cornea are preferred[19]. Wound creation can be complicated by induced astigmatism and progressive ectasia and may not result in a self-sealed wound. Sutured incisions are safer and provide an additional chance to improve refraction and regularize astigmatism in these cases [20–22]. In eyes with radial keratotomy (RK), the corneal incision should be at the posterior limbus in the gap between two RK cuts so as to avoid transection of the prior RK incisions. Placing a corneal suture over the RK scars, adjacent to the main incision stabilize and reduce the risk of dehiscence of RK cuts during phacoemulsification and have a better visual prognosis[23].. The appropriate size for a clear corneal incision should be based on the number of RK cuts[24].
Pneumotonometer Accuracy Using Manometric Measurements after Radial Keratotomy, Clear Corneal Incisions and Lamellar Dissection in Porcine Eyes
Published in Current Eye Research, 2020
Lauren A. Maloley, M. Reza Razeghinejad, Shane J. Havens, Vikas Gulati, Shan Fan, Robin High, Deepta A. Ghate
Study intervention comprised of three surgical techniques performed on 28 eyes: radial keratotomy incisions (8 eyes, Figure 2a), lamellar dissection (as in Deep Anterior Lamellar Keratoplasty) (10 eyes, Figure 2b), and clear corneal phacoemulsification incisions (10 eyes). Radial keratotomy was performed using calipers to mark the central corneal 3 mm zone and a circle 0.5–1 mm inside the limbus. Eight radial incisions were created starting at the outer edge of the central 3 mm circle and extending to the inner edge of the outer circle at approximately 2/3 depth of the cornea. To accomplish lamellar dissection, a 2 mm wide incision was made 1 mm anterior and parallel to the limbus with a depth of approximately 2/3 the corneal thickness. Lamellar dissection started at the base of the incision toward the center of the cornea and was completed in all directions using a cyclodialysis spatula. The entry wound was left without suture. Standard, full thickness, phacoemulsification incisions were made with a 2.4 mm incision at the limbal area in addition to a 1 mm side-port incision. All surgical procedures were performed by the same experienced surgeon (MR). All IOPm and IOPp measurements were repeated at each IOP level (10, 20, 30, and 40 mmHg) after performing the 3 corneal procedures described above.
Posterior chamber phakic IOLs vs. LASIK: benefits and complications
Published in Expert Review of Ophthalmology, 2019
Present-day refractive surgery is broadly divided into two types, keratorefractive surgery, in which the shape of the cornea is changed, and phakic intraocular lens surgery, in which a lens is implanted into the eye. Keratorefractive surgery started with the report by Fyodorov et al. on radial keratotomy in 1979 [1]. Then, at the beginning of the 1980s, excimer laser emerged, and in 1990, laser in situ keratomileusis (LASIK) was first reported [2]. Thus, the cornea could be transformed safely and quantitatively by any surgeon, and it became a standard refractive surgery procedure. In contrast, the concept that formed the basis of the phakic intraocular lens (pIOL) was first proposed in the 1950s. In 1986, Fechner et al. reported an iris-supported type, in 1987 Baikoff et al. reported an angle-supported type, and Fyodorov et al. reported a prototype of the posterior chamber pIOL. These three types of pIOLs have respectively advanced and been commercialized; however, the posterior chamber (pIOL) implantable Collamer lens (ICL, STAAR Surgical) is predominantly used. The ICL was developed as IC2020 by STAAR Surgical Inc. in 1993 on the basis of the fundamental study by the Russian group that included Fyodorov. It is a plate-type intraocular lens made from the Collamer copolymer and is transplanted into the posterior chamber, which is the space between the iris and lens. Although good visual function is obtained after surgery with ICL [3,4], it is associated with a risk of postoperative cataract [5]. In 2007, Shimizu [6] developed the Hole ICL (ICL KS-AquaPORT, STAAR), which improved postoperative complications, resulting in a rapid increase in the number of surgeries performed in recent years. The present article compared and reviewed the long-term clinical results, optical properties, and complications of LASIK and ICL, the two standard surgical options.
Related Knowledge Centers
- Epithelium
- Keratometer
- Connective Tissue
- Infection
- Fibroblast
- Refractive Surgery
- Near-Sightedness
- Ophthalmology
- Stroma of Cornea
- Far-Sightedness