Ординатура / Офтальмология / Английские материалы / Contact Lenses in Ophthalmic Practice_Mannis, Zadnik. Coral-Ghanem, Kara-Jose_2003
.pdf190 T.B. Edrington and A. de Souza Pena
13.Soper JW, Jarrett A. Results of a systematic approach to fitting keratoconus and corneal transplants. Contact Lens Med Bull. 1972;5:50–59.
14.Raber IM. Use of CAB Soper cone contact lenses in keratoconus. CLAO J. 1983;9:237–240.
15.Edrington TB, Barr JT, Zadnik K, et al. Standardized rigid contact lens fitting protocol for keratoconus. Optom Vis Sci. 1996;73:369–375.
16.Caroline PJ, Norman CW, Andre MP. The latest lens design for keratoconus.
Contact Lens Spectrum. 1997;12:36–41.
17.Betts AM, Mitchell GL, Zadnik K. Visual performance and comfort with the Rose K lens for keratoconus Optom Vis Sci. 2002;79:493–501.
18.Barr JT, Edrington TB, Fink BA, Weissman BA, Gordon MO. Factors associated with corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Cornea. 2000;19:501–507.
19.Soper JW. Fitting keratoconus with piggy-back and Saturn II lenses. Contact Lens Forum. 1986;11:25–30.
20.Tan DTH, Pullum KW, Buckley RJ. Medical applications of scleral contact lenses: gas-permeable scleral contact lenses. Cornea. 1995;14:130–137.
21.Pullum KW, Buckley RJ. A study of 530 patients referred for rigid gas permeable scleral contact lens assessment. Cornea. 1997;16:612–622.
22.Colin J, Cochener B, Savary G, Malet F. Correcting keratoconus with intracorneal rings J Cataract Refractive Surg. 2000;26:1117–1122.
23.Colin J, Cochener B, Savary G, Malet F, Holmes-Higgin DH. INTACS inserts for treating keratoconus. Ophthalmology. 2001;108:1409–1414.
24.Tuft SJ, Gregory WM, Buckley RJ. Acute corneal hydrops in keratoconus. Ophthalmology. 1994;101:1738–1743.
25.Grewal S, Laibson PR, Cohen EJ, Rapuano CJ. Acute hydrops in the corneal ectasias: associated factors and outcomes. Trans Am Ophthalmol Soc. 1999;97: 187–198.
26.Edrington TB, et al., a standardized rigid contact lens fitting protocol for keratoconus. Optom Vis Sci. 1996;73:369–375.
19
Cosmetic and Prosthetic
Contact Lenses
Paulo Ricardo de Oliveira and Jeffrey J. Walline
1.What is the difference between a cosmetic contact lens and a prosthetic contact lens?
A cosmetic contact lens is a tinted or painted contact lens used to enhance or alter the appearance of a normal eye. A prosthetic contact lens is a tinted or painted contact lens used to improve the appearance of a disfigured eye or to help correct the vision of a poorly functioning eye.1–3 The term tinted contact lenses can be used to refer to both cosmetic and prosthetic contact lenses.
2.Do all tinted contact lenses improve vision?
Tinted contact lenses may or may not have refractive power. Contact lenses used to improve visual acuity have a clear pupil or a pupil with a translucent tint. Contact lenses used to improve the appearance of a nonseeing eye may have a black, opaque pupil. Tinted contact lenses may be used to reduce glare or photophobia in order to improve vision. Cosmetic contact lenses may occasionally induce irregular astigmatism.4
3.What are the types of cosmetic contact lenses?
Cosmetic contact lenses are nearly always soft contact lenses because rigid gas permeable contact lenses may be too small and may move too much to cover the entire iris. Cosmetic contact lenses may have a translucent tint or an opaque tint.
4.What are the indications for cosmetic contact lenses?
Cosmetic contact lenses are typically fitted because the patient wants to alter the color of the iris. Translucent, cosmetic contact lenses typi-
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cally serve to enhance the natural color of the eye. They may make blue eyes a deeper blue, or they may make green eyes more obvious. Opaque cosmetic contact lenses may make brown eyes blue (Figure 19.1), blue eyes lavender, or may change the color of the eyes to aquamarine, amber, hazel, or any number of other colors. Opaque cosmetic contact lenses may also be used in theatrical settings to make the eyes appear more dramatic, ‘‘zombie-like,’’ or animal-like. Contact lenses are also available with professional team logos or with simple designs.
5.What are the types of prosthetic contact lenses?
Prosthetic contact lenses may be polymethylmethacrylate (PMMA) contact lenses, rigid gas permeable (RGP) contact lenses, scleral contact lenses, or soft contact lenses.
6.What are the general indications for prosthetic contact lenses?
Prosthetic contact lenses may be used to improve the appearance of a disfigured cornea, sclera, iris, or crystalline lens. Any part of the eye may become disfigured due to trauma, ocular disease, systemic health problems, or congenital defects. Prosthetic contact lenses may also be used to disguise an enucleated eye, to patch an eye during vision therapy, to reduce glare or photophobia (Figures 19.2 and 19.3), or to treat intractable binocular diplopia.
7.What are the indications and contraindications for PMMA or RGP prosthetic contact lenses?
Both PMMA and RGP prosthetic contact lenses can be painted with exquisite detail to match a healthy contralateral eye, whereas soft con-
Figure 19.1. A brown-eyed patient wearing a blue, opaque cosmetic contact lens on her left eye.
19. Cosmetic and Prosthetic Contact Lenses 193
Figure 19.2. This patient complained of glare and halos, especially in dim lighting, after radial keratotomy.
Figure 19.3. A prosthetic contact lens painted on the back surface with a 4-mm clear pupil to decrease glare and halos for the patient in Fig. 19.2.
tact lenses cannot be as individualized. Disfigured corneas often exhibit irregular astigmatism, and PMMA or RGP prosthetic lenses can correct poor vision due to irregular astigmatism while improving the appearance of the disfigured eye. Disfigured eyes with moderate to severe neovascularization should be fitted with highly oxygen-permeable, RGP prosthetic contact lenses because they allow maximal amounts of oxygen to reach the cornea. Because PMMA and RGP contact lenses are smaller, and because they move on the cornea more than soft contact lenses, they should not be used to mask anomalies that affect peripheral parts of the cornea or large portions of the anterior segment.
8.What are the indications and contraindications for fitting a scleral contact lens?
A scleral contact lens is indicated when a corneal contact lens will not center properly on the cornea or when one wishes to improve the appearance of the sclera. Scleral contact lenses require a greater level of
194 P.R. de Oliveira and J.J. Walline
expertise to fit them properly; fitting them requires substantial chair time, and they are available from only a limited number of sources, so they are relatively expensive. They should be used only after all other types of contact lenses have failed to correct the problem.
9.What are the indications and contraindications for fitting a soft prosthetic contact lens?
Soft, prosthetic contact lenses should be used when a significant proportion of the anterior eye is disfigured, when the patient is a previous soft contact lens wearer, or when the patient only wants to wear the contact lens occasionally. Soft contact lenses are contraindicated in eyes with moderate to advanced neovascularization, moderate to extreme dry eye, and irregular astigmatism. Soft contact lenses may also be difficult to handle for people with motor coordination problems.
10.How does one fit a PMMA or an RGP prosthetic contact lens?
A trial lens fitting will almost always be necessary on disfigured corneas. If possible, PMMA and RGP contact lenses should be fitted using keratometry readings and manifest refraction data. Keratometry readings are often not possible to obtain on disfigured eyes that require prosthetic contact lenses due to irregularities of the corneal surface. If only one cornea is severely affected, measuring the corneal curvature of the contralateral eye may yield a reasonable estimate for the initial contact lens parameters. Generally, PMMA or RGP prosthetic contact lenses should be fitted with a large diameter to cover the defect, and they should be fitted relatively tight to decrease the movement of the contact lens. Assessing the fluorescein pattern is often difficult or impossible on an opaque prosthetic contact lens. Particular attention should be paid to the centration and movement of the contact lens as well as to the corneal slit-lamp findings to determine whether the fit of the contact lens is appropriate.
11.How does one fit a scleral prosthetic contact lens?
Scleral prosthetic contact lenses can be fitted by taking an impression of the eye or by performing a trial fitting, but ocular impressions are rarely performed. Fitting a scleral contact lens is a two-step process. The first step is to approximate the radius of curvature of the sclera. Once an optimal scleral radius is achieved, the size and curvature of the optic zone should be determined. A refraction over the final trial lens should always be performed to determine the power of the contact lens.
19. Cosmetic and Prosthetic Contact Lenses 195
12.How does one fit a soft cosmetic or prosthetic contact lens?
Soft cosmetic or prosthetic lenses are fitted using trial lenses with varying base curves, diameters, thicknesses, and colors. The color of the contact lens should be determined compared to the contralateral eye in natural sunlight and under artificial lighting. If a contact lens is to be painted after the initial fitting, the flattest contact lens possible should be chosen because the painting process may cause the contact lens to tighten.
13.How does one disinfect soft cosmetic contact lenses?
There are specific criteria for each brand, and one should follow the recommendations of the manufacturer before choosing a method of disinfection. The tint may fade if hydrogen peroxide disinfecting solutions or alcohol-based daily cleaning solutions are used, but the recommended method of cleaning or disinfecting the contact lens varies for each brand of contact lens.
14.Does an opaque cosmetic contact lens with a clear pupil reduce the patient’s visual field?
In general, an opaque cosmetic contact lens with a clear pupil reduces the patient’s visual field minimally, if at all. A smaller pupil size will limit the amount of light that reaches the back of the eye. A patient may complain that the vision is too dim, especially in poorly lit situations.
15.How and when should topical medication be used in the presence of a cosmetic contact lens?
Topical medication in the form of drops can be used routinely, but a soft contact lens can be damaged by certain topical medications. If the patient is wearing a cosmetic contact lens, it is best to apply the medication at least 10 minutes before inserting the contact lens or after removing the contact lens. If medication instillation is necessary more often, the patient should be told to remove the contact lenses prior to drop instillation and to insert them after waiting for 10 minutes.
Prosthetic Contact Lens Case Report
M.S., a 40-year-old Caucasian male police officer, reported for an eye examination with complaints of glare and halos around lights, espe-
196 P.R. de Oliveira and J.J. Walline
cially in dim conditions, since undergoing bilateral radial keratotomy nearly 1 year earlier. He had been treated for glare and halos with varying concentrations of pilocarpine to constrict his pupils, which caused transient poor vision for 30 to 60 minutes. He reported a bout of iritis in the right eye 10 years ago, but he had no other significant personal or family ocular or systemic problems. He did not report any allergies or previous surgeries.
His uncorrected visual acuity was 20/30 1 in the right eye and 20/20 1 in the left eye. Manifest refraction was 0.25 1.75 035(20/15) in the right eye and 0.25 2.25 170 (20/20) in the left eye. His pupils were 7 mm in diameter in room light and 4 mm in diameter in bright light. He had 15 radial incision scars with a 2.5-mm clear zone in the right eye and eight radial keratotomy incision scars with a 3-mm clear zone in the left eye (Figure 19.2).
The patient was fitted with Durasoft 3 Colors contact lenses in both eyes to cover most of the radial incisions and to reduce the glare and halos. After 1 week of contact lens wear, the patient said that the contact lenses slightly reduced the glare but not enough to alleviate the discomfort. The contact lenses were mailed to Adventures in Colors (Denver, CO) to paint the back surface black with 2.0-mm clear pupil in each eye.
After the patient wore the contact lenses with the 2.0-mm clear pupil for 2 weeks, he reported significant reduction of the glare and halos, but he reported that his vision was too dim, especially when he worked at night. New contact lenses were ordered with a 3.0-mm clear pupil in the right eye and a 4.0-mm clear pupil in the left eye (Figure 19.3).
After wearing the contact lenses with larger pupils, the patient reported much better vision in dim situations without glare and halos. Visual fields were performed on the patient, and no reduction in peripheral vision was noted with the contact lenses.
References
1.Massare J, Freeman M. Cosmetic soft contact lenses. In: Kastl PR, ed. Contact Lenses—The CLAO Guide to Basic Science and Clinical Practice. Dubuque, IA: Kindall/Hunt Publishing, 1995:253–261.
2.Moreira S, Moreira H. Lentes de contato cosmeticas e proteticas. In: Moreira S, Moreira H, eds. Lentes de Contato. Rio de Janeiro: Cultura Medica, 1993:262–264.
3.Efron N. Tinted lenses. In: Efron N, ed. Contact Lens Practice, 1st ed. Boston: Butterworth-Heinemann, 2002.
4.Schanzer MC, Mehta RS, Arnold TP, Zuckerbrod SL, Koch DD. Irregular astigmatism induced by annular tinted contact lenses. CLAO J. 1989;15:207– 211.
20
Therapeutic Contact Lenses
Paulo Ricardo de Oliveira and Melissa D. Bailey
1.What are the indications for the use of a therapeutic contact lens?
●Pain reduction caused by defects or lesions of the corneal epithelium
●More rapid restoration and preservation of corneal epithelial integrity
●Protection of the cornea in cases of corneal drying
●Protection of the cornea in cases of mechanical injury secondary to entropion and trichiasis
●Restoration of the anterior chamber after shallowing caused by small corneal perforations
●Delivery of medications to the ocular surface
2.What are the primary indications for the use of a therapeutic contact lens?
●Abrasions, erosions, and corneal ulcers
●Filamentary keratitis
●Neurotrophic keratitis
●Neuroparalytic keratitis
●Herpes simplex keratitis
●Dry eye syndrome
●Ectatic dystrophies
●Corneal dystrophies with epithelial compromise
●Bullous keratopathy
●Entropion, trichiasis, and lid defects
●Corneal lacerations with small perforations
●Postoperative discomfort
●After suturing the cornea or surgical correction of lid injuries
3.How should one choose a therapeutic contact lens?
The choice of a therapeutic contact lens depends basically on the objective. The water content, thickness, oxygen transmissibility, diameter,
198 P.R. de Oliveira and M.D. Bailey
base curve, and power must be consistent with the problem that needs to be resolved. Collagen contact lenses are used when the eye care practitioner wants to soak the lens in a medication prior to applying the contact lens. Low-water-content contact lenses are used to prevent drying of the cornea. If the lens needs to be worn for an extended period of time, consider a silicone hydrogel lens that is designed to be worn on an extended basis.
4.What are the principal benefits of using a therapeutic contact lens?
●Alleviation of pain
●Treatment of corneal disease
●Improvement of visual acuity
5.What are the basic principles that must be observed when fitting a therapeutic contact lens?
To choose the base curve for the therapeutic contact lens, take readings of the patient’s central corneal curvature with a keratometer or corneal topographer. In the event that central corneal curvature readings are not available or that it is not possible to obtain this measurement due to the condition of the cornea, choose a lens with an average base curve. In general, a therapeutic contact lens should be fit tighter than usual, providing adherence and stabilization. The contact lens diameter should be fairly large, covering the entire cornea, with less mobility than normal. Nonetheless, try to conserve some tear exchange. A therapeutic contact lens should either be thin with low water content or thicker with high water content, depending on the indication and the need for oxygen transmissibility. The cornea should not be further traumatized by the contact lens, and the patient should report good comfort with the lens in place.
6.How should the therapeutic contact lens be maintained?
The frequency of examination visits to reassess the condition of a therapeutic contact lens depends on the ocular disorder under treatment. When the threat of corneal perforation is present or there is a loss of corneal sensation, the cornea should be observed daily. In cases of superficial keratitis, bullous keratopathy, or recurrent erosion, the patient can be seen weekly. The eye care practitioner must evaluate the condition of the contact lens and determine if replacement is necessary. Many manufacturers make recommendations about the frequency of lens replacement, and those recommendations should be considered. Practitioners often use ordinary disposable contact lenses as therapeu-
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tic contact lenses, and these lenses may be changed daily, weekly, every 2 weeks, or at the discretion of the doctor.1
7.How does one proceed when it is necessary to measure intraocular pressure during the use of a therapeutic contact lens?
The lens should be removed from the eye very carefully. If fluorescein is used for tonometry, the eye should be irrigated thoroughly afterward. Another possibility is to use non-contact tonometry, measuring the pressure with the lens on the eye. The intraocular pressure measurement obtained will be a few millimeters higher than without the lens. Intraocular pressure measurements can also be obtained with a handheld contact tonometer, such as the Tonopen , through the lens, without difficulty.
8.How and when should one use topical medications with a therapeutic contact lens?
Topical medication can be used as necessary. The use of topical antibiotic is recommended in the majority of cases. When possible, preparations without preservatives should be used to avoid toxic and sensitivity reactions. Artificial tears should be preservative-free when they are used several times a day and/or for a long period of time. Hypertonic solutions may cause dehydration of the therapeutic contact lens and lead to tight-lens syndrome in these patients.
9.When is a therapeutic contact lens indicated for bullous keratopathy?
A therapeutic lens is indicated for relief of pain. The use is of short duration, generally while the patient is awaiting corneal transplantation or a surface stabilization procedure. In such cases, the lens should be used for as short a time as possible to avoid secondary infection or neovascularization.
A therapeutic contact lens can be used for longer periods in eyes with no hope of visual recuperation. In such cases, one may observe the development of neovascularization and formation of fibrosis under Bowman’s membrane, which diminishes bullous formation, permitting discontinuation of the therapeutic lens.
10.How long are therapeutic contact lenses used for recurrent corneal erosion?
It generally takes a period of several months for the epithelial cells of the cornea to form a firm adhesion to the epithelial basement mem-