PROSTHETIC LENSES

Soft Contact Lenses for Prosthetic Fitting

Prosthetic lenses fulfill a functional and a cosmetic need for damaged or disfigured eyes.

By Dawn Lam, BSc, MSc, OD, FAAO

Colored soft contact lenses have the ability to influence and change perceived eye colors. There are two distinct types of patients who can benefit from colored soft contact lenses: those who have disfigured or diseased eyes, and those who have normal eyes but are looking for a day-to-day cosmetic change.

Patients who are looking for a cosmetic change to their iris can be fit into frequent replacement colored soft lenses (see sidebar on page 39). These lenses are available in a limited range of colors and parameters, and they have pre-determined iris and pupil diameters. Several of the major contact lens manufacturers offer these options.

Patients who need to mask an ocular disfigurement or who have certain eye diseases should be fit into a prosthetic soft contact lens. These patients need a lens that contains pigments dense enough to hide a scar or injury to the ocular surface. They may also need a prosthetic lens to fulfill a functional need (for example, iris or pupil occlusion). Prosthetic evaluations can be very rewarding, but there are many factors to consider for success.

Indications

Common indications for prosthetic soft contact lenses include aniridia, iris coloboma, ocular albinism, leukocoria, leukoma, diplopia, micro-cornea, and iris atrophy. Most patients who have iris irregularities also have symptoms of glare and photophobia. They would need a contact lens that provides iris occlusion, and their symptoms will be reduced as a result of the smaller pupil diameter.

Patients who have scarred or white opacified corneal abnormalities are usually self-conscious of their physical appearance. Patients who have these abnormalities will typically have little to no light perception, so vision is not usually their primary goal. They would benefit from a lens that can mask the ocular disfigurement. The patients’ functional need will dictate which type of prosthetic contact lens is best suited for them.

Iris and Pupil Occlusion

An iris occlusion prosthetic contact lens has iris pigment on the front surface (Figure 1a) and a black backing on the back surface (Figure 1b). These lenses can have varying pupil diameters, with a clear/open pupil or a black/closed pupil. Iris occlusion lenses are ideal for patients who have fixed, dilated pupils and symptoms of glare and photophobia. It is not always necessary to incorporate iris pigment to the front surface of the lens. Patients who have dark iris colors may be able to attain a suitable cosmetic match with a simple black iris occlusion lens (Figure 2-A).

Figure 1a. An iris occlusion lens with the iris color to match a patient’s natural iris color.

Figure 1b. An iris occlusion lens showing the black iris backing.

Figure 2. Clockwise from top: (A) an iris occlusion lens with an open pupil; (B) a pupil occlusion lens with a translucent, tinted iris; (C) both an iris and pupil occlusion tinted lens; (D) a pupil occlusion lens with a translucent, tinted iris; and (E) a pupil occlusion lens with a clear iris.

A pupil-occluding prosthetic contact lens has an opaque (black) pupil area and either a clear (Figure 2-E) or pigmented iris (Figures 2-B and 2-D). This type of lens does not provide any vision, but is ideal for patients trying to hide a white pupil, an opaque central corneal opacity, or for vision occlusion. Prosthetic contact lenses can be designed with both iris and pupil occlusion (Figure 2).

Pupil diameters can be designated to match a patient’s normal eye. In an iris occlusion lens, a small diameter open pupil will reduce symptoms of glare and photophobia; however, as the diameter of the pupil is reduced, the patient’s field of view is also restricted. This restriction can be bothersome to some patients, and a compromise is needed to balance visual comfort (less glare) and patients’ field of view.

An important consideration is patients’ daily activities. For a patient who spends the majority of his time outdoors, match the final pupil diameter to his normal pupil in bright illumination; for a patient who spends the majority of his time indoors, match the final pupil diameter to his normal pupil in dim illumination. Although not a necessity, when a pupil-occluding contact lens is needed, an associated iris color match can be designated to match the natural iris color.

Types of Prosthetic Contact Lenses

Many laboratories offer prosthetic soft contact lenses, which can be classified into three general types:

1) Tinted, translucent lenses in which there is a homogenous color throughout the iris template on the lens.

2) Computer-generated, printed lenses in which the color is pre-determined.

3) Hand-painted lenses in which iris color and diameters are completely custom.

All prosthetic soft contact lenses are replaced annually. Depending on the contact lens type, patients can be prescribed hydrogen peroxide or multipurpose contact lens care solutions.

Tinted Lenses Tinted lenses offer a homogenous, translucent color throughout the iris template (Figures 2 and 3). Details such as iris nevi, corneal arcus, and pupillary ruffs cannot be added to a tinted lens.

Figure 3. A variety of tinted, translucent lenses.

Consultation with the laboratory is necessary to determine availability of iris and pupil diameters. Usually, pupil and iris diameters can be customized, and an open or black pupil can be added to tinted lenses, if warranted. Complete pupil occlusion can be difficult in some tinted prosthetic contact lens designs if the black pupil pigment is not dense enough. Iris occlusion is not always possible; these contact lenses are translucent, and a full iris occlusion will result in a black iris (Figure 2-A).

Note: with these types of tinted prosthetic contact lenses, you can designate either the iris color or the black iris back but not both. In addition, the iris pigment in these contact lenses is usually not dense enough for patients who have light-colored irises to achieve a good cosmetic match. For such patients, consider printed or hand-painted prosthetic contact lenses in which iris details are possible to aid in the overall iris color match.

An alternative use for translucent tinted prosthetic contact lenses would be for low vision patients who need to wear a dark filter to improve visual function. Some trial and error may be necessary to achieve the correct tint, and patients should be educated that the lens may alter their perceived iris color, especially in patients who have lighter-colored eyes.

Computer-Generated Lenses Computer-generated prosthetic contact lenses have pre-determined iris colors and diameters (Figure 4). Some designs allow for layering of different colors to achieve the desired iris color effect. This type of contact lens is reproducible and provides good repeatability.

Figure 4. Examples of computer-generated or printed lenses. All of these lenses have a clear iris back. The lenses on the left have open pupils, and the lenses on the right have black pupils.

Full iris or pupil occlusion is possible by specifying a black iris backing while also specifying the appropriate front iris color for the patient. A black iris backing will provide patients with full iris occlusion, and a clear iris backing will provide patients with a partial iris occlusion (Figures 5-A and 5-B). It should be noted that a black iris backing can influence the perceived iris detail and color on the front of the lens, which needs to be taken into consideration when color matching. Unlike tinted prosthetic contact lenses in which iris and pupil diameters are customizable, for computer-generated lenses there are limitations to the template sizes available. In addition, the pre-determined range of colors may not be suitable for every patient.

Figure 5. The front and back of computer-generated prosthetic lenses with a clear iris backing (A) and black iris backing (B). Note that the blue iris color on the front of the lens is the same computer-generated color, but the overall perceived color is different because of the iris backing.

Hand-Painted Lenses Hand-painted prosthetic contact lenses are completely custom (Figures 6-A and 6-B), so you must consult the laboratory prior to fitting a patient. They are available in any iris and pupil diameter. A photo of the patient’s normal eye needs to be sent to the laboratory so that the iris color and details can be custom painted to match. The laboratory will paint the iris onto a clear contact lens, and a black or a white iris backing can be specified. When ordering these contact lenses, a black iris backing (iris occlusion) will cause the surface color to look darker and deeper versus a white iris backing. Be sure to communicate to the laboratory at the beginning of the ordering process whether a patient will need a black iris backing to reduce glare and photophobia. Hand-painted prosthetic contact lenses provide the most opportunities for customizing to suit each patient’s needs.

Figure 6. Examples of hand-painted prosthetic contact lenses.

Prosthetic Soft Contact Lens Evaluation

Color Matching The first consideration during a prosthetic contact lens fitting is determining the patient’s natural iris color. The patient should be evaluated in an examination room, and privacy should be maintained. Best results are obtained when room lighting is consistent at each follow-up visit. Ideally, the examination room walls should be a neutral grey color. You should have access to both indoor and outdoor illumination to evaluate iris colors. To ensure accurate iris color match from one week to the next, instruct the patient to wear white or black clothing; a white or black cloth covering kept in the office can also be laid over the patient’s clothing.

In a busy prosthetic contact lens practice, it would be advantageous to have a series of tinted prosthetic contact lenses from your laboratory of choice to be used as the basis of a fitting set. A fitting set consisting of light, medium, and dark iris colors would provide a good starting point when color matching to a patient’s natural iris color.

If a hand-painted prosthetic contact lens is needed, then a photo printer is necessary because digital images will have different color tones on different computer monitors. Once a photo is printed, the iris color in the photo can be compared to the patient’s natural iris color while the patient is in the examination room.

The choices are more plentiful for brown eyes. Tinted, printed, and hand-painted prosthetic contact lenses are all potential options for such patients. Green, grey, or blue eyes are limited to a printed or a hand-painted contact lens to ensure a good cosmetic match. In most cases, the pigment in a tinted contact lens would not be dense enough to conceal scars for light-colored irises.

Prosthetic lenses are all prescribed for annual replacement. Advise patients that tinted and hand-painted contact lenses gradually fade over a 12-month period. Computer-generated lenses are less likely to fade, but should still be replaced annually. Consult with the laboratories for recommended contact lens care products; some can accelerate the contact lens fading process. If a particular lens care product is contraindicated, avoid using that lens care solution even during the clear lens fitting process, and make sure to educate the patient appropriately. Usually, a lens care product is contraindicated because of a particular ingredient or preservative.

Contact Lens Parameters The second consideration is the patient’s vision. A patient who has a refractive error will need his refractive correction incorporated into the contact lens powers. In addition to base curve, lens power, vision, and overall diameter, also document the normal iris color, iris diameter, and pupil diameter (in dim and bright illumination). The final lens pupil diameter will be dictated by a patient’s occupation and activities of daily living.

The soft contact lens should be comfortable and should fit well on the patient’s ocular surface. Patients who have irregular corneal surfaces may require custom base curve adjustments. Document contact lens centration, and adjust the overall lens diameter if possible to ensure full coverage of the cornea. A contact lens that does not center well on the cornea will expose the underlying ocular tissues and will not result in an orthophoric eye position. Increasing the diameter may be necessary to provide a large enough contact lens to hide any ocular abnormality (Figure 7-A). If the center of the contact lens does not correspond to an orthophoric position for the patient, then a hand-painted prosthetic lens is the only choice, as this allows the iris artistry to be decentered (Figure 7-B).

Figure 7. When the iris artistry needs to be decentered (A), a large-diameter soft lens (B) can be fitted and painted to match the patient’s natural iris colors.

Although a soft contact lens will not change the dimensions of the palpebral fissures, the vertical palpebral fissure opening should be measured and compared between the two eyes. This documentation can be monitored over time.

Consult the laboratory with the first step of the lens order. Because the majority of prosthetic contact lenses are not trials, each contact lens will have a material fee. Silicone hydrogel contact lenses cannot be tinted and, as such, patients are limited to traditional hydrogel contact lenses.

Whenever possible, order a clear contact lens with the appropriate contact lens parameters to confirm fit, vision, and comfort. Re-ordering a clear contact lens to adjust the parameters is more cost efficient compared to re-ordering a custom-tinted prosthetic contact lens. When the clear contact lens fit is finalized, send the contact lens that the patient has been successfully wearing to the lab for the final color to be incorporated.

In addition, some laboratories require patients to be fit into a contact lens of the laboratory’s choosing. Success is more easily achieved if the laboratory guidelines are followed. Often, the only requirement is a 55% water content hydrogel contact lens. If this is the case, you can choose from a number of custom annually replaced contact lenses. Such clear lenses are available in base curve radii of 6.0mm to 11.0mm and in overall lens diameters from 10.0mm to 24.0mm; sometimes, further customization is possible. These contact lenses also are available in both sphere and toric lens designs.

Safety or protective eyewear is important for all prosthetic lens patients. In addition, power in the spectacle lens can be adjusted to help magnify or minimize a disfigured eye as needed. For example, a patient who has a smaller ocular socket and eyeball may benefit from a plus-power spectacle lens to provide good symmetry in size between the two eyes.

Type of Disfigurement The final consideration is the type of ocular disfigurement. Does the patient have an opacified cornea or an iris abnormality? A patient who has an opacified cornea will likely need both a pupil and iris occlusion contact lens. A patient who has an iris abnormality will need an iris occlusion contact lens with an open pupil.

Cases in Point

Case #1: Tinted Lens A 75-year-old female with a history of cataract removal and a subsequent retinal detachment presented with a white opacified cornea and complaints of being self conscious of her physical appearance. Our evaluation confirmed no light perception, an opacified cornea, and a relatively equal palpebral fissure opening (Figure 8-A). We trialed both tinted and computer-generated prosthetic soft contact lenses.

Figure 8. A patient who has a left opacified cornea before prosthetic lens fitting (A), and the same patient now wearing a tinted translucent prosthetic lens (B).

Although the computer-generated lens was able to provide a good color match, the iris diameter of 12.0mm was too large compared to the patient’s normal right eye (11.5mm). A tinted lens also provided a good color match, and the availability of different iris and pupil diameters provided the customization that this patient needed. A tinted, translucent lens with an 11.5mm iris diameter and 3.5mm black pupil diameter was finalized for this patient (Figure 8-B).

Case #2: Hand-Painted Lens A 63-year-old male patient presented with a history of a traumatic iris injury at the age of 4 years. He reported cataract removal at the age of 8, and he is currently best corrected to 20/400. Our examination confirmed that this patient had a fixed, dilated pupil (Figure 9-A). He had symptoms of glare and photophobia.

Figure 9. A patient who has an irregular pupil secondary to iris trauma (A), and the same patient now wearing a hand-painted prosthetic lens (B).

The patient’s natural iris was a light blue-grey color. We successfully matched the patient in a hand-painted prosthetic lens with an 11.5mm iris diameter, black iris backing, and a 3.5mm open pupil to preserve his 20/400 vision. We also requested a light white opaque sclera to help mask the underlying eye color because of a slight lens decentration (Figure 9-B).

Case #3: Computer-Generated Printed Lens A 75-year-old male patient presented with complaints of glare and poor vision from a left traumatic iris injury. Our examination confirmed that he had a fixed, dilated pupil and was best corrected to 20/40. The patient is currently having difficulties with glare and diplopia (Figure 10-A). He was unable to tolerate a pupil occlusion lens on his left eye.

Figure 10. A patient who has an irregular pupil secondary to iris trauma (A), and the same patient now wearing a computer-generated printed prosthetic lens (B).

Currently, the patient is wearing a printed prosthetic lens with a black iris backing, blue iris color, 12.0mm iris diameter, and 4.5mm open pupil (Figure 10-B). He is also wearing spectacles with prisms ground in to eliminate his symptoms of diplopia. CLS