A. E. Reynolds conceived of the ring (based on expansion and contraction) in 1978; Kera Associates was formed in 1980 to develop the ring and other concepts. In 1985, the first preclinical studies of Reynolds’s concept led to development of lens thickness as the means of achieving correction (as opposed to the expansion/ contraction model), and in 1986, Kera-Vision, Inc., was founded to focus solely on development of its ICR technology.

In 1991, to demonstrate the safety of the ICR in humans, researchers conducted a blind-eye trial in Brazil and a similar one in the United States shortly thereafter. Both studies demonstrated that the ICR could be safely inserted into the peripheral corneal stroma in humans, thereby flattening the central cornea; five-year follow-up demonstrated that the eye tolerated the ring well, even years after insertion. The first procedures on sighted human eyes were performed in Brazil in 1991 and in the United States in 1993 as part of a phase II study regulated by the U.S. Food and Drug Administration (FDA).

In 1995, KeraVision created intrastromal corneal ring segments (ICRS), an alternative design, and introduced them into clinical trials in the United States. A U.S. phase II study and a two-site European study were initiated in 1995. U.S. phase III (10 reporting sites) research was initiated in 1996. In April 1999, the FDA approved three sizes (0.25, 0.30, and 0.35 mm) of Intacs, the commercial name for ICRS. Intacs completely replaced the 360-degree ICR. Use of Intacs has eliminated incision-related healing complications that were noted with the 360-degree ICR. Surgeons have performed approximately 1,800 Intacs procedures clinically worldwide to date. As a nonlaser alternative that does not remove tissue from the central optical zone (OZ) and is both removable and replaceable, Intacs represent a new direction for refractive surgery.

Specifications

• two half-rings placed through a single, peripheral incision
  
• made of polymethylmethacrylate
  
• varying the thickness of Intacs changes corneal curvature and dioptric correction (a nearly linear relationship between the degree of flattening achieved and the device thickness)

Advantages

Indications and Inclusion Criteria

• reduction or elimination of mild myopia (–1.00 to –3.00 D spherical equivalent at the spectacle plane)
  
• age of 21 years or older
  
• documented stability of refraction, as demonstrated by less than 0.50 D of change for at least 12 months prior to the preoperative examination
  
• +1.00 D or less of astigmatism

Patient Education

• Assist the patient in choosing the best procedure for his or her refractive error.
  
• Advise patient of realistic visual expectations and potential postoperative visual problems, including the fact that the patient may not be totally independent of spectacle lenses, as a result of this or any other refractive procedure.
  
• Discuss the specific advantages, limitations, and potential complications of the selected refractive procedure at an early consultation (this can save time in the long run).
  
• Address patient’s concerns about permanently altering the eyes and the availability of options in the event that the patient is dissatisfied with the outcome.
  
• Discuss all known general surgical risks with patient.

Patient Preparation

• As with any surgical procedure, take precautions to minimize the risk of infection.
  
• Instruct the patient to discontinue application of eye makeup for 2 to 3 days before the procedure.
  
• Advise the patient to instill one drop of trimethoprim (Polytrim; Allergan, Inc., Irvine, CA) in the operative eye at bedtime on the night prior to the procedure.
  
• Instruct the patient to instill one drop of Polytrim every hour (a total of three applications) beginning 3 hr before the procedure.
  
• Ensure that the patient completes all administrative forms, including the patient consent form.

Preoperative Medications

• Valium (5-10 mg, 20-30 min before procedure)
  
• diclofenac sodium (Voltaren Ophthalmic; CIBA Vision, Atlanta, GA) drops (20-30 min prior to procedure)
  
• tetracaine (Cetacaine or Pontocain; apply drops upon entering operative suite)

Absolute Contraindications

Relative Contraindications

• pregnancy or nursing
  
• use of isotretinoin (Accutane; Roche Pharmaceuticals, Nutley, NJ), amiodarone (Cordarone, Wyeth-Ayerst Laboratories, Madison, NJ), and/or sumatriptan (Imitrex; Glaxo Wellcome, Inc., Research Triangle Park, NC)

Methods

Intraoperative Complications

Postoperative visits are usually scheduled for 1 day, 1 week, 1 month, 3 months, and 6 months after surgery.

Day of Surgery

• expected symptoms
  
  
  
  • mild to moderate discomfort/pain for a few hours after surgery (if pain is more severe, contact the surgeon)
    
  • foreign body sensation or “scratchiness” (common during the immediate postoperative period)
    
  • fluctuating vision during the first month
    
  • dry eyes for the first 2 to 3 months
  
  
• management
  
  
  
  • Apply an antibiotic-steroid combination ointment or solution (0.1% dexamethasone and 0.3% tobramycin or equivalent) to the operative eye at the end of the procedure.
    
  • Perform a slit-lamp examination (to observe the segment placement and incision closure and to verify tunnel depth).
    
  • Cover the operative eye with a clear shield (the patient should wear a shield at night for 1 week).
    
  • Provide the patient with postoperative instructions.
    
  • Prescribe analgesic medication (acetaminophen, paracetamol, or equivalent) for postoperative discomfort (prescribe other pain medication at your discretion).
    
  • Provide artificial tears as needed.
    
  • Recommend that the patient take a nap (patients will be photophobic and they should rest their eyes).
    
  • Prescribe postoperative medications [antibiotic-steroid combination solution (0.1% dexamethasone/0.3% tobramycin or equivalent], four times a day for 1 week.
    
  • Instruct the patient to watch for symptoms of infection (e.g., dull, aching pain or discomfort, with or without photophobia) at any point in the postoperative period.
    
  • Remind the patient to contact his or her doctor if any of these symptoms occur.
    
  • Advise the patient to avoid rubbing the eye (may lead to segment migration or improper healing of the incision).

The Immediate Postoperative Period (Days 1-7)

Expected Results

• good visual acuity (majority of patients see better than 20/40)
  
  
  
  • Advise patient that over the next 3 to 6 weeks visual acuity will be good but may fluctuate from day to day and even during the course of the day.
    
  • Advise patient who does not have 20/40 vision that refractive surgery procedures typically require some recovery time and that vision will most likely improve.
  
  
• good intraocular pressure
  
• possible astigmatism
  
  
  
  • No intervention is necessary.
  
  
• epithelium healing
  
  
  
  • Healing is usually complete and foreign-body sensation resolved by the end of the first week.

COMPLICATIONS Several complications may be observed during the first week of postoperative recovery.

Epithelial Defect

foreign body sensation (if epithelium has not yet healed)

photophobia

• findings
  
  
  
  • possible mild subconjunctival hemorrhage and/or chemosis remaining from the VCG
    
  • little to no intraocular inflammation
  
  
• management
  
  
  
  • Half of cases almost entirely resolve by the first postoperative day and most others completely resolve by day 3.
    
  • Attempt to bury suture knots, if not already done.
    
  • Provide a bandage contact lens to be worn until the defect heals.
    
  • If the epithelial defect is larger than 2×2 mm, use a bandage contact lens or mild patching. (Beware of excessive pressure on the dome of the cornea that could cause movement or malpositioning of the segments.)
    
  • Monitor bandage contact lens use (prolonged contact lens wear may aggravate superficial neovascularization to the superior aspect of the incision).
    
  • Discontinue the bandage contact lens as soon as the epithelial defect resolves or when limbal vascular buds form.

Filamentary Keratitis

• usually a single filament extending from the end of the incision (causes disproportionate discomfort to the patient)
  
• symptoms
  
  
  
  • foreign body sensation
    
  • photophobia
  
  
• findings
  
  
  
  • occasionally may develop as the epithelial defect heals
  
  
• management
  
  
  
  • Treat with debridement, hypertonic saline drops (5% sodium chloride), or a bandage contact lens.
    
  • See Epithelial Defects section for information about monitoring and removing bandage contact lenses.

Drug Toxicity and Allergies

• symptoms
  
  
  
  • foreign body sensation
    
  • eye irritation
  
  
• findings
  
  
  
  • superficial punctate keratitis
    
  • extensive chemosis [possible allergic reaction to topical medications unless surgery involved significant trauma (i.e., difficulty with VCG placement or prolonged application of the VCG)]
    
  • lid edema
    
  • lid erythema
  
  
• management
  
  
  
  • In the presence of severe conjunctival chemosis in the early postoperative period, shift topical medications to an increased dose of topical steroids.

Infection

Corneal Edema

• peripheral or central corneal edema and recurrent or extended corneal edema (rare)
  
• mild corneal edema from placement, removal, or replacement of Intacs or other refractive procedures (routine)
  
• symptoms
  
  
  
  • blurred vision
  
  
• management
  
  
  
  • Prescribe or increase the dosage of topical corticosteroids.

Suture-Induced Astigmatism

• symptoms (associated with induced astigmatism or undercorrection)
  
  
  
  • glare
    
  • halos
    
  • double images
    
  • blurred vision
  
  
• findings
  
  
  
  • with the rule astigmatism (not coupled)
    
  • steepening along the 90-degree meridian, which leads to additional steepening along the 180-degree meridian (perhaps from blunting of the typical flattening that occurs in the opposite meridian with suture-induced astigmatism)
    
  • For example, a −2.00 + 2.00 X 90-degree refraction prior to suture removal shifts to piano after suture removal.
    
  • undercorrection
    
  • use of 10-0 nylon, more than one suture, tight suture closure, wound dehydration during surgery, and wound maceration or excess manipulation during surgery (all increase risk)
  
  
• management
  
  
  
  • If induced astigmatism is at least 1.00 D, identify the probable source of the astigmatism.
    
  • Astigmatism related to over-tensioning of the incision sutures (i.e., with the rule astigmatism) typically diminishes over time.
    
  • If there is more than 1.00 D with the rule astigmatism and sutures are still in place after day 7, remove the sutures.
    
  • Address suture-induced astigmatism early if the incision is healed and does not stain with fluorescein.

The Intermediate Postoperative Period (Weeks 1-4)

Expected Results

• no ocular discomfort or inflammation
  
• uncorrected visual acuity (UCVA) typically better than 20/40 (fluctuates from day to day and during the course of a day, usually in proportion with the induced astigmatism)

Induced With-the-Rule Astigmatism

• a myopic shift in the spherical equivalent (Intacs may blunt the concomitant flattening usually seen with suture-induced astigmatism)
  
• symptoms
  
  
  
  • astigmatic blur
    
  • double vision
  
  
• findings
  
  
  
  • a long incision with limbal encroachment
    
  • visible incision and suture scarring
    
  • elliptical decentration
    
  • with the rule topographic changes
    
  • too tight sutures or those left in place too long (according to current clinical data, may result in prolonged or even permanent with-the-rule astigmatism, even after suture removal)
  
  
• management
  
  
  
  • Administer topical corticosteroids to carefully modulate overly aggressive wound healing during the initial postoperative period.
    
  • Reincise the original incision and suture loosely or leave the incision unsutured for those patients who have corneas that healed aggressively. (This strategy has had only very limited success in a very small number of patients with astigmatism. Available clinical data have not demonstrated consistent results.)
    
  • Selective suture removal may be necessary if the induced astigmatism is greater than 1.00 D at 2 weeks.
    
  • Remove sutures by 4 weeks.

Induced “Against-the-Rule” Astigmatism

• symptoms
  
  
  
  • double vision
    
  • astigmatic blur
  
  
• findings
  
  
  
  • “against-the-rule” topographic changes
    
  • incision wound gape
    
  • cysts
    
  • epithelial plugs
    
  • inadequate wound closure
    
  • wound trauma (e.g., blunt force or eye rubbing)
    
  • flatter than average preoperative asphericity
  
  
• management
  
  
  
  • Remove any epithelial cysts or plugs.
    
  • Debride the incision or reapproximate the wound edges and resuture the wound as appropriate.

Corneal Thinning

• symptoms
  
  
  
  • foreign body sensation
  
  
• findings
  
  
  
  • epithelial breakdown or staining over Intacs
    
  • shallow Intacs placement (typically when placed at <30% depth)
  
  
• management
  
  
  
  • Recommend early intervention to prevent corneal thinning.
    
  • Remove Intacs immediately.
  
  
• Make a new intrastromal tunnel at the appropriate depth (68% of pachymetry reading).
  
• Reposition Intacs.

Infiltrates

mechanical trauma

• management
  
  
  
  • Administer combined antibiotic and steroid treatment (even though some may self-resolve over time).

Intacs Displacement

• may be vertical or lateral
  
• symptoms
  
  
  
  • glare
    
  • starbursting
    
  • halo
    
  • variable visual acuity
  
  
• findings
  
  
  
  • inferior or superior placement or irregular astigmatism (vertical displacement)
    
  • inadequate centration mark during surgery, incomplete tunnel dissection, incomplete advancement of Intacs, aggressive eye rubbing by patient, or segment movement within the intrastromal tunnel (vertical decentration)
    
  • mismatched pupil center to surgical center of the Intacs, irregular topography, or irregular astigmatism (lateral displacement)
    
  • decentered intrastromal tunnel, poor VCG placement or loss of suction during surgery, aggressive eye rubbing by patient, oversized pocket superiorly, or removal of Intacs and replacement with segment movement within the intrastromal tunnel (lateral decentration)
  
  
• management
  
  
  
  • Replace Intacs and properly align the new lens on the pupillary center.

Large Pupils

• symptoms
  
  
  
  • Intacs edge visible to patient
    
  • glare
    
  • starbursting
  
  
• findings
  
  
  
  • large pupil in dark environment
    
  • mismatched pupil to surgical center of Intacs
    
  • poor Intacs placement
    
  • decentered intrastromal tunnel
    
  • segment movement within the intrastromal tunnel
  
  
• management
  
  
  
  • Carefully select patients to avoid large-pupil issues.
    
  • Remove or reposition the Intacs if decentration is the main issue (may self-resolve over time).

Epithelial Plug Formation in Incision

• management
  
  
  
  • Intervene as soon as possible after observing the plug.
    
  • Remove the incision sutures (if present) and debride and resuture the incision area.
    
  • Follow the patient closely for 2 weeks to ensure adequate incision closure.

The Late Postoperative Period (Month 2 and Beyond)

Between months 1 and 3 the surgeon should begin assessing whether the patient is satisfied with his or her vision and is “20/Happy.” Follow satisfied patients on a routine basis after the six-month examination.

Expected Results

COMPLICATIONS In general, late complications of Intacs placement are rare.

Intrastromal Tunnel Deposits

• generally appear between 3 and 12 months postoperatively
  
• findings
  
  
  
  • observed in 68% of the U.S. Phase III clinical trial patients at the month 12 exam
    
  • remain confined to the intrastromal tunnel (do not spread centrally into the visual axis)
    
  • rarely, lead to confluent accumulations of opalescent material limited entirely to the dissected intrastromal tunnel
    
  • may become visible to the naked eye
    
  • from month 6 to month 12, prevalence and levels of deposits remain stable
    
  • causes not yet conclusively established

Pannus and Deep Neovascularization

• findings
  
  
  
  • prior contact lens wear
    
  • preoperative pannus
    
  • incision extending to the limbal vessels during surgery
    
  • wound healing issues (e.g., neovascularization in incision)
    
  • loose sutures

Undercorrection or Overcorrection

• findings
  
  
  
  • vessel growth
  
  
• management
  
  
  
  • Before considering replacement, perform a cycloplegic refraction and evaluate topography.
    
  • Where appropriate, discuss options including replacement.
    
  • Prescribe topical corticosteroids to stop vessel growth once present.
    
  • Advanced vessel growth that does not respond to topical corticosteroids may require laser therapy to impede deep vessel growth.
    
  • Replace Intacs with thinner or thicker segments, depending on the residual refractive error (currently, insufficient data on efficacy of exchanging Intacs)
    
  • Remove Intacs.
    
  • See section on Removal and Replacement that follows.

Removal and Replacement

Intacs may be removed or replaced, unlike essentially permanent refractive techniques that directly cut or remove tissue and may be adjusted but not undone. Initial results of Intacs removal are very good although further analysis is needed. In FDA trials, only 6.9% of patients required removal in the first year.

Indications

• change in patient’s vision over time
  
• a clinically significant complication
  
• titration of the refractive effect with thicker or thinner Intacs

Expected Results

• within one line of preoperative BCVA
  
• no complications
  
• return of refraction to preoperative levels within 3 months (most cases)
  
• an additional effect because of replacement with thicker segments (6 procedures in FDA study)

Methods

Intacs insertion is the first new refractive surgery technology to appear since laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK). LASIK, PRK, and RK were originally used to treat higher myopic patients, leaving patients with low myopia with very low hopes for laser vision correction.

The use of Intacs, LASIK, and intraocular lenses (IOLs) will most likely overlap somewhat, just as glasses, contact lenses, and refractive surgery have. Surgeons may choose among them based on their skill level, patient profiles, and practice environment.

Laser In Situ Keratomileusis

There has been no formal study of LASIK after initial Intacs insertion or LASIK and then subsequent insertion of Intacs, and no supporting data are available. However, anecdotal reports suggest that LASIK is effective after Intacs removal.

Characteristics

Asbell PA, Ucakhan OO, Durrie DS, Lindstrom RL. Adjustability of refractive effect for corneal ring segments. J Refract Surg. 1999;15:627-631.

Burris TE, Baker PC, Ayer CT, et al. Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study. Cataract Refract Surg. 1993;9(suppl):182-187.

Fleming JF, Lovisolo CF. Intrastromal corneal ring segments in a patient with previous laser in situ keratomileusis. J Refract Surg. 2000;16: 365-367.

Twa MD, Hurst TJ, Walker JG, Waring GO, Schanzlin DJ. Diurnal stability of refraction after implantation with intracorneal ring segments. J Cataract Refract Surg 2000;26:516-523.

Twa MD, Karpecki PM, King BJ, Linn SH, Durrie DS, Schanzlin DJ. One-year results from the phase III investigation of the KeraVision Intacs. J Am Optom Assoc. 1999;70:515-524.