Radial keratotomy: complications management
- 1 Corneal perforations
- 2 Incisions and decentration
- 3 Overcorrection
- 4 Undercorrection
- 5 Astigmatism
- 6 Premature presbyopia
- 7 Contact lens intolerance
- 8 Stromal melting
- 9 Endothelial cell loss
- 10 Infectious keratitis
- 11 Endophthalmitis
- 12 Cataract
- 13 Traumatic rupture of keratotomy scars
- 14 Epithelial ingrowth
- 15 Irydociclitis
- 16 Retinal detachment and maculopathy
- 17 References
Corneal perforations can be divided into microperforations and macroperforations. Microperforations are usually in the inferior and temporal cornea, and they may allow continuing with surgery. The incidence of small ruptures in Descemet membrane is 2-10%, whereas of large perforations is 0-0.45%.
Factors that contribute to corneal perforations include inexperienced with the knife blade, centripetal incisions, intraocular pressure (IOP) elevation during incisions, recutting incisions, prolonged corneal dehydration intraoperatively, corneal thickness measurement erros, and unexpected movements of the patient.
When microperforations are detected, the surgeon should stop the incision, dry the knife and surface, and may be allowed to finish the incision with a slightly retracted knife blade or less pressure on it if the anterior chamber has a normal depth. Operating on a relatively dry field may permit to detect timely any leakage of aqueous humor. Starting the incisions in the thinnest quadrant first reduces the risk of a self-sealing perforation.
If a macroperforation occurs on the first incision or in the centrifugal component of any incision, the surgery must be stopped and completed later, with repeated pachymetry and diamond calibration.
The most important factor to prevent a large perforation is the timely recognition of a small perforation. Stopping the surgery because of aqueous leak prevents the extension of the laceration of Descemet membrane.
Self-sealing perforations are treated with cycloplegia (to dilate the pupil and prevent adherence of the iris to the perforation site), topical aqueous suppressants, topical antibiotics, and an ocular shield. Eye patching is not recommended as this compresses the cornea and opens the incisions.
In macroperforations, interrupted 10-0 nylon sutures are place to seal the wound and the eye should be patched if the anterior chamber is depth.
Complications of corneal perforation include damage to the endothelium with a subsequent scar in Descemet membrane, iridocorneal adhesions if there is a flat anterior chamber, laceration of the lens, endophthalmitis, or epithelial ingrowth.
Incisions and decentration
Incisions across the visual axis disturb vision by generating scarring, irregular astigmatism, and glare. Also, a small clear zone will cause a great effect if decentration occurs, with increased astigmatism and glare. Influencing factors include patient’s movements, an unexpected Bell reflex, inexperience with the knife and forceps, and a dry corneal surface. The combined (Genesis) incision technique was designed to minimize this. It consists in a centrifugal partial thickness cut followed by a centripetal cut to the optical zone with an especially-design diamond blade, which has a cutting surface on both sides.
Intersecting incisions can lead to corneal flaps, wound gape and poor healing. To approximate the wound edges, interrupted 10-0 nylon sutures are used. This are left for 10-12 weeks or until they loosen.
If a transverse incision to treat astigmatism is place in the wrong axis it can cause substantial refractive problems. Repeat operations can result in irregular astigmatism and hypertrophic scars, as well.
Other complications related to incisions include corneal posterior plaques if perforation occurs, limbal scarring and fibrovascular ingrowth if incisions extend beyond clear cornea, vascularization (especially in contact lens wearers), epithelial inclusions, debris and deposits.
Overcorrection is a significant complication of refractive surgery. There is better adaptation with undercorrection than with overcorrection. In overcorrection, a sudden demand for increased accommodation occurs, with associated accommodative-convergence of the near reflex.
Risk factors include radial incision prolonged to the limbus, multiple enhancement procedures, peripheral redeepening operations, absence of preoperative cycloplegic refraction, contact lens wear posoperatively, and postoperative ocular massage.
This can occur immediately after surgery when edema and the effect of the incisions cause gaping and greater flattening of the cornea. It usually resolves spontaneously within a few weeks, but can be reduced by decreasing the amount of irrigation at the end of surgery and by using hypertonic topical solutions in the postoperative period.
Incorrect incisions can also increase overcorrection. Another situation is the inexplicable overresponder in whom surgery was done properly but a large overcorrection followed. This is treated with spectacles, contact lenses, or suturing the wounds. In the case of suturing the wounds, the modified Grene Lasso suture approach has demonstrated suitable results.
Undercorrection is more frequent in high myopes, and can occur because of inaccuracy in refraction with insufficient surgery. Patients can remain undercorrected despite apparently accurate surgery, or can regress over time. Treatment includes medical and surgical methods.
Astigmatism can be residual (not corrected by surgery) or induced (increased after surgery). This may occur if fewer incisions are made, if the incisions are asymmetric in respect to the visual axis or have a variable deepness, or if the optical zone is decentered. Irregular astigmatism is more frequent with repeated surgeries. The majority of these refractive aberrations are self-limited and improve within the first 6 weeks. Refraction and corneal topography should be stable before placing additional incisions. This can be treated with rigid gas permeable contact lens.
Occurs in overcorrected patients, as they become presbyopic at an earlier age because of their hyperopia.
Contact lens intolerance
With shorter incisions (1 mm away from the limbus), the risk of corneal vascularization and fibrovascular ingrowth is reduced. Chronic contact lens wear is associated with irritation, hypoxia, wound stretching and progressive hyperopia.
Rigid gas-permeable lenses with peripheral curves matching the patient’s preoperative parameters are recommended in this situation.
Stromal melting frequently develops with crossed incisions. It is also associated with collagen vascular diseases, such as rheumatoid arthritis, and severe keratoconjunctivitis sicca. Thus, these patients are not candidates for radial keratotomy.
Endothelial cell loss
Acute endothelial cell loss has been reported, more severe with corneal perforation. Chronic increase in endothelial cell loss has the potential to cause an accelerated cell loss compare to the normal aging process. Corneal health after radial keratotomy is further confounded by contact lens wear. Radial keratotomy seems fairly safe if the number and length of incisions are minimized and macroperforations avoided.
Early postoperative keratitis
Most frequent organism includes Pseudomonas species, Staphylococcus aureus, and Staphylococcus epidermis. The infiltrate is usually located within an incision, and it may take place in the deep stroma with intact overlying epithelium. The use of prophylactic topical antibiotics until the incisions are reepithelialized reduces its frequency. Corneal Gram stains and cultures should be collected. A broad-spectrum fortified antibiotic must be initiated with adjustment depending on culture and sensitivity results. An initial approach may include fortified cefazolin (50 mg/ml), fortified tobramycin (14 mg/ml), and gataflaxicin on an hourly basis. A combination of 0.4 ml cefazolin (250 mg/ ml), 0.4 ml tobramycin (40 mg/ml), and 0.1 ml lidocaine 2% can be administered as a subconjunctival injection to the affected quadrant every day while cultures are awaited. Overlying epithelium can be debride in the first few days to improve antibiotic penetration. If no improvement, one must suspect the possibility of a fungus, atypical microorganism, or superinfection. Topical corticosteroids must be avoided.
Delayed bacterial or fungal keratitis is a rare complication, long-term prophylactic antibiotics are not recommended. Patients should be warned to consult an ophthalmologist if blurred vision or eye redness occurs. Chronic corticosteroid use may increase the risk of infectious keratitis. They can also be associated with cataracts, elevated intraocular pressure, or infectious crystalline keratopathy.
Herpes simplex keratitis
Surgical trauma can stimulate the recurrence of infection and decrease wound healing. Some authors consider herpes simplex keratitis a contraindication for refractive keratotomy. Other factors that may stimulate recurrent disease are sunlight, fever, contact lenses, menstruation, and trauma.
This is very rare. Probably the infectious agent comes from the eyelids, lashes, conjunctiva, or lacrimal system into the eye through a corneal perforation during or after surgery.
The majority of lens opacities after refractive keratotomy are the result of direct trauma to the lens through a corneal perforation. Recommendations to prevent this include precise corneal incisions and moderate use of topical corticosteroids after surgery.
Traumatic rupture of keratotomy scars
An increase risk of rupture from direct trauma exists, as the cornea becomes weaker after surgery. Patients must be advised about this.
Corneal epithelial ingrowth can occur through a perforation. Avoiding irrigation through a perforation may prevent this. Management depends on the extension.
A mild anterior chamber reaction usually occurs after surgery, which resolves in 1-3 weeks.
Retinal detachment and maculopathy
High myopia increases the risk of retinal detachment; therefore all patients should have a thorough fundus examination before surgery. Although cases of retinal detachment after refractive keratotomy have been reported, there is no evidence that surgery predisposes to retinal detachment.
- Kerry K. Assil, Joelle A. Hallak, Dimitri T. Azar . “Astigmatic and Radial Incisional Keratotomy”. In: Myron Yanoff, Jay S Duker. Ophthalmology. Fourth Edition. USA: MOSBY Elsevier, 2013: 141-146.
- Mounir Bashour. Radial Keratotomy Myopia Treatment & Management [online]. USA: Hampton Roy, march 2014. [Consult: 01/4/2016]. Available in: http://emedicine.medscape.com/article/1222168-treatment#d14
- John B Cason JB, Kerry Assil. “Radial keratotomy”. In: Copeland Jr RA, Afshari NA. Copeland and Afshari’s Principles and Practice of Cornea. Volume 1. First Edition. USA: Jaypee Brothers Medical Publishers, 2013: 1231-1237.
- Mahanti R, Shapiro D. Complications of small clear zone radial keratotomy. Ophthalmol 2000; 107(6): 1023-6.
- Walton N, Endriss D, Forseto AS. Corneal Suture for the Correction of Hyperopia Following Radial Keratotomy. J Refract Surg 2007; 23(5): 523-527.
- MacRae S, Rich L. Long-term Effects of Radial Keratotomy on the Corneal Endothelium. J Refract Surg 1998; 14(1): 49-52.
- Gwon A. Prospective Evaluation of Radial Keratotomy (PERK) Study 10 years after surgery. Arch Ophthalmol 1995; 113(10): 1225-6.
- Heidemann DG, Dunn SP, Chow CY. Early- versus late-onset infectious keratitis after radial and astigmatic keratotomy: clinical spectrum in a referral practice. J Cataract Refract Surg 1999; 25(12): 1615-9.