|
Speciality Spotlight
Refractive Surgery
-
Budak K, Hamed AM, Friedman NJ, et al (Baylor College of Medicine, Houston)
Preoperative Screening of Contact Lens Wearers Before Refractive Surgery.
J Cataract Refract Surg 25: 1080-1086,1 999.
Patients must discontinue contact lens wear prior to refractive surgery, so that the cornea can recover its normal contour.
Computerised videokeratography (CVK) provides a sensitive assessment of changes over a large area of the corneal surface.
Corneal stability after discontinuation of contact lens wear was investigated using CVK, in 76 contact lens wearers (CLWs) who were candidates for refractive surgery.
Soft contact lens wear was discontinued for 2 weeks and gas-permeable for 5 weeks.
Sequential examination of corneal topography in CLWs are crucial to ensure that contact lens related corneal changes have resolved prior to refractive surgery.
-
Waring GO III, Carr JD, Stulting RD, et al (Emory Univ, Atlanta, Ga)
Prospective Randomized Comparison of Simultaneous and Sequential Bilateral Laser in Situ Keratomileusis for the Correction of Myopia
Ophthalmology 106: 732-738, 1999
This randomized trial (378 eyes in the simultaneous group and 331 eyes in the sequential group) showed few differences in safety or efficacy for eyes in which bilateral LASIK was performed (simultaneously or sequentially). The only safety difference was a small increase in the risk for epithelial in-growth during simultaneous procedures.
-
Donnenfeld ED, Kornstein HS, Amin A, et al (North Shore Univ Hosp, Manhasset, NY; New York Univ)
Laser In Situ Keratomileusis for Correction of Myopia and Astigmatism After Penetrating Keratoplasty
Ophthalmology 106: 1966-1975, 1999
Results of LASIK in patients with postkeratoplsty myopia and astigmatism were evaluated. The prospective uncontrolled trial included 23 eyes of 22 patients with myopia, astigmatism or both after Penetrating Keratoplasty (PK).
It was found that results were better in terms of correcting myopia than astigmatism.
To minimize the risk of complications, postkeratoplasty LASIK should be done by an experienced surgeon in order to minimize suction time.
-
Buzard KA, Tuengler A, Febbraro J-L (Univ of Nevada, Las Vegas; Buzard Eye Inst, Las Vegas, Nevada; Tulane Univ, New Orleans, La)
Treatment of Mild to Moderate Keratoconus with Laser in Situ Keratomileusis.
J Cataract Refract Surg 25: 1600-1609, 1999
In patients with mild-to-moderate keratoconus, LASIK gives encouraging results. Long term follow-up showed that some eyes develop reduction in visual acuity, as also corneal ectasia with astigmatism. Nearly one-fifth eyes required penetrating keratoplasty one to two years after LASIK.
-
Perez-Santonja JJ, Sakla HF, Cardona C, et al (Univ of Alicante, Spain)
Corneal Sensitivity After Photorefractive Keratectomy and Laser in Situ Keratomileusis for Low Myopia.
Am J Ophthalmol 127: 497-504, 1999.
In patients undergoing LASIK correction for low myopia, corneal sensitivity remains significantly reduced during the first 3 post-operative months. However, corneal sensitivity recovers within one month after Photorefractive Keratectomy (PRK).
Lasik appears to cause more damage to the corneal innervation than PRK does.
-
Stulting RD, Carr JD, Thompson KP, et al (Emory Univ, Atlanta, Ga)
Complications of Laser in Situ Keratomileusis for the Correction of Myopia
Ophthalmology 106: 13-20, 1999
In this large study of 1062 eyes, complications occurred in 5% of procedures, but rarely caused loss of more than 2 Snellens lines. Flap button holes were the largest cause of loss of visual acuity. Surgery expertise reduces the rate of complications.
-
Quiros PA, Chuck RS, Smith RE, et al (Univ of California, Irvine)
Infectious Ulcerative Keratitis After Laser In Situ Keratomileusis
Arch Ophthalmol 117: 1423-1427, 1999
The authors report 6 cases of LASIK-associated infectious ulcerative keratitis.
Symptoms developed as long as one year after the procedure, although more often they occurred within the first few days.
Residual stromal scarring developed after ulceration in all 6 eyes. A causative organism was cultured in 4 of 5 eyes. Three eyes required secondary interventions: flap excision in two eyes and penetrating keratoplasty in one eye.
Possible risk factors for ulcerative keratitis were :
(1) soft contact lens wear in 2 patients – one of whom was using corticosteroids.
(2) Undiagnosed dry eye in 2 patients
(3) Severe blepharitis in a patient who was HIV positive.
-
AS Forseto, CM Francesconi, RAM Nose , et al [Eye Clinic Day Hosp, Sao Paulo, Brazil]
Laser in Situ Keratomileusis to Correct Refractive Errors After Keratoplasty
J Cataract Refract Surg 25: 479-485, 1999
The result of LASIK in 22 eyes of 19 patients [with a history of keratoplasty] were reported. Ninety-one percent of eyes had had keratoconus before keratoplasty was done. Penetrating keratoplasty [PK] was done in 82% of eyes, and lamellar in 18%.
LASIK was performed a mean of 5 years after keratoplasty. The authors found that 55% patients achieved uncorrected visual acuity of at least 20/40. There were no serious complications such as significant endothelial cell loss or keratoplasty wound dehiscence.
The authors however state that long-term follow-up is required to firmly establish the efficacy of this procedure.
-
HS Geggel, AR Talley [ Virginia Mason Med Ctr, Seattle, Wash; TLC-North-West Eye, Seattle, Wash]
Delayed Onset Keratectasia Following Laser in Situ Keratomileusis
J Cataract Refract Surg 25: 582-586, 1999
Removal of too much stromal tissue, during LASIK, can lead to iatrogenic keratectasia. The authors report a case of a woman [44 years old].
There was progressive steepening of the central cornea, necessitating a penetrating keratoplasty in the right eye, about 9 months following the LASIK procedure.
Further study is needed to define the amount of posterior stroma to be left intact.
-
HY Yang, H Fuji Shima, I Toda et al ( Tokyo Dental College; Keio Univ, Tokyo; Itoh Hosp, Mobara, Japan)
Allergic Conjunctivitis as a Risk Factor for Regression and Haze After Photorefractive keratectomy.
Am J Ophthalmol 125: 54-58, 1998.
Allergic conjunctivitis may be associated with subepithelial haze in patients who undergo PRK. The relationship between allergic conjunctivitis and the results of PRK with a 4.5-mm ablation zone were examined in 57 eyes.
Results indicate that untreated allergic conjunctivitis is associated with the development of corneal haze and myopic regression after photorefractive keratectomy (PRK). When allergic conjunctivitis was treated, these adverse effects were significantly decreased.
-
MC Knorz, B Wiesinger, A Liermann, et al (Klinikum Mannheim, Germany)
Laser In Situ Keratomileusis for Moderate and High Myopia and Myopic Astigmatism.
Ophthalmology 105: 932-940, 1998.
Patients with greater than -6 D of myopia undergoing wide-area ablation photorefractive keratectomy run the risk of refractive instability, corneal scarring night aberration and loss of visual acuity.
The predictability, stability, and safety of a standardised LASIK technique were examined in 93 eyes with myopia and myopic astigmatism. In patients with myopia of upto -10 D, the standardized LASIK procedure offers stable manifest refraction, adequate uncorrected visual acuity, and good patient satisfaction. Patient satisfaction is lower with astigmatism correction than with spherical correction.
-
M Pop (Michel Pop Clinics, Montreal and Hull, PQ):
Laser Thermal Keratoplasty for the Treatment of Photorefractive Keratectomy Overcorrections: A1-Year follow-up.
Ophthalmology 105:926-931, 1998.
The use of holmium: yttrium-aluminium-garnet (YAG) laser thermal keratoplasty (LTK) when re-treating PRK-overcorrected myopic eyes was evaluated with patients who were overcorrected by at least 1 D.
Two thirds of the retreated eyes needed no further retreatment at 12 months after a LTK following initial PRK.
-
WA Lyle, GJC Jin (Eye Inst of Utah, Salt Lake City)
Hyperopic Automated Lamellar Keratoplasty: Complications and Visual Results.
Arch Ophthalmol 116:425-428, 1998.
The use of hyperopic automatted lamellar keratoplasty should be discouraged because of its long-term instability and high incidence of iatrogenic keratoconus especially true for consecutive hyeropia after radial keratotomy.
-
RJ Smith, RK Maloney (Jules Stein Eye Inst, Los Angeles; Univ of California, Los Angeles)
Diffuse Lamellar Keratitis: A New Syndrome in Lamellar Refractive Surgery.
Ophthalmology 105: 1721-1726, 1998.
After lamellar refractive surgery, infectious keratitis can occur, which can be confused with the self-limiting syndrome, diffuse lamellar keratitis.
Noninfectious diffuse lamellar keratitis (also called – Sands of the Sahara syndrome) is a syndrome of unknown origin following lamellar refractive surgery. The condition begins 2 to 6 days after surgery and resolves within 2 weeks – it may be associated with pain or photophobia. The treatment of choice is an increase in topical steroids and close follow-up.
-
WB Jackson, E Casson, WG Hodge, et al (Univ of Ottawa, Ont; Ottawa Gen Hosp, Ont)
Laser Vision Correction for Low Hyperopia : An 18-month Assessment of Safety and Efficacy.
Ophthalmology 105:1727-1738, 1998.
Hyperopic PRK is safe and effective. Recovery of best spectacle -corrected vision and of uncorrected visual acuity is slower than with myopic procedure. Some regression of spherical equivalent appeared between 12 to 18 months
-
HV Gimbel, EEA Penno, JA van Westenbrugge, et al (Gimbel Eye Centre, Calgary, Alta)
Incidence and Management of Intraoperative and Early Postoperative Complications in 1000 consecutive Laser In Situ Keratomileusis Cases.
Ophthalmology 105: 1839-1848, 1998.
There were 32 intraoperative complications (3.2%), 19 related to the microkeratone and 13 related to the surgery. In the latter 13 cases, surgery was discontinued – 9 of these patients successfully underwent the procedure at a later date.
Flaps had to be repositioned in 18 eyes, 24 hours or less after surgery because the flaps shifted or microwrinkles or edge folds developed. The incidence of intraoperative microkeratome complications decreased substantially as the surgeon gained experience.
Of the 950 eyes with uncomplicated LASIK surgery, 290(30.5%), needed to be retreated, mainly for undercorrection (79.3%) or overcorrection (9.7%). Of the 32 eyes that experienced complications, after 6 months, 26 eyes remained the same or improved slightly (one line), 6 eyes lost one line.
Of the uncomplicated cases, 16(1.77%) lost 2 lines or more.
-
MS Kapadia, SE Wilson (Cleveland Clinic Found, Ohio)
Transepithelial Photorefractive Keratectomy for Treatment of thin flaps or caps after complicated Laser in Situ Keratomileusis (LASIK).
Am J Ophthalmol 126: 827-829, 1998.
Transepithelial PRK seems to be effective in the treatment of central corneal thin cap or flap abnormalities associated with LASIK, especially in eyes with associated central corneal scarring or with epithelial ingrowth that causes doubling or ghosting of the image, or loss of best corrected visual acuity.
-
PG Ursell, DJ Spalton, MV Pande, et al (St Thomas’ Hosp, London; Kings College, London; United Med and Dental Schools, London)
Relationship Between Intraocular Lens Biomaterials and Posterior Capsule Opacification.
J Cataract Refract Surg 24: 352-360, 1998.
A system for objectively measuring the degree of posterior capsular opacification (PCO) in an individual eye was developed, using high-resolution digital imaging and dedicated image processing software. This system was used to follow the development of PCO in a prospective, randomized study of 99 patients with a PMMA, silicone or AcrySof IOL.
Patients with surgical complications were excluded from the final analysis. A digital retroillumination camera with a dedicated software program was used to assess posterior capsule opacification.
Compared with PMMA and silicone lenses, the AcrySof lenses were associated with less PCO. No significant differences occurred between PMMA and silicone lenses.
-
MJF Orhdahl, PP Fagerholm (St Erik Eye Hosp, Stockholm; Karolinska Inst, Stockholm)
Phototherapeutic Keratectomy for Map-Dot-Fingerprint Corneal Dystrophy.
Cornea 17:595-599, 1998.
Map-dot-fingerprint (MDF) dystrophy is the commonest corneal dystrophy causing transient or permanent reduction in visual acuity, sometimes combined with ghost images or subjective monocular diplopia. The latter symptoms result from irregular astigmatism and abnormal tear break-up.
Excimer laser photoablation appears to be effective, safe and stable in eyes with MDF dystrophy.
-
C K Patel, R Hanson et al (Oxford Eye Hospital, Radcliffe Infirmary)
Late Dislocation of a LASIK Flap Caused by a Fingernail
Arch Ophthalmol, vol.119, March 2001, pg.447-450
This is a case report of a 28 yr.old white lady who underwent uncomplicated bilateral LASIK. Ten months following surgery, her fingernail brushed the left eye while she was removing a sweater. This resulted in painful displacement of the corneal cap.
After repositioning the cap (under topical and sub-Tenon anaesthesia) it was found that the cap had everted, the lower edge of the nasal hinge had torn, it had twisted about the original hinge and one of its edges had folded over.
The stromal bed and cap were debrided and Three 10-0 nylon sutures were used to secure the cap. Five days later debris was detected between the cap and corneal stroma, suggestive of epithelial in growth.
Forty-three days postoperatively, irregular astigmatism reduced unaided visual acuity to 20/200. This later recovered to 20/40 following removal of a small central area of corneal stroma, scraping of the residual cap area and application of a bandage lens. The patient is being managed conservatively. The authors make the following interesting comments:
Recent reviews of Lasik state that cap dislocation occurs in 0.7% to 5.8% cases.
Debridement of edematous corneal epithelium during vitrectomy has resulted in iatrogenic cap dislocation.
Corneal integrity is never fully restored after creation of a LASIK flap. Flap dislocation as a potential delayed complication should be discussed as part of informed consent prior to surgery.
Lasik should be contraindicated in patients with a high risk of sustaining glancing corneal injuries, as in rugby players.
-
Majmudar PA, Forstot SL, Dennis RF, et al (Rush-Presbyterian-St Luke’s Med Ctr, Chicago; Corneal Consultants of Colorado, Littleton; Eye Consultants of Maryland, Baltimore; et al)
Topical Mitomycin-C for Subepithelial Fibrosis After Refractive Corneal Surgery
Ophthalmology 107: 89-94, 2000
Subepithelial fibrosis following refractive corneal surgery can be visually disabling. The authors found that the use of topical Mitomycin C, 0.2%, seems to be an efficient way to prevent recurrence of subepithelial fibrosis after debridement.
-
Wachtlin J, Blasig IE, Schrunder S, et al (Free Univ, Berlin; Forschungsverbund Berlin EV; Univ Med Ctr Benjamin Franklin, Berlin)
PRK and LASIK- Their Potential Risk of Cataractogenesis: Lipid Peroxidation Changes in the Aqueous Humor and Crystalline Lens of Rabbits
Cornea 19: 75-79, 2000
LASIK with a flap thickness of 250 mm was performed (right eye) of 6 female rabbits. A 250 mm thick corneal flap was then created by a microkeratome cut on the left eye. The corneal lenticules were then sutured with 10-0 nylon interrupted sutures, which were removed after 7 days.
PRK was done in the right eye of 6 other rabbits, and the left eye was left untreated.
The results suggest that LASIK, but not PRK, may be a risk factor in cataractogenesis, on the basis of findings of elevated malondialdehyde (MDA) levels in the lens of the microkeratome group.
The increase in MDA levels in this group probably result from the microkeratome incision rather than secondary radiation from the excimer laser.
-
Wang MY, Maloney RK (Univ of California, Los Angeles; Maloney Vision Inst, Los Angeles)
Epithelial Ingrowth After Laser In Situ Keratomileusis
Am J Ophthalmol 129: 746-751, 2000
The rate of significant epithelial ingrowth after primary treatment was 35 (0.92%) of 3786 eyes. After enhancement LASIK, the rate of significant epithelial ingrowth was 8 (1.7%) of 480 eyes.
The authors postulate a hypothesis that epithelial ingrowth is caused by postoperative invasion under the flap by surface epithelial cells, rather than intraoperative implantation of epithelial cells.
Complete mechanical removal of epithelium from the posterior surface of the corneal flap and keratectomy bed sufficient to ensure tight apposition of the flap with the bed is recommended.
-
Dastgheib KA, Clinch TE, Manche EE, et al (Univ of Utah, Salt Lake City; Stanford Univ, Palo Alto, Calif; Univ of Medicine and Dentistry New Jersey, Newark)
Sloughing of Corneal Epithelium and Wound Healing Complications Associated With Laser In Situ Keratomileusis in Patients With Epithelial Basement Membrane Dystrophy
Am J Ophthalmol 130: 297-303, 2000
The authors postulate that patients with epithelial basement membrane dystrophy may be at increased risk of sloughing of the corneal epithelium during the microkeratome pass of LASIK procedures. Flap distortion, flap keratolysis, interface epithelial growth, and corneal scarring may result. Hence, LASIK is not recommended for these patients.
The clinical signs of epithelial basement membrane dystrophy in asymptomatic eyes may be lacking, therefore it is possible to miss the diagnosis even with meticulous examination.
-
Holland SP, Mathias RG, Morck DW, et al (Univ of British Columbia, Vancouver; TCL The Laser Ctr, Vancouver; Univ of Calgary, Alberta; et al)
Diffuse Lamellar Keratitis Related to Endotoxins Released From Sterilizer Reservoir Biofilms
Ophthalmology 107: 1227-1234, 2000
One of the complications of LASIK is diffuse lamellar keratitis (DLK) – which involves the development of a lamellar, diffuse infiltrate in the interface. This infiltrate progressively increases in size and density. It occurs within one week of surgery.
The incidence and the cause of DLK remain undetermined. It was hypothesized that DLK is a response to a heat-stable toxin introduced under the corneal flap which produced a polymorphonuclear reaction in susceptible individuals.
The microorganism isolated from the sterilization reservoir was Burkholderia pickettii. The toxin of this microorganism was able to survive the short-cycle sterilization used, was deposited on the instruments and then was introduced into the flap interface.
The endotoxin (lipopolysaccharide) producing the DLK was derived from gram-negative bacteria.
-
Lee AG, Kohnen T, Ebner R, et al (Univ of Iowa, Iowa City; Baylor College of Medicine, Houston; Johann Wolfgang Goethe-Univ, Frankfurt, Germany; et al)
Optic Neuropathy Associated With Laser In Situ Keratomileusis
J Cataract Refract Surg 26: 1581-1584, 2000
Intraocular pressure (IOP) may rise significantly during the lamellar cut portion of LASIK. The authors report 4 cases of optic neuropathy after LASIK.
During the lamellar cut portion of LASIK, a suction device is applied to stabilize the globe and increase IOP to achieve a smooth cut.
In the vacuum phase, IOP can increase to 80 to 230 mm Hg with a microkeratome. During the lamellar cut IOP can reach 140 to 360 mm Hg.
In the above 4 cases, 2 developed retrobulbar optic neuropathy while 2 developed anterior ischemic optic neuropathy.
The resulting visual acuity and field loss were permanent.
-
Colin J, Cochener B, Savary G, et al (Brest Univ, France)
Correcting Keratoconus With Intracorneal Rings
J Cataract Refract Surg 26: 1117-1122, 2000
The use of intra stromal corneal rings (Intacs) may delay and avoid the need for penetrating keratoplasty (PKP) in patients with contact lens (CL) intolerance who have clear cornea keratoconus.
Intacs can change the corneal shape in patients with low myopia by effectively flattening the central cornea.
The intacs do not eliminate the keratoconus, but decrease the corneal abnormality to achieve acceptable visual acuity, thereby delaying or eliminating the need for PKP.
