Repeated
Excimer Laser Treatment After Photorefractive Keratectomy Theo
\s=b\
in
Seiler, MD, PhD;
Scarring
or
Matthias
Derse; Thoai Pham,
undercorrection
occurs
percentage of patients after myopic photorefractive keratectomy. Scarring occurred in 1.8% of 298 patients with a baseline myopia of 6.0 diopters or less, increasing to 8.8% in those with cora
small
rections of more than 6.0 D. Undercorrection of more than 1 D occurred in 2.7% of the eyes with a baseline myopia of up to \m=-\6.0 D. A much greater incidence of undercorrection (30% to 40%) was found after corrections of more than 6.0 D. Thirty eyes in 30 patients were reoperated because of scarring (11 eyes) and/or undercorrection (27 eyes) and were observed for 6 to 18 months (average, 7.8 months). Only one of the eyes has shown mild scar formation after this second laser treatment. Sixty-three percent of these patients had a manifest refraction between \m=-\1.0D and +1.0 D six months after reop-
eration. Repeated phototablation seems to be a valuable technique for treatment of
scarring after photorefractive keratectomy. {Arch Ophthalmol. 1992;110:1230-1233) undercorrection and/or
keratectomy (PRK) "photorefractive with the excimer laser (193 nm) is *-
undergoing clinical investigation to prove its safety and efficacy. Previously published early studies revealed very promising results with success rates of 90% or greater for corrections of myo¬ up to —6.0 diopters after 1 year.'
pia
See also pp 1221 and 1286.
Scarring is considered to be one of the most serious complications, occurring in
1% of cases. Undercor¬ in approximately 8% of cases,1 less frequently than after radial keratotomy.2 In corrections of myopia
approximately
rection
occurs
Accepted for publication March 9, 1992. Universittsaugenklinik im Klinikum Charlottenburg, Berlin, Germany. Dr Seiler is a paid consultant for Summit Technology, Waltham, From the
Mass.
Reprint requests to the Universittsklinikum\x=req-\ Rudolf-Virchow, Augenklinik, Augustenburger Platz 1, W-1000 Berlin 65, Federal Republic of Germany (Dr Seiler).
MD
greater than -6.0 D, however, scarring and undercorrection may
Operation Technique
occur more
frequently.
To manage these complications, a second treatment may be necessary to remove scar tissue and/or to correct the residual refractive error. So far, such repeated ablations have been per¬ formed in animal eyes,3 in blind eyes (T.S., unpublished data, 1990), and for
therapeutic applications (W. Stark, MD, oral
communication, 1991). Herein, we report the outcome of re¬
peated excimer laser treatment with re¬ spect to scarring and undercorrection. PATIENTS AND METHODS
Thirty eyes in 30 patients were re¬ treated with a medical excimer laser (Summit Technology, Waltham, Mass) emitting 193-nm light at a fluence of 180 mJ/cm2 and a repetition rate of 10 Hz.
The same laser parameters were used for the initial PRK treatment. The mean (±SD) age of the patients was 34.4 ± 10.1 years (range, 21 to 56 years). Fourteen (47%) of the 30 eyes showed a pressure elevation of more than 5 mm Hg during the primary postoperative phase and were considered "steroid responders." All patients had originally undergone PRK in our clinic before October 31, 1990. The procedure was performed with the previously described nontouch technique4 with ablated zones 3.5 to 5 mm in diameter. At the follow-up exam¬ inations, the subepithelial haze was graded on a scale of 0 (clear cornea) to 4+ (dense scar).5 Haze of 2+ and greater interferes with vision; therefore, retreatment was considered in these pa¬ tients. Also, patients with a refractive error of more than —1.0 D, in whom the refraction remained constant for at least 3 months, were candidates for reoperation. The shortest time between the first and second treatments was 6 months. Informed consent was obtained from all patients after a thorough explanation of the procedure. The Ethics Committee of the Klinikum Charlottenburg, Berlin, Germany, approved the study protocol.
The photoablation technique involved two steps: removal of the epithelium and ablation
of stromal tissue. For débridement of the ep¬ ithelium, the beam diameter was set to 5 mm. The fellow eye was patched, and a lid speculum was inserted into the eye to be treated. The patient was positioned so that the heliumneon pilot beams merged on the anterior sur¬ face of the cornea at the correct image plane. The patients were asked to fixate the eye on the target that was coaxial with the beam, and the eye was oriented so that the pupil was cen¬ tered between the dimmed helium-neon spots on the iris. Laser energy was delivered by de¬ pressing the system foot pedal and could be in¬ terrupted any time. In a darkened operating room, the photoablation process was moni¬ tored by the observation of a fluorescent cir¬ cular area on the corneal surface seen through the surgical microscope. The fluorescence was bluish as long as epithelium was photoablated and disappeared when the excision reached the underlying stroma or scar tissue. The pho¬ toablation was discontinued as soon as the dark spots were confluent and formed a dark ring around a bluish area of remaining epithe¬ lium. A standard PRK procedure was then performed with a 5-mm optical zone size. The attempted correction was calculated with use of the manifest refractive error plus 1 D. On completion of the procedure, the patient was asked not to blink and was moved to the slit lamp. The ablated area was inspected for re¬ sidual scar tissue. In a few eyes, a minimal re¬ sidual scar was detected. In these cases, an¬ other 10 to 20 laser pulses (full beam, 5-mm zone) were delivered. The medication admin¬ istered before the laser treatment consisted of topical anesthetics and 1% pilocarpine hydro¬ chloride drops. After surgery, ofloxacin and 1% homatropine hydrobromide ointments were applied, and the eye was patched for one night. The patients were seen the next day, and the patch was removed. Until epithelium closure, the patients were asked to use oflox¬ acin ointment five times a day. Once reepithelialization occurred, 0.1% dexamethasone phosphate drops to be instilled five times a day were prescribed for the first month postoperatively. Fluorometholone (0.1%) was used four times a day during postoperative months 2 and 3 and was subsequently tapered during postoperative month 4. In cases of steroid re¬ sponse after the initial PRK treatment, the patients were asked to use Fluorometholone four times a day and ß-blockers twice a day, as soon as the epithelial defect was closed.
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Examinations
RESULTS
1 day, 2 days, and 1, 3, Patients 6, and 12 months after surgery. At each appointment after day 2, visual acuity, both unconnected and best corrected, was evaluated with use of a fogging technique. Keratometry (Ophthalmometer, Zeiss, Ob¬ erkochen, Germany), autorefraction (Model 570, Humphrey, San Leandro, Calif), autokeratometer readings (RK 1, Canon, Lake Success, NY), visual acuity under glare con¬ ditions (Model 570, Humphrey), intraocular pressure measurements (Goldmann), and slit-lamp inspections were performed at each visit. In addition, corneal topography was measured both preoperatively and postoperatively at each follow-up visit after day 2 after surgery.
The re-treatment group was divided into three subgroups: (1) repeated photoablation due to scarring no undercorrection; (2) re¬ peated photoablation due to scarring and undercorrection; and (3) treatment due to undercorrection, no scarring. The sizes of groups 1 and 2 are listed in Table 2. Groups 1 and 2 include all patients who met the inclusion criteria; however, not ev¬ ery patient with undercorrection without scarring needed a second treatment. In ad¬ dition to the 27 undercorrected eyes which were reoperated, in another nine undercor¬ rected eyes (after 1 year), the patients were satisfied with the result and decided not to undergo further treatment. Therefore, the incidence of undercorrection (12.1%) was clearly dependent on attempted correction: up to -6.0 D, six eyes or 2.7%; from -6.25 D to -10.0 D, 24 eyes or 36.9%; and more than -10.0 D, six eyes or 42.8%. The incidence of scarring with and without
were seen
Representative Group Two hundred ninety-eight sighted eyes in 201 patients treated with PRK through Oc¬ tober 31, 1990, served as a representative group to estimate the incidence of scarring and undercorrection. The preoperative re¬ fractions of the 298 eyes in this group are listed in Table 1.
Table
1—Attempted Corrections Representative Group
Refraction, Diopters
,
undercorrection is listed in Table 2. Clearly, scarring occurred significantly more fre¬ quently (P
Excimer Laser Treatment After Photorefractive Keratectomy Theo
\s=b\
in
Seiler, MD, PhD;
Scarring
or
Matthias
Derse; Thoai Pham,
undercorrection
occurs
percentage of patients after myopic photorefractive keratectomy. Scarring occurred in 1.8% of 298 patients with a baseline myopia of 6.0 diopters or less, increasing to 8.8% in those with cora
small
rections of more than 6.0 D. Undercorrection of more than 1 D occurred in 2.7% of the eyes with a baseline myopia of up to \m=-\6.0 D. A much greater incidence of undercorrection (30% to 40%) was found after corrections of more than 6.0 D. Thirty eyes in 30 patients were reoperated because of scarring (11 eyes) and/or undercorrection (27 eyes) and were observed for 6 to 18 months (average, 7.8 months). Only one of the eyes has shown mild scar formation after this second laser treatment. Sixty-three percent of these patients had a manifest refraction between \m=-\1.0D and +1.0 D six months after reop-
eration. Repeated phototablation seems to be a valuable technique for treatment of
scarring after photorefractive keratectomy. {Arch Ophthalmol. 1992;110:1230-1233) undercorrection and/or
keratectomy (PRK) "photorefractive with the excimer laser (193 nm) is *-
undergoing clinical investigation to prove its safety and efficacy. Previously published early studies revealed very promising results with success rates of 90% or greater for corrections of myo¬ up to —6.0 diopters after 1 year.'
pia
See also pp 1221 and 1286.
Scarring is considered to be one of the most serious complications, occurring in
1% of cases. Undercor¬ in approximately 8% of cases,1 less frequently than after radial keratotomy.2 In corrections of myopia
approximately
rection
occurs
Accepted for publication March 9, 1992. Universittsaugenklinik im Klinikum Charlottenburg, Berlin, Germany. Dr Seiler is a paid consultant for Summit Technology, Waltham, From the
Mass.
Reprint requests to the Universittsklinikum\x=req-\ Rudolf-Virchow, Augenklinik, Augustenburger Platz 1, W-1000 Berlin 65, Federal Republic of Germany (Dr Seiler).
MD
greater than -6.0 D, however, scarring and undercorrection may
Operation Technique
occur more
frequently.
To manage these complications, a second treatment may be necessary to remove scar tissue and/or to correct the residual refractive error. So far, such repeated ablations have been per¬ formed in animal eyes,3 in blind eyes (T.S., unpublished data, 1990), and for
therapeutic applications (W. Stark, MD, oral
communication, 1991). Herein, we report the outcome of re¬
peated excimer laser treatment with re¬ spect to scarring and undercorrection. PATIENTS AND METHODS
Thirty eyes in 30 patients were re¬ treated with a medical excimer laser (Summit Technology, Waltham, Mass) emitting 193-nm light at a fluence of 180 mJ/cm2 and a repetition rate of 10 Hz.
The same laser parameters were used for the initial PRK treatment. The mean (±SD) age of the patients was 34.4 ± 10.1 years (range, 21 to 56 years). Fourteen (47%) of the 30 eyes showed a pressure elevation of more than 5 mm Hg during the primary postoperative phase and were considered "steroid responders." All patients had originally undergone PRK in our clinic before October 31, 1990. The procedure was performed with the previously described nontouch technique4 with ablated zones 3.5 to 5 mm in diameter. At the follow-up exam¬ inations, the subepithelial haze was graded on a scale of 0 (clear cornea) to 4+ (dense scar).5 Haze of 2+ and greater interferes with vision; therefore, retreatment was considered in these pa¬ tients. Also, patients with a refractive error of more than —1.0 D, in whom the refraction remained constant for at least 3 months, were candidates for reoperation. The shortest time between the first and second treatments was 6 months. Informed consent was obtained from all patients after a thorough explanation of the procedure. The Ethics Committee of the Klinikum Charlottenburg, Berlin, Germany, approved the study protocol.
The photoablation technique involved two steps: removal of the epithelium and ablation
of stromal tissue. For débridement of the ep¬ ithelium, the beam diameter was set to 5 mm. The fellow eye was patched, and a lid speculum was inserted into the eye to be treated. The patient was positioned so that the heliumneon pilot beams merged on the anterior sur¬ face of the cornea at the correct image plane. The patients were asked to fixate the eye on the target that was coaxial with the beam, and the eye was oriented so that the pupil was cen¬ tered between the dimmed helium-neon spots on the iris. Laser energy was delivered by de¬ pressing the system foot pedal and could be in¬ terrupted any time. In a darkened operating room, the photoablation process was moni¬ tored by the observation of a fluorescent cir¬ cular area on the corneal surface seen through the surgical microscope. The fluorescence was bluish as long as epithelium was photoablated and disappeared when the excision reached the underlying stroma or scar tissue. The pho¬ toablation was discontinued as soon as the dark spots were confluent and formed a dark ring around a bluish area of remaining epithe¬ lium. A standard PRK procedure was then performed with a 5-mm optical zone size. The attempted correction was calculated with use of the manifest refractive error plus 1 D. On completion of the procedure, the patient was asked not to blink and was moved to the slit lamp. The ablated area was inspected for re¬ sidual scar tissue. In a few eyes, a minimal re¬ sidual scar was detected. In these cases, an¬ other 10 to 20 laser pulses (full beam, 5-mm zone) were delivered. The medication admin¬ istered before the laser treatment consisted of topical anesthetics and 1% pilocarpine hydro¬ chloride drops. After surgery, ofloxacin and 1% homatropine hydrobromide ointments were applied, and the eye was patched for one night. The patients were seen the next day, and the patch was removed. Until epithelium closure, the patients were asked to use oflox¬ acin ointment five times a day. Once reepithelialization occurred, 0.1% dexamethasone phosphate drops to be instilled five times a day were prescribed for the first month postoperatively. Fluorometholone (0.1%) was used four times a day during postoperative months 2 and 3 and was subsequently tapered during postoperative month 4. In cases of steroid re¬ sponse after the initial PRK treatment, the patients were asked to use Fluorometholone four times a day and ß-blockers twice a day, as soon as the epithelial defect was closed.
Downloaded From: http://archopht.jamanetwork.com/ by a DALHOUSIE UNIVERSITY-DAL-11762 User on 06/20/2015
Examinations
RESULTS
1 day, 2 days, and 1, 3, Patients 6, and 12 months after surgery. At each appointment after day 2, visual acuity, both unconnected and best corrected, was evaluated with use of a fogging technique. Keratometry (Ophthalmometer, Zeiss, Ob¬ erkochen, Germany), autorefraction (Model 570, Humphrey, San Leandro, Calif), autokeratometer readings (RK 1, Canon, Lake Success, NY), visual acuity under glare con¬ ditions (Model 570, Humphrey), intraocular pressure measurements (Goldmann), and slit-lamp inspections were performed at each visit. In addition, corneal topography was measured both preoperatively and postoperatively at each follow-up visit after day 2 after surgery.
The re-treatment group was divided into three subgroups: (1) repeated photoablation due to scarring no undercorrection; (2) re¬ peated photoablation due to scarring and undercorrection; and (3) treatment due to undercorrection, no scarring. The sizes of groups 1 and 2 are listed in Table 2. Groups 1 and 2 include all patients who met the inclusion criteria; however, not ev¬ ery patient with undercorrection without scarring needed a second treatment. In ad¬ dition to the 27 undercorrected eyes which were reoperated, in another nine undercor¬ rected eyes (after 1 year), the patients were satisfied with the result and decided not to undergo further treatment. Therefore, the incidence of undercorrection (12.1%) was clearly dependent on attempted correction: up to -6.0 D, six eyes or 2.7%; from -6.25 D to -10.0 D, 24 eyes or 36.9%; and more than -10.0 D, six eyes or 42.8%. The incidence of scarring with and without
were seen
Representative Group Two hundred ninety-eight sighted eyes in 201 patients treated with PRK through Oc¬ tober 31, 1990, served as a representative group to estimate the incidence of scarring and undercorrection. The preoperative re¬ fractions of the 298 eyes in this group are listed in Table 1.
Table
1—Attempted Corrections Representative Group
Refraction, Diopters
,
undercorrection is listed in Table 2. Clearly, scarring occurred significantly more fre¬ quently (P
