Anupam Chatterjee

REDUCTION IN INTRAOCULAR PRESSURE AFTER EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY; CORRELATION WITH PRETREATMENT MYOPIA

PURPOSE The authors relate the observed reduction in intraocular pressure (IOP) after excimer laser treatment to the degree of myopia treated. BACKGROUND Intraocular pressure, measured by both Goldmann applanation and noncontact tonometry, has been reported to decrease after excimer laser photorefractive keratectomy (PRK). However, IOP readings after excimer laser PRK might be inaccurate as a consequence of changes in both the thickness and curvature of the cornea. METHODS Baseline IOP readings were measured by noncontact tonometry in each eye of a group of 1320 patients at the time of their initial consultation. These were compared to readings obtained before treatment of the second eye, which took place a minimum of 4 months later. The untreated eyes served as controls. The paired Students t test was used for statistical analysis. RESULTS After PRK, a decrease was observed in the IOP of treated eyes that was related to the degree of myopia treated. A significant difference was observed between treated and untreated eyes (P < 0.0000). CONCLUSIONS The IOP measured after PRK for myopia may be reduced because of changes in corneal thickness (absence of Bowmans membrane and central thinning) and topography. This is of particular relevance when monitoring the IOP of those patients who are given steroid drops to prevent regression. It also may be of importance in the management of any future glaucoma.

Predictability of spherical photorefractive keratectomy for myopia1

Abstract Objective This study aimed to examine the effects of purely spherical excimer laser photorefractive keratectomy (PRK) for myopia. Design Consecutive case series. Participants A total of 3218 eyes with a mean preoperative mean spherical equivalent (MSE) of −3.75 diopters (D) ± 1.73 D standard deviation (SD) (range, −1.00 D to −11.88 D) underwent PRK with a Nidek EC-5000 excimer laser. Eyes were divided into groups based on the degree of preoperative myopia in 1 D steps Intervention All eyes underwent PRK with a Nidek EC-5000 excimer laser. Main outcome measure Visual and refractive outcome of PRK treatment was measured. Results After a mean follow-up period of 52.6 weeks (range, 26–150 weeks), the final MSE was −0.07 D (±0.68 D) (range, −5.50 D to +4.50 D). Of the 3218 eyes, 2919 (90.7%) were within 1.00 D of emmetropia, and 3038 (94.4%) of eyes had an uncorrected visual acuity of 20/40 or better, with 1886 (58.6%) achieving 20/20 or better visual acuity. Eyes in the lower preoperative myopia groups had a greater chance of attaining 20/40 unaided visual acuity than those in the higher groups (e.g., 98.3% of the −2D group and 53.6% of the −9D group achieved 20/40 unaided visual acuity). Overall, mean postoperative haze was 0.29 ± 0.39 SD (scale, 0–3), and 29 eyes (0.9%) lost 0.3 or more logarithm of the minimum angle of resolution (LogMAR) unit of best-corrected visual acuity. Conclusions Excimer laser PRK is an effective treatment for myopia of up to −9.00 D. The outcome parameters are less predictable for eyes with greater than −9.00 D of myopia.

COMPARISON OF 18% ETHANOL AND MECHANICAL DEBRIDEMENT FOR EPITHELIAL REMOVAL BEFORE PHOTOREFRACTIVE KERATECTOMY

PURPOSE To assess the safety of alcohol compared to mechanical debridement for epithelial removal prior to photorefractive keratectomy (PRK). METHODS Forty-one second eyes of 41 patients underwent epithelial removal using alcohol prior to PRK with a Nidek EC-5000 excimer laser. The results were compared with the results of the 41 first eyes of the same patients that had mechanical debridement. RESULTS Initial results showed that the alcohol treated group tended to stay slightly hyperopic but had less haze compared to the mechanical debridement group. The treating surgeons favored alcohol as the preferred method of epithelium removal. CONCLUSION Alcohol debridement is an effective procedure although algorithms may have to be altered to take into account the slightly different healing process postoperatively.

Results of Excimer Laser Retreatment of Residual Myopia after Previous Photorefractive Keratectomy

BACKGROUND Nine percent to 30% of all patients who undergo a single excimer laser photorefractive keratectomy (PRK) do not achieve an unaided visual acuity of 20/ 40 or better and may require optical correction to obtain adequate vision. METHODS The authors performed a retrospective analysis of the records of 164 patients who had undergone retreatment with the excimer laser for residual myopia after a previous PRK. Mean follow-up was 35.5 +/- 15.2 weeks (range, 26-104 weeks). RESULTS The mean spherical equivalent (MSE) before retreatment was -2.59 +/- 1.36 diopter (D) (range, -0.50 to -7.75 D). The final MSE after reablation was -0.52 +/- 1.36 D (range, 2.50 to -5.50). Of the 164 patients, 107 (65.2%) obtained a final refraction within 1.00 D of emmetropia and 111 (67.3%) achieved an unaided visual acuity of 20/40 or better. Only 10 patients (6.1%) lost more than one Snellen line of best-corrected visual acuity. The final MSE result for the subgroup of patients who had a pre-retreatment myopia of between -0.50 and -1.90 D (-0.31 +/- 1.09 D) was significantly closer to emmetropia than that of the subgroup with a residual myopia of -4.00 to -7.75 D (-1.62 +/- 1.94 D). CONCLUSIONS Excimer laser retreatment may provide a relatively safe and predictable method of correcting residual myopia after an earlier PRK with a 25% extra correction recommended for residual myopia.

Astigmatism Induced by Spherical Photorefractive Keratectomy Corrections

PURPOSE The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and the Nidek EC-5000 (Nidek Co. Ltd, Aichi, Japan) excimer lasers. METHODS A total of 4269 eyes of 3289 patients were treated with a 5-mm optical zone using the Summit Omnimed excimer laser and 1825 eyes of 1303 patients treated with the Nidek EC-5000 excimer laser. The final astigmatic refractive outcome was compared with the initial refraction by vector analysis (Alpin and Jaffe method). RESULTS Subjective astigmatic refraction for the Summit laser reduced from a mean of -0.39 diopter (D) +/- standard deviation (SD) 0.33 D (range, 0 to -2.50 D) to -0.33 D +/- SD 0.41 D (range, 0 to -3.00 D). Surgically induced astigmatism (SIA) had a mean of 0.42 +/- SD 0.34 D (range, 0 to 2.89 D). Mean SIA increased with increasing preoperative astigmatism by 0.60 D SIA for every 1.00 D of preoperative cylinder. For the Nidek laser, subjective astigmatic refraction changed from a mean of -0.18 D +/- SD 0.21 D (range, 0 to -1.25 D) to -0.30 D +/- SD 0.33 D (range, 0 to -3.00 D). Surgically induced astigmatism had a mean of -0.32 D +/- SD 0.29 (range, 0 to 3.05 D). Mean SIA increased with increasing preoperative astigmatism by 0.47 D SIA for every 1.00 D of preoperative cylinder. CONCLUSIONS The authors show that spherical photorefractive keratectomy corrections can induce significant astigmatic change, particularly if a large amount of preoperative astigmatism is present.

Predictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser.

Purpose: To evaluate the effect of astigmatic correction on the accuracy of the myopic and astigmatic correction in patients having photorefractive astigmatic keratectomy (PARK) and in those having photorefractive keratectomy (PRK). Setting: Specialist excimer laser refractive clinic. Methods: This prospective consecutive case series comprised 6097 eyes with a preoperative mean spherical equivalent (MSE) of –4.63 diopters (D) ± 1.95 (SD) (range –0.75 to –13.00 D) and a mean cylinder of –1.13 ± 0.73 D (range –0.50 to –6.00 D) having PARK with a Nidek EC‐5000 excimer laser. Visual and refractive outcomes were assessed 12 months postoperatively and compared with those in 3004 eyes that had spherical PRK. Results: At 12 months, the MSE was –0.02 ± 0.79 D and the mean cylinder was –0.49 ± 0.47 D in the PARK group; the MSE was −0.07 ± 0.66 D in the PRK group. An MSE within ±0.05 D of emmetropia was achieved by 69.8% and within ±1.00 D, by 87.9%. The uncorrected visual acuity (UCVA) was 20/20 or better in 42.6% and 20/40 or better in 91.2%. Statistical significance (P < .001, analysis of variance) was achieved for MSE, sphere, cylinder, haze, and visual acuity (best corrected [BCVA] and UCVA) based on the preoperative cylinder. The loss of BCVA varied from 1.1% to 5.8% depending on the degree of astigmatism treated. Accuracy varied with the attempted myopic correction and the attempted astigmatic correction. Conclusions: Excimer laser PARK was an effective treatment for compound myopic astigmatism, but predictability decreased and complications increased as the attempted astigmatic correction increased.

SATISFACTION AFTER PHOTOREFRACTIVE KERATECTOMY

PURPOSE To evaluate patient satisfaction one year after photorefractive keratectomy (PRK) for myopia and myopia astigmatism using the Nidek EC-5000 excimer laser. METHODS This study assessed the level of satisfaction of 6280 patients who underwent PRK after a minimum follow-up of 1 year. All patients were asked to enter their level of satisfaction as excellent, good, worthwhile, or disappointed into a networked computer database. Their responses were subsequently analyzed according to baseline and postoperative refractive data. RESULTS Patients considered their results to be as follows: 82.3% good or excellent, 14.9% worthwhile, and 2.8% were disappointed with the outcome. CONCLUSION A high percentage of patients were satisfied with the outcome following PRK. However, a fair number (14%) of patients considered the treatment to be worthwhile but it did not meet their expectations. Extensive counseling and inculcating realistic expectations before treatment is essential in achieving better patient satisfaction.

Efficacy of topical nonsteroidal drops as pain relief after excimer laser photorefractive keratectomy.

PURPOSE To compare the efficacy of topical aqueous indomethacin and ketorolac for pain relief following excimer laser photorefractive keratectomy (PRK). METHODS We conducted a double masked, randomized trial involving 120 patients. All patients received a standard regimen of one of the trial drugs and chloramphenicol ointment to be used four times daily for 2 days. Pain levels and quality were assessed on a 10 cm linear analogue scale prior to each instillation of the topical medication with the McGill pain questionnaire. Pain threshold was evaluated using a modified State Trait Anxiety Inventory questionnaire. Patients were advised to use paracetomol for additional pain relief but were allowed to use any oral analgesic (except nonsteroidal agents) which they documented (type and quantity). RESULTS There was no significant difference in pain scores between the groups using indomethacin and ketoralac. CONCLUSION We found no significant difference between topical ketoralac and aqueous indomethacin as pain relief following excimer laser PRK. Both drugs seemed to significantly reduce pain.

Effects of Topical Corticosteroids after Photorefractive Keratectomy

PURPOSE To assess the effects of topical corticosteroids (fluoromethalone) following photorefractive keratectomy (PRK). METHODS Both eyes of 654 patients had PRK with a minimum of 4 months between treatments. Topical corticosteroids were prescribed for one eye only. Endpoints were assessed by comparing the ratio of intended to actual refractive change in the corticosteroid treated eye with the fellow eye (no corticosteroid use). RESULTS The corticosteroid treated eyes showed a mean percentage correction of 95.7% compared to the untreated fellow eyes, which achieved a percentage correction of 103.3%-statistical significance of p = 0.00001. There was more of a trend toward regression in the corticosteroid treated eyes despite intervention with fluoromethalone. CONCLUSION Topical corticosteroids showed very little positive effect on regression of effect after PRK.

Effect of an Elliptical Optical Zone on Outcome of Photoastigmatic Refractive Keratectomy

BACKGROUND This study presents the effect of an elliptical optical zone on the accuracy of correction of astigmatism in patients undergoing photorefractive astigmatic keratectomy (PARK) for myopic astigmatism. METHODS We reviewed a consecutive case series of 102 eyes that underwent PARK with a Nidek EC-5000 excimer laser by a single surgeon. Group A consisted of 50 eyes treated using a circular optical zone of 6.5 mm x 6.5 mm with a 7.5-mm x 7.5-mm transition zone. Group B consisted of 52 eyes treated using an elliptical optical zone of 5.5 mm x 6.5 mm with a 6.5-mm x 7.5-mm transition zone. Refraction was measured preoperatively and postoperatively, and vector analysis was used to study the change in astigmatism induced by surgery. RESULTS Mean correction index improved from 75% in Group A to 100% in Group B. Mean angle of error was reduced from 15.8 degrees in Group A to 7.5 degrees in Group B. Hyperopic shift was reduced from +0.70 D in Group A to +0.20 D in Group B. CONCLUSIONS Excimer laser photorefractive astigmatic keratectomy using an elliptical optical zone improved the correction index for astigmatic change and reduced the mean angle of error. An elliptical optical zone is more effective than the circular optical zone for the treatment of astigmatism in patients with compound myopic astigmatism.