Samir J. Bechara

KERATOCONUS IN TWO PAIRS OF IDENTICAL TWINS

We studied two sets of identical twins with keratoconus. The first 21-year-old pair had bilateral fully developed keratoconus and the second 35-year-old pair presented with early bilateral keratoconus detected by videokeratography. To our knowledge, these are the seventh and eighth sets of identical twins with keratoconus reported in the literature. They support the evidence of heredity as a factor in the etiology of keratoconus. Videokeratography proved to be a valuable adjunct for the detection of early keratoconus in a cornea with normal slit-lamp microscopy and photokeratoscopy results. Radial keratotomy in one eye produced an unstable refraction.

The Effect of Globe Fixation on Ablation Zone Centration in Photorefractive Keratectomy

PURPOSE For optimal vision, the ablation zone in photorefractive keratectomy should be centered over the entrance pupil. During ablation, the globe can be immobilized by the surgeon, with a suction ring around the corneoscleral limbus. Alternatively, the globe can be immobilized by patient fixation on a target, unassisted by the surgeon. We investigated which method results in better centration of the ablation zone over the entrance pupil, by using an objective, mathematical method to determine the ablation zone center. METHODS Forty-eight eyes from 48 patients who underwent photorefractive keratectomy by the two techniques were studied retrospectively. The centers of the ablation zones were objectively determined by a weighted center of mass algorithm applied to the preoperative minus postoperative difference maps. The validity of the objective method was confirmed by comparison to subjective estimates of ablation zone centers made by independent human observers. RESULTS The 19 eyes treated by surgeon fixation had an average decentration of the ablation zone of 0.63 +/- 0.31 mm (range, 0.01 to 1.00 mm), and the 29 eyes treated by patient fixation had an average decentration of 0.41 +/- 0.23 mm (range, 0.11 to 1.18 mm) (P = .027). CONCLUSIONS The center of the ablation zone can be determined mathematically from the topographic map, to avoid observer bias. In this study, unassisted patient fixation during photorefractive keratectomy produced more accurate centration of the ablation zone than did surgeon fixation and has the potential for maximizing the quality of vision postoperatively.

Advances in femtosecond laser technology

Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures.

Corneal Collagen Cross-linking in Advanced Keratoconus: A 4-Year Follow-up Study.

PURPOSE To analyze the safety and efficacy of standard corneal collagen cross-linking (CXL) in advanced cases of progressive keratoconus after 4 years of follow-up. METHODS A retrospective case series of patients with advanced progressive keratoconus (stages 3 and 4 of Amsler-Krumeich classification) underwent standard CXL treatment. The parameters examined were changes in uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), keratometry values (mean, flat, steep, and apical), pachymetry, and endothelial cell count at the baseline and at 12, 24, and 48 months postoperatively. RESULTS Forty eyes of 40 patients were enrolled in the study. The mean patient age was 22.5 years (range: 15 to 37 years). Both mean UDVA and CDVA remained stable during the time points; no statistically significant change was noted. Although a slight reduction was observed in all keratometric readings, a statistically significant reduction was only reached in the apical keratometry (P = .037) at 4 years after CXL. A significant reduction in the corneal thickness was also found (ultrasonic: 388 ± 49 to 379 ± 48 μm; slit-scanning: 362 ± 48 to 353 ± 51 μm); however, this change was likely not clinically meaningful. Endothelial cell count was not significantly different at the end of the study. Treatment failure or progression was noted in two patients (5%) over the follow-up period. CONCLUSIONS Standard CXL treatment was safe and able to stabilize both visual acuity and topographic parameters at 4 years of follow-up in eyes with advanced keratoconus. [J Refract Surg. 2016;32(7):459-464.].

Improved Evaluation of Postoperative Pain After Photorefractive Keratectomy

Purpose: Postoperative pain remains an important limiting factor to the selection of photorefractive keratectomy (PRK). There is a consensus in neurology pain research that pain should be evaluated as a multidimensional concept, which differs from current practice in ophthalmology. The purpose of this paper was to validate the use of multidimensional questionnaires, such as the Brief Pain Inventory (BPI) and the McGill Pain Questionnaire (MPQ), to provide an improved analysis of pain after PRK and to better describe its temporal profile. Methods: This prospective study included 43 eyes of 43 myopic patients who underwent unilateral PRK. After surgery, usual pain treatment was administered. All of the participants responded to the Visual Analogue Scale (VAS), the BPI and the MPQ 1, 24, 48, 72, and 96 hours after surgery. The internal consistency was evaluated, different postoperative periods were compared, and convergent validity was assessed using correlation testing. Results: The Cronbach alpha test showed high internal consistency for each of the questionnaire subscales. Patients reported higher postoperative pain values at the first measurement of the VAS (4.93 ± 2.38), MPQ-pain rating index (26.95 ± 10.58), BPI-pain severity index (14.53 ± 7.36), and BPI-pain interference index (22.30 ± 15.13). Almost all of the scales and subscales showed a statistically significant direct correlation with the VAS at all of the evaluation periods. Conclusions: This study validated the utility of multidimensional questionnaires to expand the assessment of the PRK postoperative pain profile, including intensity and other qualitative aspects.

Codeine Plus Acetaminophen for Pain After Photorefractive Keratectomy: A Randomized, Double-blind, Placebo-controlled Add-on Trial

Background: Pain after photorefractive keratectomy (PRK) is significant, and the analgesic efficacy and safety of oral opioids in combination with acetaminophen has not been fully investigated in PRK trials. Purpose: To assess the efficacy and safety of the combination of codeine plus acetaminophen (paracetamol) versus placebo as an add-on therapy for pain control after PRK. Study design: Randomized, double-blind, placebo-controlled trial. Setting: Single tertiary center. Methods: One eye was randomly allocated to the intervention, whereas the fellow eye was treated with a placebo. Eyes were operated 2 weeks apart. The participants were adults older than 20 years with refractive stability for ≥1 year, who underwent PRK for correction of myopia or myopic astigmatism. Codeine (30 mg) plus acetaminophen (500 mg) was given orally 4 times per day for 4 days after PRK. The follow-up duration was 4 months. The study outcomes included pain scores at 1 to 72 hours, as measured by the visual analog scale, McGill Pain Questionnaire, and Brief Pain Inventory, as well as adverse events and corneal wound healing. Results: Of the initial 82 eyes, 80 completed the trial (40 intervention, 40 placebo). Median (interquartile range) pain scores as measured by the visual analog scale were statistically and clinically lower during treatment with codeine/acetaminophen compared with the placebo: 1 hour: 4 (2–4) versus 6 (3–6), P < 0.001; 24 hours: 4 (3–6) versus 7 (6–9), P < 0.001; 48 hours: 1 (0–2) versus 3 (2–5), P < 0.001; and 72 hours: 0 (0–0) versus 0 (0–2), P = 0.001. Virtually identical results were obtained by the McGill Pain Questionnaire and Brief Pain Inventory scales. The most common adverse events with codeine/acetaminophen were drowsiness (42%), nausea (18%), and constipation (5%). No case of delayed epithelial healing was observed in both treatment arms. Conclusions: When added to the usual care therapy, the oral combination of codeine/acetaminophen was safe and significantly superior to the placebo for pain control after PRK. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02625753.

Predictors of Early Postoperative Pain After Photorefractive Keratectomy.

Purpose: To compare the profiles of postoperative photorefractive keratectomy (PRK) pain between both eyes under the same conditions and to verify the preoperative predictors of pain such as gender, anxiety, knowledge of the procedure, and spherical equivalent refractive error (SERE). Methods: This prospective study included 86 eyes of 43 patients with myopia who underwent PRK in both eyes at an interval of 14 days between the procedures. Before surgery, subjects answered the State Anxiety Inventory. After surgery, usual PRK pain treatment was given. Subjects answered the Visual Analog Scale, the Brief Pain Inventory (BPI), and the McGill Pain Questionnaire at 1, 24, 48, 72, and 96 hours after surgery. Pain scores and anxiety were compared between each eye using the Wald test and paired Student t test, respectively. The Wald test was performed for gender and SERE for each eye separately. Results: There were no statistically significant differences between both eyes for all time points regarding the Visual Analog Scale, BPI, and McGill Pain Questionnaire–Pain Rating Index pain scores. Subjects were less anxious on average before the second surgery compared with before the first surgery (P < 0.001); however, it was not related to pain ratings after surgery. Gender did not significantly affect any scale of pain, and the SERE between −3 diopters (D) and −5 D (P = 0.035) revealed effects on the BPI. Conclusions: The profiles of postoperative pain after PRK were similar between both eyes under the same conditions. In this study, a high SERE was the only predictor for increased pain after PRK.