Hong Bok Kim

Comparison of tear secretion and tear film instability after photorefractive keratectomy and laser in situ keratomileusis

Purpose: To evaluate and compare tear secretion and tear film instability following photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Setting: Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea. Methods: In a prospective study, 36 eyes (21 patients) had PRK and 39 eyes (25 patients) had LASIK to correct myopia. Tear secretion and tear film instability were tested preoperatively and 3 and 6 months postoperatively using Schirmer test values, tear breakup time (BUT) scores, and tear osmolarity. Results: Six months after surgery, the change in Schirmer test values from preoperative levels was –14.57% ± 6.39% (SD) in the PRK eyes and –23.40% ± 5.94% in the LASIK eyes and the change in BUT scores, –12.54% ± 8.28% and –18.79% ± 13.01%, respectively. The change in tear osmolarity was 14.95% ± 6.46% and 35.63% ± 8.51%, respectively. Conclusions: The decrease in tear secretion was greater after LASIK than after PRK at 6 months. Proper treatment of dry eye is required after LASIK and PRK, particularly in the LASIK postoperative period.

Expression and Distribution of Extracellular Matrices during Corneal Wound Healing after Keratomileusis in Rabbits

We compared the corneal wound healing responses of keratomileusis and keratectomy in rabbits. A single pass of thin lamellar keratectomy was performed with a microkeratome in rabbits. The lenticule was repositioned with a hinge in one group and discarded in the other. With immunofluorescence techniques, we studied the appearance and distribution of fibronectin, fibrinogen and type III collagen at follow-up intervals from 1 h to 3 months. Fibronectin and fibrinogen began to deposit on the periphery of the denuded stroma 3 h after induced injury and diminished once reepithelialization had completed in both groups. In the corneas with attached lenticules, type III collagen was detected 7 days after surgery and lasted for at least 3 months. Type III collagen was detected only in the periphery of the interface and not in its center. These findings suggest that fibronectin and fibrinogen may play roles in epithelial healing after in situ keratomileusis in rabbits. Stromal healing of colla- gen seems to take place 7 days after keratomileusis and to last for several months. No deposits of new collagens in the center of the interface between lenticule and stromal bed may explain the optical clarity in the keratomileusis.

Effect of 0.2% Brimonidine in Preventing Intraocular Pressure Elevation after Nd:YAG Laser Posterior Capsulotomy

BACKGROUND AND OBJECTIVE To determine the prophylactic effect of 0.2% brimonidine in reducing the elevated intraocular pressure (IOP) in patients undergoing Nd:YAG laser posterior capsulotomy. PATIENTS AND METHODS The 81 patients (81 eyes), who underwent Nd:YAG laser posterior capsulotomy, were allocated to two treatment groups. One drop of 0.2% brimonidine or vehicle was instilled 1 hour preoperatively and one drop immediately after capsulotomy. IOPs were measured preoperatively and 1, 2, 3, and 24 hours postoperatively. RESULTS Intraocular pressure decreased from the baseline in the brimonidine group by the third postoperative hour (P<0.05), while the vehicle group exhibited an increase. Intraocular pressure elevations of 5 mm Hg or greater occurred in 7.3% (3/41) in the brimonidine group compared to 20.0% (8/40) in the vehicle group. IOP elevations of 10 mm Hg or greater occurred in 2.4% (1/41) in the brimonidine group compared to 7.5% (3/40) in the vehicle group. CONCLUSIONS One drop of 0.2% brimonidine instilled 1 hour preoperatively and immediately after capsulotomy was found to be efficacious and safe in preventing IOP elevations that frequently follow Nd:YAG laser posterior capsulotomy.

Letter to the Editor · Travail original · Originalarbeit

Dear Sir, In the article ‘Iris Cyst in Aphakic Patient: Improvement of Visual Acuity after excision’ by Di Maria et al. [Ophthalmologica 1997;211:312–315], the authors describe their short-term result of partial resection of a postoperative cystic epithelial ingrowth of the iris and chamber angle by sector iridectomy. However, in our experience with over 100 patients with cystic or diffuse epithelial ingrowth treated by block excision [1–3] and by histopathologic studies of over 200 specimens with epithelial ingrowth [4], there is a definitive risk of transforming cystic ingrowth into diffuse epithelial downgrowth by partial removal of cystic epithelial ingrowth. Diffuse epithelial downgrowth is frequently relentlessly progressive and leads to loss of the eye. Therefore, we firmly believe that the treatment of choice for epithelial ingrowth is complete excision of all epithelial layers which usually requires block excision of the adjacent cornea, iris, chamber angle and ciliary body with a full-thickness corneoscleral graft. Although block excision of epithelial ingrowth may at first glance appear to be a rather aggressive procedure, our experience shows that the morphological and functional results of block excision are – with regard to the preoperative situation – generally good with no recurrence of epithelial ingrowth and avoidance of enucleation [1–3]. We strongly recommend not to treat cystic epithelial ingrowth with argon laser coagulation, YAG laser coagulation or partial excision because these procedures put the patient at an unnecessary and unacceptable risk of developing diffuse epithelial ingrowth with a poor prognosis. Epithelial ingrowth is a treatable condition if detected before it extends over more than 4–5 clock hours in the chamber angle and if treated adequately. Far too frequently, we have seen patients with advanced untreatable cystic or diffuse epithelial ingrowth who elsewhere had undergone previous unsuccessful surgical attempts to partially excise, ‘shrink’, ‘coagulate’ or ‘puncture’ cystic epithelial ingrowth.