Photorefractive keratectomy for correction of myopia: Our one-year experience

Background/Aim. Photorefractive keratectomy (PRK), after laser in situ keratomileusis (LASIK), is commonly performed refractive surgical method worldwide. The aim of this study was to examine the effectiveness and safety of PRK in correction of various strengths of myopia and to assess how much corneal tissue is being removed with one diopter sphere (Dsph) correction by using different optical zones (OZ). Methods. A prospective study with a follow-up period of 6 months included 55 patients of which 100 myopic eyes were treated by PRK method (one eye was included in 10 patients). Myopic eyes with a preoperative best corrected visual acuity (BCVA) = 1.0 (20/20) were analysed. In order to assess the effectiveness of PRK operated myopic eyes were divided into four groups according to the dioptric power: 1)≤ -1.75 Dsph (n = 26); 2) from -2 to -3.75 Dsph (n = 44); 3) from -4 to -6.75 Dsph (n = 23), and 4) ≥ -7 Dsph (n = 7). Myopic eyes with preoperative BCVA ≤ 0.9 (amblyopic eyes) were excluded from the study, as well as eyes with astigmatism > -1.5 Dcyl. To assess the effectiveness of PRK we examined the percentage of eyes in the mentioned groups, which derived uncorrected visual acuity (UCVA) 6 months after the intervention to the following: a) UCVA = 1.0 (20/20) and b) UCVA ≥ 0.5 (20/40). To assess the safety of PRK we examined the frequency of intraoperative and postoperative complications. To estimate how much corneal tissue was removed with one Dsph correction by using different OZ, we used preoperative and postoperative (after 6 months) central pachymetry values expressed in μm and volume of cornea (central 7 mm) expressed in mm³. In that sense, we used only the myopic eyes with clear preoperative spherical refraction. The total number of these eyes was 27, of which 16 eyes were treated using a 6.5 mm OZ and 11 eyes using a 7 mm OZ. Results. Refractive spherical equivalent (RSE) for all eyes was in the range from -0.75 to -8.75 Dsph, and preoperative mean value of RSE with standard deviation (mean RSE ± SD) was -3.32 ± 1.83 Dsph. Six months after PRK, 91% of eyes had UCVA = 20/20, and 99% of eyes had UCVA ≥ 20/40. In the first group (≤ -1.75 Dsph) preoperative mean RSE ± SD was -1.34 ± 0.32 Dsph, six months after PRK, 96% of eyes had UCVA = 20/20, and 100% of eyes had UCVA ≥ 20/40. In the second group (from -2 to -3.75 Dsph) preoperative mean RSE ± SD was - 2.95 ± 0.57 Dsph, six months after PRK, 89% of eyes had UCVA = 20/20, and 100% of eyes had UCVA ≥ 20/40. In the third group (from -4 to -6.75 Dsph) preoperative mean RSE ± SD was - 4.93 ± 0.70 Dsph, six months after PRK, 100% of eyes had UCVA = 20/20. In the fourth group (≥ - 7 Dsph) preoperative mean RSE ± SD was -7.71 ± 0.67 Dsph, six months after PRK, 57% of eyes had UCVA = 20/20, and 86% of eyes had UCVA ≥ 20/40. There were no intraoperative complications while postoperative complications occurred in 2 patients - in both cases in one eye (2%). In that cases, epithelial defects were detected. In the group of eyes that were treated by 6.5 mm OZ mean RSE ± SD was -2.45 ± 0.99 Dsph, the ablation depth per 1 Dsph was 17.54 ± 5.58 μm and ablated volume of central 7 mm cornea by 1 Dsph was 0.43 ± 0.18 mm³. In the group of eyes that were treated by 7 mm OZ mean RSE ± SD was -3.32 ± 2.26 Dsph, the ablation depth per 1 Dsph was 23.73 ± 6.91 μm and ablated volume of central 7 mm cornea by 1 Dsph was 0.61 ± 0.31 mm³. Conclusion. PRK is effective and safe refractive surgical method for correcting myopia up to -8 .75 Dsph. OZ size is the main factor determining the depth of the excimer laser ablation of the corneal tissue volume consumed by 1 Dsph. Higher OZ value determines higher consumption of cornea tissue

Evolution of cataract surgery: Smaller incision - less complications

Background/Aim. Cataract surgery has become one of the safest procedures in medicine thanks to advances in technology and surgical techniques. Although minimal, we still witness different complications. The aim of this study was to compare visual outcome and complication rate in different techniques of cataract surgery, ie in cataract surgeries with various corneal incision width. Methods. The study included 3,457 consecutive patients, ie 4,670 eyes that had undergone cataract surgery. The used surgical techniques were: extracapsular cataract extraction, phacoemulsification/ forceps IOL implantation, phacoemulsification/ injector IOL implantation, microincision cataract surgery (MICS). Patient follow up was 6 months. Patients were evaluated for: visual aquity, corneal astigmatism, cellular reaction in the anterior chamber, IOL position. Results. Uncorrected visual aquity 30 days postoperatively was ≥ 0.5 in 30% of the eyes - ECCE; 54.7% of the eyes - phacoemulsification/forceps IOL implantation; 63.0% of the eyes - phacoemulsification/injector IOL implantation; 5/8 of the eyes - MICS. Endophthalmitis was detected in 0.15% of the eyes - ECCE and 0.1% of the eyes - phacoemulsification/forceps IOL implantation. In eyes with phacoemulsification/injector IOL implantation or microincision cataract surgery (MICS) there were no cases of endophthalmitis. After a 6-month period intraocular lens were dislocated in 7.2% of the eyes - ECCE, and 0.6% of the eyes - phacoemulsification/PMMA IOL. There was no IOL dislocation in other surgical techniques. Conclusion. Shorter corneal incision implies less complications, less operative trauma, faster visual rehabilitation and better visual outcome

Levels of interleukin-6 in tears before and after excimer laser treatment

Immune response and consequent inflammatory process which originate on ocular surface after a trauma are mediated by cytokines. Photoablation of corneal stroma performed by excimer laser causes surgically induced trauma. Interleukin-6 (IL-6) is mostly known as a proinflammatory cytokine. However, it also has regenerative and anti-inflammatory effects. It is supposed that this cytokine is likely to play a significant role in the process of corneal wound healing response after photoablation of stroma carried out by laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) methods. The aim of this study was to determine and compare the levels of IL-6 in tears before and after treatment with LASIK and PRK methods

High-frequency deep sclerotomy, a minimal invasive ab interno glaucoma procedure combined with cataract surgery: physical properties and clinical outcome

Background: The efficiency and safety of primary open-angle glaucoma with high-frequency deep sclerotomy (HFDS) combined with cataract surgery has to be investigated. Methods: Right after cataract surgery, HFDS was performed ab interno in 205 consecutive patients with open angle glaucoma. HFDS was performed with a custom-made high-frequency disSection 19 G probe (abee tip 0.3 x 1 mm, Oertli Switzerland). The bipolar current with a frequency of 500 kHz is applied. The nasal sclera was penetrated repetitively six times through the trabecular meshwork and consecutively through Schlemm's canal. Every time, a pocket of 0.3 mm high and 0.6 mm width was created. Results: Mean preoperative intraocular pressure (IOP) was 24.5 +/- 2.1 mmHg (range 21 to 48 mmHg). After 48 months, the follow up average IOP was 15.0 +/- 1.7 mmHg (range 10 to 20 mmHg). Postoperative IOP has been significantly reduced compared to preoperative IOP for all studied cases (p < 0.001). After 48 months, the target IOP less than 21 mmHg reached in 84.9%. No serious complications were observed during the surgical procedure itself and in the postoperative period. Conclusions: HFDS is a minimally invasive procedure. It is a safe and efficacious surgical technique for lowering IOP combined with cataract surgery

Arteficial monoblock lenses implantation following rupture of posterior capsule during phacoemulsification surgery

Background/Aim. Phacoemulsification is a modern surgical technique for cataract operations. Through minimal corneal wound (2.2-2.7 mm) lens nucleus is emulsificated and arteficial lens is implanted in capsular bag. Complications during operations are possible, and can vary from minor to very serious one, with consecutive visual loss. One of possible complications is rupture of posterior lens capsule, which could happen in any stage of operation. The aim of this study was to evaluate results of monoblock arteficial lens implantation in sulcus on the remains of anterior capsule and capsulorhexis after posterior capsule rupture during phacoemulsification. Methods. This prospective, non-comparative study included 19 patients with rupture of posterior capsule as a result of cataract operation with phacoemulsification method. Average monitoring time was 14 months (1-18). We analysed best corrected visual acuity, intraocular pressure, fundus findings, and implanted lens position with wawelight allegro oculizer (Scheimpflug camera). Results. Preoperative visual acuity was from L+P+ to 0.5. On first postoperative day visual acuity 0.02-0.08 was noted in 8 patients, from 0.1-0.4 also in 8 patients and 0.5 and more in 3 patients. After 12 months from the operation 15 patients had visual acuity better than 0.5. Among early complications corneal edema was noted in 6 cases, anterior chamber reaction with or without fibrin reaction in 8 cases and rise of intraocular pressure in 3 cases. All complications were reversibile. Conclusion. Posterior capsule rupture/break is a serious complication of phacoemulsification, hardly to prevent. Regarding size of posterior rupture, foldable monoblock arteficial lens can be implanted into the sulcus on the remains of anterior capsule in most of the cases, keeping the advantages of small corneal incision: smaller astigmatism, better postoperative visual acuity, faster wound healing and earlier visual rehabilitation

Why use ultrashort pulses in ophthalmology and which factors affect cut quality

The power density of femtosecond lasers and exposure time to the tissue are crucial for a successful procedure in terms of safety and precision. The reduction of the pulse duration allows reducing the quantity of the energy to be delivered to the tissue for disruption with strongly diminished mechanical and thermal collateral damage. The cutting effect of ultra-short pulses is very precise, minimally traumatic, safe, and predictable. Future developments will lead to further energy reductions to achieve optical breakdowns. However, the pulse length cannot be shortened arbitrarily because below 100 fs nonlinear effects can change the process in an unfavorable way. Compared to manual-conventional cataract surgery, femtosecond laser-assisted cataract surgery (FLACS) shows many advantages in clinical application, especially with regard to precision and tissue protection. The femtosecond laser has become particularly important and has made the overall procedure safer when we deal with complex cataract cases such as subluxated lenses. We provide an overview of the evolution of femtosecond laser technology for use in refractive and cataract surgeries. This article describes the advantages of available laser platforms with ultrashort pulses and mainly focuses on the technical and physical backgrounds of ophthalmic surgery technologies

Levels of interleukin-6 in tears before and after excimer laser treatment

Background/Aim. Immune response and consequent inflammatory process which originate on ocular surface after a trauma are mediated by cytokines. Photoablation of corneal stroma performed by excimer laser causes surgically induced trauma. Interleukin-6 (IL-6) is mostly known as a proinflammatory cytokine. However, it also has regenerative and anti-inflammatory effects. It is supposed that this cytokine is likely to play a significant role in the process of corneal wound healing response after photoablation of stroma carried out by laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) methods. The aim of this study was to determine and compare the levels of IL-6 in tears before and after treatment with LASIK and PRK methods. Methods. The study included 68 shortsighted eyes up to -3.0 diopter sphere, i.e. 198 samples of tears (per three samples taken from each of the eyes), divided into two groups according to the kind of excimer laser intervention performed: the group 1 - eyes treated by LASIK method (n = 31), and the group 2 - eyes treated by the PRK method (n = 37). The samples of tears were taken from each eye at the following time points: before excimer laser treatment (0 h, the control group), 1 h after the treatment (1 h) and 24 h after the treatment (24 h). The patients did not use anti-inflammatory therapy 24 h after the intervention. Tear samples were collected using microsurgical sponge. Level of IL-6 in tear fluid was determined by the flow cytometry method, applying a commercial test kit which allowed cytokine detection from a small sample volume. Results. The values of IL-6 were detectable in 16% of samples before LASIK treatment and in 30% of samples before PRK treatment. One h after the treatment IL-6 was detectable in 29% of samples for the LASIK group and 43% of samples for the PRK group, and 24 h after the treatment it was detectable in 19% of samples for the LASIK group and in 57% of samples for the PRK group. When we analyzed the dynamics of IL-6 production in particular groups, we noticed that both in the LASIK and PRK group the number of samples with increased values of IL-6 after 1 h, and after 24 h, was considerably larger than the number of samples with decreased values of IL-6 after the intervention. Analyzing the dynamics of IL-6 concentration changes in the 1 h samples vs 24 h samples there was a statistically significant increase in the number of samples with IL-6 concentration decline in the LASIK group, while at the same time no considerable changes occurred in the PRK group. Comparing average IL-6 values between the two treatment groups in all tear samples at 0 h, 1 h and 24 h after intervention a significantly higher level in the PRK group 24 h after procedure (p = 0.0031) was detected. Conclusion. IL-6 level in tears increases 1 h and 24 h after LASIK and PRK treatments. This increment is significantly larger 24 h after the treatment with the PRK method than with the LASIK method. Changes of IL-6 production levels in tears after excimer laser treatment indicate that this cytokine takes part in the corneal recovery process after stromal photoablation