Anterior Radial Keratotomy Research Articles

MACHINE LEARNING AND ARTIFICIAL NEURAL NETWORK TECHNOLOGIES IN THE CLASSIFICATION OF POSTKERATOTOMIC CORNEAL DEFORMITY

Backgraund: A thorough analysis of both the optical and anatomical properties of the cornea in patients after anterior radial keratotomy is of particular importance in choosing the optical strength of an intraocular lens in the surgical treatment of cataracts and other types of optical correction. The variability of the clinical picture of postkeratotomic deformity (PCRD) determines the need to develop its classification and is an important task of modern ophthalmology.
 Aims: to develop an automated system of classification of corneal PCRD using machine learning and an artificial neural network based on the analysis of topographic maps of the cornea.
 Materials and methods: depersonalized results of the analysis of medical records of 250 patients aged 59.63±5.95 (from 46 to 76) years were used as the material. The analysis of 500 maps of the relief-topography of the anterior and posterior surfaces of the cornea and 3 stages of machine learning of the PCRD classification were carried out.
 Results: Stage 1- analysis of the relief topography of the anterior and posterior surfaces of the cornea allowed us to fix the numerical values of the elevation of the anterior and posterior surfaces of the cornea in three ring-shaped zones. At stage 2, in the course of deep machine learning, a direct distribution neural network was selected and created. 8 auxiliary parameters describing the shape of the anterior and posterior surfaces of the cornea were established. Stage 3 was accompanied by obtaining algorithms for the classification of PCRD depending on the ratio of test and training samples, which ranged from 75 to 91%..
 Conclusion: The use of artificial neural network algorithms can become a useful tool for automatic classification of postkeratotomic corneal deformity in patients who have previously undergone radial keratotomy.

Клиническая эффективность хирургического лечения катаракты у пациентов после ПРК с использованием основных формул расчета оптической силы ИОЛ

Purpose. To analyze possible refractive errors when calculating IOL power in patients after ARK (anterior radial keratotomy). Material and methods. The data of Intraocular lens (IOL) power calculation in 46 patients (46 eyes) with anterior radial keratotomy (ARK) who also underwent cataract surgery were analyzed. The IOL calculation was performed taking into account the data obtained by the Lenstar LS 900 (HAAG-STREIT AG, Switzerland) and keratotopography (Pentacam HR, Oculus, Germany), with a target refraction corresponding to emmetropia up to ±0.50 D. Results. The analysis of the clinical efficacy of phacoemulsification with IOL implantation in patients after ARK with the refractive error (RE) calculation and refractive prediction error (RPE) calculation according to the basic formulas were performed. It was found that emmetropia (up to ±0.5 D) in the postoperative period was achieved in 52% of cases. The value of the postoperative RPE had no reliable dependence on the values of the eyeball length, it was depended on the corneal optical power in the central zone of the cornea only with some formulas for IOL calculation (Barrett, Barrett Universal II, MIKOFRK/ALF). The obtained results of the analysis provide justification for a deeper study of post keratotomy corneal deformation as a pathological condition with the presence of hidden risk factors. Conclusion. Phacoemulsification with IOL implantation in patients with previously performed ARK is accompanied by the achievement of target refraction in 52% of cases. The high proportion of IOL calculation errors in cataract surgery in patients after ARK largely depends on hidden factors, which determines the need for a detailed study of post keratotomy corneal deformation as a pathological condition. Key words: IOL power calculation, anterior radial keratotomy, emmetropia

Experience of Using Corneal Epithelium Protector Gel for the Treatment of Corneal Erosion for a Patient after Radial Keratotomy

Currently, one of the actual problems of pharmacotherapy is the treatment of recurrent corneal erosions. Traumatic and postoperative damage to the cornea can disrupt the connection between the basement membrane and the epithelium. One type of such predisposing factors that disrupt the connection between the epithelium and the basement membrane is a previously performed anterior radial keratotomy. This article describes a clinical case using off-label “Protector of corneal epithelial SPHERO®oko gel” within the complex treatment of traumatic corneal erosion for a patient after radial keratotomy. A conservative treatment includes applying 5 % dexpanthenol gel, 0.05 % picloxidine solution, a tear substitute and Corneal Epithelium Protector (BIOMIR Service, Russia) 4 times a day until the erosion was closed and then again during 2 weeks. On the 14th day complete epithelization of the cornea was achieved. Within 2 weeks the condition remained stable. Protector of corneal epithelial showed its effectiveness in complex treatment of traumatic corneal erosion for a patient after radial keratotomy.

Розрахунок параметрів тунельного розрізу при факоемульсифікації у хворих з раніше проведеною передньою радіальною кератотомією

Мета. Вибір типу тунельного розрізу на підставі математичних розрахунків у хворих на катаракту з раніше проведеною передньою радіальною кератотомією. Матеріали та методи. У розрахунках використовувалась формула довжини хорди окружності: L = 2R · sin(α/2), де R — радіус рогівки, α — кут у градусах між двома рогівковими надрізами. Довжину хорди вимірювали на лімбі (верхній край тунельного розрізу) та 2 мм від лімба (ніжній край тунельного розрізу). Більш важливою є хорда 2 мм від лімба, тому що відстань між кератотомічними розрізами в цьому місці є меншою. До ширини леза ножа необхідно додати ще від 0,4 мм до 1,0 мм залежно від типу післяопераційного загоювання рогівки, що і буде запорукою пересічення розрізів. Результати. Найпоширенішими є ножі 2,2 мм та довжиною тунелю 2 мм. Тому проводимо розрахунки на базі цього ножа у пацієнтів з 8 та 12 кератотомічними розрізами та діаметром рогівки 12 мм за вертикаллю та 11 мм за горизонталлю. У пацієнтів з 8 кератотомічними розрізами є можливість використовувати ніж 2,2 мм для рогівкового тунельного розрізу, а у хворих з 16 насічками використання рогівкового тунелю неможливе. Висновки. У пацієнтів, хворих на катаракту, в яких раніше була проведена передня радіальна кератотомія, потрібен особливий підхід щодо вибору тунельного розрізу. Вибір доступу залежить від діаметра рогівки, кількості кератотомічних надрізів та ширини ножа і вираховується за допомогою формули довжини хорди окружності.

Формирование роговичного тоннельного разреза с пересечением кератотомических рубцов у пациентов после радиальной кератотомии при факоэмульсификации

Purpose. A clinical study of safety and changes of refraction during intersection of a keratotomy scar while performing the corneal tunnel incision in phacoemulsification with IOL implantation. Material and methods. The clinical study included 11 patients (19 eyes) suffering from cataract and patients with previously performed anterior radial keratotomy. A tunnel incision 2.2 mm wide was performed with the location of the scar in its center. In case of insufficient area of the corneal tissue between the scars to involve only one keratotomy scar into the tunnel incision, the adjacent scar was transected at the final stage of tunnel formation when entering the anterior chamber. The other stages of phacoemulsification were carried out in a standard way. During the operation, the state of the keratotomy scar was assessed. A day, a week and a month later after the operation, the patients underwent biomicroscopy, autorefractokeratometry, visometry with an assessment of the values of subjective and objective cylindrical correction. In order to assess the postoperative state of the keratotomy scar and the incision zone, OCT of the cornea was performed using an RTVue 100 optical coherence tomograph (Optovue, Inc, USA) in Line, Crossline, 3D cornea modes. Results. In all cases, during the operation and also the next day, biomicroscopically the cornea was transparent, there was no keratotomy scar dehiscence. There is a dynamic of the best corrected visual acuity value by 1 month after surgery and the difference between the value for subjective and objective cylinder correction as well. The next day after the operation, in all cases the keratotomy scar on the OCT scans is uniform, comparable in width, the architectonics of the tunnel incision does not differ from that of standard phacoemulsification. Conclusion. Performing a corneal tunnel incision with the beginning of the formation outside the zone of the keratotomy scar and with further intersection of the scar with the plane of the blade so that most of it is in the projection of the center of the tunnel incision, as well as the intersection of the adjacent keratotomy scar at the end of the formation of the tunnel incision when entering the anterior chamber in case of insufficient the area of the corneal tissue between the incisions is safe at all stages of phacoemulsification and in the postoperative period. Changes in the values of best corrected visual acuity over time and the difference between the values of subjective and objective cylinder correction require further study on a larger sample and using various keratometry methods. Key words: radial keratotomy, phacoemulsification, tunnel incision, intersection of the keratotomy scar, cornea optical coherence tomography.

Рельеф-топография передней и задней поверхностей роговицы у пациентов с миопией в отдаленном периоде после передней радиальной кератотомии

Purpose. To analyze the topographical features of the relief of anterior and posterior corneal surfaces in patients with myopia in the long-term period after anterior radial keratotomy (ARK). Material and methods. We examined 132 patients with age-related cataracts of varying degrees of density and a history of myopia with previously performed ARK. Mean age of patients was 59.67±6.09 (from 47 to 76). In the control group, 30 patients of the same age group with myopia were examined. A comprehensive examination was performed, including optical biometry, keratotopography on the Pentacam HR device with the determination of the elevation points of the anterior and posterior corneal surfaces. Results. The corneal profile differed from the correct spherical configuration in the control group. The average deviation of the profile of the anterior part of the cornea from the BFS was (–)1.41±5.10 µm, the posterior part was (–)5.12±12.25 µm (p=0.0001). The profile of the posterior corneal surface had a pronounced prolapse in the paracentral area with positive elevation values in the lower-outer segment. Negative values were found in the upper and lower sectors in the peripheral area and positive values were found in the inner and outer sectors. The corneal profile was deformed in patients after ARK. Negative elevation values in the central and paracentral area and positive elevation values in the peripheral segments corresponding to its protrusion were noted. At the same time, the relief of anterior and posterior surfaces of the cornea was not regular. Prolapse from the posterior surface of the cornea in the peripheral area was more pronounced than its anterior surface (p=0.0001). Conclusion. The relief of anterior and posterior corneal surfaces in patients of the control group differs in the degree and topography of elevation. In patients after ARK, obvious topographic deformities of the anterior and posterior corneal profiles were detected. Key words: anterior radial keratotomy, corneal elevation, myopia.

Оценка профиля роговицы у пациентов с миопией в отдаленном периоде после передней радиальной кератотомии

Оценка профиля роговицы у пациентов с миопией в отдаленном периоде после передней радиальной кератотомии

Сравнительный анализ методов расчета оптической силы ИОЛ у пациентов после передней радиальной кератотомии

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Analysis of Optical Properties of Posterior Surface of Cornea in Patients after Anterior Radial Keratotomy

Taking into account the constant increase in patients with age-related cataracts after radial keratotomy, a careful analysis of both the optical and anatomical properties of the cornea with the examination of the posterior surface is of particular importance.Aim. To analyze the optical properties of the posterior surface of the cornea in patients after anterior radial keratotomy. Materials and methods. An examination of 24 patients (48 eyes) with age-related cataracts of varying degrees of density, myopia and the presence of a previous anterior radial keratotomy or radial-tangential keratotomy in history. The average age of patients was 59.5 years (from 47 to 68), there were 19 women and 5 men.Results. The radius of curvature of the anterior surface in patients after anterior radial keratotomy was 9.45 ± 0.91 mm on average along the meridians, which is significantly more in comparison with these indices in control patients – 7.70 ± 0.19 mm (p = 0.0001). The ratio of the radii of the posterior cornea curvature to the anterior radius on average along the meridians in patients after anterior radial keratotomy was 1.07 ± 0.70, and in control patients – 1.20 ± 0.02 (p = 0.0001). The keratometric index in patients after anterior radial keratotomy was 1.3538 ± 0.0239, and in the control group – 1.3372 ± 0.0003 (p = 0.23).Conclusion. In patients after anterior radial keratotomy, keratometry of the posterior surface of the cornea is significantly higher than in the control. The ratio of the radius of curvature of the posterior cornea to the radius of curvature of the anterior cornea varies significantly after anterior radial keratotomy, which is due to a more pronounced flattening of the posterior cornea. The standard keratometric index (1.3375) is invalid for patients after anterior radial keratotomy and must be calculated individually for each patient when deciding on the operative treatment of cataracts.

Клинико-оптическое состояние роговицы у пациентов со снижением центрального зрения при прозрачности оптических сред в отдаленные сроки после передней радиальной кератотомии

Клинико-оптическое состояние роговицы у пациентов со снижением центрального зрения при прозрачности оптических сред в отдаленные сроки после передней радиальной кератотомии

Клинический случай диагностики и лечения глаукомы у пациента после передней радиальной кератотомии

Клинический случай диагностики и лечения глаукомы у пациента после передней радиальной кератотомии

Long Term Follow-up of the Corneal State after Anterior Radial Keratotomy

Purpose: to investigate the cornea condition in the patients after anterior radial keratotomy in long-term (over 20 years) period. Patients and methods. The study involved 80 patients (147 eyes) aged from 41 to 65 years, who had keratotomy in average 23.9 ± 1.9 years ago. The number of keratotomy scars varied from 6 to 18. Radial keratotomy was performed in 125 eyes, in 22 eyes — radial and tangential keratotomy, repeat radial keratotomy about residual moderate myopia was performed in 3 eyes. Ophthalmologic examination of patients included conventional techniques. Results. In 76.2% of cases in the corneal optical zone were observed accumulation of hemosiderin; in 63.3% — signs of intraoperative micro- and macroperforations, going through all cornea layers, capturing the Descemet membrane and the endothelium, leading to a decrease in the density of endothelial cells. There was subepithelial fibrosis in 2.7% cases; the signs of postkeratotomic keratectasia with expressed refractive disorders and prevalence of hyperopic complex or mixed forms of astigmatism were in 9.5%; during the endothelial microscopy in 21.8% of cases «dark zones» were revealed. It in combination with pleomorphism and polimegatizm indicates a decrease of endothelial functional reserve in patients after anterior radial keratotomy. Conclusions. The special features of the cornea state oafter keratotomy in the long term are including the accumulation of hemosiderin in the corneal optical zone, the signs of intraoperative perforation in the area of keratotomy scars, subepithelial fibrosis, postkeratotomy keratectasia, reducing of the density of endothelial cells, pleomorphism, polimegatizm, «dark zones» found at endothelial microscopy

Phacoemulsification of Cataract in Patients Undergone Anterior Radial Keratotomy

Phacoemulsification of Cataract in Patients Undergone Anterior Radial Keratotomy

Long-term Quantitative and Qualitative Assessment of the Corneal Endothelium after Anterior Radial Keratotomy

Purpose. To determine the long-term status of the corneal endothelium after anterior radial keratotomy. Patients and methods. The main group consisted of 69 patients (104 eyes) who underwent radial or radial-tangential keratotomy to correct myopia and myopic astigmatism an average of 23,1±2,8 years ago (range 16 to 30 years). The average age of patients was 53,8±5,7 years (range 39 to 65 years). The number of keratotomy scars ranged from 4 to 14. Repeated keratotomy was performed on 8 eyes. The control group consisted of 56 patients (110 eyes) aged from 39 to 64 years (average 54,2±4,3 years) with refractive-axial myopia from medium to high stage, whom potentially could be done anterior keratotomy in the 90th of the last century. Patients with concomitant pathology and ocular trauma that could lead to loss of endothelial cells were excluded from both groups. Corneal endothelium cell densit y, polimegatizm, pleomorphism in addition to standard eye examination were performed to all patients with the help of contactless endothelial microscope «EM-3000» company Tomey (Japan). Results. In the control group endothelial cell densit y averaged 2734,8±121,2 cells /mm2, in the main group — 2134,2±299,1 cells/mm2 (p <0,05), in group after repeated keratotomy — 1679,9±327,3 cells/mm2 (p≤0,0001). Endothelial cell densit y in patients with biomicroscopic signs of intraoperative perforation of the cornea — an average of 2012,2±245,7 cells/mm2, without signs of perforation — 2378,4±242,9 cells/mm2. In the main group the coefficient of variation averaged 0,47±0,06, in the control group — 0,28±0,03 (p<0,05). In the main group percentage of hexagonal cells averaged 37,9±9,4, in the control group — 69,2±6,3 (p<0,05). Conclusions. Anterior keratotomy leads to a significant reduction in the endothelial cell densit y, increasing the size and coefficient of variation, decreasing percentage of hexagonal cells in the long-term. Endothelial cell densit y is significantly lower in patients after repeated keratotomy and in patients with the signs of corneal intraoperative perforations.

Corneal ectasia after excimer surgery and the mandelbrot B. fractal theory in ophthalmology

AbstractPurpose To investigate corneal ectasia after LASIK surgery by using the Mandelbrot B. fractal theory in ophthalmology.Methods We reviewed our consecutive 55012 cases of excimer‐laser surgery including LASIK (48910 eyes) and PRK (6102 eyes). We used MEL‐60, MEL‐70 and MEL‐80 excimer laser (“Carl Zeiss Meditec”) and microkeratomes LSK‐Evolution 1, 2 and 3 (“Moria”) for LASIK. Follow‐up period was up to 14 years. The age of all patients was from 18 to 74 years. Some of them had hyperopia with sphere‐equivalence (SE) up to 6,5D, and the others had myopia with SE from –1,0D to –18,0D.Results There was NO corneal ectasia in the PRK and the hyperopic LASIK groups. 38 eyes (0,08%) had corneal ectasia after myopic LASIK (46294 eyes). There were 8 eyes with previous radial keratotomy, 8 eyes with subclinical keratoconus and 22 eyes with normal cornea (0,048% of all myopic LASIK) among the eyes . Pre‐op parameters of these eyes were the followings: central K ‐ 44,37±1,09D, CCT ‐ 530,4±34,4 microns, SE – 5,90±3,36D. Fractal theory allows to explain post‐op corneal ectasia phenomenon.Conclusion There are NO optical methods to predict corneal ectasia after LASIK surgery. But the risk factors of this complication were the followings: steep cornea (more than 44,0 D), corneal scars after previous corneal surgery (e.g. anterior radial keratotomy etc.), corneal topography irregularity and probably very thin residual corneal thickness. Myopic LASIK surgery can provoke post‐op corneal ectasia development in the long follow‐up period. We described post‐op myopic LASIK cornea as a “odd” (“curious”) attractor according to the Mandelbrot B. fractal theory.

Radial keratotomy for the purpose of reducing glasses power in high myopia.

Anterior radial keratotomy for high myopia (over-6.25 diopter) to reduce refractive error was not able to dispense with glasses or contact lenses due to the high myopia itself. However patients could see objects well and were free of dizziness while wearing glasses of relatively reduced power. We performed anterior radial keratotomies on 83 high myopic and/or astigmatic eyes of 47 patients at Kangnam St. Mary's Hospital between May 1990 and Mar. 1991. Eight radial incisions with a diamond blade were performed and the Ruiz technique was added for astigmatism of over 2.0 diopters. The depth of incision was 90 to 95% of corneal thickness and the optical zone was 3mm in diameter. Patients were followed up on postoperative 7 days. 1 month, 3 months, 6 months, 1 year and thereafter. Uncorrected visual acuity of 20/40 or better after radial keratotomy could be obtained in 19.6% of high myopic eyes. A mean reduction of the spherical equivalent cycloplegic refraction of 5.13 diopters and a keratometric reading of 3.89 diopters after radial keratotomy were observed. About 90% of patients were satisfied with their visual outcome with reduced refractive power glasses. We recommend radial keratotomy for high myopic patients to reduce the refractive power and to help them enjoy a more comfortable life.

Sources of Error in Keratotomy Knife Incision

ABSTRACT: Since the introduction of anterior radial and astigmatic keratotomy in the late 1970s, significant attention has been placed on the pachymetric measurement with three different modalities. Pachymetry is only one factor related to the attained depth from the keratotomy incision. Micrometer gem knife footplate design and cutting edge quality provide far greater potential sources of error than involved in the simple measurement of corneal thickness. Micrometer accuracy, chuck stability, footplate design, alignment relationships, blade quality and care, and the precision of the calibration device all can contribute significantly to the accuracy of the incision.

Morphometric analysis of corneal endothelium following radial keratotomy

We performed morphoinetric analysis of the central corneal enclothelium on 24 eyes of 19 patients who had had anterior radial keratotomy. The endothelium was analyzed for a variety of parameters, including cell area, perimeter, side lengths, cell shape, and number of sides. Mean, standard deviation, and coefficient of variation were calculated for each parameter. The mean cell density decreased from 2,8:35 to 2,677 cells/mm2, mean cell perimeter increased from 71.4 μm to 74.3 μm, and mean side length increased from 11.8 μm to 12.3 μm following surgery. The changes in these three parameters were statistically significant (P < 0.05). The coefficient of variation of cell area (polymegathism) changed from 0.319 to 0.307, the hexagonality changed from 62.5% to 59.6%, and the cell shape changed from 0.872 to 0.867. The changes in these parameters were not statistically different before and after surgery. The group of patients that had no reported microperforations shoNved only a small decrease of cell density (1.6%), while the group of patients that had microperforations showed a large decrease of cell density (14.3%). The cell perimeter and side lengths showed a similar pattern. The group of corneas with the optical zone diameter less than 3.5 nun showed a decrease in mean cell density from 2,994 to 2,725 cells/mm2, and the cell shape changed from 0.874 to 0.866 following surgery. The changes in these parameters were statistically significant (P < 0.05) before and after surgery. Among all factors associated with radial keratotomy, microperforation and a small diameter of central optical zone appear to be the two greatest risk factors.

Radial keratotomy: Analysis of efficacy and predictability in 1,058 consecutive cases Part II: Predictability

Effectiveness and predictability of anterior radial keratotomy to correct myopia and/or astigmatism were evaluated in 1,058 consecutive surgeries. The surgical technique, results, and comparison to other series are detailed in Part I. In this paper, a retrospective study for predicting the change in refraction of eyes having radial keratotomy with and without astigmatism incisions, statistically derived predictors accounted for 72.9% of the variations in outcome.

Ptosis Following Radial Keratotomy: Performed Using a Rigid Eyelid Speculum

Seven patients with acquired ptosis and normal levator function following anterior radial keratotomy are presented. Five of these patients then elected to undergo radial keratotomy of the opposite eye, and four had symmetrical lid fissures (mild bilateral ptosis) after bilateral surgery. Ptosis is a wellknown complication of cataract extraction, but has not been reported following radial keratotomy. Unlike cataract extraction, radial keratotomy does not require anesthetic injections, bridle sutures, or conjunctival flaps. The rigid Knapp eyelid speculum used in these cases remains as the only apparent cause of eyelid trauma and subsequent ptosis. During radial keratotomy, the speculum was opened widely in order to provide good corneal exposure and avoid contact with the diamond knife. Contraction of the orbicularis oculi muscle against the rigid speculum may have traumatized the lid, resulting in a levator aponeurosis disinsertion and subsequent ptosis.