Irregular astigmatism induced by annular tinted contact lenses

Three patients developed irregular corneal astigmatism while wearing annular tinted soft contact lenses on a daily basis for 1.5 to 3 years. There was severe keratometer mire distortion, and photokeratoscopy revealed central and midperipheral corneal topographical irregularities in four of six eyes. In a masked protocol, scanning electron microscopy of four contact lenses revealed physical deformations in three lenses worn on affected eyes. We propose that latent stress vectors were created when the affected contact lenses were tinted. With patient usage, the stress vectors matured into physical deformations that induced irregular astigmatism. The astigmatism resolved upon discontinuing wear of these lenses, and the patients were able to wear other lenses with no recurrence of symptoms.     

The PALM Technique as an Alternative to Customized Ablations

The photoablatable lenticular modulator (PALM) technique is a method developed at the University of Crete for the correction of corneal surface irregularities. The PALM technique refers to corneal excimer laser phototherapeutic keratectomy through a gel used as a masking agent. The authors describe the basic principles of the PALM procedure as well as the refractive and visual outcome of selected cases with different types of corneal irregularities treated with this technique     

Soft contact lenses for irregular astigmatism after laser in situ keratomileusis.

PURPOSE: To investigate soft contact lenses for managing irregular astigmatism after laser in situ keratomileusis (LASIK). The prevailing notion has been that soft contacts conform to corneal surface irregularities and have a limited role for managing LASIK-induced irregular astigmatism. METHODS: A 41-year-old man with bilateral central steep islands following LASIK had best spectacle-corrected visual acuity of 20/40(+1) in the right eye and 20/70+2 in the left eye, despite 20/20 acuity in each eye with rigid contact lenses. Three soft lenses made of etafilcon A (58% H2O) in different center thicknesses were placed sequentially on each eye. All lenses were -2.00 D sphere, in the flatter of the two available base curves. With each lens, corneal topography, spherical over-refraction, and the resulting visual acuity were recorded. RESULTS: In all instances, corneal topography showed reduced surface irregularity although at least some irregularity still transmitted through the lenses. Each spherical over-refraction gave better visual acuity than the corresponding best spectacle-corrected visual acuity. The right eye achieved 20/20 with the thickest lens and spherical over-refraction. The left eye achieved 20/25 with the lens of intermediate thickness and spherical overrefraction. The patient reported functional vision and good comfort with these lenses. CONCLUSIONS: Disposable soft contact lenses can modestly mask irregular astigmatism caused by excimer laser ablation.     

Excimer laser versus diamond fraise: equal short-term outcome of corneal smoothing in pterygium operations

BACKGROUND: The treatment of pterygia often results in irregular astigmatism. Corneal smoothing at the end of surgery plays a major role in the development of astigmatism. The aim of our study was to compare the efficiency of corneal smoothing performed by phototherapeutic keratectomy compared with the conventional method performed by a diamond fraise. The effect of postoperative excimer laser smoothing on refraction, visual acuity and irregular astigmatism was investigated. PATIENTS AND METHODS: 32 eyes underwent pterygium excision using a standardized surgical procedure. In addition 9 eyes underwent postoperative phototherapeutic keratectomy of the wound region with an excimer laser, 23 eyes were treated with a diamond fraise for corneal smoothing. The postoperative examination was performed 7, 14 and 30 days after surgery. Corneal topography was performed by a computer-assisted videokeratoscope (TMS-1). The results were evaluated by the Fourier transform analysis. RESULTS: Both methods showed similar results concerning refraction and visual acuity postoperatively. Preoperatively all patients had an irregular flattening of the corneal topography in the area of the pterygium. Postoperatively a small irregular flattening was left in eyes treated with a diamond fraise. In the excimer laser treated group a steepening in the corneal topography could be observed. CONCLUSIONS: The phototherapeutic keratectomy with excimer laser in the treatment of pterygia suggests to be a gentle alternative creating a smooth wound surface. Despite of this advantage the treatment with the excimer laser effects a remarkable increase in administration and expense.     

Contact lens fitting after photorefractive keratectomy.

AIMS/BACKGROUND: This study evaluated contact lens fitting and the longer term response of the photorefractive keratectomy (PRK) cornea to lens wear. In PRK for myopia problems such as regression, anterior stromal haze, irregular astigmatism, halo aberration, and anisometropia have been reported. Certain patients therefore require contact lens correction to obtain best corrected visual acuity (BCVA). METHOD: From an original cohort of 80 patients, 15 were dissatisfied with their visual outcome 6 months after PRK. Ten of these were fitted with lenses and monitored regularly. RESULTS: The best fit rigid gas permeable lens of diameter 9.20-10.00 mm was generally 0.10 mm steeper than mean keratometry readings. Because of lid discomfort five patients were refitted with daily wear soft lenses. All 10 achieved satisfactory lens wear of 10 hours per day. Central corneal steepening of 0.75 D (0.15 mm) occurred in one patient. Two patients had slight central corneal flattening. Three patients discontinued lens wear as they found lens care a nuisance. Four finally opted for retreatment by PRK. CONCLUSIONS: In most cases, contact lenses gave good visual acuity and, in cases of mild irregular astigmatism, a significant improvement over spectacle BCVA. No significant adverse reaction to contact lens wear was found. Although ocular tolerance of lenses was satisfactory, several patients discontinued lens wear or sought improved unaided vision.     

Superficial keratectomy with the 193 nm excimer laser: a reproducible model of corneal surface irregularities.

Rough corneal surfaces may be smoothed by performing a superficial keratectomy with the 193 nm excimer laser. In order to smooth an irregular surface, a substance must be used during ablation to protect low corneal areas so that high spots are ablated preferentially. A simple, accurate, and reproducible method for modelling various corneal surface irregularities was developed. The technique uses the excimer laser to imprint the patterns of various metallic grids onto the stromal surface. The model was used to facilitate a comparison of three potential smoothing agents: 0.5% tetracaine, 2% hydroxypropylmethylcellulose, and a fluorescein-containing hyaluronate preparation. Preliminary results indicate that tetracaine may be the most efficacious smoothing agent.     

New generation of excimer laser--Asclepion Meditec MEL 70 G-Scan

The new Asclepion-Meditec MEL 70 G-Scan represents a breakthrough in surgical application of excimer laser. The laser uses the latest generation of flying spot system which utilizes a SafeScan algorithm (patent pending) to avoid corneal surface irregularities. The system utilizes a Gaussian beam profile. In cases where the cornea has regular surface, the conventional excimer laser PRK or LASIK method will provide good results. If the cornea shows an irregular surface shape, custom-tailored, topography-based ablation, which has been adapted to the corneal irregularity, should provide better results. Asclepion-Meditec have added a TSA (Tissue saving Algorithm) module to TOSCA (Topography Supported Customized Ablations) software for carrying out topography-guided corrections. This module automatically minimises the tissue removal when calculating the correction program. MEL 70 G-Scan allows to treat all forms of refractive errors, myopia and myopic astigmatism -24 D sph, -12 D cyl, hyperopia and hyperopic astigmatism +16 D sph, +8 D cyl, mixtus and irregular astigmatism.     

Comparison of changes in manifest refraction and corneal power after photorefractive keratectomy

PURPOSE: To determine which corneal curvature values most closely correlate to change in manifest refraction after excimer laser photorefractive keratectomy. METHODS: In a prospective study at the Cullen Eye Institute, excimer laser photorefractive keratectomy was performed on 27 eyes of 27 patients (mean age, 38.07+/-6.65 years). Preoperative refractive errors ranged from -2.25 diopters to -8.75 diopters (mean, -5.74+/-2.09 diopters). Preoperatively and 1 month postoperatively, we determined the spherical equivalent of the subjective manifest refraction (corrected for a 12-mm vertex distance) and measured corneal power using standard keratometry (Bausch & Lomb Keratometer; Rochester, New York) and computerized videokeratography (EyeSys Corneal Analysis System; Premier Laser Systems Inc, Houston, Texas). We collected 15 corneal values: standard keratometry and 14 computerized videokeratography values calculated using the axial, instantaneous, and refractive formulas. All calculations were performed with 1.3375 and 1.376 for the refractive index of the cornea. For each of the corneal values, we subtracted the change in corneal power from the change in manifest refraction and calculated for this difference the means, SDs, correlations, and regressions. RESULTS: Mean differences between change in refraction and change in corneal power were lower when for a refractive index of 1.376 than for 1.3375, were lowest for the most central measurement points, and displayed a high SD. A value of 1.408 for the refractive index would be required to optimize the correlation between change in manifest refraction and effective refractive power of the central 3 mm of the cornea. CONCLUSIONS: For individual patients who have undergone photorefractive keratectomy, changes in corneal values determined by computerized videokeratography or by standard keratometry do not reliably predict change in manifest refraction.     

Astigmatism in corneal graft. Prevention and treatment

The tremendous development of the photokeratoscope and corneal topography analysis explains the development of corneal astigmatism study in corneal graft. Our study consists in a review of the bibliography. The prevention of the astigmatism needs the following: before the trephination, the astigmatism has to be treated (correction of against the rule astigmatism which is usual in the aphake people); during the trephination, to minimize the deformation of the eye ball, to choose a good diameter for the keratoconus case, to use a pneumatic trephine in order to have a perpendicular cut (the use of the laser Excimer seams promising); The suture of the corneal graft can be done with a double running suture 10/0 and 11/0. The 10/0 is removed at the third month, the visual recovery is faster but the average astigmatism is not as good as with the interrupted 10/0 sutures and running suture 11/0. This technique is good for an old patient or a one eyed people specially interested in a faster recovery of visual acuity. The second possibility is to use 16 interrupted sutures with and 11/0 running suture. With this technique, the sutures are removed selectively depending on the keratometry and the photokeratoscopy. The visual recovery is longer but the astigmatism at the end is very low. When all the sutures have been removed, the residual astigmatism can be treated when there is not any misalignement between the cornea and the graft. The keratometry, photokeratoscopy allows to find the meridian which is abnormal and to find out if the astigmatism is symmetrical or asymmetrical. The astigmatism is symmetrical if the deformation is the same at either side of the meridian. When the abnormal meridian is the steepest, the only thing to do is a relaxing incision (one or two if is asymmetric, two if the astigmatism is symmetric). The size of the relaxing incision is determined by the photokeratoscopy and the deepness by the effect obtained during surgery looking at a qualitative keratometer. On the table, the effect must be about 50% of over correction. When, the abnormal meridian is the flattest, the only thing to do is a wedge resection (if the astigmatism is asymmetric) or two wedge resections (if the astigmatism is symmetric). The size of the cuneiform resection is choosen with photokeratoscopy. The study of the literature about the Ruiz incision adapted to corneal graft cannot nowadays conclude to the accuracy and safety of this technique.(ABSTRACT TRUNCATED AT 400 WORDS)     

Transepithelial photorefractive keratectomy for treatment of thin flaps or caps after complicated laser in situ keratomileusis

PURPOSE: To report transepithelial photorefractive keratectomy treatment of corneal irregularities produced during laser in situ keratomileusis (LASIK) in which there is a thin flap or cap associated with central corneal scarring or epithelial ingrowth that threatens vision.METHODS: Case reports. The thickness of the abnormal corneal flap or cap and associated scarring or epithelial ingrowth is estimated at the slit lamp or measured with an optical pachymeter. If residual myopia is sufficiently high to allow complete ablation of the flap or cap in the central cornea, a transepithelial photorefractive keratectomy is performed in which the epithelium is completely ablated with the excimer laser in phototherapeutic keratectomy mode; residual myopia is corrected using photorefractive keratectomy.RESULTS: This method was used successfully in two eyes of two patients in which a thin cap was associated with a transverse cut through the central cornea or a donut-shaped flap associated with epithelial ingrowth in the central cornea. In both cases, the abnormal cap or flap was ablated, central corneal clarity restored, and visual function improved.CONCLUSION: Transepithelial photorefractive keratectomy may be effective in treating central corneal thin cap or flap abnormalities associated with LASIK.     

Limitations of erbium:YAG laser photorefractive keratectomy

PURPOSE: The erbium:YAG laser (lambda = 2.94 microm) has been considered promising as an alternative to the ArF excimer laser in photorefractive keratectomy (PRK). However, corneal application of this mid-infrared solid state laser is still plagued with various disadvantages compared to that of the ArF excimer laser (lambda = 193 nm). We discuss the limitations of PRK with the erbium:YAG laser. METHODS: Measurements of ablation threshold, ablation efficiency, and thermal damage were done to compare the process of erbium:YAG laser photoevaporization to the ArF excimer laser. PRK procedures were performed on fresh enucleated pig corneas to investigate the morphology and surface roughness of the cornea after scanning-spot and fundamental mode photoablation. Surface roughness was measured by using a tactile surface reprofiling system. RESULTS: The ablation threshold and the ablation efficiencies for the erbium:YAG laser are significantly higher compared to the ArF excimer laser. Collateral thermal damage decreases with a reduction of laser pulse duration to a minimum of approximately 5 microm. Scanning electron microscopy and surface roughness measurements of the corneal surface after erbium:YAG laser treatment demonstrated higher surface roughness compared to ArF excimer laser treatments. CONCLUSIONS: The erbium:YAG laser is not at present an alternative to the ArF excimer laser for photorefractive keratectomy.     

Regression and epithelial hyperplasia after myopic photorefractive keratectomy in a human cornea.

We present the histology of a cornea of a woman who had excimer laser photorefractive keratectomy (PRK) for myopia 6 months before she died in an accident. Preoperative spherical refraction was -6.00 diopters (D) with an astigmatism of -0.50 D. Six months postoperatively, refraction was -4.50 D. Slight corneal haze was noted at 1 and 3 months. The corneal histology showed marked epithelial hyperplasia in the center of the ablation zone without subepithelial deposition of newly synthesized collagen, proteoglycans, or both. The epithelial thickness was 38 microns in the untreated area and 93 microns in the center of the ablation. In conclusion, postoperative epithelial hyperplasia was responsible for regression after PRK in this eye.     

Contact lens fitting difficulties following refractive surgery for high myopia.

PURPOSE: To describe the clinical and optical problems encountered in contact lens fitting following refractive surgery for high myopia. METHODS: Following refractive surgery for high myopia (greater than -10.00 D) we corrected residual refractive errors with contact lenses in the four eyes of two patients. The first patient had undergone bilateral laser in situ keratomileusis (LASIK),with two subsequent LASIK retreatments in the left eye. Ten months later she was fit with rigid gas permeable (RGP) lenses in both eyes. The second patient had undergone a clear lens extraction in the right eye and radial keratotomy followed by photorefractive keratectomy(PRK) in the left eye. She was fit with toric soft lenses six years postoperatively. RESULTS: Final visual acuity obtained with contact lenses was 20/25-20/20 in all eyes. The first patient required significant minus lens power compensation. Furthermore, the RGP lens in the left eye was slightly decentered due to corneal irregularity induced by LASIK. The second patient had regular corneal surfaces and was successfully fit with daily wear toric soft lenses despite the 2.75 D of residual astigmatism in the left eye. CONCLUSIONS: Following refractive surgery for high myopia a proportion of patients will remain undercorrected. In these patients the alterations in corneal architecture that ensue make contact lens fitting more challenging. Patients with regular astigmatism may be fitted successfully with toric soft lenses. Patients with corneal irregularities should be fit with RGP lenses.     

准分子激光术后超微结构变化与生物组织反应

目的 以超微结构为基础,了解准分子激光表面切削术后角膜生物组织反应特点。方法 透射电镜对38只兔眼4,8,12周角膜组织进行观察和分析,并设对照。结果 角膜基质细胞线粒体和粗面内质网损害;出现功能不良性角膜实质细胞;在各种细胞中有成堆的骶鳞体积聚,提示大量自由基的产生;免疫细胞反应和淋巴细胞的凋亡;气化性碎屑产生;角膜胶原纤维区域性溶解等。结论 准分子激光可使角膜组织产生特异性的生物组织反应,可能是临床合并症的组织病理学基础。     

New lamellar keratoplasty techniques: posterior keratoplasty and deep lamellar keratoplasty

Posterior keratoplasty is a new surgical technique that may be valuable in treating patients with corneal decompensation secondary to endothelial dysfunction. There are currently two approaches to posterior keratoplasty. In the first approach, a corneal flap is created using a microkeratome (similar to laser in situ keratomileusis flap), and posterior stromal tissue is excised (by trephination or excimer laser keratectomy). In the second approach, a deep stromal pocket is created across the cornea through a superior scleral incision. A custom-made flat trephine is inserted into the pocket to excise a posterior lamellar disc. Preliminary studies have shown the feasibility of performing these techniques in sighted human eyes. Despite potential advantages, further clinical studies are needed to determine whether these techniques reduce interface scarring, astigmatism and graft rejection, improve visual outcomes, or are potentially an alternative for penetrating keratoplasty.     

Correlation among refractive, keratometric and topographic astigmatism after myopic photorefractive keratectomy

BACKGROUND: Photorefrative keratectomy can be used to flatten the curvature of the anterior cornea and reduce the myopic refraction of the eye. This leads to unphysiological topographical changes of the cornea and may alter the conditions for examinations of corneal surface topography. The purpose of this study was to check for mutual agreement of three different methods of assessment of astigmatism before and after myopic photorefractive keratectomy (PRK). PATIENTS AND METHODS: Forty-seven eyes of 28 patients (age 32.7+/-6.6 years) following PRK using an 193-nm excimer laser were included in this study. 37 eyes were treated for pure myopia (-4.9+/-2.4 D) and 10 eyes for myopic astigmatism (sphere -2.0 to -7.0 D, cylinder -1.0 to -3.0 D). Preoperatively and at 18 months postoperatively, subjective refractometry, keratometry and topography analysis were performed. The axes of topographic and keratometric cylinder were standardized periodically (180 degrees) with respect to the refractive cylinder axis. RESULTS: Pre- and postoperatively, the absolute astigmatism values correlated highly significantly between all three methods (P< or =0.001). The mean refractive cylinder was 0.65+/-0.61 D preoperatively and 0.46+/-0.41 D postoperatively (P=0.2). The mean keratometric astigmatism was 1.14+/-0.64 D before and 0.94+/-0.50 D after PRK treatment (P=0.2). Among the three methods, the mean topographic astigmatism was the highest (P<0.001) preoperatively (1.31+/-0.56 D) and postoperatively (1.21+/-0.52 D) (P=0.3). In eyes treated for pure myopia, no difference between pre- and postoperative refractive, keratometric and topographic astigmatism was detected (P>0.5). The axes of both topographic and keratometric astigmatism correlated highly significantly with the refractive cylinder axis (R> or =30.9, P<0.0001). CONCLUSION: Up to 2 years after myopic PRK, the difference between refractive and keratometric astigmatism does not differ from the preoperative value, indicating an even corneal surface. The absolute astigmatism values and the cylinder axis correlated well between subjective and objective methods of astigmatism assessment. Thus, objective measurements may be helpful in determining the cylinder component of best spectacle correction after PRK. However, topographic analysis overestimates astigmatism values systematically before and after PRK.     

Impact of phototherapeutic keratectomy on the outcome of subsequent penetrating keratoplasty in patients with stromal corneal dystrophies

PURPOSE: To examine the impact of previous phototherapeutic keratectomy (PTK) on the outcome of subsequent penetrating keratoplasty (PK) in patients with stromal corneal dystrophies. DESIGN: Retrospective, cross-sectional, clinical single-center study. METHODS: Patient Population: Fifteen patients (21 eyes) age 39.9 +/- 11.4 years. Inclusion Criteria: Primary homologous PK performed in phakic patients with granular or macular dystrophy; no use of combined surgical procedures; defined graft size and technique. The study group comprised eight eyes of five patients, PK performed 3.7 +/- 2.3 years after PTK. The control group (no previous PTK) comprised 13 eyes of 10 patients. In both groups, 38% had granular and 62% had macular dystrophy. Intervention Procedures: Phototherapeutic keratectomy was performed using a 193 nm excimer laser. All PKs were also performed using this laser, with trephination using a metal mask. Subjective refractometry (trial lenses), standard keratometry (Zeiss ophthalmometer), and corneal topography (Tomey TMS-1) were performed preoperatively, 6 months after PK, and after first and second suture removal (1.1 +/- 0.2 years; 1.6 +/- 0.2 years). Main Outcome Measures: Keratometric, topographic net astigmatism, and refractive cylinder; keratometric and topographic central power; best-corrected visual acuity (BCVA); surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA). RESULTS: Refractive power and astigmatism, BCVA, and PVA values did not differ significantly between the two groups at any time-point; SRI tended to be better in the study group after first suture removal (P =.05). CONCLUSION: Preceding PTK does not appear to impair the outcome of subsequent penetrating keratoplasty in stromal corneal dystrophy patients.     

Treatment of corneal surface irregularities using biomask as an adjunct to excimer laser phototherapeutic keratectomy.

PURPOSE: To assess the clinical changes induced by the use of BioMask as an adjunct to phototherapeutic keratectomy (PTK) using the excimer laser. METHODS: A nonrandomized, prospective clinical trial was conducted. Twenty-two consecutive patients were enrolled for BioMask treatment with reduced visual acuity caused by irregular astigmatism or corneal scarring. Patients were treated with a broad-beam excimer laser using the standard PTK mode. The BioMask collagen material was applied as a liquid at 47 degrees C and molded using custom-made, rigid, gas-permeable contact lenses. After allowing the material to cool for approximately 3 minutes, the lens was removed and the gel was ablated at a fluence of 130-140 mJ/cm2 at a frequency of 10 Hz, until the stromal bed appeared smooth. After surgery, patients were followed at day 1, week 1, and months 1, 3, 6, 9, and 12. The main outcome measures were best spectacle-corrected visual acuity (BSCVA) and uncorrected visual acuity (UVA). RESULTS: Comparison of the preoperative and postoperative BSCVAs showed a statistically significant change in vision (p = 0.0356). Before surgery, the mean Snellen BSCVA was 20/90, whereas after surgery, BSCVA increased to 20/60. Sixty-five percent of the patients had an improved BSCVA, with an average gain of 3.7 lines per patient (range, +2 to +10). Fifteen percent of the patients lost an average of 3.0 lines (range, -2 to -6), and 20% had no change. UVA averaged 20/180 before surgery and 20/123 after surgery, but the change was not statistically significant. With respect to UVA, 63% improved by an average of 4.25 lines per patient (range, +2 to +9). Twenty-six percent (26%) lost an average of 5.6 lines (range, -2 to -8), and 10% had no change. The average follow-up time was 8 months for both BSCVA and UVA. When patients were stratified by their treatment indications and ranked in order of BSCVA outcome, patients with Salzmann's nodular degeneration did the best, followed by those with prior refractive surgery, corneal dystrophies, and corneal scars. Even though BSCVA did not improve as much in the corneal scar group, 50% of the patients reported an improvement in the symptoms they experienced before surgery based on questionnaires. Conclusion. BioMask appears to have potential as an ablatable mask material when used in conjunction with PTK for the treatment of corneal surface irregularities.     

Selective zonal ablations with excimer laser for correction of irregular astigmatism induced by refractive surgery

OBJECTIVE: To demonstrate the safety and efficacy of selective zonal ablations with excimer laser for the correction of irregular astigmatism induced by refractive surgery. DESIGN: Thirty-one eyes of 26 patients. Retrospective and noncomparative case series. METHODS: The authors reviewed the medical results of the two series of consecutive cases of irregular astigmatism induced by refractive surgery. One group showed a topography map with a defined pattern: decentered ablation, decentered steep central island, central irregularity, and peripheral irregularity. The other group showed an irregular astigmatism without defined pattern. Selective zonal ablation was performed with a broad-beam excimer laser. Laser ablations were adjusted according to the Munnerlyn formula. A phototherapeutic keratectomy (PTK) mode was used in all cases without using viscous masking solution. MAIN OUTCOME MEASURES: Uncorrected visual acuity, best spectacle-corrected visual acuity (BCVA), and Holladay diagnostic summary (Eye Sys 2.000) were considered before and after surgery to obtain the qualitative and quantitative characteristics of the visual acuity and corneal topography. The corneal uniformity index (CUI) was used to evaluate the corneal surface changes induced by the selective zonal ablations in the correction of irregular astigmatism. It proved to be a useful tool in the understanding of astigmatic changes when it is not possible to apply the vector analysis. RESULTS: In group 1, the irregular astigmatism was significantly improved in 96.4% of cases. The CUI was improved from 58+/-0.3% to 87+/-0.8%, P < 0.005 (Student's t-test). The improvement of the BCVA was from 20/40+/-20/100 to 20/25+/-20/100, P < 0.005 (Student's t-test). The results obtained in group 2 were not clinically significant in terms of improvement of CUI and BCVA. CONCLUSIONS: Using the corneal topographic map as a guide, selective zonal ablations with excimer laser can be used to create a more regular corneal surface, when a defined pattern of topographic irregularities can be defined.     

Two cases of Terrien's marginal degeneration treated with peripheral full thickness keratectomy,and followed-up by computer-assisted corneal topography

BACKGROUND: In 1970 Alberth and Süveges published a method, peripheral full thickness keratectomy, for the treatment of Terrien's marginal degeneration of the cornea. They hypothesized that this type of surgery acts by excising the thinned and extended corneal parts and by restoring normal corneal surface and curvature. METHOD: The right eyes of two patients with Terrien's disease were operated with full thickness keratectomy at our Department, and were followed-up by computer-assisted computer topography. RESULTS: The corneal surface became more regular, astigmatism smaller and fully correctable, visual acuity improved, and the results did not change between 1 and 3 years after surgery in either of the two cases. CONCLUSION: Peripheral full thickness keratectomy, in our experience, proved effective in reducing astigmatism, in improving visual acuity, and in stopping the progression of the disease. Corneal topography can be used in the diagnosis of Terrien's disease, as well as in the postoperative follow-up of patients, giving more information than simple keratometry.