[Acute vision loss after intraocular foreign body injury 20 years ago].
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Acute Disease↗
Biomedical subjects
A Viestenz
Publications and source records attributed to A Viestenz.
[Impact of the eye's cyclorotation on axial orientation analysis of toric intraocular lenses: recommendations for an optimized evaluation of rotational stability of toric IOLs].
BACKGROUND: After the implantation of toric intraocular lenses (tIOLs) significant postoperative tIOL rotation angles were measured occasionally. We investigated the rotational stability of eyes during standardized photography and recommend two methods for an enhanced evaluation of tIOL rotation. PATIENTS AND METHODS: 1. The cyclorotation of the eye was investigated using standard fundus photography. A sequence of two fundus photographic slides was taken in 550 phakic eyes of 275 consecutive patients with a time interval of at least 6 months. With characteristic markers on the fundus photograph, the axial orientation of the eyes was defined and the cyclorotation between the two slides of each eye was measured. 2. Using bifocal photography (HRA II - Heidelberg Retina Angiograph), a sequence of anterior segment and fundus images was taken considering stable head position in 19 pairs of photographs of eyes with implanted tIOLs. The angle between reference fundus axis and tIOL axis was measured at both time stages (mean: after 3 months). The difference of the angle between bifocal-image samples was defined as the real tIOL rotation angle. 3. Ten pairs of anterior segment photographs of eyes with a tIOL were investigated using the Axenfeld loop analysis. In each photograph, the angle between the axis connecting two Axenfeld loops and the tIOL axis was measured. The difference of two angles of two photographs was defined as the rotational tIOL angle. RESULTS: 1. The mean absolute eye's rotation angle was 2.3 +/- 1.7 degrees (range: 0 to 11.5 degrees) in all 550 eyes. Only 9.1 % of the eyes did not rotate. In 57.3 % of the eyes a rotation of less than 3 degrees and in 33.6 % of more than or equal to 3 degrees was detected. The eye's cyclorotation correlated (p < 0.04) with an age older than 39 years and higher astigmatism (> 1.5 D). Because of the significant amount of spontaneous globe rotation we developed the following enhanced methods to minimize measurement errors of tIOL rotation: 2. Bifocal photography: comparing the 19 HRA anterior segment images, the amount of mean tIOL rotation was 5.4 +/- 4.8 degrees (range: 0 - 20.0 degrees). Using the bifocal photography, the mean tIOL rotation was 1.9 +/- 1.3 degrees (range: 0 - 5.0 degrees). The overestimated rotation of the tIOL (only anterior segment tIOL comparison) correlated with higher amounts of the eye's cyclorotation (r = 0.94; p = 0.01) and higher corneal astigmatism (r = 0.54; p = 0.05). 3. The simultaneous analysis of Axenfeld loops revealed significantly smaller amounts of tIOL rotation (2.3 +/- 2.5 degrees range: 0 - 7.0 degrees ) in 10 pairs of anterior segment photographs in contrast to the single analysis of tIOL axis (5.5 +/- 4.8 degrees range: 1 - 13.0 degrees p = 0.09). A reduction of up to 18.0 degrees tIOL rotation measurement failure was possible in single cases by applying the bifocal photography or simultaneous Axenfeld loop analysis. CONCLUSIONS: Head inclination, head rotation, and incyclo- or excyclorotation of the eye may have a significant impact on the tIOL axis evaluation. Besides the bifocal photography the simultaneous Axenfeld loop analysis could be a promising alternative to the conventional axis evaluation of tIOLs.
Artifacts↗
[Healthy optic discs with large cups--a diagnostic challenge in glaucoma].
BACKGROUND: Healthy optic discs with large cups are often characterised to be glaucomatous in automated, morphometric analysis. The aim of this study was to investigate the variables of laser scanning tomography (LST) and nerve fibre polarimetry of these disks in comparison to small and normal sized disks. METHODS: 117 eyes (age 49.3 +/- 14.6 years) with healthy, non-atrophic disks (md = 0.8 dB, Tensio 14.3 +/- 2.5 mmHg) of the Erlangen Glaucoma Registry were clinically examined. Morphometry was performed both by planimetry and the HRT I (Heidelberg Engineering, Dossenheim, version 2.01) and with the GDx FCC (Laser Diagnostics, San Diego). 63 eyes initially referred for a large cup were compared to 54 normal eyes. All measurements were analysed globally and in four sectors according to Jonas. RESULTS: The disc area of discs with large cups was significantly larger than that for the normals (3.1 +/- 5.3 vs. 2.2 +/- 4.2 mm (2)). Both the multivariate analysis of the HRT and the GDx revealed a significant correlation with total disk area (R = 0.34, p = 0.0001), with a high percentage of false positive glaucoma eyes among large disks. Cup area and volume showed, in contrast to rim volume and rim area, a significant correlation (R = 0.76, p = 0.0001) with the disc size. Thickness of retinal nerve fibre layer measurements both in HRT and GDx showed higher values for larger disc size with steeper cup measurements. The vertical diameter of the cup increased in comparison to the horizontal to a higher extent with increasing disc size. CONCLUSIONS: By the pronounced enlargement of cup measurements, decreasing nerve fibre thickness values and decreasing ratio of temporal-to-inferior width of the neuroretinal rim, large disks may easily be detected as false glaucomatous by morphometric analysis systems. A better presentation of large discs in a normative database and integration of sectors and disc area in a multivariate analysis may improve the diagnostic abilities of automated morphometric disk analysis.
Diagnosis, Differential↗
[Parapapillary autofluorescence as indicator for glaucoma].
BACKGROUND: A pronounced fundus autofluorescence (lipofuscin) occurs in eyes with AMD. Parapapillary lipofuscin accumulation in the retinal pigment epithelial cells was observed in eyes with advanced glaucoma histologically. The aim of this study was to evaluate the parapapillary autofluorescence (PAF) in vivo in healthy eyes (controls), and in eyes with primary open angle glaucoma (POAG), pseudoexfoliation glaucoma (PSXG) or normal tension glaucoma (NTG). PATIENTS AND METHODS: Controlled cross-sectional analysis was performed on 281 consecutive eyes (98 controls, 95 POAG, 32 PSXG, 56 NTG). Eyes with fundus pathologies were excluded. The confocal scanning laser ophthalmoscope HRA II (Heidelberg Retina Angiograph II) was used after lipofuscin-excitation with an argon blue laser (488 nm) to detect PAF in the spectrum above 500 nm. PAF area and PAF distance to the optic nerve head were analyzed using the HRA standard software. Two experienced ophthalmologists classified independently the stage of glaucomatous optic nerve head atrophy (GONHA) using 15 degrees fundus photographs. RESULTS: Vital optic nerve heads had smaller PAF areas (stage 0: 0.07 +/- 0.09 mm (2)) in contrast to advanced stages of GONHA (stages 1 to 4: 0.27 +/- 0.46 mm (2); p < 0.001; logistic regression Cox and Snell: r = 0.7; p = 0.015). The PAF distance to the optic nerve head was lower in controls (0.12 +/- 0.08 mm) than in eyes with POAG, PSXG, or NTG (0.25 +/- 0.21 mm, Bonferroni: p < 0,004). The PAF area correlated significantly with the stage of GONHA (stage 1: 0.23 +/- 0.23 mm (2), stage 2: 0.24 +/- 0.19 mm (2), stages 3 and 4: 0.34 +/- 0.73 mm (2), p < 0.01). No significant difference of PAF area was found between the glaucoma types. However, the distance between PAF and optic nerve head was higher in POAG (0.28 +/- 0.26 mm) than in NTG (0.24 +/- 0.07 mm) or in PSXG (0.18 +/- 0.07 mm, Bonferroni: p < 0.03). CONCLUSIONS: A pronounced fundus autofluorescence was detected as a sign of increased lipofuscin accumulation in the parapapillary atrophic zone of eyes with POAG, PSXG, and NTG in contrast to controls. The PAF analysis may provide an indicator for glaucomas in the future.
Biomarkers↗
[Reproducibility of dynamic contour tonometry. Comparison with TonoPenXL and Goldmann applanation tonometry - a clinical study on 323 normal eyes].
BACKGROUND: The PASCAL Dynamic Contour Tonometer (DCT) is a new diagnostic approach for the digital measurement of intraocular pressure (IOP) in eyes with glaucoma. The aim of this study was to evaluate the reproducibility of DCT in normal eyes and to compare DCT with Goldmann applanation tonometry (GAT) and TonoPenXL. PATIENTS AND METHODS: A prospective cross-sectional study on 323 normal, consecutive eyes was performed. Eyes with an IOP of more than 23 mmHg (GAT) were excluded. Central corneal power (Zeiss Ophthalmometer) and central corneal thickness (ultrasound pachymetry: Tomey AL-1000) were taken. The IOP readings were obtained as follows: 3 x DCT [quality of measurement, IOP and ocular pulse amplitude (OPA) were taken], 1 x TonoPenXL, GAT, finally: once again DCT to evaluate the tonography effect. RESULTS: The quality of 3 following IOP (DCT) readings was good (quality Q1 = 43.4 %, Q2 = 32.5 %, Q3 = 22.7 %). The reproducibility of the IOP (DCT) measurements was excellent (first measurement IOP (DCT) = 18.1 +/- 3.4 mmHg, second measurement IOP (DCT) = 18.1 +/- 3.4 mmHg, third measurement IOP (DCT) = 17.8 +/- 3.4 mmHg, Cronbach's alpha = 0.976). First and second IOP (DCT) values showed a strong correlation (r = 0.93). A significant tonography effect was observed between first and third IOP (DCT) measurements (0.4 mmHg; p = 0.004). Mean OPA (DCT) was 3.0 mmHg during the first three measurements (Cronbach's alpha = 0.964). IOP (DCT) and OPA (DCT) reproducibility showed no laterality. IOP (DCT) (17.7 +/- 3.4 mmHg) was significantly higher than IOP (TonoPenXL) (16.0 +/- 3.2 mmHg, n = 275; p < 0.001) and higher than IOP (GAT) (14.5 +/- 3.1 mmHg, n = 275; p < 0.001). The effect of tonography between the third and last IOP (DCT) measurement was zero (p = 0.6). IOP (DCT) and IOP (GAT) values were only weak correlated with central corneal thickness. CONCLUSIONS: IOP and OPA values measured with the DCT are extraordinary reproducible in normal eyes. Frequently, DCT detects higher IOP values than those obtained with TonoPenXL and GAT. A reproducible measurement of IOP and OPA may open new diagnostic fields, e. g., in glaucoma detection or ocular vascular diseases.
Cross-Over Studies↗
[Toric intraocular lenses for correction of persistent corneal astigmatism after penetrating keratoplasty].
PURPOSE: Cataract extraction with implantation of toric intraocular lenses (tIOL) is a new surgical option for correction of residual astigmatism following penetrating keratoplasty and cataract with only minimal direct manipulation of the graft. PATIENTS AND METHODS: We implanted an individually manufactured backtoric tIOL in 11 eyes of 9 patients. TIOL power calculation was done using vergence transformation in a paraxial space. RESULTS: Implantation and intraoperative alignment of tIOL were uneventful in all patients. Uncorrected visual acuity increased from 0.1+/-0.06 preoperatively to 0.47+/-0.18 (p=0.006) postoperatively. Best-corrected visual acuity changed from 0.23+/-0.18 preoperatively to 0.6+/-0.14 postoperatively (p=0.002). The refractive cylinder could be reduced from 7.0+/-2.6 D to 1.63+/-1.5 D (p=0.001) after surgery. We observed a small mean deviation from the target axis of 4.1+/-2.9 degrees (0-8 degrees ) after a mean follow-up time of 3.5 (2-7) months. CONCLUSION: TIOL implantation is a promising option for correction of high astigmatism following penetrating keratoplasty with only minimal direct surgical manipulation of the graft. Regular and symmetric corneal topography is essential for successful implantation of tIOL.
Aged↗
[Unilateral, segmental corneal decompensation. Suspicion of keratitis herpetica].
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Adult↗
[Blunt ocular trauma. Part II. Blunt posterior segment trauma].
This review presents typical patterns of posterior segment injuries as well as diagnostic and therapeutic considerations after ocular contusion or rupture of the globe. Vitreal prolapse is associated with retinal detachment (20%), iridodialysis or ciliary body cleft (43%), and contusion cataract (41%). Berlin's edema (35%) and retinal detachment (5-7%) are frequent after ocular contusion. In cases of central Berlin's edema, choroidal infarction (Hutchinson-Siegrist-Neubauer syndrome) or choroidal rupture, macular hole or choroidal neovascularization should be ruled out. A central choroidal rupture is often associated with choroidal neovascularization (14-20%). Globe ruptures (5% of blunt injuries) are associated with hyphema grades III and IV (58 vs 5% in ocular contusions). The prognosis of globe ruptures to develop a visual function <20/200 is 51 times more frequent than in eyes with contusion. The risk of trauma-induced globe ruptures is higher in eyes after cataract surgery (27 x) (in females 5 x).
Adult↗
Block-excision of cystic epithelial downgrowth as the treatment of choice.
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Anterior Chamber↗
[Blunt ocular trauma. Part I: blunt anterior segment trauma].
Blunt ocular traumas include contusions and ruptures of the globe--open and closed globe injuries. Characteristic damage results in anterior and posterior segment trauma. Typical patterns of injuries are combinations of (1) hyphema grade II-IV, iris-lens injury, vitreal bleeding--choroidal rupture and increased risk of rebleeding, (2) angle recession >180 degrees--secondary open-angle glaucoma, and (3) vitreal prolapse and lens dislocation-retinal detachment. Patients with blunt eye trauma should be under steady observation by an ophthalmologist to handle late complications.
Adult↗
[Rotational stability of the eye in standard photography].
BACKGROUND: After the implantation of a toric IOL (tIOL), postoperative rotations of more than 30 degrees have been reported. Beyond this scope, we investigated the reproducibility of the eye's orientation (rotation stability) in principle. PATIENTS AND METHODS: The rotational stability of the eye was investigated using standard fundus photographs (telecentric fundus camera, Zeiss, Oberkochen). One hundred eyes of 50 patients (28 females) were photographed in a time interval of more than 6 months twice. With the aid of significant markers on the fundus photograph, the axial position of the eye was defined and the rotational angle between the two slides of one eye was measured. RESULTS: The mean absolute rotational angle was 2.4 +/- 1.7 degrees (range 0 to 7.5 degrees ) in all 100 eyes (2.5 +/- 1.6 degrees right eye, 2.4 +/- 1.7 degrees left eye). Only 6 % of the eyes did not rotate. A range of less than 3 degrees rotation was detected in 52 % of the eyes. A rotation of equal to or more than 3 degrees was noted in 42 %. The patient's age did not influence the amount of globe rotation. In- and excyclorotations showed a coincidental distribution and no side differences. CONCLUSIONS: Seven and a half degrees or 3 degrees tIOL rotation would correspond to a residual astigmatism of 26 % or 10 %. When measuring the marked axis of the tIOL, these results are markedly influenced by head inclination, rotation of the head, incyclorotation or excyclorotation. This is transferable, for example, to autorefractor, corneal topography and sectorial analyses for glaucoma diagnostics.
Eye Movements↗
[Toric intraocular lenses for compensation of corneal astigmatism].
BACKGROUND: Besides arcuate or straight transverse keratotomies, toric intraocular lenses are of increasing popularity to enhance the visual function in cases of lens opacification for the correction of corneal astigmatism and the following ocular surgery such as penetrating keratoplasty. The purpose of this study was to present a generalized scheme for the calculation of toric intraocular lenses and to demonstrate its potential on a clinical example in a step-by-step approach. METHODS: After providing some helpful approximations for the clinicians, i. e., for a conversion of radii differences to corneal astigmatism, the calculation scheme using vergence transformation in a paraxial space and the dualism of the standard and component notation for the description of spherocylindrical vergences and spherocylindrical refractive surfaces is described. RESULTS: In a clinical example, a toric intraocular lens is calculated step-by-step using the above-mentioned calculation scheme. The methodology is designed in a matrix structure for the direct implementation in a computer language. In a second step, a toric lens similar to the calculated lens in the manufacturing grid is selected and inserted with a small angle of rotation from the ideal implantation axis to demonstrate the effect on postoperative refraction. CONCLUSIONS: The calculation scheme allows the determination of toric intraocular lenses with an astigmatic cornea and enables us to achieve a spherocylindrical target refraction with cylinder axis at random. Furthermore, the postoperative refraction at the spectacle or corneal plane can be simulated by inserting any toric intraocular lens oriented in any axis. The concept can be easily generalized to 'thick' toric intraocular lenses if the geometrical data and the refraction index of the material are known.
Astigmatism↗
[Bilateral visual field defects with optic disc drusen and secondary open angle glaucoma with PEX--clinical correlation with the HRA].
BACKGROUND: Arcuate visual field defects are a typical sign of glaucomatous damage. Elevated intraocular pressure in combination with pseudoexfoliation syndrome (PSX) manifests the diagnosis glaucoma. Beyond this state, in microdiscs with optic disc drusen, the exact classification of the visual field defects is crucial. CASE REPORT: A 57-year-old male with pseudoexfoliation glaucoma was referred because of progressive glaucomatous visual field defects. The visual acuity was right 20/40 and left 20/25. Maximum intraocular pressure was 36 mm Hg. A simple optic nerve atrophy was diagnosed superonasally. The optic disc size was OD 2.24 mm(2) and OS 1.89 mm(2) (HRT I). An Ultrasound B-mode scan demonstrated the diagnosis of optic disc drusen. Over a follow-up of 1 year, a growth tendency was observed, especially in the superonasal quadrant. The mulberry-shaped surface of the drusen was visualized with infrared reflection images (HRA II, 830 nm). Confocal scanning laser ophthalmoscopy (HRA II, excitation 488 nm, 500 nm notch filter) showed an increased intrapapapillary autofluorescence (> 50 % papillary area: OD 1.67 mm(2), OS 1.26 mm(2)). This technique could detect drusen in areas that looked normal in classical retinoscopy. CONCLUSION: The differential diagnosis of arcuate scotomas includes simple optic nerve atrophy and glaucomatous optic nerve atrophy. Optic disc drusen in glaucoma eyes can obscure the main cause of progressive visual field loss. Superficial optic disc drusen can be measured planimetrically over the years. An adequate reduction of intraocular pressure should be realized in these eyes.
Diagnosis, Differential↗
[Rupture of the choroid after eyeball contusion--an analysis based on the Erlangen Ocular Contusion Registry (EOCR)].
BACKGROUND: Ocular injuries may lead to severe damage of the posterior segment with manifest visual impairment. Choroidal ruptures are frequently masked by acute subretinal haemorrhage. We analysed possible predictive factors and functional results of eyeballs with rupture of the choroid after ocular contusion. PATIENTS AND METHODS: We performed a retrospective study of 376 consecutive inpatients (Erlangen Ocular Contusion Registry - EOCR, over a 10-year period), who were treated because of a blunt eye injury at our eye hospital (86 % males). Detailed notes regarding the anterior and posterior segments were extracted from the standardised charts. Mean age was 28.8 +/- 16.1 years (4 to 84 years). Eyes with previous trauma or globe ruptures were excluded. RESULTS: Twenty-six of 376 patients developed choroidal rupture due to ocular contusion (6.9 %). A choroidal rupture was more frequent in females (9.4 %) than in males (6.5 %). Patients with choroidal rupture were treated as inpatients 5 days longer than patients without (10.7 vs. 5.5 days; p < 0.001). Twenty-two percent of the injuries occurred during work time. Main causes of choroidal ruptures were water jet (19 %), fireworks (12 %), elastic cords (12 %), metal pieces (12 %), gotcha (8 %) and champagne corks (8 %). The risk for developing a choroidal rupture due to water jet or fireworks injuries was increased 9 or 4 times. Ninety-two percent of choroidal ruptures were located at the posterior pole and concentric, 40 % were submacular, 12 % outside the large temporal vessels (4 % were located both centrally and peripherally). Initial visual acuity (VA) and VA at discharge were decreased significantly in eyes with rupture of the choroid (20/200 and 20/60) in contrast to eyes without (20/40 and 20/25; p < 0.001). Choroidal ruptures were often associated with iridodialysis, lens dislocation and contusion cataract (3 x ), vitreous haemorrhage (4 x ), complete retinal defects (6 x ), ciliary body clefts (7 x ) or hyphema rebleeding (4 x ). No association between the height of hyphema and choroidal ruptures was found. The predictive level of choroidal ruptures was 40 % in eyes with a combination of lens dislocation, traumatic cataract and vitreous bleeding. The final VA was 20/200 or less in 11 eyes associated with a prevalence of 55 % of ruptures submacularly. In contrast to this, eyes with VA > 20/200 developed 26 % submacular choroidal ruptures. CONCLUSIONS: Additional severe traumatic changes of the anterior and posterior segment were found 2 - 7 times more frequently in eyes with choroidal ruptures compared to eyes without those ruptures. The visual improvement was limited due to submacular ruptures. Frequent ophthalmological controls are recommended to minimise the risk of choroidal neovascularisation in a submacular location.
Age Distribution↗
[Bifocal photography using the HRA -- an optimized method to evaluate tIOL's axial orientation].
BACKGROUND: The assessment of axial orientation of toric IOLs (tIOLs) by monofocal photography can be deteriorated due to intrinsic errors e. g. globe rotation, head inclination or inadequate camera adaption and slide projection. METHOD: In a 67 years old female a tIOL was implanted after penetrating keratoplasty for correction of high corneal astigmatism. A sequence of two fundus and two tIOL photographs (bifocal photography) was taken in a time interval of 3 months using the HRA II (Heidelberg Retina Angiograph II). A reference at the fundus was defined using two characteristic markers. The axial fundus orientation between the markers was overlaid to the line defined by the tIOL axis markers. The angular offset/distance between the fundus orientation line and the tIOL marker line was analyzed for each bifocal image at different time points. RESULTS: The comparison of axial tIOL orientation between both different tIOL images revealed a rotation angle of 13 degrees (monofocal photograph). In contrast, using the bifocal photography and digital overlay technique the fundus line as a reference the tIOL rotated 1 degrees and 4 degrees from the first to the second time point of photography. Thus, the real rotation angle of tIOL measured only 3 degrees. CONCLUSION: The bifocal photography with constant head position has the potential to minimize the intrinsic error in documentation of axial orientation of tIOL.
Aged↗
[Impact of prostaglandin-F(2alpha)-analogues and carbonic anhydrase inhibitors on central corneal thickness -- a cross-sectional study on 403 eyes].
BACKGROUND: Histological changes of, in particular, collagen and extracellular matrix after administration of topical prostaglandin F(2alpha)(PGF (2alpha)) analogues have been reported. In view of this observation, we investigated the influence of PGF(2alpha) analogues on the central corneal thickness. PATIENTS AND METHODS: In a non-randomized, controlled, cross-sectional study, 403 eyes from 208 consecutive patients were examined: 149 eyes (normals/controls) and 79 with ocular hypertension (OHT), 119 eyes with primary open angle glaucoma (POAG) and 56 eyes with normal tension glaucoma (NTG). One experienced ophthalmologist measured the central corneal thickness (CCT) using ultrasound pachymetry (Tomey AL-2000, sequence of 5 measurements with an SD < 3 microm). The central corneal power was measured with the Zeiss keratometer. Depending on the topical treatment, the patients were classified into 4 groups: A) PGF(2alpha) analogues (n = 78), B) carbonic anhydrase inhibitors (n = 26), C) combination of PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (n = 41), D) none of these drugs (n = 258). T tests and multiple linear regression analyses were used for statistical analysis. RESULTS: CCT was decreased significantly (p < 0.01 each) in eyes treated with PGF(2alpha) analogues (group A: 529 +/- 34 microM), in comparison with the untreated and non-glaucomatous eyes (part of group D: 542 +/- 35 microM, n = 148), untreated glaucomatous/OHT eyes (part of group D: 563 +/- 37 microM, n = 110), eyes treated with carbonic anhydrase inhibitors (group B: 561 +/- 32 microm) and eyes with a topical application of both PGF (2)(alpha) analogues and carbonic anhydrase inhibitors (group C: 555 +/- 48 microM. No correlation was found between CCT and diagnosis (OHT, POAG, NTG, control), gender, central corneal power, and intraocular pressure in a multivariate analysis. CONCLUSIONS: The present findings suggest that the topical application of prostaglandin F(2alpha) analogues onto the cornea reduces the central corneal thickness significantly. These changes might be attributed to effects of PGF(2alpha) analogues on the extracellular matrix of the corneal stroma via upregulation of matrix metalloproteinases. In clinical practice, corneal thinning under local PGF (2)(alpha) analogue treatment could result in underestimation of intraocular pressure levels as measured by applanation tonometry.
Acetazolamide↗
Q-switched erbium:YAG laser corneal trephination: thermal damage in corneal stroma and cut regularity of nonmechanical Q-switched erbium:YAG laser corneal trephination for penetrating keratoplasty.
PURPOSE: To assess stromal thermal damage and cut regularity induced by nonmechanical Q-switched Er:YAG laser corneal trephination for penetrating keratoplasty. METHODS: Corneal trephination was performed in 80 enucleated porcine eyes by Q-switched (2.94-microm) Er:YAG laser, along with donor and recipient masks made of metal or ceramic. All combinations of 0.65- or 0.96-mm spot diameter and 45- or 50-mJ/pulse energy setting were used with each of the masks at a 5-Hz repetition rate. Corneas were processed for histologic examinations. Stromal thermal damage was quantified on PAS-stained slides, and cut regularity was assessed semiquantitatively on a scale from 0 (regular) to 3 (highly irregular). Transmission electron microscopy and scanning electron microscopy were performed on selected specimens. RESULTS: The least thermal damage (mean +/- SD = 6.2 +/- 0.7 microm) was found in the donor ceramic group with 50-mJ/pulse energy and 0.65-mm spot diameter, while the best regularity of the cut (1.2 +/- 0.4) was found in the donor ceramic group with 45-mJ pulse energy and 0.65-mm spot diameter. Thermal damage was less pronounced in donor than in recipient corneas (P < 0.01). Smaller spot diameter (0.65 mm) led to less thermal damage (P < 0.01) than the use of a 0.96-mm spot diameter. The differences in thermal damage between ceramic and metal masks were minimal. CONCLUSIONS: After Q-switched Er:YAG laser corneal trephination for nonmechanical penetrating keratoplasty, reproducible high cut regularity and low concomitant thermal damage were observed. This is an encouraging finding in the search for a nonmechanical trephine for penetrating keratoplasty combining high precision and low cost.
Animals↗