Ildikó Süveges

Scanning laser polarimetry of the retinal nerve fibre layer in primary open angle and capsular glaucoma

AIMS To evaluate the clinical value of scanning laser polarimetry with the nerve fibre analyser type II in primary open angle glaucoma (POAG) and capsular glaucoma. METHODS Scanning laser polarimetry was performed on one eye of 30 patients suffering from POAG, 25 patients suffering from capsular glaucoma, and on 35 healthy control subjects. The retinal nerve fibre layer (RNFL) thickness values were compared among the groups. Reproducibility of the measurements was calculated and the influence of pilocarpine induced miosis on the results was investigated. RESULTS RNFL thickness in the superior and inferior sectors, as well as along the total circumference was significantly lower in both glaucoma groups than in the control eyes (p<0.05). None of the thickness values differed between the two glaucoma groups. Reproducibility was comparable in all groups; the coefficient of variation varied between 3.0% and 8.9% for the different sectors investigated. Miosis had no significant impact either on the thickness values or on the reproducibility (p>0.05). CONCLUSION The results suggest that scanning laser polarimetry is a useful method for nerve fibre layer analysis in glaucoma, and that it is not influenced by the pupil size.

Ultraviolet-B Enhances Corneal Stromal Response to 193-nm Excimer Laser Treatment

PURPOSE The purpose of the study was to evaluate the biomicroscopic, light microscopic, and electron microscopic effects of ultraviolet-B (UV-B) exposure on the outcome of photorefractive keratectomy (PRK). METHODS A total of 24 pigmented rabbits were used in the study. One eye of 16 rabbits received a 193-nm, 45-micron deep (-5.0 diopter) excimer laser PRK. Twenty-one days after PRK, eight of the laser-treated eyes were exposed to 100 mJ/cm2 UV-B (280-315 nm) UV radiation by placing the rabbits in a standard clinically used dermatologic chamber for 7 minutes. Eight PRK-treated rabbits received no further treatment. The remaining eight non-PRK-treated rabbits received 100 mJ/cm2 UV-B only to one eye. Subepithelial haze was assessed before and after UV irradiation. Corneal morphology was assessed 4, 8, 12, and 16 weeks after UV-B exposure, using light microscopic and transmission electron microscopic (TEM) techniques. RESULTS Untreated eyes exposed to 100 mJ/cm2 UV-B only exhibited photokeratitis for 2 days, but showed no haze and were normal histologically at all intervals. The PRK-treated UV-B irradiated eyes exhibited a significant increase of stromal haze compared to eyes receiving PRK alone. Histologically, the main difference between the UV-B irradiated and nonirradiated post-PRK eyes was the presence of anterior stromal extracellular vacuolization in the UV-B-exposed eyes. The vacuolated foci were confined to the PRK treatment area and showed increased keratocyte density and disorganization of normal collagen lamellae. TEM showed activated keratocytes containing abundant rough endoplasmic reticulum, prominent Golgi zones, and extracellular vacuoles filled with amorphous material. The haze and morphologic changes showed a tendency to incomplete resolution over the period of 16 weeks. CONCLUSIONS The UV-B exposure during post-PRK stromal healing exacerbates and prolongs the stromal healing response and is manifest biomicroscopically by augmentation of subepithelial haze. The findings suggest that excessive ocular UV-B exposure should be avoided during the period of post-PRK stromal repair and that UV-B may modulate the response of tissues to 193-nm excimer laser and perhaps other laser energy in general.

Influence of LASIK on scanning laser polarimetric measurement of the retinal nerve fibre layer with fixed angle and customised corneal polarisation compensation

Background/aim: Retinal nerve fibre layer thickness (RNFLT), as measured with scanning laser polarimetry using the fixed angle corneal polarisation compensator (SLP-F), has been found to be reduced after uncomplicated laser assisted in situ keratomileusis (LASIK) compared to the pre-LASIK measurement. Since this virtual RNFLT thinning is attributed to the corneal changes induced by the LASIK, the authors investigated whether customised corneal polarisation compensation (SLP-C), which compensates for the actual corneal polarisation during each measurement, can avoid the LASIK induced, virtual changes of the polarimetric RNFLT values. Methods: Scanning laser polarimetry using both the SLP-F and SLP-C methods (GDx-Access, software version 5.0) was performed on 15 consecutive healthy subjects with no eye disease who underwent LASIK for ametropia correction. The SLP measurements were performed before the surgery, then on day 1 and day 6 after LASIK. Thickness data from images of one randomly selected eye per subject were analysed using the ANOVA and Scheffe multiple comparison tests. Results: Superior maximum, inferior maximum, normalised superior area, and normalised inferior area (SLP parameters representing the RNFLT at the superior and inferior poles of the optic nerve head) remained unchanged with SLP-C (ANOVA, p>0.05) but decreased (superior maximum, normalised superior area, Scheffe test, p<0.05) or tended to decrease (inferior maximum) after LASIK, when measured using SLP-F. In contrast, certain other parameters—namely, superior ratio and inferior ratio (representing the ratios between the superior or the inferior sector and the temporal sector), maximal modulation, and ellipse modulation decreased with SLP-C (Scheffe test, p<0.05), but remained stable with SLP-F (ANOVA, p>0.05) after LASIK. Superior to nasal ratio, symmetry of the superior and inferior RNFLT as well as the parameter showing the probability of having glaucoma (called “the number”) remained unchanged with both types of corneal compensation (ANOVA, p>0.05). With SLP-C the parameter ellipse average thickness increased after LASIK (Scheffe test, p = 0.021). No parameter value altered between day 1 and day 6 after LASIK, for either method. Conclusion: The results suggest that the LASIK induced decrease of the polarimetric RNFLT, which is consistently detected with polarimeters when using the fixed angle corneal polarisation compensator, is due to alterations of the corneal polarisation. The use of customised corneal polarisation compensation avoids this virtual decrease of the polarimetric RNFLTHowever, our results suggestan increase of the measured retardation in the temporal quadrant of the SLP-C image after LASIK. Since ratios of parameters using the temporal RNFLT in the denominator are important in the polarimetric glaucoma diagnosis algorithm, their decrease as a consequence of using SLP-C needs further investigation.

Clinical and Morphological Response to UV-B Irradiation After Excimer Laser Photorefractive Keratectomy*

This paper represents an update on a study that has been reported elsewhere (Nagy ZZ et al: Ophthalmology 104:375-380, 1997). The aim of the study was to evaluate the clinical and light- and electron-microscopic effects of ultraviolet-B (UV-B) exposure on the outcome of photorefractive keratectomy (PRK). A total of 42 pigmented rabbits were used in the study. One eye from each of 12 rabbits received a 193 nm 45-microm deep (-5.0 diopters [D]) excimer laser PRK, one eye from each of 12 rabbits received a 135-microm deep (-15.0 D) excimer laser PRK, and one eye from each of 12 rabbits received a 270 microm deep (-30.0 D) excimer laser PRK. Twenty-one days after PRK, six of the laser-treated eyes from each group were exposed to 100 mJ/cm2 UV-B (280-320 nm). The other six rabbits from the PRK groups received no further treatment. One eye from each of six rabbits received only UV-B irradiation, serving as control. Subepithelial haze was evaluated before and after UV-B irradiation. Clinical changes were followed by laser tyndallometry, confocal corneal biomicroscopy, ultrasound biomicroscopy, and endothelial specular microscopy. Corneal morphology was assessed 4, 8, and 12 weeks after UV-B exposure, employing light microscopic and transmission electron-microscopic techniques (TEM). Eyes only exposed to 100 mJ/cm2 UV-B exhibited keratitis for 2 days, but showed no haze and were histologically normal at all time intervals. The PRK-UV-B-irradiated rabbit eyes exhibited a significant increase of stromal haze compared to the eyes receiving PRK alone; this phenomenon correlated with the depth of photoablation. The severity of clinical findings also correlated with the previously attempted photoablation depth; in PRK-UV-B-irradiated eyes the symptoms were much more serious than in eyes treated with PRK alone. Histologically, the main difference between the UV-B-irradiated and nonirradiated-post-PRK eyes was the presence of anterior stromal extracellular vacuolization in the UV-B-exposed eyes. The vacuolated foci were confined to the PRK treatment area, contained increased numbers of keratocytes and showed a disorganization of normal collagen lamellae. Transmission electron microscopy revealed activated keratocytes containing abundant rough endoplasmic reticulum, prominent Golgi zones, and extracellular vacuoles filled with amorphous material. The haze and morphological changes showed a tendency to incomplete resolution over a period of 12 weeks. Ultraviolet-B exposure during post-PRK stromal healing exacerbates and prolongs clinical symptoms and the stromal healing response, which is manifest biomicroscopically by augmentation of subepithelial haze. The findings suggest that excessive ocular UV-B exposure should be avoided during the period of post-PRK stromal repair and that UV-B may modulate the response of tissues to excimer 193 nm, and perhaps, other laser energy in general.

Influence of post-LASIK corneal healing on scanning laser polarimetric measurement of the retinal nerve fibre layer thickness

Aim: To investigate the influence of laser assisted in situ keratomileusis (LASIK) on the values for retinal nerve fibre layer thickness (RNFLT) as measured with scanning laser polarimetry (SLP) during the healing process of the cornea after LASIK. Methods: SLP with the GDx instrument was performed on 20 consecutive healthy subjects without any eye disease undergoing LASIK for ametropia correction. The SLP measurements were performed before the surgery, and at 1 and 3 days, as well as at 3 months, after LASIK. Thickness data from images of one randomly selected eye per subject were analysed using the ANOVA and Duncan multiple comparison tests. Correlation coefficients between RNFLT data and the treatment parameters were also calculated. Results: Somewhat similar results were found for the different retinal areas. The measured values for superior average RNFLT decreased significantly at all time points compared to the preoperative baseline (p<0.003, Duncan test), but increased significantly between postoperative day 1 and the final visit at 3 months (p=0.025, Duncan test). Inferior average RNFLT in the early postoperative days was significantly smaller than at 3 months after LASIK (p<0.05, Duncan test), and tended to be smaller than at baseline. The thickness values before surgery and at the final visit, however, showed no significant difference (p=0.698, Duncan test) in this region. Ellipse average RNFLT was significantly smaller in the early postoperative days than the baseline value before LASIK. However, the measured value had significantly increased again by the time of the final visit (p<0.02, Duncan test). This value at the final visit showed no difference from the baseline value (p=0.46, Duncan test). The changes in the nasal average and temporal average RNFLT were not statistically significant. No correlation was found between the change in the SLP measured thickness values and central corneal thickness at baseline and its change after surgery, nor with the change in cylindrical correction due to LASIK, or the length of the suction time during surgery (p>0.05 for all correlations). Conclusion: The SLP technique is sensitive to the corneal optical properties, and RNFLT as measured with SLP shows changes after LASIK. Most of these changes, however, diminish with time after surgery, and the values tend to return to the preoperative results during the first 3 months of corneal healing following uncomplicated LASIK. It appears that in uncomplicated cases the transient RNFLT changes are artefacts and do not imply pathological thickness alterations due to LASIK.

Nocturnal blood pressure and intraocular pressure measurement in glaucoma patients and healthy controls

Daytime and nocturnal intraocular pressure (IOP) values and systemic blood pressure (BP) values were compared in 60 non-glaucomatous controls, 54 glaucoma patients with normal visual field, and 46 glaucoma patients with visual field loss. The daytime IOP was measured with a Goldmann applanation tonometer and the nocturnal IOP with a Bio-Rad-Tono-Pen 2™. The BP was measured with either a mercury manometer or with a Meditech ABPM-02 Ambulatory Blood Pressure Monitor, which took BP readings at 60 minute intervals. A tendency towards increasing IOP and decreasing BP was detected in the non-glaucomatous controls, within normal limits, and pathological changes of IOP and BP were observed with a significantly high occurrence (5% > P > 2%; Pearsons χ2-test) in the glaucoma group with visual field loss.

Positioning of electronic subretinal implants in blind retinitis pigmentosa patients through multimodal assessment of retinal structures

PURPOSE To optimize methods for positioning subretinal visual implants, customizing their cable length, guiding them to the predetermined retinal position, and evaluating their performance. METHODS Ten eyes of 10 patients (6 male, 4 female, mean age 46.4 years) were investigated before implantation of a subretinal visual implant. The structural characteristics of the retina as well as the ocular dimensions were determined. Topographic images of the prospective implantation site were subdivided into grids of squares. Each square received a weighted score for suitability. The sum of the scores was calculated, and the region with the highest score was chosen for the implant. In each case, the implants power supply cable length was calculated by means of magnetic resonance imaging. The planned and achieved positions before and after implantation were compared. RESULTS The mean light sensitivity ratio between the area actually covered by the chip and that of the planned position was 90.8% with an SD of 11.4%. In two cases with almost perfect positioning, the computed ratio was 100%. Measurements showed that to achieve a 95% sensitivity rate the difference between the planned and achieved chip position must be less than 1.7 mm. Preoperative calculations of the intraocular cable length proved accurate in all cases. CONCLUSIONS Preoperative evaluation of retinal structures and eye morphology is useful for guiding a retinal implant to the designated area. It is a meaningful tool for planning and performing retinal chip implantation, and it optimizes personalized implantation. (ClinicalTrials.gov numbers, NCT00515814, NCT01024803.).

Photorefractive keratectomy for astigmatism with the Meditec MEL 60 laser

PURPOSE To evaluate the results of photorefractive keratectomy (PRK) in eyes treated with astigmatic refractive errors. METHODS Nine hundred forty eyes were treated with the Aesculap Meditec MEL 60 ArF excimer laser. Treatment groups were: Group 1 (n=746) eyes with compound myopic astigmatism, Group 2 (n=104) eyes with compound hyperopic astigmatism, Group 3 (n=75) eyes treated for mixed astigmatism, and Group 4 (n=15) eyes with simple myopic astigmatism (negative cylinder). RESULTS In Group 1, the preoperative spherical equivalent refraction of -6.10 D with an average of -1.50 D cylinder decreased to -0.95 D with -0.13 D cylinder; uncorrected visual acuity (UCVA) of 20/40 or better was achieved in 86% (642/746 eyes); 20/20 or better in 58% (433/746 eyes); 0.8% (6/746 eyes) lost two lines of spectacle-corrected visual acuity (SCVA); 74% (552/746 eyes) were within +/-0.50 D and 93% (694/746 eyes) were within +/-1.00 D of target refraction. In Group 2, preoperative mean +4.57 D spherical equivalent refraction with an average of +1.57 D cylinder decreased to +1.13 D with +0.38 D cylinder; UCVA of 20/40 or better was achieved in 84% (87/104 eyes); 20/20 or better in 46% (48/104 eyes); 14,4% (15/104 eyes) lost two or more lines of SCVA; 52% (54/104 eyes) were within +/-0.50 D and 82% (85/104 eyes) were within +/-1.00 D of target refraction. In Group 3, mean preoperative -4.20 D cylinder and +3.00 D spherical equivalent refraction decreased to -0.50 D cylinder and -0.50 D spherical equivalent refraction; UCVA of 20/40 or better was achieved in 83% (62/75 eyes); 20/20 or better in 32% (24/75 eyes); 13.3% (10/75 eyes) lost two or more lines of SCVA. In Group 4, mean preoperative -3.98 D cylinder decreased to -0.62 D cylinder; UCVA of 20/40 or better was achieved in 60% (9/15 eyes); none of the eyes achieved 20/20 or better; SCVA remained stable in 6.6% (1/15 eyes) and decreased two or more lines in 20.0% (3/15 eyes); 20% (3/15 eyes) were within +/-0.50 D and 53.3% (8/15 eyes) were within +/-1.00 D of target refraction. CONCLUSION PRK with the Meditec MEL 60 laser produced the best results in eyes with compound myopic astigmatism (Group 1). In all other groups, results were less predictable.

Photorefractive keratectomy for hyperopia in 800 eyes with the Meditec MEL 60 laser.

PURPOSE To evaluate the refractive results of 800 hyperopic eyes undergoing PRK treatment. METHODS Eight hundred hyperopic eyes were treated with PRK. An Aesculap-Meditec MEL 60 scanning ArF excimer laser used. Treatment Group 1 consisted of eyes with a preoperative refractive error of +3.50 D or less (n = 482) and Group 2, of +3.75 D or more (n = 318). RESULTS Preoperatively, Group 1 required an average correction of +2.88+/-1.34 D and Group 2 required +5.64+/-2.96 D. One year after PRK, average residual correction was +1.26+/-1.24 D in Group 1, and in Group 2, +2.46+/-1.84 D. In Group 1, uncorrected visual acuity (UCVA) was 20/40 or better in 88.4% (426/482); 20/20 or better in 75.7% (365); 2.1% (10/482) of eyes lost 2 lines, 2.1% (10/482) gained 2 lines; 3.1% (15/482) gained 2 or more lines of BSCVA; 74.4% (359/482) of eyes were within +/-0.50 D of target correction and 84.8% (408/482) were within +/-1.00 D. In Group 2, 47.5% (151/318) had UCVA of 20/40 or better; 34.2% (109/318) saw 20/20 or better uncorrected; 19.1% (61/318) lost 2 lines; 11.6% (37/318) lost 3 lines; none of the eyes gained 2 or more lines of BSCVA; 22.3% (71/318) were within +/-0.50 D and 46.8% (149/318) were within +/-1.00 D of target correction. Refractive stability was achieved after 6 months; a slight regression after 6 months was still observed. In Group 1, 10.5% (42/482) and in Group 2, 21.6% (69/318) complained of problems with daytime vision (glare and ghost image); during night-driving in Group 1, 17.6% (85/482) and in Group 2, 40.5% (129/318) had problems. CONCLUSION PRK with the Aesculap-Meditec MEL 60 scanning ArF excimer laser offered the best long-term results with +3.50 D or less preoperative refractive error. With higher corrections, regression, decrease in BSCVA, and daytime visual problems were encountered.

Treatment of intraocular pressure elevation after photorefractive keratectomy

Purpose: To study the effect of timolol maleate, dorzolamide, or a combination of both in post photorefractive keratectomy (PRK) eyes with an elevated intraocular pressure (IOP) after topical steroid administration. Setting: Refractive Surgery Outpatient Department, 1st Department of Ophthalmology, Semmelweis University, Budapest, Hungary. Methods: Forty‐five patients with elevated IOP were randomly enrolled in 3 groups: Group 1 received timolol maleate 0.5% twice a day; Group 2 received timolol maleate 0.5% twice a day and dorzolamide 2% 3 times a day; and Group 3 received only topical dorzolamide 2% 3 times a day. Intraocular pressure was measured 3 days and 1, 3, and 6 weeks after the antiglaucoma medication was started. Results: The mean preoperative IOP was 15.25 mm Hg ± 1.28 (SD). Following administration of topical fluorometholone, the IOP increased a mean of 27.39 ± 2.88 mm Hg. Six weeks after the antiglaucoma therapy was started, the mean IOP reduction was 6.6 mm Hg in Group 1, 8.86 mm Hg in Group 2, and 4.64 mm Hg in Group 3. Conclusions: A combination therapy of timolol 0.5% and dorzolamide 2% was most effective in treating secondary IOP elevation after PRK. Dorzolamide alone did not adequately control secondary post‐PRK IOP elevation.