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AIM: to assess the influence of the endothelial graft thickness on postoperative visual acuity following modified endothelial keratoplasty (UTDSAEK). MATERIAL AND METHODS: The study included 49 patients with pseudophakic bullous keratopathy and no concomitant disorders of either the retina or optic nerve. Ultrathin Descemet's stripping automated endothelial keratoplasty (UTDSAEK) was performed in all cases. Corneal graft thickness was measured 1 year after UTDSAEK by means of optical coherence tomography. Postoperative visual acuity values were compared in patients with the endothelial graft thickness from 51 to 98 microns (27 eyes) and those with the endothelial graft thickness from 102 to 121 microns (22 eyes). The dynamics of the graft thickness change after surgery was also assessed. RESULTS: The thickness of the graft gets reduced by an average of 21% over the first 2-3 weeks after UTDSAEK and by approximately 5% over 2 more months. For the next few years it remains relatively stable (the maximum follow-up period was 5 years). The study showed no statistically significant difference in visual acuity between two groups of patients with the endothelial graft thickness of less than and greater than 100 microns (p=0.7). CONCLUSION: The thickness of the endothelial graft for UTDSAEK has no statistically significant effect on postoperative visual acuity. The optimal thickness of the graft being cut out lies in the range from 100 to 150 microns. Such grafts adapt well to the posterior surface of the recipient cornea with no significant changes to its topography. Moreover, thicker grafts are easier manipulated before insertion into the anterior chamber and are associated with a lower risk of perforation during acquisition as compared to grafts of under 100 microns.

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The effect of laser treatment on ocular fundus tissues depends on quite a number of factors, mostly uncontrollable, hence, laser output parameters may vary dramatically even within the same fundus. In classical procedure ('threshold' laser coagulation), these parameters are adjusted to ophthalmoscopically visible tissue color changes at the site of coagulation. However, this method does not work with modern subthreshold techniques, that are more tissue-saving and thus, produce no immediate and visible changes in the retina. Calculation methods that are used instead are much less accurate. Photoacoustic monitoring may become a real breakthrough in this field. The method involves acoustic analysis of the response to soft and short laser pulses ('test' pulses). Heating of the target by the main therapeutic laser causes alterations in its physical properties and, consequently, the laser-induced acoustic signal. This gives us an ability to monitor the temperature and thus, to evaluate the clinical effect of coagulation despite the absence of visible changes at the site. The most promising techniques of photoacoustic monitoring that are being developed are discussed here.

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AIM: to study the nature of intraocular lens (IOL) opacification depending on the patient's ocular status and general condition. MATERIAL AND METHODS: A total of 9 patients (9 eyes) with 3-6 year history of progressive IOL opacification were enrolled. All the IOLs were acrylic (either hydrophilic--7 cases, or hydrophobic--2 cases). Two patients had their IOLs exchanged due to opacification. Six patients earlier underwent glaucoma surgery. Two patients were type 2 diabetic. Slit lamp biomicroscopy and optical microscopy were used for IOL examination. RESULTS: The surface of hydrophilic acrylic lenses appeared bumpy because of multiple variously shaped translucent granules separated by a chaotic network of furrows and microfractures and located predominantly in the optic zone. In a more severe case, a bowl-shaped impression was observed in the area of opacification. Surface changes of hydrophobic acrylic lenses were in the form of isolated and confluent glistening formations (microcavities). CONCLUSION: Signs of IOL degradation develop over a long period of time (3-6 years, in our experience) and mostly involve the anterior surface of the lens optic. Ocular comorbidity, glaucoma in particular, as well as other surgery and/or therapeutic treatment following IOL implantation may contribute to its opacification. Analysis of published data and own observations suggest that hydrophobic IOLs should be preferred in patients with concomitant diseases, especially diabetes mellitus. Granular deposits, if accumulate, may lead to deformation of the lens optic, as confirmed by the bowl-like impression in one of the explanted hydrophilic IOLs.

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UNLABELLED: Aim - to study biomechanical properties of the cornea in patients with bullous keratopathy before and after keratoplasty. MATERIAL AND METHODS: Ocular response analyzer (ORA, Reichert) indices were studied in 37 patients (37 eyes) with bullous keratopathy before and after surgery - in 1, 2, and 6 months and then in 1, 2, 3, and 5 years. The following keratoplasty modifications were performed: ultrathin Descemet's stripping automated endothelial keratoplasty (UTDSAEK) - in 17 cases, microkeratome-assisted posterior keratoplasty (MAPK) - in 13 cases, half top-hat penetrating keratoplasty (HTH PK) - in 7 cases. RESULTS: Corneal hysteresis (CH) and corneal resistance factor (CRF) values were significantly decreased in non-operated bullous keratopathy eyes as compared to healthy ones (p<0.05). By the 6-month follow-up these parameters have been found to be partially recovered and stabilized in all groups, however, still lower than normal (p<0.05). Differences between the groups were never statistically reliable, not at any time after surgery. Moreover, in eyes with bullous keratopathy, the mean corneal-compensated intraocular pressure (IOPcc) exceeded the mean Goldman-related IOP (IOPg) by 2.4 mmHg. One month after keratoplasty the difference between IOPcc and IOPg was 2.7, 4.3, and 3.6 mmHg in the MAPK, UTDSAEK, and HTH PK group, respectively; in 6 months - 2.6; 2.4 and 3.6 mmHg, respectively (p<0.05). In the fellow healthy eyes the two IOP measurements were not statistically different. CONCLUSION: Chronic edema of the cornea results in alteration of its viscoelastic properties. It has been shown that CH and CRF values decrease significantly in the eye involved as compared to the fellow healthy eye. After keratoplasty, regardless of the exact modification, these parameters partially recover, but remain lower than normal for at least 5 years as it was in our study. Neither before the surgery (when the cornea is chronically swollen), nor after, does corneal thickness correlate with its biomechanical indices. Postoperative reduction in corneal rigidity in eyes with bullous keratopathy may be confusing and lead to underestimation of the true level of IOP, thus, causing delays in diagnosis of concomitant glaucoma.