[Chemical microanalysis of mineral deposits on explanted hydrophilic acrylic intraocular lenses].

AIM: to perform chemical microanalysis of mineral deposits on the surface of explanted hydrophilic acrylic intraocular lenses (IOL). MATERIAL AND METHODS: Two soft IOLs made of hydrophilic acryl (one, however, hydrophobic surface coated) and explanted 3 and 6 years after implantation were examined by scanning electron microscopy (EVO LS10, "Karl Zeiss", Germany). Chemical composition of the lens surface was studied using an energy-dispersive spectrometer (EDS X-Max50, Oxford, Great Britain). RESULTS: Chemical microanalysis allowed identification of the deposits, which turned out to be non-stoichiometric hydroxylapatite (also, hydroxyapatite (HA)) crystals with zinc impurity (up to 1.4%weight). CONCLUSION: The two samples represent two stages of a single process. The early stage is associated with newly formed HA crystals that are unable to cause any significant changes to the lens surface. However, as spherocrystals grow, they exert a crystallization effort that moves their growth centers apart with subsequent lens rupture and deformation. Crystal morphology undergoes dynamic changes: while primary (newly formed) crystals are sheaf-like, mature are spheres. A growing HA is non-stoichiometric. Zinc abundance accounts for appearance of its separate mineral phase. Hydrophilic properties of acrylic polymer determine its high affinity for HA crystals. Hydrophobic coating (sample no.1) does not completely prevent lens opacification due to mineral deposits on its surface.

[Analyzing causes for opacification of acrylic IOLs].

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.

[Intraocular lens power calculation in silicone-filled eyes].

AIM: to evaluate the accuracy of different modified methods for axial length (AL) measurement in silicone-filled eyes. MATERIAL AND METHODS: The study was conducted in a group of 60 patients (60 eyes) with silicone oil tamponade (Oxane 1300 cst). Axial length measurements were taken using IOL Master optical coherence biometry ('silicone-filled eye' mode) and modified A-scan ultrasound biometry (velocity of ultrasound passing through the vitreous body set at 980 m/s and 1000 m/s). After phacoemulsification and silicone oil removal, AL measurements were repeated on same devices switched to standard pseudophakia modes. The results were then compared to those obtained in modified modes before the surgery. RESULTS: Preoperative axial lengths measured by A-scan at 980 m/s tended to be 0-1.5 mm (the median of 0.52 mm) shorter than those obtained after silicone oil removal. With 1000 m/s ultrasound velocity the error was much less--from 0 to 0.5 mm (the median of 0.15 mm). As for preoperative ALs by IOL Master in the 'silicone-filled eye' mode, they were 0-1.2 mm (the median of 0.3 mm) longer than postoperative ones. CONCLUSIONS: In cases of impossibility or inaccessibility of optical biometry, measurements taken with an A-scan device set at 1000 m/s are sufficient. The true AL of an eye with silicone oil tamponade falls somewhere between the values obtained with 1000 m/s ultrasound and IOL Master in the 'silicone-filled eye' mode.