Late surface opacification of Hydroview intraocular lenses.

PURPOSE: To describe clinical and pathological features of Hydroview intraocular lenses undergoing delayed surface opacification resulting in visual deterioration. METHODS: Twenty one eyes which underwent uncomplicated phacoemulsification and Hydroview lens implantation with good visual recovery, presenting at 46-146 weeks post-surgery with visual deterioration and glare symptoms resulting from opacification of the implants, were included in the study. Twelve eyes had severe opacification, of which nine underwent intraocular lens exchange and three more are still awaiting surgery. The method of explantation is described. The explanted intraocular lenses were examined using light microscopy, scanning electron microscopy and x-ray microanalysis using a light element detector. RESULTS: Light microscopy and scanning electron microscopy revealed diffuse granular deposits of approximately 5 microm diameter covering the optic surfaces but sparing the lens haptics. Light microscopic staining techniques and x-ray microanalysis confirm the major component of the deposits to be calcium phosphate salts. CONCLUSIONS: Late opacification of Hydroview intraocular lens implants is uncommon and aetiology seems to be multifactorial. Implant exchange is necessary to restore sight in some cases. As new materials are increasingly used it is important to highlight such unusual occurrences.

The physical basis of transparency of the normal cornea.

An understanding of the physical basis of corneal transparency has been a subject of interest amongst physicists, basic scientists and ophthalmologists. Impairment of corneal clarity is a significant cause of visual morbidity worldwide. Several highly mathematical treatises have been presented in support of different theories of corneal transparency in the normal cornea relating structure to function, particularly in the years since the advent of the electron microscope, which has brought about a much greater understanding of corneal ultrastructure. This review presents the concepts that underpin the theories of corneal transparency.

Effects of air injection into the corneal stroma of man: an in vitro study.

BACKGROUND: Corneal stromal air injection has been described for assisting the deep dissection of the recipient corneal bed in lamellar grafting. The consistent finding of air entering the anterior chamber is considered an undesirable complication of the procedure. The route of air entry into the anterior chamber has not been investigated previously. METHODS: The route of air passage through the cornea was studied in 10 human cadaver eyes by direct viewing of the inner corneal surface with an operating microscope and by electron microscopy. RESULTS: Air entered the anterior chamber peripheral to Descemet's membrane in every case in the absence of pre-existing corneal pathology. The air expansion of the cornea occurred only along planes occupied by keratocytes and their cell processes and this expansion caused disruption of the keratocytes. CONCLUSIONS: Air injection into the cornea caused bubbles to enter the anterior chamber peripheral to Schwalbe's line, through the trabecular meshwork. The air produced cleavage of the collagen lamellae along those planes occupied by keratocytes and their cell processes since this provides a path of least resistance. Disruption of the keratocytes is a direct mechanical effect. Descemet's membrane and Bowman's layer act as effective barriers to air passage in the normal cornea.