Transmittance characteristics of transparent hydrophobic acrylic foldable intraocular lenses that were in vivo for a prolonged period of time: A UV visible spectrophotometric study.

PURPOSE: To record experimental data on the spectral transmittance characteristics of transparent hydrophobic acrylic foldable IOLs, which were in vivo for a prolonged period of time and explanted under clinical indications and also to compare the data with that of corresponding control and crystalline lens along with review of the relevant literature. METHOD: Material and make of each of the explanted intraocular lenses (IOLs) as well as pre-explantation clinical status of the eyes were confirmed from the medical record. The transmittance of wavelength from 185 to 900 nm of each of the selected IOLs was measured using Shimadzu UV 2600 UV visible (UV-Vis) spectrophotometer in double-beam configuration and probe version 2.16 software. The data obtained were statistically analyzed. RESULTS: The mean transmittance of 12 clinically explanted IOLs at spectral range 300-700 nm was 49.5% ± SD 6.9%. This value was 10% and 38% less than the corresponding clear (59% ± SD 0.4%) and yellow (87.5% ± SD 0.4%) control, respectively. The mean transmittance of the analytes in the UV range was 43.3 ± SD 6.9%, and it was almost similar to the control. The data showed wide variations without good correlation, and it matches with the human crystalline lens at the age range of 50-60 years. All eyes were otherwise healthy, and none had age-related macular degeneration. CONCLUSION: In comparison with fresh IOL with a yellow filter, light transmittance at the spectral range 300-700 nm was found decreased in all the IOLs, which were in vivo for an average period of 12.25 ± 4.4 years. All IOLs transmitted variable amounts of UV radiation. More data are required for further analysis on the subject.

Raman Spectroscopy of six explanted acrylic hydrophobic foldable intraocular lenses with glistening.

Purpose: To study and interpret Raman spectra of six explanted acrylic hydrophobic foldable intraocular lenses (HFIOLs) with grade six microvacuoles and to understand the possible mechanism for microvacuole formation. Methods: Clinical data, slit-lamp photographs, and optical microphotographs of the explanted analytes were obtained. RS of the analytes were registered using a confocal Raman microscope (Lab RAM HR Evolution, Horiba Jobin Yvon) and Horiba Lab Space 6 Spectroscopy Suite software. Data were interpreted by identifying the functional group and fingerprint region of the spectra about the available literature. Results: IOLs were explanted for visual impairment after an average interval of 11.2 years following implantation. Each of the HFIOLs exhibited distinctive and identical Raman bands at the frequency range of 200-1,800, 2,600-3,000, and 3,200-3,700 cm-1 which were identified with those reported in the literature. The unique bands and peaks of the spectra were specific to the functional groups, its ring and other stretching variations, hydroxyl group, and water molecule. A spike at 1,640 cm-1 revealed the presence of monomer and indicated material bioincompatibility of the samples. Conclusion: Raman spectroscopy (RS) was found specific and an effective tool to detect the material change in the HFIOL and constituents of polymer biomaterial about microvacuole formation and also suggested modification and development of a more biocompatible and non-biodegradable polymer blend where RS could be a monitoring tool.

Changing pattern of childhood blindness in eight North-Eastern states and review of the epidemiological data of childhood blindness of India.

PURPOSE: To assess the causes of visual impairment and blindness in children in all the schools for the blind in eight northeastern states and to determine its temporal trend, and to analyze the result with reference to various regional epidemiological data on childhood blindness in India. METHODS: Children aged ≤16 years, with a visual acuity of ≤6/18 in the better eye, attending 17 schools for the blind were examined between November 2018 and March 2020. WHO protocol and reporting format was used for the evaluation, diagnosis, and classification of the causes. RESULTS: Out of 465 eligible study participants, 93.76% were blind and only 12.26% of causes were avoidable. Anatomical causes of childhood blindness were whole globe (43.2%), cornea (17.20%), optic nerve (12.04%), retina (9.68%), and lens (9.46%). Etiological causes were unknown (52.69%), hereditary (26.02%), intrauterine (15.05%), and 26.08% had blinding congenital ocular abnormality (s). Regional temporal trend revealed a decrease in corneal and childhood causes and an increase in retina, optic nerve, hereditary, and intrauterine causes. CONCLUSION: A constellation of causes were differentiable but matched with the overall emerging trend of childhood blindness in India. Higher corneal, unavoidable, and unknown causes suggest a region-specific action plan for controlling childhood blindness as well as rehabilitation.

Optical biometry and influence of media opacity due to cataract on development of axial length in NorthEast Indian paediatric patients- A prospective study.

AIM: To study the influence of media opacity due to cataract on the development of axial length in paediatric patients from North-East India, using optical biometry. METHOD: This is a prospective, observational study, including consecutive patients attending the paediatric ophthalmology clinic, over a period of 1 year. Patients with other ocular and systemic diseases, unfit for optical biometry measurements due to dense cataract, nystagmus and strabismus were excluded and rest divided into three groups after proper age matching - 1. Group A (Bilateral cataract) 2. Group B (Unilateral cataract) 3. Group C (Bilateral normal). The axial length of the various groups was analysed using independent sample test (for bilateral cataract group) and paired t-test (for unilateral cataract group). Linear regression analysis between age and axial length was done. RESULTS: A total of 177 patients were included.80 cases in Group A (bilateral cataract), 18 cases in Group B (unilateral cataract) and 79 in Group C (bilateral normal) The mean age of the patients in all the groups was 8.88 ± 3.51 years (range: 1-17 years). The bivariate analysis and simple linear regression revealed a statistically significant correlation between age and AL in case of cataractous eyes. (Pearson's coefficient: 0.341, p < 0.001). The mean AL was significantly longer (p = 0.013) in the cataractous eyes (mean = 23.38 ± 2.08 mm) of Group A(bilateral cataract) in the 7-12 years age group as compared to the bilaterally normal eyes (mean AL = 22.57 ± 0.70 mm) of patients in the same age group in Group C. The mean AL of cataractous eyes in group B (unilateral cataract) (mean = 22.46 ± 1.73 mm) as compared to the fellow normal eyes, (mean = 21.87 ± 0.97 mm) was not statistically significant. CONCLUSION: Cataractous eyes have an abnormal axial length development. The influence of media opacity due to cataract on development of axial length in paediatric eyes in the North-East Indian population is variable, in line with global data on the same. Although there is some influence of media opacity, the exact nature is not clearly understood and may have a crucial interaction with genetic and other environmental factors. Genetic testing integrated with biometric analysis is recommended for further understanding of the ocular growth and development.

Delayed postoperative opacification of three hydrophobic acrylic intraocular lens: A scanning electron microscopic and energy dispersive spectroscopic study.

Purpose: The aim of this study was to report scanning electron microscopic (SEM) and energy dispersive spectroscopic (EDS) findings of three specimens of opaque hydrophobic acrylic intraocular lens (IOL) explanted in delayed postoperative period for visual indications. Methods: Clinical data and photographs from each subject were obtained. Explanted IOLs were examined under gross and light microscopy followed by SEM coupled with EDS. Results: All three subjects underwent IOL implantation following senile cataract extraction at an average age of 64.3 ± 0.3 years, and the IOLs were in situ for a duration of 11.3 ± 4.04 years. The IOL explantation and exchange were done due to late postoperative opacification of the IOL and significant visual deterioration. The milky iridescent opacity affected the full thickness of IOL optics in the first two specimens and in the third only two surfaces were involved. SEM detected surface cracks in the first specimen, typical conglumated surface, pores and accumulation of crystals with surface deposit of nano-particles on the second specimen and uneven surface erosion in the third specimen. SEM detected mainly sodium (Na) and chloride (Cl) spikes. All patients recovered normal vision following IOL exchange. Conclusion: SEM features of the IOL optics and absence of calcium and phosphate spikes in EDS and other findings were consistent and suggestive of hydrolytic biodegradation of hydrophobic acrylic IOL polymer in ocular media and was responsible for delayed postoperative opacification of the hydrophobic IOLs and visual loss.

Scanning electron microscopic features of explanted degraded hydrophobic acrylic intraocular lenses which were in vivo for a prolonged period.

Purpose: To study and document electron microscopic features in explanted hydrophobic microvacuoles affected acrylic intraocular lenses (IOL) which were in vivo for an average duration of 11 years. Methods: Scanning electron microscopic (SEM; Hitachi S 3000 N EXAX Genesis VP SEM) study of five explanted hydrophobic acrylic IOL which had clinically evident microvacuoles prior to explantation, was done. The IOLs were in vivo for a prolonged period and needed explantation for various indications. Only those hydrophobic acrylic IOLs which fulfilled the inclusion criteria were included. The findings were compared with control specimens. Results: The IOLs were in vivo for an average duration of 11.6 ± 4.21 years. The cause of explantation of IOL was subluxation in four cases and low visual acuity in one case. Bulk degradation and microvacuoles on cut sections throughout the IOL optics and undulating surface patterns over both the surfaces of the IOL has been documented in all the specimens. No such findings were noted in the control specimens where the surface and texture were homogenous. Conclusion: SEM findings of the structural changes in explanted IOL documented in the study demonstrate that hydrophobic acrylic IOL is degradable in vivo. Microvacuoles are a clinical manifestation of the structural changes that occur at a microscopic and molecular level. These changes are not seen in IOLs which have not undergone intraocular implantation. To our knowledge, a similar study of this kind has not been done.