Volume 39 ·  Issue 06 ·  2003

The present study was designed to examine the visual acuity (VA) and contrast sensitivity function (CSF) under three refractive correction methods, the visual performance and vision quality under different correction methods were compared and analyzed.

Twenty three college students with myopia (41 eyes, myopia range: -1.25 D~9.25 D; astigmatism <0.50 D) were enrolled and fully corrected by three different methods: 1) spectacles with resin lens material (SP); 2) soft contact lens (SCL); 3) rigid gas-permeable lens (RGP). The distant and near LogMar VA and CSF were examined. To avoid the subjective bias, the correction procedure was randomly selected and the VA chart and CSF chart used had the same pattern but different letters' organization or directions.

The best corrected distant VA was significantly higher in RGP wearing eyes than those in the Soft-CL and SP wearing eyes (P<0.01 and P<0.05, respectively). No statistically significant difference was detected between the SP and SCL wearing eyes. There was no significant difference in the near VA among these three conditions, although the near VA in RGP group was slightly better than that in the SCL condition. There was no significant difference in CSF value at low spatial frequencies (1.5 cpd and 3 cpd) among these three conditions. However, at middle and high spatial frequencies (6 cpd, 12 cpd and 18 cpd), the RGP curve was the highest and followed by the SCL and SP curves.

RGP correction offers the best visual acuity quality for myopia subjects. The CSF assessment can be used as an indirect method to evaluate the quality of corrected retinal image.

To analyze the aberration of human eyes after LASIK by using wavefront analyzer, to evaluate the eye aberrations by using the large spot in refractive surgery, and to compare the aberrations in different pupil zones.

This is a prospective clinical study. Preoperatively and postoperatively, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), spherical equivalent (SE) and aberrations were evaluated on each patient. The patients were divided into three different groups according to the SE diopter before the surgery. We used the SAS and SPSS10.0 statistic software to analyze the data.

Preoperatively, BCVA was 4.98±0.07. Ten days after surgery, UCVA and BCVA were 4.92±0.10 and 4.95±0.09, respectively. One month after surgery, UCVA and BCVA were 4.96±0.09 and 4.99±0.09, respectively. Over time, visual acuity improved with Postoperatively, parts of the eye's BCVA were better than preoperatively. Ten days after LASIK, the SE of three groups were hyperopic. But with time, SE changes to myopia. In the Allegretto exam, high order aberrations increased immediately after surgery in each group (P<0.05), but decreased with time (P>0.05) and did not return to preoperative values at one month. Preoperatively, the total aberrations (RMSg) were larger than postoperatively. The aberrations especially spherical are larger in the 6.5 mm pupil zone than in the 4 mm pupil zone. Preoperatively, there were no significant differences of high order aberrations between the three groups (P>0.05). But after surgery, there were significant differences (P< 0.05).

Initially, high order aberrations increased after LASIK, but decreased over time. Preoperatively, there were no significant differences of aberrations between the three groups, but after surgery, significant differences existed. The aberrations especially spherical were larger in the 6.5 mm pupil zone than in the 4 mm pupil zone. Allegretto wave-front analyzer can be used for low to middle myopia.

To evaluate the degree and correlative factors of decentration of orthokeratology lenses and its effect on the visual function.

Two different kinds of orthokeratology lenses were fitted to 270 eyes of 135 patients [initial mean refractive error: (-3.98±1.51) D]. Humphery Instruments ATLAS 8.0 was used for the computer-assisted analysis of corneal differential topographical maps. The examination of corneal topography was proceeded on the patients before the fitting of orthokeratology lenses and 6-month later. The distance from center of optic zone to apex of the cornea was measured as the value of decentration of orthokeratology lenses. The factors influenced the value of decentration were analyzed, including the initial refraction error, astigmatism, keratometry values, corneal eccentricity, and the diameter of the lens. The complaints of patients were recorded. Questionnaires, involving the symptoms of monocular diplopia and glare, were used to evaluate the effects of decentration of orthokeratology lenses on the visual function.

The mean distance of decentration was (0.49 ±0.34) mm after one night fitting, the mean distance of decentration after follow-up for 1 month, 3 months and 6 months was (0.57±0.41) mm, (0.55±0.48) mm and (0.59±0.39) mm, respectively. After one month, the distance of decentration was less than 0.5 mm in 51.1% eyes, 0.5-1.0 mm in 35.6% eyes and more than 1.0 mm in 13.3% eyes. The direction of decentration in eyes with more than 0.50 mm decentration was mainly in the temporal side (48.5%). Patients with greater initial astigmatism and smaller diameter of lens showed greater distance of decentration (P<0.05). There was no statistically significant difference in the distance of decentration between two groups with different corneal eccentricities and keratometry values (P>0.05). The distance of decentration was greater in patients with monocular diplopia and glare.

The degree of decentration of orthokeratology depends on the degree of initial refractive error, astigmatism and the design of orthokeratology lenses. The degree of decentration can influence the visual function.

To investigate the efficacy and safety of the implantation of phakic anterior chamber intraocular lens (IOL) for high myopia.

A consecutive group of 73 eyes in 41 patients with -7.00 to -30.00 diopters (D) of myopia were implanted.

All of 73 eyes were implanted successfully and have been followed-up for 3 m (months). The uncorrected visual acuity was from FC/33 cm to 0.2 pre-operatively and 0.1 to 1.03 m post-operatively. The best corrected visual acuity (BCVA) was from 0.05 to 1.0 pre-operatively and 0.1 to 1.03 m post-operatively. The post-operative BCVA of every eye was not worse than the pre-operative one. The refractive diopters were from -7.00 to -30.00 D pre-operatively and -6.00 to +2.50 D 3 m post-operatively. There were no significant differences between pre- and 3 m post-operative mean corneal astigmatism (t=1.751, P=0.082) and mean intraocular pressure (IOP) (t=1.181, P=0.240), respectively. The mean counts of endothelial cells was (2680±538)/mm² pre-operatively and (2514±420)/mm² 3 m post-operatively. There was no significant difference (t=1.182, P=0.242) though it decreased 6.19%. No severe complications occurred.

The implantation of phakic anterior chamber IOL for high myopia is predictable, reversible and controllable with simple manipulation. No severe complication occurred in 3 m post-operatively, and long-time follow-up is still required.

To investigate the distribution of dopamine transporter (DAT) in the chicken eye and to explore the role of DAT in the occurrence of experimental myopia.

Thirty 2-day-old chickens were divided into four groups. Chicken eyes were fitted with lenses of -10 D (Group 1), -20 D (Group 2) and translucent goggles (Group 3) unilaterally. Chickens without any treatments were used as the control (Group 4). The refraction and the axial eye length of all chickens were measured after 3 weeks, then, all chickens were given an intramuscular injection of ¹²⁵I-β-CIT [2β-carbomethoxy-3β-(4-iodophenyl) tropane] and sacrificed two hours after injection. Retinal pigment epithelium (RPE) and neural retina were dissected from the eye as a whole layer in Groups 1 and 4; and dissected separately in Groups 2 and 3. Radioactive DAT from each specimen was assayed by γ-counter.

In Groups 2 and 3, the radioactive DAT value in the RPE from the experimental eyes was significantly greater than that in the neural retina and also greater than those in the RPE from the control eyes (P< 0.01). In Groups 1,2, and 3, the radioactive DAT value in the whole retina or RPE from the experimental eyes was significantly greater than those from the control eyes (P<0.01).

Retinal DAT is located mainly in the RPE and may be involved in the occurrence of both lens-induced myopia and form-deprivation myopia. These methods may provide a new approach for further studying the role of dopamine system in the occurrence of experimental myopia.

To determine the efficacy of the M₁-selective muscarinic antagonist, pirenzepine, in preventing lens-induced myopia in the guinea-pig and to study the mechanism and the possibility of treatment of myopia with pirenzepine.

Fifteen 4-week-old guinea-pigs were monocularly fitted with -10.00 D lenses for a period of 11 days. In Group I (n=7), both eyes received topical administration of 0.24% saline vehicle as the controls. In Group II (n=8), the lens-fitted eyes were topically treated with 10% pirenzepine, while the other eyes received the vehicle control. Ocular refraction and biometric measurements were collected on the first and the 11th days. All eyes were finally enucleated for histopathological examination to evaluate the possible toxic effects of pirenzepine.

In Group I, 11 days of lens-fitting produced -2.45 D myopia (t=3.141, P<0.05) with 0.05 mm elongation of axial dimension (t=2.500, P<0.05) as compared to the contralateral eyes. There were no significantly differences of refractive error and axial dimensions between the experimental eyes and the controls in Group II. Histological examinations revealed no obviously toxic effects in the pirenzepine - treated eyes.

Topical administration of the M₁-selective muscarinic antagonist, pirenzepine, prevents lens-induced experimental myopia in guinea-pig by inhibiting the elongation of axial dimension with no obvious damage to the ocular tissues.

To disclose the relationship between the deposition of advanced glycosylation end products (AGE) in the retinal vascular tissues and damage of retinal vessels in diabetic retinopathy.

Sixteen SD rats aged 2 months were divided into 4 groups, with 4 rats in each group. Rats in normal group received no treatment. Diabetes was induced by AGE in the diabetes group. Rat serum albumin (RSA, 40 mg/kg weight) was administered daily to healthy non-diabetic rats through tail veins for 2 weeks (RSA group). AGE-modified RSA was injected to rats in another group at the same route and dosage (AGE-RSA group). The number of pericytes in retinal capillary vessels was counted 2 weeks later.

After two weeks continuous AGE treatment, the average amount of pericytes of capillary vessel per 10 microscope visual field (× 100 magnification) in AGE group (4.31±0.34) was significantly less than that of RSA group (5.80±0.48) (P<0.01). Meanwhile, in the AGE-RSA group, AGE were identified in the retinal vascular tissues by immunohistochemical staining.

Injection of exogenous AGE into healthy rats induces vascular changes resembling those find in the diabetic retinopathy. AGE might be one of the independent pathogenic factors in the occurrence of diabetic retinopathy.

To study the cultivation and differentiation of neural stem cells (NSC) in vitro and observe the effects of retinal cell-conditioned medium on the differentiation of NSC.

Cells from subependymal zone of postnatal 0-3 days SD rat were isolated and cultured in vitro. Retinal cells of SD rat were cultured simultaneously. The supernatants (conditioned medium, SDR-CM) of cultured retinal cells were collected and used for the cultivation of the NSC from subependymal zone. Immunofluorescence method and anti-Thy1. 1 antibodies were used to identify the cells derived from the NSC.

Cultured NSC grew well in the serum-free culture medium. Cultured subependymal cells in the SDR-CM could be differentiated to the retinal cells. Some cells were stained positively with anti-Thy1. 1 antibodies.

These results showed that cultured NSC could survive well in vitro. SDR-CM can induce the NSC to differentiate to the retinal cells. The present study was designed to simulate the microenvironment of the eyes and to induce the differentiation of the NSC. Our in vitro model system may provide theoretical basis for the intraocular transplantation of retinal neurons.

To test the safety of guidelines for limiting exposure to low power level microwave radiation and to try to explore the mechanisms of early damages induced by such radiation in rabbit lens capsule epithelial cells, using flow cytometry as a quantitative method of evaluation of these damages.

The rabbit eyes were exposed to 5 mW/cm² (group I) and 10 mW/cm² (group II) power densities of microwave for 3 h. Annexin V-PI two-color flow cytometry was used to detect the changes of rabbits lens epithelial cells, apoptosis cells and secondary necrotic cells after radiation. The other eyes served as self-controls.

In group I, the percentage of early apoptosis cells in the experimental eyes was significantly greater than that of the controls (P<0.01), whereas no significantly difference in the percentage of secondary necrotic cells could be observed (P>0.05). In group II, there was no significant difference between the percentage of early apoptosis cells in experimental eyes and the controls (P>0.05), whereas the percentage of secondary necrotic cells in the experimental eyes was significantly greater than that of the controls (P<0.05). The percentage of secondary necrotic cells (16.2±5.6)% in group II is greater than that in group I (10.3±6.8)% (P<0.05), though there is no significant difference in the percentage of early apoptosis cells between these two groups (P>0.05).

Low power density of microwave radiation (5 mW/cm² and 10 mW/cm²) can induce irreversible damage of rabbit lens epithelial cells in a dose-dependent manner. Therefore, the safety dosage criterion of microwave exposure needs further investigation.

To develop a system of enhancing work efficiency in prevention of blindness in Zhejiang province by creating the Model County in prevention of blindness.

Twenty counties were selected in the whole Zhejiang province to serve as the candidates of the Model County in prevention of blindness in 1996-1998. The activities for prevention of blindness were conducted in these counties according to the five standards of the Model County in prevention of blindness established by the National Committee for Prevention of Blindness. The Model County in prevention of blindness was awarded only after checking and accepting by the authorities in county, provincial and national levels.

The effective way for creating the Model County in prevention was as follows: the local government put the prevention of blindness in the list of the priorities, the local committee for prevention of blindness was established, the three level network for prevention of blindness was established, the eye care workers were trained, the necessary equipment was provided. After the efforts for three years, seven counties were awarded as the Model County in prevention of blindness. In addition, Shaoxing Prefecture city became Model City in prevention of blindness. A strong effort was made to promote the activities for prevention of blindness during 1996 to 1998 in the other thirteen counties. The number of eye doctors increased from 602 into 1850. There were two folds increase in the number of equipment availability, for example, slit lamp and ophthalmic microscope. The annual number of cataract surgeries was about 20000.

It appears to be a good approach to create the Model County to promote the prevention of blindness.