Role of lasers in eye care

This review discusses the role of lasers in eye care under five headings: Absorption of laser radiation by ocular tissues. Types of lasers include: ruby, argon, gas, organic dye, krypton, Nd:YAG, excimer, and infrared. Applications of lasers for examining the eye include: laser refraction, determining visual acuity by laser fringes, measuring retinal blood flow, scanning laser ophthalmoscopy and tomography, measuring aqueous flare, ocular holography, measuring retinal absorption, measuring visually evoked potentials, and measuring corneal sensitivity. Applications of laser radiation for ocular surgery include: photocoagulation, destruction of tumors, reattaching the retina, treating glaucoma by producing an iridotomy or by trabeculoplasty or by cyclodestruction. Lasers can be used to remove surface irregularities or superficial opacities from the cornea or eyelids. Other uses are for producing a capsulotomy and for altering corneal curvature as a means of correcting ametropia. Potential adverse effects of laser radiation on the eye are summarized.

Damage to the rainbow trout (Oncorhyncus mykiss) lens following an acute dose of UVB

Rainbow trout (Oncorhynchus mykiss) were used to model the solar radiation-induced cataract that occurs in hatchery-reared lake trout (Salvelinus namaycush). Rainbow trout eyes were exposed to wideband predominantly UVB radiant energy from a filtered 1000W xenon source. Lenticular damage was assessed and classified and comeal damage noted. Lenticular threshold radiant exposure was 0.48 J.cm-2 which is in the same range as the mammalian lens. Permanent lenticular damage occurred at radiant exposure levels approximately twice the threshold for lenticular radiant exposure (also similar to the mammalian response). Slit-lamp and scanning electron microscopical results support the theory of post-exposure anterior subcapsular epithelial cell damage, lens fibre swelling, and eventual rupture, leading to areas of lower refractive index in the anterior subcapsular region of the lens.

Prevalence and cytologic manifestations of human papilloma virus (HPV) types 6, 11, 16, 18, 31, 33, 35, 42, 43, 44, 45, 51, 52, and 56 among 500 consecutive women

The prevalence and associated cytologic manifestations of cervical infection with human papillomavirus (HPV) types 6, 11, 16, 18, 31, 33, 35, 42, 43, 44, 45, 51, 52, and 56 were studied among 500 consecutive women attending the Harborview Medical Center Sexually Transmitted Diseases (STD) Clinic in Seattle, WA. Using radiolabeled-probes without prior amplification of DNA, HPV DNA was detected in cervical specimens from 120 (24%) of the women and was found to be more prevalent than Chlamydia trachomatis (13%), Neisseria gonorrhoeae (12%), or mucopurulent cervicitis (20%). High-risk HPV types 16 or 18 were present alone in 5% of the women; intermediate-risk types 31, 33, 35, 45, 51, 52, or 56 in 3%; and low-risk types 6, 11, 42, 43, and 44 in 5%. In an additional 8% HPV DNA was detected but could be characterized only as being type 6, 11, 16, 18, 31, 33, or 35. Each grouping of HPV types was equally associated with squamous intraepithelial lesions (SILs) of the cervix. In the absence of SIL and koilocytosis, the cytologic changes associated with HPV infection included frequent binucleation and variation in nuclear size and chromatin distribution. Parakeratosis and hyperkeratosis without nuclear atypia were not associated with HPV DNA. The natural history and clinical significance of these HPV-associated lesions remain to be defined.

Protection from acute exposure to ultraviolet radiation by ultraviolet-absorbing RGP contact lenses

One eye in each of 12 female pigmented rabbits was irradiated with UVB while wearing an EqualensR I rigid gas-permeable contact lens. The other eye served as a control. The irradiance level was 625 microW cm-2 (285-315 nm total bandpass) with exposure times up to 2364 s. Eyes were evaluated 24 h and 48 h after exposure by biomicroscopy and pachometry, and later by scanning electron microscopy (SEM). The contact lens was found to protect the central cornea from radiant exposures up to 60 times threshold. The exposed areas of cornea showed characteristic ultraviolet damage with an arc of demarcation indicating the position of the lens. With time the area formed a ridge of damaged cells (confirmed by SEM). At radiant exposure over 0.75 J cm-2 some oedema was seen in the 'protected' region, apparently by extension rather than as a direct effect. These findings suggest that in the human being exposed to ultraviolet radiation this ultraviolet-absorbing RGP lens would permit nasal and temporal photoketatitis with sparing of the central cornea and provide some protection of more posterior ocular structures.

Analysis of the physical state of different human papillomavirus DNAs in intraepithelial and invasive cervical neoplasm

The integration of human papillomavirus (HPV) DNA into the human genome has been generally accepted as a characteristic of malignant lesions. To gain a better understanding of this phenomenon, genomic DNA from 181 cervical biopsy specimens was isolated and analyzed for HPV type and physical state of the HPV genome. These specimens represented the full spectrum of cervical disease, from condyloma to invasive carcinoma. Discrimination between integrated and episomal HPV DNA was accomplished by the detection of HPV-human DNA junction fragments on Southern blots. In most cases in which ambiguous Southern blot results were obtained, the specimens were reanalyzed by two-dimensional gel electrophoresis. Of the 100 biopsy specimens of cervical intraepithelial neoplasia analyzed, only 3 showed integrated HPV DNA, in contrast to 56 (81%) of 69 cervical carcinomas (P less than 0.001) showing integrated HPV DNA. Of the 40 carcinomas containing HPV 16 DNA, 29 (72%) had integrated HPV DNA, of which 8 (20%) also had episomal HPV DNA. In 11 (27%) cancers, only episomal HPV 16 DNA was detected. All 23 HPV 18-containing carcinomas had integrated HPV DNA, and 1 also had episomal HPV 18 DNA. The difference between HPV types 16 and 18 with respect to frequency of integration was statistically significant (P less than 0.01). The results of this study indicate that detectable integration of HPV DNA, regardless of type, occurs infrequently in cervical intraepithelial neoplasia. The absence of HPV 16 DNA integration in some carcinomas implies that integration is not always required for malignant progression. In contrast, the consistent integration of HPV 18 DNA in all cervical cancers examined may be related to its greater transforming efficiency in vitro and its reported clinical association with more aggressive cervical cancers.

UV-B radiation and the optical properties of cultured bovine lenses

The effect of UV-B radiation on the crystalline lens was examined by subjecting bovine lenses in culture to varying low exposures at 300 nm. Lens optical quality was monitored on a long-term basis (to 1000 hrs.) with an automated scanning laser system that recorded both change in relative scatter and focal length across each lens. Data were collected for 20 lens positions at each scan. Radiant exposure levels consisted of 0.5, 0.25, 0.125, 0.06 and 0.03 Jcm-2. Twenty irradiated lenses were compared to twelve untreated controls. All of the irradiated lenses showed changes in scatter and focal length relative to the controls. Most (about 75%) of the treated lenses showed significant increases in scatter (200-400%) and focal length (10-20%) at 40 to 60 hours after exposure. A similar time frame for lens damage was noted by visual inspection. Exposure to UV-B at the above doses did not affect culture longevity.

Acute effects of ultraviolet-B irradiation on the corneal surface of the pigmented rabbit studied by quantitative scanning electron microscopy

The eyes of female pigmented rabbits were exposed to a single dose of UV-B (300 +/- 9 nm, 0.05 J/cm2 total dose) between 13.30 and 15.00 h. The average irradiance was 225 +/- 36 microW/cm2 delivered over 191 to 264 s. At various time periods thereafter (24, 48, 72 and 96 h post-irradiation), the animals were euthanized by pentobarbital overdose and the eyes fixed with 2% glutaraldehyde in 80 mM cacodylate buffer (pH 7.4, total osmolarity of 330-340 mOsm/L). Corneal quadrants were examined by high resolution scanning electron microscopy at 100 X and 500 X at-stage magnification at central, mid-peripheral and peripheral sites. The micrographs from the central cornea were subjected to a quantitative analysis using a computer based digitization system. A peak effect was observed at 48 h at which cellular exfoliation was noted at the corneal apex. In the region immediately adjacent to the exfoliating cells, the number of light and dark electron reflex cells decreased to 48 h while the numbers of medium-reflex cells decreased after 48 h. The relative surface area of all cells was also decreased at 48 h compared to unirradiated controls. Significant recovery was observed by 96 h. Mid-peripheral and peripheral sites were largely unaffected by this just supra-threshold irradiation.

Long-term effects of a single dose of ultraviolet-B on albino rabbit cornea--II. Deturgescence and fluid pump assessed in vitro

Both eyes of female albino rabbits (1.9 kg: 9-10 wk old) were exposed to a single dose of UV-B (300 +/- 9 nm; 0.125 J/cm2 total dose) between 13.30 and 15.00 h. At various time periods thereafter (every 12 h for 3 days, 6, 7, 14, 28, 42, 56, 112, 224 and 336 days post-irradiation), animals were sacrificed, samples of aqueous humor taken for analysis and stroma-endothelium preparations obtained from the corneas. Following such threshold irradiation, small increases in aqueous humor tonicity and protein levels were observed. The preparations were mounted in a specular microscope assembly (for measuring the rate and magnitude of corneal deturgescence) or between two half chambers (for measuring fluid pump) and equilibrated for 2 h with a CO2-equilibrated glucose-adenosine-glutathione-supplemented Ringer solution at 37 degrees C and a hydrostatic pressure of 20 cm H2O. After equilibration the stromal thickness showed large variation with large reductions in both the rate and amplitude of deturgescence function observed by 36 h. Large reductions in fluid pump activity were also observed by 36 h. The magnitude of the effects on fluid pump were somewhat greater than the effects on deturgescence. Both functions recovered to pre-irradiation levels by 112 days post-irradiation.

Physical characteristics and perceptual effects of "blue-blocking" lenses

The transmission-optical properties of a "blue-blocking" lens and its influence on several aspects of human visual performance were assessed. Results showed that the lens was effective in absorbing ultraviolet and blue wavelengths and that its effects on contrast sensitivity and visual evoked potentials (VEP's) were similar to those produced by an equivalent neutral density (ND) filter. Although the lens did not alter stereopsis, it did produce severe color discrimination losses for normal and dichromatic subjects.

Contact lenses and acute exposure to ultraviolet radiation

The eyes of twenty-three pigmented rabbits (weight approximately 2kg) were irradiated with a single dose of UVB (285 to 315 nm total bandpass at approximately 450 muW.cm-2 irradiance) for exposure times of 22s to 1680s. One group wore UV-transmitting soft contact lenses during exposure of one eye with the fellow eye serving as a control while another group wore a UV-absorbing lens on each eye with only one eye irradiated. UV-transmitting contact lenses did not affect the clinical response to UV exposure whereas the UV-absorbing contact lenses protected the corneas as could have been predicted by consideration of the absorption characteristics of the lenses at the experimental waveband. In no case was there any evidence of adhesion between the contact lens and the corneal epithelium.

Long-term effects of a single dose of ultraviolet-B on albino rabbit cornea--I. in vivo analyses

Both eyes of female albino rabbits (1.9 kg) were exposed to a single dose of UV-B (300 +/- 9 nm; 0.125 J/cm2 total dose) between 13.30 and 15.00 h. The average irradiance was 209 +/- 4 microW/cm2 delivered over 612 +/- 13 s. At various time periods thereafter (every 12 h for 3 days, 6, 7, 14, 28, 42, 56, 112, 224 and 336 days post-irradiation), the animals were subjected to a full slit lamp examination to evaluate the status of the cornea and the anterior segment along with optical or ultrasonic pachometry of central corneal thickness. The results were compared with studies on age-matched rabbits over the same time period. In response to the UV-B irradiation, the corneas showed a modest edema (20% increase in central corneal thickness) that peaked at 48 h. Nearly normal central corneal thickness returned in 6 days and followed by a secondary very slight swelling (less than 5%) that resolved by 14 days. The edema was accompanied by keratitis over the same period. Thereafter, both control and UV-B irradiated corneas progressively increased in thickness with age. Biomicroscopy also revealed the appearance of granular opacities in the corneal epithelium that peaked at 72-96 h and resolved over 28 days. In addition, very small microdot opacities of the corneal epithelium were present in the UV-B irradiated corneas that reached maximum at 72 h but persisted to some degree throughout the evaluation period. Biomicroscopy also revealed a progressive disruption of the homogeneous nature of the corneal stroma by the appearance of large 'bread crumb'-like opacities that started at 72 h and was still present at the end of the evaluation period. These results suggest that long-term evaluation of the cornea is important after acute UV-B exposure and indicate that acute exposure to UV-R can produce corneal changes resembling those reported following chronic exposure to UV-R-rich environments.

The influence of contact lens wear on the corneal response to ultraviolet radiation

One eye of each of 15 male pigmented rabbits was fitted with a gas-permeable rigid contact lens. Lenses were worn on a daily basis for an initial period of 7 days with the other eye serving as a control. After this initial period the lenses were removed and both eyes were irradiated with UV-B (305 nm +/- 9 full width half maximum) using either 0.03 J cm-2 or 0.12 J cm-2 which were approximately the epithelial and endothelial damage thresholds for this waveband respectively. The responses of the cornea were followed by microscopy and pachometry. Biomicroscopically there was a dramatic difference in response between contact lens wearing and non-wearing eyes for the higher radiant exposure, whereas little difference was observed at the lower level. For both levels of radiant exposure there was a significantly less corneal thickness increase in contact lens wearing eyes after UV-B irradiation. Recovery patterns were similar.

Optical management of posterior chamber lens tilt

A pseudophakic patient reported blurred vision and diplopia one year after the surgery. We suspected that the origin of both these problems was subluxation of the intraocular lens. His blurred vision was eliminated by a cylindrical spectacle lens at an oblique axis. Monocular diplopia could only be eliminated occasionally. The displacement of the IOL is shown photographically in this report.

Keratopathy with low dose chloroquine therapy

Antimalarial drugs (4-aminoguinolines) are often used as non-steroidal anti-inflammatories and remission inducers in the treatment of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). In this paper we report on ocular signs of aminoquinolinic toxicity among 39 patients, 31 with RA and 8 with SLE. These patients received either chloroquine 250 mg q.h.s. or hydroxychloroquine 200 mg b.i.d. No maculopathy was detected, however 75% of the patients showed various degrees of keratopathy ranging from epithelial haze to dense "whorl" deposits. No correlation was found between severity of the keratopathy and the estimated total amount of aminoquinoline administered.

Ultraviolet-B damages corneal endothelium

Direct in vivo observation of acute ultraviolet (UV)-induced corneal endothelial damage is not possible due to the more severe damage produced in the epithelium. In order to quantify damage and evaluate endothelial recovery an indirect method was used. Eyes of pigmented rabbits were irradiated with UV-B (290 to 320 nm) isolated from the output of a high-pressure 1000 W reflectorized Xenon arc lamp by a grating monochromator and appropriate filters. The peak wavelength of the radiation used was 305 nm, with a 18 nm bandwidth at half-maximum. Corneal thickness variations measured with a modified Zeiss (Oberkochen) pachometer were used to follow alterations in epithelial and endothelial function. Epithelial damage alone resulted in a maximum thickness increase of 13.5% within 24 hr with recovery within a further 24 hr. Greater increases in corneal thickness, in the absence of anterior uveal involvement, were taken to indicate endothelial damage, and reached maximum at 2 days, with recovery occurring in 7 days. The threshold for endothelial damage sufficient to disturb corneal deturgescence was 0.12 J X cm-2.

Determination of infrared radiation levels for acute ocular cataractogenesis

One hundred pigmented rabbit eyes and ten primate eyes were exposed to infrared (IR) radiation in the 715 to 1,400 nm wavelength range and to the full spectrum output from a 5,000 W Xenon high-pressure source. The ocular exposures were evaluated independently with a slitlamp by two researchers and classified for ocular damage. The primary ocular lesions resulting from exposure to IR radiation were corneal, iritic, and lenticular. Corneal damage varied from epithelial haze to epithelial erosion but no endothelial damage was found. The iris showed stromal haze and swelling. Lenticular changes showed small white dots that, occur at the level of the anterior cortex. All lens damage depended on iris involvement. Ocular damage was related to the rate of delivery of the IR radiation since the data show that as the irradiance level increases, the radiant exposure threshold decreases. Exposures for the full spectrum were found to be additive for irradiance levels at 4 W.cm-2 and above. The threshold radiant exposures for the full spectrum of 750 J.cm-2 for the cornea, 1,000 J.cm-2 for the iris, and 2,000 J.cm-2 for the lens were essentially identical to the IR exposure thresholds for the same irradiance levels. The primate threshold radiant exposure was a factor of six above the respective rabbit thresholds.

The ratio of the size of the optic cup (as determined by the place where the vessels deviate) to size of the disc

The vessel deviation to disc ratio (VDR) of the optic nerve head can be defined for a given meridian as the ratio of the size of the cup as indicated by small blood vessel deviation in that meridian to the size of the disc. Thus, VDR is a relative measure similar to cup/disc ratio. The difference between VDR and other methods of measuring cup/disc ratio is that the former identifies the rim of the cup with the deviation or bending of the small blood vessels as they fan out over the disc, whereas the latter determine the location by the other criteria which vary from examiner to examiner. The purpose of this study is to quantify the variation in VDR and its relation to age, refractive error, and sex.

Additive effects of ultraviolet radiation

A 5000 W xenon-mercury high pressure lamp and a double monochromator were used to produce a 3.3-nm half-bandpass ultraviolet (UV) radiation at 295 nm. Pigmented rabbit eyes were irradiated with radiant exposures given in joules per cm2 and ranging from 0.014 to 1.0 J.cm-2 and evaluated by slitlamp biomicroscopy. Corneal threshold (Hc) was 0.05 J.cm-2 and lens threshold (hL) was 0.75 J.cm-2. Other eyes were irradiated with 2 Hc and evaluated from 4 to 24 hr at 4-hr intervals. After a latent period of 4 hr, the corneal response was observed to increase to a maximum by 12 hr. Addition eyes were subjected to repeated Hc and 0.5 Hc followed by Hc exposures with varying intervals between exposures. Corneal damage was only greater than that expected from a single Hc exposure if the separation between the two Hc exposures did not exceed 8 hr. The subthreshold exposures did not sensitize the cornea to later Hc irradiations. The most repeatable and reliable corneal response to these levels of UV was the development of corneal epithelial granules.

Ultraviolet induced lysosome activity in corneal epithelium

A 5,000 W Xe-Hg high pressure lamp and a double monochromator were used to produce a 3.3 nm half-bandpass ultraviolet radiation at 295 nm. Pigmented rabbit eyes were irradiated with radiant exposures from 140 Jm-2 to 10,000 Jm-2 and evaluated by slit-lamp biomicroscopy, light and electron microscopy. Corneal threshold (Hc) was 200 Jm-2 and lens threshold (HL) was 7,500 Jm-2. The most repeatable and reliable corneal response to these levels of UV was the development of corneal epithelial granules. Histological changes included a loss of superficial epithelial cells and selective UV induced autolysis of the wing cells. It is suggested that the biomicroscopically observed granules are the clinical manifestation of the secondary lysosomes revealed by light and electron microscopy. It is proposed that UV breaks down the primary lysosome membranes to release hydrolytic enzymes which in turn form the secondary lysosomes during autolysis. Extreme levels of radiant exposure at 295 nm result in indiscriminate destruction of all layers of the corneal epithelium, but the posterior cornea was spared.

Experimental acute pancreatitis: action of atropine and beta-haloethylamine furoate on muscarine-induced exocrine pancreatic secretion

Intraarterially administered muscarine induced predictable and reproducible experimental acute pancreatitis with a simultaneous increase in amylase levels in blood. Muscarine also caused a transient rise followed by a lowering of blood glucose levels. The stimulated amylase secretion was dose-response related. The guinea pigs survived 2--2 1/2 h after muscarine administration. Atropine (3 and 5 mg/kg), an antimuscarinic agent, injected intraperitoneally 2 h prior to muscarine administration, (a) inhibited muscarine-induced amylase secretion, and (b) marginally increased the survival time of guinea pigs, but could not sustain the animals for further experimentation. The high death rate of experimental animals prevented the use of this method as a model for investigation of experimental acute pancreatitis.

The regression of hypertensive retinopathy

The detection of severe hypertensive retinopathy in a relatively symptomless 30-year-old white female contact lens patient is reported. The regression is documented during subsequent antihypertensive therapy. The retinopathy resolved uneventfully despite fluctuating blood pressure.