Unoperated Eyes Research Articles

Diode Array as Fixation Light to Reduce Unwanted Globe Movements

In ocular surgery complications can occur from eye movements during topical anesthesia or insufficient retrobulbar anesthesia. To minimize eye movements during surgery a fixation light was designed consisting of a diode array embedded in an eye patch, and a keyboard, which will be positioned on the patient’s thorax. The patient focuses with the unoperated eye at a flashing diode which is part of the diode array. The operated eye is guided by conjugated eye movements. With the keyboard, the surgeon can change the diode signal all over the array. As a result, the eye is kept still or moved in the appropriate direction to facilitate the surgical process. The flat and lightweight design of the device enables its use under sterile surgical covers or in an upright position of the patient during laser applications.

Bilateral Retinal Venous Caliber Decrease Following Unilateral Optic Nerve Sheath Decompression

Abstract We investigated retinal vascular changes in nine patients undergoing optic nerve sheath decompression for vision-threatening papilledema associated with pseudotumor cerebri. Two major (one superior and one inferior) retinal venous and arterial calibers were measured before and 1.1 +/- 0.1 months, 3.2 +/- 0.2 months, 5.0 +/- 0.2 months, 7.6 +/- 0.2 months, and 13.0 +/- 1.9 months after surgery. The retinal venous caliber decreased significantly, and the decrease progressed until 3.2 months after surgery. The venous caliber in the contralateral unoperated eyes also decreased significantly. The decrease in the venous caliber in the contralateral unoperated eye as well as in the operated eye following the surgery supports the hypothesis that slow filtration is the mechanism of successful optic nerve sheath decompression. Retinal venous caliber measurement, in either the operated eye or the unoperated fellow eye, can be used to quantitatively monitor the status of papilledema associated with pseudotumor cerebri.

Long-term prognosis of extracapsular cataract extraction and intraocular lens implantation in diabetic patients

Although cataract extraction with intraocular lens implantation (IOL) is being used for increasing numbers of patients, there is still insufficient information regarding the long-term outcome for these patients. In this retrospective study of 140 eyes of 102 patients, 97 eyes (69%) achieved a best visual acuity of 20 40 or better. After a minimum 6-month postoperative period, 26 eyes (19%) had developed retinopathy: eight eyes progressed from nonproliferative to proliferative retinopathy. Glycosylated hemoglobin levels and fasting blood glucose were significantly higher at time of surgery in the eight that progressed than in those who did not ( P = 0.002, P = 0.034). There were 65 unilateral IOL implantations; in 10 (15%) of these eyes, retinopathy progressed. Retinopathy also progressed in 70% of the fellow eyes of these patients. In patients whose retinopathy did not progress, 95% of the fellow eyes also showed no progression. Also, patients with progression in the pseudophakic eye frequently had progression in the fellow unoperated eye. Postoperative progression was symmetrical ( P = 0.0001). Our analysis suggests that progression of diabetic retinopathy following IOL implantation can be correlated to diabetic control at the time of surgery.

Disparity between refractive error and visual acuity after photorefractive keratectomy: Multifocal corneal effects

Purpose: To determine the relationship between postoperative refractive error and uncorrected visual acuity (UCVA) after photorefractive keratectomy (PRK) and compare the results to those in unoperated control eyes with different degrees of myopic refractive error.Setting: Academic cornea and refractive surgery subspecialty practice.Methods: Uncorrected visual acuity and manifest refraction were recorded for 52 consecutive patients who had PRK for myopia. Eight control eyes that did not have PRK and in which artificial myopia was induced were also studied to ascertain the association of UCVA with myopia in untreated eyes. Uncorrected visual acuity in postoperative eyes was compared with that in control eyes.Results: Of the 46 eyes with a myopic spherical equivalent postoperative refraction, 44 (96%) had better UCVA than control eyes with equivalent myopic refractions. Twelve of 13 (92%) eyes with refractions of −1.00 diopter or more had a UCVA of 20/40 or better.Conclusion: After excimer laser PRK, patients achieved better Snellen visual acuity than might be expected from their residual refractive error, perhaps as a result of a multifocal postoperative corneal topography. Nonuniformity of the corneal surface following PRK may create “focal areas of emmetropia” that allow patients to achieve better visual acuity than the refraction may predict.

Effect of mitomycin C on the optic nerve in rabbits

AIMTo prevent scarring after surgical optic nerve sheath decompression, it has been suggested that treating the area of fenestration with mitomycin C (MMC) might be effective. An animal model was...

Cell size in the lateral geniculate nucleus of cats reared with esotropia and sagittal transection of the optic chiasm

We have attempted to investigate the role of extraretinal influences in controlling visual system development by rearing cats with esotropia in combination with sagittal transection of the optic chiasm. This combination leave two intact A 1 laminae, one innervated by the deviated eye and one innervated by the unoperated eye and thus minimizes the contributions of retinally mediated influences. Cell size measurements in the dorsal lateral geniculate nucleus revealed that the neurons in the A 1 lamina innervated by the deviated eye were, on average, 10–15% smaller than their counterparts in the contralateral A 1 lamina.

Experimental Erbium: YAG Laser Photoablation of Trabecular Meshwork in Rabbits: An in-vivo Study

Photoablative laser trabecular surgery has been proposed as an outflow-enhancing treatment for open-angle glaucoma. The aim of the study was to investigate the time course of repair response following low-thermal Erbium: YAG-laser trabecular ablation.In 20 anaesthetized rabbits gonioscopically controlled ab-interno photoablation of the ligamenta pectinata and underlying trabecular meshwork (TM) was performed with a single-pulsed (200 μs) Erbium: YAG (2.94 μm) laser. The right eye received 12–15 single laser pulses (2 mJ) delivered through an articulated zirconium fluoride fiberoptic and a 200 μm (core diameter) quartz fiber tip, the left unoperated eye served as control. At time intervals of 30 minutes, 2, 10, 30, and 60 days after laser treatment, eyes were processed for light- and scanning electron microscopy.The applied energy density of 6.4 J cm−2resulted in visible dissection of the ligamenta pectinata and reproducible microperforations of the TM exposing scleral tissue accompanied by blood reflux from the aqueous plexus. The initial ablation zones measured 154±36 μm in depth and 45±6 μm in width. Collateral thermal damage zones were 22±8 μm. At two days post-operative, ablation craters were still blood- and fibrin-filled. The inner surface of the craters were covered with granulocytes. No cellular infiltration of the collateral thermal damage zone was observed. At 10 days post-operative, progressive fibroblastic proliferation was observed, resulting in dense scar tissue formation with anterior synechiae, proliferating capillaries and loss of intertrabecular spaces inside the range of former laser treatment at 60 days post-operative. Trabecular microperforations were closed 60 days after laser treatment in all rabbits. IOP in treated and contralateral eyes did not significantly change its level during whole period of observation. Low-thermal infrared laser energy with minimal thermal damage to collateral structures could not effectively prevent early scarring of trabecular surgery in rabbits.

Neodymium:YAG laser lens ablation in a rabbit model

Purpose: To assess the safety of neodymium:YAG (Nd:YAG) laser lens ablation in a rabbit model prior to human investigation.Methods: The Nd:YAG laser lens ablation probe was inserted into the anterior chamber of 14 New Zealand white rabbit eyes and Nd:YAG laser lens ablation was simulated, exposing the eyes to energy significantly higher than that used in previous experimental Nd:YAG lens ablation of the human crystalline lens. After the procedure, the rabbits were killed at 1 hour, 1 day, or 1 week and the eyes evaluated by specular microscopy, ultrasonic pachymetry, and light microscopy.Results: There was no statistically significant difference in the postoperative endothelial cell counts or ultrasonic pachymetry of study eyes and control (unoperated) eyes. Light microscopy revealed no apparent damage to the cornea, trabecular meshwork, or retina of the study eyes.Conclusions: The Nd:YAG laser lens ablation device appears to be a safe method of cataract removal in this animal model. Further study is needed to determine the safety and efficacy of this device for cataract removal in humans.

Eye growth in the aphakic newborn rabbit

Purpose:To examine eye growth in unilaterally lensectomized newborn rabbits.Setting:S:t Erik Eye Hospital, Karolinska Institute, Stockholm, Sweden.Methods:Unilateral lensectomy was performed in 18 randomly selected 23-day-old rabbits. Corneal incision was performed in 2 other rabbits, and the aqueous humor was replaced with balanced salt solution in one eye. Axial length, corneal diameter, corneal thickness, intraocular pressure (IOP), and refraction were measured in all eyes preoperatively and 1, 2, and 3 months postoperatively. The wet mass of the after-cataract was measured 3 months after surgery.Results:The growth of the aphakic eye, as indicated by axial length and corneal diameter, was significantly less than that of the control eye in 14 rabbits. No significant difference in IOP or corneal thickness was found between the lensectomy and control eyes. Four animals had elevated IOP with secondary glaucoma and were excluded from the study. No difference in eye growth was found between the two eyes when no lensectomy was performed. Refraction in the unoperated eye showed a myopic shift. After lensectomy, the operated eye became hyperopic with a myopic shift 3 months after surgery. No correlation was found between eye growth and the wet mass of the after-cataract.Conclusions:Our results suggest that removal of the rabbit crystalline lens at an early age reduces eye growth.

Scheimpflug anterior segment photography assessment of wound healing after myopic excimer laser photorefractive keratectomy

Purpose: To describe a method for analyzing Scheimpflug anterior segment images for a new measure of the cornea's response to excimer laser photoablation.Setting: Mericos Eye Institute, Scripps Memorial Hospital, La Jolla, California.Methods: Digitized Scheimpflug anterior segment photographs of operated and unoperated eyes were obtained in 17 patients 1 to 15 months after photorefractive keratectomy (PRK). The images were analyzed to determine their dimensions. Each imaged opacity was compared with corneal haze observed by slitlamp biomicroscopy, intended ablation depth, postoperative corneal thickness, and refractive error change.Results: All postoperative corneas displayed a nonhomogeneous, meniscus-shaped pattern in the ablated area that ranged from 17 to 40% of corneal thickness. This pattern correlated poorly with intended laser ablation depth.Conclusion: This technique provides a new assessment of corneal response to PRK. Improvements in software analysis may facilitate quantitative assessment.

Night vision testing in unoperated eyes.

We previously described a simple test which evaluates image degradation in post-excimer laser (PRK) patients under scotopic conditions. After refractive surgery, corneal haze, ablation zone decentration, ablation zone/pupillary diameter disparity, and under-correction each result in a characteristic pattern on the Night Vision Recording Chart. Using the same method, further studies evaluated night vision image degradation in 118 un-operated emmetropic, myopic, hyperopic, and astigmatic eyes and in 26 contact lens wearers. Scotopic image degradation increases with myopic refractive error, image displacement increases with astigmatism, and contact lens wearers have more image degradation that with spectacle correction. Our Night Vision Recording Chart offers a simple, reproducible method to characterize image degradation under scotopic conditions.

Photorefractive keratectomy following radial keratotomy.

Excimer laser photorefractive keratectomy (PRK) has been used to correct residual myopia in eyes that have had refractive keratotomy. Nine eyes of eight patients were studied at a mean of 13 months after PRK. Previous procedures included radial keratotomy (9 eyes) and myopic keratomileusis (1 eye). PRK was performed using a Summit Technology excimer laser with a 5.0-mm diameter ablation zone. Uncorrected visual acuity improved in 7 of 9 eyes. The refractive outcome was within 1.00 diopter (D) of attempted correction for 3 of 9 eyes. Spectacle-corrected visual acuity decreased 2 or more Snellen lines in 2 of 9 eyes. Subepithelial corneal stromal haze was seen 1 month postoperatively in 6 of 8 eyes and was present in 4 of 6 eyes at 1 year. Stromal haze was associated with regression of the refractive effect of the PRK. PRK in eyes with previous radial keratotomy appears to be less predictable and may be associated with greater corneal haze and regression of refractive correction than in previously unoperated eyes. Activation of stromal fibroblasts in the previous corneal incisions may cause these findings.

Effect of squint surgery on pupillary diameter.

To investigate the effect that squint surgery has on pupillary diameter. The effect of squint surgery on pupil size was investigated in 19 patients. A significant mydriasis in the operated eye was observed when compared with the unoperated eye. This was independent of the number or type of extraocular muscles operated upon. It is hypothesised that this change in pupillary diameter results from the release of neurotransmitters from tissues damaged during surgery.

4112 Confocal microscopic and histological evaluation of long-term corneal endothelial cell transplantation

This report describes the clinical course, refractive changes, confocal microscopic and histological evaluation of corneal endothelial cell transplantation in rabbits with long-term follow-up. Transplantation of corneal endothelial cells using a cell/carrier device was performed in 19 rabbits. Clinical evaluation between 1-25 months included slit-lamp examination, keratometry, retinoscopy and surface topography. Two grafts in rabbits with 12 and 24 month survivals were evaluated in vivo by 3D tandem scanning confocal microscopy. The same grafts were then processed for transmission electron microscopy. BrdU labeling of the grafted cells in one transplant was performed in order to distinguish between host and grafted endothelial cells. All grafts cleared and remained clear for an average of one year without signs of rejection or inflammation. Postoperative refraction data and topography of the transplants showed progressive development of myopia and steep corneas compared to the unoperated eyes in each case. Confocal microscopy in vivo demonstrated a regular hexagonal pattern of the transplanted endothelial cells and a thickened Descemet's membrane, which correlated with the light and electron microscopic findings. BrdU labeling of the grafted endothelial cells showed a homogenous labeling of cell nuclei 6 months after the transplantation. This study demonstrates that corneal endothelial cells grown on a biomaterial can be replaced and remain functional for a long period of time.

Phenomenal motion seen through artificial intra-ocular lenses.

In an experiment on the human brain using the technique of positron emission tomography (Zeki et al . 1993), we showed that when a subject sees motion in the rings constituting Leviant’s Enigma figure (see figure 1), there is significant increase in regional cerebral blood flow. This increased blood flow occurs in the region of human area V5, specialized for visual motion, and partly overlaps that area. On the basis of this result, we concluded that it is activity in specific visual areas of the cerebral cortex which endows Enigma with the phenomenal property of motion which is not objectively there. This conclusion was criticized by Gregory who thought that the motion is due to the hunting of accomodation in the eye, and is thus generated by the eye and has little to do with the cerebral cortex. Since then I have conducted experiments to answer Gregory’s points and refute his arguments (Zeki 1994). In an editorial in Perception , Gregory (1994) has now made an excellent suggestion which I have seized upon. One way of resolving the issue, Gregory suggests, is to ask subjects with an intra-ocular lens implant or no lens at all whether they can see the motion in the Enigma figure. Gregory remains vague about the motion: he speaks of shimmers and moire patterns. I, on the other hand, am concerned with the most distinctive feature of Enigma , namely the rapid circular motion that is confined to the rings and that reverses direction with prolonged viewing. Mr Timothy ffytche FRCS, ophthalmologist, agreed to consecutively show the Enigma figure to three patients who had had both lenses removed and replaced with implants. (These patients had lost the mechanism for accomodation and therefore, if they could detect the motion in the rings, the explanation must lie elsewhere than in the ‘hunting of accommodation’ favoured by Gregory.) In fact, the result was quite conclusive: without prompting, the patients rapidly referred to motion in the rings. Confidence in their observation was heightened by the fact that they spontaneously described the motion as reversing direction, which is what also happens when normal observers view Enigma . In addition to this, I had the opportunity to present this same figure to a patient who had had the same operation in one eye only, two weeks before. When viewing this figure through the eye with a replacement lens, he commented spontaneously on the motion in the ring (‘especially the outer ring’) and reported seeing much the same thing when he viewed the figure through the unoperated eye.

Bilateral Retinal Venous Caliber Decrease Following Unilateral Optic Nerve Sheath Decompression

We investigated retinal vascular changes in nine patients undergoing optic nerve sheath decompression for vision-threatening papilledema associated with pseudotumor cerebri. Two major (one superior and one inferior) retinal venous and arterial calibers were measured before and 1.1 +/- 0.1 months, 3.2 +/- 0.2 months, 5.0 +/- 0.2 months, 7.6 +/- 0.2 months, and 13.0 +/- 1.9 months after surgery. The retinal venous caliber decreased significantly, and the decrease progressed until 3.2 months after surgery. The venous caliber in the contralateral unoperated eyes also decreased significantly. The decrease in the venous caliber in the contralateral unoperated eye as well as in the operated eye following the surgery supports the hypothesis that slow filtration is the mechanism of successful optic nerve sheath decompression. Retinal venous caliber measurement, in either the operated eye or the unoperated fellow eye, can be used to quantitatively monitor the status of papilledema associated with pseudotumor cerebri.

Acute Corneal Hydrops in Keratoconus

To determine the clinical factors associated with the development of acute corneal hydrops and its subsequent outcome. The authors identified 147 eyes (124 patients) with acute hydrops from a database of 5242 eyes (2723 patients) with keratoconus. They compared the clinical features of patients in whom hydrops developed with unaffected patients and assessed the progression to penetrating keratoplasty by actuarial methods. Patients in whom acute hydrops developed tended to be younger males who had advanced corneal ectasia and a poor corrected Snellen visual acuity at the diagnosis of their keratoconus (P < 0.001). Acute hydrops also was more common in the presence of severe allergic eye disease (P < 0.001). The development of hydrops was a very significant risk factor for subsequently receiving a penetrating keratoplasty (P < 0.00001) and at the end of the study period 87 (59%) of the 147 eyes had surgery for visual rehabilitation. These eyes had a greater rate of graft rejection than eyes grafted without hydrops (P = 0.02). After resolution of the hydrops, 46 of the 60 unoperated eyes had been refitted with contact lenses, of which 28 (61%) achieved a Snellen visual acuity of 20/40 or better, although a better visual acuity often was present in the contralateral eye. Microbial keratitis developed in two of these eyes after refitting. Although a penetrating keratoplasty often is indicated for visual rehabilitation after acute corneal hydrops, there is an increased rate of rejection. Only a minority of eyes were re-established in contact lenses after resolution of hydrops, but some patients achieved a functional level of visual acuity such that the procedure could be delayed or avoided.

Continued Endothelial Cell Loss Ten Years after Lens Implantation

To investigate the effects of cataract extraction and lens implantation on the central corneal endothelium 10 years after surgery. The authors conducted a prospective study of 253 consecutive eyes that underwent cataract extraction with or without lens implantation by one surgeon from 1976 to 1982. Three types of lens implant were used during this period. The protocol included ophthalmic examinations and specular microscopy on all eyes preoperatively, and 2 months and 1, 3, 5, and 10 years postoperatively. The 10-year analysis was conducted on 67 (26%) of the 253 total eyes. The remaining patients died (86 eyes [34%]), were unable to return 10 years later (93 eyes [37%]), or had secondary implants (5 eyes [2%]) or penetrating keratoplasty (2 eyes [1%]). There were no statistically significant differences among the median 10-year endothelial cell losses of 36% in 17 control cataract extractions without lens implantation (15 extracapsular and 2 intracapsular), 40% in 15 medallion iris suture implants, 32% in 28 transiridectomy clip implants, and 32% in 7 posterior chamber implants. The median exponential rate of chronic cell loss from 1 to 10 years after surgery was 2.5% per year, which did not differ significantly among the three implant groups or between the implants (2.4% per year) and controls (2.7% per year). The chronic cell loss rate was significantly higher (7.2% per year) in six eyes with cornea guttata, which was the only preoperative endothelial morphologic feature that was significantly associated with the chronic cell loss rate. Ten years after cataract extraction, eyes continued to lose endothelial cells from the central cornea at a rate of 2.5% per year, 2.5 to 8.0 times the rate in healthy unoperated eyes. The rate was not affected significantly by the presence of the three types of lens implants that the authors used. Postoperative eyes with cornea guttata continued to lose cells at more than twice this rate. Preoperative specular microscopy did not provide additional information helpful in predicting postoperative endothelial status or outcome.

Change of eye muscle sarcomeres according to eye position.

In three monkeys, the right eye was moved from the primary position to a position of 30 degrees to 45 degrees exotropia by suturing the globe to the orbital wall. In two animals perfused immediately following suturing, histological examination showed the medial rectus and its sarcomeres to be lengthened and the lateral rectus and its sarcomeres to be shortened as compared to those of the unoperated control eye. In the third monkey, after exotropia was maintained for 2 months, the muscle lengths changed but the sarcomere lengths were similar to those of the control eye. We interpret this to indicate addition of sarcomeres to the lengthened medial rectus and removal of sarcomeres from the shortened lateral rectus. This adaptation to conform muscle length to eye position may explain the altered eye position which persists following periods of eye deviation due to muscle paralysis, prior surgery, injury, or botulinum toxin treatment.

Prognostic Factors for the Progression of Keratoconus

The progression of keratoconus to a stage where penetrating keratoplasty (PK) is required for visual rehabilitation has considerable implications for affected patients. To assist with counselling, the authors have attempted to identify which factors measurable early in the course of the disease may indicate the likelihood of subsequent surgery. The authors reviewed the records of all patients who attended a single center over a 7-year period for contact lens management of their keratoconus. The influence of clinical variables on the time taken for the worst eye to progress to PK was evaluated by actuarial methods and multivariate analysis. Included in the study were 2723 patients with a mean follow-up for unoperated eyes from the first visit of 4.5 years (range, 3 months to 28 years). Data were available for multivariate analysis in 2363 patients. At the end of the study period, 757 eyes (21.6% of all patients) had been grafted. The number of eyes progressing to PK was independently related to both the maximum and minimum keratometry, a corneal cylinder of more than 1.9 mm, the Snellen acuity, the racial group (P < 0.0001), and the age at presentation (P = 0.0006). Sex, laterality, systemic atopic disease, maternal or paternal age at birth, joint hypermobility, and a family history of keratoconus were not statistically related to outcome. Progression to PK in one eye increased the risk of progression in the contralateral eye (P < 0.0001) and a linear model of disease progression is proposed. Several clinical variables can be measured in patients at the presentation of keratoconus that influence the probability of a subsequent PK.