Intraocular pressure measurement after DSAEK by iCare, Goldmann applanation and dynamic contour tonometry: A comparative study

PURPOSE

Corneal thickness inevitably increases following Descemet's stripping automated endothelial keratoplasty (DSAEK), owing to the addition of a donor graft. The current study compares different devices in assessing post-DSAEK intraocular pressure (IOP).

METHODS

We compared IOP values measured by the Goldmann tonometry (GAT), iCare rebound tonometry (iCare) and Pascal dynamic contour tonometry (PDCT) in eyes following DSAEK. Agreement between measurements was calculated with correlation analysis and Bland-Altman plots. Effects of keratometry, central, thickness (CCT), endothelial cell density (ECD) and axial length on IOP measurements were assessed with Pearson's correlation.

RESULTS

Twenty eyes of 20 patients (mean age 74.3±14.4, 14 females) post-DSAEK were included in this study. There was a high concordance between the IOP readings obtained by the three devices: a strong and significant correlation was found between GAT and PDCT (r=0.94, P<0.001) GAT and iCare (r=0.86, P<0.001) and iCare with PDCT (r=0.81, P<0.001). However, the iCare measurements were significantly and consistently lower than that obtained with GAT (ΔIOP=1.68±2.0, P=0.002, 95% CI: 0.7-2.6) and with PDCT (ΔIOP=1.61±2.5, P=0.01, 95% CI: 0.4-2.8). CCT, ECD, CCT, AXL, corneal curvature or astigmatism did not influence IOP measurement by any instrument.

CONCLUSIONS

IOP measurement with three different techniques (applanation, rebound and dynamic contour) showed good correlations, despite an increased corneal thickness following DSAEK. However, the iCare, which is based on a rebound tonometry showed significant lower IOP then the two other methods. This should be taken into account when evaluating patients post DSAEK.

Inadvertent intravitreal gentamicin injection

PURPOSE

To describe the management and consequences of an accidental injection of gentamicin in the vitreous.

METHODS

A retinal detachment developed in a 70-year-old male. During a vitrectomy operation, gentamicin (20mg) was accidentally injected in to the eye. The surgeon immediately began vigorous lavage of the vitreal cavity with balanced salt solution.

RESULTS

No toxic signs appeared after the operation, despite the devastating consequences described in previous reports.

CONCLUSIONS

The immediate vigorous lavage may have reduced the concentration of the toxic material and its consequences.

Pulsatile ocular blood flow in diabetic retinopathy

PURPOSE

To assess circulatory properties of eyes with progressive stages of diabetic retinopathy.

METHODS

The intraocular pressure, pulse amplitude (PA) and pulsatile ocular blood flow (POBF) were measured with a pneumatonometer (OBF Labs UK Ltd). The eyes were grouped: (a) normal control, n = 26, (b) diabetes with no observable diabetic retinopathy (NDR), n = 18, (c) mild to moderate non-proliferative diabetic retinopathy (NPDR), n = 20, and (d) very severe pre-proliferative and proliferative diabetic retinopathy (PPDR/PDR), n = 12.

RESULTS

The PA and POBF values were lower than normal values in the earliest stage (NDR). The POBF increased but was still below normal levels at the NPDR stage, and then increased to an above normal level in the PPDR/PDR stage of diabetic retinopathy. The PA was at normal levels in these later two stages.

CONCLUSION

An initial decrease in pulsatile ocular blood flow is present with the onset of diabetes where no diabetic retinopathy has yet occurred. Subsequently, the pulsatile ocular blood flow increases with the severity of the retinopathy.

Total internal reflection of laser light in eyes filled with silicone oil

BACKGROUND AND OBJECTIVES

This is the first report of clinical settings in which total internal reflection of laser light in eyes filled with silicone oil was observed. The authors analyze this phenomenon and outline the potential hazards it may present to patient, surgeon, and operating room personnel.

MATERIALS AND METHODS

The authors observed significant reflection of laser light off the silicone-water interface both intraoperatively and in the clinic. The critical angle according to Snell's law (i.e., the angle at which total internal reflection occurs at the interface between silicone oil and vitreous) was calculated. The critical angle was found to be 71.9691 degrees(72 degrees).

RESULTS

An analysis of each of the clinical conditions where this phenomenon was observed is presented. Clinical and surgical implications are discussed.

CONCLUSIONS

The hazard of total internal reflection of laser light in eyes filled with silicone oil should be recognized by ophthalmologists to avoid possible complications. Techniques for overcoming and circumventing the difficulties resulting from this phenomenon are proposed.

Managing inferior zonule tears during manual extracapsular cataract extraction

We describe a new technique for safely concluding manual extracapsular cataract extraction in the presence of a rupture of the interior zonules. A lens glide is inserted in the anterior chamber. The tip of the glide is placed in the inferior part of the capsular bag, pushing it toward the ciliary sulcus at 6 o'clock. The extraocular part of the glide is sutured to the sclera to prevent its displacement during manipulation of the eye. The glide spreads the rolled inferior capsule, allowing aspiration of retained cortical material and in-the-bag intraocular lens implantation. The glide is then removed. This technique was used in 12 eyes with pseudoexfoliation in which the complication occurred. No vitreous loss, lens displacement, or other intraoperative or postoperative complications were observed.

Nucleus fragmentation in a scleral pocket for small incision extracapsular cataract extraction

We present a technique for planned manual extracapsular cataract extraction (ECCE) incorporating a modification of mini-nuc ECCE in which the scleral tunnel is made wide enough to allow a nucleus of any size to settle in the tunnel. A 5.0 mm, inverted-V chevron incision is used in which the exposed part of the nucleus lodged in the scleral pocket can be manually picked and fragmented until it is small enough to be removed through the incision. The chevron incision is flexible enough to allow a medium-sized nucleus to be extracted without fragmentation and implantation of a rigid 6.0 mm poly(methyl methacrylate) lens. Vector analysis of preoperative and 3 month postoperative keratometric results in 30 patients showed that the surgically induced vector was 0.54 diopter (D) +/- 0.58 (SD). Mean reduction in astigmatism was 0.08 +/- 0.39 D. The sutureless technique is fast and safe, allows a nucleus of any size to be extracted through a constant size 5.0 mm incision, and results in minimal postoperative astigmatism.

Role of blood components in ocular silicone oil emulsification. Studies on an in vitro model

PURPOSE

To develop an in vitro model for silicone oil emulsification and to explore the blood components involved in this process.

METHODS

The capacity of various blood components to support silicone oil (1000 CS) emulsification was studied by applying 0.5 ml oil on top of 0.5 ml saline containing various blood components. Each tube was sonicated for 150 seconds and centrifuged at 5000 g for 20 minutes. Three phases were noted in the tube: At the top was clear silicone oil, in the middle was emulsified silicone oil, and at the bottom was aqueous solution. The tubes were photographed, and the percentage of the phase length containing emulsified silicone oil (middle) of the total length of the three phases was calculated from the projected image of each tube.

RESULTS

Emulsified silicone oil in plasma or serum was initiated after 100 seconds of sonication and quickly reached maximum (approximately 80%) at 120 seconds. The size of these oil droplets prepared in vitro was 0.0467 +/- 0.028 mm, closely resembling that observed in oil samples removed from a patient's anterior chamber (0.038 +/- 0.018 mm). Under these conditions, silicone oil emulsified in the presence of whole blood cells occurred only at a concentration of 120 micrograms protein/ml; in the presence of red blood cell membranes, it occurred at a concentration of 60 micrograms protein/ml. Lipoprotein-deficient serum failed to support emulsification; however, samples of high-density lipoprotein and low-density lipoprotein supported this process. Purified high-density lipoprotein-apolipoproteins supported oil emulsification. The addition of phosphatidylcholine further enhanced this process, but phosphatidylcholine alone failed to support emulsification.

CONCLUSIONS

A simple and fast in vitro model to study factors affecting silicone oil emulsification was developed. Using this model, red blood cell membranes, plasma lipoproteins, and purified HDL-apolipoproteins supported silicone oil emulsification. Lipids did not, but they had the capacity to enhance the apolipoprotein-supported emulsification.

Safe method for cleaning the posterior lens capsule

Cleaning the posterior capsule is an important step in cataract microsurgery to prevent early postoperative visual impairment. A simple method for cleaning posterior lens capsule opacities during extracapsular cataract extraction is described. A straight 20-gauge cannula with a 0.3 mm anterior aspiration port, attached to a syringe with the piston removed, allows safe polishing in a deep anterior chamber. The described procedure has been safely performed in more than 300 operations.

Angiogenic activity of vitreous extract obtained from rabbit eyes with endotoxin-induced uveitis

The effect of rabbit vitreous with endotoxin-induced uveitis was investigated for its role in the modulation of rat corneal neovascularization (NV). Elvax pellets implanted into at cornea contained either uveitic vitreous, intact vitreous or Elvax alone. The latter two kinds of pellets did not elicit NV. Uveitic vitreous pellets caused, in 100% of eyes, a persistent NV with maximal growth on the 10th day post implantation. Prostaglandin E2 and leukotriene B4 levels in the uveitic rabbit vitreous at 36 h postendotoxin injection were 7- and 5-fold higher than baseline, respectively. Histopathologically, the neovascularized cornea showed a significant inflammatory reaction attributable to the uveitic vitreous extract.

Methylcellulose as a contact lens irrigant when silicone oil is used in vitreoretinal surgery

When silicone oil, a hydrophobic agent, is injected into the vitreous cavity during the course of vitrectomy operations, often some escapes outside the eye, and a mixture of oil and water forms under the infusion contact lens, markedly interfering with visibility. We found that a viscous solution of methylcellulose 1.75% in saline used as the infusion contact lens irrigant, instead of a saline solution alone, can prevent silicone oil from entering under the contact lens, thus avoiding this difficulty.

Long-term follow up of accidental parafoveal laser burns

The findings after 12 years of follow-up evaluation of 2 patients who sustained accidental parafoveal and juxtafoveal Nd:YAG laser injuries are reported. In both cases, the fovea was not destroyed by the initial insult and early scar formation. Both cases demonstrated, after more than a decade, minimal visual deficit without significant late complications. In spite of early decrease in visual performance, the long-term prognosis for Q-switched Nd:YAG laser retinal lesions in which the fovea was not directly involved in the injury or its repair mechanisms is relatively benign.

Cataract extraction in eyes filled with silicone oil

A surgical technique for cataract extraction in eyes filled with silicone oil was developed that has two major objectives: removal of the entire cataractous lens and complete preservation of the silicone oil volume. A regular extracapsular cataract extraction or phacoemulsification is performed, and the incision is closed with the final sutures. All steps are performed under continuous positive pressure achieved with an anterior chamber maintainer connected to a bottle of balanced saline solution. An inferior basal iridectomy is created with a vitrectomy probe, and the posterior capsule is then slowly pulled out through the limbal incision with intraocular forceps, again under positive pressure, in an eye that is actually a closed system, without any loss of silicone. This step results in transformation of the extracapsular cataract extraction condition into an intracapsular cataract extraction condition. The described technique was successfully performed in nine eyes. In the younger patients, the whole procedure was completed through two very small limbal openings.

Self-inflicted ocular mutilation in the pediatric age group

Three mentally retarded children with severe self-inflicted ocular injuries are presented. All three suffered from severe ocular injuries including retinal detachment resulting in progressive visual loss and even blindness. Self-inflicted injuries to the eyes, including self enucleation, is an extremely uncommon form of behavior, rarely encountered by pediatricians. The risk of ocular morbidity is high if the diagnosis is overlooked. Technical advances in ophthalmology permit much improvement in some formerly hopeless cases of ocular self-mutilation, but there is still no accurate method to repair destroyed retinal or nervous tissue. Early identification of patients at risk of ocular self-mutilation is essential in order to prevent or minimize such severe ocular injuries.

Transient fluorescein leakage simulating subretinal membrane: a diagnostic dilemma

A 68-year-old woman with blurred vision had a foveal spot of fluorescein leakage that later was found to be a transient leakage. The clinical picture resembled central serous chorioretinopathy, a rare diagnosis in older patients. Other possible diagnoses (e.g., subretinal neovascular membrane or epiretinal membrane) are discussed as is the need for laser treatment.

Continuous control of intraocular pressure in pseudophakic retinal detachment surgery

We describe a method for continuous control of intraocular pressure in pseudophakic retinal detachment surgery done shortly after extracapsular cataract extraction and posterior chamber intraocular lens implantation. The system consists of a special needle inserted into the anterior chamber through the corneal limbus. The needle is attached by a regular intravenous administration set to an infusion bag. This allows fluids to exit the eye when the eyeball is compressed and to return to the eye when pressure on the eye is released. The presence of an intact posterior capsule and an intraocular lens do not impose a significant barrier to the passage of fluids between the anterior chamber and the vitreous cavity. Using this technique, intraocular pressure can be stabilized throughout the operation. The implementation of this system is demonstrated by a case report.

[Treatment of retinal detachment with intraocular expandable gas injection]

The injection of expandable gas into the vitreous is a new method for treating retinal detachment. The injected gas bubble seals the retinal break and allows absorption of subretinal fluid. In 12 patients, in all eyes treated by injection of sulfur hexafluoride, the detached retina became reattached. In 3 eyes (25%) detachment recurred. To achieve attachment again, both vitrectomy and the circling band operation were performed in 2 of them, and only the latter operation in the third. Risk factors for redetachment included detachment of the macula, retinal detachment larger than 5-o'clock-hours, and pseudophakia. Proper selection of patients for gas injection is most important.

Immediate retinal adhesion by CO2 laser irradiation using a fiberoptic intraocular probe

Using an experimental fiberoptically guided CO2 laser system, we produced lesions on fresh bovine retinas. These lesions were shown to achieve immediate measurable chorioretinal adhesion. This model provides preliminary data on the use of a fiberoptic CO2 laser probe to produce chorioretinal lesions and possible future use in intraocular surgery for retinal detachment. The advantages of using CO2 laser energy are minimal damage surrounding desired lesion and its versatility as a coagulator and cutter. With modifications, CO2 endolaser may have a role in intraocular surgery.

Axial length and scleral thickness effect on susceptibility to glaucomatous damage: a theoretical model implementing Laplace's law

Laplace's law relates the pressure inside a hollow sphere with its radius and the tension in its walls. A theoretical model implementing Laplace's law in the eye globe is presented. The physical model may help to explain certain aspects in glaucomatous disk damage such as higher susceptibility of myopic eyes to glaucomatous damage and a possible explanation for glaucoma nerve head damage in low tension glaucoma.

A quantitative in vitro model for silicone oil emulsification. Role of blood constituents

To understand why some patients seem to be protected from emulsification and others are not, the authors developed an in vitro model for quantitative analysis of silicone oil emulsification. The pro-emulsifying potential of substances and blood components that may have access to the vitreous cavity in a patient's eye was analyzed. In this model, red blood cell ghosts had the highest emulsifying effect; plasma and lymphocytes also had a significant emulsifying effect. Phospholipids in membranes and other soluble blood components may play important roles in this process. These results suggest the importance of avoiding and removing hemorrhage and avoiding inflammation when silicone oil is used in vitreoretinal surgery.

Risk factors associated with late infection of filtering blebs and endophthalmitis

Late infection of filtering blebs and endophthalmitis are hazardous complications of glaucoma filtering surgery frequently associated with bleb failure and loss of functional vision. To determine possible risk factors for the development of these complications, characteristics of nine eyes of nine patients after filtering surgery in whom late endophthalmitis developed were compared with those in patients who had received a comparable operation at the same time in whom endophthalmitis did not develop. An average of 7.7 +/- 6.2 years (range, 6 months to 18 years) elapsed between the time of the filtering procedure and the initial appearance of endophthalmitis. Factors associated with increased risk were: increased axial length, thin and leaky bleb, conjunctivitis, upper respiratory infection, and the winter season.

Preserved action of a rectus muscle after transection by an encircling solid silicone band

We present a case of anterior migration of a solid silicone band through a lateral rectus muscle. In this patient the action of the lateral rectus was preserved, and this is demonstrated photographically. The possible reasons for this rare complication and the possible mechanism by which lateral rectus activity remained intact are explained.

The intravitreal penetration of orally administered ciprofloxacin in humans

To evaluate the penetration of ciprofloxacin, a new wide-spectrum oral antibiotic, into the vitreous, ciprofloxacin was administered orally to 21 patients who were scheduled to undergo vitreal surgery. Seven patients received 750 mg ciprofloxacin 4 hr before surgery (group I), seven patients received this dose 8 hr before surgery (group II), and seven patients received two 750-mg doses of oral ciprofloxacin every 12 hr. The last dose was administered 12 hr before surgery (group III). Vitreous and blood samples were collected simultaneously and assayed for ciprofloxacin concentrations by bioassay and high-performance liquid chromatography.

Identification, prevention, and treatment of silicone oil pupillary block after an inferior iridectomy

We treated two patients in whom silicone oil pupillary block developed despite a patent inferior iridectomy. The clinical characteristics of this complication were a deep anterior chamber, specular reflexes from the iris surface, identification by biomicroscopy of aqueous trapped inferiorly in the vitreous cavity, and no convection currents in the anterior chamber. This complication may be prevented by early face-down positioning of the patient after the operation, and the avoidance of large, centrally located, inferior iridectomies. We recommend that the iridectomy be placed peripherally no larger than 2 mm and propose a new technique for breaking the silicone oil block, which was clearly successful in one of the patients.

Subthreshold argon-laser irradiation elicits a pronounced vitreal prostaglandin E2 response

Chorioretinal production of prostaglandin type E2 (PGE2) as well as changes in vitreal protein and PGE2 concentrations were studied following retinal irradiation with low-power laser energy that caused ophthalmoscopically invisible ("subthreshold") laser burns. This was compared with changes following ophthalmoscopically visible ("suprathreshold") laser burns. Our results demonstrate that with in eyes exposed to the lower-power levels, the enhancement in vitreal PGE2 concentration persisted for a longer period and was more pronounced than in eyes exposed to the suprathreshold levels (a 3-fold and a 2-fold increase above baseline values, respectively). Protein leakage into the vitreous was noted only in the suprathreshold group, indicating a blood-retinal barrier (BRB) disruption. The findings of persistent, excessive PGE2 vitreal levels with no protein leakage in the subthreshold group suggest a possible anti-inflammatory role for PGE2 following low-power laser exposure.

The corneal disk: a new keratoscopic device

An inexpensive instrument for rapid intraoperative or postoperative evaluation of corneal astigmatism is presented. Its ease of use and availability make it an ideal adjunct to cataract and corneal surgical procedures in which minimal postoperative astigmatism is desired.

Argon laser irradiation of rabbits' eyes-changes in prostaglandin E2 levels

Laser irradiation of the eye is a widely used therapeutic measure in various ocular disorders. We investigated in laser-treated rabbits' eyes the changes in prostaglandin E2 (PGE2) levels of the tissue affected by the laser (the retina/choroid) and of its adjacent vitreous over a two-week period. The parameters studied were; PGE2 in vitro production by the retina/choroid, as well as PGE2 and protein levels in the vitreous, the latter indicative of a break in the blood retinal barrier (BRB). The effect of noncoherent light exposure used for illumination, and that of the mechanical manipulation involved (sham exposure) were also studied. Following laser exposure vitreal PGE2 levels were increased two-fold above baseline (days three and 14), whereas light exposure resulted in a single peak. PGE2 in vitro production by the retina/choroid in the laser-exposed group was elevated throughout the observation period, peaking twice (days 3 and 14), in the light-exposed group the enhanced production was evident during a shorter period, whereas in the sham group it remained unchanged from baseline. An elevation in vitreal protein levels to above baseline levels occurred in both the laser- and, to a lesser degree, in the noncoherent light-exposed groups, but not in the sham group. Our study demonstrated an enhanced PGE2 in vitro production by retina/choroid of laser-exposed eyes, which might be attributable to the additive effect of the laser induced trauma, and the noncoherent light photochemical changes; the clinical significance of the recurrent increase in vitreal PGE2 levels in laser-treated eyes might be related to its anti-inflammatory properties.

Intravitreal suture: a complication of pterygium surgery

Among the complications associated with pterygium surgery, scleral perforation is mentioned in cases where subconjunctival tissue must be separated from the sclera. We present a case in which such a perforation and consequent suturing resulted in an intravitreous migration of a suture. We believe this is the first report of such a complication following pterygium surgery.

Long-term study of the prevalence of capsular opacification following extracapsular cataract extraction

The prevalence of capsular opacification was studied in a group of patients who had extracapsular cataract extraction from 1978 to 1980 by one surgeon. In 94 eyes the follow-up was longer than four years. Capsular opacification developed in 41% of these eyes. In 72% of the eyes with opacification the diagnosis was made more than two years after surgery. In the patients who were operated on during 1980, capsular opacification appeared later and less frequently than in those operated on during 1978. Although the difference was not statistically significant, it probably reflects improved technique and more meticulous cleaning of residual cortex. Patients younger than 40 years had a higher prevalence of capsular opacification (70%) than those older than 40 years (37%). Pseudophakic and aphakic patients had a similar prevalence--47.6% and 39.7%, respectively.

Prophylactic scleral buckling in perforating ocular injuries involving the posterior segment

Twenty patients suffering from perforating injury involving the posterior segment of the eye without retinal tear or detachment underwent posterior vitrectomy. In 12 of these where traction of the retina was suspected, prophylactic scleral buckling was performed as well. Only two of these patients developed delayed retinal detachment. Six of the eight patients who did not undergo scleral buckling at the time of the vitrectomy developed this complication. This finding was statistically significant (P = .015) and supports the use of prophylactic scleral buckling in the treatment of eyes with perforating injuries involving the posterior segment to prevent delayed retinal detachment.

Postoperative corneal astigmatism in cataract extraction: diamond knife versus Beaver blade

Postoperative corneal astigmatism was studied in two groups of patients who had cataract extraction. The technique in both groups was identical except for the knife used for the partial-thickness limbal incision. In 49 patients the incision was performed with a Beaver blade and in 35 patients, with a diamond knife. Six weeks postoperatively the astigmatism was 1.27 +/- 0.90 diopters (D) in the diamond knife group, and 2.85 +/- 1.78 D in the Beaver blade group (P less than 0.0001). Sixty-one percent of the Beaver blade cases had with-the-rule astigmatism and 8% had no astigmatism. Thirty-one percent of the diamond knife cases had with-the-rule astigmatism and 26% had no astigmatism. At six months, the astigmatism was equal in both groups and practically identical to that found six weeks postoperatively in the diamond knife group. We conclude that incision of the limbal tissue with a diamond knife is associated with lower postoperative astigmatism and a more stable refractive state than incision with a Beaver blade.

Severe combat eye injuries in the Lebanon War, 1982

The findings, treatment and follow-up of 21 severe, blunt and perforating ocular injuries that occurred during combat in the Lebanon War, 1982, are presented. The diagnostic and therapeutic approaches to complex and severe ocular injuries are discussed. The patients were followed up for 1 year and the long-term effects of the injuries on their eyesight are described.

Macular pucker following accidental laser burn

A case of an accidental exposure to a high intensity Q-switched infrared laser beam is described. A paramacular burn, splinter hemorrhages on the disc margin, and vitreous hemorrhage were the initial findings. Later, a paramacular pucker developed, causing reduction in visual acuity to 6/12. Microvascular accident on the disc margin is assumed to be the cause of a paracentral scotoma located fairly far from the image area.

Identifying patients at risk for thromboembolism. Use of 125I-labeled fibrinogen in patients with acute myocardial infarction

Fibrinogen labeled with iodine 125 was used to detect deep vein thrombosis (DVT) in 35 patients during their course and convalescence from acute myocardial infarction. Clinical status was assessed and scored with the use of a modified coronary prognostic index. According to the prognostic scores, patients were allocated to one of two groups. Of 27 patients in good clinical condition, DVT developed in only one patient, whereas thromboembolic complications occurred in seven of eight patients who were severely ill--a highly significant difference. Prophylactic anticoagulation is advisable in patients at risk.