Current Issue

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Volk 78D Lens Giveaway

There’s nothing better than flexibility! The Volk 78D slit lamp lens is an extremely popular and versatile lens that is a favorite among residents and attendings alike. Traditional slit lamp lenses range from 60D to 90D, and for those new to slit lamp lens, the bigger the number the lower the magnification. The 78D lens is in the middle when it comes to magnification (0.93x), and therefore it is extremely flexible and functional for many different uses. With its wider frame (compared to a 90), you can get a pretty good field view, especially as a beginner. The increased magnification also allows users to see better detail, both in the posterior pole and towards the periphery. One of the key knocks on the 78D is that it is not the optimal lens for the undilated eye; however, it still can function in those cases for a more advanced user. All in all, the 78D lens is extremely versatile, and a necessary option to add your lens collection. Make sure to check out Volk’s website for more information on their slit lamp (and other) lenses!

All subscribers to The Lens have a chance to win their own Volk 78D Lens! Retweet to double your chance to win!

In this week’s issue:

• Promising proof-of-concept for Deep Neural Network to aid in cataract surgery
• Patient features can predict early and late complications from acute symptomatic PVDs
• The LION trial found no significant difference in anterior chamber flare from IOL repositioning and IOL exchange
• Molecular pathway behind ocular neuropathic pain was elaborated in a rat model of dry eye disease

JAMA Ophthalmology

Deep Neural Network Platform for Intraoperative Guidance

Virtual reality is moving one step closer toward reality. Artificial intelligence has slowly been percolating into the realm of surgery. In ophthalmologic surgery, the potential of machine learning has been demonstrated in the postoperative setting with broad applications such as defining surgical landmarks, detecting instruments, and analyzing resident technique. To explore the intraoperative utility of this technology, researchers at the University of Chicago designed a system to track the pupil, detect the current stage of cataract surgery, and provide guidance with visual and auditory feedback. Examples of feedback included capsulorhexis templates, fluidic turbulence indications, and pupil decentration alerts. Six surgical videos were used to train the machine learning algorithm, the performance of which was then validated against 101 cataract procedures from a publicly available dataset. Performance was assessed using area under the receiver operator characteristic (ROC) curve for predicting surgical stage and the Dice score, a method for quantifying the performance of image segmentation, for identifying pupil boundary. Area under the ROC curves were 0.996, 0.972, 0.997, and 0.880 for capsulorhexis, phacoemulsification, cortex removal, and idle phase recognition, respectively, indicating that the algorithm excelled at detecting the current phase of cataract surgery. With a Dice score of 90.23%, the algorithm demonstrated proficiency with pupil boundary detection. Furthermore, 8 of 11 surveyed cataract surgeons who were previously unfamiliar with the platform indicated they were “mostly” or “extremely” likely to use the technology to assist with a complex cataract. Although this platform has yet to be applied in live action, this study demonstrates the potential for augmented reality to enhance ophthalmologic surgery in years to come. 

Ophthalmology

Predicting Complicated PVD in Comprehensive Practice

Flashes? Floaters? In this retrospective cohort study of 8305 patients in a comprehensive eye care practice, investigators assessed the rates and risk factors for complicated posterior vitreous detachments. Notable triage findings associated with increased risk of complicated PVD included male sex, reduced vision, family history of detachments, and prior refractive or cataract surgery. Notable exam findings associated with complicated PVD included vitreous pigment, vitreous hemorrhage, lattice degeneration, and vision worse than 20/40. The authors note that their rate of combined retinal tears and rhegmatogenous retinal detachments in this study (9.7%) is substantially lower than that found in retina subspecialty practices. In addition, they highlight the importance of noting patient-specific risk factors available during triage and examination to predict which patients might be at the highest risk of complicated PVD. 

American Journal of Ophthalmology

The LION Trial: Comparing Inflammation in Repositioning vs. Exchange for IOL Dislocation

Although ophthalmologists have it in the bag, the lens doesn't always stay put in the bag. Late in-the-bag intraocular lens (IOL) dislocation can occur several years after cataract surgery and is related to weakening of the zonular fibers. The two main surgical approaches to late in-the-bag IOL lens dislocation are IOL repositioning and IOL exchange. This study of late in-the-bag IOL dislocation surgery (the LION trial) is a prospective, randomized, parallel-group clinical trial which sought to compare postoperative intraocular inflammation between IOL repositioning and IOL exchange following IOL dislocation. The study included 100 eyes with late in-the-bag IOL dislocation, which were randomly assigned to IOL repositioning or IOL exchange. The main outcome measure was anterior chamber laser flare, measured with a laser flare meter as photon counts per millisecond (pc/ms). There was no significant difference in median anterior chamber flare between reposition group vs. exchange group at two-week follow-up (28.9 vs 31.6, P=0.83). Anterior chamber flare level was utilized because it is more objective than relying on clinical assessment of cell and flare at the slit lamp; however, it remains unclear what level of flare is clinically relevant as a possible threshold for anti-inflammatory treatment or if it is a good marker for postoperative inflammation. Clinicians can consider using the findings from this study when comparing surgical approaches to late in-the-bag IOL dislocation.

Demystifying the cause of ocular neuropathic pain

“Pain without stain” or “phantom cornea” refer to chronic ocular neuropathic pain that greatly impairs a patient's quality of life. While there are many known triggers for ocular neuropathic pain (such as dry eye disease or damage to nerves during refractive surgeries), the pathophysiology and mechanisms underlying the pain remains only partially understood. Transmission of noxious stimuli and nociceptive pain signals require voltage-gated ion channels and a prior study had found that the α2δ–1 subunit of Ca2+ channels mediated spinal hyperexcitability. Researchers hypothesized that upregulation of this subunit might also be responsible for ocular neuropathic pain and performed several analyses using a rat dry eye model with lacrimal gland excision. Neuronal hyperactivation, transient activation of microglia, persistent activation of astrocytes, α2δ–1 subunit upregulation, and reduced numbers of inhibitory interneurons were observed in the trigeminal nucleus while continuous treatment with pregabalin was effective in decreasing hypersensitivity and hyperalgesia. Ophthalmic treatment (hyaluronic acid drops and ophthalmic ointment) alone was ineffective at ameliorating the chronic pain. This suggests that simply repairing the epithelial damage caused by dry eye disease is insufficient for recovery and reduction in pain. These findings may help us better target therapies for ocular neuropathic pain in a mechanism-based manner through increasing our understanding of the complex pathophysiology of this disease. Future studies should expand these findings in other models of ocular neuropathic pain including post-surgical pain. 

Journal of Glaucoma

Vascular Risk Factors for Low Tension Glaucoma

Vascular abnormalities are hypothesized to cause diminished perfusion to the optic nerve in low-tension glaucoma. Investigators explored vasculopathic risk factors for development of low-tension glaucoma in a retrospective case-control study. Low tension glaucoma was associated with several vascular risk factors. Low tension glaucoma patients were found to have lower likelihood of obesity (body mass index >30, P=0.03), and higher incidences of systemic hypertension [odds ratio (OR): 1.64, P=0.004], diabetes mellitus (OR: 3.01, P<0.001), peripheral vascular disease (OR: 2.61, P=0.009), migraine headache (OR: 2.12, P=0.02), anemia (OR: 2.18, P=0.003), systemic hypotension (OR: 4.43, P<0.001), Raynaud syndrome (OR: 3.09, P=0.05), and angiotensin-converting enzyme inhibitor (OR: 1.64, P=0.01) or calcium channel blocker use (OR: 1.98, P=0.004). Further research is needed to determine the role of vascular factors in glaucoma pathogenesis. 

BMC Ophthalmology

Evaluation of Screening Guidelines for Retinopathy of Prematurity in Egypt

Screening guidelines for Retinopathy of Prematurity (ROP) are not well established in Egypt. Current American guidelines recommend screening for infants born at gestational ages <30 weeks or birth weight <1500 g, however this was developed based on American prematurity and growth restriction prevalence. In a two year independent screening effort for ROP in rural Egypt, infants born at <34 weeks of gestational age, birth weight < 2000 g, or with history of unstable NICU course were screened (and if indicated, treated) for ROP. The incidence found in this sample (48.2%) was far greater than rates in other countries (South Africa 29.6%, Iran 23.5%). Limitations included delayed examination (>28 days of life) which may have contributed to better visibility of vascularization and relatively small sample size (276 infants). Other studies have noted differences in incidence of ROP in rural settings as compared to university hospitals and private hospitals in Egypt each with different screening parameters. Collectively, these studies should be used to determine adequate screening guidelines specific to the country of Egypt, and similar reevaluation should be conducted in countries globally to address disease burden specific to each setting.

A 26-year-old woman with a history of hypertension, obesity, and recent weight gain presents with blurry vision, headache, and proptosis. Her symptoms significantly worsened over the last 5 days, and she now requires help navigating her home due to her poor vision. She takes hydrochlorothiazide and lisinopril. Her physical exam is notable for restricted visual fields bilaterally, hand motion visual acuity in the left eye, 20/200 in the right eye, and optic disc edema. A lumbar puncture is performed, and the opening pressure is 39 cm of water. An MRI brain is performed, and the relevant images are included below. Which of the following is the most sensitive imaging finding related to her probable diagnosis?

A. Flattened posterior globe

B. Empty sella turcica

C. Transverse sinus stenosis

D. Lacrimal gland swelling

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