Robert Latkany

Intraocular lens calculations after refractive surgery

Purpose: To evaluate the effect of refractive surgery on intraocular lens (IOL) power calculation, compare methods of IOL power calculation after refractive surgery, evaluate the effect of pre‐refractive surgery refractive error on IOL deviation, review the literature on determining IOL power after refractive surgery, and introduce a formula for IOL calculation for use after refractive surgery for myopia. Setting: Laser & Corneal Surgery Associates and Center for Ocular Tear Film Disorders, New York, New York, USA. Methods: This retrospective noncomparative case series comprised 21 patients who had uneventful cataract extraction and IOL implantation after previous uneventful myopic refractive surgery. Six methods of IOL calculation were used: clinical history (IOLHisK), clinical history at the spectacle plane (IOLHisKs), vertex (IOLvertex), back‐calculated (IOLBC), calculation based on average keratometry (IOLavgK), and calculation based on flattest keratometry (IOLflatK). Each method result was compared to an “exact” IOL (IOLexact) that would have resulted in emmetropia and then compared to the pre‐refractive surgery manifest refraction using linear regression. The paired t test was used to determine statistical significance. Results: The IOLHisKs was the most accurate method for IOL calculations, with a mean deviation from emmetropia of −0.56 diopter ±1.59 (D), followed by the IOLBC (+1.06 ± 1.51 D), IOLvertex (+1.51 ± 1.95 D), IOLflatK (−1.72 ± 2.19 D), IOLHisK (−1.76 ± 1.76 D), and IOLavgK (−2.32 ± 2.36 D). There was no statistical difference between IOLHisKs and IOLexact in myopic eyes. The power of IOLflatK would be inaccurate by −(0.47x + 0.85), where x is the pre‐refractive surgery myopic SE (SEQm). Thus, without adjusting IOLflatK, most patients would be left hyperopic. However, when IOLflatK is adjusted with this formula, it would not be statistically different from IOLexact. Conclusions: For IOL power selection in previously myopic patients, a predictive formula to calculate IOL power based only on the pre‐refractive surgery SEQm and current flattest keratometry readings was not statistically different from IOLexact. The IOLHisKs, which was also not statistically different from IOLexact, requires pre‐refractive surgery keratometry readings that are often not available to the cataract surgeon.

Comparative evaluation of refractive surgery candidates with Placido topography, Orbscan II, Pentacam, and wavefront analysis

PURPOSE: To study the role of the Pentacam (Oculus), Orbscan II (Bausch & Lomb), and WaveScan (Visx) in evaluating topographic features identified as risk factors for ectasia after laser in situ keratomileusis to identify parameters that may be important in interpreting elevation topography and wavefront data when screening refractive surgery candidates. SETTING: Private practice, New York, New York, USA. METHODS: One hundred forty‐five eyes of 75 consecutive patients were evaluated for refractive surgery by ultrasound pachymetry (Humphrey Atlas), videokeratography, WaveScan, Orbscan II, and Pentacam. Eyes were classified as normal or suspect based on the Rabinowitz criteria for keratoconus suspect on Placido disk‐based videokeratography. Forty‐six parameters were evaluated in a comparison of topographically normal eyes and eyes that met the criteria for keratoconus suspect. RESULTS: The suspect group had thinner pachymetry, multiple distinguishing characteristics on the anterior and posterior corneal surfaces by elevation topography, and larger amounts of coma by wavefront analysis. Multivariable regression analysis identified the following as the strongest predictors of a suspect Placido topography: Pentacam, thinner pachymetry and larger differences between the highest and lowest points on the posterior elevation; Orbscan II, higher anterior maximum elevation, horizontal location of the thinnest point on the pachymetry map, and larger differences between the highest and lowest points on the posterior elevation. CONCLUSION: Several parameters provided by the Pentacam, Orbscan II, WaveScan, and pachymetry were statistically correlated with keratoconus suspect, defined by higher asymmetry and steeper curvature on Placido topography.

Current and Emerging Therapeutic Strategies for the Treatment of Meibomian Gland Dysfunction (MGD).

Meibomian gland (MG) dysfunction (MGD) is a multifactorial, chronic condition of the eyelids, leading to eye irritation, inflammation and ocular surface disease. Initial conservative therapy often includes a combination of warm compresses in addition to baby shampoo or eyelid wipes. The practice of lid hygiene dates back to the 1950s, when selenium sulfide-based shampoo was first used to treat seborrhoeic dermatitis of the eyelids. Today, tear-free baby shampoo has replaced dandruff shampoo for MGD treatment and offers symptom relief in selected patients. However, many will not achieve significant improvement on this therapy alone; some may even develop an allergy to the added dyes and fragrances in these products. Other manual and mechanical techniques to treat MGD include MG expression and massage, MG probing and LipiFlow®. While potentially effective in patients with moderate MGD, these procedures are more invasive and may be cost prohibitive. Pharmacological treatments are another course of action. Supplements rich in omega-3 fatty acids have been shown to improve both MGD and dry eye symptoms. Tea tree oil, specifically the terpenin-4-ol component, is especially effective in treating MGD associated with Demodex mites. Topical antibiotics, such as azithromycin, or systemic antibiotics, such as doxycycline or azithromycin, can improve MGD symptoms both by altering the ocular flora and through anti-inflammatory mechanisms. Addressing and treating concurrent ocular allergy is integral to symptom management. Topical N-acetylcysteine and topical cyclosporine can both be effective therapeutic adjuncts in patients with concurrent dry eye. A short course of topical steroid may be used in some severe cases, with monitoring for steroid-induced glaucoma and cataracts. While the standard method to treat MGD is simply warm compresses and baby shampoo, a more tailored approach to address the multiple aetiologies of the disease is suggested.

Nocturnal Lagophthalmos: An Overview and Classification

Nocturnal lagophthalmos is the inability to close the eyelids during sleep. Lagophthalmos is associated with exposure keratopathy, poor sleep, and persistent exposure-related symptoms. There are a variety of causes of lagophthalmos, grouped as proptosis/eye exposure etiologies and palpebral insufficiency etiologies. Although obvious lagophthalmos is usually detected, it is sometimes difficult to recognize obscure lagophthalmos, due either to eyelash obstruction or overhang of the upper lid anterior and inferior to the most superior portion of the lower lid in a closed position. We present a novel classification system and illustrations of obvious and obscure lagophthalmos. A diagnosis can usually be made with a focused history and slit lamp examination. Treatment is multipronged and may include minor procedures or ocular surgery to correct the lid malposition; natural, topical or oral agents; and punctal plugs to manage ocular surface effects. Correct and timely diagnosis allows greater opportunity for relief of patient suffering and prevention of severe ocular surface pathology, as well as educated planning for future ocular surgical procedures.

Effect of punctal plugs in patients with low refractive errors considering refractive surgery.

PURPOSE To study the effect of punctal plug placement in patients undergoing refractive surgery for correction of poor vision. METHODS A retrospective study was performed of 12 patients (21 eyes) who presented for initial refractive surgery or retreatment after LASIK or photorefractive keratectomy to improve visual acuity. Uncorrected visual acuity (UCVA) was documented in each eye. If tear normalization test was positive (indicating dry eye), silicone punctal plugs were placed in the lower lids of both eyes. Subjective patient UCVA and Snellen UCVA were assessed at 1 month. RESULTS At 1 month, two eyes improved by three Snellen lines, nine eyes improved by two lines, seven eyes improved by one line, and three eyes remained unchanged. Uncorrected visual acuity was considered statistically significant (P < .0001) using the paired t test. No eye demonstrated decrease in visual acuity. One patient experienced punctal plug extrusion in both eyes. No other adverse outcomes were reported. One patient pursued additional refractive surgery after plug placement. No patient requested plug removal. CONCLUSIONS Patients with low refractive errors note improvement in visual acuity after punctal plug placement.

Tear film normalization test: a new diagnostic test for dry eyes.

Purpose: To evaluate the normalization of the tear film (tear film normalization test [TNT]) as a diagnostic test for dry eye syndrome. Methods: The uncorrected distance vision of 20 patients with dry eyes (40 eyes) and 20 normals (40 eyes) before and after instillation of carboxymethyl cellulose 0.5% (CMC; Refresh Plus; Allergan, Irvine, CA) was recorded. We used study early treatment diabetic retinopathy (ETDRS) vision charts to test vision in each eye. Tear film breakup time (TBUT), presence or absence of superficial punctate erosions (SPE), tear film meniscus height, meibomian gland function, and ocular surface disease index (OSDI) questionnaire scores were evaluated. Results: CMC improved visual acuity in the dry eye group (P < 0.0001). Response operators curve (ROC) analysis showed that vision improvement of 2 lines or more after tear normalization was associated with an 82.5% (95% CI: 66.6%-92.1%) sensitivity and 100% (95% CI: 89.1%-100%) specificity for dry eye. There was a significant correlation between vision improvement and OSDI score in the dry eye group (P = 0.003). Conclusion: The TNT is a highly sensitive and specific test for dry eyes and is available in every eye care professionals office. The more symptomatic the dry eye, the greater the improvement.

Retention rate of silicone punctal plugs placed by residents in a general clinic setting.

Purpose: To evaluate the retention rate of silicone punctal plugs placed in patients with dry eye in a general clinic setting by ophthalmology residents. Methods: A cohort study reviewing charts of 88 patients who underwent punctal plug placement in the resident clinic at The New York Eye and Ear Infirmary from January 2007 to November 2008. Information recorded included age and sex of the patients, date of insertion, initial versus replacement plug, type and size of plug, location of insertion, and retention versus spontaneous extrusion versus removal of plugs at follow-up visits. Follow-up data were recorded at 30 and 60 days. Results: Follow-up data for 106 plug placements were available at 30 days. A total of 71.7% were retained, 23.6% were lost, and 4.7% were removed. At 60 days, data were available for 96 plug placements. A total of 50.0% were retained, 47.9% were lost, 5.2% had been removed prior to 60 days, and 2.1% had been replaced prior to 60 days. Conclusion: Spontaneous extrusion is a common complication in punctal plug insertion, and the retention rate in a general clinic setting with ophthalmology residents is low. This may suggest that attention should be placed on improved instruction in placement techniques and sizing, better patient education on avoidance of rubbing, and importance of follow-up. It may also support the need for better designed plugs or considering alternatives to the silicone plugs, or the placement of such plugs in a dedicated punctal plug clinic under supervision of an experienced attending physician.