Calculation of tunnel incision parameters during phacoemulsification in patients with previous anterior radial keratotomy

Background. The purpose was the choice of the type of tunnel incision on the basis of mathematical calculations in cataract patients with a previous anterior radial keratotomy. Materials and methods. During the calculations, the formula for the chord length of a circle was used: L = 2R · sin(α/2), where R is the radius of the cornea, α is the angle (in degrees) between the two corneal incisions. The chord length was measured on the limbus (upper edge of the tunnel incision) and 2 mm from the limbus (lower edge of the tunnel incision). The chord 2 mm from the limbus is more important because the distance between keratotomy incisions at this site is smaller. From 0.4 to 1.0 mm must be added to the width of the knife blade, depending on the type of postoperative corneal healing, which will be the key to crossing the incisions. Results. The most common knives are those 2.2 mm long with a tunnel length of 2 mm. Therefore, we perform calculations based on this knife in patients with 8 and 12 keratotomy incisions and a corneal diameter of 12 mm vertically and 11 mm horizontally. In patients with 8 keratotomy incisions, a 2.2 mm knife can be used for a corneal tunnel incision, and in patients with 16 incisions, it is impossible to use a corneal tunnel. Conclusions. In cataract patients who have previously undergone anterior radial keratotomy, a special approach is needed to the choice of tunnel incision. The choice of access depends on the diameter of the cornea, the number of keratotomy incisions and the width of the knife and is calculated using the formula for the chord length of a circle.

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Pneumotonometer Accuracy Using Manometric Measurements after Radial Keratotomy, Clear Corneal Incisions and Lamellar Dissection in Porcine Eyes

Current Eye Research ◽

10.1080/02713683.2019.1652915 ◽

2019 ◽

Vol 45 (1) ◽

pp. 1-6

Author(s):

Lauren A. Maloley ◽

M. Reza Razeghinejad ◽

Shane J. Havens ◽

Vikas Gulati ◽

Shan Fan ◽

...

Keyword(s):

Radial Keratotomy ◽

Porcine Eyes ◽

Corneal Incisions

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Paired opposite clear corneal incisions to correct preexisting astigmatism in cataract patients

Journal of Cataract & Refractive Surgery ◽

10.1016/j.jcrs.2004.11.053 ◽

2005 ◽

Vol 31 (6) ◽

pp. 1167-1170 ◽

Cited By ~ 31

Author(s):

Abid Qammar ◽

Paul Mullaney

Keyword(s):

Cataract Patients ◽

Corneal Incisions

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The effect of tunnel length and position on postoperative corneal astigmatism: An optical coherence tomographic study

European Journal of Ophthalmology ◽

10.1177/1120672118805875 ◽

2018 ◽

Vol 30 (1) ◽

pp. 104-111

Author(s):

Serap Sonmez ◽

Cagatay Karaca

Keyword(s):

The Other ◽

Corneal Astigmatism ◽

Tunnel Length ◽

Corneal Incision ◽

Surgically Induced Astigmatism ◽

Clear Corneal Incision ◽

Induced Astigmatism ◽

Short Tunnel ◽

Surgically Induced ◽

Corneal Incisions

Purpose: The purpose of this study is to evaluate the effects of variation in tunnel length of same-sized clear corneal phacoemulsification incisions on the generation of surgically induced astigmatism and corneal astigmatism. Methods: A total of 126 cataract patients treated in four study groups based on location and tunnel length of the clear corneal incisions (superior long, superior short, temporal long, temporal short) were reviewed. In the short tunnel groups, a 2.8 mm keratome was used with a motion parallel to the iris surface, while in the long tunnel groups, the same keratome was advanced in the corneal stroma until the mark on the keratome was reached. The surgically induced astigmatism and the corneal astigmatism were measured with corneal topography. The tunnel lengths were determined by anterior segment optical coherence tomography. Results: The tunnel lengths of the long tunnel groups were significantly longer than the short tunnel groups. The total and anterior corneal surgically induced astigmatism of the superior long group was significantly higher than the other groups. Posterior corneal surgically induced astigmatism was similar. The postoperative total and anterior corneal astigmatism values of the superior long group was significantly higher than the other groups. No difference was observed for mean change in corneal astigmatism between the groups. Conclusion: The tunnel length of a clear corneal incision is a significant determinant of surgically induced astigmatism for superior placed corneal incisions. Therefore, for superiorly positioned clear corneal incision, the incision should be rectangular with a shorter tunnel to keep the surgically induced astigmatism to a minimum. For squarer-shaped clear corneal incision, limbal-temporal incisions may be performed for astigmatic neutrality.

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Ortho-k lenses fitting in patients with “non-typical” corneas

The Eye ◽

10.33791/2222-4408-2020-1-22-29 ◽

2020 ◽

Vol 22 (129) ◽

pp. 22-29

Author(s):

Svetlana Kravchuk ◽

Olga Zhabina

Keyword(s):

Correction Method ◽

Diameter Ratio ◽

Corneal Curvature ◽

Individual Approach ◽

Fitting In ◽

Corneal Diameter ◽

Clinical Cases

We described two clinical cases of ortho-k lenses fitting in patients with “non-typical” corneal curvature/diameter ratio. The main goal was to acknowledge effective and safe use of this myopia correction method in patients with corneal diameter greater than 11 mm. Individual approach to each patient is the key to a successful and safe ortho-k lenses fitting.

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Profil Pasien Katarak Senilis Pada Usia 40 Tahun Keatas di RSI Siti Rahmah Tahun 2017

Health & Medical Journal ◽

10.33854/heme.v1i1.214 ◽

2019 ◽

Vol 1 (1) ◽

pp. 15-21

Author(s):

Rada Puspita ◽

Haves Ashan ◽

Fidiariani Sjaaf

Keyword(s):

High School ◽

Secondary Data ◽

Study Data ◽

Vision Impairment ◽

High School Education ◽

Frequency Data ◽

Private Companies ◽

The World ◽

Age Range ◽

Cataract Patients

Vision impairment is estimated to affect 285 million people in the world, where 16-20% experience blindness, from the number of blindness suffered at the age of 40-50 years. Cataract seninis is all lens opacities that are found in old age that is above 40 years. The purpose of identifying and collecting frequency data Profile of Senilis cataract patients at the age of 40 years and above at RSI Siti Rahmah Padang in 2017. The research method is descriptive type of research, this study data taken is secondary data, In this study data was taken from the Medical Record at RSI Siti Rahmah Padang. When the study was conducted in February-August 2018, the population of this study were all cataract patients at the age of 40 years and above at RSI Siti Rahmah Padang in 2017 with 80 samples. Data analysis is univariate presented in the form of a frequency distribution table. Results From 80 respondents as many as 40 people (50%) were in the age range of 60-69 years, as many as 42 people (52.5%) patients were male, as many as 31 people (38.8%) patients with high school education and 35 people (43.8%) patients work as private companies. Conclusion In general, most patients are at the age of 60-69 years, the most sex is men, the highest education is high school and most patients are private.

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